J. LAURENS BARN A Benthic Ecology of

Bahia de San Quintin

Baja California

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1970 NUMBER 44
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ABSTRACT

Barnard, J. Laurens. Benthic Ecology of Bahia de San Quintin, Baja California.

Smithsonian Contributions to Zoology, 44:1-60, 1970.—Three important biotic

assemblages and several minor associations occur on the soft bottoms of San Quintin

Bay. The most obvious assemblage is characterized by the eelgrass, Zostera marina,

that covers approximately 20 percent of the study area. A second densely populated

assemblage occurs in tidal channels and on their margins and is dominated by a

globular ascidian, Eugyra glutinans, and a tube-forming amphipod, Ampelisca compressa. That community merges with a poorly populated Prionospio (polychaete)

community occupying sand flats in shallow, quiet water; the two are asymmetrically

connected by a facies (or ecotone) characterized especially by two genera of amphipods, Acuminodeutopus and Rudilemboides. A less widespread fourth assemblage,

dominated by a polychaete genus Fabricia, occurs primarily adjacent to marshes,

especially in the inner reaches of the lagoon. Three phases of the Prionospio community

occur, the typical phase and phases dominated by the polychaetes Scoloplos acmeceps

and Cossura Candida. The Ampelisca-Eugyra community also exists in extreme

phases dominated by either of the principal members.

The Prionospio community is interpreted as a base community representing

a penetration from the open sea of an analogous community in shallow waters on

which is imposed the Zostera community where suitable banks are elevated above

the surrounding fiats. The Zostera community has few elements in common with

the Phyllospadix (surfgrass) community of the open sea. The Eugyra-Ampelisca community occurs mainly in channels and at the feet of banks where water motion is

highest in the bay. The Eugyra-Ampelisca community is unique to the literature but

has affinities with open-sea Tellina communities.

San Quintin has few of the cosmopolitan taxa usually introduced into bays by

humans. The warm-temperate lagoons of California and Baja California have few

common denominators probably because of changes imposed by man. Very few

species in San Quintin are obligatory inhabitants of lagoons.

San Quintin is unusual in being controlled physiographically by cinder cones;

the west arm is a typical lagoon, whereas the east arm has characteristics of a drowned

river valley.

A hypothetical system of lagoonal maturation and senescence is proposed in

which the depositional influences are accelerated by soft-bodied benthic biota.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

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Contents

Page

Abstract ii

Introduction 1

Field Methods 1

Analytical Methods, Hypotheses, and Terms 1

The Communities 5

The Problem of Subcommunities 7

Description of the Communities 8

The Zostera-Ericthonius-Capitita Community 8

The Eugyra-Ampelisca Community 8

The Prionospio Community 9

The Cossura Phase of the Prionospio Community 10

The Scoloplos Phase of the Prionospio Community 10

The Fabricia Community 11

The Kalliapseudes Samples 11

The Exogone-Acuminodeutopus-Rudilemboides Ecotones 13

Relationship of Communities to Sediments 13

Relationship of the Lagoonal Community to the Open Sea 13

Interrelationships of Warm-Temperate Lagoons 18

Comparability of the Eelgrass Community to the Phyllospadix Community of the Open-Sea

Intertidal 18

The Calm-Water Element 19

Open-Sea Distribution of Major Lagoonal Taxa 20

Relationship of the Benthic Lagoonal Community to Pollution Faunas 21

The Environment 23

Physiography and Sediments 23

Interrelationships of Sediments and Biota 24

Climate of Air and Water 26

Avian Predators 26

Conclusions 26

Acknowledgments 28

Literature Cited 28

Appendix I, Contagious Species 30

Appendix II, List of Miscellaneous Species 33

Appendix III, Nomenclatural List 35

Appendix IV, Data Decks and Methods 36

Index 57

i ll

J. Laurens Barnard Benthic Ecology of

Bahia de San Quintin

Baja California

Introduction

The environment and benthic macrofaunal assemblages of Bahia de San Quintin are discussed as a

conclusion to a survey conducted in 1960-62. Previous

papers include an Introduction by Barnard (1962),

Benthic Flora (Dawson, 1962), Physiography and Sediments (Gorsline and Stewart, 1962), Isopoda (Menzies, 1962), Polychaeta (Reish, 1963), Mollusca

(Keen, 1962), and Amphipoda (Barnard, 1964).

Manuscripts concerning hydrography by Grady, and

microbiota by Resig are in preparation.

This study is confined to the eastern, landward arm

of San Quintin Bay that has been considered physiographically by Gorsline and Stewart (1962) to

represent a drowned estuary. The bay now has the

characteristics of a lagoon because of the arid climate.

Maps printed herein include only the eastern arm of

the bay except Figure 13.

Because the biotope has already been considered by

Gorsline and Stewart, the presentation herein proceeds from an identification of the benthic biota to

a discussion of the biotope so that facts uncovered in

the biological analysis can be discussed in relation to

the physical setting. The analytical procedures are

described in detail (Appendix IV) as an exercise in

simple methodology in hopes of stimulating further

exploration of undersea bottom life in American

waters. Such exploration has been neglected on level,

sedimentary bottoms in the Western Hemisphere, in

part because of a paucity of finances available for the

large teams of researchers necessary to explore and

analyze undersea biotopes and partially because of

/. Laurens Barnard, Department of Invertebrate Zoology,

Smithsonian Institution, Washington, D.C. 20560.

the scarcity of expert taxonomists to identify biota.

Surveys are likely to continue by utilizing simple tools

and methods in the foreseeable future. The crucial

focus in these early times is the necessity to describe

communities in as consistent framework as possible

to conform with the basic literature developed from

European studies (Thorson, 1957).

Field Methods

Water characteristics were studied in 1960 and 1961

in both arms of the bay during 5 seasonal surveys

(Figure 15), whereas the bottom biota and sediments

were sampled only once, in April 1960. The biotic

samples were collected on an even-area grid of 90

stations in the east arm of the bay at a density of about

15 per nautical square mile utilizing an orange peel

grab of 0.06 square meter coverage. Samples of sediment were also collected with this device. Gorsline and

Stewart (1962) studied San Quintin sediments in

terms of mean diameters of particles, but I have recalculated them as median diameters for use herein so

as to correspond with procedure generally found in

the literature.

The biological samples were filtered through Tyler

screens of 0.7 mm mesh, sorted and identified by

various specialists. The Polychaeta, Amphipoda, Isopoda, and Mollusca deserved separate reports (see list

above and Appendix III). The remaining identifications are tabulated in Appendix II.

Analytical Methods, Hypotheses, and Terms

A benthic sampling survey provides a means of describing taxonomic components of the fauna and their

1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

distribution and abundance in relation to their biotopes. A survey also presents the possibility of determining the cooccurrence of two or more species so that

biotic associations can be discussed. Whether the terms

community, association, biofacies, or assemblage deserve any categorical rank is a subject not considered

in this paper because I cannot contribute anything to

the problem of whether the whole ocean contains only

one community or many and whether a marine community must necessarily have a visible photosynthetic

base. The terms community, association, and biofacies

are utilized interchangeably herein, but the term

assemblage is used arbitrarily to identify a possible community in the early stages of its elaboration by statistical methods. The methods utilized in the discussion do

not automatically define the taxal structure of a community nor do they circumscribe the limits of a community. These definitions are matters of judgment

based on the degree of relationships among samples,

the extent to which groups of samples have discontinuities among themselves, a knowledge of the

environment represented by groups of samples, a knowledge of the environment adjacent to the area under

study, and an appreciation of the precedents already

described in the world literature of marine communities (Thorson, 1957). Other important considerations

are the size of the area and the density of individuals

represented by groups of samples. These characters

have relevance to the matter of defining a group of

samples as representative of a community or an ecotone. An ecotone is a region, usually of small extent,

between two communities of large extent. In the ecotone, the principal taxa of the adjacent communities

may be strongly mixed or there may occur an impoverishment of taxa and individuals of adjoining communities. If communities can be defined, or at least named,

for their principal members, these members being the

most frequently occurring taxa of reasonably large body

size in the samples under consideration, then one finds

that the community may occur in phases definable by

the occurrence of secondary dominants. This may be

visualized more easily by codes; two communities may

be identified by their principal taxa, A and X; community A may be relatively homogeneous but community X may have other secondary species (Y and Z)

nearly as abundant as X; but Y and Z may be mutually

exclusive and form phases of the community; X remains the common denominator, however, and is the

main member of the community. In another case community MN may have two principal species that occur

together frequently but have phases in which M and

N are mutually exclusive. Another community, F, may

have two phases, one with F alone as dominant and

one with F and G together. In this case and in the

Y-Z case, it may be difficult to determine whether the

Y, Z, and G phases are really ecotones unless these

phases can be shown to occur on boundaries of the

area of distribution of communities X and F.

Two precepts of community analysis have been abandoned in this study. The importance of standing crop

as a criterion of selection for the major species in a

community is considered negligible and the method unworkable. The Peterson rule of grouping samples (or

bottom area) if half or more of contiguous samples (or

area) have the dominant species present is abandoned

in favor of a 100 percent rule. This divides the sample

groups more finely. Samples are therefore grouped

according to the presence of the most abundant individuals of a taxon, but taxa with high standing crops

and low numbers of individuals are not ignored entirely (Table 1). The term "dominant" is accorded

to a species with highest frequencies of individuals in

a sample. "Subdominant" species represent taxa with

secondarily high frequencies of individuals.

A synecological survey of the kind discussed in this

paper requires taxonomic analysis of biota found in the

samples (90). The data incorporate the names (or

codes) and total numbers of specimens of each taxon

in each sample and the data are arranged in five decks

(Appendix IV). Initial inspection of the data of decks

1 and 2 shows that many samples can be grouped

according to the presence of a few species with high

numbers of individuals per sample, but most of the

species have low numbers of specimens in many samples

and high numbers of specimens in a few samples. By

arranging the data as in deck 3 (Appendix IV), the

chronology of sample numbers is lost, but each species

is thereby provided with a list of samples ranked according to the number of specimens in each sample.

A working basis for community analysis is possible

on the theory that the most widely distributed species

or those with highest frequencies in a few samples may

represent the main species of several communities. The

next step is to determine whether the main species

are more or less mutually exclusive in occurrence (Appendix IV, Method 1 and alternatives A-l-2, and B1-2). Those species with highest numbers of individuals or most widely distributed (Table 1) or a few of
NUMBER 44 3

TABLE 1.—Dominant species of Bahia de San Quintin (abundant or large-bodied species utilized for community analyses)

Median Midpoint "ContaName of species sample specimens positive positive between gious fireoccurrence average quency"*

and median

Positive

sample

(n=90)

Total

specimens

Average

positive

occurrence

POLYCHAETA

Axiothella rubrocincta

Brania clavata

Capitita ambiseta

Chone rnollis

Cirriformia luxuriosa

Cossura Candida

Exogone verugera

Fabricia limnicola f

Lumbrineris minima

Megalomma pigmenium

Neanthes caudata

Onuphis microcephala

Pista alata

Platynereis bicanaliculata

Prionospio malmgreni

Scoloplos acmeceps

Scoloplos ohlini

Scyphoproctus oculatus

AMPHIPODA

Acuminodeutopus heteruropus

Ampelisca compressa

Amphideutopus oculatus

Corophium baconi

Elasmopus rapax

Ericthonius brasiliensis

Hyale frequens

Lembos macromanus

Listriella melanica

Lysianassa holmesi

Microdeutopus schmitti

Orchomene magdalenensis

Paraphoxus obtusidens

Pontogeneia quinsana

Rudilemboides stenopropodus

Uristes entalladurus

MOLLUSCA

Acteocina carinata

Tellina buttoni

ISOPODA

Paranthura elegans

TANAIDACEA

Kalliapseudes crassus

ASCIDIACEA

Eugyra glutinans

29

28

46

41

16

48

68

27

41

40

46

13

34

23

70

64

39

18

53

56

22

24

16

21

22

25

35

16

28

28

43

17

48

19

32

11

14

12

35

141

231

3,840

516

124

3,669

10,865

3,391

351

371

802

341

946

170

5,735

1,433

267

267

2, 185

18, 923

804

260

272

5,892

2,085

828

319

1,457

1,049

641

850

194

3,040

265

267

87

133

10, 393

7,157

5

8

83

13

8

76

160

126

9

9

17

26

28

7

82

22

7

15

41

338

37

11

17

281

95

33

9

91

37

23

19

11

66

14

8

8

9

866

204

3

3

12

6

3

44

19

21

4

5

6

6

10

3

44

10

3

6

15

8

6

8

15

82

50

15

5

3

5

7

9

6

21

2

4

3

3

4

43

4

6

47

10

6

60

89

74

7

7

11

16

19

5

63

16

5

11

28

173

22

10

16

182

73

24

7

47

21

15

14

9

44

8

6

5

6

435

123

9

10

228

14

11

153

105

141

10

16

16

17

54

9

112

35

6

13

48

227

26

14

9

160

32

43

9

81

16

40

29

6

133

5

9

6

35

1,632

143

•Number of specimens in first sample above change in curve, see text.

flncluding sample zero with 1340 individuals not otherwise included in this report.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

the large-bodied species in San Quintin were tested in

pairs among themselves and the results presented in

Figures 1-3 and 5, according to variations of n in the

formula of Method I. In the standard procedure, n is

considered as the total number (90) of samples in the

survey, but the results are diffuse (Figure 3). By restricting the number of samples considered in the comparison between any two species, the results are sharpened strongly (Figure 2). The restriction is based on

the premise that several samples with the highest number of specimens for each of the species have more informational content in the test of association. These

samples are termed as those in which the species is contagious, and they are selected from data deck 3 by instructions in data deck 5 (Appendix IV) or alternatively in part 5 of data deck 4. The selection of samples

that are contagious for each species is controlled by the

hypothesis that the rate of increase of specimens per

sample along a straight line connecting the plots of

specimens on arithmetic graph paper, from lowest to

highest in the sample group, represents an arithmetic

progression except at the high end of the plots where

the line evolves into a curve. At that point a geometric

progression is assumed to commence and this point

defines the minimum value of contagion for a species.

The minimum value of contagion is generally approximate to a number computed from the halfway point

between the mean occurrence of the species per sample and the median (discarding samples in which the

species is absent). These data form a part of data deck

4 (Appendix IV) and form the basis on which samples are selected for Method 1, alternative B-2. All of

the commonly occurring species in San Quintin Bay,

those in 10+ percent of the samples in Table 1, show

statistical aggregation in the Poisson series; this aggregation is a main function of at least some of those

samples embraced by the curve signifying a geometric

progression in the occurrence of a species from sample

to sample. For the sake of analogy one might speak of

those samples arranged in an arithmetic progression

as representative of environments in which the species

occurs in background (endemic) frequencies. The

samples in the geometric progression might be termed

as epidemic or contagious and they may represent environments in which the species occurs in superoptimal

densities. So as to find a level of consistency in the

foci of communities in San Quintin, the descriptions

of the communities have been based largely on samples in which the main species are contagious. The

number of positive samples for each species in San

Quintin that are considered as contagious varies between 7 and 12 percent of the positive samples for

each species.

The method of selecting contagious samples for each

species is probably a workable hypothesis only in a survey in which samples have been taken on a grid system and are thus representative of evenly sized areas

which include biotopes outside the range of the species.

Once the perimeter of a species has been found in a

survey of this kind it would be possible to design a sampling pattern almost wholly within the parts of the

biotope in which the species is most highly aggregated.

Once a matrix of C-values in Method 1 is prepared,

a judgment of the significance of the values is made

by inspection of the data. By trial and error various

levels of significance are selected so as to group several

species in polygons like those of Figures 1-3. When

lower levels of significant C-values are selected more

species are joined to the foci. Because of field observations in ,San Quintin Bay, the significant C-values

could be easily selected so as to include in a group those

species already known to be restricted to the Zostera

community. This level of significance (Figure 1) resulted also in joining together species known to be typical of the Ampelisca-Eugyra assemblage, and it revealed a third assemblage not otherwise observed in

the field.

Samples in data deck 1 are rearranged on the basis

of Figure 1 to extract any containing the main species

in the three assemblages and then further divided into

assemblages including only those samples containing

the main species in contagious levels. Because only a

fraction of the samples in data deck 1 is ordered into

assemblages by Method 1 the remaining samples (residuals) are treated by Method 2. The disadvantage

of Method 1 is the failure to pinpoint assemblages unless three or more species are involved as the main

dominants.

The further determination of assemblages based on

Method 2 accounted for only 72 percent of all the

samples because decisions as to possible assignment of

samples to primary foci could not be made with any

consistency.

The next stage of analysis is an attempt to determine if the samples represent a closely knit continuum

of taxal occurrences. The method of minimum faunal

percentages (MFP, see Method 3 and Sanders, 1960;

Barnard, 1964) compares samples by pairs to deter-
NUMBER 44

mine if both samples of a pair contain specimens of

one species. An index is found (Method 3) for all the

joint occurrences of species in all pairs of samples and

these values are stored in matrices (trellises, like

Figure 4) or in a data deck composed of cards on which

are entered the pair of sample numbers (conjoint

sample) and the index of faunal affinity. The cards

are reordered so that a conjoint sample with a high index value is joined by another conjoint sample containing a joint sample number and having the next highest

index value. Conjoint samples are thereby clustered

so that a master matrix can be formed to give a visual

impression of the degree of continuity among samples.

Dendrograms can be constructed according to the

Mountford method (Method 5, Appendix IV).

The method MFP emphasizes the internal

homogeneity of a single sample because the factors

in the computed indices are based on the percentage

composition of each species in the sample. The method

of Morisita-Ono (Method 4, Appendix IV) is an

elaboration of correlative methods in which each

species in terms of its frequency is independent of the

others within a sample. The numbers of specimens of

taxa occurring in both members of a pair of samples

(conjoint) are the correlative factors, but the vagaries

of comparing pairs of samples with low and high

specimen frequencies are accounted for in the lambda

values. Clusters of samples identified in the data deck

of CA values can be extracted, trellis diagrams constructed of the values, or dendrograms formed by

Method 5 so that the results are comparable to the

method of MFP.

In the chapter to follow, various incongruities in the

dendrogrammatic analysis of faunal indices are discussed. Although the broad outlines of sample clustering are presentable with the dendrogrammatic method

and a measure of the distance between contiguous

clusters becomes evident, one must also resort to examination of the matrices of faunal indices in order

to understand incongruities that result from the 2-

dimensional restrictions of dendrograms. Sticks and

lumps of clay marked with sample numbers are utilized

to reorder the dendrogrammatic clusters so that triads,

quartets (. . . etc.) of samples can be better visualized. The higher a conjoint value of CA or MFP scores,

the closer the samples are positioned to each other by

pairs. From this experience one develops a visual

method of arranging samples in three dimensions by

coded cards (Method 6). The relative simplicity of the

362-694 O—70 2

San Quintin samples facilitated a view of the broad

outlines of sample relationships. To compress this

arrangement into two dimensions for publication, a

maze-grid is adopted (Figure 11). This method of

presentation has advantages as a visual memory device

incorporating information on the contiguity of samples

plotted as a function of the area each sample includes.

Heavy walls between adjacent samples simulate a low

joint faunal index, whereas lack of heavy walls indicates high conjoint indices. Windows in heavy walls

indicate conjoint indices of medium levels. Several best

fits are possible in the arrangement. Letters drawn in

various sizes indicate the dominant and subdominant

species of each sample (based on frequencies of specimens) . Maze lines of Figure 18 indicate the lines of

relationship of samples so that ectones can be

visualized.

The Communities

Methods 1-6 (Appendix IV) reveal 10 main foci of

assemblages in the San Quintin samples, characterized

by the following taxa: (1) Zoster a, as represented by

various amphipods and a polychaete obligatorily associated with the eelgrass; (2) Ampelisca,Eugyra; (3)

Acuminodeutopus, Pista, Rudlilemboides; (4) Prionospio; (5) Fabricia; (6) Kalliapseudes; (7) Scoloplos

acmeceps; (8) Cossura; (9) Cirriformia; (10)

Exogone.

Three primary groups of species determined from

Method 1 represent three areas of high population

density in San Quintin: (1) the Zortira-community as

indicated by the occurrence of Ericthonius, Capitita,

Elasmapus and Platynereis; (2) the channel community with Eugyra and Ampelisca; and (3) the intermediate sandflat zone with Pista, Acuminodeutopus,

and Rudilemboides. The first two associations are obvious to the field observer. Subdominant species are

also strongly bound to these associations (Figures 1-3).

Still other minor associations are apparent but represented by insufficient samples for extended analysis.

These are focused on Cirriformia, Scoloplos, Kalliapseudes, and Fabricia. Taxa that are widely dispersed

through several communities in contagious numbers

are rarely as abundant in the bay as are the primary

and even some secondary dominants of the primary

communities. Exogone verugera is the most conspicuous exception to this rule.

The unity of the assemblages determined in Method
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

1 is demonstrated by the low coefficient scores among

contagious dominants from one community to another.

Only in contagious numbers do the communities show

strong internal cohesion, whereas those indices calculated for dominant community species utilizing all

samples (n=90) are very low and similar among

themselves as shown on the left side of the matrix in

Figure 5. Only Eugyra and Ericthonius in Figure 5

show strong exclusion from joint occurrences in noncontagious samples. Although Eugyra and Ampelisca

are strongly correlated in those samples in which they

are contagious (Figures 1 and 2), they occur together

in subcontagious condition very frequently throughout

the bay. Neither is strongly dissociated from other

species-pairs that are shown to dominate samples when

collected in contagious frequencies.

Method 1 fails (1) to pinpoint Prionospio as a basic

dominant of the sandflat community or (2) to demonstrate that in reality the Acuminodeutopus-Rudilemboides-Pista association is intercalated between the

channel community (Ampelisca-Eugyra) and the full

extreme of the sandflat community represented by

Prionospio. The latter taxon occurs in all of the communities and is therefore masked from any significant

pairing. It occurs in the Zostera-Ericthonius community not as an integral part of the community above

root level but in the mud-sand substrate on which the

Zostera grows. If the zosteral elements are determined

and eliminated from the calculations the Prionospio

component shows more clearly in the calculations.

The strong cohesion between the Ampelisca-Eugyra

association and the Acuminodeutopus association can

be seen in Figure 1 in the number of lines directly connecting the two, whereas most of the lines leading from

the Ericthonius-Capitita ( = Zostera) association connect only with poorly associated subdominants. The

superiority to the method shown in Figure 1 of another

simple calculation shown in Figure 2 occurs in the preponderance of lines connecting the Ampelisca-Eugyra

association with the Acuminodeutopus-Pista association. Only those samples with species in contagious condition are used in the formula with n=a+b—h . But

again, Prionospio, paired only with Cirriformia, is

submerged. The weakness of utilizing noncontagious

samples (n=90) is shown in Figure 3.

Methods 3 and 4 of correlating species and their

frequencies by intersample comparison are superior in

relegating samples to clusters that pinpoint associations. The Morisita-Ono correlation method and

Sanders minimal faunal percentage methods have

different results. The Morisita-Ono method excels in

bonding together samples with similar dominant species, whereas the Sanders method, in accounting for

internal homogeneity of a sample, occasionally displaces a sample with extreme monospecific domination to a branch outside the basic community. The

dendrogrammatic presentation in either case suffers

the defect of segregating certain closely related pairs

of samples in favor of others. For instance, samples 78

and 67 in Figure 10 together have a higher index of

association than 78 has with any other sample, yet 78

is separated from 67 by three dendrites (samples 35,48,

and 20) and is paired with 65 only at a much lower

level than with the others. These are vagaries of statistics in two dimensions on binary cycles.

A pair of dendrograms summarizing 20 samples

from the five major assemblages in San Quintin (Figures 9, 10) incorporates a strongly dominated, a weakly

dominated, and 2 intermediate samples from each

assemblage. The strong cohesion of the Zostera community again demonstrates the usefulness of the simple

methods, but there emerges also the previously assumed

affinity of the Zostera community to the basic Prionospio community on which it has presumably been

superimposed. The Morisita-Ono method (Figure 10)

of sample comparison is shown to be superior to that

of minimum faunal percentages because it results in

sample 78, highly dominated by Ampelisca, being

joined with those of its congeners moderately dominated by both Ampelisca and Eugyra. Sample 14, numerically dominated by Prionospio but originally

selected as a weak Fabricia sample, is also more properly joined to the Prionospio community in Figure 10.

The method of MFP does detect, very ably, the degree

of homogeneity of samples, because samples 14 and 78

are highly aberrant and have very low faunal

coefficients.

The dendrogrammatic method, as is well known,

does present difficulties in leading to erroneous visual

impressions as to the affinity of samples. A superior

presentation (Figures 11 and 18) results from visually

arranging samples in clusters and dendrites in three

dimensions by utilizing cards covered with symbols of

taxal frequencies (Method 6). Compression of the resulting "tree" in a grid of two-dimensions (Figure 11)

then necessitates forming a "maze-grid" (Figure 18)

in which samples or groups of samples are separated

by walls often penetrated by windows demonstrating
NUMBER 44

partial affinity between samples. A family of community foci is formed and pathways of affinity demonstrate

the spectral character of community interrelationships.

The Acuminodeutopus-Rudilemboides ecotone is reduced in prominence in favor of other ecotones or community phases of even greater importance in terms of

areal distribution.

The Problem of Subcommunities

The Zostera community is sharply defined statistically

and in physical view, but other communities need further testing to determine their internal cohesiveness

and their discreteness from contiguous associations.

They are communities with sediments as the only

substrate.

Slightly more than half (eight) of those samples previously determined by Barnard (1964) as belonging to

an Acuminodeutopus-Rudilemboides association within the amphipodan subcommunities have been allocated to the Ampelisca-Eugyra community in the

analysis of all species other than amphipods. A few of

the samples (six) have been assigned by previously discussed methods to the Prionospio association and one

sample is probably a member of the Zostera association.

Most of these samples now assigned to the Prionospio

association belong to those zones primarily characterized in frequency by Exogone or Cossura. All of the

samples assigned to the Ampelisca-Eugyra community

have been connected with the facies in which Ampelisca is predominant. This is of course a function of the

artificial procedure of analyzing only Amphipoda, for

Ampelisca is an amphipod and dominates numerous

samples in which Acumindeutopus and Rudilemboid.es

are just as abundant as they are in those Eugyra samples having low Ampelisca dominance. Utilization of

just one order of organisms for indication of community structure turns out to be unsatisfactory. Subdominant organisms may thus form a pattern distinct from

dominant organisms and not be bound obligatorily

to primary dominants. But the AcuminodeutopusRudilemboides association broadly binds Prionospio

samples to Ampelisca-Eugyra samples once the strictly

fiugyra-dominated samples are ignored (Figures 11

and 18).

The problem is to determine whether the AmpeliscaEugyra community is linked to the Prionospio association through the facies Acuminodeutopus-Rudilemboides. Thinking in reverse suggests the possibility that

Prionospio is the base of the primary lagoon community and that the Eugyra-Ampelisca facies is superimposed on a Prionospio background in response to channelization of lagoon waters. A Prionospio community

occupying inshore sands along the coast of California

has already been described by Barnard (1963). One

might expect the Prionospio community to have penetrated into shallow lagoons but whether the EugyraAmpelisca association is an imposition upon that base

or a discrete community that merges with Prionospio

requires examination.

Prionospio has a poor coefficient of association with

other taxa in San Quintin because it is widely dispersed throughout the bay. Its occurrence in the

Zostera community is apparently similar to the concurrence of Ampelisca and can be explained by the grab

sampler collecting not only eelgrass but surrounding

substrate that is not part of the discrete Zostera-Ericthonius assemblage. The frequency of Prionospio in

the core of the Eugyra-Ampelisca community (Table

3) is 876 per square meter, but in its restricted association (Table 5) it occurs in a frequency of 3130 per

square meter. Prionospio is therefore reduced in frequency in the channel community, the latter not being

a simple imposition on a Prionospio base.

A continuum of samples from one extreme to the

other can be arranged as in Figure 6. On a basis of

percentage of the fauna in each sample, Eugyra and

Ampelisca are replaced by increments with Acuminodeutopus-Pista-Rudilemboides and all five taxa further

replaced by Prionospio. Fifty samples qualify for inclusion in Figure 6 (but weak Prionospio samples are

omitted) with each dominant comprising more than

20 percent of the specimens in the samples. Only seven

samples are not clearly dominated by any of the primary members but only three of those seven have an

exceptional percentage of the Acuminodeutopus-Pista

associates. The other four seen in Figure 6 show clear

numerical domination by Prionospio. The Acuminodeutopus-Rudilemboides ecotone is therefore only a

weak link to the Prionospio community and is confined

primarily and very clearly to the Eugyra-Ampelisca

community.

Other tests of the continuum potential in this ecotone

between Eugyra-Ampelisca and Prionospio dominated

bottoms are presented in Figure 8. These dendrograms

are based on MFP and CX indices and are composed

from 15 samples marked with asterisks in Figure 6. The

dendrograms are comparable except for sample 64

alternating between the Prionospio and Eugyra den-
8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

drites. Sample 64 is a strong mixture of specimens of

Acuminodeutopus (267), Ampelisca (63), Rudilemboides (221), Capitita ambiseta (41), Chone (67),

Cossura (22), Exogone (511), Pista (212), Prionospio

(330), Scoloplos acmeceps (111), and Eugyra (198);

therefore it is a universal sample matching with all

other samples moderately well but never pairing

strongly with any.

The allotment of Acuminodeutopus-Rudilemboides

samples into both dendrites of the Prionospio and

Ampelisca assemblages and the relatively low CA indices indicate the narrow spectral character of the

merger between the two assemblages.

Description of the Communities

Communities of the San Quintin benthos can be described despite the partial continuum among various

segments of the environment seen in dendrograms and

the maze-grid. Samples are segregated from the clusters

seen in the maze-grid (Figure 11) and the communities

described by ranking species and listing their frequencies in Tables 2-8. The foci of the communities are

based mainly on samples having the main species in

contagious frequencies. The Eugyra-Ampelisca community is described as a unit whole in Table 3 but split

into its two phases in Table 4. The Prionospio community in its purely dominant form is described in

Table 5, while one of its phases characterized by Cossura (Table 6) is described separately. The ExogoneAcuminodeutopus-Rudilemboides ecotone (Table 8)

forms a link strongly penetrating the Fabricia community (Table 7), but without Exogone the other

dominants are found most prominently as subdominants in the Eugyra-Ampelisca community. The

Zoster a community is described as a unit (Table 2)

and although its sedimentophilous species show considerable variations, the component directly associated

with the plant seems to be the least variable and highly

specific of any in the bay. The three samples dominated

by Kalliapseudes (10,13, 28) are enigmatical. Various

other samples acting as intergrades (18, 49,50, 73, 84)

or several very impoverished samples are omitted or

utilized in two places.

Communities are listed in emerging order from the

first detected to the least clarified and the samples for

each are listed in order from strongest to weakest. Samples in parentheses are very weakly categorized and

usually not reported upon in various tables or in the

maze-grid. Samples without dominants are 72 and 86.

Figure 15 shows the areal distribution of the communities in the east arm of Bahia de San Quintin.

The Zostera-Ericthonius-Capitita Community

TABLE 2

SAMPLES.—61, 62, 70, 66, 81, 79, 34, 87, 89, 53, 74,

90,85,83,57.

DISTRIBUTION.—Primarily on banks in the outer

third of the bay.

Zostera has not been measured either in frequency

or standing crop in this community, but its presence is

clearly indicated by the occurrence of various amphipods, Ericthonius brasiliensis, Hyale frequens, Pontogeneia quinsana, Elasmopus antennatus, and by the

polychaete Platynereis bicanaliculata. Another polychaete, Capitita ambiseta, is a major dominant but not

wholly restricted to this community. Possibly it lives in

the substrate and increases enormously in abundance

as a response to the presence of Zostera. A major share

of the individuals of Armandia bioculata, Modiolus

species, and Corophium acherusicum live in this

community.

The Prionospio community probably forms the substrate on which this epifloral community is superimposed. Prionospio is almost as numerous as it is in its

own community, Cossura Candida increases fourfold,

although Scoloplos acmeceps and Onuphis microcephala decrease by half, while ghost-shrimps and

transennellid clams are excluded.

The Zostera community is the most highly specific

of the assemblages in San Quintin Bay. It has more

species fully confined to its margins and thus is most

sharply defined by those distributions than any other

assemblage. The low internal homogeneity of the community is nevertheless recognizable in Figures 7 and 11.

The Eugyra-Ampelisca Community

TABLES 3, 4

SAMPLES.—Mixed community: 73,50, merging with

Prionospio 18.

Eugyra phase: 67, 60, 35, 76, 77, 51, 46, 48, 43, 56,

20, 52.

Ampelisca phase: 69, 44, 78, 65, 15, 12, 31, 22.

DISTRIBUTION.—Channels, side channels, feet and

slopes of banks, the Ampelisca phase in the deepest
NUMBER 44

TABLE 2.—Rank and abundance of species in the ZosteraEricthonius-Capitata community based on samples with

the two latter dominants comprising 30-\- percent of the

specimens: (stations SQ, 34, 53, 61, 62, 66, 70, 79, 81,

87, 89)

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Name of species

Ericthonius brasilicnsis

Capitita ambiscta

Hyale frequens

Exogonc verugera

Cossura Candida

Prionospio malmgrcni

Lembos macromanus

caprcllids

Plata alata

Elasmopus antennatus

Rudilcmboidcs

stcnopropodus

ncbalian

Pontogencia quinsana

Platyncreis bicanaliculata

Ampelisca comprcssa

Ncanthes caudata

Corophium baconi

Orchomenc magdalencnsis

Listriella raclanica

Scoloplos acmeceps

Acuminodcutopus

hctcruropus

Armandia bioculata

Onuphis microcephala

Corophium acherusicum

ncmerteans

Modiolus sp.

holothurians

Lumbrineris minima

Chone mollis

Megalomma pigmcntum

Microdcutopus schmitti

Individuals

per square

meter

9,160

4,500

2,950

2,050

2,000

1,860

1,020

755

465

360

325

278

257

222

216

211

195

188

160

142

125

125

118

112

101

83

72

72

69

58

53

Percentage

total individuals of

study in this

community

97

73

88

12

34

20

77

30

31

83

7

21

86

82

1

16

47

18

31

6

4

64

22

54

10

67

12

13

8

10

3

Minor species are listed in sentence order below with individuals per square meter: Amphipholis squamata 38, shrimp 35,

Stenothoe valida 32, Ampithoe plumulosa 30, PTricolia sp. 29,

Ampithoe longimana 27, Nephtys caecoides 27, Pseudokoroga

rima 26, Scoloplos ohlini24, Mitrellacarinata 18,enteropneusts

16, Amphideutopus oculatus 14, Aoroides columbiae 14, Eugyra

glutinans 13, Erichsonella crenulata 11, flatworm 11, Paraphoxus heterocuspidatus 10, Amphilochus neapolitanus 8,

Paracerceis sculpta 8, Axiothclla rubrocincta 8, Spiophanes

missioncnsis 8, Oxyurostylis tcrtia 8, tanaid 8, Paraphoxus

bicuspidatus 6, Haliophasma geminata 6, Lumbrineris erecta 6,

Nerinides maculata 6, Notomastus magnus 6, Microjassa

parts (6-8 meters) and the Eugyra phase generally in

depths of 3-5 meters, the evenly mixed samples in extremes of 10 and 3 meters.

Although more than 84 percent of the individuals of

both Ampelisca and Eugyra occur in this community

the two taxa occur in significant frequencies in the

Exogone ecotone, in the Kalliapseudes samples, and in

low frequencies in other communities. Lysianassa holmesi, Tellina buttoni, Uristes entalladurus, and Paranthura elegans are obligatory companions of Ampelisca,

while Microdeutopus schmitti is confined primarily to

the Ampelisca phase of this community. Additional indicators of the mixed community are Amphideutopus

oculatus and nebalians, while numerous other species

preponderantly belong with this community.

If the Prionospio community forms the base on

which is superimposed the numerous dominant and

characteristic species of the Eugyra-Ampelisca community, it is indicated by the presence of Cossura candida and Scoloplos acmeceps in undiminished numbers

but Prionospio malmgreni is reduced to a third of its

frequency in its own community. Significant numbers

of Capitita ambiseta, a characteristic member of the

Zostera community, also occur in the channels.

The Prionospio Community

TABLE 5

SAMPLES.—14, 16, 19, 29, 47, 71, 17, 49, 58, 36,

23, 37, 11, 21, (8), merging with Eugyra-Ampelisca

18, Exogone-Eugyra 64, and Exogone-Cossura 38.

DISTRIBUTION.—Widespread throughout the inner

two thirds of the bay on sand flats in depths not

favored by Zostera.

Prionospio malmgreni is generally three times more

abundant than it is in any other community except

that of Zostera; Cossura Candida and Scoloplos acmeceps are the second and third dominants; either species

also forms the dominant of a phase of this community.

Onuphis microcephala is prominent, the mollusk

macrocoxa 5, Munna ubiquita 5, Acmaea depicta 5, Arenicola

cristata 5, cumacean 5, crab 5, Ciliacea sp. 5, Listriella diffusa 3,

Goniada littorea 3, Hypoeulalia bilincata 3, Monoculodes

hartmanae 2, Paraphoxus obtusidens 2, Aequipecten c. aequisulcatus 2, Leptopecten latiauratus 2, nudibranch 2, Brania

clavata 2, Chrysopetalum occidental 2, Cirriformia luxuriosa 2,

Dorvillea articulata 2, Glyccra amcricana 2, Lepidonotus

caelorus 2, Ophiodromus pugettensis 2, Polyophthalmus pictus

2, Scyphoproctus oculatus 2, Cumella sp. 2, isopod 2.
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 3.—Rank and abundance of species in the EugyraAmpelisca channel community, based on samples with primary dominants comprising 20-\- percent of the specimens:

(SQ 12, 15, 18, 35, 44, 46, 48, 51, 60, 65, 67, 69,

73, 76, 77, 78)

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

Name of species

Ampclisca compressa

Eugyra glutinans

Rudilemboides

stenopropodus

Lysianassa holmesi

Acuminodcutopus

hctcruropus

Microdcutopus schmitti

Prionospio malmgrcni

Amphidcutopus oculatus

Capitita ambiseta

nebalian

Paraphoxus obtusidens

caprdlids

Cossura Candida

Scoioplos acmcceps

Oxyurostylis tcrtia

Uristcs cntalladurus

nemcrtcans

Pista alata

holothurians

Orchomenc magdalenensis

Neanthes caudata

Scyphoproctus oculatus

Chone mollis

Fabricia limnicola

Exogonc vcrugcra

Mcgalomma pigmcn turn

Lumbrincris minima

Paranthura clegans

Corophium baconi

Kalliapseudcs crassus

Actcocina carinata

Lembos macromanus

Paraphoxus hctcrocuspidatus

Haploscoloplos elongatus

Axiothella rubrocincta

Tdlina buttoni

Brania clavata

Onuphis microccphala

Individuals

per square

meter

15,966

6,550

1,990

1,449

1,000

898

876

737

727

641

522

506

378

365

246

259

229

227

217

211

184

166

159

152

146

133

118

HI

107

101

88

83

82

76

74

73

60

58

Percentage of

total individuals of

study in this

community

84

91

65

99

46

86

15

92

19

77

61

32

10

25

72

98

38

24

59

33

23

62

31

4

1

36

34

84

41

1

32

10

58

86

52

84

26

17

Minor species are listed in sentence order below with individuals per square meter. Listriella melanica 57, Lyonsia

californica 53, Transennella tantilla 50, Nerinides maculata

46, Armandia bioculata 44, Corophium acherusicum 39,

Pseudokoroga rima 38, Paraphoxus bicuspidatus 38, OxyuTransennella tantilla characteristic, and ghost-shrimps

Callianassa species construct their major beds in this

community.

The Cossura Phase of the Prionospio Community

TABLE 6

SAMPLES.—26, 32, 41, 9, 24, 39, 45, 27, merging

with a mixed sample 54 (Eugyra-Fabricia), and Exogone-Prionospio 38, and Prionospio-Eugyra 64.

DISTRIBUTION.—At the margins of the Prionospio

community primarily in the middle third of the bay,

not occurring in the outer third.

This ecotone links the Prionospio community with

the Exogone samples. Cossura Candida is the most

numerous and clearly dominant species. Prionospio

malmgreni is the secondary dominant and Exogone

verugera is the third most abundant species. The only

phoronids collected in the bay occur in this zone, and

Cirriformia luxuriosa is a prominent subdominant.

The Scoioplos Phase of the Prionospio Community

SAMPLES.—€3,88,40,84, (59), (68).

DISTRIBUTION.—Generally inshore, near marshes on

the east side of the outer bay.

These samples, averaging 12 species each, are very

impoverished. Only 5 species are of any importance:

Scolopos acmeceps 812, Acteocina carinata 96, Nerinides maculata 84, Megalomma pigmentum 64, and

Exogene verugera 32 individuals per square meter.

rostylis pacifica 35, tanaids 32, Nephtys caecoides 28, enteropneusts 25, Scoioplos ohlini 25, Modiolus sp. 21, flatworm

20, Ampithoe plumulosa 19, Amphipholis squamata 17, nudibranchs 12, Cirriformia luxuriosa 12, Platynereis bicanaliculata 12, Hippomedon denticulatus 11, Microjassa macrocoxa 11, Haliophasma geminata 9, Haminoea sp. 8,

Spiophanes missionensis 8, Monoculodes hartmanae 7,

Anaitides multiseriata 6, Metaphoxus fultoni 5, Polydora

uncata 5, Cumella sp. 5, Heterophoxus oculatus 4,

Hyale frequens 4, Goniada littorea 4, Macoma yoldiformis 3,

Solen rosaceus 3, Anaitides williamsi 3, Glycera americana 3,

Lepidonotus caelorus 3, shrimp 3, Serolis carinata 2, Parvilucina tenuisculpta 2, Trachycardium quadragenarium 2,

Eteone dilatae 2, Pherusa capulata 2, Typosyllis variegata 2,

Callianassa sp. 2, Corophium uenoi 1, Cooperella subdiaphana

1, Mitrella carinata 1, Eteone pacifica 1, Lumbrineris erecta

1, Polyophthalmus pictus 1, Trypanosyllis gemmipara 1,

Oxyurostylis sp. 1, Odostomia fetella 1, cumacean 1.
NUMBER 44 11

TABLE 4.—Rank and abundance of dominant species in extreme phases of the AmpeliscaEugyra community

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

Name of species

Ampclisca comprcssa

Eugyra glutinans

Rudilcmboidcs stenopropodus

Lysianassa holmcsi

Microdcutopus schmitti

Acuminodcutopus hetcruropus

Capitita ambiscta

Prionospio malmgrcni

nebalian

Amphidcutopus oculatus

Paraphoxus obtusidcns

Scoloplos acmcceps

caprellids

Cossura Candida

Uristes cntalladurus

nemcrteans

Oxyurostylis tcrtia

Orchomenc magdalenensis

Pista alata

Neanthes caudata

holothurians

Scyphoproctus oculatus

Chone moll is

Individuals per square meter

Ampelisca phase

Samples 12, 15,

44, 65, 69, 78

41,200

6,700

2,975

3,680

2,060

1,030

878

646

1,675

1,167

935

224

300

123

1, 160

189

149

472

294

75

235

350

182

Eugyra phase

Samples 35, 51,

60, 67, 76, 77

470

9,470

2,220

165

328

1,486

1,057

1,342

35

972

302

670

1,017

683

37

376

248

37

300

412

215

94

189

The Fabricia Community

TABLE 7

SAMPLES.—6, 3, 42, 55, 91, 33, 1, 2, merging with

Exogone 5,4, 7.

DISTRIBUTION.—Dominating fine silt sediments of

the inner bay bordered by marsh and in widely scattered inshore localities of the outer bay adjacent to

marshes.

The most numerous organism of this community is

Exogone verugera, but it is a small bodied polychaete

not dominating the standing crop. Fabricia limnicola,

the second most frequent, dominates the standing crop.

Over 80 percent of the individuals of Fabricia occur

in this community. The most highly characteristic species are chironimid larvae (100 percent), the amphipod Corophium uenoi (99 percent), and tanaids other

than Kalliapseudes (88 percent). Polydora uncata,

Acteocina carinata. Scolopos ohlini, and Acuminodeutopus heteruropus are conspicuous subdominants.

The Kalliapseudes samples

SAMPLES.—28,13,10.

DISTRIBUTION.—In deep channels of the middle bay

or in shallow channels of the inner bay but deepest

of their areas.

The dominant individuals per square meter of these

samples are: Kalliapseudes crassus (54,800), Exogone

verugera (25,000), Ampelisca compressa (12,860),

Orchomene magdalenensis (1,569), Typosyllis

variegata (747), Metaphoxus fultoni (577), Listriella

melanica (416), Heterophoxus oculatus (315), Cirolana diminuta (277), and Scyphoproctus oculatus

(277).

At its peak of abundance, Kalliapseudes has a standing numerical frequency of 140,000 individuals per
12

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 5.—Rank and abundance of species in samples clearly dominated by Prionospio

malmgreni: SQ 11, 14, 16, 17, 19, 21, 23, 29, 36, 37, 47, 58, 71

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

18

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

Name of species

Prionospio malmgreni

Coasura Candida

Scoloplos acmeccps

Onuphis microcepbala

Acuminodeutopus hcteruropus

Capitella capitata

Callianassa SDCCICS

Exogone verugera

Neanthes caudata

Paraphoxus obtusidens

Transennella tantilla

nemcrtcans

Fabricia limnicola

holothurians

enteropncusts

Scoloplos ohlini

Rudilemboidcs stenopropodus

Cirriformia luxuriosa

Brania clavata

Pistaalata

caprdlids

Oxyurostylis tcrtia

Polydora uncata

LJstriella melanica

Ampelisca comprcssa

Megalomma pigmcntun

Hctcrophoxus oculatus

Ncrinidcs maculata

Eugyra glutinans

Paraphoxus hetcrocuspidatus

Capitita ambiseta

Chonc mollis

Lumbrineris minima

Marphysa sanguinea

Acteocina carinata

Axiothella rubrocincta

Microdeutopus schmitti

Solen rosaccus

Ericthonius brasiliensis

Hyalefrequens

LJstriella diffusa

nudibranchs

Arabella iricolor

Scyphoproctus oculatus

Oxyurostylis pacifica

Eteone pacifica

Notomastus magnus

Amphideutopus oculatus

Coropbium uenoi

Hippomedon denu'culatus

Total

2,541

448

222

186

88

87

74

70

68

60

50

42

37

36

32

28

27

24

23

22

19

19

19

19

17

16

16

13

12

11

11

10

9

9

7

7

5

5

3

3

3

3

3

3

3

2

2

1

1

1

Individuals

per square

meter

3,130

550

273

229

108

107

91

86

84

74

62

52

45

44

39

34

33

29

28

27

23

23

23

23

21

20

20

16

15

14

14

12

11

11

9

9

6

6

4

4

4

4

4

4

4

2

2

1

1

1

Percentage

total individuals

of study in

this community

44

12

16

55

4

37

89

negl.

8

7

50

7

1

10

7

10

1

19

10

2
NUMBER 4 4 13

TABLE 5.—Rank and abundance of species in samples clearly dominated by Prionospio

malmgreni: SQ 11, 14, 16, 17, 19, 21, 23, 29, 36, 37, 47, 58, 71— Continued

Rank

51

52

53

54

55

Name of species

Monoculodcs hartmanae

Pontogeneia quinsana

Uristes entalladurus

Cumella species

Amphipholis squamata

Total

Individuals

per square

meter

Percentage

total individuals

of study in

this community

square meter. Species obligatorily bound to, or charasteristic of these samples are, Kalliapseudes crassus

(100 percent), Typosyllis variegata (100), Metaphoxus fultoni (88), Cirolana diminuta (100), and

Heterophoxus oculatus (70).

The Exogone-Acuminodeutopus-Rudilemboides

Ecotones

TABLE 8

SAMPLES.—8 0 , 25, (30), (7), (75), merging with

Fabricia 5, with Eugyra-Prionospio 64, and with

Prionospio-Cossura 38.

The miscellaneous samples, with mixed dominants

having Exogone as a prominent numerical member

comprise various strong intergrades among all the

communities except Zostera. Even sample 25 has the

barest indication of proximity to a Zostera bed, with

an occurrence of individuals of Elasmopus, Ericthonius, and Hyale. Sample 25 is near the abandoned pier

and has the majority of specimens of Capitella capitata

occurring in the bay, thus indicating some history of

pollution, artificial or natural, possibly from debris generated by fouling organisms on the pilings. Sample 5 is

also assigned to the Fabricia community of the upper

bay; the other samples are adjacent to shore, 80 near a

marsh and the Fabricia zone, 38, 64, and 30 on the

midwestem shore. Sample 64 is so strongly dominated

by Eugyra glutinans and Prionospio malmgreni that I

have assigned it to the former community also. Exogone

is a poor indicator of its own ecotone for the species is

widely distributed through other communities; only

when extremely abundant or occurring as the superior

numerical dominant does it indicate either a speciesimpoverished area or a mixed sample.

362-694 O—7(

Relationship of Communities to Sediments

The range of sedimentary median diameters of San

Quintin samples, in which community dominants have

been identified, is extreme. The central tendencies of

the sample-groups are determined as median points of

the median diameters (Table 9) rather than averages,

because of extreme skewing that results from averaging

these data. There are significant differences in these

median points between the Fabricia and the EugyraAmpelisca communities. They show that the Fabricia

community occupies silts of very fine texture adjacent

to marshes, whereas the Eugyra-Ampelisca community

occupies medium and fine sands of the channels (Figures 13, 14). Prionospio samples have a median point

in the coarse silt range and Zostera in fine sand.

The fact that the six most important Fabricia samples occur on fine silts of approximately 9 microns

median diameter indicates the possibility that the other

three samples occurring on sands of approximately

130 microns median diameter represented a surface

veneer of fine silt on top of medium sand and that the

sampling device bit into the subsurface sand resulting in a mixed sample. If this occurred in one community it may have occurred in others even though

such mixing appeared to be very low during field operations. The sedimentary data are thus potentially poor

but a relationship of dominant taxa occurs to median

diameters and percent sand (Figure 12).

Relationship of the Lagoonal Community to the

Open Sea

Open-sea benthic communities of the eastern Pacific

Ocean are poorly known. Those described from the

semiarid coast of California, 300 miles north of San
14 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 6.—Rank and abundance of species in Cossura phase of Prionospio association:

SQ, 9, 24, 26, 27, 32, 39, 41, 45

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

Name of species

Cossura Candida

Prionospio malmgreni

Exogone verugera

Acuminodeutopus heteruropus

Cirriformia luxuriosa

Capitita ambiseta

Scoloplos acmeceps

Megalomma pigmentum

Chone mollis

Lumbrincris minima

Neanthes caudata

Rudilemboidcs stenopropodus

nemertcans

Pista alata

Brania clavata

enteropneusts

holothurians

Scoloplos ohlini

phoronids

caprcllids

Scyphoproctus oculatus

Ampelisca compressa

Listriella melanica

Nephtys caecoides

Paraphoxus obtusidens

Amphilochus neapolitanus

Heterophoxus oculatus

Oxyurostylis tertia

Amphideutopus oculatus

Microdeutopus schmitti

Nerinides maculata

Notomastus magnus

Kalliapseudes crassus

Callianassa spp.

Ericthonius brasiliensis

Listriella diffusa

Orchomene madgalcnensis

Paraphoxus bicuspidatus

Paraphoxus hetcrocuspidatus

Paranthura elegans

Serolis carinata

Tellina buttoni

nudibranch

Etcone dilatae

Glycera amcricana

Polydcra uncata

Cumella species

Total

1,075

463

110

82

74

65

64

48

47

45

40

33

32

30

27

23

22

22

21

18

13

9

6

6

4

3

3

3

2

2

2

2

2

2

1

1

1

1

1

1

1

1

1

1

1

1

1

Individuals

per squre

metear

2, 150

926

220

164

148

130

128

96

94

90

80

66

64

60

54

46

44

44

42

36

26

18

12

12

8

6

6

6

4

4

4

4

4

4

2

2

2

2

2

2

2

2

2

2

2

2

2

Percentage

total individuals

of study in

this community

29

8

1

4

60

2

4

13

9

13

5

1

5

3

12

5

6

8

100

1

5
NUMBER 4 4 15

TABLE 7.—Rank and abundance of species in samples

assigned to the Fabricia zone: SQ 1, 2, 3, 4, 5, 6, 33,

42, 55, 91

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Name of species

Exogone verugcra

Fabricia limnicola

tanaids

Corophium ucnoi

Acuminodeutopus

hctcruropus

caprellids

Prionospio malmgreni

Scoloplos ohlini

Actcocina carinata

insect larvae

Scoloplos acmeceps

Polydora uncata

Rudilemboides

stenopropodus.

Neanthes caudata

Ampelisca compressa

Brania clavata

nemcrteans

Pontogeneia quinsana

Oxyurostylis tertia

Oxyurostylis pacifica

Paraphoxus obtusidens

Individuals

per square

meter

3,030

2,715

1, 190

681

392

350

278

185

168

133

96

90

85

66

51

51

35

35

34

27

22

Percentage

total individuals of

study in this

community

17

82

88

99

11

14

3

44

39

100

4

62

2

5

0

14

4

11

6

38

2

Minor species are listed in sentence order below with

individuals per square meter: Paraphoxus heterocuspidatus

18, Ampithoe pollex 16, Corophium baconi 16, Nerinides

maculata 16, Paranthura elegans 16, Hyale frcquens 14,

Cossura Candida 11, Eugyra glutinans 11, Corophium acherusicum 11, Ampithoe plumulosa 8, enteropneust 6, Lembos

macromanus 5, Chone mollis 5, Axiothella rubrocincta 3,

Eteone pacifica 3, Megalomma pigmentum 3, Scyphoproctus oculatus 3, Capitita ambiseta 2, Platynereis bicanaliculata

2, Callianassa sp. 2, Paraphoxus bicuspidatus 2, stenothoid

2, Uristes entalladurus 2, nudibranch 2, Amphideutopus

oculatus 2, Hetcrophoxus oculatus 2, Listriella melanica 2.

Quintin, have been primarily conspicuous soft-bottom

assemblages (Barnard and Hartman, 1959; Barnard

and Ziesenhenne, 1961; Barnard, 1963). The latter

paper is pertinent to this discussion because it describes

benthic assemblages on shallow-water open-sea bottoms. In depths of about 10 to 30 meters, outside the

surf zone on sand and fine-sand bottoms, the biota is

dominated by the clam Tellina buttoni and the polychaete Nothria elegans. This megacommunity is composed of two extremes dominated primarily by Tellina

on fine sediments and Nothria on coarse sediments

with intermediate sediments dominated by both species together. Shallow sands in depths of 4-10 meters,

on the inshore margin of the 10-30 meter coastal

strip, are dominated by the small polychaete Prionospio

malmgreni. This animal also occurs in the TellinaNothria community fades, but in the 4-10 meter zone

it overwhelmingly dominates the fauna. It is 4 to 13

times more abundant in the 4-10 meter zone than in

the 10-30 meter zone. In the Prionospio zone, Tellina

occurs sparsely, 6 to 18 times less abundant than in

the 10-30 meter zone. Nothria elegans is completely

absent from the Prionospio zone. Barnard (1963) thus

considers the Prionospio zone as an orthodox softbottom community.

In Bahia de San Quintin the so-called Prionospio

community is a "background" community on which,

perhaps, are superimposed the more diversified eelgrass

and channel assemblages. The lagoonal community

may be compared cursorily to the open-sea community

(Table 10) and in greater detail to the lists published

in a limited distribution report by Hartman, Barnard,

and Jones (1960). The two representations of the

Prionospio community, open sea and lagoonal, differ

considerably. Of the 14 most abundant species in the

open-sea assemblage, only 6 occur in San Quintin and

only one of those, Prionospio malmgreni, is among the

14 most frequently occurring San Quintin species.

Fifty-four species of animals have been collected in

the San Quintin assemblage, of which 47 have been

named. Only 11 of those species also occur among the

225 + species found by Hartman, Barnard, and Jones

in the open-sea assemblage. This scant comparability

casts doubt on the nomenclatural usefulness of designating communities by the names of their dominant

(standing crop) species, for these two assemblages of

Prionospio-dominated fauna have little in common.

The six most abundant San Quintin species, however,

occur in the open sea or have generic counterparts

there.

Hartman, Barnard, and Jones (1961) list 13 species

of polychaetes as characteristic indicators of inshore

sands of southern California; none of these occurs in

Bahia de San Quintin. Prionospio malmgreni is not

on the list, of course, because it occurs in environments other than inshore sands.

The frequency of individuals in the San Quintin

Prionospio community is nearly twice that in the open
16

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 8.—Rank and abundance of species in the Exogone ecotone: SQ 5, 25, 38, 64, 80

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

Name of species

Exogone verugcra

Prionospio malmgreni

rar»aiHf

Acuminodeutopus heteruropus

Rudilcmboidcs stenopropodus

Pistaalata

caprcllids

Eugyra glutinans

Scoloplos acmeceps

Ampelisca comprcasa

Chone T""H'*

Cossura Candida

Capitdla capitata

Neanthes caudata

Capitita ambiseta

ncmcrtcans

Microdeutopus schmitti

Mcgalomma pigmentum

Brania clavata

Listriclla mdauica

Oxyurostylis tertia

Lumbrineris irninima

enteropneusts

Parapboxus obtusidens

Ampbideutopus oculatus

nudibranchs

insect larvae

Cumella species

Amphipholis squamata

flatworm

Paranthura elegans

Lyonsia californica

Cirrifbnnia luxuriota

Fabricia limnicola

Ampithoe plumulosa

Monoculodes hartmanae

Paraphoxus heterocuspidatus

Elasmopus antennatus

Ampithoe pollcx

Orchomene magdalencnsis

Acteocina carinata

Nephtys caecoides

Scoloplos ohlini

holothurians

Corophium uenoi

Heterophoxus oculatus

Arenicola criitata

Nerinides maculata

Oxyurostylis pacifica

nebalian

Ericthonius brasiliensis

Total

2,538

800

645

467

322

334

246

237

227

166

164

149

140

110

63

54

51

45

43

42

41

32

34

35

21

18

15

11

10

10

9

9

9

9

8

8

8

7

6

6

6

6

6

6

2

2

2

2

2

2

1

Individuals

per square

meter

8,110

2,560

2,060

1,495

1,030

1,068

787

759

726

537

525

477

448

352

202

173

163

144

138

134

131

102

109

112

67

58

48

35

32

32

29

29

29

29

26

26

26

22

19

19

19

19

19

19

6

6

6

6

6

6

3

Pereentaee

total individuals

of study in

this community

25

14

75

21

11

35

16

3

16

1

32

4

60

14

2

9

5

12

19

13

12

9

7

4

3

35

73
NUMBER 44 17

TABLE 8.—Rank and abundance of species in the Exogone ecotone: SQ 5, 25, 38, 64, 80—

Continued

Rank

52

53

54

55

56

57

58

59

60

61

62

Name of species

Hippomedon dcnticulatus

Paraphoxus bicuspidatus

Uristcs entalladurus

Serolis carinata

Modiolus species

Solen rosaceus

Arabella iricolor

Axiotbella rubrocincta

Polydora punctata

Kalliapscudcs crassus

Callianassa species

Individuals

Total per square

meter

1 3

1 3

I 3

I 3

3

3

3

I 3

I 3

3

1 3

Percentage

total individuals

of study in

this community

sea. Only 2 of the 47 identified species occur in this

San Quintin community more than 50 percent of the

time, one of them having 73 percent and the other 54

percent of their lagoonal individuals confined to the

community.

The Eugyra-Ampelisca community of channels and

their margins is dominated by a pan-American amphipod from open-sea depths of 2-200 meters and a tunicate known heretofore primarily from subarctic regions

but also known to occur sporadically as far south as

Magdalena Bay (to the south of San Quintin). The

maximum density of Ampelisca compressa in the open

sea is 27 individuals per square meter in depths of

10-20 meters (average over scores of square miles).

In San Quintin the species is 500 times more abundant

in the channel community than in the open sea.

No community comparable to the Eugyra-Ampelisca

assemblage has been reported from the open sea, and

TABLE 9.—Sedimentary characteristics in communities of

Bahia de San Quintin (data quoted as median diameters in

microns)

it may be unique to lagoons having tidal rushes largely

confined to channels. Ten of the 80+ identified species

in the assemblage are more than 50 percent confined

to the community; indeed, five of them have 85 percent

or more of their individuals confined to this community. Lysianassa holmesi, with 99 percent of its individuals in the Ampelisca-Eugyra community is found

TABLE 10.—Most abundant animal species on inshore

sandy bottoms of southern California, by rank and abundance

{species also occurring in Bahia de San Quintin marked

with asterisks)

Community

Fabricia

Prionospio

Zostera

Ampelisca

Number

of samples

Range

of median

diameters

Median

of median

diameters

9

22

13

21

8-145

22-135

50-155

50-175

10

47

71

87

Rank

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Name of species

•Prionospio malmgreni P

Diastylopsis tenuis C

•Goniada littorea P

*Tellina buttoni M

Paraphoxus epistomus C

•Nephtys caecoides P

Chaetozone nr. spinosa P

Olivella species (including boetica) M

Mandibulophoxus uncirostratus C

•Haploscoloplos elongatus P

Dendraster species, juveniles E

•Paraphoxus bicuspidatus C

Photis lacia C

Scoloplos armiger P

Individuals

per square

meter

930

101

69

65

55

53

40

32

31

31

27

25

25

24

P=polychaete; C=crustacean; M = mollusk;E=echinodenn.
18 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

in the open sea in depths of about 10 to more than

200 meters, with maximum concentration of 11 individuals per square meter in a depth class of 75-92

meters.

Several open-sea Tellina communities have been described in various parts of the world (Thorson, 1957).

Apparently, the Prionospio community has little connection to those Tellina communities, for in southern

California, even though Tellina occurs in the Prionospio community, its abundance is reduced to less than

10 percent of that found in the Tellina-Nothria community and in San Quintin Tellina is apparently absent from the Prionospio community. On the other

hand, Tellina is strongly linked to the Eugyra-Ampelisca community, for 100 percent of the Tellina-contagious samples and 85 percent of all individuals

collected in San Quintin occur in that zone. In abundance, Tellina ranks only 34th in the Eugyra-Ampelisca

community, although its relatively large body size

brings it to high rank in standing crop values (probably

within the top 7, weights not taken). The abundance

of Tellina in the Ampelisca-Eugyra zone is only 15-30

percent of that found in the Tellina-Nothria community of the open sea. The occurrence of Tellina in San

Quintin suggests that the Eugyra-Ampelisca community may be an ecological equivalent to, or have a close

relationship with, the open-sea Tellina communities.

Interrelationships of Warm-Temperate Lagoons

Polychaeta, like Amphipoda, have a low proportion

of common denominators in the estuaries and lagoons

of California and Baja California (Reish, 1959, 1963,

Reish and Barnard, 1967) presumably because of latitudinal (thermal) differences, varying amounts of runoff and alterations by mankind. San Quintin shows

strongest relationship to Newport Bay but several dominant members of the San Quintin fauna have not

been recorded there (among polychaetes are Exogone

verugera, Onuphis microcephala, Scoloplos acmeceps,

and Prionospio malmgreni). San Quintin seems to

have a stronger affinity with the open sea in this sense

than does Newport Bay. A few common species in

coastal estuaries and lagoons from San Francisco Bay

or Morro Bay south to San Quintin among polychaetes,

for example, are Anaitides williamsi, Platynereis bicanaliculata, Stauronereis articulata, Haploscoloplos

pugettensis, Spiophanes missionensis, Armandia bioculata, Capitella capitata, and Axiothella rubrocincta,

but few of these are important dominants of lagoons.

Only 9 of the 13 most important species of San Quintin

occur in Newport Bay and only 6 of the 13 occur abundantly in the sublittoral of the open sea (as computed

from Hartman, 1966) of southern California. San

Quintin has more of the abundant Californian bay species than any other lagoon studied (18 of 21, see

Reish, 1963) and has four important species not in

other lagoons, thus lacking only Tharyx parvus and

Nereis procera, the two indicators of healthy bottoms in

Los Angeles Harbor (Reish, 1959).

Comparability of Eelgrass Community to the Phyllospadix Community of the Open-Sea Intertidal

The Zostera community is, to a large extent, a superimposition of a secondary substrate (the plant) upon

a primary sedimentary substrate. One might presume

that without the plant the substrate community would

resemble that of the Prionospio community because

many of the prionospionid members occur in the sediments on which the eelgrass grows. Those Prionospio

bottoms lacking eelgrass, however, must differ environmentally from those on which it does occur and one

would expect that the presence of eelgrass signals the

presence of organisms that would not occur on noneelgrass bottoms. This naturally applies to those animals occurring only on the living plant as well as some

normally occurring in the sediments and even others

that immigrate into climax Zostera communities because of (e.g.) the accumulation of waste products.

Figure 17 has been prepared in order to sort out

immigrant zosteral taxa. The major species of the

communities are arranged on either side of a base line

(0) and added cumulatively according to their frequency of individuals per square meter in the community. This gives an impression of the relative density of

organisms in each community and of which species

the assemblages are composed. The Prionospio community is the second most impoverished of the five

and placed near the middle as a base community.

Those species characteristic of the Ampelisca community are included above the base line, those of the Zostera community below. Only five major species besides

Zostera are absolutely characteristic of the eelgrass

community, those of the genera: Platynereis, Pontogeneia, Elasmopus, Hyale, and Ericthonius, all presumed to be oriented to the plant directly and not

necessarily to the original sedimentary substrate nor
NUMBER 44 19

to the substrate altered by the presence of Zostera.

Capitita ambiseta is partially characteristic of the Zostera community but also occurs in diminished numbers

in the Eugyra-Ampelisca community and of all major

lagoonal species appears to be the only one strongly

influenced by the development of organic oozes in the

channels and the eelgrass flats. The same may be true

of Fabricia limnicola on the bay margins near the

marsh flats, of the Scoloplos samples also near the bay

margins, and of the ubiquitous pollution indicator

Capitella capitata.

In the open sea a community comparable to that

of Zostera is the Phyllospadix zone of the lower intertidal. Both taxa are flowering plants and have a similar appearance. Phyllospadix, however, is a surfgrass

occurring in the heaviest zones of wave-dash. Unfortunately, the Californian Phyllospadix zone has not

been well studied; the fauna included in that zone is

adequately reported only by Hewatt (1946) and only

from the offshore Channel Islands, which undoubtedly

are biotopically distinct from continental shallows. Barnard (1969) has reported upon the amphipodan constituents of Phyllospadix zones from seven localities.

One of these, at Jolla, is compared in Table 11 with

the inhabitants of the Zostera community of San Quintin. Only 8 of the 24 important open-sea species occur

in San Quintin and only one of these, Hyale rubra

frequens, has rank equivalent to its open-sea frequency.

San Quintin species (of the 8) are either much less or

much more frequent in occurrence than in the open

sea. The open sea and lagoonal counterparts of marine

grasses thus have a fauna about as incongruous as the

open sea and lagoonal members of the Prionospio

fauna; the biotopes of the grasses, however, are more

strongly distinct than are the Prionospio and sublittoral

benthic zones because of the contrast between surf dash

and quiet water. Presumably the faunal members other

than Amphipoda differ from open-sea to lagoonal

environments as much as do Amphipoda. Only one

of the eight species of San Quintin is known to be

near its northern limit at La Jolla and therefore it

has a strongly different frequency in the open sea than

in lagoons because of zoogeographic reasons. That

species is Pontogeneia quinsana.

The Calm-Water Element

The bay-restricted, calm-water element in amphipodan

faunas of the Californias is poorly represented in Bahia

de San Quintin. Barnard (1961) identified six species

TABLE 11.—Important Amphipoda of the open-sea

Phyllospadix zone and the lagoonal Zostera community

(data from La Jolla, California, after Barnard, 1969)

Name of species

Hyale frequens

Ischyrocerus litotes

Elasmopus rapax serricatus

Photis brevipes

Photis conchicola

Elasmopus antennatus

Microdeutopus schmitti

Cerapus tubularis

Aoroides columbiae

Par aphoxus spinosus

Ericthonius brasiliensis

Amphilochus litoralis

Megamphopus effrenus

Jassa falcata

Megamphopus martesia

Ampithoe pollex

Cheiriphotis megacheles

Ampithoe plumulosa

Ischyrocerus species A

Amphilochus neapolitanus

Parapleustes pugettensis

Pontogeneia rostrata

Synchelidium rectipalmum

Pontogeneia quinsana

Total species in the faunules

Individuals per square meter

La Jolla

Phyllospadix

4,890

2,177

1,714

935

745

736

503

498

408

303

250

149

142

142

130

107

90

70

63

62

44

44

33

19

43

San Quintin

Zostera

2,950

—

—

—

—

360

33

—

9

—

9, 160

—

—

—

—

—

—

19

—

5

—

—

—

257

26

as members of this element: Corophium acherusicum,

C. insidiosum, Podocerus brasiliensis, (Jassa falcata),

Elasmopus rapax, and Ampithoe longimana. Since that

paper, Barnard (1969) has shown that Jassa falcata

is an abundant open-sea member of the intertidal

fauna, and that two forms of E. rapax are extremely

abundant in the open sea. The bay form of E. rapax,

however, remains recognizable as a bay-restricted

Pphenotype. The five bay-restricted species are extremely rare in the San Quintin fauna, possib'ly owing

to the absence of pilings. Probably all of them are

widely dispersed by means of ship foulings. The development of a remarkable phenotype of /. falcata in

open-sea California (Barnard, 1969) indicates the possibility that it is an immigrant to harbors and invaded

the open sea of California secondarily. Corophium

acherusicum is the eighteenth most abundant amphipod in San Quintin, whereas in harbors with pilings it
20

may rank first or second. Corophium insidiosum has

not been found in San Quintin; in nearby harbors it

is abundant in extremely polluted zones (or in brackish

waters). Podocerus brasitiensis and the bay form of

E. rapax have not been found in San Quintin.

Ampithoe longimana occurs sparsely in San Quintin,

but it also occurs sparsely in Newport Bay and is not

pollution-tolerant.

Bay and open-sea species, of higher frequency in

lagoons than in open seas, are Ericthonius brasiliensis,

Stenothoe valida, and Paraphoxus spinosus. The first

species is extremely abundant on harbor pilings and

in beds of eelgrass and in the open sea is of medium

rank (Table 11). Stenothoe valida is a common piledwelling species of Newport Bay but is of low frequency

in San Quintin. Paraphoxus spinosus is surprisingly

sparse in San Quintin if one considers its moderate

abundance in Newport Bay and that the bay is in

the middle of its eastern Pacific range; instead,

P. obtusidens, a closely related species not occurring

in Newport Bay, is dominant in San Quintin.

Two of the three Newport Bay, host-oriented commensal amphipods, Leucothoe alata and Leucothoides

pacifica, occur in San Quintin. Anamixis linsleyi apparently does not. Because of host protection these

species must be considered as belonging to a "calmwater" element.

Probably Corophium uenoi and C. baconi can be

added to the list of bay and open-sea forms, of higher

frequency in calm water than in surf. They are widely

distributed in the open sea of the North Pacific but

appear to occur in higher numerical frequency in bays

than in the open sea. Whether they have been dispersed

by ships or transplanted accidentally with commercial

marine organisms is open to question. Unlike their congeners, C. acherusicum and C. insidiosum, they have

not been recorded from seas other than the Pacific.

The so-called Pontogeneia minuta, now believed to

be distinct from the European types, has so far been

found only in Newport Bay and San Quintin and must

be considered a native calm-water element.

Thus, of 15 species identified in the Californias as

indicators of calm water, either by their presence or

their high frequencies in ponded water, the cosmopolitan forms associated with harbor pilings are poorly

represented in San Quintin (six species). Three native

species of epifaunas are well represented. Two native,

host-oriented species occur in San Quintin. One panAmerican burrower (Paraphoxus spinosus) is poorly

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

represented and another pan-American phycophilous

species (Ampithoe longimana) is normally represented. The final species, Ericthonius brasiliensis, is

ubiquitous and extremely abundant in San Quintin.

One must presume that the advent of commercial

development in San Quintin would change the balance

from native species to cosmopolitan species as it has in

Californian harbors.

Open-Sea Distribution of Major Lagoonal Taxa

None of the dominant taxa in the soft-bottom fauna of

San Quintin Bay is wholly confined to bays although

11 species of 46 in Table 12 are primarily lagoonal

inhabitants. These data concern only Polychaeta, Mollusca, and Amphipoda because the further distribution

of so many of the other groups (Isopoda, Tanaidacea,

Cumacea) is poorly known and still other groups are

very rare in Californian lagoons (e.g., Echinodermata).

Another 20 of the 46 species occur frequently in intertidal zones, another 15 in shallow water sands of the

open sea and only 6 species have their centers of abundance in water exceeding 11 meters in depth. More

than 85 percent of the dominant (high frequency)

species of San Quintin are either lagoonal forms or

have immigrated from shallow open-sea waters. If all

species, including so-called strays, were considered, a

very much lower percentage of the total probably

would be shown to have a shallow-water affinity. Unfortunately, the quantitative distribution of marine

invertebrates is poorly known and very little more can

be written about the zoogeography of the lagoon faunas

at this time.

Relationship of the Benthic Lagoonal Community

to Pollution Faunas

Presumably parts of San Diego Bay, Newport Bay,

Mission Bay, and Los Angeles Harbor, California,

resembled Bahia de San Quintin Bay in the days before

mankind altered them for maritime use. Some of those

harbors and others of smaller extent have been studied

by Reish (1955, 1959a, 1959b, 1961) and Reish and

Winter (1954). Los Angeles-Long Beach harbors have

been most extensively studied. Reish (1959b) found

five kinds of benthic assemblages, two of them called

semihealthy, one healthy, one polluted, and one very

polluted (azoic). Healthy bottoms are dominated by

Tharyx parvus, Cossura Candida, and Nereis procera;

semihealthy bottoms either by Polydora paucibran-
NUMBER 4 4 21

TABLE 12.—Distribution of abundant Polychaeta, Mollusca, and Amphipoda from Bahia de

San Quintin (primary habitats of each species marked with an "x"; geographic remarks

very abbreviated; "warm-temperate" refers only to Californias)

Names of species

POLYCHAETA

Armandia bioculata

Axiothella rubrocincta

Brania clavata

Capitclla capitata

Capitita ambiseta

Chone inollis

Cirriformia luxuriosa

Cossura Candida

Exogonc verugera

Fabricia limnicola

Haploscoloplos clongatus

Lutnbrineris minima

Megalomma pigmentum

Marphysa sanguinca

Ncanthcs caudata

Ncphtys caecoides

Nerinidcs maculata

Onuphis microccphala

Pista alata

Platynereis bicanaliculata

Prionospio malmgreni

Scoloplos acmeceps

Scoloplos ohlini

Scyphoproctus oculatus

MOLLUECA

Acquipccten circularis

aequisulcatus

Acteocina carinata

Crucibulum spinosum

Cryptomya californica

Hiatella arctica

Lasaea subviridis

Lyonsia californica

Marginella californica

Mitrella carinata

Ostrca lurida

Solcn rosaceus

Tellina buttoni

AMPHIPODA

Acuminodeutopus

heteruropus

Ampelisca comprcssa

Amphidcutopus oculatus

Ericthonius brasiliensis

Hyale frequcns

Lembos macromanus

Primarily

Bays

X

X

X

X

X

Intertidal

X

X

X

X

X

X

X

x (California)

X

X

X

X

X

X

% (kdpl

X

X

X

X

X

X

X

X

X

X

X

X

Open Sea {meters)

2-10

X

X

X

X

X

X

X

X

11-

30

X

x (kdp)

X

X

X

X

X

30-

100

X

Geography

warm-temperate

NE Pacific

cosmopolitan

cosmopolitan

warm-temperate

warm-temperate

warm-temperate

warm-temperate

cosmopolitan

warm-temperate

NE Pacific

warm-temperate bays

warm-temperate bays

cosmopolitan

cosmopolitan

NE Pacific

warm-temperate

tropical America

warm-temperate

Pacific

cosmopolitan

NE Pacific

E Pacific

warm-temperate

tropical-warmtemperate

tropical-warmtemperate

E Pacific

NE Pacific

arctic-tropical

warm-temperate

NE Pacific

warm-temperate

NE Pacific

NE Pacific

warm-temperate

NE Pacific

warm-temperate

pan-America

warm-temperate

cosmopolitan

warm-temperate

warm-temperate

362-694 O—70
2 2 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABLE 12.—Distribution of abundant Polychaeta, Mollusca, and Amphipoda from Bahia de

San Quintin (primary habitats of each species marked with an "x"; geographic remarks

very abbreviated; "warm-temperate" refers only to Galifornias)—Continued

Names of species

Lysianassa holmesi

Microdeutopus schmitti

Orchomcne raagdalcncnais

Paraphoxus obtusidcns

Primarily

Bays

Intertidal

Open Sea (meters)

2-10

X

X?

11-

30

X

30-

100

X

Geography

warm-temperate

warm-temperate

warm-temperate

N Pacific

chiata in combination with Dorvitlea articulata or by

Cirriformia luxuriosa; and polluted bottoms by Capitella capitata. All of these organisms are polychaetes.

Reish (1963 Table 4) in his analysis of the polychaetes

of San Quintin cites a number of species occurring in

several southern Californian bays and harbors of varying polluted conditions. Three major polychaetes do

not occur in San Quintin: Nereis procera, Prionospio

h. newportensis, and Tharyx parvus. That their absence from San Quintin proves that they are indicators

of polluted conditions in the harbors is disputed by the

presumption that they probably have their southern

limits in southern California and that they do not

extend as far south as San Quintin. Furthermore, San

Quintin has five major species of polychaetes not occurring as major dominants in the Californian harbors:

Exogone verugera, Scoloplos ohlini, S. acmeceps, Prionospio malmgreni, and Axiothella rubrocincta. A sixth

San Quintin species, Fabricia limnicola, occurs only in

Newport Bay, California, and not in two other harbors.

Only S. ohlini of the six taxa might be a southern species not occurring as far north as the California harbors; thus the absence of the others may be related to

factors of pollution. Fabricia limnicola apparently is a

warm-temperate, eastern Pacific bay taxon, reported

only from Newport Bay, Anaheim Slough, and San

Quintin; its absence in harbors also may be a factor of

artificial pollution, because in San Quintin the species

occurs in areas of fine sediment with high organic contents near marshes and must be existing under conditions of partial natural pollution. The same is true of

Scoloplos acmeceps.

Only Cossura Candida, of those polychaetes dominating the harbor healthy benthos, also occurs in San

Quintin; it is abundant in the eelgrass and Prionospio

communities.

Cirriformia luxuriosa, the harbor indicator of semihealthy bottom II has nearly 80 percent of its individuals in San Quintin Bay confined to the Prionospio

community (mostly Cossura phase). There it is abundant only in three samples.

Capitella capitata, the ubiquitous pollution indicator is probably also an indicator of any environmental

extreme that is limiting to other Metazoa. It occurs at

three stations in San Quintin, 25, 29, and 43; one of

these is a Prionospio bottom, another an Eugyra-Ampelisca bottom, and the third a Capitella-Scohplos

dominated bottom. Presumably the worm occurs in

these samples in a patch of environment, probably

putrid, restrictive to other organisms in the samples.

Benthic Amphipoda are nearly absent in polluted

harbors such as Los Angeles and Long Beach. The piling fauna is a different matter and was discussed previously; on pilings in those harbors, Amphipoda are

extremely abundant.

The benthic seaward portion of Newport Bay is

dominated by the Acuminodeutopus-Rudilemboides

amphipod association which in San Quintin is essentially an ecotonal area between Ampelisca-Eugyra and

Prionospio communities. In San Quintin the association is actually dominated in standing crop by Eugyra

glutinans and Prionospio malmgreni. Neither of those

species occurs in Newport Bay (or have not been detected in great abundance). The AcuminodeutopusRudilemboides samples of Newport Bay are dominated

in numbers by the polychaetes Capitita ambiseta, Cossura Candida, and Lumbrineris minima, but these are

of medium to low rank in San Quintin.
NUMBER 44

The Environment

Physiography and Sediments

Bahia de San Quintin is a Y-shaped tidal lagoon with

a single entrance at the foot of the Y. It is located at

approximately 30.5° N on the Pacific coast of Baja

California, about 255 kilometers south of the California borderline. The lagoon has a north-south orientation (Figures 13-14) which has been controlled by

the development of cinder cones on its northwest

perimeter and between the arms of the lagoon. The

east shore of the east arm is defined by a small escarpment which may represent a minor stage shoreline of

the open sea prior to or during volcanic activity and

uplift (or sea lowering) (but see Gorsline and Stewart,

1962). Spit dunes, one of which is a tambolo, form a

barrier to sea encroachment on the west and connect

low ground between the seaward cinder cones. The

arms of the lagoon are extremely shallow except for

narrow channels that rarely exceed 7 meters in depth.

More than 40 percent of the bay is believed to be exposed during tides lower than mean sea level. The bay

bottom, especially that in the east arm, which has been

studied more thoroughly than in the west arm, is

characterized by the elevation of small banks dominated by the eelgrass, Zostera marina L. Perhaps 20

percent of the bay bottom is covered with this flowering plant (Dawson, 1962). Marshes have encroached

on the water area in several places, but they are

severely controlled by the unusual topography of the

embayment.

The western arm of the bay has the characteristics

of a normal seaside lagoon in being separated from the

sea by a narrow spit of dunes and sand sheets and by

having its axis parallel to shore. The spit is abnormal

in the sense that it has been controlled by cinder cones

at either end, rather than having been formed merely

as a bar in reaction to changing sea levels. A few kilometers to the north of San Quintin are numerous temporary storm lagoons completely landlocked by dunes

and sand sheets, and one must presume that this

would have been the fate of the present bay except for

the impingement of the volcanics. Indeed, the subaerial

topography of the emergent coastal plain of Santa

Maria must have been extended considerably seaward

by the volcanics. The "central hills" (see fig. 2 in

Gorsline and Stewart, 1962), composed of extrusives,

probably formed a solid barrier to longshore sand

movements and controlled the development of sand

23

sheets and storm lagoons to the north of San Quintin.

Without the volcanics one would presume that the

present shoreline might occur approximately at the

small escarpment forming the mideastem margin of

the east arm. There is a remote possibility that this

escarpment (2-8 meters high) represents an old shoreline, but Gorsline and Stewart also imply that it may

have been cut by pluvial erosion, since they consider

the east arm to be a drowned estuary. The central

hills therefore blocked direct sea access to a major

arroyo during a wetter Holocene epoch, resulting in a

southward deflection of the channel, now represented

by the east arm.

That the embayment has not been completely filled

with sediment is of course a factor of time and climate.

But the aging of the seaward lagoon to some extent and

the landward relict estuary to a great extent may have

been lessened through protection afforded by the

peculiar topography.

The central volcanic peninsula has shielded the east

arm from north and westerly windblown sediments and

thus helped to control the survival of a deep channel.

The deep channel in the west arm fringes the west

margin of the central peninsula, thus indicating that a

great deal of the sediment filling the western ninetenths of the lagoon has come from the seaward dunes.

Perhaps the channel survives because it is bordered on

one side by "hard" rock contributing little sediment.

If the volcanics commenced subaqueously then baserock of the bay must have been deeper than in a

normal lagoon of a submergent coastal plain and if the

processes of aging (sedimentation) were normal, San

Quintin should have had a longer life than other aridclimate lagoons.

The east arm is not only longer than west but apparently far more complex. The diagram of sediment

distribution published by Gorsline and Stewart shows

a far greater complexity and patchiness to sediments

in the east arm than in the west (but the east was

studied more intensively than the west). The west arm

sediments grade regularly from sand to silt from southeast to northwest, the silt occurring just off the only

major plat of marshland in the northwest corner. That

marshland survives probably because of its protection

by the cinder cone known as Colina del Sudoeste,

whereas marshes on the lagoonal margin of the spit

are becoming inundated with sand. Essentially the west

arm has been filled with sediments coming from a single undirectional source and therefore a gradational

simplicity is to be expected. The near absence of
24

marshes on the east shore of the west arm is a function

of the elevated volcanic ground.

Even though sediments of the east arm are more diverse and patchy than in the west arm, the boundaries

between classes of sediments are not sharp. They appear sharp only because of the artificiality imposed by

drawing isopleths and other contours. Sediments of the

east arm presumably have multiple origins; some may

have been brought to the bay in the ancient estuary

during wetter climes and have been conserved to the

present by tidal reworking; more recent sediments presumably enter the bay rarely during floods of the main

arroyo and sheet flow over the escarpment; silts with

high organic content are related to marshes. The full

east shore of the east arm, except the margins of the

escarpment, is lined with marshes, some of them very

broad (cf. one half nautical mile wide). A lowland

drainage area between the two major cones of the

central peninsula is also dominated by a marsh on the

west shore of the east arm. The main channel probably

has been shifted westward since wetter climes as sheet

flow carried more sediments into the bay from the

plateau of the coastal plain than from the central

peninusla.

Interrelationships of Sediments and Biota

Except in the deep main channels, the upper 20 centimeters of sediment during field operations appeared

fairly uniform, presumably by homogenization through

biotic activities. Channel sediments are highly diverse

and undoubtedly strongly affected by animal populations. In some channel segments the substrate is medium to fine sand, in other segments the sand is overlain

by silt, and in the channel near the abandoned pier the

substrate is essentially pure slit as far as the sampler

could dig. Scouring of some of the channels may be

hindered by the presence of enormous numbers of

globular ascidians which would tend to impede saltation of coarse particles and thus contribute to deposition. Extraordinary numbers of ampeliscid Amphipoda,

building soft tubes on the substrate surface, also characterize some of the channels but presumably not those

in which the tidal rush is greatest because of the fragility of the tubes. The tunicate and the amphipod are

biotic partners of the overall channel community but

their codominance forms a spectrum, suggesting that

the ascidian occurs in greatest abundance in rapidly

flowing waters and the ampeliscid in greatest abunSMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

dance in fairly slow-moving water. The amphipod is

essentially a "filter feeder" on fairly coarse particles and

thus requires a certain minimal amount of water movement for food supply; it therefore does not occur in

abundance in completely ponded or very slow-moving

water. Few organisms occurring in the channels would

be considered as "sediment reworkers" (infauna) so

that one is left with the impression that channel filling

is being hastened by activities of organisms. This does

not account for the possibility of large organisms such

as elasmobranchs stirring up the bottom during

feeding.

There must be a very critical fulcrum of balance in

the channel environment between the factors of (1)

tidal rush impelling particles in an erosional-depositional cycle (2) the depositional influences of organisms essentially contributing to a self-destruction of

the environment. The maintenance of the channels in

this mature to senescent stage of the lagoon therefore

indicates that a fairly steady state is reached in the

evolution of the lagoon. The ascidians especially do

not live in extremely shallow, slow-moving waters so

that if deposition were to proceed to that level the

organisms would be removed from the picture and the

erosional part of the tidal rush would again scour

the channels to suitable biotopic conditions for the

tunicate. The organisms may well have contributed

to the overall filling of the bay through impedance

of erosion and once the water volume had been reduced

by increments, the deposition of the southern (eastwest) spit could proceed through dropping of sediment

load by decrease in tidal momentum. The east-west

spit now restricts the tidal rush to a relatively small

amount of water moving swiftly through the entrance

and into the channels and may be a major cause and

not necessarily the effect of the filling of the bay by

sediments. The open-sea hydrographic and topographic relationships to the east-west spit require study

before a measure of the balance between spit and bay

can be taken. The western (north-south) spit is presumed to be fairly stable and generally unaffected by

events inside the bay for it was originally controlled by

cinder cones.

In considering the maturation of the bay by filling

of a medium-depth sea bottom cut off by a northsouth spit and induced by volcanic activity (a

consideration antithetical to the drowning of the

coastal plain by change in sea level), one might recognize a stage between deep channelization and complete
NUMBER 44 25

shoaling. This biotope today is represented by mediumdepth flats between banks and channels and has an

impoverished fauna. If one could visualize a perfect

model of this bay there would be an assumption that

once the channel organisms had aided in the filling

of a simple deep channel to middepth flats, thereby

destroying their biotope, the subsequent stage of an

impoverished fauna would endure for a long period

of time until physically influenced deposition had built

the flats into shoals on which eelgrass could survive.

Eelgrass apparently requires a level of illumination

that would occur only in the upper few meters of a

highly turbid bay. The immigration of eelgrass would

then reaccelerate the deposition by trapping particles

and slowing water movement, but again it would help

to destroy its own biotope through filling the bay to

sea level. Meanwhile the lateral accretion of marshes

would continue to diminish the bay volume, the plants

again acting as sediment traps that would elevate

marsh surfaces to the upper limit of salt water.

The lagoonal characteristics of Morro Bay (Reish

and Barnard, 1967) and Newport Bay (Barnard and

Reish, 1959) seem to support parts of this model and

previous remarks on climate. The outer lagoon of

Newport Bay is represented by wide channels of middepth (4—5 meters) artificially induced by humans

through dredging and filling. Those channels have relatively even bottoms and are dominated by the impoverished Acuminodeutopus-Rudilemboides-Prionospio

community typical of middepth flats in San Quintin.

The marshes at Morro Bay are relatively more dominant to water area than they are in San Quintin; the

upper bay bottom is scarcely covered with water, has

seemingly little eelgrass and an impoverished fauna

with some similarities to that of Newport and San

Quintin. The main seaward channel of Morro Bay

is apparently dredged and composed of hard-packed,

biotically impoverished sand altered by the influences

of breakwater and human habitation. No channels with

ascidian-amphipod communities have been found in

Morro Bay. The enlarged marsh and almost completely filled inner lagoon suggest the influence of a

slightly wetter climate than in arid San Quintin, bringing into the bay more particles that were trapped by

former stands of marsh and eelgrass. Rainfall is apparently sufficient to carry many of the particles through

the marsh where presumably they have been trapped

by eelgrass and thus contributed to lagoonal senescence. There has also been a leveling of the inner

Morro lagoon through establishment of oyster farms.

A model of lagoonal maturation should therefore include a period of long stability through faunal impoverishment intercalated between the eelgrass and the

marsh stage. The sequence would then proceed as follows: (1) deep channels with high tidal volume

brought, through assistance of biota, to (2) middepth

flats with, faunal impoverishment and long-term stability, followed by (3) eelgrass dominated banks with an

increase in depositional rates, succeeded by (4) shoal

water, level and barren mud flats of long duration, on

which finally (5) marshes would encroach by lateral

immigration.

This simple model is complicated by the lack of any

reports on known broad-channel embayments with

high tidal volume in which stage 1 biota are known

to occur. The interpretation does suggest that San

Quintin Bay would have a. longer life than a lagoon in

a slightly wetter clime, and the model presupposes a

steady sea level which is contrary to the thesis of

Gorsline and Stewart that San Quintin, at least the

east arm, is a drowned estuary. In the drowned estuary

one could propose the occurrence of a broad and deep

river channel eventually dominated by tidal rush and

metasaline waters in which stage 1 biota could occur.

The relatively straight eastern escarpment and axis of

the east arm, deflected only by hard volcanic outcrops

suggest the ancient occurrence of a fairly heavy flow of

water that would have created a broad channel with

few meanders. A low-gradient stream with heavy sediment load and strong meanders would provide an

environment already suitable for stage 3 biota.

If coastal plain submergence took place after an

increase in aridity then the broad river valley, ergo

estuary, would already have a sediment load and meandering channels. Channelization would then be

maintained only by tidal rush and subshoal banks

would be available for immediate implantation of eelgrass. A submerged estuary in an arid climate would

therefore already be mature whereas a lagoon, formed

immediately after stability of sea level through simple

deposition of offshore bars and their rapid evolution

into a spit, might have a longer life. This longer life

would be controlled by storms, prevailing winds, aridity, specific composition of the spit sediments, activities

of terrestrial organisms on the bar, groundwater, and a

host of other factors.

Relatively rapid changes apparently occur in Sonoran lagoons of the northeast Pacific, for Gorsline and

Stewart show the considerable changes known to have
26 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

occurred in the erosional-depositional cycle near the

tambolo of San Quintin since 1886, and Stevenson and

Emery (1958) trace the extensive changes that have

occurred in Newport Bay since 1825. The changes at

Newport are so extensive as to suggest significant uplift

in the last 200 years, but the changes shown by Gorsline

and Stewart at San Quintin appear to be oscillatory.

Climate of Air and Water

Climate not only influences the thermal boundaries of

the biogeographic province in which San Quintin

occurs but it has topical effects The very low rainfall

and presumedly moderate evaporation result in slightly

hypersaline lagoonal water and very little continuous

sedimentation. The extremely rare occurrence of pluvial sheet-flow must create catastrophic conditions from

time to time, not only in diluting seawater but by roiling

the water and superimposing fresh sediments. The absence of fluvial sedimentation has presumably afforded

a longer life to the lagoonal environment than if the bay

had occurred in wetter climes but Gorsline and Stewart

believe that San Quintin did at one time exist in a

wetter clime and that the east arm is a drowned estuary.

A sediment load would already be present under those

circumstances. Further discussion must concern present-day water conditions.

Hydroclimatic conditions of Bahia de San Quintin

are less extreme than we had expected to encounter

(Figure 16). In comparison with Laguna Ojo de

Liebre, 315 kilometers to the south of San Quintin

(Phleger and Ewing, 1962), San Quintin is colder and

less hypersaline. If the years 1956-57 for Ojo de Liebre

and 1960-61 for San Quintin can legitimately be compared, one can state that in November the bays have

similar thermal conditions (20° C temperature at the

heads of the bays) but in February Ojo de Liebre is

still 20° whereas San Quintin has dropped to 16.0-

16.5° C. In August the head of San Quintin has

warmed to 24.4-24.7° whereas the waters in Ojo de

Liebre are in excess of 26° C. Presumably much of

this summer difference can be explained by the warmer

water of the inshore open sea off Ojo de Liebre and

the winter difference by upwelling in the inshore open

sea of San Quintin (Dawson, 1951), a condition not

likely to occur at Ojo de Liebre because of its situation

in the large Gulf of Sebastian Viscaino. In either bay,

therefore, a considerable influence is felt from open-sea

conditions. The smaller San Quintin is affected more

strongly and immediately by the open sea than is Ojo

de Liebre. Fog and overcast, especially in early morning

hours, ameliorate thermal extremes of air and water

in both San Quintin and Ojo de Liebre.

Avian Predators

Four or five species of shore birds (dowitchers, godwits,

sandpipers) prey extensively on polychaetes, frequently

on amphipods and other small crustaceans and rarely

on mollusks and crabs (juvenile crabs or legs of adults).

Stomachs of about 100 birds have been processed and

await final analysis; the only comment that can be

made at this time is that during periods of favorable

low water a few days a month the birds take enormous

numbers of polychaetes and crustaceans. Birds that had

been feeding on mud flats during negative tides and

killed two hours after sunrise had frequently consumed

between 50 and 100 individuals of the common amphipods and polychaetes, primarily in the Zostera zone or

on barren banks in shallower depths. A minimum of

5,000 shorebirds in feeding behavior during a low tide

has been counted in one day. These very minimal numbers indicate a prodigious effect rendered on the invertebrate fauna even if maximal feeding is confined

to 25 days per year and only on the shallowest of the

banks. Other than elasmobranchs, piscine predators on

small invertebrates seem to be insignificant; only the

local needlefish consumes neritic copepods whereas

numerous other species of fish had few invertebrates in

their stomachs. Many bottom-feeding elasmobranchs

occur in San Quintin Bay but most of those we autopsied had empty stomachs. Bony fish stomach contents

await further study.

Conclusions

Few estuaries or lagoons fit a simple model. The physiographic control of the San Quintin lagoon is highly

abnormal but the results fit, to a large extent, the concept of a lagoon, if stringently defined (Emery, Stevenson, Hedgpeth, 1957). San Quintin is thus a shallow,

semienclosed body of slightly hypersaline sea water.

Its axes are parallel to the sea margin but at least in

the case of the east arm, the axis is directly controlled

by solid volcanics whereas the west arm is normally

controlled by a spit, although the spit is an abnormal

corollary of volcanic extrusions to the north and the

south. San Quintin therefore resembles other Califor-
NUMBER 44

nian lagoons which are bipartitely extinct river valleys

and seaside lagoons, but the axis of the San Quintin

stream valley has been deflected to parallel the sea

margin. There is some indication that floods of rare

rainstorms are channeled into shallow arroyos debouching into the upper end of the east arm in San Quintin,

but this kind of erosion did not control the basic structure that came during a wetter clime in the past. Spits

evolved from bars characterize some of the Californian

lagoons (Newport), but solid intrusives and rock faulting obviously control others (San Diego Bay). Regardless of the controlling geomorph the results in the Sonoran northeastern Pacific have been the same; the

development of ponded waters open to tidal rush, with

evaporative-precipitative balance affording slight hypersalinity. San Quintin differs from lagoons to the

north but not to the south in the presence of deeply

cut channels far from the mouth and these are probably maintained in part by the hard precipitous volcanic ground. The east arm but not the west is protected completely from effects of storm waves and

windblown sediments which so often are major components controlling the physiography and water content of lagoons.

Like most estuaries the level of dissolved phosphate

and silicate is high toward the inner reaches of San

Quintin, but this high level of nutrient salts cannot

be explained by the loading effect of rivers (Stevenson, Emery, Hedgpeth, 1957). High levels of nutrients

seem to be associated with those parts of the lagoon

fringed by dense marshes. Concentration of nutrients

may be assisted by avian and piscine predation altering the biomass-nutrient balance common in the open

sea to a level with nutrients dominating. In other

words the exposable bay margins may not support a

potentially maximal biomass density consistent with

available nutrients because of predatory effects. A

short-term increase in standing crop would probably

result from civilizing influences resulting in removal of

the avian predators, but those human influences then

might implement the new level by increasing nutrient

disposal through domestic outfalls, followed by ultimate decrease of standing crop through introduction

of lethal pollutants.

The east arm of Bahia de San Quintin might be

visualized as a perfectly flat bottom dominated by a

highly restricted invasive Prionospio community with

low standing crop, low diversity, and low frequency

of organisms, on which has been imposed the follow27

ing modifications that in most cases increase the diversity, abundance, and standing crop of organisms:

(1) the incision of channels into which are directed

most of the tidal waters and in which are received

most of the sedimented debris and detritus that is reworked by the Eugyra-Ampelisca community; (2) the

development of eelgrass beds on suitably elevated

banks that come to climactical perfection by self-generation of debris and detritus sedimented because of water-ponding by the eelgrass; (3) peripheral low-grade

sedimentation bringing the bay margins to a peneplane

level on which marsh plants by particle entrapment

also evolve to climax and ultimate destruction through

subaerial elevation but that meanwhile contribute certain components of the underwater Fabricia biotope.

The sharp definition of the eelgrass community from

the purely sedimentary surroundings attests to the importance of an epifaunal substrate provided to a few

organisms that would otherwise probably not occur in

lagoons except where humans have constructed artificial substrates such as pilings and floating docks.

The eelgrass community is matched in the open sea

only by wave-dashed Phyllospadix stands while the

channel community and Fabricia zone have no opensea counterparts. The biota of the channel community

consists of invaders from the open sea thrown together

in unique combination; the basic Prionospio community is dominated by a strong open-sea taxon while

the Fabricia zone is dominated by a lagoonal species

and the Zostera community has as its basic member a

lagoonal evolute. But the zosteral associates comprise

strong open-sea species in combination with a few

species primarily restricted to lagoons. The channel,

zosteral, and marsh communities are presumably very

sensitive to depth or water-volume and momentum

changes made by humans; the Fabricia community,

however, may survive under certain artificial conditions of pollution, while a few of the dominant zosteral foulers will survive on artificial substrates.

No important zoological effect of an axial gradient

in environmental conditions is seen in Bahia de San

Quintin, although water quality differs recognizably

between the open mouth and the head of the bay (Figure 16). Apparently the special domination of the upper end of the bay by Fabricia is simply a positive

relationship to the increased ratio of marsh to water

volume, because a weak Fabricia community occurs

adjacent to marshes in the outer bay, and bottoms next

to precipitous volcanics in the upper bay are barren of
28

Fabricia. A few rarely occurring members of the biota

such as Kalliapseudes may reflect other special conditions in the reaches, but these correlations have not

been elucidated because they require intense study of

very small areas of bottom.

An extraordinary relationship between climate and

physiography is demonstrated in the present-day condition of San Quintin Bay. The effects of the two

groups of conditions are so inextricably mixed in the

resultant bay structure that one must suggest the

ultimate understanding of these effects will come from

large-scale experimental models.

In an area of regional uplit or heavy sedimentation

the fate of San Quintin would be a filled marsh with

a frontage of sand beaches possibly like that at Anaheim Slough, California. Even in a geostrophic steady

state the process of filling the bay with sediments occurs from windblown western dunes and the rare occurrence of freshwater runoff.

Sea-farm management of San Quintin could be accomplished by experimentation in dredging, excavation, and landfill so as to increase the undersea area

covered by either Zostera banks or channel communities, balancing both extremes so that the necessary rush

of water feeding the channel communities is carried in

suitable proportion to zosteral banks, thus eliminating

unproductive middepth or supralittoral banks. Presumably creation of additional marshes by landward

excavation would provide an increase in the photosynthetic base to supply debris and detritus to the

undersea flats. An enlarged water volume would have

to be considered. Ponds with artificial vertical surfaces

to attract fouling organisms could increase the production of protoplasm in such a system. Apparently

the simple dumping of shells on the bottom would not

result in an increase of favorable surface, for the shelly

bottoms of upper Newport Bay are very barren. The

basic product of such a system would be powdered protein or cellulose with various byproducts. Because the

lagoons of the Califomias are predictably vulnerable to

destruction by human habitation San Quintin in its

present primeval condition would make an idealistic

sea-farm community experiment In the process of its

ideal development a reserve of supralittoral banks for

preservation of wildfowl and marine communities

could be incorporated, and recreational areas developed that would not hinder the productivity. Human

effluvia from the recreational area could be contributed

to the nutrient base.

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

The natural beauty and relatively benign climate

of San Quintin, would, under circumstances affording

cheap fresh water, result in a dense human population

that would frustrate massive reclamation for sea

farming and conservation that is unfeasible for lagoons

such as Newport and San Diego because of proprietary

rights. To protect San Quintin from the ugly fate of

the other lagoons the timing of its development must

anticipate cheap fresh water and retard the importation of deleterious industries—the ultimate ideal, of

course, would be the complete protection of San Quintin, the removal of its few humans to suitable employment elsewhere, and the reintroduction of the marine

turtle that used to function as a top herbivore in this

system.

Acknowledgments

The fieldwork for this study was supported under

grants NSF-G 11413 and 16170 to the Beaudette

Foundation of California from the National Science

Foundation, for which grateful acknowledgement is

made (and see Barnard, 1962, 1964). Since 1964 the

Smithsonian Institution has supported the continuity

of this project and among many persons who have lent

their support I must give special thanks to Dr. Meredith L. Jones, Dr. D. F. Squires, Dr. I. E. Wallen, Dr.

R. B. Manning, and Dr. Richard S. Cowan. Mrs. Carolyn B. Gast prepared the illustrations.

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Appendix I

Contagious species in each benthic sample from Bahia

de San Quintin, printed in lower case Roman type. If

italicized, these names also represent standing-crop

dominants. Capitalized names represent standing-crop

dominants that are not in contagious frequencies.

Names in parentheses represent secondary crop dominants.

Station number

1. Acteocina carinata, PRIONOSPIO MALMGRENI, (FABRICIALIMNICOLA).

2. Acteocina carinata, FABRICIA LIMNICOLA.

3. Exogone verugera, Fabricia limnicola, Scoloplos

ohlini, Acteocina carinata.

4. Exogone verugera, Acteocina carinata, FABRICIA LIMNICOLA.

5. Exogone verugera, Fabricia limnicola.

6. Fabricia limnicola.

7. None.

8. PRIONOSPIO MALMGRENI.

9. Prionospio malmgreni, Cossura Candida.

10. Neanthes caudata, Scyphoproctus oculatus, MARPHYSA SANGUINEA, KALLIAPSEUDES

CRASSUS.

11. PRIONOSPIO MALMGRENI.

12. Prionospio malmgreni, Scoloplos acmeceps, Scyphoproctus oculatus, Acteocina carinata, Acuminodeutopus heteruropus, Ampelisca compressa,

Axiothella rubrocincta, Chone mollis, Paranthura

elegans, Paraphoxus obtusidens, EUGYRA GLUTINANS, KALLIAPSEUDES CRASSUS

13. Exogone verugera, Kalliapseudes crassus, Ampelisca compressa, Listriella melanica, Orchomene

magdalenensis, Paranthura elegans, Paraphoxus

obtusidens, (MARPHYSA SANGUINEA).

14. Prionospio malmgreni.

15. Scoloplos acmeceps, Scyphoproctus oculatus, Acteocina carinata, Acuminodeutopus heteruropus,

Ampelisca compressa, Paranthura elegans, Paraphoxus obtusidens, Scoloplos ohlini, EUGYRA

GLUTINANS.

16. Prionospio malmgreni.

17. Prionospio malmgreni, COSSURA CANDIDA.

18. Prionospio malmgreni, Scoloplos acmeceps, Axiothella, rubrocincta, Megalomma pigmentum,

Paranthura elegans, Paraphoxus obtusidens, EUGYRA GLUTINANS, AMPELISCA COMPRESSA.

19. Prionospio malmgreni, Scoloplos acmeceps.

20. Acuminodeutopus heteruropus, Paraphoxus obtusidens, EUGYRA GLUTINANS, PRIONOSPIO MALMGRENI.

21. Scoloplos ohlini, (PRIONOSPIO MALMGRENI).

22. None.

23. Prionospio malmgreni, Cossura Candida, Pista

alata.

24. Megalomma pigmentum, PRIONOSPIO MALMGRENI.

25. Exogone verugera, Scoloplos acmeceps, Acuminodeutopus heteruropus, Neanthes caudata, Paraphoxus obtusidens, CAPITELLA CAPITATA.

26. Cirriformia luxuriosa, Cossura Candida, Prionospio

malmgreni.

27. Scoloplos acmeceps, Scoloplos ohlini, PRIONOSPIO MALMGRENI.

28. Exogone verugera, Kalliapseudes crassus, Listriella melanica, Lumbrineris minima, Orchomene

magdalenensis, Paranthura elegans.

29. Cirriformia luxuriosa, Prionospio malmgreni, Listriella melanica, Neanthes caudata, Scoloplos

ohlini.

30. (MARPHYSA SANGUINEA).

31. None.

32. Lumbrineris minima, Pista alata, Scoloplos ohlini,

Scyphoproctus oculatus.

33. Fabricia limnicola, Acuminodeutopus heteruropus,

Brania clavata, PRIONOSPIO MALMGRENI.

34. Capitita ambiseta, Corophium baconi, Ericthonius

brasiliensis, Exogone verugera, Pista alata, Platynereis bicanaliculata.

35. Eugyra glutinans, Fabricia limnicola, (Prionospio

malmgreni), Acuminodeutopus heteruropus, Amphideutopus oculatus, Axiothella rubrocincta,

30
NUMBER 44 31

Cossura Candida, Listriella melanica, Lumbrineris

minima, Megalomma pigmentum, Pista alata, Paraphoxus obtusidens, Rudilemboides stenopropodus.

36. Prionospio malmgreni, Brania clavata, Cirriformia

luxuriosa, Neanthes caudata, Scolopos acmeceps.

37. Prionospio malmgreni, (Cossura Candida).

38. (Cossura Candida), (Pista alata), (Prionospio

malmgreni), Acuminodeutopus heteruropus,

Brania clavata, Chone mollis, Cirriformia luxuriosa, Exogone verugera, Listriella melanica, Lumbrineris minima, Megalomma pigmentum, Neanthes caudata, Rudilemboides stenopropodus,

Scoloplos acmeceps.

39. Chone mollis, (Lumbrineris minima), (Scoloplos

acmeceps), Capitita ambiseta, Cossura Candida,

Megalomma pigmentum, Pista alata, PRIONOSPIO MALMGRENI.

40. (Scoloplos acmeceps), Paraphoxus obtusidens.

41. Prionospio malmgreni, (Neanthes caudata), Cossura Candida.

42. Prionospio malmgreni, (Fabricia limnicola),

Brania clavata.

43. Eugyra glutinans, Megalomma pigmentum, Acuminodeutopus heteruropus, Amphideutopus oculatus, Brania clavata, Exogone verugera, Microdeutopus schmitti, Paraphoxus obtusidens, Pista

alata, Rudilemboides stenopropodus, (PRIONOSPIO MALMGRENI).

44. Eugyra glutinans, (Pista alata), Acteocina carinata, Acuminodeutopus heteruropus, Ampelisca

compressa, Amphideutopus oculatus, Axiothella

rubrocincta, Corophium baconi, Lembos macromanus, Listriella melanica, Lumbrineris minima,

Microdeutopus schmitti, Orchomene magdalenensis, Paraphoxus obtusidens, Rudilemboides stenopropodus, Tellina buttoni, Uristes entalladurus,

COSSURA CANDIDA.

45. Acuminodeutopus heteruropus, Brania clavata,

Cossura Candida, Megalomma pigmentum.

PRIONOSPIO MALMGRENI.

46. Acuminodeutopus heteruropus, Paraphoxus obtusidens, EUGYRA GLUTINANS, (COSSURA

CANDIDA), (PRIONOSPIO MALMGRENI).

47. Onuphis microcephala, Prionospio malmgreni,

(Scoloplos acmeceps), Paraphoxus obtusidens.

48. Amphideutopus oculatus, Lumbrineris minima,

Paraphoxus obtusidens, Uristes entalladurus,

EUGYRA GLUTINANS.

49. Prionospio malmgreni, Acuminodeutopus heteruropus, Brania clavata, Chone mollis.

50. (PRIONOSPIO MALMGRENI), EUGYRA

GLUTINANS.

51. Eugyra glutinans, (Cirriformia luxuriosa),

(Prionospio malmgreni), Acuminodeutopus heteruropus, Axiothella rubrocincta, Megalomma pigmentum, Neanthes caudata, Paraphoxus obtusidens, Scyphoproctus oculatus.

52. (Chone mollis), (Lumbrineris minima), EUGYRA GLUTINANS).

53. Capitita ambiseta, (Prionospio malmgreni), Hyale

frequens, Listriella melanica, Platynereis bicanaliculata, Pontogeneia quinsana, (EXOGONE VERUGERA) .

54. (Cossura Candida), Chone mollis, Exogone verugera, Listriella melanica, Pista alata, Scoloplos

ohlini, (FABRICIA LIMNICOLA), (PRIONOSPIO MALMGRENI), EUGYRA GLUTINANS.

55. Scoloplos acmeceps.

56. (EUGYRA GLUTINANS).

57. None.

58. Prionospio malmgreni, Brania clavata, Scoloplos

ohlini, COSSURA CANDIDA.

59. Acteocina carinata.

60. Chone mollis, Eugyra glutinans, (Pista alata),

Acuminodeutopus heteruropus, Amphideutopus

oculatus, Axiothella rubrocincta, Listriella melanica, Megalomma pigmentum, Microdeutopus

schmitti, Prionospio malmgreni, Rudilemboides

stenopropodus, Scoloplos acmeceps.

61. Capitita ambiseta, Pista alata, Prionospio malmgreni, Corophium baconi, Cossura Candida, Elasmopus rapax, Ericthonius brasiliensis, Exogone

verugera, Hyale frequens, Lembos macromanus,

Listriella melanica, Lumbrineris minima, Orchomene magdalenensis, Platynereis bicanaliculata,

Pontogeneia quinsana, Scoloplos acmeceps.

62. Capitita ambiseta, (Prionospio malmgreni), Cossura Candida, Elasmopus rapax, Ericthonius brasiliensis, Exogone verugera, Hyale frequens, Lembos

macromanus, Listriella melanica, Orchomene

magdalenensis, Pista alata, Platynereis bicanaliculata, Pontogeneia quinsana, Rudilemboides

stenopropodus, Scoloplos ohlini.

63. Scoloplos acmeceps.

64. Eugyra glutinans, Pista alata, Prionospio malmgreni, Scoloplos acmeceps, Acuminodeutopus
32 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

heteruropus, Brania clavata, Ghone mollis, Exogone verugera, Listriella melanica, Megalomma

pigmentum, Microdeutopus schmitti, Neanthes

caudata, Rudilemboides stenopropodus.

65. Eugyra glutinans, (Capitata ambiseta), (Chone

mollis), Acuminodeutopus heteruropus, Ampelisca

compressa, Amphideutopus oculatus, Megalomma

pigmentum, Microdeutopus schmitti, Paraphoxus

obtusidens, Rudilemboides stenopropodus, Uristes

entalladurus.

66. Chone mollis, Cossura Candida, Megalomma pigmentum, Prionospio malmgreni, Acuminodeutopus heteruropus, Capitata ambiseta, Corophium

baconi, Ericthonius brasiliensis, Hyale frequens,

Lembos macromanus, Listriella melanica, Neanthes caudata, Onuphis microcephala, Pista alata,

Pontogeneia quinsana, Rudilemboides stenopropodus, Scoloplos acmeceps.

67. Eugyra glutinans, Acteocina carinata, Acuminodeutopus heteruropus, Axiothella rubrocincta,

Microdeutopus schmitti, Rudilemboides stenopropodus, PRIONOSPIO MALMGRENI,

(SCOLOPLOS ACMECEPS).

68. (Scoloplos acmeceps), Acteocina carinata, Paraphoxus obtusidens.

69. Eugyra glutinans, (Chone mollis), (Lumbrineris

minima), Ampelisca compressa, Axiothella rubrocincta, Brania clavata, Capitita ambiseta, Corophium baconi, Lysianassa holmesi, Orchomene

magdalenensis, Paranthura elegans, Paraphoxus

obtusidens, Rudilemboides stenopropodus, Uristes

entalladurus.

70. Capitita ambiseta, (Cossura Candida), Elasmopus

rapax, Ericthonius brasiliensis, Hyale frequens,

Lembos macromanus, Listriella melanica, Orchomene magdalenensis.

71. Prionospio malmgreni, (Scoloplos acmeceps).

72. None.

73. Eugyra glutinans, Ampelisca compressa.

74. Neanthes caudata, Acuminodeutopus heteruropus,

Axiothella rubrocincta, Corophium baconi, Elasmopus rapax, Hyale frequens, Scoloplos acmeceps,

Scoloplos ohlini.

75. None.

76. Eugyra glutinans, (Neanthes caudata), Scoloplo*

acmeceps, Acuminodeutopus heteruropus, Axiothella rubrocincta, Brania clavata, Cossura Candida, Onuphis microcephala.

77. Eugyra glutinans, (Capitita ambiseta), (Megalomma pigmentum), Amphideutopus oculatus,

Lembos macromanus, Pista alata, Rudilemboides

stenopropodus.

78. Ampelisca compressa, Corophium baconi, Microdeutopus schmitti, Orchomene magdalenensis,

Rudilemboides stenopropodus.

79. Platynereis bicanaliculata, Capitita ambiseta, Elasmopus rapax, Ericthonius brasiliensis, Exogone

verugera, Hyale frequens, Lembos macromanus.

80. (Exogone verugera), Acteocina carinata.

81. Pista alata, (Capitita ambiseta), Corophium

baconi, Cossura Candida, Elasmopus rapax, Ericthonius brasiliensis, Exogone verugera, Hyale frequens, Listriella melanica, Neanthes caudata, Onuphis microcephala, Platynereis bicanaliculata,

Pontogeneia quinsana, Scoloplos ohlini.

82. No sample.

83. Platynereis bicanaliculata, Rudilemboides stenopropodus, Tellina buttoni.

84. (Scoloplos acmeceps), Acteocina carinata.

85. (Chone mollis), (Neanthes caudata), Axiothella

rubrocincta, Megalomma pigmentum, Pontogeneia quinsana, Scoloplos ohlini, Scyphoproctus

oculatus.

86. None.

87. Pista alata, (Cossura Candida), Capitita ambiseta,

Elasmopus rapax, Hyale frequens, Lembos macromanus, Lumbrineris minima, Neanthes caudata,

Megalomma pigmentum, Orchomene magdalenensis, Pontogeneia quinsana.

88. (Scoloplos acmeceps), Acteocina carinata, Megalomma pigmentum.

89. (Capitita ambiseta), (Cossura Candida), Corophium baconi, Hyale frequens, Lembos macromanus, PRIONOSPIO MALMGRENI.

90. Scoloplos acmeceps, (Fabricia limnicola), (Neanthes caudata), Acuminodeutopus heteruropus,

Axiothella rubrocincta, Chone mollis, Lembos

macromanus, Onuphis microcephala, Scoloplos

ohlini.

91. Scoloplos ohlini, (Neanthes caudata), (FABRICIA LIMNICOLA).
Appendix II

List of miscellaneous species and phyla identified from

San Quintin samples. Names of Amphipoda (Barnard,

1964), Polychaeta (Reish, 1963), Mollusca (Keen,

1962), and Isopoda (Menzies, 1962) are listed in

Appendix III for convenience of readers unfamiliar

with names mentioned in text. Ophiuroids have been

identified by Capt. F. C. Ziesenhenne, Cumacea by

Mr. R. R. Given, and various worm phyla sorted by

Dr. D. J. Reish. The ascidian, Eugyra glutinans has

been identified by Dr. D. P. Abbott.

Turbellaria: SQ 12 (1), 25 (1), 34 (1), 38 (6),

43 (2), 51 (1),53 (1),64 ( + ),66(1),6 7 (4), 69

(10), 76(1), 77(1), 81 (4).

Sipunculida: SQ 13 (20), 28 (83), 30 (10).

Phoronidea: SQ 26 (21).

Nemertea: SQ 1 (1), 2 (1), 4 (5), 5 (3), 7 (2),

9 (3), 10 (1), 12 (1), 13 (63), 14 (5), 15 (20), 17

(2), 20 (2), 23 (7), 24 (2), 25 (8), 26 (4), 27 (4),

30 (2), 31 (40), 34 (12), 35 (11), 36 (11), 37 (7),

38 (27), 39 (9), 40 (4), 43 (9), 44 (30), 47 (4), 48

(5), 51 (9), 52 (2),53 (11),58 (4),59 (4),60 (17),

62(12),64(13),65(9),66(4),67 (67) sic, 69 (10),

71 (2), 72 (1), 73 (4), 74 (5), 76 (25), 77 (12), 79

(12),81 (4), 84 (3), 85(1), 88(1),89 (8),90 (13),

91 (10).

Oligochaeta: R = rare (1-10), S= sparse (10-20),

G= significant (20-50), A= abundant (50-100),

V— very abundant (100+), individuals often fragmented and counted mainly by estimate: SQ 0 (R),

1 (A), 2 (S), 3 (S), 5 (V), 6 (A), 7 (G), 8 (A), 9

(A), 10 (A), 11 (G), 12 (R), 13 (V), 14 (G), 15

(G), 16 (G), 17 (G), 18 (R), 19 (A), 20 (G), 22

(R), 23 (V), 24 (R), 25 (R), 26 (V), 27 (R), 30

(G), 31 (S), 32 (S), 35 (G), 36 (G), 37 (G),

38 (G), 39 (A), 40 (R), 41 (G), 42 (G), 43 (V),

44 (R), 45 (R), 46 (S), 47 (A), 49 (A), 50 (G),

51 (G), 53 (R), 54 (G), 58 (G), 60 (G), 63 (R),

64 (A), 66 (R), 68 (R), 72 (R), 74 (R), 75 (R), 76

(G),79(R),81(R),84(R),85(R),88(S),90(R).

Crustacea:

Tanaidacea:

Kalliapseudes crassus: SQ 10 (68), 12 (71), 13

(8580), 15 (25), 18 (4), 22 (2), 24 (2), 25 (1),

28 (1632), 30 (4), 43 (1), 65 (1).

Othe r tanaids: SQ 1 (2), 2 (8), 4 (82), 5 (640),

6 (13), 7 (17), 8 (3), 12 (19), 13 (40), 15 (1), 25

(2), 38 (3), 55 (1), 60 (3), 65 (1), 67 (3), 74 (8),

87 (5).

Decapoda, shrimp, Callianassa spp.: SQ 14 (1),

16 (1), 19 (2 + 60 larvae), 23 (1), 27 (1), 28 (1),

29 (9), 30(1) , 41(1),51(1),52(1),64(1),65(1) .

Othe r shrimp: SQ 65 (1),7 7 (1), 79 (21), 81 (1).

Mysidacea: S Q 60 (1).

Brachyura: S Q 61 (1), 70 (2), 72 (2).

Cumacea:

Oxyurostylis tertia: S Q 10 (1), 14 (1), 17 (2), 18

(57), 20 (10), 25 (10), 33 (20), 35 (29), 36 (1),

37 (3), 38 (3), 40 (1), 43 (7), 44 (21), 45 (3), 46

(14), 47 (12), 48 (1), 51 (28), 53 (1), 60 (14), 61

(3), 64 (24), 65 (25), 66 (1), 67 (1), 69 (10),

74 (1), 76 (7), 77 (13), 88 (1).

Oxyurostylis pacific a: S Q 12 (1) , 17 (1) , 2 0 (1) ,

33 (10), 55 (3), 65 (3), 68 (7), 71 (2), 76 (1), 80

(2), 84 (8), 91 (4).

Oxyurostylis sp.: SQ 12 (1), 61 (3), 67 (1).

Cumella sp.: SQ 9 (1), 35 (1), 51 (1), 64 (1),

65 (1), 74(1) , 76 (4), 85 (4), 87 (1).

Other Cumacea: SQ 15 (5), 25 (1), 38 (3), 48

(1), 51 (2), 60 (2), 64 (1), 65 (1), 76 (1), 77 (1),

90 (1).

Ostracoda: SQ 1 (80), 2 (16), 3 (30), 4 (35), 5

(171), 6 (43), 7 (23), 8 (10), 9 (46), 10 (55), 11

(1), 12 (422), 13 (600), 14 (20), 16 (7), 17 (40),

18 (105), 19 (42), 20 (83), 23 (55), 24 (23), 25

(107), 26 (9), 27 (2), 28 (43), 29 (78), 30 (10),

31 (40), 32 (3), 33 (290), 34 (89), 35 (601), 36

(285), 37 (57), 38 (471), 39 (214), 40 (11), 41 (52),

43 (322), 44 (438), 45 (108), 46 (244), 47 (255),

48 (162), 51 (697), 52 (35), 53 (139), 55 (116), 58

(98), 59 (60), 60 (399), 61 (135), 62 (546), 63 (15),

64 (733), 65 (195), 66 (771), 67 (149), 68 (3), 69

33
34 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

(1470), 70 (45), 71 (112), 72 (2), 73 (12), 74 (396),

76 (443), 77 (210), 79 (40), 80 (2), 81 (199), 84

(110), 85 (261), 87 (285), 88 (6), 89 (96), 90 (228),

91 (148).

Caprellidea: SQ 1 (1), 2 (1), 7 (1), 12 (4), 15

(456), 17 (3), 18 (13), 20 (2), 22 (1), 24 (1), 25

(56), 28 (2), 33 (170), 34 (18), 35 (205), 36 (4),

38 (84), 39 (8), 43 (50), 44 (3), 45 (2), 51 (13),

53(21),55(7),60(93),61 (123),62 (78),64 (106),

65 (102), 66 (98), 67 (65), 70 (51), 71 (12), 74 (5),

76 (5), 79 (12), 81 (62), 85 (14), 87 (18), 89 (9),

90(15),91 (40).

Nebaliacea: SQ 43 (7), 44 (9), 51 (3), 53 (1),

60 (4), 61 (18), 62 (36), 64 (2), 65 (15), 66 (8),

69 (600), 70 (99), 73 (1), 77 (6), 81 (9), 85 (6),

87 (2),89(1),90(2).

Chironimid larvae: SQ 1 (26), 2 (1), 4 (1), 5 (15),

6(1).

Echinodermata:

Ophiuroidea:

Amphipholis squamata: S Q 25 (1) , 2 8 (3) , 30

(1) , 3 4 (3) , 35 (1) , 3 8 (6) , 4 3 (1) , 5 3 (2) , 6 4 (3) ,

6 5 (1) , 66 (2) , 67 (3) , 6 9 (10) , 70 (6) , 71 (1) , 73

(1) , 74(1) , 76(1) , 77(1) , 81 (4) , 8 7 (1) .

Amphiodia occidentalis: SQ 52 (4).

Holothurian, brown, 5-12 mm long: SQ 24 (4),

27 (8), 29 (27), 34 (2), 35 (43), 37 (1), 38 (6),

39 (7), 48 (49), 51 (10), 60 (19), 67 (7), 69 (10),

74(19),85(7),90(3) .

Holothurian, black: SQ 53 (14), 62 (21), 66 (8).

Enteropneusta: SQ 8 (5), 9 (6), 19 (2), 26 (3),

36(10),37(ll),38(21),4 1 (14), 43 (226), 46 (7),

47 (1), 51 (13), 53 (2), 58 (7), 59 (1), 63 (1), 64

(7),6 6 (5),6 7 (2),6 9 (1420), 71(1), 74(1), 77 (3),

85(1),8 9 (3),90(1),9 1 (2).

Ascidiacea, Eugyra glutinans: SQ 12 (72), 14 (1),

15 (25), 18 (82), 20 (15), 31 (10), 34 (1), 35 (465),

38 (39), 39 (5), 42 (5), 43 (153), 44 (519), 45 (2),

46 (71),47 (9), 48 (57), 50 (55), 51 (143), 52 (15),

54(43),56(43),58(2),6 0 (616), 62 (3), 64 (198),

65 (479), 66 (4), 67 (705). 69 (1420), 73 (280), 76

(835),77(781),88(2),91(2).
Appendix III

Nomenclatural List of Amphipoda, Polychaeta, Isopoda, and Mollusca from Bahia de San Quintin

References: Barnard (1964), Reish (1963), Menzies

(1962), Keen (1962).

Amphipoda, Gammaridea: Acuminodeutopus heteruropus, Ampelisca compressa, Amphideutopus oculatus, Amphilochus neapolitanus, Ampithoe longimana, Ampithoe plumulosa, Ampithoe pollex,

Aoroides columbiae, Colomastix pusilla, Corophium

acherusicum, Corophium baconi, Corophium uenoi,

Elasmopus antennatus, Elasmopus rapax, Ensayara

ramonella, Ericthonius brasiliensis, Heterophoxus

oculatus, Hippomedon denticulatus, Hyale rubra frequens (=H. "nigra"), Jassa falcata, Lembos macromanus, Leucothoe alata, Leucothoides pacifica,

Listriella diffusa, Listriella melanica, Lysianassa

holmesi (=Aruga h.), Maera danae, Maera sp.,

Metaphoxus fultoni, Microdeutopus schmitti, Microjassa macrocoxa, Monoculodes hartmanae, Orchomene

magdalenensis, Orchestia traskiana, Orchestoidea benedicti, Orchestoidea californiana, Paraphoxus bicuspidatus, Paraphoxus heterocuspidatus, Paraphoxus

obtusidens, Paraphoxus spinosus, Parallorchestes ochotensis, Pontogeneia "minuta," Pontogeneia quinsana,

Pontogeneia rostrata, Pseudokoroga rima, Rudilemboides stenopropodus, Stenothoe valida, Uristes

entalladurus.

Polychaeta: Anaitides williamsi, Anaitides nr. multiseriata, Arabella tricolor, Arenicola cristata, Armandia

bioculata, Axiothella rubrocincta, Brania clavata,

Capitella capitata, Capitita ambiseta, Chone mollis,

Chrysopetalum occidentale, Cirriformia luxuriosa, Cossura Candida, Dorvillea articulata, Eteone dilatae,

Eteone pacifica, Exogone verugera, Fabricia limnicola,

Glycera americana, Goniada brunnea, Haploscoloplos

elongatus, Hypoeulalia bilineata, Lepidonotus caelorum, Lumbrineris erecta, Lumbrineris minima, Marphysa disjuncta, Megalomma pigmentum, Neanthes

caudata, Nephtys caecoides, Nerinides maculata, Notomastus magnus, Onuphis microcephala, Ophiodromus

pugettensis, Pherusa capulata, Pista alata, Platynereis

bicanaliculata, Polydora uncata, Polyophthalmus pictus, Prionospio malmgreni, Prionospio pygmaeus, Scoloplos acmeceps, Scoloplos ohlini, Scyphoproctus oculatus, Sphaerodorum minutum, Spiophanes missionensis,

Trypanosyllis gemmipara, Typosyllis variegata.

Isopoda: anthurid, Cirolana diminuta, Dynamenopsis dianae, Erichsonella crenulata, Exocorollana

kathyae, Gnathia steveni, Haliophasma geminata, Jaeropsis dubia, Lironeca sp., Munna ubiquita, Paranthura elegans, Paracerceis sculpta, Rocinela aries,

Serolis carinata, Sphaeroma pentodon.

Mollusca: Acmaea depicta, Acteocina carinata,

Aequipecten circularis aequisulcatus, Assiminea compacta, Bittium quadrifilatum, Brachidontes sp., Chaetopleura gemmea, Cooperella subdiaphana, Crucibulum

spinosum, Cryptoma californica, Haminoea sp., Hiatella arctica, Lasaea subinridus, Leptopecten latiauratus, Lyonsia californica, Macoma yoldiformis, Marginella californica, Marginella pyriformis, Marginella

regularis, Mitrella carinata, Modiolus sp., Odostomia

fetella, Odostomia sp., Orobitella singularis, Ostrea

lurida, Parvilucina tenuisculpta, Protothaca staminea,

Solen rosaceus, Tellina buttoni, Terebra pedroana,

Trachycardium quadragenarium, Transennella tantilla, ?Tricolia sp., Turbonilla sp., Nudibranchiata

(various spp.).

35
Appendix IV

Data Decks and Methods

Data Decks

1. Alphabetical list of species and specimens for

each sample.

2. Chronological list of all samples and specimens

for each species.

3. A recast of deck 2 with samples arranged in order

according to number of specimens in each sample, from

low to high.

4. Master list of all species (like Table 1) arranged

alphabetically with the following columns: (1) number of samples in which species occurs; (2) total number of specimens in all samples; (3) mean number of

specimens per sample; (4) median number of specimens in positive samples; (5) straight-line numerical

median between columns 3 and 4 to indicate minimal

frequency of contagion for each species; see deck 5 for

option.

5. (optional) Plots on arithmetic graph paper for

each species occurring in 10 percent or more of the

samples (found in deck 4, column 1); data from deck

3 are graphed with number of specimens per sample

plotted on abscissa and samples plotted by even increments on ordinate. Line connecting dots is drawn

and dot selected where significant curve commences

near high end of plots. Dot level read as number of

specimens and entered in deck 4, column 5 as optional

substitute for minimum level of contagion.

Method 1

Test of association between pairs of species to produce Figures 1-3. Formula adapted from Cole (1949).

Represents rudimentary elucidation of community foci.

Pairs of species are selected from deck 2 to include only

those occurring in more than 10 percent of the samples

or those with very high specimen frequencies in a few

samples.

Formula:

r_kn

C = coefficient of association; a = number of

samples with first species of the pair; b = number of

samples with second species of the pair; h = number

of samples containing both species of the pair; n =

number of samples (90).

Results of C are tabulated in a matrix like Figure

4. C-values for pairs of species are separately listed

in order from high to low. Arbitrarily high values of

C arranged in polygons like Figures 1-3 so that each

species permitted in a corner has a selected minimum

value with all other species in the corner. Minimum

values may be selected by drawing on field experience

if one biotope has been observed to contain two or

more species strongly associated together. Various polygons are constructed to utilize several arbitrary levels

of C; final presentation of association polygon based

on best fit; polygons made from San Quintin data

show best fit when all species with 99 percent of their

specimens confined to Zostera community are incorporated in one corner; good fit assumed because another

corner contains obvious members of a second assemblage recognized in the field (Eugyra-Ampelisca);

third corner thus contains associates not otherwise

determinable in the field. Lines in Figures 1-3 connecting species outside of corners present associative

pairs with C-values higher than stated minimum.

Alternatives of n in Method 1

A. All positive samples for each species of the pair

are utilized.

1. n= 90 (total samples in survey) (Figure 3).

2. n = a + b - h.

B. Only positive samples contagious for each species

of the pair are utilized.

1. n = 90 (Figure 1).

2. n= a + b — h (superior method) (Figure

2).

Method 2

RESIDUALS.—Samples assigned to assemblages by

means of Method 1 are removed from deck 1. If each

36
NUMBER 4 4 37

corner of the polygon represents an Assemblage, then

all samples containing any of those species in contagious frequencies are removed from deck 1. Residual

samples contain associations based on one pair of

species or one species alone. Recast of Method 1 on

residual samples of deck 1 will select any further

samples with pairs of species as dominants. Residual

samples are arranged according to their dominant

species (by highest frequency of specimens).

Method 3

MINIMUM FAUNAL PERCENTAGES (MFP) (Sanders,

1960).—The total number of specimens of all species

in one sample is summed (from deck 1). The percentage composition of each species in a sample is found

by dividing the number of specimens of each species

by the total number of specimens of all species. Data

sheets are completed for all samples. Samples are now

compared by pairs. If a species is found in both samples

of a pair the lesser percentage factor of that species

in either sample is extracted to a new data card, identified by the joint numbers of the samples. The lesser

percentage factors of all species common to both

samples are extracted and summed on the data card.

This sum is the MFP; it is found for all possible pairs

of samples. The new data deck is arranged with MFP

values from highest to lowest. The highest sum is

chosen as a focus and the deck searched for the next

highest sum having one of its conjoint sample numbers

identical to one of the sample numbers on the focal

card. Two cards now set together have three sample

numbers between them. The deck is searched again

for the next highest sum having any of the three

sample numbers; three cards now have four sample

numbers; this procedure is repeated through the half

of the deck having the highest MFP values; after the

first cluster of cards is removed, the next highest card

is chosen as a focus and a second cluster of cards is

generated. All clusters in the first half of the deck

are found; samples in these clusters represent the

majority of samples that can be utilized as foci for

the description of communities but a few samples will

remain in the deck that are highly dominated by one

species but have low MFP values. The MFP system

delegates high conjoint indices to samples with internal

homogeneity but delegates low values to the odd

samples with low diversity of species and high specimen frequencies of only one of the species. Unless

two or more of these samples occur in the data deck

they fail to form clusters. The San Quintin data contain no similar pairs of these samples (like sample 78

in Figures 9-10), but presumably a higher sampling

frequency would produce clusters of these.

Clusters of samples may be arranged in trellises

(Figure 4) and the MFP values for each sample

summed so as to determine weak samples with low

sums that should not be included in the descriptions of

community foci.

Cards in the second half of the deck may be joined

to the initial clusters in the same procedure and a tree

of relationships formed by spreading the cards on a

table top in the form of clusters as they are removed

from the deck and matched.

To clarify anomalous samples in the tree of relationships, a master visual card for each sample is formed.

A symbol for each species in the samples is devised

and printed by replication on the sample card, one

symbol for each specimen of the species in the sample.

To reduce the sizes of the cards generated from the

San Quintin data, one symbol was printed for each

ten specimens in the sample. This reduced the positive

reports in a sample to less than ten species. Symbols

can be formed from the alphabet and the most frequently occurring species can be assigned colors to

assist visual correlations of cards. The master cards

are distributed throughout the tree of relationships at

the positions marked by conjoint occurrences of the

samples. One may now readily detect anomalous

samples, especially those that are heavily dominated

by one main species and that have been displaced in

the MFP system.

Method 4

MORISITA-ONO INDEX OF FAUNAL AFFINITY (Morisita,

1959, b; rewritten by Ono, 1961) .—An index of affinity is found for a pair of samples by this method; coefficients (CA) are stored on cards or in matrices and

may be evolved into trees of relationships as in

Method 3.

Formula:

nlin2i

(XI +X 2) M N2 in which nli and n2i

are the number of specimens of conjoint species (i-th)

in the two samples and Nl, N2 are the total numbers
38 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

of specimens in the two samples. The X coefficients are

determined for each sample by

^ ni(ni— 1)

X

~£tN(N-l)

The arithmetic is elaborated in a sample problem

below:

Sample number 44 89

Species A nla 9 (specimens) n2a 2

B nib 6 n2b 4

C nlc 3 n2c 0

D nld 0 n2d 1

E nle 2 n2e 5

Nl=20 N2= 12

Lambda-values (formula 2) are first determined for

each sample; the values for samples 44 and 89 are

found as follows:

, , , 9(8) 6(5) 3(2) 0(0)

20(19)^20(19) ' 20(19)

 r20(19)

34

X89=;J-5Q==0-26 (rounded) (same procedure).

The coefficient of affinity (formula 1) is computed

utilizing values (SD=same denominator as first

expression)

(9) (2)

(6)(4) _

SD ^ SD

(.29+.26) (20) (12)

(OKI) ,

SD "•"

J 8 ,2 4

W2+W2+m=^ f!=0.79 (Rounded).

Method 5

DENDROGRAMS.—The scores of the CA or MFP coefficients are arranged in a half-matrix (trellis).

Dendrograms are formed in a weighted pair-group

method (Mountford, 1962), by evolving a series of

matrices calculated in succession from the prime matrix. The pair of samples in the first matrix with the

highest joint coefficient is coalesced as if it were a single

sample and a new matrix is developed by comparing

the conjoint sample with all others. The second matrix

also includes all of the prime-matrix coefficients less the

first pair. From the second matrix the pair of samples

with the highest joint coefficient is again selected,

joined together as one sample and compared with all

others to form the third matrix. This procedure is

carried to its conclusion when all samples have been

joined together by their highest successive coefficients.

In comparing a conjoint sample with a single sample

one must average the joint coefficient of the two

numbers of the conjoint sample with the coefficient of

the single member in the immediately previous matrix

without returning to the first matrix, except in the first

increment. The conjoint coefficients are recorded and

utilized to make dendrograms as in Figures 7-10, by

joining together samples and groups of samples according to the coefficient arranged along the ordinal axis.

The spread of the dendrites on the abscissa is simply

a matter of convenience in dispersing sample pairs

that overlap.

These techniques are extraordinarily time-consuming; intercomparison of more than 24 samples requires

a computer; a desk-calculator is necessary for any

number of samples between 10 and 24. A group of 24

samples requires about 40 hours of calculating time

(if samples have a maximum number of 120 species

and an average of 1,000 specimens per sample).

Method 6

MAZE-GRIDS.—A maze-grid as herein defined is a

compression into 2 dimensions of a 3-dimensional tree

of relationships evolved in Method 3 or a dendrogram

evolved in Method 5. A tree of relationships may be

formed without computing either CA or MFP values

by making a card for each sample on which are printed

symbolically the number of specimens of each species;

a symbol for each species is replicated on the card for

each specimen (or a consistent fraction of the specimens). In the San Quintin samples, N=90, total

species about 120, mean number of specimens per sample of 1006, it was possible to divide by 10 the number

of specimens of each species and put one symbol per

ten specimens of each species on each card. If color

symbols or blocks of color in proportion to frequencies

of species are used the landscape effect on the card can

be readily classified by eye and the samples arranged
NUMBER 44 39

into a tree. The maze-grid is found by arranging the

cards into several best fits on a rectangular or square

grid (Figure 11). Lines of close interrelationship between samples may be plotted; walls between boxes of

the grid may be thickened or windows may be opened

according to the degree of relationships among contiguous samples found in MFP or CA values. The ease

in classifying samples from San Quintin by this method

did not warrant calculation of window widths in the

grids printed herein and they are simply left closed

where no obvious relationships between samples

occurred.

FIGURE 1.—Relationships of three groups of species in Bahia de San Quintin. Each corner holds

species with coefficients of association exceeding 3.37 to all other species in the group. Lines

connect other species with similarly high coefficients of association. For example, Listriella would

be included in the Ericthonius corner, but it has a strong association with only 5 of the 6

species in the Ericthonius group. Diagram based on standard formula with n=90 and utilizing

only "contagious" samples for each species (method B-l).
40 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

CIRRIFORMIA PRIONOSPIO

AMPHIDEUTOPUS MEGALOMMA

FIGURE 2.—Relationships of three groups of species in Bahia de San Quintin. Compare with

Figure 1. Diagram based on standard formula utilizing "contagious" samples for each species

with n=a+b—h (method B-2).
NUMBER 44

41

FIGURE 3.—Relationships of three groups of species in Bahia de San Quintin. Compare with

Figures 1 and 2. Diagrams based on standard formula utilizing all samples, including "noncontagious" members with n=90 (method A-l).
42

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

12

15

18

35

43

44

46

48

51

60

64

65

67

69

73

76

77

78

STA.

TOTALS

90

X

65

50

26

17

39

37

28

43

29

34

48

22

39

37

19

18

29

12

| 57

9

89

37

X

40

21

9

46

27

20

31

17

29

42

19

44

43

15

10

40

15

t 51

8

87

38

61

X

46

24

27

55

32

57

46

44

44

35

27

34

30

30

15

18

1 63

6

85

50

34

37

X

33

30

57

49

64

65

50

46

52

12

26

36

40

3

35

1 65

6

81

33

61

61

33

X

28

32

30

29

42

52

37

39

13

13

16

28

6

43

1 44

8

79

30

47

52

29

64

X

20

30

22

33

28

59

27

70

54

11

25

67

44

1 61

6

74

56

40

43

57

40

40

X

40

71

52

52

37

43

14

27

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38

5

46642

70

28

63

62

23

71

58

33

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43

46

27

43

39

14

24

28

37

3

48

| 533

66

43

58

68

44

64

57

46

59

X

54

47

39

46

16

27

41

37

6

51

m

i—

NO

62

35

54

56

32

76

59

40

76

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53

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66

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60

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61

33

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56

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79

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39

78

58

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X

38

37

11

12

24

25

6

64

S

m

53

28

57

39

28

57

48

39

44

39

50

54

X

46

44

48

22

42

37

65

K)

34

27

37

46

23

63

56

40

54

52

61

63

57

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16

44

49

54

8

67642

STA.

90

89

87

85

81

79

74

70

66

62

61

53

34

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56

11

16

66

69

CO

9

TOTALS

438

611

619

419

702

600

513

649

645

680

695

540

579

X

46

50

44

73625 X

53

1

76484 X

8

77568

riTA CAPI" -snif :THOH -ERK

OH

CO

o

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78350

EUGYRA-AMPELISCA

FIGURE 4.—Strength of association among samples of two communities; lower left of graph

=Eugyra-Ampelisca, upper right=Zostera, Method=minimum faunal percentages (see text).
NUMBER 44 43

CO

< 2 °

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CO

a.

|

O

o 51 £

< — O

o a. <

EUGYRA

AMPELISCA

ERICTHONIUS

CAPITITA

PISTA

ACUMINODEUTOPUS

•

1.30

0.87

1.36

1.53

1.35

0.90

•

1.24

1.10

1.38

1.31

0.47

0.83

•

1.70

2:17

1.41

0.85

0.86

0.91

•

1.52

1.22

0.82

0.93

0.90

0.93

•

1.55

0.89

0.93

0.87

0.88

0.78

•

C a " ab

n = a + b-h

Ca max = 1.0

OTHER SPECIES PAIRS

EXCEEDING 0.90= 138

(OUT OF POSSIBLE 1482)

C a ^ n=9 0

OTHER SPECIES PAIRS EXCEEDING 1.50 =202

(OUTOF POSSIBLE 1482)

FIGURE 5—Associative indices of pairs of species obviously dominating three associations utilizing

two methods as shown. Graph demonstrates low information content of these methods as

opposed to utilizing samples in "contagious" condition for each species.
44 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

90—1

AMPELISCA-EUGYRA

PRIONOSPIO

ACUMINODEUTOPUS-RUDILEMBOIDES-PISTA

MICRODEUTOPUS-AMPHIDEUTOPUS

SAMPLE NO.

FIGURE 6.—Continuum of samples from center of Eugyra-Ampelisca community on left, through

Acuminodeutopus-Rudilemboides ecotone in middle to center of Prionospio community on

right. Samples marked with asterisks are arranged in a dendrogram of Figure 8.
NUMBER 44 45

EPBXH

61

EBHxc

62

ECB

70

HX

90r

EXbhc

34

HEBXI

79

ehxb

57

BX

f

EBHxc

81

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53

80

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LU

70

89

:HTCB

87

6 0 L

M.F.P.

hp

85

I

Sharb

90

E H «lap

74

ZOSTERA

FIGURE 7.—Dendrogram showing association among all samples of Zoster a community. Based

on minimum faunal percentages. Each dendrite bears sample number and letter abbreviations

denoting major species in sample. Letters occur in four sizes, largest denoting occurrence of

200+specimens in sample, next 101-199 specimens, next 51-99, smallest 11-50. Abbreviations:

A=Acuminodeutopus, B=Capitita ambiseta, D=Amphideutopus, E=Ericthonius, H=Hyale,

L=Elasmopus, M=Microdeutopus, ?=Prionospio, R=Rudilemboides, S=Scoloplos acmeceps,

T=Pista, X=Exogone.
46

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

100

90

80

£70

z

u.

at

fe 60

50

PEA

18

3 0 L

MOR.

DOMINANTS

A -AMPELISCA

C -COSSURA

E -EUGYRA

E -EXOGONE

P -PRIONOSPIO

E xP

ft.

PEA

18

M.F.P.

cP

39

I

FIGURE 8.—Dendrograms representing relationships among samples of Eugyra-Prionospio

continuum of Figure 6. Based on two methods, Morisita and Minimum Faunal Percentages.
NUMBER 44 47

70

60

50

40

Ex (FS)

55

o

z

(F)

91

cP

39

CEx

45

J

64

20

10

4

ZOSTERA PRIO-EUGYBA

FABRICIA

P

14

P-A-Z

A

78

M.F.P.

REM

43

T

(E)

48

EUGYRA

20

Ac

A

C

E

E

x

F

M

P

R

- ACUMINODEUTOPUS

-AMPEUSCA

- COSSURA

-EUGYRA

- EXOGONE

-FABRICIA

- MICRODEUTOPUS

- PRIONOSPIO

- RUDILfMBOIDES

S - SCaOPLOS ACMECEPS

Z - ZOSTERA -ERICTHONIUS

FIGURE 9.—Dendrogram of strong, medium, and weak samples of 4 communities and one ecotone

in Bahia de San Quintin. Based on minimum faunal percentages. A strong sample (heavy

dominance by one species), a weak sample (small numbers of individuals), and two medium

samples (diversity of species with numerous individuals) are plotted for each of the five

assemblages. Four strong clusters representing good communities occur; two strong samples

remain with their communities but two others (14 and 78) are cast out of their clusters

because of heavy dominance by one species.
48

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

80r

70

60

550

u

(FS)

S5

(F)

91

I

30

20

10

Z

81

JCP

39

EP

67

ER

35

CE x

45

- I P

49

I

ExP

64

I

ExF

4

FABRICIA

(E)

48

_J

(ACE)

20

MOR.

EUGYRA

FIGURE 10.—Recasting of data plotted in Figure 9, utilizing Morisita index of affinity.
NUMBER 44 49

31

AC

22

(A)

13

••••••

KA

Ex 28

• •• •

E,K

11

(P)

21

(P)

17

P

C

23

P

C

58

PC

44

• •

: A

REDMT

78

• •

: A

M(R)

10

KH

(SE)

14

P

16

P

37

PC

9

CP

41

C

P

24

CP

65

: A

ERIDAeM

69

• •••

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LUIR

12

A

PEHA c _ ^

19

P

29

P

26

• •

c

p

27

(CSP)

49

P

•Ex Ac

66

• •

z

CP

15

A

ACPS

73

AE

50

EA

18

PEA

32

C

36

P

(CS)

39

C

PIS

62

• •

z

EXPC

53

Z

EXP

20

AC(E)

51

E

PAgC

35

E

PAeRDFC

45

C

ExAc(P)

47

P

S

71

PS

74

Z

s

90

Z

SRAC

61

• ••

z

PEXC

56

E

76

. E

SCA,.

67

E

RACM

54

C

EXFEA

88

S

63

S

84

(SR)

83

RZ

81

•

z

ExC

46

ECPACEXR

60

. E

RAgDTC

64

E,PAC

RTE

38

ExPC

TA^RS

33

ACF

PR

40

(S)

34

z

Ex

79

Z

Ex

87

Z

CT

48

EDR

77

E

IR

25

ExS^SR

1

(EXF)

2

(EXF)

42

F

p

91

o

85

Z

70

• •

. z

c

43

R

EM

80

Ex

5

• •

E,

F

4

Ex

(F)

3

• •

F

Ex

6

• •

F

<EX)

55

(FS)

57

Z

89

. z

c

FIGURE 11.—Association grid of 81 samples from Bahia de San Quintin. Two-dimensional

presentation represents one of several possible "best-fits." Heavy lines separate communities, but

windows denote relationships contributing to appearance of continuum among communities

of lagoonal habitat. See Figure 18 for condensation. Sample numbers in upper right corners

of squares. Dots indicate extreme abundance of certain species. Letter symbols in middle of

boxes indicate primary domination (numerical) and symbols on lower margins of boxes denote

secondary dominants. Parentheses indicate weak domination (low numerical abundance).

A.=Ampelisca, Ac=Acuminodeutopus, C=Cossura, Gap=Capitella, T>=Amphideutopus,

E=Eugyra, Ex=Exogone, F=Fabricia, l—Capitita, K=Kalliapseudes, L=Lysianassa,

M—Microdeutopus, P=Prionospio, S=Scoloplos acmeceps, T—Pista, X}=Uristes, Z=

{Zostera aggregates), combined frequencies of Ericthonius, Hyale, Elasmopus, Pontogeneia.
50 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

10,000

8000

6000

g 4000

<

2000

2 1000

°- 800

to

^ 600

=>

| 400

o

z

200

100

PERCENT SAND

20 100

20,000

10,000

8000

MEDIAN DIAMETER

20 40

MICRONS

FIGURE 12.—Relationships of important benthic species to sedimentary parameters. Upper

graph represents abundance in relation to percentage of sand in substrate and lower graph

represents abundance in relation to median diameter of particles in substrate. Partition of

Fabricia into two sections in upper graph demonstrates stratification of silt over sand.
NUMBER 44 51

SAN QUINTIN BAY

PHYSIOGRAPHY

MUT1OL Kil l

FIGURE 13.—Physiography of Bahia de San Quintin.
52

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

116*00"

BAHIA DE SAN QUINTIN

_£^

FIGURE 14.—Distribution of sediments in east arm of Bahia de San Quintin.
NUMBER 44 53

BAHIA DE SAN QUINTIN

SURVEY OF 1886 CORRECTED

0

FIGURE 15.—Distribution of biotic communities in east arm of Bahia de San Quintin. Dots

indicate, samples. A—Ampelisca, E=Eugyra, Y=Fabricia, K=Kalliapseudes, V=Prionospio,

Z=Zostera, pyg=Megalomma pigmentum.
54

INNER BAY

I H

AREA

m

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

OUTER BAY

Q_

ti

O

25

24

23

22

21

on

ZU

19

18

17

16

38

37

-i 36

<

to

_, 35

e 34

1.9

1.8

*1.6

2 1.4

_i 1.2

<

1 0

a. 0.8

0.6

0.4

0.2

42

39

* 3 6

2 33

^ 30

i 27

<C 24

a

 21

18

15

12

6

o

o

(_ *••••/ygy.'£> ~• — -^V ^ AUG.60

AUG. 60

FEB. 61

NOV. 60

AUG.60

APR. 60

AUG. 61

AUG. 61

AUG. 61

FIGURE 16.—Water quality of 5 zones in east arm of Bahia de San Quintin, extending from

I=innermost to V=outermost portion of arm. Temperature, salinity, phosphates, silicates, and

dissolved oxygen are plotted in either 4 or 5 surveys. Considerable differences are noted in the

August 1960 and August 1961 surveys.
NUMBER 44 55

40,000

20,000

10,000

6000

4000

2000

1000

600

400

200

BASE

200

10.000

COMMUNITIES

PRIONOSPIO MALMGRENI

FIGURE 17.—Cross section of numerical frequency of major species in 5 biotic assemblages of

Bahia de San Quintin. Plotted on semilog scale from base line in middle with overemphasis on

frequency of species in middle of graph. Species situated toward base line commonly occur in

all communities. Species plotted above base line dominate Eugyra-Ampelisca and Fabricia

communities, those below base line dominate Ericthonius and Prionospio communities. Crosssectional limits occur between outermost heavy lines in upper graph, with total individuals per

square meter summed below for each community. Lower graph plotted on arithmetic scale,

representing important species of "others" fraction in main graph. For purposes of clarity

this figure has been condensed.
56

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

AMPELISCA EUGYRA

FABR.

ZOSTERA

FIGURE 18.—Maze-grid summarizing Figure 11. Lines connecting centers of sample boxes

represent imaginary expansion of 2-dimensional presentation to 3-dimensions.
Index

Citations of species in tables and appendices omitted unless species is cited only in those places; but minor

species generally cited only once, either in a table or in one appendix. Names of genera and communities in text

are cited as binominals in index. a = appendix; t=table.

acherusicum, Corophium, 8,19, 20

Acmaea depicta, 9t

acmeceps, Scoloplos, 3t, 5, 8,9, 10,18,19, 22

Acteocina carinata 3t, 10, 11

Acuminodeutopus heteruropus, 3t, 5, 7,8, 11,13, 22, 25

Aequipecten circularis aequisulcatus, 9t

alata, Leucothoe, 20

Pista, 3t, 5, 6, 7,8

ambiseta, Capitita, 3t, 5, 6,8, 9,19,22

americana, Glyccra, 14t

Ampelisca compressa, ampeliscid, 3t, 4, 5, 6, 7, 8, 9, 11, 17,

18,19,22,24,27

Amphideutopus oculatus, 3t, 9

Amphilochus litoralis, 19t

neapolitanus, 14t

Amphiodia occidentalis, 34a

Amphipholis squamata, 13t, 34a

Ampithoe longimana^ 19, 20

plumulosa, 16t

pollex, 16t

Anai tides williamsi, 18

nr. multiseriata, 10t

Anamixis linsleyi, 20

antennatus, Elasmopus, 3t, 8,13, 18

anthurid, 35a

Aoroides columbiae, 9t, 19t

Arabella irioolor, 12t

arctica, Hiatella, 2It

Arenicola cristata, 16t

arics, Rocinela, 35a

Armandia bioculata, 8, 18

articulata, Dorvillea, 22

Stauronereis, 18

Ascidiacea, see Eugyra glutinans

Assiminea compacta, 35a

Axiothella rubrocincta, 3t, 18, 22

baconi, Corophium, 3t, 20

benedicti, Orchestoidea, 35a

bicanaliculau, Platyncreis, 3t, 5,8, 18

bicuspidatus, Paraphoxus, 17t

bilineata, Hypoeulalia, 9t

bioculata, Armandia, 8, 18

Bittium quadrifilatum, 35a

Brachidontes sp., 35a

Bracyhura, 33a

Brania clavata, 3t, lOt

brasiliensis, Ericthonius, 3t, 5,6,8,13, 18, 20

Podocerus, 19,20

brevipes, photis, 19t

brunnea, Goniada, 35a

buttoni, Tellina, 3t, 9,15,18

caecoides, Nephtys, 17t

caelorus, Lepidonotus, 9t

californiana, Orchestoidea, 35a

californica, Cryptomya, 211

californica, Lyonsia, 16t

Marginella, 21t

Callianassaspp. (ghost-shrimp), 8,10, 33a

Candida, Cossura, 3t, 5, 8,9, 10,13, 20,22

capitata, Capitella, 13, 18,19, 22

Capitella capitata, 13,18, 19, 22

Capitita ambiseta, 3t, 5,6,8,9,19, 22

Caprellidea, lit,34a

capulata, Pherusa, lOt

carinata, Acteocina, 3t, 10,11

Mitrella, 9t

Serolis, 14t

caudata, Neanthes, 3t, 14t

Cerapus tubularis, 19t

Chactoplcura gemmea, 35a

Chaetozone spinosa, 17t

Cheiriphotis mcgacheles, 19t

Chironomid larvae, 15t, 34a

Chone mollis, 3t, 8

Chrysopetalum occidentale, 9t

Ciliacea sp., 9t

circularis aequisulcatus, Aequipecten, 9t

Cirolana diminuta, 11,13

Cirriformia luxuriosa, 3t, 5,6, 10,22

clavata, Brania, 3t, lOt

Colomastix pusilla, 35a

columbiae, Aoroides, 9t, 19t

compacta, Assiminea, 35a

compressa, Ampelisca, 3t, 4, 5, 6, 7, 8, 9, 11, 17, 18, 19, 22,

24,27

conchicola, Photis, 19t

Cooperella subdiaphana, lOt

57
58

INDEX

Corophium acherusicum, 8, 19, 20

baconi, 3t, 20

insidiosum, 19, 20

uenoi, 11,20

Cossura Candida, 3t, 5,8,9,10, 13, 20, 22

crassus, Kalliapseudes, 3t, 5,8,9, 11, 12, 28, 33a

crenulata, Ericsonella, 9t

cristata, Arenicola, 16t

Crucibulum spinosum, 2It

Cryptomya californica, 2It

Cumacea, 20, 33a

Cumellasp., 13t, 33a

danae, Maera, 35a

Dendraster sp., 17t

denticulatus, Hippomedon, 12t

depicta, Acmaea, 9t

dianae, Dynamenopsis, 35a

Diastylopsis tenuis, 17t

difFusa, Listriella, 9t

dilatae, Eteone, 14t

diminuta, Cirolana, 11, 13

Dorvillea articulata, 22

dubia, Jaeropsis, 35a

Dynamenopsis dianae, 35a

Echinodermata, 20, 34a

eelgrass, see Zostera marina

effrenus, Megamphopus, 19t

Elasmopus antennatus, 3t, 8, 13, 18

rapax, 5, 19, 20

serricata, 19t

elegans, Nothria, 15, 18

Paranthura, 3t, 9

elongatus, Haploscoloplos, 17t

Ensayara ramonella, 35a

entalladurus, Uristes, 3t, 9

Enteropneusta, 12t, 34a

epistomus, Paraphoxus, 17t

erecta, Lumbrineris, 9t

Ericsonella crenulata, 9t

Ericthonius brasiliensis, 3t, 5, 6, 8, 13, 18, 20

Eteone dilatae, 14t

pacifica, 12t

Eugyra glutinans, 3t, 4, 5, 6, 7, 8, 9, 10, 13, 17, 18, 19, 22,

24, 27, 34a

Exocorollana kathyae, 35a

Exogone verugera, 3t, 5, 7,8,9, 10, 11, 13,18, 22

Fabricia limnicola, 3t, 5,6, 8, 10,11,13, 19, 22, 27, 28

falcata, Jassa, 19

fetella, Odostomia, lOt

flatworm, see Turbellaria

frequens, Hyale, see H. rubra

fultoni, Metaphoxus, 11, 13

geminata, Haliophasma, 9t

gemmea, Chaetopleura, 35a

gemmipara, Trypanosyllis, lOt

glutinans, Eugyra, 3t, 4, 5, 6, 7, 8, 9, 10, 13, 17, 18, 19, 22,

24, 27, 34a

Glycera americana, 14t

Gnathia steveni, 35a

Goniada brunnea, 35a

littorea, 17t

Haliophasma geminata, 9t

Haminoeasp., lOt

Haploscoloplos elongatus, 17t

pugettensis, 18

hartmanae, Monoculodes, 13t

heterocuspidatus, Paraphoxus, 16t

Heterophoxus oculatus, 11, 13

heteruropus, Acuminodeutopus, 3t, 5, 7, 8, 11, 13, 22, 25

Hiatella arctica, 2 It

Hippomedon denticulatus, I2t

holmesi (—Aruga h.), Lysianassa, 3t, 9, 17

Holothurian, lit, 34a

Hyale rubra frequens (=H . "nigra"), 3t, 8, 13, 18, 19

Hypoeulalia bilineata, 9t

insect larvae, see chironomid

insidiosum, Corophium, 19, 20

iricolor, Arabella, 12t

Ischyrocerus litotes, 19t

Isopoda, 20

Jaeropsis dubia, 35a

Jassa falcata, 19

Kalliapseudes crassus, 3t, 5, 8, 9, 11, 12, 28, 33a

kathyae, Exocorollana, 35a

lacia, Photis, 17t

Lasaea subviridis, 211

latiauratus, Leptopecten, 9t

Lembos macromanus, 3t, 9t

Lepidonotus caelorus, 9t

Leptopecten latiauratus, 9t

Leucothoe alata, 20

Leucothoides pacifica, 20

limnicola, Fabricia, 3t, 5, 6, 8, 10, 11, 13, 19, 22, 27, 28

Lironeca sp., 35a

Listriella diffusa, 9t

melanica, 3t, 11

litoralis, Amphilochus, 19t

litotes, Ischyrocerus, 19t

littorea, Goniada, 19t

longimana, Ampithoe, 19, 20

Lumbrineris erecta, 9t

minima, 3t, 22

lurida, Ostrea, 211

luxuriosa, Cirriformia, 3t, 5, 6, 10, 22

Lyonsia calif ornica, 16t

Lysianassa holmesi ( = Aruga h.), 3t, 9, 17

Macoma yoldiformis, lOt

macrocoxa, Microjassa, 9t

macromanus, Lembos, 3t, 9t

maculata, Nerinides, 10

Maera danae, 35a

magdalenensis, Orchomene, 3t, 11

magnus, Notomastus, 12t

malmgreni, Prionospio, 3t, 5, 6, 7, 8, 9, 10, 13, 15, 18, 19,

22, 25, 27

Mandibulophoxus uncirostratus, 17t
INDEX 59

Marginella californica, 2It

pyriformis, 35a

regularis, 35a

marina, Zostera, 4, 5, 6, 7, 8, 9, 13, 18, 19, 23, 26, 27, 28

Marphysa sanguinea, 12t

martesia, Megamphopus, 19t

megacheles, Cheiriphotis, 19t

Megalomma pigmentum, 3t, 10

Megamphopus effrenus, 19t

martesia, 19t

melanica, Listriella, 3t, 11

Metaphoxus fultoni, 11, 13

microcephala, Onuphis, 3t, 8, 9, 18

Microdeutopus schmitti, 3t, 9

Microjassa macrocoxa, 9t

minima, Lumbrineris, 3t, 22

"minuta", Pontogeneia, 20

minutum, Sphaerodorum, 35a

missionensis, Spiophanes, 18

Mitrella carinata, 9t

Modiolus sp., 8

mollis, Chone, 3t, 8

Monoculodes hartmanae, 13t

multiseriata, Anaitides, lOt

Munna ubiquita, 9t

Mysidacea, 33a

Neanthes caudata, 3t, 14t

neapolitanus, Amphilochus, 14t

Nebaliacea, nebalians, 9, lOt, 34a

Nemertea, 33a

Nephtys caecoides, 17t

Nereis procera, 18, 20, 22

Nerinides maculata, 10

newportensis, Prionospio h., 22

Nothria elegans, 15, 18

Notomastus magnus, 12t

Nudibranchiata (various spp.), 35a

obtusidens, Paraphoxus, 3t, 20

occidentalis, Amphiodia, 34a

occidentale, Chrysopetalum, 9t

ochotensis, Parallorchestes, 35a

oculatus, Amphideutopus, 3t, 9

Heterophoxus, 11, 13

Scyphoproctus, 3t, 11

Odostomia fetella, lOt

sp., 35a

ohlini, Scoloplos, 3t, 11, 22

Oligochaeta, 33a

Olivellasp., 17t

Onuphis microcephala, 3t, 8,9, 18

Ophiodromus pugettensis, 9t

Ophiuroidea, 34a

Orchomene magdalenensis, 3t, 11

Orchestia traskiana, 35a

Orchestoidea benedicti, 35a

californiana, 35a

Orobitella singularis, 35a

Ostracoda, 33a

Ostrealurida,21t

Oxyurostylis pacifica, 12t, 33a

sp., lOt, 33a

tertia, lit, 33a

pacifica, Eteone, 12t

Leucothoides, 20

Oxyurostylis, 12t, 33a

Paracerceis sculpta, 9t

Paraphoxus bicuspidatus, 17t

epistomus, 17t

heterocuspidatus, 16t

obtusidens, 3t, 20

spinosus, 20

Parallorchestes ochotensis, 35a

Paranthura elegans, 3t, 9

Parapleustes pugettensis, 19t

Parvilucina tenuisculpta, lOt

parvus, Tharyx, 18, 20, 22

paucibranchiata, Polydora, 11, 20

pedroana, Terebra, 35a

pentodon, Sphaeroma, 35a

Pherusa capulata, lOt

Phoronidea, phoronids, 14t, 33a

Photis brevipes, 19t

conchicola, 19t

lacia, 17t

Phyllospadix sp., 18, 19, 27

pictus, Polyophthalmus, 9t

pigmentum, Megalomma, 3t, 10

Pista alata, 3t, 5, 6, 7, 8

Platynereis bicanaliculata, 3t, 5, 8,18

plumulosa, Ampithoe, 16t

Podocerus brasiliensis, 19, 20

pollex, Ampithoe, 16t

Polydora paucibranchiata, 20

Polydora uncata, 11, 17t

Polyophthalmus pictus, 9t

Pontogeneia "minuta", 20

quinsana, 3t, 8, 18, 19

rostrata, 35a

Prionopsio h. newportensis, 22

malmgreni, 3t, 5, 6, 7, 8, 9, 10, 13, 15, 18, 19, 22, 25, 27

pygmaeus, 3t, 35a

procera, Nereis, 18, 20, 22

Protothaca staminea, 35a

Pseudokoroga rima, 9t

pugettensis, Ophiodromus, 9t

Parapleustes, 19t

pusilla, Colomastix, 35a

pygmaeus, Prionospio, 3t, 35a

pyriformis, Marginella, 35a

quadragenarium, Trachycardium, lOt

quadrifilatum, Bittium, 35a

quinsana, Pontogeneia, 3t, 8, 18, 19

ramonella, Ensayara, 35a

rapax, Elasmopus, 5, 19, 20

rectipalmum, Synchelidium, 19t

regularis, Marginella, 35a

rima, Pseudokoroga, 9t
60 INDEX

Rocinela aries, 35a

rosaceus, Solen, 12t

rostrata, Pontogeneia, 35a

rubia frequens (=H. "nigra"), Hyale, 3t, 8, 13, 18, 19

rubrocincta, Axiothella, 3t, 18, 22

Rudilemboides stenopropodus, 3t, 5, 6, 7, 8, 13, 22, 25

sanguinea, Marphysa, 12t

schmitti, Microdeutopus, 3t, 9

Scoloplos acmeceps, 3t, 5,8, 9, 10, 18, 19, 22

anniger, 17t

ohlini, 3t, 11,22

sculpta, Paracerceis, 9t

Scyphoproctus oculatus, 3t, 11

Serolis carinata, 14t

scrricata, Elasmopus rapax, 19t

singularis, Orobitella, 35a

Sipunculida, 33a

Solen rosaceus, 12t

Sphaerodorum minutum, 35a

Sphaeroma pentodon, 35a

spinosa, Chaetozone, 17t

spinosum, Crucibulum, 211

spinosus, Paraphoxus, 20

Spiophanes missionensis, 18

squamata, Amphipholis, 13t, 34a

staminea, Protothaca, 35a

Stauronereis articulata, 18

stenopropodus, Rudilemboides, 3t, 5,6, 7,8,13, 22, 25

Stenothoe valida, 20

steveni, Gnathia, 35a

subdiaphana, Cooperella, lOt

subviridis, Lasaea, 21t

Synchelidium rectipalmum, 19t

Tanaidacea, 20, 33a

tantilla, Transennella, 8, 10

Tellina buttoni, 3t, 9, 15, 18

tenuis, Diastylopsis, 17t

tenuisculpta, Parvilucina, lOt

Terebra pedroana, 35a

tertia, Oxyurostylis, lit, 33a

Tharyx parvus, 18, 20, 22

Trachycardium quadragenarium, lOt

traskiana, Orchestia, 35a

Transennella tantilla, 8, 10

FTricolia sp., 9t

Trypanosyllis gemmipara, lOt

tubularis, Cerapus, 19t

Tunicata, tunicate, see Eugyra glutinans

Turbellaria, 16t, 33a

Turbonilla sp., 35a

Typosyllis variegata, 11, 13

ubiquita, Munna, 9t

uenoi, Corophium, 11, 20

uncata, Polydora, 11, 17t

uncirostratus, Mandibulophoxus, 17t

Uristes entalladurus, 9

valida, Stenothoe, 20

variegata, Typosyllis, 11, 13

verugera, Exogone, 3t, 5, 7, 8,9, 10, 11, 13, 18, 22

williamsi, Anaitides, 18

yoldiformis, Macoma, lOt

Zostera marina, 4, 5, 6, 7, 8, 9, 13, 18, 19, 23, 26, 27, 28

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