University of Alaska 

Coastal Marine Institute 

Kachemak Bay Experimental and Monitoring Studies: 

Recruitment, Succession, and Recovery in 

Seasonally Disturbed Rocky-Intertidal Habitat 

Raymond C. Highsmith, Principal Investigator 

Susan M. Saupe 

Arny L. Blanchard 

University of Alaska Fairbanks 

Final Report 

August 2001 

OCS Study MMS 2001-053 
CMI contact information 

E-mail: cmi@sfos.uaf.edu 

Phone: 907.474.7707 

Fax: 907.474.7204 

Postal: Coastal Marine Institute 

School of Fisheries and Ocean Sciences 

University of Alaska Fairbanks 

Fairbanks, AK 99775-7220 

This study was funded in part by the U.S. Department of the Interior, Minerals Management Service 

(MMS). through Cooperative Agreement No. 14-35-0001-30661. Task Order No. 11982, between the 

MMS, Alaska Outer Continental Shelf Region, and the University of Alaska Fairbanks. 

The opinions, findings, conclusions, or recommendations expressed in this report or product are those 

of the authors and do not necessarily reflect the views of the Minerals Management Service, nor does 

mention of trade names or commercial products constitute endorsement of recommendation for use 

by the Federal Government. 
OCS Study MMS 2001-053 

Final Report 

Kachemak Bay Experimental and Monitoring Studies: 

Recruitment, Succession, and Recovery in Seasonally Disturbed 

Rocky-Intertidal Habitat 

Raymond C. Highsmith 

Susan M. Saupe 

Arny L. Blanchard 

School of Fisheries and Ocean Sciences 

University of Alaska Fairbanks 

Fairbanks, AK 997757220 

August 2001 
Project Organization 

Report Authors: 

Raymond C. Highsmith - Principal Investigator 

Susan M. Saupe 

Amy L. Blanchard 

Data Collection, Data Analyses and Data Entry: 

Tracy Asselin 

Catherine Egan 

Stephanie Moreland 

Tama Rucker 

Steve Sklavounos 

Paul Will 

Jennifer Trask 

Pat Jacobson 

Gretchen Saupe 

Algal Voucher Collection: 

Mandy Lindeberg 

Lauren McCarty 

Budget Management: 

David Doudna 

Computer Support: 

Michelle Bourassa 

Chirk Chu 
Table of Contents 

.. Project Organization ................................................................................................................. 11 

List of Tables ........................................................................................................................... iv 

List of Figures .......................................................................................................................... v 

Executive Summary .................................................................................................................. 1 

Introduction ............................................................................................................................. 3 

Purpose ................................................................................................................................ 3 

Background and need ........................................................................................................... 3 

Goals and objectives ......................................................................................................... 4 

Methods .................................................................................................................................... 5 

Definitions ........................................................................................................................... 5 

Study area ............................................................................................................................ 5 

Site selection ..................................................................................................................... 6 

Transect and quadrat locations .............................................................................................. 7 

Quadrat treatments ............................................................................................................... 8 

Quadrat data collections ..................................................................................................... 10 

Data analyses ..................................................................................................................... 13 

Univariate methods (individual taxonomic group analyses) ...................................... 13 

Multivariate methods (community level analyses) .................................................... 14 

Results .................................................................................................................................... 15 

General descriptive patterns ................................................................................................ 15 

Univariate analyses (individual taxonomic group analyses) ................................................ 29 

Multivariate analyses (community level analyses) .............................................................. 44 

Discussion .............................................................................................................................. 55 

Conclusions ........................................................................................................................... 60 

Acknowledgements ................................................................................................................. 62 

Study Products ........................................................................................................................ 62 

References ............................... y. ............................................................................................. 63 

iii 
List of Tables 

Table 1. 

Table 2. 

Table 3. 

Table 4. 

Table 5. 

Table 6. 

Table 7. 

Table 8. 

Table 9. 

Table 10. 

Table 1 1. 

Table 12. 

Site codes, latitude, longitude, and general descriptive location of the 

eight recruitment and succession study sites ............................................................................... 7 

Dates and locations of control and scraped quadrats at the study sites .................................... 10 

Dates when invertebrate and algal data were collected from the study sites ........................... 11 

Algal voucher specimens collected from intertidal zones in the general 

study area of outer Kachemak Bay ............................................................................................ 12 

Summary of repeated measures ANOVA comparisons for adult Balanus 

(Semibalanus balanoides + Balanus glandula) percent cover data at MVD 1.5 ..................... 30 

Summary of repeated measures ANOVA comparisons for adult Balanus 

(Semibalanus balanoides + Balanus glandula) percent cover data at MVD 2.5 ..................... 3 1 

Summary of repeated measures ANOVA comparisons for adult 

Semibalanus cariosus percent cover data at MVD 3.5 .......................................................... 34 

Summary of repeated measures ANOVA comparisons for Fucus gardneri 

percent cover data at MVD 1.5 ................................................................................................ 35 

Summary of repeated measures ANOVA comparisons for Fucus gardneri 

percent cover data at MVD 2.5 ................................................................................................ 36 

Summary of repeated measures ANOVA comparisons for Alaria spp. 

percent cover data at MVD 3.5 ........ . ........ .. . . ... ... .... ... . . . ... . . . . . . . . . ....... . ........ . . . . . . 39 

Summary of repeated measures ANOVA comparisons for Mytius trossulus 

percent cover data at MVD 1.5 ............................................................................................. 40 

Summary of repeated measures ANOVA comparisons for Mytilus trossulus 

percent cover data at MVD 2.5 ............................................................................................... 43 
List of Figures 

Figure 1. 

Figure 2. 

Figure 3. 

Figure 4. 

Figure 5. 

Figure 6. 

Figure 7. 

Figure 8. 

Figure 9. 

Figure 10. 

Figure 1 1. 

Figure 12. 

Figure 13. 

Figure 14. 

Figure 15. 

Figure 16. 

Study site locations for the Kachemak Bay intertidal experimental and 

monitoring study ........................................................................................................................ 6 

Schematic cross-section of a site showing the locations of meter vertical drops 

(MVDs) relative to each other and to mean higher high water (MHHW) ................................. 8 

Schematic of study site layouts .................................................................................................. 9 

Mean dissolution rate of calcium sulfate cylinders deployed at the 2.5 meter 

vertical drop on study sites in August and October 1994 ........................................................ 14 

Mean percent cover of barnacle spat in scraped and control quadrats at each 

site measured in July 1995 and September 1996 ....................................................................... 17 

Mean percent cover of Balanus (Balanus glandula + Semibalanus balanoides) in 

scraped and control quadrats at each site measured in July 1995 and September 1996 .......... 18 

Mean percent cover of Semibalanus mriosus and Alaria spp. in scraped 

and control quadrats at each site measured in July 1995 and September 1996 ........................ 19 

Mean percent cover of Funts gardneri in scraped and control quadrats 

at each site measured in July 1995 and September 1996 ......................................................... 20 

Contribution of major intertidal species to total cover within quadrats in July 1995 .............. 22 

Contribution of major intertidal species to total cover within quadrats 

in September 1996 ...................................................................................................................... 23 

Mean total percent cover of all invertebrates and algae in scraped and 

control quadrats at sheltered site BB .................................................................................. 24 

Mean total percent cover of all invertebrates and algae in scraped and 

control quadrats at wave exposed site HI ................................................................................. 25 

Densities (individuals mP2) of Littorina sitkana and L. snrtulara averaged 

across all sites ............................................................................................................................. 26 

Densities (individuals m-') of limpets averaged across all sites .............................................. 27 

Densities (individuals m-') of the limpet Tectura snrtum and the chiton 

Katharina tunicata at MVD 3.5 across all sites ...................... , ................ .. ............................ 28 

Linear regressions of percent cover data collected in July 1995 using 

"surface" and "3-D" data collection methods ........................................................................... 29 
Figure 17. 

Figure 18. 

Figure 19. 

Figure 20. 

Figure 2 1. 

Figure 22. 

Figure 23. 

Figure 24. 

Figure 25. 

Figure 26. 

Figure 27. 

Figure 28. 

Figure 29. 

Figure 30. 

Figure 3 1. 

Mean total percent cover of Semibalanus balanoides + Balanus glandula at MVDs 

1.5 and 2.5 and S. cariosus at MVD 3.5 in scraped and control quadrats at site BB ............... 32 

Mean total percent cover of Semibalanus balanoides + Balanus glandula at MVDs 

1.5 and 2.5 and S. cariosus at MVD 3.5 in scraped and control quadrats at site HI ................ 33 

Mean total percent cover of Fucus gardneri at MVDs 1.5 and 2.5 and 

Alaria spp. at MVD 3.5 in scraped and control quadrats at site BB ........................................ 37 

Mean total percent cover of Fucus gardnen at MVDs 1.5 and 2.5 and 

Alaria spp. at MVD 3.5 in scraped and control quadrats at site HI .......................................... 38 

Mean total percent cover of Mytilus trossulus in scraped and control quadrats 

at site BB ..................................................................................................................................... 41 

Mean total percent cover of M@lus trossulus in scraped and control quadrats 

at site HI ..................................................................................................................................... 42 

Example of coding for multi-dimensional scaling .................................................................... 45 

Multi-dimensional scaling ordination of July 1995 multi-species data 

fiom control and scraped quadrats at eight sites .................................................................... 46 

Multi-dimensional scaling ordination of September 1996 multi-species data 

fiom control and scraped quadrats at eight sites ....................................................................... 47 

MDS ordination of July 1995 multi-species data from MVD 1.5, 

redrawn fiom Figure 24 ............................................................................................................ 49 

MDS ordination of July 1995 multi-species data fiom MVD 2.5, 

redrawn fiom Figure 24 .............................................................................................................. 50 

MDS ordination of July 1995 multi-species data fiom MVD 3.5, 

redrawn from Figure 24 ............................................................................................................. 5 1 

MDS ordination of September 1996 multi-species data from MVD 1.5, 

redrawn fiom Figure 25 ......................................................................................................... 52 

MDS ordination of September 1996 multi-species data fiom MVD 2.5, 

redrawn fiom Figure 25 .............................................................................................................. 53 

MDS ordination of September 1996 multi-species data fiom MVD 3.5, 

redrawn fiom Figure 25 ............................................................................................................. 54 
Executive Summary 

The purpose of this study was to establish a multi-year sampling program in rocky-intertidal assemblages 

of outer Kachemak Bay and to assess recruitment and successional patterns leading to recovery of 

selected intertidal species and the intertidal community after seasonal disturbances. The specific 

objectives were to: 

1. Determine whether the season in which a disturbance takes place affects recovery 

rates or succession processes. 

2. Quantify inter- and intra-annual abundance patterns for major species. 

3. Determine the effect of wave exposure on community structure and response to 

seasonal disturbances. 

The study was initiated in response to questions raised during injury assessment studies following the 

Exron Valdez oil spill pighsmith et al. 19943. Several organisms showed increased numbers or percent 

cover in oiled compared to unoiled rocky-intertidal habitat. Data were not available to determine if these 

increases were correlated with the time of year that space had become available, due either to the oil or to 

subsequent clean-up activities, and thus reflecting timing of reproduction or recruitment for some species 

but not others. The responses of the various invertebrates and algae to the oil spill differed by species, 

tidal height, region, habitat, and wave exposure as reflected by increases, decreases, or no change to 

abundance, biomass, or percent cover. Rates of recovery, or convergence with control sites, also differed 

among the numerous taxa and depended upon the above variables. Another question raised was whether 

there were inherent differences between oiled and control sites, based on the prevailing currents that 

carried oil to the impacted sites. A lack of pre-spill intertidal data necessitated the comparison of oiled 

shorelines to unoiled control beaches for all of the intertidal injury and restoration studies [Gilfillan et al. 

1995; Houghton et al. 1993; Highsmith et al. 19941. With data for the major space-occupying species, 

Highsmith et al. [I9941 used the multi-dimensional scaling (MDS) method to evaluate recovery of 

invertebrate and algal communities on rocky substrates. Their results showed that site exposure to waves 

explained the ordinations and oiling category did not. Kachemak Bay rocky-intertidal communities have 

been generally surveyed and have some similarities to lower-latitude west coast communities that have 

been more intensively studied. However, extrapolation of the lower-latitude results to southcentral Alaska 

is not appropriate as certain key intertidal species are not present or occur in very low abundances in 

Kachemak Bay. In Alaska, physical extremes, such as temperature and photoperiod, are greater and many 

species are at their northern geographical limit. In fact, some of the major community-structuring species 

in the Pacific Northwest do not occur in the Kachemak Bay intertidal zone, e.g., Mjdw califomianus, 

or are in such low densities, e.g., Pisaster ochraceus, that they have little role in community dynamics. 

Studies in lower-latitude west coast areas have shown effects of season on population dynamics and 

recovery rates after disturbances in rocky-intertidal habitat [Kinnetic Laboratories, Inc. 1992; Minerals 

Management Service 1996; Kim and DeWreede 19961. In Alaska, seasonal effects may be a primary 

factor in determining recovery rates. Generally, information on inter- and intra-annual variability in 

Alaskan intertidal communities is lacking. This report contains results fiom a study in outer Kachemak 

Bay to provide multi-year data on rocky-intertidal assemblages and to assess recovery and successional 

patterns after seasonal disturbances. 

In this study, experimental disturbances in different seasons and over a range of wave exposures were 

used to assess recruitment and succession patterns during recovery in rocky-intertidal habitat sites. To 

simulate seasonal environmental disturbances, quadrats at three tidal heights at eight sites were cleared 

of all invertebrates and algae during March, July and October 1994, and March 1995. These dates were 

selected to provide potential settlement sites (bare rock) for organisms that recruit in different seasons. 

Undisturbed control quadrats were also established to provide data on inter- and intra-annual variability 

of dominant invertebrates and algae and for comparative statistical analyses of degree of recovery of 
disturbed plots. The eight study sites were selected to represent a range of wave exposures from highlysheltered to fiequently-impacted by storm waves. Sites were surveyed, and quadrats were established, 

cleared, and subsequently monitored for organism abundance andlor percent cover. Sampling dates 

were July 1995, October 1995, June 1996, and September 1996. Data were analyzed using two main 

approaches. First, dominant or key invertebrates and algae were analyzed across time using repeatedmeasure ANOVAs (rmANOVA) to assess the effects of site and disturbance date. To assess recovery of 

the intertidal community, a multivariate technique, multi-dimensional scaling, was used. This method 

plots multi-species, multi-sample data sets on a two-dimensional graph such that the rank ordering of the 

sample distances agrees with the rank order of distances fiom a dissimilarity matrix. The ordination gives 

a visual representation of the similarity or dissimilarity of species composition between samples [Clarke 

and Warwick 19941. Ordination gradients were then used to evaluate the importance of environmental 

variables in recovery dynamics fiom the disturbance. 

This study showed that time of disturbance relative to seasonal reproductive events of major spaceoccupying species affected the time required for recovery. Summer and fall disturbances took longer 

to recover fiom than spring disturbances because the latter occurred just prior to the peak of barnacle 

larval settlement. Therefore, early barnacle recruitment appears to be a critical element in recovery rates. 

Although this three-year study provides a data and knowledge base for continued work, this project was 

not long enough for all end-points to be reached. A primary recommendation is that long-term, i.e., 

5-1 0 years, monitoring of experimentally disturbed sites is needed in Kachemak Bay in order to fblly 

understand the specific events and timecourse of recovery from seasonal disturbances. 

In control quadrats, the community remained relatively stable throughout the study, although some 

intra-annual variability was detected due to life histories, such as in annual algae. The acorn barnacles, 

Sernibalanus balanoides and Balanus glandula, were the first to colonize the disturbed quadrats in the 

high (1.5 meters of vertical drop below mean higher high water) and mid (2.5 MVD) intertidal zones, 

often with > 80% cover. Adult percent cover of these species remained above control quadrat levels at 

the end of the study, suggesting stability had not yet been achieved. The dominant alga in the mid to 

upper intertidal zone, Fucus gardneri, colonized disturbed plots only after the above barnacle species 

were established and had not returned to control levels at the end of the study except in quadrats that 

had 2.5 years to recover. A similar scenario occurred for the dominant algal and barnacle species in the 

low intertidal zone (3.5 MVD). Recruitment of the kelp Alaria spp. followed recruitment by the barnacle 

S. cariosus, and neither had recovered to control levels by the end of the study. The blue mussel M@Iu 

trossulus which also appears to recruit in large numbers only after barnacles have become established, 

had not recovered by the end of the study and the data indicate that much longer than 2.5 years may 

be required for recovery at wave-exposed sites. Generally, recovery rates within quadrats scraped on 

different dates were driven by the seasonal timing of barnacle recruitment relative to the date of scraping 

(bare rock substrate availability). 

Multi-dimensional scaling showed that scraped quadrats had not llly converged with control quadrats 

by the last sampling date, 30 months after the first set of quadrats was scraped in March 1994. Recovery 

rates varied by the season that quadrats were scraped. Quadrats scraped in July and October 1994 showed 

slower recovery rates than quadrats scraped in March 1994 or 1995. The dissimilarities of scraped 

quadrats compared to control quadrats were reduced between July 1995 and September 1996, suggesting 

community recovery was in progress but just not complete after 2.5 years. Although there were 

recruitment differences for some species between protected and exposed sites, wave exposure as a matrix 

variable did not account for community-level differences in recovery. 
Introduction 

Purpose 

The purpose of this study was to establish a multi-year sampling program in rocky-intertidal assemblages 

of outer Kachemak Bay and to assess the recovery and successional patterns of intertidal organisms 

after seasonal disturbances. The information obtained during this project will 1) support environmental 

assessment processes for Cook Inlet and Gulf of Alaska lease sales, 2) help in the decision-making 

process during shoreline response operations in the event of an oil spill, and 3) increase the ability to 

monitor recovery in the event of an oil spill in Cook Inlet. 

Backgroundandneed 

Cook Inlet shorelines include numerous habitats such as marshes, sheltered and exposed tidal flats, coarse 

textured beaches, and sheltered and exposed rocky habitats. The unique combination of tidal currents, 

upwelling, the Alaska Coastal Current, and freshwater inputs creates a well-mixed tidal estuary that 

supports high biological productivity, exemplified by the extremely productive rocky shorelines of outer 

Kachemak Bay mosenthal and Lees 1976; Lees and Houghton 1977; Lees et al. 1980; Carroll 1994; 

Highsmith et al. 19941. These shorelines contain diverse and rich invertebrate and algal assemblages and 

include state park lands, a state critical habitat area, and a national estuarine research reserve. Although 

not immediately adjacent to the active lease sales and oil industry operations in Cook Inlet, these rocky 

shores are still at risk from accidental releases of oil fiom tankers transiting the inlet, pipeline fractures, or 

well blow-outs. Depending upon prevailing winds and currents, oil could be carried fiom remote release 

points to almost any shoreline within Cook Inlet, including Kachemak Bay. In fact, in February 1999, 

the oil tanker Potomac Trader was towed to outer Kachemak Bay after a hairline fracture of its hull was 

caused by ice in the inlet. Oil trajectory models indicated that if significant oil had leaked fiom the ship, 

the path would take the oil directly south onto the rocky shorelines included in this study. Extensive overflights of the area detected no oil hitting the shorelines. This incident, however, highlights the potential 

value of the baseline data presented in this report. 

Intertidal communities are especially vulnerable to spilled oil due to their location at the interface 

between marine waters and the shoreline where incoming tides and prevailing currents may strand 

floating oil. Once ashore, stranded oil can impact intertidal communities as a direct result of oiling or 

indirectly due to subsequent clean-up efforts. Intertidal impacts can include immediate death fiom oiling 

or response efforts; sub-lethal effects such as failure to molt, swim, feed, or reproduce; and reductions in 

fertility, recruitment success, or growth rates. Changes to one intertidal species can directly or indirectly 

affect other organisms wage 19951. One indirect effect of an oil spill, reduced cover or shelter due to 

the loss of attached intertidal organisms, can be most dramatic at rocky shores compared to other habitats 

[Gilfillan et al. 19951. Rocky shores act as buffers to upland habitat, provide habitat for a variety of plant 

and animal species that require hard substrate, and are important habitats for a diverse association of 

marine species [Dobroski and Bogardus 19901. 

The intertidal community was the largest habitat category affected by the Exxon Valda oil spill (EVOS), 

with damage from the oil and resultant cleanup activities occurring over several hundred kilometers of 

shoreline. Several EVOS studies conducted within rocky-intertidal habitat after the oil spill reported 

varying levels of injury and recovery in key organisms, including Fucus gardneri (the major structural 

component of rocky-intertidal communities in southcentral Alaska), limpets, litto~es, and barnacles 

[Houghton et al. 1993,1996; DeVogelaere and Foster 1994; Highsmith et al. 1994; Gilfillan et al. 1995; 

Highsmith et al. 20001. In contrast, some organisms showed significantly increased numbers or percent 

cover on oiled sites compared to control sites, perhaps due to lack of competitors or predators. Recovery 

is occurring or has occurred in the low and mid intertidal zone for most organisms. The longest on-going 

intertidal study conducted after the EVOS describes the onset of recovery as occurring within the first 
several years after the spill [Coates et al. 19991, with most major intertidal assemblages having recovered 

within six years. However, a series of studies conducted in Herring Bay in Prince William Sound showed 

that F. gardneri and several grazing invertebrates continued to show reduced densities relative to control 

sites on oiled upper intertidal shorelines up to six years after the oil spill [Stekoll and Deysher 1996; van 

Tamelen and Stekoll 1996; Highsmith et al. 20003. 

Pre-spill data did not exist for the intertidal studies conducted after the EVOS to estimate injury to 

invertebrates and algae and, thus, oil effects had to be estimated from a comparison of oiled and non-oiled 

areas. Information on intertidal community structure and patterns would have made damage and recovery 

studies much more time and cost efficient. The statistical advantage of collecting pre-spill data, as 

opposed to using a post-spill matched-pair design, is that inherent physical, geological and biological 

differences between paired sites would not be factors in the analyses. These examples illustrate the 

recommendations by intertidal researchers to establish reference sites in areas where the potential for oil 

spills exists mawkins and Hartnoll 1983; Hiscock 1985; Dobroski and Bogardus 19901. In addition to 

pre-spill data collections, multi-year data collection is necessary to describe seasonal and inter-annual 

fluctuations and trends in community structure. This information can aid in determining whether changes 

in the community are due to pollution or natural disturbances. For example, a major die-off in the mid to 

upper intertidal zone due to freezing was reported in southcentral Alaska just weeks prior to the EVOS 

[Carroll 19941. 

Pacific coast studies south of Alaska have assessed various aspects of disturbances on recruitment, 

recovery, and successional patterns on rocky-intertidal shorelines. Foster et al. [I9861 reviewed 

disturbances in rocky-intertidal communities in the northeastern Pacific and the processes that might 

affect impacts at various spatial and temporal scales. Much of the variation in patterns of distribution 

and abundance of intertidal organisms was attributed to disturbances that removed portions or entire 

assemblages of epibenthic communities. A subsequent series of studies was conducted that looked at 

disturbances to, and recovery of, rocky-intertidal sites during different times of the year along a latitudinal 

gradient from central to northern California [Kinnetic Laboratories, Inc. 1992; Minerals Management 

Service 19961. The disturbances were created by removing intertidal organisms and the researchers found 

that recovery rates varied by tidal height or assemblage, with upper intertidal zone recovery occurring in 

as little as one year while lower intertidal mussel beds were estimated to take at least ten years to recover. 

Recovery rates were slower for assemblages that were disturbed in the fall compared to those disturbed in 

the spring. Recovery rates were not significantly correlated with latitude. 

Kachemak Bay rocky-intertidal communities are biologically productive and, in many ways, are similar 

to those of California, Oregon, Washington, and British Columbia [Carroll 1994; Pentec Environmental 

Inc. 19961. Studies in these areas have shown effects of season on population dynamics and on 

recovery rates after disturbances in rocky-intertidal habitat [Kinnetic Laboratories, Inc. 1992; Minerals 

Management Service 1996; Kim and DeWreede 19961. Physical extremes related to latitude, such as 

temperature and photoperiod, are greater in Alaska than further south, suggesting that seasonal effects 

would be even greater in determining recovery rates for rocky-intertidal communities in Alaska, 

especially because many species are at or near their northern geographical limit. For Alaska, there is 

a lack of postdisturbance data on inter- and intra-annual variability of recovery rates and patterns for 

intertidal invertebrates and algae. This study established a multi-year sampling program in rockyintertidal assemblages and assessed their recovery and successional patterns after experimental seasonal 

disturbances. 

Goals and objectives 

The goals of this study were 1) to establish reference sampling sites that can provide baseline information, 

including inter- and intra-annual variability, for intertidal habitats in southcentral Alaska; and 2) to 
evaluate seasonal influences on recovery rates for a range of wave exposures. This information will 

aid in estimating expected recovery rates for disturbances that occur during different times of the year. 

For rocky-intertidal habitats in outer Kachemak Bay, the specific objectives of the study were to: 

1. Determine whether the season in which a disturbance takes place affects recovery or 

succession processes. 

2. Quantify inter- and intra-annual abundance patterns for major species. 

3. Determine the effect of wave exposure on community structure and response to 

seasonal disturbances. 

Methods 

Definitions 

In this study, disturbance is defined as any discrete event that reduces the amount of living biomass in an 

area and opens up space for the establishment of new individuals or colonies [Kim and Dewreede 19961. 

Recovery is the point when population- or community-level variables measured in disturbed areas are not 

significantly different from those of undisturbed or control areas. Succession is the sequence of changes 

in community structure that occurs after a site has been disturbed Derlow 19971. Recruitment includes 

both settlement and survival and, for a given species, includes the smallest recognizable individual 

[Carroll 1 9941. 

Study area 

The study area is located in outer Kachemak Bay on the eastern side of Cook Inlet, Alaska (Figure 1). 

The semi-diurnal tidal range in the area averages more than five meters, making spring tides some of 

the largest in the world. Field crews used lodging and laboratory facilities at the University of Alaska 

Fairbanks' Kasitsna Bay Laboratory. All of the sites were accessed by boat. 

Kachemak Bay was selected for this study for several reasons: it has extreme seasonal variations in air 

temperature, wind-induced waves, and solar radiation; it is near or at the northern geographical limit 

of many intertidal species; it has high biological productivity in the intertidal zone; the beaches are 

accessible and close to the Kasitsna Bay Laboratory; and there is public and agency interest in the area 

due to its proximity to oil transportation routes and production sites. 

The upper intertidal zone of rocky substrates in the area is dominated by the rockweed Fucus gardneri 

and the acorn barnacles Semibalanus balanoides and Balanus glandula. Grazing invertebrate populations 

are dominated by the periwinkle snail Littorina sitkana. The most common limpet in the area is Lottia 

pelta, although L. digitalis is also common among barnacle tests. 

The diversity of the mid intertidal community is greater than that of the upper intertidal zone. The blue 

mussel Mytillus trossulus is more abundant, as is the thatched barnacle Semibalanus cariosis. Funrs 

gardneri is still abundant and red algae are more common, dominated by Odonthaliafloccosa. The green 

algae, Acrosiphonia sp., Ulva sp. and Monostroma sp., are also abundant. 

The brown algae Alaria spp. is the dominant overstory component in the low intertidal zone, especially 

at exposed sites. The dominant barnacle is Semibalanus cariosus. The most abundant herbivores are the 

limpets (Lottiidae), mainly Lottiapelta and Tectura scutum, but the black chiton Katharina runicata 

dominates in some areas. 
Figure 1. Study site locations for the Kachemak Bay intertidal experimental and monitoring 

study. Note that the sites BB, LB, C1, C2, and HI are located on islands, while 

sites KB, JB, and SB are located on the mainland of the Kenai Peninsula. 

Site selection 

Sites were selected to represent rocky substrates typical of the area and to include a range of wave 

exposures. The field team surveyed the shorelines around the mainland and islands in outer Kachernak 

Bay in an area bounded by McDonald Spit and the outermost islands to the west, Yukon Island to 

the north, the entrance to Tutka Bay to the east, and Kasitsna and Jakolof Bays to the south (Figure 1, 

Table 1). Much of the shoreline was too steep for safe field work or had coarse-textured beach below 

the mid intertidal zone, thus limiting the length of shoreline available for the study. The selected sites 

ranged from highly wave-exposed shorelines (Hesketh Island) to the most wave-sheltered sites (Jakolof 

and Kasitsna Bays). The relative ranking of wave exposure for the sites was defined by personal 

observations, the direction and length of the fetch for prevailing storm waves, and dissolution rates of 

calcium sulfate cylinders (see below). Wave exposure among the sites ranged from being subjected to 

waves several meters high during storms to total protection from waves. Sites were observed over the 

two and a half years of the study to verify the original subjective ranking by wave exposure. 

Dissolution rates of calcium sulfate cylinders were used to estimate relative water movement at the eight 

sites spanning a range of wave exposures. Dissolution of the calcium sulfate cylinders is a function of 

the rate at which water moves past the cylinders, and thus is a function of wave, tide, and wind-driven 

currents. Dissolution cylinders were constructed from commercially available calcined gypsum (calcium 

sulfate). Gypsum powder was mixed with water, stirred, and poured into molds made from PVC pipe. 

A large screw was inserted through the center so that the head was flush with the surface of the calcium 

sulfate at one end of the mold and the pointed tip of the screw protruded at least one inch from the other 

end. The molds were removed after the mixture had set (1 to 1.5 hours), and rough seams were smoothed 
with a razor blade. The cylinders were dried overnight at 40°C. Waterproof epoxy was applied to both 

ends of each cylinder (without covering the screw head) to prevent dissolution from the ends and to allow 

for a radially symmetrical surface for dissolution. A numbered tag was embedded in the epoxy on the top 

of each cylinder. They were then re-dried for 48 hours at 40°C, placed in a desiccator to cool and weighed 

to the nearest 0.001g. Cylinders were deployed at the 2.5 m vertical drop (h4VD) below mean higher high 

water (MHHW) at each transect on all eight sites. To deploy the cylinders, screw anchors were drilled 

into the rock substrate and the cylinders were screwed directly into the anchors, positioning them directly 

above the substrate. Cylinders remained deployed for several days, depending upon weather conditions. 

After collection, they were dried and weighed. The difference in weight of each cylinder is a relative 

measure of the rate of water movement past the cylinder muus 1968; Gerard 1982; Petticrew and Kalff 

19911. 

Table 1. Site codes, latitude, longitude, and general descriptive location of the eight recruitment 

and succession study sites. 

Site Latitude 

BB 59O29.883' 

Longitude General Location 

151 "30.967' North side on the southernmost of the Hemng Islands 

151°31.317' Northwest comer on the northernmost of the Hemng Islands 

151 "31.033' Southwest corner on the northernmost of the Hening Islands 

151 "31.350' North side of Hesketh Island 

151 "31 -550' East side of Jakolof Bay 

151 "33.600' South side of Kasitsna Bay 

151"30.000' South side on the easternmost of the Hening Islands 

151 "29.133' Just outside the mouth of Tutka Bay on the south side 

Transect and quadrat locations 

Stretches of rocky-intertidal habitat between 25 m and 100 m in length were measured at each of the eight 

selected sites. The shoreline was disjunct at several sites and a total of 100 m was attained by combining 

rocky shorelines encompassing coarse-textured pocket beaches. To establish transects perpendicular 

to the shore, the mean hijjher high water line was estimated based on a commercial tidal program, the 

location of the upper edge of the barnacle zone and the lower edge of the Vewucaria (a black lichen) zone 

above the barnacles. The interface between the Vmcaria and barnacle zones is a good indicator of 

MHHW mighsmith et al. 19941. To determine transect placement, the site length was divided by four and 

the resulting distance was multiplied by a random number less than 1.0. The first transect was located that 

distance from the left end of the defined beach. The other three transects at the site were placed one fourth 

of the total beach length apart to the right (facing shore) of the first transect, excluding any pocket beaches. 

Three permanent 0.1 m2 quadrats were established at 1.5,2.5, and 3.5 MVD below the MHHW line 

(Figure 2). A surveyor's sight level was used to determine the MVD locations. To mark quadrat locations, 

stainless steel screws were secured in holes drilled in the rocks at the upper-right and lower-left comers 

of each quadrat. A numbered plastic tag was attached to one of the screws. Permanently marking the 

quadrats enabled exact positioning of the quadrat fkme on return visits. 
Figure 2. Schematic cross-section of a site showing the locations of meter vertical drops 

(MVDs) relative to each other and to mean higher high water (MHHW). The 

MVDs were determined with a surveyor's sight level. 

Quadrat treatments 

Experimental "disturbed" quadrats were created in March, July, and October 1994, and March 1995 by 

scraping away all invertebrates and algae, including tests and holdfasts of dead organisms. A lO-cm 

border was cleared around each quadrat to reduce migration problems. After physical removal of all 

organisms, the quadrats and border were burned with a propane torch to ensure removal of the smallest 

recruits or algal eggs. Finally, bleach was squirted into cracks to ensure that no Fum gardneri eggs 

would survive. Control quadrats, in which no organisms were removed, were permanently established in 

March 1994. For control quadrats, the left edge of the quadrat fi-ame was placed along the transect line 

centered at the 1.5,2.5, and 3.5 MVDs (Figure 3). The March 1994 scraped quadrats were placed one 

meter to the left of the control quadrats. Subsequent scraped quadrats, made in July 1994, October 1994, 

and March 1995, were placed one meter to the left of the previously scraped quadrats. The dates for 

clearing quadrats were chosen to reflect different seasons: March 1994 was selected to provide space 

for spring-recruiting organisms; July 1994 was chosen to provide space for species that recruit in late 

summer or fall; October 1994 was selected to provide bare space for recruitment occurring during the 

winter or in early spring before the next March scrapes were made; and March 1995 was selected to 

provide a measure of inter-annual variability when compared to the March 1994 quadrats. By March 

1995, there were 60 quadrats on each site (four transects x three MVDs x five treatments), with 

exceptions as noted below (Table 2). 
MHHW 

MVD 1.5 

MVD 2.5 

MVD 3.5 

March 95 October 94 July 94 March 94 

Figure 3. Schematic of study site layouts. Quadrats are one meter apart. MVD = meter vertical drop 

fiom mean higher high water (MI-IHW). The dates below each quadrat indicate when the 

quadrat was scraped. A 10-crn boundary was scraped outside of each 3 1.6 x 3 1.6 cm quadrat. 

After the first visit to the Jakolof Bay (JI3) site we removed its MVD 3.5 quadrats fiom the study because 

fine sediments collected on the rocky substrate and in crevices and precluded the recruitment of hardsubstrate organisms. Sites JI3 and Kasitsna Bay (KB) were relatively narrower and lacked sufficient 

length to scrape quadrats in March 1995 without interfering with the established control quadrats. Thus, 

no March 1995 quadrats were scraped on these sites. After initially establishing four transects at the Tutka 

Bay site (SB), Transect 3 was dropped fiom the study because the substrate was generally cobble and too 

different fiom the rest of the site and other sites for comparative purposes. Table 2 lists total transects and 

quadrats at each of the eight sites. 
Table 2. Dates and locations of control and scraped quadrats at the study sites. MVD = meter 

vertical drop. An X means that quadrats were established at that site and MVD for 

the number of transects listed. 

Numberof MVD Date Quadrats Scraped 

Tramects Control March 94 July 94 October 94 March 95 

Quadrat data collections 

Quadrats were revisited to collect recruitment and succession data after they were scraped, with the 

main data collection efforts made after the final scraped quadrats were created in March 1995. A nondestructive sampling procedure was necessary for monitoring quadrats through time. Two different pointcontact methods were used for collecting percent cover data. The first method was used to perform rapid 

assessments in control and scraped quadrats. A 36-point, evenly spaced grid within the 3 1.6 cm x 3 1.6 cm 

quadrat frame was placed over each quadrat and aligned with the rock screws. The organisms directly 

beneath each of the 36 grid points were identified and recorded. Only overstory organisms, or bare rock, 

visible directly beneath the grid point without disturbing the substrate were recorded. Although this 

method misses understory organisms, it was used when the sampling team was establishing new scraped 

quadrats and did not have time for more detailed counting. 
A more thorough, point-contact method was employed after the last quadrats were scraped in March 

1995. A 36-point, evenly-spaced grid within a 3 1.6 an x 3 1.6 crn frame was aligned over each quadrat. 

The organisms beneath each grid point were identified vertically through all layers. Overstory, midstory, 

and understory organisms were all sampled, providing a 3-dimensional view of the complex intertidal 

community [Foster et al. 19911. Data were collected using this method in July 1995, October 1995, June 

1 996, and September 1996 (Table 3). 

Table 3. Dates when invertebrate and algal data were collected from the study sites. An (X) 

signifies data collections made on a limited set of sites or using abbreviated methods. 

An X signifies data collected using the 3-D percent cover methods that sample 

vertically through the intertidal assemblages. The shaded area represents data that is 

presented in this report for the recruitment and successions study. Data represented 

by the non-shaded area were used for methods comparisons. 

Date Data Collected Control March 94 July 94 October 94 March 95 

March 1994 (x) 

July 1994 (XI (XI 

October 1994 ()o o() (XI 

March 1995 

July 1995 X X X X X 

October 1995 X X X X X 

June 1996 X X X X X 

September 1996 X X X X X 

For data collected using the 3-D method, total percent cover greater than 100% can occur if all points 

are summed for all species. Organisms often occur in layers and each grid point could have more than 

one organism recorded as being directly beneath it. Therefore, we calculated total percent cover of all 

organisms based on percent of bare rock present. Percent bare rock is the percent of grid points under 

which no organisms occurred and is a measure of available, or unoccupied, space. Total organism percent 

cover was calculated by subtracting the number of grid points where bare rock occurred fiom 36, dividing 

the remainder by 36 then multiplying by 100. This value is referred to as "total percent cover". 

Most invertebrates and algae were recorded at the species level in the field, with the following exceptions: 

The barnacles Semibalanus balanoides and Balanus glandula are difficult to differentiate in the field, 

especially when covered with algae. These two barnacles occupy similar ecological niches [O'Clair and 

Zimrnerman 19871 and are treated together in this study. The green filamentous algae, Acrosiphonia sp. 

and Cladophora sp., are very similar morphologically and were combined as one taxonomic group. 

Melanosiphon intestinalis and Scytosiphon Iomentaria were also treated as one taxonomic group. 

Porphyra spp. were identified to the genus level in the field. Palmaria species were combined for 

analyses, as were Odonthalia species. 

Algal vouchers representing all species present in the quadrats were collected at each site. In addition, the 

general site areas were surveyed to collect species that may not have occurred in the quadrats. Examples 

of each alga were pressed on herbarium paper, dried, and mounted for archiving. Labels were attached to 

the final mounted specimens, documenting the collector and location of collection. Each specimen was 
inserted into a plastic sleeve and placed in a large binder, separated into rhodophytes, phaeophytes, and 

chlorophytes, and was used as a reference and review tool for the field data collection team. Table 4 lists 

the algal voucher specimens that were collected from the general study area in outer Kachemak Bay. 

Table 4. Algal voucher specimens collected hm intertidal zones in the general study area of 

outer Kachemak Bay. 

Chlorophyta Phaeophyta Rhodophyta 

Acmiphonia sp. #I 

Acmiphonia sp. #2 

Blidihgia minima 

Chaetomorpha tortuosa 

Chaetomorpha melagonium 

Cladophora seriacea 

Codium tilten 

Derbesia marina 

(Halicystis ovalis) 

Entemmorpha linza 

Entemmorpha prdifera 

Komrnannia leptodema 

Monosfroma sp. 

Prasiola meridionalis 

(Rhizoclonium sp.) 

Ulothrix sp. 

Agamm cribmsum 

Alaria fistulosa 

Alaria marginata 

Alaria praelonga 

Analipus japonicus 

Choda filum 

Chodaria flagellifomis 

Coilodesme bulligera 

Cdpomenia peregrina 

Costaria data 

Cymathem ttiplicata 

Desmarestia kurilensis 

Dktyosphon sinicola 

Eudesme virescens 

Fucus cottonii 

Fucus gadneri 

Hedophyllum sessile 

Laminaria groenlandica 

Laminatia saccharins 

Laminaria (discoid holdfast) 

Leathesia difomis 

Melamphon intestinalis 

(Myelophycus intestinalis) 

Nereocystis luetkeana 

Petalonia fascia 

Pilayella/Spongonema 

Punctaria sp. 

Ralfsia fvngifmis 

Saundersella sp. 

Scytosiphon lomentaria 

Soranthera uhidea 

Antithamnionella pacitica 

Bangia sp. 

Bossiella sp. 

Callithamnion pikeanum 

Callophyllis cristata 

Constantinea subulifera 

Corallina sp. 

Cryptosiphonia wdii 

Devaleraea ramentacea 

Dumontia contorta 

Endocladia muricata 

Gloiopeltis fvrcata 

Halosaccion glandifome 

Halosaccion (lepechini) 

Mastocarpus papillatus 

Mazzaella (Gigartinaceae) 

Membranoptera sp. 

Mesophyllum sp. 

Mikamiella sp. 

Neodilsea natashae 

Neoptilota asplenioides 

Neorhodomela sp. 

Odonthalia floccosa 

Odonthalia kamtschatica 

Opuntiella califomica 

Palmaria callophylloides 

Palmatia hecatensis 

Palmaria mdlis 

Phycodtys riggii 

Polysiphonia sp. 

Porphyra abbottae 

Porphyra cuneifomis 

Porphyra pseudolinearis 

Porphyra sp. 

Ptemphonia sp. 

Ptilota serrata 

Rhodymenia pertusa 

Scagelia pylaisaei 

Tokidadendron kurilensis 

Tumerella mertensiana 
Data analyses 

Univariafe methods (individual taxonomic group analyses) 

Previous studies have shown that when rocky-intertidal assemblages differed significantly spatially 

and temporally, the differences were largely due to the relative importance of a few dominant species 

[Underwood and Chapman 1998; Chapman and Underwood 19981. In addition, related studies have 

shown that recovery following disturbance to intertidal communities varied among sites and tidal heights 

[Kinnetic Laboratories, Inc. 1992; Carroll 1 994; Minerals Management Service 19961. Thus, repeated 

measures analysis of variance (rmANOVA) was performed only for several selected taxonomic groups, 

representing species that dominated in the nearby undistxrbed rocky habitat. Two sites were selected 

to represent differences in wave exposure among the eight sites based on the relative ranking of sites 

by fetch and orientation, and the results of the calcium sulfate dissolution experiments (Figure 4). 

The Hesketh Island site (HX) represented highly waveexposed sites and the Herring Island site (BB) 

represented protected sites. These were used in the "Site" effects comparison in the ANOVAs. Separate 

ANOVAs were performed for each MVD. The hypothesis tested for each species was that there was no 

difference in percent cover between sites, scrape dates (date when quadrats established), sampling periods 

(date when data were collected) or their interactions. Sampling date was selected as the repeated measures 

factor. 

When a site has recovered from scraping, no significant differences in mean percent cover between 

control and the scraped quadrats at that site should be apparent. Therefore, a significant interaction 

between site or scrape date and sampling period indicates recovery when significant differences are 

observed for the July 1995 sampling period but not for the September 1996 period. Differences in ,the 

time to recovery will be affected by the unique environmental factors at each site, including wave 

exposure. Thus, significant differences between sites may represent the effect of wave exposure, and the 

suite of environmental factors for which exposure is a proxy, on recovery. Given a significant difference 

in an rmANOVA comparison, multiple comparisons were performed using the Tukey test. To summarize 

the matrices of multiple comparisons, key comparisons were extracted which depended on the particular 

effect. Primary interest was given to contrasts of the control means to the various scrape date means. 

Parameters analyzed included total percent cover (the percent of substrate that is not bare), Semibalanus 

balanoides and Balanus glandula (MVDs 1.5 and 2.5), Semibalanus cariosus (MVD 3.9, Fucus gardneri 

(MVDs 1.5 and 2.5), Alaria spp. (MVD 3.9, and Mytilus trossulus (MVDs 1.5 and 2.5). The significance 

level for all comparisons is 5%. All analyses were performed on percent cover data collected using the 

3dimensional method. The three null hypotheses tested by the univariate analyses are: 

1. Hol : There are no significant differences in recovery for quadrats scraped during 

different seasons (Scrape Date). 

2. 62: There are no significant differences in recovery for quadrats scraped at sites 

with different wave exposures (Site). 

3. Ho3: There are no significant differences in quadrat data collected during different 

site visits (Time). 
Recruitment/Succession Study Sites 

5-1 1 August 1994 

6000. 

Wave exposure decreased - n 

w 

?- 

C 

0 .- 

.d 

- 3 

2 

.OD 2000 n 

0 I I I I 

Site 

RecruitmentlSuccession Study Sites 

3-9 October 1994 

m 

Wave exposure decreased - 

6000 

w 

z' 

s -= 4ooo 

- 3 

2 

10 

ii 

2000 

0 

HI C1 C2 LB SB BB JB KB 

Site 

Figure 4. Mean dissolution of calcium sulfate cylinders deployed at the 2.5 meter 

vertical drop on study sites in August and October 1994. Sites are aligned 

fiom left to right in order of decreasing wave exposure. N = 4 for each site. 

Vertical bars are one standard error. Missing data indicate that cylinders 

were destroyed by waves or couldn't be retrieved in time due to weather. 

Multivariate methods (community level analyses) 

Nonparametric multi-dimensional scaling Fa>S: Kruskal and Wish 1978; Field et al. 19821 was used to 

assess changes in the community-level composition of quadrats. Since the variability in percent cover 

of most organisms was very high, and the statistical power for most univariate analyses was low, these 

community level analyses provide an alternate method for assessing the convergence of scraped quadrats 

with control quadrats over time. Warwick and Clarke [I9911 found that multivariate methods (e.g., MDS) 

were much more sensitive than the commonly used univariate methods at discriminating the response of 

marine communities to stress or environmental changes. Multivariate techniques incorporate populationlevel variation into community-level effects without the subsequent loss of species-specific information 
[Whittle et al. 19981. Among the applicable multivariate techniques (e.g., MDS, cluster analysis, principal 

coordinates analysis, detrended correspondence analysis), MDS was selected because of its robustness, 

applicability and ease of interpretation. The MDS algorithm attempts to plot samples on a twodimensional graph such that the rank ordering of the sample distances agrees with the rank order of 

distances fiom a dissimilarity matrix. If successful, as measured by the "stress coefficient" (0.0-1.0), the 

ordination gives a visual representation of the similarity of the species composition between samples 

[Clarke and Warwick 19941. That is, samples which are highly similar will be close together in the MDS 

plot while dissimilar samples should be widely separated. The stress coefficient reflects the extent to 

which the two sets of ranks do not agree and an accepted rule-of-thumb is that values <0.1 correspond to 

a good fit, values >0.1 and <0.2 give a useful 2-dimensional picture but too much reliance should not be 

placed on the details of the ordination, and values >0.3 indicate an almost arbitrary ordination [Clarke 

and Warwick 19941. Thus, MDS is an indirect gradient analysis method, which is useful here because 

it provides a graphical means of revealing ecologically meaningful relationships among sets of multispecies data. Cluster analyses were also applied to the dissimilarity matrices and were conducted to 

corroborate MDS results. The combination of techniques is especially important when the stress value 

of the MDS ordination is high. 

Multivariate analyses were performed based on family level, or higher, percent cover estimates. It has 

been shown that very little information is lost analyzing data at higher taxonomic levels using MDS and 

in some instances it may better reflect the effects of some environmental variables [Clarke and Warwick 

19941. Advantages of lumping data to higher taxonomic levels include the reduction of redundancy in 

species that characterize the community composition, the ability to include data for those organisms that 

are difficult to identify to the species level in the field, and the reduction of the effects of rare species. The 

Bray-Curtis dissimilarity measure pray and Curtis 19571 was used to calculate distances between sites 

based on mean algal and invertebrate percent cover at each MVD. The statistical package STATISTICA 

for Windows (Statsoft, Inc., Tulsa, OK 74104) was used for MDS analyses. Results are reported for twodimensional solutions. Dissimilarity matrices were constructed to compare data between scrape dates 

within a data collection date. Separate analyses were performed for each data collection date because the 

ordination plots contained too many variables when all of the data were combined, and were too difficult 

to interpret. Analyses were performed for the !%st and the last sampling dates to bracket the temporal 

range of data collection dates. 

Results 

General descriptive patterns 

The study area contained a suite of green, red, and brown algae, as well as space-occupying, grazing, 

and predatory invertebrates on each site. The control quadrats at the eight sites showed some seasonal 

variability, but the dominant species were fairly constant across time. The dominants included the 

barnacles Semibalanus balanoides + Balanus glandula (Balanus) and S. cariosus, the perennial alga 

Fucus gardneri, the grazing snails Littorina sitkuna and L. scutulata, the limpets Lottiapelta, L. digitalis, 

and Tectura scutum, and the blue mussel Mytilus trossulus. The abundance of the annual kelp Alaria spp. 

varied seasonally. 

Balanus dominated in the high intertidal zone, about 1.5 m vertical drop below mean higher high water. 

Attached to or near the barnacle cover was Fucus gardneri, the dominant algal species at this tide height. 

Several other algal species commonly occurred, although at much lower percent cover than F. gardnen. 

They included the red algae Endocladia muncata and Gloiopeltisfitrcata. The most common grazers 

included Littorina sitkana and L. scutulata, with L. sitkuna being more abundant, and the limpets Lottia 

pelta and L. digitalis, with L. pelta being more abundant. 
At 2.5 MVD below MHHW, Balanus were the dominant barnacles, but at a lower percent cover than at 

MVD 1.5. Fucus gardneri still dominated the algal assemblage, but a more diverse algal community 

emerged. Other algae included the rhodophytes Palmaria spp., Odonthalia spp., Polysiphonia sp., 

Pterosiphonia sp. and the chlorophytes, Ulva sp., Monostroma sp. and Acrosiphonia spp. The blue mussel 

Mytilus trossulus was commonly attached to barnacle tests, among F. gardneri or Odonthalia, or in 

crevasses. 

In the lowest intertidal zone studied, 3.5 m below MHHW, the dominant algae were the phaeophyte 

Alaria spp. The thatched barnacle Semibalanus cariosus was the dominant barnacle. The black chiton 

Katharina tunicata was most abundant at this tidal level compared to higher intertidal zones. Limpet and 

littorine snail densities were much lower, although the limpet Tectura scutum was common. 

The temporal changes in the abundance of barnacles, F. gardneri, and Alaria spp. following the scraping 

disturbances are presented to illustrate patterns in recovery for all sites and scrape dates (Figures 5-8). 

Data are presented for the first sampling date that 3-dimensional percent cover data were collected, July 

1995, and for the last data collection date in September 1996. The sites are ordered left to right, fiom the 

most wave-exposed sites to the most wave-protected sites. 

In July 1995, barnacle spat had the highest percent cover (> 80% for some sites) in quadrats that 

were most recently scraped compared to control quadrats and quadrats scraped earlier. The latter had 

decreasing cover with time (Figure 5). The quadrats scraped in March 1994 were most similar to the 

controls. In September 1996, the percent cover values of spat in most quadrats were similar to the control 

quadrats. Figures 6-8 show that for Balanus, Semibalanus cariosus, Alaria spp. and Fucus gardneri the 

percent cover values observed in July 1995 were most similar between control quadrats and quadrats 

scraped in March 1994. Quadrats scraped after March 1994 were least similar to controls and had almost 

no coverage of these organisms in July 1995. By September 1996, the percent cover of Balanus in 

scraped quadrats was generally higher than in control quadrats (Figure 6). In contrast, S. cariosus had 

substantially lower percent cover in all scraped quadrats at MVD 3.5 compared to control quadrats, 

except for the most exposed site at Hesketh Island (Figure 7). This suggests that S. cariosus requires more 

than 2.5 years to fully recover fiom scraping. Also at MVD 3.5, Alaria spp. generally had higher percent 

cover on the more exposed sites, such as HI and C2, and had not recovered in most scraped quadrats by 

the last sampling date in September 1996 (Figure 7). F. gardnen' is most abundant at MVDs 1.5 and 2.5, 

although sites LB and SB had relatively high percent cover at MVD 3.5 in quadrats scraped in March 

1994 (Figure 8). For most quadrats, F. gardneri had recovered to levels similar to control quadrats by 

September 1996, although some scraped quadrats had higher percent cover than did the control quadrats. 

Pie diagrams are presented in Figures 9 and 10 to show the relative contribution of major intertidal 

species to total cover in control and scraped quadrats. The pie diagrams include data fiom all MVDs and 

eight sites combined and are presented to illustrate general trends in species composition. The "slices" of 

each pie represent the relative contribution that the organisms make to total percent cover and should not 

be confUsed with actual percent cover on rocks. Data collected in July 1995 and September 1996 were 

chosen for presentation to illustrate species composition of intertidal cover on the earliest and latest 

sampling dates. Dominant or key intertidal taxa for the control and scraped quadrats are presented and 

are in the same order for each pie diagram to aid interpretation. Species that were not found in quadrats 

fiom a specific scrape date, or were found as a small contributor to total cover, are still named in the pie 

diagram to emphasize their absence in comparison to other quadrat categories. 
Barnacle Spat, MVD 1.5, July 19% 

1 

Barnacle Spat, MVD 1.5, September 1996 

HI C1 C2 LB SB BB JB KB 

Site 

Barnacle Spat, MVD 2.5, July 1995 Barnacle Spat, MVD 25, September 1996 

100 

80 

k 

960 - 

3 40 

C 

20 

0 

HI C1 C2 LB SB BB JB KB HI C1 C2 LB SB BB JB KB 

Slte Site 

Barnacle Spat, 3.5, July 1995 Barnacle Spat, MVD 3.5. September 1996 

100 

80 

k 

860 - 

40 

a 

20 

0 

HI C1 C2 LB SB BB JB KB HI ClC2LBSBBBJB KB 

Si Site 

Figure 5. Mean percent cover of barnacle spat in scraped and control quadrats at each site measured in 

July 1995 and September 1996. Sites are ordered fiom left to right fiom most wave exposed 

to least exposed. MVD = meter vertical drop. Date Scraped = control quadrats or dates when 

quadrats were scraped. Quadrats were not scraped in March 1995 at site KB. Site JB was not 

sampled at MVD 3.5. 
Balanus, MVD 1.5, July 1995 

r- 9 

Balanus, MVD 1.5, September 1996 

100 

80 

L 

m 8 60 - 

g 40 

a 

20 

0 

HI C1 C2 LB SB BB JB KB HI C1 C2 LB SB BB JB KB 

Site Site 

Balanus, MVD 2.5, July 1995 Balanus, MVD 2.5, September 1996 

100 

80 

L 

9 60 

- 

C 

40 

a 

20 

0 

HI C1 C2 LB SB BB JB KB 

Site Si 

Balanus. MVD 3.5. July 1995 

77 

Balanus, MVD 3.5, September 1996 

Site Site 

Figure 6. Mean percent cover of Balanus (Balanus glandula + Sernibalanus balanoides) in scraped and 

control quadrats at each site measured in July 1995 and September 1996. Sites are ordered 

fiom left to right fiom most wave exposed to least exposed. MVD = meter vertical drop. Date 

Scraped = control quadrats or dates when quadrats were scraped. Note y-axis scale change for 

MVD 2.5, September 1996. Quadrats were not scraped in March 1995 at site KB. Site JB was 

not sampled at MVD 3.5. 
Semibalanw, mti08w MVD 3.5, July 1995 Alntia spp, MVD 3.5, July 1995 

Site 

Semibalmus catiosw MVD 3.5, September 1996 

. . . . . . 

HI C1 C2 LB SB BB JB KB 

Site 

Alaria spp, WD 3.5, September 1996 

Figure 7. Mean percent cover of Semibalanus cariosus and Alaria spp. in scraped and control quadrats 

at each site measured in July 1995 and September 1996. Sites are ordered fiom left to right 

hm most wave exposed to least exposed. MVD = meter vertical drop. Date Scraped = control 

quadrats or dates when quadrats were scraped. Quadrats were not scraped in March 1995 at site 

KB. Site JB was not sampled at MVD 3.5. 
Fucw gardimi, MVD 1.5, July 1995 Fucw gardnei mD 1.5, September 1996 

HI C1 C2 LB SB BB JB KB 

Site 

". .... . . . , u HI C1 C2' LB SB BB JB KB 

Site 

Fucus gardnerl MVD 2.5. July 1995 Fucw gardmij WVD 25, September 1996 

HI C1 C2 LB SB BB JB KB 

Site 

Fucus gardmij MVD 3.5, July 1995 Fucw gardnd, MVD 3.5, September 19% 

Site Site 

Figure 8. Mean percent cover of Fucus gardnen' in scraped and control quadrats at each site measured 

in July 1995 and September 1996. Sites are ordered from left to right from most wave exposed 

to least exposed. MVD = meter vertical drop. Date Scraped = control quadrats or dates when 

quadrats were scraped. Quadrats were not scraped in March 1995 at site KB. Site JB was not 

sampled at MVD 3.5. 
In July 1995, control quadrats had a diverse community, with no individual species dominating (Figure 

9). Green algae (chlorophytes), red algae (rhodophytes), brown algae (phaeophytes), mussels, and 

barnacles are all major space occupiers. The relative contributions of the various intertidal organisms 

to total cover in scraped quadrats were very different from those in control quadrats. For most groups, 

total cover was lowest in those quadrats that had the least amount of time to recover since the scrape date. 

In contrast, barnacle spat cover was highest in the most recently scraped quadrats (Figure 9). Just four 

months after scraping, March 1995 quadrats showed a low distribution of most organisms and the highest 

cover of barnacle spat. Another exception is the red alga Porphyra spp., which had higher relative 

contributions to total cover in recently scraped quadrats (March 1995 and October 1994) compared to 

control quadrats. Note that the earliest scraped quadrats (March 1994) were very similar to control 

quadrats and had little contribution by barnacle spat. The blue mussel Mytilus trossulus did not contribute 

significantly to total cover in any of the scraped quadrats whereas in control quadrats it was a significant 

contributor, suggesting M. trossulus is not an early colonizer of bare space on rocks. 

Figure 10 includes pie diagrams of the same organisms presented in Figure 9, for data collected in 

September 1996. The relative contribution of species in control quadrats was almost identical in July 1995 

and September 1996. Scraped quadrats were more similar to control quadrats by September 1996 than 

they had been in July 1995. The major differences between scraped quadrats and control quadrats found 

in September 1996 include greater proportions of Fucus gardneri and Balanus in scraped quadrats. 

M. trossulus contribution to total cover, though greater than in July 1995, was still much lower in all 

scraped quadrats than control quadrats. Also, the relative contribution of S. cariosus was lower in most 

scraped quadrats than in control quadrats. 

Total percent cover (percent substrate that is not bare rock) for all quadrats over time at sites BB and HI is 

plotted in Figures 11 and 12, respectively. These sites were selected to represent wave-protected (BB) and 

wave-exposed (HI) sites and are included in the univariate analyses presented in the next section. Site BB 

data (Figure 11) show that there is little intra- or inter-annual variability in total cover in control quadrats 

at all three MVDs. Scraped quadrats are at, or near, convergence with control quadrats by the last 

sampling date in September 1996. At site HI (Figure 12), total percent cover in scraped quadrats is higher 

than for similar treatments at Site BB. At HI, total percent cover is similar in scraped and control quadrats 

at all sampling dates at MVD 1.5 and during the last two sampling dates at MVDs 2.5 and 3.5. It should 

be noted that quadrats may have similar total percent cover but have very different species compositions. 

Percent cover data are more meaningful when trends are interpreted within the context of key species or 

groups of organisms as is done below. 

Densities of grazers counted in July 1995 and June 1996 are shown in Figures 13-1 5. Direct counts of 

mobile organisms were only conducted twice due to time limitations. The periwinkles Littorina scutulata 

and L. sitkana were common grazers found in the quadrats. L. scutulata is commonly found at lower tidal 

heights than L. sitkana. However, both species occupy a similar grazing niche and are treated together in 

Figure 13. These snails are small, usually < 5 mm, and their abundances are not accurately assessed using 

a 36-point sampling grid. The actual counts are plotted as numbers per square meter. These grazers tend 

to be found in conjunction with barnacles in the high intertidal zone and on or under Fucus gardneri when 

the alga is present [Highsmith et al. 20001. The higher densities of these grazers in scraped quadrats than 

control quadrats may be a result of the higher percent cover of barnacles and F. gardnen' in the scraped 

quadrats (Figure 10). 
01 soo!lnqguo:, aAgeIa1 aql lciavai pw patnqmo:, pne saqs 

@!a luasalda~ qea .unBeq a!d q:,m JOJ laplo am apr palaasald are sagads 

3661 dpf sleqenb u!qly la~o:, ~qolol sa!d leppitn IO@~JO uo!lnqguo3 -6 ad!~ 
All others 

Barnacle spat - 

Quadrats scraped 

AU others - 

Figure 10. Contribution of major intertidal species to total cover within quadrats in September 1996. 

Species are presented in the same order for each pie diagram. Data represent all eight 

sites and MVDs combined and reflect the relative contributions to total cover. 
Site BB, Total Percent Cover, 1.5 MVD 

100 

0 

Jul95 Oct 95 Jun 96 *P 96 

Data Collection Date 

Site BB, Total Percent Cover, 25 MVD 

100 

0 

Jut 95 Oct 95 Jun 96 -96 

Data Collection Date 

Si BB. Total Percent Cover. 3.5 MVD 

0 

Jut 95 Oct 95 Jun 96 

Data Collection Date 

Contrd - - -. Mar 94 - - - Ju194 - -0 Oct 94 ----a Mar 95 

Figure 1 1. Mean total percent cover of all invertebrates and algae in scraped and control 

quadrats at sheltered site BB. Different symbols represent control quadrat. 

or quadrats scraped on different dates, as shown in the legend. The x-axis 

represents the dates when percent cover data were collected. MVD = meter 

vertical drop. Error bars represent one standard error of the mean. 
Site HI, Total Percent Cover, 1.5 MVD 

0 

Jul95 Oct 95 Jun 96 SP 96 

Data Collection Date 

Site HI. Total Percent Cover, 25 MVD 

0 

Ju195 Oct 95 Jun 96 SepS 

Data Collection Date 

Si HI. Total Percent Cover. 3.5 MVD 

0 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Figure 12. Mean total percent cover of all invertebrates and algae in scraped and control 

quadrats at wave exposed site HI. Different symbols represent control 

quadrats or quadrats scraped on different dates, as shown in the legend. The 

x-axis represents the dates when percent cover data were collected. MVD = 

meter vertical drop. Error bars represent one standard error of the mean. 
Littorina spp., All Sites, MVD 1.5 

U ' Jul95 Jun 96 

Data Collection Date 

Littorina spp.. All Sites, MVD 2.5 

Data Collection Date 

Lmorina spp., All Sites, MVD 3.5 

Data Collection Date 

Figure 13. Densities (individuals m-2) of Littorina sitkana and L. scutulata averaged 

across all sites. Data are means of site means. N = 8 at MYDs = 1.5 and 

2.5. N = 7 at MVD = 3.5. MVD = meter vertical drop. Scrape Date = 

control quadrats or dates when quadrats were scraped. Data Collection 

Date = date when percent cover data were collected. 
Limpets, All Sites, MVD 1.5 

Data Collection Date 

Limpets, All Sites, MVD 2.5 

Data Collection Date 

Limpets, Ail Sites, MVD 3.5 

Jul95 ' Jun 96 ' 

Data Collection Date 

Figure 14. Densities (individuals m-') of limpets averaged across all sites. Data 

are means of site means. N = 8 at MVDs = 1.5 and 2.5. N = 7 at 

MVD = 3.5. MVD = meter vertical drop. Scrape Date = control 

quadrats or dates when quadrats were scraped. Data Collection Date 

= date when percent cover data were collected. 
Tectura scutum, All Sites, MVD 3.5 

/P-------7 

Data Collection Date 

Katharina tunicat6 All Sites. MVD 3.5 

Data Collection Date 

Figure 15. Densities (individuals m-2) of the limpet Tectura snttum and the chiton Katharina 

tunicata at MVD 3.5 across all sites. Data are means of site means. N = 7. MVD = 

meter vertical drop. Scrape Date = control quadrats or dates when quadrats were 

scraped Data Collection Date = date when percent cover data were collected. 

Many small limpets occurred in the quadrats, with typically more than 80% <8 mm in length. Limpets 

are difficult to identify at small sizes and were recorded as Lottiidae. However, limpets >8 rnrn were 

identified to species when possible. Figure 14 includes all limpets averaged across the sites. Limpets were 

often more dense on scraped quadrats compared to control quadrats, especially at MVDs 2.5 and 3.5. 

Limpets, as well as Littorina spp., appeared in the quadrats soon after they were scraped For example, 

quadrats scraped in March 1995 tended to have densities similar to, or greater than, control quadrats only 

four months later in July (Figures 13 and 14). Small limpets were often observed living on and among 

young and adult barnacles before anything else was observed in the quadrats. Limpet densities were lower 

at MVD 3.5 than at higher tidal levels. However, the limpet Teciura scuium typically occurs at MVD 3.5. 

Although the densities of this limpet were low (Figure 15), individuals were often very large (>15 mm) 

and can collectively graze a relatively large area. Densities of the chiton Katharina tunicata, another large 

intertidal grazer found at low tidal heights, are also shown in Figure 15. The total numbers of K. tunicata, 

which typically occurs in and among the large tests of Semibalanus cariosus, were low in all quadrats. 

However, these chitons were usually >50 mm in length and could graze large total areas. 
Univariate analyses (individual taxonomic group analyses) 

A comparison was made between the surface percent cover and 3-dimensional methods to determine 

whether the earlier surface data could be combined with the later 3-D collections during this study. 

This comparison would also demonstrate if the 3-D data were comparable to data collected previously 

in the area by other researchers using the simpler method. Figure 16 compares the two methods for 

organisms that generally occur above other organisms (overstory), both above and below other organisms 

(midstory), and beneath most other organisms (understory). The two methods are comparable for the 

brown algae, Alaria spp. (slope = 0.996, ? = 0.994) and Fucus gardneri (slope = 0.92, ? = 0.96). These 

algae are overstory organisms and, if present, appear directly under the intersecting grid points for 

both methods. The two methods did not correlate as well for organisms that often occur beneath other 

invertebrates or algae. The blue mussel MMlus trossulus often grows on top of barnacles but beneath 

algae such as F. gardneri or Odonthaliafloccosa. The surface percent cover method underestimated blue 

mussels by 36% (slope = 0.64, ? = 0.712). Similarly, the midstory algal species Odonthaliafloccosa is 

under-represented as intertidal cover using the surface percent cover method (slope = 0.60, ? = 0.648). 

Barnacles often occur beneath other organisms, especially in the middle and lower intertidal zones. The 

correlation between the two data collection methods is low for barnacle data (slope = 0.45, ? = 0.445). 

This comparison of the two methods indicates that the 3-dimensional data more accurately reflect the 

cover of individual species and that the simpler, surface percent cover method would not be adequate for 

anything other than overstory organisms. Thus, the statistical comparisons reported for this study were 

made only for the data collected by the 3-D method starting in July 1995. 

0 20 40 60 80 100 

3-D Percent Cover 

Akriaspp. V Fucus gardneri Mytilus trossulus 

Odmthalia t7oawsa 0 Sem~batanus babnoides + Balanus gbndula 

mria spp. 

Fucus gardnen 

Semibalanus baI&s 

+ Balanus glanduia 

Figure 16. Linear regressions of percent cover data collected in July 1995 using "surface" and 

"3-D" data collection methods. Slopes and ? values are as follows: Alaria spp. (slope = 

0.996,? = 0.994), Fucus gardnen' (slope = 0.92, ? = 0.96), Mytilus trossulus (slope = 

0.64, ? = 0.71), Odonthaliafloccosa (slope = 0.60, ? = 0.65), and Semibalanus 

balanoides + Balanus glandula (slope = 0.45, ? = 0.44). 
Analyses of percent cover for barnacles resulted in significant interaction effects at MVD 1.5. The 

comparisons of Balanus (Semibalanw balanoides + Balanus glandula) percent cover resulted in 

significant interaction effects (p < 0.05) for the site (ST) x time (T) and scrape date (SC) x T interactions, 

thus rejecting the null hypotheses of no differences in means between both sites and scrape dates over 

time (Table 5). The key multiple comparisons of the STx T interaction yielded no significant differences. 

The multiple comparisons of the SC x T interaction reveal no significant differences for the comparisons 

of control vs. scrape dates by sampling date. The plots of mean percent cover for sites BB and HI (Figures 

17 and 18, respectively) suggest that the main interaction between the sites and the scrape dates was an 

over-recruitment of barnacles at the HI site, even though its control quadrats had lower 

mean percent covers than did site BB. 

Table 5. Summary of repeated measures ANOVA comparisons for adult Balanus (Semibalanus 

balanoides + Balanw glandula) percent cover data at MVD 1.5. The Mauchly's test 

was significant (p < 0.0042) for this comparison so the Greenhouse-Geiser adjustment 

(G-G Adj.) was used. A negative sign before the pvalue of a Tukey multiple 

comparison indicates that the mean decreased fiom one category to the next while a 

positive sign indicates that the mean increased P-values < 0.05 are in bold print. 

Effect df Effect MS Effect G-G Adj. 

P-value 

Site (ST) 

*aping (SC) 

STx SC 

Em 1 

Time (T) 

STxT 

SCxT 

STxSCxT 

Em 2

Summary of Tukey Multiple Comparisons 

July 95 October 95 June 96 September 96 

Site x Time 

BB vs. HI 0.9579 1 .oOO 0.9657 0.8602 

Scrape Date x Time 

Control vs. March 94 0.0991 0.5956 1 .WOO 0.9889 

Control vs. July 94 0.7256 1.0000 0.7730 0.9291 

Contrd vs. October 94 0.20 12 1 .WOO 0.7952 0.9400 

Control vs. March 95 0.2012 0.9497 1.0000 0.9400 
The analysis of variance for Balanus percent cover at MVD 2.5 resulted in significant interaction effects 

(Table 6). The ST x T and SC x T interaction effects are significant. The key multiple comparisons 

revealed no significant differences between sites by similar sampling period. The significant comparisons 

for this effect were among the cross-period comparisons (e.g., July 1995 for BB vs. September 1996 for 

HI) indicating that changes in mean Balanus percent cover between some sampling periods were different 

between sites but these differences do not represent comparisons of recovery and succession and are not 

presented. Comparisons of the SC x T interaction effect demonstrate significantly greater percent cover 

of barnacles for quadrats scraped in March 1995 compared to control quadrats when sampled in October 

1995, June 1996, and September 1996. These significant differences are apparent in the plots of mean 

percent cover for MVD 2.5 at both sites (Figures 17 and 18). These graphs reveal a tremendous increase 

in barnacle cover for the March 1995 quadrats that greatly exceeds barnacle cover for the controls. 

Table 6. Summary of repeated measures ANOVA comparisons for adult Balanus (Semibalanus 

balanoides + Balanus glandula) percent cover data at MVD 2.5. The Mauchly's test 

was significant (p < 0.0064) for this comparison so the Greenhousffieiser adjustment 

(G-G Adj.) was used. A negative sign before the pvalue of a Tukey multiple 

comparison indicates that the mean decreased fiom one category to the next while a 

positive sign indicates that the mean increased. P-values < 0.05 are in bold print. 

Effect df Effect MS Effect P-value G-G Adj. 

P-value 

Site (ST) 1 3.09 0.003 0.9555 

Scraping (SC) 4 10235.15 10.487 0.0000 

ST x SC 4 1264.42 1 296 0.2940 

Error 1 30 975.98 

Time (T) 3 7722.35 21.021 0.0000 0.0000 

STxT 3 1765.05 4.805 0.0038 0.01 11 

SCxT 12 2264.69 6.165 0.0000 0.0000 

STx SCxT 12 226.58 0.617 0.8229 0.7835 

Error 2 90 367.36 

Summary of Tukey Multiple Comparisons 

July 95 October 95 June 96 September 96 

Site x ~ime 

BB vs. HI 0.9502 0.0780 0.9998 0.4323 

Scrape Date x Time 

Control vs. March 94 0.2 1 53 0.3567 0.9995 0.9745 

Control vs. July 94 1 .WOO 0.9942 0.7641 0.0543 

Control vs. October 94 1.0000 0.5071 0.1419 (+) 0.0033 

Control vs. March 95 1 .0000 (+) 0.0002 (+) 0.0002 (+) 0.0002 
Si BB, Semibalanus balanoides + Balanus glandula, 1.5 MVD 

100 

Jut 95 Oct 95 Jun 96 

Data Collection Date 

Site BB, Semibalanus balanoides + Balanus glandula, 25 MVD 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Site BB, Semibalanus mriosus, 3.5 MVD 

100 

Jul95 Oct 95 Jun 96 SP 96 

Data Collection Date 

Figure 17. Mean total percent cover of Semibalanus balanoides + Balanus glandula 

at MVDs 1.5 and 2.5 and S. cariosus at MVD 3.5 in scraped and control 

quadrats at site BB. Different symbols represent control quadrats or 

quadrats scraped on different dates, as shown in the legend. The x-axis 

represents the dates when percent cover data were collected. MVD = 

meter vertical drop. Error bars represent one standard error of the mean. 
Site HI, Semibalanus balanoides + Balanus glanduliq 1.5 MVD 

100 

Jul95 Oct 95 Jun 96 SP 96 

Data Collection Date 

Si HI, Semibalanus Lmlanoides + Balanus glanduliq 25 MVD 

100 

Jul 95 Oct 95 Jun 96 SP 96 

Data Collection Date 

Site HI, Semibalanu~ cario8us, 3.5 MVD 

100 - 

0 

Jul95 Oct 95 Jun 96 SP 96 

Data Collection Date 

Figure 18. Mean total percent cover of Semibalanus balanoides + Balanus glandula 

at MVDs 1.5 and 2.5 and S. cariosus at MVD 3.5 in scraped and control 

quadrats at site HI. Different symbols represent control quadrats or 

quadrats scraped on different dates, as shown in the legend. The x-axis 

represents the dates when percent cover data were collected. MVD = 

meter vertical drop. Error bars represent one standard error of the mean. 
Comparisons of Semibalanus cariosus at MVD 3.5 rejected the null hypotheses of no differences in mean 

percent cover; the ST x T and SC x T interaction effects were significant (Table 7). The comparisons of 

percent cover between stations, limited to comparisons for matching sampling periods, revealed no 

significant differences. The significant comparisons within the set of cross-period comparisons are not 

presented. The comparisons of the SC x T interaction reveal that percent cover of S. cariosus for the July 

1994, October 1994 and March 1995 quadrats for each sampling period were generally significantly less 

than that of the controls. None of the comparisons for the March 1994 quadrats are different fiom the 

controls. Mean percent cover for S. cariosus (Figures 17 and 18) in treated quadrats was generally less 

than in controls although percent cover in March 1994 quadrats was similar to control quadrats, 

particularly at site HI (Figure 18). 

Table 7. Summary of repeated measures ANOVA comparisons for adult Semibalanus 

cariosus percent cover data at MVD 3.5. The Mauchly's test was not significant 

(p = 0.0933). A negative sign before the pvalue of a Tukey multiple comparison 

indicates that the mean decreased fiom one category to the next while a positive 

sign indicates that the mean increased. A logarithmic transformation pog(X + I)] 

was used to correct for inequality of variances. P-values < 0.05 are in bold print. 

Effect df Effect MS Effect F P-value 

Site (ST) 

Scraping (SC) 

STx SC 

Error 1 

Time (T) 

STxT 

SCxT 

STxSCxT 

Error 2 

Summary of Tukey Multiple Comparisons 

July 95 October 95 June 96 September 96 

Site x Time 

BB vs. HI 

Scrape Date x Time 

Control vs. March 94 1 .OOm 0.6043 0.9834 0.8698 

Control VS. July 94 (+) 0.0002 (-) 0.0002 (-) 0.0005 (-) 0.0050 

Control vs. October 94 (-) 0.0002 (-) 0.0002 (-) 0.0004 0.0705 

Control vs. March 95 (-) 0.0002 (-) 0.0002 (-) 0.0002 (-) 0.0002 
The analysis of variance for percent cover of Fucus gardneri at MVD 1.5 provides evidence against the 

null hypotheses of no differences in mean cover due to scrape date, site, or sample date. All main effects 

are significant (Table 8). Comparisons between sites indicate that the percent cover of F. gardneri at site 

BB was significantly greater than at site HI. Tukey multiple comparisons between the control quadrats 

and the percent cover of F. gardneri for the various scrape dates indicate significant differences in percent 

cover between the controls and the October 1994 and March 1995 quadrats. Comparisons between 

sampling periods reveal that the percent cover of F. gardneri increased with time. The results of these 

multiple comparisons are supported by the plots of mean percent cover for F. gardneri at sites BB and HI 

(Figures 19 and 20, respectively). For all scrape dates, the percent cover of F. gardneri at site BB was 

much greater than the cover of F. gardneri at site HI. For MVD 1.5 at both sites, the mean percent covers 

of the October 1994 and March 1995 treatments were the lowest of all quadrats during all four sampling 

periods. Generally, the percent cover of scraped quadrats increased for each sampling period. 

Table 8. Summary of repeated measures ANOVA comparisons for Fucus gardneri percent 

cover data at MVD 1.5. The Mauchly's test was significant @ < 0.0001) for this 

comparison so the Greenhouse-Geiser adjustment (G-G Adj.) was used. A 

negative sign before the pvalue of a Tukey multiple comparison indicates that the 

mean decreased from one category to the next while a positive sign indicates that 

the mean increased. P-values < 0.05 are in bold print. 

Effect df Effect MS Effect P-value GG Adj. 

P-value 

Site (ST) 

Scraping (SC) 

ST x SC 

Em 1 

Time m 

STxT 

SCxT 

STxSCxT 

Em 2

Summary of Tukey Multiple Comparisons 

Site P-value 

BB vs. HI (-) 0.0076 

Scrape Date March 94 July 94 October 94 March 95 

Control VS. 0.9523 0.4388 (-) 0.0202 (-) 0.0309 

Sampling Date July 95 October 95 June 96 

October 1995 (+) 0.0104 - - 

June 1996 (+) 0.0024 0.9644 - 

September 1996 (+) 0.0001 (+) 0.0335 0.1059 
The ST main effect and SC x T interaction effect for percent cover of F. gardneri at MVD 2.5 are both 

significant, rejecting the null hypotheses of no differences in mean cover among sites and scraped dates 

over time (Table 9). Multiple comparisons reveal that site BB had significantly greater percent cover 

than site HI. The comparisons of control to scraped quadrats by sampling period reveal that in July 1995, 

F. gardneri cover in quadrats scraped in July 1994, October 1994, and March 1995 was significantly less 

than in the control quadrats. In October 1995, only those quadrats scraped in October 1994 remained 

different fiom the controls. The plots of mean percent cover (Figures 19 and 20) support the results of 

the comparisons and show that site BB had greater percent cover for all treatments. A trend of increasing 

cover for F. gardnen' over the sampling periods for all scraped quadrats except for those scraped in March 

1994 at site BB, is also shown in Figures 19 and 20. 

Table 9. Summary of repeated measures ANOVA comparisons for Fum gardneri percent 

cover data at MVD 2.5. The Mauchly's test was significant @ = 0.0010) for this 

comparison so the Greenhousdeiser adjustment (G-G Adj.) was used. A 

negative sign before the p-value of a Tukey multiple comparison indicates that the 

mean decreased from one category to the next while a positive sign indicates that 

the mean increased. P-values < 0.05 are in bold print. 

Effect df Effect MS Effect F P-value G-G Adj. 

P-value 

Site (ST) 

*ping (SC) 

STx SC 

Error1 

Time (T) 

STxT 

SCxT 

STxSCxT 

Ermr2 

Summary of Tukey Multiple Comparisons 

Site P-value - 

BB VS. HI (-) 0.0002 

Scrape Date July 95 October 95 June 96 September 96 

Control vs. March 94 1.0000 0.9724 1.0000 1.0000 

Control VS. July 94 (-) 0.0142 0.8434 0.3782 1.0000 

Control VS. October 94 (-) 0.0012 (-) 0.0059 0.5481 1.0000 

Control vs. March 95 (-) 0.0004 0.2650 1 .0000 0.8435 
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I I I n 0 

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2 

-09 8 

001 

anw S-L f~~~e6 snmj '88 as 

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anw S-t '-d& ~!JEIV '88 ws 
Si HI, Fucus gardnd 1.5 MVD 

Jul95 Oct 95 Jun 96 %P 96 

Data Collection Date 

Si HI, Fucus gardneri 25 MVD 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Site HI, Alaria spp., 3.5 MVD 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Figure 20. Mean total percent cover of Fucus gardneri at MVDs 1.5 and 2.5 and 

Alaria spp. at MVD 3.5 in scraped and control quadrats at site HI. 

Different symbols represent control quadrats or quadrats scraped on 

different dates, as shown in the legend. The x-axis represents the dates 

when percent cover data were collected. MVD = meter vertical drop. 

Error bars represent one standard error of the mean. 
The results of the &NOVA comparisons for Alaria spp. percent cover data at MVD 3.5 provide 

evidence rejecting the null hypothesis of no scrape date effects between sampling periods (Table 10). The 

SC x T interaction effect is significant and multiple comparisons indicate that the Alaria spp. percent 

cover in scraped quadrats, excluding March 1994, was significantly less than in control quadrats in July 

1995. 

Table 10. Summary of repeated measures ANOVA comparisons for Alaria spp. percent 

cover data at MVD 3.5. The Mauchly's test was significant (p < 0.0001) for this 

comparison so the Greenhouse-Geiser adjustment (G-G Adj.) was used. A 

negative sign before the pvalue of a Tukey multiple comparision indicates that 

the mean decreased fiom one category to the next while a positive sign indicates 

that the mean increased P-values < 0.05 are in bold print. 

Effect df Effect MS Effect F P-value G-G Adj. 

P-value 

Site (ST) 1 3310.38 2.405 0.1314 

Scraping (SC) 4 3334.13 2.423 0.0700 

ST x SC 4 50.95 0.037 0.9972 

Error 1 30 1376.19 

Time (T) 3 2061 -54 6.723 0.0004 0.0034 

STxT 3 274.50 0.895 0.4469 0.4046 

SC xT 12 786.90 2.566 0.0057 0.0225 

STxSCxT 12 134.44 0.438 0.9436 0.8771 

Error 2 90 306.62 

Summary of Tukey Multiple Comparisons 

Scrape Date July 95 October 95 June 96 September 96 

Control vs. March 94 0.9932 1 .OOOO 0.6461 0.5297 

Control vs. July 94 (-) 0.0003 0.9983 0.2908 0.8260 

Control vs. October 94 (-) 0.0003 0.9964 0.9406 0.9932 

Control vs. March 95 (-) 0.0003 0.9950 0.9992 0.9599 

Plots of mean percent cover in control quadrats at sites BB and HI (Figures 19 and 20, respectively) show 

the intra-annual variability expected for an annual alga. Note that the percent cover of most scraped 

quadrats was lower than in control quadrats. The March 1994 scraped quadrats had cover similar to 

control quadrats in July and October 1995, but decreased below control levels in June and September 

1996. 

Comparisons of percent cover for MH1us trossulus at MVD 1.5 show significant main effects, thus the 

null hypothesis of no differences in percent cover due to scrape date or sampling date was rejected. For 

these comparisons, the SC and T main effects are significant (Table 11). The multiple comparisons of all 

the control quadrats vs. all scraped quadrats for all sites BB and HI combined reveals that the scraped 
quadrats had significantly lower cover of M. trossulus than control quadrats. Figure 2 1 indicates that 

quadrats scraped in March 1994 at site BB had converged with controls by June 1996. Comparisons of 

percent cover by sampling date indicate that the October 1995, June 1996, and September 1996 sampling 

dates had greater cover of M. trossulus than did the July 1995 sampling date. Figures 21 and 22 show 

mean M. trossulus percent cover for sites BB and HI, respectively. With the exception of quadrats scraped 

in March 1994 at site BB and sampled in June 1996 and September 1996, scraped quadrat cover was 

much lower than control quadrat cover at both sites, even by the last sampling date in September 1996. 

At the exposed site HI, M. trossulus was slow to recover in scraped quadrats and will apparently take 

significantly longer than 2.5 years to recover from removal during any season. 

Table 11. Summary of repeated measures ANOVA comparisons for MMlus trossulus 

percent cover data at MVD 1.5. The Mauchly's test was significant (p < 0.0376) 

for this comparison so the Greenhouse-Geiser adjustment (G-G Adj.) was used 

A negative sign before the p-value of a Tukey multiple comparison indicates that 

the mean decreased from one category to the next while a positive sign indicates 

that the mean increased. P-values < 0.05 are in bold print. 

Effect df Effect MS Effect F P-value GG AdJ. 

P-value 

Site (ST) 1 0.81 0.21 5 0.6465 

s~a~iW (SC) 4 37.55 9.923 0.0000 

STxSC 4 5.77 1 -524 0.2204 

Em 1 30 3.78 

Time (T) 3 

STxT 3 

SCxT 12 

STxSCxT 12 

Error 2 90 

Summary of Tukey Multiple Comparisons 

Scrape Date March 94 July 94 October 94 March 95 

Control vS. (-) 0.0282 (-) 0.0004 (-) 0.0003 (-) 0.0003 

Sampling Date July 95 October 95 June 96 

October 1995 (+) 0.0316 - - 

June 1996 (+) 0.0276 1 .0000 - 

September 1996 (+) 0.0015 0.7351 0.7636 
100 

Site BB, Mytilus, 1.5 MVD 

80 - 

& 5 60- - 

C 

p 40- 

L 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Site BB, MytiIw, 25 MVD 

100 , 1 

Ju195 Oct 95 Jun 96 

Data Collection Date 

Site BB, Mytilus, 3.5 MVD 

100 

0 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Figure 2 1. Mean total percent cover of Mytilus trossulus in scraped and control 

quadrats at site BB. Different symbols represent control quadrats or 

quadrats scraped on different dates, as shown in the legend. The x-axis 

represents the dates when percent cover data were collected. MVD = 

meter vertical drop. Error bars represent one standard error of the mean. 
Site HI, Mytiluq 1.5 MVD 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Site HI, Mytilus, 2.5 MVD 

100 

Jul95 Oct 95 Jun 96 

Data Cdlection Date 

Site HI, Mytilus, 3.5 MVD 

100 

0 

Jul95 Oct 95 Jun 96 

Data Collection Date 

Figure 22. Mean total percent cover of Mytius trossulus in scraped and control 

quadrats at site HI. Different symbols represent control quadrats or 

quadrats scraped on different dates, as shown in the legend. The x-axis 

represents the dates when percent cover data were collected. MVD = 

meter vertical drop. Error bars represent one standard error of the mean. 
The rmANOVA comparisons of M. trossulus percent cover at MVD 2.5 result in significant main effects, 

thus rejecting the null hypothesis of no differences in percent cover due to scrape date or sampling 

date (Table 12). The SC and T main effects results are significant. Multiple comparisons of the scrape 

dates show that control quadrats had significantly greater percent cover of M. trossulus than the July 

1994, October 1994, and March 1995 scraped quadrats. The comparisons of sampling dates indicate 

significantly greater cover in June and September 1996 compared to July 1995 and significantly greater 

cover in September 1996 than in October 1995 or June 1996 (Table 12). Figures 21 and 22 indicate little 

inter- or intra-annual variability in M. trossulus cover, as is expected for a sessile, relatively long-lived 

intertidal invertebrate. For sites BB and HI combined, scraped quadrats had not converged with control 

quadrats by the last sampling date in September 1996. 

Table 12. Summary of repeated measures ANOVA comparisons for Mytilus trossulus 

percent cover data at MVD 2.5. The Mauchly7s test was significant (p < 0.0001) 

for this comparison so the Greenhouse-Geiser adjustment (G-G Adj.) was used. 

A negative sign before the p-value of a Tukey multiple comparison indicates that 

the mean decreased from one category to the next while a positive sign indicates 

that the mean increased. P-values < 0.05 are in bold print. 

Effect MS Effect G-G Adj. 

P-value 

Site (ST) 1 1.67 0.287 0.5960 

Scraping (SC) 4 23.93 4.122 0.0089 

ST x SC 4 0.87 0.150 0.9614 

Em 1 30 5.80 

Time (T) 3 11.89 21.060 0.0000 0.0000 

STxT 3 0.97 1.747 0.1 632 0.1862 

SCxT 12 0.96 1.698 0.0802 0.1255 

STxSCxT 12 0.35 0.627 0.8141 0.7384 

Error 2 90 0.56 

Summary of Tukey Multiple Comparisons 

Scrape Date March 94 July 94 October 94 March 95 

Control VS. 0.3498 (-) 0.0090 (-) 0.0365 (-) 0.0393 

Sampling Date July 95 October 95 June 96 

October 1995 1.0000 - - 

June 1996 (+) 0.0010 (+) 0.0011 - 

September 1996 (+) 0.0014 (+) 0.0001 (+) 0.0406 
Multivariate analyses (community level analyses) 

The multi-dimensional scaling ordinations were conducted for the scraped and control quadrats at each 

site. The resulting ordination plots, coded to separate out all scrape date x site combinations, are too 

complex to interpret (as illustrated in Figure 23). Thus, the ordination plots presented in Figures 24 and 

25 are coded to separate out scrape date only. The ordination plots illustrate trends by showing how 

similar each quadrat is to all other quadrats. The proximity of a quadrat to all other quadrats is a measure 

of the similarity of their multi-species data sets, or their intertidal communities. ThC three plots in Figures 

24 and 25 represent ordinations for data from the three MVDs. The codes in the plots represent the 

quadrat scrape date: C = control quadrats, 1 = quadrats scraped in March 1994,2 = quadrats scraped in 

July 1994,3 = quadrats scraped in October 1994, and 4 = quadrats scraped in March 1995. The data 

should be interpreted based on how each data point ordinates relative to all other data points within a plot. 

Thus, by superimposing scrape date codes onto the ordinations (Figures 23-25), we can interpret the role 

of season of disturbance (scrape date) along a gradient, or direction, in the plot. There are no scales on the 

axes, and distances in separate MDS plots cannot be compared. However, shifts in relative distances 

of a series or point relative to other series or points in one plot can be compared to relative distances in 

another. Also, note that the orientation in space for an ordination is irrelevant. A plot could be reversed or 

placed upside down and the interpretations would be identical; the relative inter-point distances between 

every point and all other points is what is important. 

Quadrats scraped in March 1994 ordinate- closest to control quadrats at all MVDs, but had not yet 

converged with controls in July 1995 (Figure 24: stress = 0.098 for MVD 1.5,O. 136 for MVD 2.5, and 

0.120 for MVD 3.5). The stress coefficients indicate acceptable (~0.15) to good (<0.1) fits between the 

inter-point distances in the ordination plots based on the Bray-Curtis dissimilarity data. The two March 

1994 scraped quadrats that ordinated furthest from their controls were from sites JB and C2. As the data 

represented in Figure 24 were collected in July 1995, when most scraped quadrats were less than a year 

old, there had been limited time for recovery. The data points tend to ordinate within "scrape date" groups 

rather than within "site" groups. In other words, the communities in quadrats scraped at the same time but 

at different sites were more similar to each other than were quadrats within a site scraped on different 

dates. Quadrats scraped in October 1994 and March 1995 ordinated together. The sampling date (July 

1995) for these data was shortly after the spring settlement of barnacles and both sets of quadrats had a 

similar "monoculture" of spat. This indicates that space made available on rocks in the fall remains vacant 

until spring and is, therefore, similar to a March disturbance relative to recruitment dynamics. 

September 1996 was the last sampling date for this study and the ordination plots in Figure 25 

(stress = 0.2 18 for MVD 1.5'0. 199 for MVD 2.5, and 0.179 for MVD 3.5) represent the longest time 

that the quadrats had to recover since being scraped The stress values indicate that the ordinations in the 

plots do not accurately reflect the dissimilarities between each data set as calculated by the Bray-Curtis 

dissimilarity index. Thus, interpretations must be general and detailed interpretation of individual points 

can't be made. In general, the control quadrats ordinate separately from the scraped quadrats. However, 

unlike the MDS plots for data collected in July 1995, the codes did not separate out by scrape date. The 

ordination distances between the quadrats scraped in March 1994 and those scraped in July 1994, October 

1994, and March 1995 were not as distinct as they were in July 1995. The quadrats that tended to ordinate 

furthest from control quadrats were those scraped in July 1994, suggesting that a summer disturbance 

follows a different recovery process that delays return to the pre-disturbance community. 
July 1995 

MDS 

Unweighted Pair-Group Average 

Dissimilarities from Matrix 

m 1 

MVD 1.5 

Figure 23. Example of coding style for multi-dimensional scaling. The coding is for multi-species data 

combined across all sites and scrape dates (+ controls) within a meter vertical drop. The labels 

in graphs A and B contain codes for site (first two letters or letter and number for C 1 and C2), 

meter vertical drop (fmt number), data collection date (second number), and quadrat type (last 

number representing control or scrape date). Graph A illustrates the MDS ordination with 

original codes, graph B represents results from a cluster analysis, and graph C shows MDS 

ordination results coded for quadrat type, including controls. The dotted lines delineate 

clusters at the 36% similarity level, as shown in B. 
July 1995 MVD 1.5 

July 1995 MVD 2.5 

July 1995 MVD 3.5 

Figure 24. Multi-dimensional scaling ordination of July 1995 multi-species data fiom 

control and scraped quadrats at eight sites. Series codes are: C = control 

quadrats, 1 = quadrats scraped in March 1994,2 = quadrats scraped in July 

1994,3 = quadrats scraped in October 1994,4 = quadrats scraped in March 

1995. The eight data points within each series represent the eight sites. MVD 

= meter vertical drop. 
September 1996 MVD 1.5 

September 1996 MVD 2.5 

September 1996 MVD 3.5 

Figure 25. Multi-dimensional scaling ordination of September 1996 multi-species data from 

control and scraped quadrats at eight sites. Series codes are: C = control quadrats, 

1 = quadrats scraped in March 1994,2 = quadrats scraped in July 1994,3 = quadrats 

scraped in October 1994,4 = quadrats scraped in March 1995. The eight data points 

within each series represent the eight sites. MVD = meter vertical drop. 
The ordinations shown in Figure 24 exhibit the classic horseshoe, or arch, effect. This is a common 

feature of ordinations fiom single, strong environmental gradients. In the case of these ordinations, the 

environmental gradient is "scrape date". Samples toward opposite ends of the environmental gradient 

have few species in common, thus having high dissimilarities. When the plot arches near the tail, this 

indicates that dissimilarities near 100% have been reached [Clarke and Warwick 19941. By September 

1996 (Figure 25), after the quadrats had a longer time to recover fiom being scraped, the separation along 

the "scrape date" environmental gradient is not as strong and the horseshoe effect is absent. This is fiather 

indication that all scraped quadrats were more similar to control quadrats in September 1996 than they 

were in July 1995. 

Figures 26-31 extract individual sites fiom the MDS plots presented in Figures 24 and 25. The eight 

individual plots within each figure were not created fiom separate dissimilarity matrices, but were 

extracted fiom the MDS ordination for all sites combined. The extraction by site is for aiding 

interpretations of how quadrats within a site ordinate relative to each other. Figure 26 extracts the site 

data fiom the MDS ordination at MVD 1.5 shown in Figure 24. The arrows indicate the direction fiom 

most recently scraped quadrats (March 1995) towards older quadrats and finally towards control quadrats. 

Exceptions are for sites KB and JB where the most recently scraped quadrats were in October 1994. 

The general direction of the arrows in Figures 26-28 for all sites is along a gradient in the same direction 

within each figure, indicating that in July 1995 the ordination within each original MDS is driven by 

scrape date. At MVD 1.5 (Figure 26), the most exposed sites-HI, Cl, and C2-had control quadrats 

most dissimilar fiom the next closest (ordinated) scraped quadrat. In other words, the quadrats scraped in 

March 1994 (those quadrats with the longest time to recover after being scraped) ordinated fUrther fiom 

their control quadrats at these sites than they did at the other five sites. This indicates that the exposed 

sites initially recovered more slowly than the less exposed sites. Data collected in September 1996 

(Figures 29-3 1) ordinate in patterns different than those observed for the July 1995 data. The arrows do 

not point in the same direction along a gradient in each plot. Thus, as also shown in Figure 25, there is not 

a strong environmental gradient related to scrape date as seen for July 1995 sampling data. However, a 

different pattern emerges that was not as apparent when the data for all sites were shown in one ordination 

(Figure 25). The quadrats scraped in March 1995 tended to be more similar to the control quadrats than 

quadrats scraped in July and October 1994, even though the latter had five and eight months longer to 

recover, respectively. This pattern is particularly evident at MVDs 2.5 and 3.5 (Figures 30 and 3 1). For 

most site-extracted plots that show this pattern, the scrape date that ordinates fiathest fiom controls is July 

1994, indicating that by September 1996 their invertebrate and algal communities were most dissimilar to 

undisturbed control quadrats. 
Site SB 

Site JB 

Site BB 

Site KB 

Figure 26. MDS ordination of July 1995 multi-species data at MVD 1.5, redrawn fiom Figure 

24. Individual sites are extracted and plotted without all other ordination points. The 

arrows point in the direction fiom quadrats scraped in March 1995 + quadrats 

scraped in October 1994 + quadrats scraped in July 1994 + quadrats scraped in 

March 1994 + control quadrats. Quadrats were not scraped in March 1995 at sites 

JB or KB. The relative axes scales are the same for all plots. 
Si HI Site C1 

Site BB 

Figure 27. MDS ordination of July 1995 multi-species data at MVD 2.5, redrawn fiom Figure 

24. Individual sites are extracted and plotted without all other ordination points. The 

arrows point in the direction from quadrats scraped in March 1995 + quadrats 

scraped in October 1994 + quadrats scraped in July 1994 + quadrats scraped in 

March 1994 + control quadrats. Quadrats were not scraped in March 1995 at sites 

JB or KB. The relative axes scales are the same for all plots. 
Site SB 

Figure 28. MDS ordination of July 1995 multi-species data at MVD 3.5, redrawn from Figure 

24. Individual sites are extracted and plotted without all other ordination points. The 

arrows point in the direction from quadrats scraped in March 1995 + quadrats scraped 

in October 1994 + quadrats scraped in July 1994 + quadrats scraped in March 1994 

+ control quadrats. Site JB had no quadrats at h4VD 3.5. Quadrats were not scraped 

in March 1995 at sites JB or KB. The relative axes scales are the same for all plots. 
Site HI Site C1 

Site C2 Si LB 

Si SB Site BB 

Figure 29. MDS ordination of September 1996 multi-species data at MVD 1.5, redrawn fiom 

Figure 25. Individual sites are extracted and plotted without all other ordination 

points. The arrows point in the direction fiom quadrats scraped in March 1995 + 

quadrats scraped in October 1994 + quadrats scraped in July 1994 + quadrats 

scraped in March 1994 + control quadrats. Quadrats were not scraped in March 1995 

at sites JB or KB. The relative axes scales are the same for all plots. 
Site JB Si KB 

Figure 30. MDS ordination of September 1996 multi-species data at MVD 2.5, redrawn fiom 

Figure 25. Individual sites are extracted and plotted without all other ordination 

points. The arrows point in the direction fiom quadrats scraped in March 1995 + 

quadrats scraped in October 1994 + quadrats scraped in July 1994 + quadrats 

scraped in March 1994 + control quadrats. Quadrats were not scraped in March 1995 

at sites JB or KB. The relative axes scales are the same for all plots. 
Site C1 

Site C2 Site LB 

Site BB 

Figure 3 1. MDS ordination of September 1996 multi-species data at MVD 3.5, redrawn fiom 

Figure 25. Individual sites are extracted and plotted without all other ordination 

points. The arrows point in the direction fiom quadrats scraped in March 1995 + 

quadrats scraped in October 1994 + quadrats scraped in July 1994 + quadrats 

scraped in March 1994 + control quadrats. Site JB had no quadrats at MVD 3.5. 

Quadrats were not scraped in March 1995 at sites JB or KB. The relative axes scales 

are the same for all plots. 
Discussion 

The two major goals of this study were to establish a multi-year sampling program in rocky-intertidal 

assemblages of outer Kachemak Bay and to assess the intertidal invertebrate and algal recruitment and 

successional patterns leading to recovery after seasonal disturbances across a range of wave-exposed 

sites. Eight locations were selected and established as permanent rocky habitat monitoring sites. Calcium 

sulfate dissolution measurements made at each one showed substantial differences in water motion and 

the sites were subjectively ranked as exposed versus sheltered. The site on Hesketh Island (HI) and two 

on one of the Herring Islands (C 1 and C2) are exposed to most local storm waves in addition to residual 

ocean swells that occur as a result of storms many miles away. These sites also had the highest dissolution 

rates. The three sites ranked as having moderate wave exposure-LB, SB, and BB-all have similar 

dissolution rates that were slightly lower than at the more exposed sites. The site in Jakolof Bay (JB) had 

a higher dissolution rate during spring-tide series than expected by its ranked wave exposure. JB is near 

the entrance to the bay where a geographic constriction causes tidal currents to increase dramatically 

relative to surrounding water, resulting in a high dissolution rate. The most sheltered site, KB, had the 

lowest dissolution rate during the study. Generally, the subjective ranking of sites based on observations, 

orientation relative to prevailing storm direction, and fetch matched the measured dissolution rates. The 

method provides an additional inexpensive, quick tool for assessing or understanding differences in 

water movement at intertidal sites. Highsmith et al. [I9941 showed, through multi-variate analyses, that 

community level species similarities among sites across the entire Exxon Valdez spill region were best 

described by wave exposure, rather than by local geography or any other variable studied. 

The eight established sites were successfully surveyed in March 1994; permanently marked during each 

of the treatment visits in March 1994, July 1994, October 1994, and March 1995; and monitored during 

four sampling periods between July 1994 and September 1996. Intertidal zonation was reflected at the 

sites by the shift in dominant barnacles by tidal height, as well as a shift fiom the perennial alga Fucus 

gardneri dominating algal cover in the upper and mid intertidal zone to Alaria spp. dominating in the low 

intertidal zone. The control quadrat measurements are a time-series of data representing late spring/early 

summer and fall periods for two years and provide inter- and intra-annual comparisons of mky-intertidal 

habitat in outer Kachemak Bay. These data indicate that over the course of the study the dominant 

intertidal invertebrates exhibited a relatively stable population, or spatial cover. There was relatively little 

variation between seasons and years for the major barnacle species, Semibalanus balanoides and Balanus 

glandula, in the upper and middle intertidal zones and S. cariosus in the lower intertidal zone. In a closely 

related California study in the mid-1980s [Kinnetic Laboratories, Inc. 1992; Minerals Management 

Service 19961, investigators also found that, although there were differences among sites, there was 

relatively little seasonal or year-to-year variation in the abundances of the most common species at a 

given site over a six-year period. 

The data presented in this report span a relatively short period of time compared to similar intertidal 

monitoring studies in Alaska [Highsmith et al. 2000; Coates et al. 19993, but the relative stability of the 

dominant space-occupying invertebrates and algae in undisturbed habitat was similar among the studies. 

In 1996, Pentec Environmental, Inc, [I9961 revisited several rocky-intertidal shorelines that had been 

surveyed between 1974 and 1978. They reported no major shifts in species dominance or in the health 

of the intertidal communities outside of the natural variations shown in 1974-1978, indicating that rocky 

sites in Kachemak Bay had experienced an extended (1 8+ years) period of stability. An earlier rockyintertidal habitat study conducted in outer Kachemak Bay [Carroll 19941 did show inter- and intraannual variability for several dominant organisms. These inconsistencies can be attributed to two main 

differences between this and the current Kachemak Bay study. First, the earlier study conducted by 

Carroll [I9941 recorded only those organisms that occurred directly beneath each grid point when 

collecting percent cover data. Thus, organisms that typically occur as midstory or understory organisms, 

such as barnacles, were underestimated when overstory algal cover was high. For example, he showed 

that S. cariosus exhibited large seasonal shifts in percent cover, even though this organism is a relatively 
slow-growing, long-lived sessile invertebrate. The current study collected data through overstory, 

midstory and understory layers which more accurately reflect the abundance of organisms. Secondly, 

Carroll [I9941 reported a massive winter-kill of many sessile invertebrates due to extremely low air 

temperatures immediately before his sites were established. His study was designed to document recovery 

fkom this stress, and his control sites, or sites that were not experimentally treated, were recovering 

fkom this natural clearing disturbance. The timing of the winter fieeze that he documented as creating 

widespread disturbances to the intertidal zone of outer Kachemak Bay occurred in January, similar to the 

timing of the disturbances created in March 1994 and 1995 for this study. 

The study design for determining whether the timing of disturbances affected recovery patterns over 

a range of wave-exposed rocky-intertidal habitat was complex: eight sites, three tidal heights, five 

treatments (control quadrats and four scrape dates), and four data collection dates. Statistical analyses 

or descriptions of the patterns for individual species at each site x tidal height x treatment combination 

were not possible within the scope of this study. A species by species report for each site, MVD, and 

scrape treatment across the four sampling dates would most likely show differing trends for each species 

or taxon based in part on the variables already mentioned, but also on an organism's life history and 

reproduction cycle, feeding strategy, dependence on other species for food or protection, toleraoce of 

temperature or salinity extremes, growth rate, and whether it was sessile or mobile. Highsmith et al. 

[I9941 showed injury and recovery assessment trends across three sampling dates after the Ejuson Valda 

oil spill for over 50 invertebrate and algal taxa at each of three tidal heights and four habitat types. Injury 

and recovery trends differed among species, and within species they often differed across habitats and 

tidal heights. The present study focused on several dominant organisms for statistically comparing 

recovery trends of the various scraped quadrats to those of control quadrats at two sites, and relied upon 

multivariate techniques to compare combined algal and invertebrate multi-species data for the treatment x 

site x MVD combinations. The data for several individual taxa were combined across all sites to illustrate 

general recovery trends within the region. 

Barnacles were significant contributors to intertidal cover in the mid to upper intertidal zone on outer 

Kachemak Bay rocky shores. Balanus (Semibalanus balanoides + Balanus glandula) were also the 

dominant organisms recruiting to the space made available in scraped quadrats. Recruitment was not a 

limiting factor for recovery in the high and mid intertidal zone, as Balanus cover was generally higher 

in scraped quadrats than control quadrats. Barnacle recruitment into scraped quadrats was very high in 

the spring. In the quadrats scraped in March 1995, there was a decrease in total cover between spat in 

July 1995 and mature barnacles in September 1996, due to juvenile mortality. The ratios of barnacle 

spat to Balanus percent cover were relatively constant across sites. For most sites and tidal heights, the 

September 1996 data revealed that barnacle percent cover on the most recently scraped quadrats was still 

substantially higher than the controls, due in large part to over-recruitment into the bare space provided 

by the scraping. The dominant barnacle in the low intertidal is S. curiosus, which recruited at a much 

lower rate and still had not reached control levels by the end of the study in September 1996, except at 

site HI in quadrats scraped in March 1994. 

Gregarious settlement, in which larvae colonize in response to indicators of their own species, may 

account for the high initial recruitment of barnacles into newly scraped quadrats. Gregarious response is 

stronger in barnacles, especially Balanw glandula, than other intertidal organisms [Larrnan and Gabbott 

19751. For most barnacle species, planktotrophic larvae are released in early spring to coincide with 

spring phytoplankton availability [Crisp 19761. Thus, larval settlement is highest during spring. Carroll 

[I9941 documented barnacle recruitment onto artificial plates at two sites and two tidal heights in outer 

Kachemak Bay. The date on which recruits were first observed on test surfaces during his three-year 

study varied by only 4 days, fkom 8-1 1 May. However, he detected differences in the total length of time 

that the barnacles recruited during each year. In 199 1, barnacles "trickled" in during much of the spring 

and summer. In 1992 and 1993, recruitment began with an initial heavy pulse, resulting in maximum 
density of recruits by the beginning of June. The pattern Carroll [I9941 detected in 1992 and 1993 was 

similar to the results for this study. Barnacle spat were the initial colonizers of quadrats having bare space 

available in the spring and the highest densities of spat were detected during the summer sampling dates, 

July 1995 and June 1996. Significantly fewer barnacle spat were detected in October 1995 and September 

1996, probably due to mortality and advancement to larger size classes. Some barnacles recruited later, 

as evidenced by the presence of adult Balanus in quadrats sampled July 1995 that had been scraped in 

July 1994. Strathrnann and Branscomb [ 19791 observed that larvae of the barnacles B. glandula and 

S. cariosus recruited more heavily into algal cover transplanted fiom low intertidal substrates to the 

upper intertidal zone than among algae resident in the upper intertidal area. Thus, the absence or presence 

of specific algal species could enhance recovery after a disturbance by affecting microhabitats utilized 

by other species, such as barnacles. 

Percent cover values for Fucus gardneri indicated variable recruitment and recovery. This species is the 

major structural component of rocky shorelines throughout much of Alaska's coastline and was heavily 

damaged by the EVOS and subsequent clean-up activities PeVogelaere and Foster 1993; Stekoll and 

Deysher 1996; Highsmith et al. 20001. Quadrats scraped in March 1994 generally had the highest Fucus 

cover of any scraped quadrats during the study and were more similar to the control quadrats at the end of 

the study than for any other scrape date. Also, the overall cover of Fucus was lowest at the most exposed 

sites (Figure 8). Percent cover values may fluctuate annually, as there appear to be some differences in 

cover at the control sites fiom year to year. Interactions between organisms may play a part in highly 

variable recruitment as well. For example, barnacles can facilitate the settlement of Fucus eggs [Carroll 

1994; Highsmith et al. 2000), although long-term survival of Fucus plants on barnacle tests is lower than 

for plants growing in substrate cracks [Stekoll and Deysher 19961. 

A study conducted in Herring Bay revealed decreased grazer densities when Fucus gardneri was removed 

fiom quadrats mighsmith et al. 20001. In that study, limpets and littorine snail abundances decreased on 

rocky substrate directly beneath Fucus canopy after the plants were removed. While limpet densities 

increased to pre-Fucus removal levels after one month, L. sitkana densities still remained depressed two 

months later. In the current study, littorine densities equal to or greater than those in control quadrats were 

found in scraped quadrats by July 1995. Quadrats scraped in March were dominated by barnacle spat, yet 

contained greater numbers of littorines than did control quadrats, even in the total absence of Fucus cover. 

Under the experimental conditions of these two studies, littorines appear to take at least two months but 

less than 16 months to recruit back into scraped quadrats. 

Alaria spp. are commonly found in association with Semibalanus cariosus in the low intertidal zone. The 

holdfasts of these algae are often attached directly to the barnacle tests, suggesting that the presence of 

S. cariosus may facilitate Alaria recruitment. Compared to the other species included in this study, Alaria 

recovery in the low zone appears to be much slower, though Alaria cover was highest on sites with the 

highest S. cariosus cover. Alaria spp. were one of the algal genera damaged by the EVOS [Highsmith 

et al. 19941. Recruitment of Fucus into the space made available by the removal of Alaria at oillclean-up 

impacted beaches resulted in higher cover of Fucus at oiled sites compared to non-oiled sites in the low 

intertidal area. The current study results do not show this replacement at MVD 3.5, although Alaria cover 

in control quadrats was highest at sites with low Fucus cover. 

Only limited recruitment patterns appeared to be related to the wave exposure gradient, perhaps because 

barnacle spat recruitment was high at most sites. Both Semibalanus cariosus and Alaria spp. showed 

higher percent cover at the three exposed sites than at the protected sites, especially by September 1996 

(Figure 7). In contrast, Fucus gardneri had higher cover at protected sites (Figure 8), with significant 

differences at MVD 1.5 between sites HI (exposed) and BB (protected) (Table 8). F. gardneri did not 

recruit into scraped quadrats until after barnacles had recruited into the space and, as noted above, 

Alaria spp. recovery may be dependent upon prior S. cariosus recruitment. 
General successional patterns emerged as the quadrats were sampled over time. Barnacle spat recruitment 

was highest in quadrats that had the most bare space available when data were collected in July 1995 

(i.e., quadrats scraped most recently). By September 1996, however, barnacle spat cover was low, in part 

because bare space was becoming limiting in many of the scraped quadrats, with total percent cover near 

80%. Also, barnacle spat grew into adult barnacles (Semibalanus balanoides and Balanus glandula), 

increasing total adult barnacle cover. In fact, in most scraped quadrats, the percent cover of adult 

barnacles was higher than in control quadrats as a result of the over-recruitment of spat onto the available 

bare space when the quadrats were created. Rolan and Gallagher [199 11 reported similar trends for 

Semibalanus balanoides following an oil spill at Sullom Voe, with a rapid initial population increase 

following the spill that reached densities higher than those reported in pre-spill data. They, however, 

attributed the increase to spill-related loss of a major barnacle predator. As barnacle spat matured in 

the scraped quadrats, adult barnacle percent cover was lower than previously found for barnacle spat, 

indicating spat mortality, possibly due to overcrowding. In contrast, over-recruitment did not occur in the 

larger, low intertidal species, Semibalanus cariosus. This barnacle had not recovered by the last sampling 

date, except in scraped quadrats that had the most time to recover ( >2.5 years). 

Mytrlus ttossulus recovery was incomplete for all scraped quadrats at sites BB and HI combined. 

Recovery appeared to be finther along at the wave-protected site BB (Figure 2 l), compared to the 

waveexposed site HI (Figure 22), but significant differences in recovery rates were not detected by 

the rmANOVA. However, recovery shown for M. trossulus is probably underestimated. Although the 

3-dimensional percent cover method used to collect these data did measure understory organisms, it did 

not detect more than one layer of the same organism. Once a taxon was encountered, it was not recorded 

again if it occurred more than once. This decision was made because most algal species fold over onto 

themselves and individuals would otherwise be recorded twice or even three times. However, for 

organisms such as M. trossulus, that often recruit to byssal threads of established individuals, our 3-D 

method is not truly counting individual mussels in a three dimensional manner. Recovery of mussel beds 

in cleared areas during a California study [Kinnetic Laboratories, Inc. 1992; Minerals Management 

Service 19961 was slow and took up to ten years or more at most sites. Suchanek [1978], however, 

reported that for exposed rocky shorelines in southeastern Alaska, mussels settled densely in bare space 

and grew quickly to reproductive size, oh occupying 7580% of the substratum. 

Recovery fiom disturbance was incomplete in the most recently scraped quadrats by the last sampling 

date in September 1996, although some sites were finther along in the recovery process than others. 

Quadrats scraped in July and October 1994 were finthest fiom recovery compared to control quadrats. 

Quadrats scraped in March 1994 and March 1995 were more similar to control quadrats. Quadrats 

scraped in March, before barnacle larval settlement, had the most bare space available for recruitment. 

A similar study conducted in California also showed that recovery varied with time of clearing 

[Kinnetic Laboratories, Inc. 1992; Minerals Management Service 19961. Their study showed that in an 

Endocladia/Mmtocarpuspapillatus assemblage, quadrats scraped in spring had recovered to a greater 

extent than those cleared in the fall. Sousa [1979a, b] reported that seasonality of recruitment is crucial 

in determining the sequence in which species colonize newly cleared space, with the species that is least 

seasonal in its recruitment usually becoming established first. Our data contradict this statement since 

barnacles dominate in quadrats scraped during all seasons, even though their recruitment is extremely 

seasonal. 

On the central Oregon coast, Farrell [I9911 reported that the general order of succession was the same for 

experimental clearings: Chthamalus dalli + Balanus glandula + macroalgae (including Fucus). Fucus 

colonized only after barnacles had done so, similar to the findings of this study. Although the general 

order of succession was the same for different clearings, the time required ranged fiom less than 12 

months to greater than 36 months. FarreU [I9911 attributed the differences in the rates of succession to 

variations in the timing of successful Balanus recruitment. For our study, scraped quadrat recovery also 
depended on the recruitment of barnacles, which delayed recovery stages for almost a year for quadrats 

scraped in the summer and fall until the following spring's barnacle settlement. 

Multidimensional scaling has become a widely accepted model for demonstrating ecological patterns 

in a variety of marine communities. Applied to this study, it successhlly illustrated the differences in 

intertidal communities among controls and quadrats scraped on different dates. In addition, the method 

showed the relative convergence of quadrats scraped in March 1994 and 1995 compared to quadrats 

scraped in July and October 1994. Additionally, the dissimilarities of scraped quadrats compared to 

control quadrats was reduced between July 1995 and September 1996. MDS methods have been applied 

extensively in studies of environmental impacts of pollution on soft sediment subtidal habitats to show 

differences in community structure between polluted and non-polluted sites or to show shifts in 

community structure along a pollution gradient [Gray et al. 1988; Agard et al. 1993; Warwick 19931. 

MDS was also utilized to assess benthic communities following the EVOS in subtidal environments of 

Prince William Sound [Feder and Blanchard 1998; Jewett et al. 19991. Highsmith et al. [I9941 used MDS 

methods to evaluate recovery of invertebrate and algal communities on rocky substrates after the Exron 

Valdez disturbance and subsequent clean-up activities. MDS methods had not been applied to many 

rocky-intertidal studies previously and their data showed that site exposure to waves explained the 

ordinations and oiling category did not. Hansen and Ingolfsson [I9931 used MDS methods to evaluate 

patterns in species composition of Iceland's rocky shorelines and found that the degree of site exposure 

was an important factor in structuring intertidal communities. Since then a number of studies have used 

MDS to evaluate rocky-intertidal habitats [Chapman and Underwood 1998; Conlan et. al. 1998; Dye 

1998; Lasiak 19981. 

No direct relationship between recovery rate and site wave exposure was apparent from the MDS 

analyses. MDS analyses performed after the EVOS for intertidal invertebrates and algae from rocky 

shores [Highsmith et al. 19941 indicated that sites with similar wave exposures were more similar than 

sites within a given geographi-cal area. This suggests that effects due to wave exposure may be masked in 

this study as a result of the high variability observed. Unfortunately, data collection in Highsmith et al. 

[1994] was short term relative to recovery, and specific assessment of the interaction between community 

recovery rates and wave exposure was not possible during that study. Wave action may contribute to the 

productivity of more exposed coastlines by providing food and nutrients, limiting self-shading algae, and 

protecting sessile species from grazing and predation [Leigh et al. 19871. Sessile invertebrates tend to 

reach their largest individual size at wave-swept sites paine 19761, but mobile grazers and predators 

are generally smaller wenge 1974; Paine 1976; Denny et al. 1985; Brown and Quinn 19881. Although 

individuals may be smaller, some invertebrates can be more abundant on exposed shorelines. Brown and 

Quinn El9881 found smaller, but more abundant, Nucella and limpets on exposed shorelines. However, 

the reverse may also occur. In Herring Bay, higher abundances of a littorine snail were found at protected 

than exposed sites mghsmith et al. 20001, although the differences in wave exposure were much less 

than across the eight sites in this study. The effects of wave exposure on intertidal organisms are not 

always clear and the results of this study, primarily the assessment of specific organisms rather than 

community level analyses, suggest only weak to moderate influences on recruitment and recovery of 

scraped sites within this particular study area. 

Recovery rates will vary with the scale of the disturbance, with intertidal communities taking longer 

to recover from disturbances that substantially increase distances to source populations for recruits. 

Recovery rates detected during this study were higher for several dominant intertidal organisms 

(e.g., Balanus and Fucus gardnen') than for the same species damaged by the Exron Valdez oil spill. 

Fucus gardneri recovery in the high intertidal zone was not complete by September 1996 of this study. 

However, most scraped quadrats had significantly increased Fucus cover and were beginning to approach 

levels similar to control quadrats. Fucus damaged in high intertidal areas impacted by the EVOS had not 

recovered to the levels found on moiled shorelines seven years after the spill. The higher recovery rate 
is most likely a result of the size of scraped quadrats compared to the vast intertidal areas affected by the 

spill. The scraped quadrats in this study were surrounded by healthy, undisturbed intertidal communities. 

The presence of nearby barnacles may encourage gregarious settlement of larvae. Fucus gardneri egg 

dispersal distance is very limited, with settlement occurring near the adult plant [Stekoll and Deysher 

19961. Thus, in our study, nearby plants provide a source of eggs for the disturbed sites. In a heavily 

oil- or treatment-damaged area, Fucus cover along whole shoreline segments may be dramatically 

reduced, thus greatly retarding Fucus recovery rates. Studies in Herring Bay showed slow increases in 

limpet and littorine densities on oiled sites in the years following the EVOS. These studies also showed 

slow steady increases in densities in cleared sites at unoiled shorelines adjacent to heavily oiled areas, 

indicating that the available recruits to the entire area were affected by the extensive loss of adults at oiled 

sites. We observed relatively short recovery periods for limpets and littorines in our quadrats, suggesting 

availability of potential recruits was not a recovery restraint in this study. 

Conclusions 

1. Recovery from disturbances occurs on different time scales for different species, different 

habitats and different geographic locations. We have shown during this study that time of 

disturbance relative to seasonal reproductive events of major space-occupying species can 

affect the timecourse of recovery. However, the study did not continue long enough for all 

end points to be reached nor for confirmation of overall community recovery by documenting 

achievement of stability (i.e., no further significant change or difference fiom controls). 

Consequently, a primary conclusion of this study is that long-term monitoring of experimentally disturbed sites is needed in Kachemak Bay in order to fully understand the specific 

events and timecourse of recovery from seasonal disturbances. However, this study does 

provide a data and knowledge base for continued intertidal monitoring and research in the 

region that should be incorporated into a long-term program. As there may be habitat and local 

geographic differences in recruitment and post-recruitment dynamics, research of the type 

conducted in this project should also be conducted on a long-term basis at other locations 

within Kachemak Bay and Cook Inlet. 

2. The specific objectives of the study in the rocky-intertidal habitat of outer Kachemak Bay were 

to: a) determine whether the season in which a disturbance occurs affects recovery rates or 

successional processes, b) quantify inter- and intra-annual abundance pattems for major spaceoccupying species, and c) determine the effect of wave exposure on community structure and 

response to seasonal disturbances. To address these objectives, eight rocky-intertidal sites 

were established over a gradient of wave exposures and permanently marked such that baseline 

data can continue to be collected in the future (see conclusion 1). Data were collected fiom 

undisturbed control quadrats during two summer and two fall sampling periods in 1995 and 

1996 to quantify inter- and intra-annual abundance pattems for major space-occupying species. 

In addition to control quadrats at each site, experimental quadrats were cleared of all biota 

during different seasons and followed over time to see if the timing of a disturbance affects 

recovery rates and/or successional processes. The data collected fiom these sites could provide 

pre-spill data in the event of a catastrophic oil spill at upstream coastal areas in the Gulf of 

Alaska or in Cook Inlet. 

3. The season in which a disturbance to rocky-intertidal habitats in southcentral Alaska takes 

place affects recruitment, successional, and recovery patterns of several dominant intertidal 

algae and invertebrates. In this study, summer and fall disturbances took longer to recover fiom 

than disturbances in the spring, prior to the period of peak settlement of barnacle larvae. It 

appears that barnacle recruitment is a precursor for recruitment of other major species common 
in the undisturbed community. Therefore, early barnacle recruitment appears to be the key to 

higher recovery rates. For this study, recovery by intertidal organisms fiom disturbances was 

not shown to be a function of wave exposure. The recruitment, successional, and recovery 

trends were similar across all sites, perhaps due to rather uniform barnacle cover, regardless of 

exposure. Although most bare space is colonized within months of being created, especially at 

exposed sites, the initial species composition is much different fiom controls, so measurement 

of total percent cover, independent of species composition, is not a good predictor of recovery 

rates fiom disturbances. 

4. In control quadrats, the data indicate a relatively stable intertidal community where the 

dominant organisms showed little inter-annual variability. Several species did exhibit intraannual variability in percent cover (i.e., differences between summer and fall) which were 

expected given their life histories. In experimental quadrats, barnacle spat densities were 

highest in the most recently scraped set and lowest in the oldest set due to less space being 

available for settlement in the older quadrats. Spat densities declined during summer and fall 

due to some combination of growth out of the size class and post-settlement mortality. For all 

sites combined, the percent cover levels for the barnacles Semibalanus balanoides and Balanus 

glandula, which had over-recruited into scraped quadrats, had not returned to control percent 

cover levels, which were usually lower, as of the last sampling date at MVDs 1.5 and 2.5. At 

MVD 3.5, the barnacle S. cariosus and the kelp Alaria spp. had not increased to control levels 

in quadrats that had more than two years to recover after being scraped. Fucus gardneri was 

also still recovering except in scraped quadrats that had 2.5 years to recover. The blue mussel 

Wtilus trossulus had not increased to control levels for all scraped quadrats combined at sites 

BB and HI as of the last sampling date. Based on the results for site HI, mussels may take much 

longer than 2.5 years to recover. As having zero means is inevitable for some species and 

quadrats in a relatively short-term study, the parametric analyses of the results need to be 

interpreted with some caution. 

5. Multidimensional scaling methods, using time of disturbance as an environmental variable, 

illustrated differences in community recovery status among quadrats scraped during different 

seasons. By September 1996, analyses indicate relative convergence of quadrats scraped in 

March 1994 and 1995, compared to quadrats scraped in July and October 1994. No direct 

relationship with recovery rate and site wave exposure was apparent fiom the MDS analyses. 

The dissimilarities of scraped quadrats compared to control quadrats were reduced between 

July 1995 and September 1996, suggesting community recovery was in progress but not 

complete after 2.5 years. 

6. We cannot provide a rigorous, statistically-based estimate of recovery time for scraped intertidal 

quadrats. Simple inspection of the data presented suggest that some species at some tidal heights 

at some locations reach control levels approximately 2 to 2.5 years after scraping but that some 

of the same species plus other species at different heights and locations did not reach control 

levels over the same period. Even for those cases where there is not a significant difference 

between scraped and control quadrats by the end of the present study, monitoring should 

continue for at least an additional two years to ensure the recovering quadrats have stabilized. 

A difficulty in making recovery estimates is the potential for additional disturbance of the 

experimental quadrats. For example, extremely cold weather coincided with very low tide series 

in 1989,1999 and 2000, usually in January. Nearly all mid to upper intertidal barnacles and 

mussels in the vicinity of the present study were killed in 1989 [Carroll 19941. Shells and tests 

of dead mussels and barnacles were still present in early April but by June they had fallen off 

and there was a heavy set of barnacle spat. Based on the results of this study, severe winter kill 

would reset the recovery process back to the beginning, with time to recovery similar to that for 
our March 1994 or March 1995 scraped quadrats in which there was early barnacle recruitment. 

However, recovery of species with poor dispersal capabilities, such as Fucus gardneri, would 

probably take much longer than suggested by our data due to the lack of nearby adult plants. Our 

estimate of the time boundaries for a community study of the type presented here would be 5-10 

years, following the latest major disturbance, whether experimental or otherwise. 

Acknowledgments 

This study was supported in part by the University of Alaska Coastal Marine Institute and the U.S. 

Minerals Management Service. Matching funds were provided by the Exron Valda Trustee Council 

through the Alaska Department of Fish and Game (Grant No. 96086-C). Data collection, data entry, 

and sample analyses fiom outer Kachemak Bay were performed with the assistance of Tracy Asselin, 

Catherine Egan, Stephanie Moreland, Tama Rucker, Steve Sklavounos, Paul Will, Jennifer Trask, Pat 

Jacobson and Gretchen Saupe. Mandy Lindeberg collected and identified algal voucher samples and 

Lauren McCarty compiled the voucher collection. Michelle Bourassa and Chirk Chu provided advice and 

programming skills for database design and statistical analyses. David Doudna managed our budget. 

Study Products 

Kachemak Bay Algal Voucher Collection: stored at the University of Alaska Fairbanks Kasitsna Bay 

Laboratory. 

Incorporation of the study sites fiom this CMI study into the NOAA HAZMAT intertidal program: 

"Epibiota sampling in Kachemak Bay", staffedlhded by Gary Shigenaka, NOAA HAZMAT and by 

Susan Saupe, Cook Inlet Regional Citizens Advisory Council. 

Highsmith, R.C., S.M. Saupe and A.L. Blanchard. 2001. Kachemak Bay experimental and monitoring 

Studies: Recruitment, succession, and recovery in seasonally disturbed rocky-intertidal habitat. Final 

Report. OCS Study MMS 2001-053, University of Alaska Coastal Marine Institute, University of 

Alaska Fairbanks, 66 p. 

Saupe, S.M., and R.C. Highsmith. 1995. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, Alaska. Oral presentation at the University of Alaska Coastal Marine 

Institute Annual Research Review, February 1995, Fairbanks. 

Saupe, S.M., and R.C. Highsmith. 1995. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, Alaska. Oral presentation at the Kachemak Bay Conference, Homer, AK. 

Saupe, S.M., and R.C. Highsmith. 1996. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, Alaska. Oral presentation at the University of Alaska Coastal Marine 

Institute Annual Research Review, February 1996, Fairbanks. 

Saupe, S.M., and R.C. Highsmith. 1997. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, Alaska. Oral presentation at the University of Alaska Coastal Marine 

Institute Annual Research Review, February 1997, Fairbanks. 

Saupe, S.M., and R C. Highsmith. 1997. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, Alaska. Watershed '97, The Cook Inlet Symposium, Anchorage. 

Saupe, S.M., and R.C. Highsmith. 1999. Recruitment and succession after disturbances to the intertidal 

zone in outer Kachemak Bay, p. 37 (abstract). In Proceedings Seventh MMS Information Transfer 

Meeting. Alaska OCS Region, Minerals Management Service, January 1999, Anchorage. 

(http://www.mms.gov/Alaskalesditm/itm99/itm.htm) 
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The Department of the lnterior Mission 

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for most of our nationally owned public lands and natural resources. This includes fostering 

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by ensuring the efficient, timely and accurate collection and disbursement of revenue from 

mineral leasing and production due to lndian tribes and aliottees, States and the U.S. Treasury. 

The MMS strives to fulfill its responsibilities through the general guiding principals of: (1) being 

responsive to the publicB concerns and interests by maintaining a dialogue with all potentially 

affected parties and (2) carrying out its programs with an emphasis on working to enhance the 

quality of life for all Americans by lending MMS assistance and expertise to economic 

development and environmental protection.