Nutrient Loading and Coastal Plankton Blooms: 

Seasonalhnterannual Successions and Effects on Secondary Production 

Robert J. Livingston 

Center for Aquatic Research and Resource Management 

136b Conradi Building, Florida State University, 

Tallahassee, Florida 32306-1 100 

Abstract-A 13-year field analysis of the Perdido Bay 

system (Gulf of Mexico) indicated that orthophosphate and 

ammonia loading from a pulp mill was associated with a series of 

plankton blooms. Bloom species (10) followed distinct seasonal 

and interannual trends that included the replacement of initial 

diatom blooms by raphidophytes and dinoflagellates. Long-term 

habitat changes associated with river flow rates (droughtlflood 

cycles) defined varying susceptibility to bloom development. The 

initiation and proliferation of plankton blooms were also affected 

by seasonal changes of temperature, phosphorus and nitrogen 

loading, and associated nutrient concentration gradients. 

Plankton blooms were associated with deterioration of secondary 

production through food web interactions. The bivalve Rangia 

cuneafa was an indicator of such effects. Most scientific efforts 

continue to overlook the world-wide impacts of anthropogenous 

nutrient loading and associated plankton blooms due to the lack 

of long-term analyses of species-specific, community-level 

phytoplankton assemblages and the replacement of ecosystem 

studies with patch-quilt ecological efforts that depend on 

disorganized and inadequate data acquisition and uncoordinated 

multidisciplinary efforts. 

I. INTRODUCTION 

River-estuarine and coastal systems are among the most 

productive areas in the world due to factors that include 

nutrient enrichment from land runoff, the shallow nature of 

the receiving system, and energy supplements in the form of 

wind, tidal currents and thermohaline circulation. 

Phytoplankton and benthic microalgae comprise the primary 

sources of organic carbon in river-dominated estuaries [l]. 

Because of high diversity, taxonomic complexity, and rapid 

reproduction rates, community interactions of coastal 

microalgae are poorly understood even though such 

organisms form the basis of many coastal food webs. 

The processes that determine primary productivity and 

resultant food webs in coastal areas vary from one system to 

the next. Ecological variability depends on factors such as 

physiography, nutrient loading, nutrient concentrations, 

temperature, salinity, wind, tides, stratification characteristics, 

currents, light transmission, and sediment characteristics. 

Biological processes such as competition and predation also 

define patterns of primary and secondary production. 

Different combinations of these variables lead to highly 

variable rates of primary production and food web responses 

from one system to the next; these processes are translated 

into major differences in population dynamics, community 

structure, and overall secondary production [2]. Despite such 

variation, the basic elements of eutrophication remain 

essentially the same whereby light energy is captured and 

redistributed into myriad forms of coastal plants and animals. 

The response of phytoplankton populations to nutrient 

loading in coastal systems has been extensively studied [3]. 

Currents and salinity can be important factors in the 

determination of diatom assemblages in coastal areas [4]. For 

example, marine diatom distribution in the Gulf of Maine was 

related to the location of large bay systems and the Georges 

Bank [5]. Anthropogenous effects on phytoplankton have 

been evaluated. For example, pulp mill effluents are known to 

cause reduced numbers of phytoplankton [6]. Cyanophycean 

types were dominant in areas of impact, with an almost total 

lack of green algae. Oscillatoria spp. were dominant in the 

polluted regions, with Rhopalodia gibberula and Nitzschia 

palea as the primary diatom species. Blue-green algae 

(Oscillatoria nigroviridis) can be indicative of waters affected 

by sewage relative to less polluted areas [7]. Low salinity 

along with the sewage effluents tended to encourage this 

species. However, blue-green algae are also abundant in 

marine areas under natural conditions [8]. A Prorocentrum 

micans bloom in a New Zealand estuary was coincident with 

increased nitrogen from upwelling [9]. However, in all of 

these studies, little consideration was given to the response of 

the phytoplankton community to nutrient loading. 

Most bloom studies are related to changes in singlespecies populations, and are usually undertaken after the 

bloom occurs. Of the approximate total number of marine 

phytoplankton species (5,000), some 300 species are known 

to occur at numbers high enough to discolor seawater [lo]. 

About 40 or 50 of these species produce toxins that can affect 

both natural marine populations of plants and animals as well 

as human beings [ 111. These so-called Harmful Algal Blooms 

or HABs have become the focus of increased research over 

the past decade as part of the perception that plankton blooms 

are increasing in both frequency and severity of impact on a 

worldwide basis. Representative groups with documented 

histories as HABs include blue green algae, diatoms, 

prymnesiophytes, dinoflagellates, and raphidophytes. 

Unfortunately, there has been little unequivocal coupling of 

microalgal concentrations and their harmful effects [ 121. 

Available background information concerning bloom 

causation and the ecological effects of HABs thus remain 

largely dependent on serial autecological studies, thus 

precluding comprehensive appraisals of how HABs are 

created and how such populations affect phytoplankton 

assemblages as a whole. 

MTS 0-933957-28-9 1973 
11. STUDYAREA 

The Perdido Bay system (Fig. 1) is a shallow to 

moderately deep inshore body of water that is approximately 

perpendicular to the Gulf of Mexico. Perdido Bay has a 

length of 53.4 km, an average width of 4.2 km, and an 

average depth of 2.2 m. The primary source of freshwater 

input to the estuary is the Perdido River system that flows 

southward about 96.5 km, draining an area of about 2937 

km2 [2]. Freshwater inflow peaks during March and April 

and is lowest in October and November. Tidal range averages 

0.2-0.3 m. The Elevenmile Creek system is a small drainage 

basin (about 70 km') that receives input from a pulp mill. 

Elevenmile Creek drains into the estuary about 1.6 km east of 

the entry point of the Perdido River in the northernmost part 

of the system. The relatively small Bayou Marcus Creek 

drains a residential area of western Pensacola with input from 

urban stormwater runoff. 

1II.MATERIALS AND METHODS 

Detailed descriptions of methods for the collection of 

physicallchemical field data have been published [13, 14, 15, 

161. Data (temperature, salinity, conductivity, Qssolved 

oxygen, pH) were taken with Datasonde 4 multiprobes (AMJ, 

Inc.). Orthophosphate analyses were based on protocols of 

the American Public Health Association [ 171. Ammonium 

was measured as ammonia with an ion electrode [18]. This 

method has essential features that allow minimal interference 

from waters highly stained with humic materials and paper 

mill effluents [13]. 

Detailed protocols for biological field and laboratory 

operations are available [2]. Whole water phytoplankton 

were taken with repetitive (3) l-L samples. Phytoplankton 

samples were immediately fixed in Lugol's solution in its 

acid version [19] and analyzed by established methods 

[20,21]. All phytoplankton cells were counted and identified 

to species or to the lowest taxonomic category possible 

(genus/order/class). Infauna (including clams) were taken 

with multiple core samples that were preserved with 10% 

formalin, identified to species, counted and weighed. 

Statistical tests were developed to compare serially 

correlated populations of numbers taken at subject stations by 

calculating differences of the observations and plotting the 

autocorrelations of the differences [2]. For independent, 

random samples from normally distributed populations, the 

parametric t-test was used to compare sample means. For 

cases where one or both of the data sets violated the 

assumption of normality, a data transformation was made to 

bring the data into normality. Alternatively, I applied the 

Wilcoxon sign-rank test to compare (0.05 confidence level) 

the two sets of numbers. Tables were constructed of the 

means where the statistical test could be run without serial 

autocorrelations. 

IV. RESULTS AND DISCUSSION 

A. River Flows and Nutrient Loading 

There were seasonal patterns of Perdido River flow 

(Fig.2), with low flows from August through December and 

high flows from January through March. Two-way 

ANOVAs, run by year and season using monthly averages 

within each season as replicates, indicated significant (P = 

0.05) differences between winter-early spring and late 

summer/fall flows. Prolonged periods of low flow occurred 

during 1988-1989, 1993-1994, and 1998-2001. The latest 

drought was the most prolonged period of low flows during 

the study period. Relatively heavy river flow events occurred 

during the winter-spring of 1990, over a prolonged period 

from spring 1995 through winter 1996, during winter 1998, 

and during the storm periods [2]. River flows during drought 

periods were significantly (P = 0.05) different from those 

during the peak years of 1990 and 1995-1996. The 

interannual trends of the drought-flood sequences represent 

an important variable that is related to water quality in 

Perdido Bay. 

Analyses of nutrient loading (ammonia, 

orthophosphate) over the 13-year sampling period (Fig. 3) 

indicated that mill orthophosphate loading was significantly 

(P=0.0212, 34.505) and positively associated with 

orthophosphate loading of Elevenmile Creek. Such loading 

remained comparable to that of the Perdido River system 

from the second quarter 1989 through the fourth quarter 

1991. There were periodic increases of orthophosphate 

loading from Elevenmile Creek during 1992-1993 that were 

accompanied by increased orthophosphate loading from the 

Perdido River. From the second quarter 1994 through the 

third quarter 1997, there were sustained increases of 

orthophosphate loading from Elevenmile Creek. High 

orthophosphate loading started during the drought of 1993- 

1994. During late summer 1997, the pulp mill reduced 

orthophosphate discharges to Elevenmile Creek. Quarterly 

orthophosphate loads reflected this effort from the final 

quarter 1997 to the second quarter 1999. There was a brief 

period of increased orthophosphate loading from the mill 

from late December 1998 through mid-January 1999. 

Following a few months of low orthophosphate loading from 

the mill, such discharges again increased in April 1999 and 

remained periodically high through August 1999. During 

September 1999, the mill resumed orthophosphate treatment 

and loading of this nutrient was again reduced during the 

period from late 1999 through summer 2001. The quarterly 

orthophosphate loading data indicated a separation of 

Elevenmile Creek values from those of the Perdido River 

system at about 50 kgP d-'. 

Elevenmile Creek was the primary source of ammonia 

to upper Perdido Bay (Fig. 3). Mill ammonia loading was 

1974 
~~ 

Fig. 1 : The Perdido Bay system showing long-term sampling stations for the long-term (13-year) field program. 

marginally (p = 0.01 15, 3 = 0.189) associated with ammonia 

loading from Elevenmile Creek. There were sustained 

increases of ammonia loading from Elevenmile Creek during 

1995-1998 and during the first 2 quarters of 2001. Ammonia 

loading from Elevenmile Creek to Perdido Bay was 

significantly higher during 1995-1998 than that of the 

preceding periods. Ammonia loading rates (i.e., beneath 300 

kg d-') were comparable to loading rates of Elevenmile Creek 

and the Perdido River system during the period of relatively 

low ammonia loading (1989 to 1991). 

B. Phytoplankton Blooms 

The spatial-temporal distribution of plankton blooms in 

the Perddo system are shown in Table 1 and Fig. 4. Species 

such as Cyclotella choctawhatcheeana Prasad, Miraltia 

throndsenii Marino et al., Leptocylindrus danicus Cleve, 

Gymnodinium splendens Lebour, and Prorocentrum 

minimum (Pavillard) Schiller were present in the bay before 

the 1993-1994 increases in nutrient loading whereas the 

diatoms Synedropsis sp. and Urosolenia eriensis (Smith) 

Round, the blue green algae Merismoedia tenuissima 

(Lemmermann) Round, and the raphdophytes (Heterosigma 

akashiwo (Hada) Hada, Chatonella subsalsa Biecheler were 

largely absent from the bay prior to such loading. The diatom 

L. danicus appeared to be a pioneer bloom species, occurring 

only once as a bloom during winter 1994. The &atom C. 

choctawhatcheeana and the dinoflagellate P. minimum 

appeared to occur bay-wide whereas other species were 

generally restricted to the upper bay. The blue green algae 

were found largely in Elevenmile Creek and bay areas at the 

mouth of the creek. 

There was a distinct species-specific pattern to the 

seasonal occurrence of the bloom species. In the upper bay, 

P. minimum and L. danicus were restricted to winter peaks 

whereas the raphidophytes H. akashiwo and C. subsalsa 

occurred during warm months of the year. The diatoms C. 

Choctawhatcheeana and M. throndsenii bloomed mainly 

during spring months while Synedropsis sp. bloomed during 

the summer. The raphidophyte and blue green algae blooms 

occurred later in the interannual bloom succession, and there 

was evidence that H. akashiwo displaced C. 

choctawhatcheeana when it reached bloom numbers. There 

were also differences in percent dominance between 

numerical abundance and biomass transformations of the 

data. The larger species such as H. akashiwo and P. minimum 

assumed higher dominance levels when defined as biomass 

percentages. 

1975 
10 

Fig; 2: River flow (m3sec-’) in the Perdido River and Elevenmile Creek taken monthly from October 1988 

through October 2000. Data were taken by the U. S, Geological Survey, Tallahassee, Florida (Dr. M. Franklin, 

pers. comm.). 

The state of the bay during periods of enhanced nutrient 

loading was an important factor in the origin of a bloom 

sequence. The original blooms occurred during the 1993-1994 

drought that was accompanied by bay conditions that 

enhanced bloom formation. Low turnover rates, increased 

winter temperature and salinity, and increased water clarity 

appeared to be important variables in the generation of the 

phytoplankton blooms, A summer flood durilig 1994 

effectively ended the previous bloom sequence, at least 

temporarily. The interannual drought-flood sequence was thus 

an important modifying factor in the response of 

phytoplankton assemblages to nutrient loading. The state of 

the bay plankton during periods of enhanced nutrient loading 

was another factor that could have contributed to the nature of 

the bloom successions. Each bloom species had a very 

different relationship to nutrient loading with obvious seasonal 

preferences for specific nutrients. Such preferences were 

consistent with the results of nutrient limitation experiments 

The relative (numerical) dominance of the different 

phytoplankton bloom species proved to be a reliable indicator 

~31. 

of community response. The relationships that could affect 

species interactions such as toxic effects, predation, 

competition for light and nutrients, and crowding, probably 

changed seasonally and interannually, thereby altering the 

response of the bloom species to nutrient loading trends. 

These effects could have been enhanced by phytoplanktoninduced water quality changes (i.e., nutrient concentration 

shifts, reduced dissolved oxygen, altered light transmission 

characteristics, increased pH)[2]. Nutrient concentration 

gradients as fresh water entered the bay appeared to be a 

trigger for the blooms. 

Seasonal changes of plankton community indices such 

as species richness ([2] were related to the plankton 

dominance hierarchies. In addition, there was a long-term 

component whereby bloom species responded differently to 

nutrient input with time. Diatom species that appeared as 

early dominants were eventually replaced by raphidophytes 

and dinoflagellates. Species competition was evident with 

some diatoms, such as C. choctawhatcheeana, maintaining a 

higher post-bloom level of abundance even after the 

1976 
2000 

1800 

1600 

1400 

1200 

2 800 

600 

400 

200 

0 

5 1000 

COmmmmooo 0--- -CI" CIrnrnrnrnb d-bbmmm mwww wr-r-r-r-CO wCOCOa.mmmooo0 -- -- CO 00 CO CO CO m ma. m m m m m m m a. mm m a. m m m m m m a.m m m m m m m m m m a. m a. m m m m m 0 0 0 0 00 0 0 . b-~~rnd--~rnb-~~rnd--~rnb-~rn~-~~rn~-~~rnb-~~rnd--~~rnb-~~rnb-~~rnb-~~rnd--~~r

. . . . . .. . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .. . . oooooom wooooo< omooooooooory oowooooooo wowooow ooooowoo 

Quarter 

Fig. 3: Ammonia (A) and orthophosphate (B) loading from the Perdido River system (Blackwater, Styx and Perdido Rivers) and 

Elevenmile Creek averaged quarterly from October 1988 through July 2001. Loading limits based on periods of early loading 

(1988-1991) are shown with the upper and lower limits for orthophosphate representing high and low flow conditions. 

phosphorus loading was reduced. This could have been a 

response to reduced competition after other bloom species 

dropped out. Another possible long-term effect was that some 

species became more easily stimulated by lower 

concentrations of nutrients over periods of increased nutrient 

loading. It was almost as if the bay was "infected" by the 

plankton blooms so that, with time, remnants of the blooms 

remained in the bay, ready to take advantage of further 

increases in nutrient loading. It is thus possible that bloom 

species, such as C. choctawhatcheeana and P. minimum, 

which were well established in the bay prior to increased 

nutrient loading, became more sensitive to nutrient loading 

after bloom status was achieved. If true, this means that the 

effects of the blooms could persist long beyond the cessation 

of the originally high levels of nutrient loading that caused 

them in the first place. 

In summary, many factors influenced the observed 

occurrences of phytoplankton blooms in Perdido Bay. The 

timing and intensity of nutrient loadmg to the bay and nutrient 

concentrations in river-bay entry points were closely 

associated with the bloom sequences. The influence of 

increased light penetration during a drought, both as a 

response to pulp mill modifications and interannual cycles 

of drought-flood conditions, also should be appeared to be 

an important causative factor in the generation of plankton 

blooms. There were distinct bloom successions that 

followed seasonal, species-specific patterns. Some blooms 

were bay-wide in distribution; others were specific to 

different parts of the bay. The main blooms occurred in the 

upper bay, which means that longitudinal salinity gradients 

could be a factor, especially to freshwater species such as 

the blue-green algae. It is also likely that some plankton 

blooms needed altered nutrient gradients to be initiated, 

but, once formed, these blooms could have been sustained 

by nutrient loading from both anthropogenous and natural 

(river) sources as the plankton were transported down the 

bay. Nutrient loading may be complementary to the 

concentration gradients of individual nutrients as the chief 

initiating factors for blooms. 

1977 
Table 1: Occurrences of blooms (> 1x106 cells L-') in the Perdido Bay system from October 1988 through July 2001. Data 

are shown by month and year in various areas of the bay (Fig. 1) 

Month Bloom Area Bloom Soecies Bloom Year Bloom Area Bloom Soecies Bloom Year 

December 

February 

March upper M. throndsenii 1994,1997, 

April baywide C. choctawhatcheeana 1994, 1998,1999,2001 upper M. throndsenii 1999,2001 

May baywide C. choctawhatcheeana 1998,1999, 

January baywide C. choctawhatcheeana 2000,2001 

June 

July 

August 

September 

October 

November 

December 

January 

February 

March 

April 

June 

July 

August 

September 

October 

November 

December 

January 

February 

March 

April 

May 

June 

July 

August 

September 

October 

November 

December 

January 

February 

March 

April 

June 

August 

September 

October 

November 

May 

May 

JdY 

?- upper 

upper 

upper 

upper 

upper 

upper 

upper 

it 

upper 

1 1-Mile Ck 

1 1-Mile Ck 

1 1-Mile Ck 

1 1 -Mile Ck 

1 1-Mile Ck 

1 1-Mile Ck 

1 1-Mile Ck 

1 1-Mile Ck 

1 1 -Mile Ck 

1 1 -Mile Ck 

H. akashiwo 1997 

H. akashiwo 2001 

H. akashiwo 1997,1998,2000 

H. akashiwo 1998,1999 

H. akashiwo 1996 

H. akashiwo 1998 

H. akashiwo 1997,1999 

L. danicus 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

M. tenuissima 

1994 

1998,1999 

1999,2000,2001 

2000 

2000 

2000,2001 

2000 

1999,2000 

1999,2000 

1999,2000 

1997 

upper P. minimum 

lower P. minimum 

1999 

2000 

upper Synedropsis sp. 1996,1998 

upper Synedropsis sp. 1996,1997,1998 

upper Synedropsis sp. 1996 

upper U. eriensis 1998 

1978 
CYCCHO MIRTHR 0 HETAKA A CHTCFSUB m URSERI 

SYDSPNOV LEPDAN 0 PROMIN 0 GYMCFSPL * MERTEN 

25 1OOOOOOO 

20 - a 1000000 

I 

-, loo000 

10000 

1000 

100 

1 

5 

0 

10 Lc 

8 

6 

4 

2 

0 

i 

a 

Year 

10 

0.01 

0.1 1E wmm 

252 

m 

2 

cj 

m 

0 

- 

t 

5 

A 

m 

Wl m 

2 

d. m 

Year 

Fig. 4: Bloom species distribution in the Perdido Bay system as annual averages of percent numbers l-', numbers l-', percent 

biomass l-', and biomass 1-I. C. choctawhatcheeana = CYCCHO, Synedropsis sp. = SYDSPNOV, M. throndsenii = MIRTHR, 

L. danicus = LEPDAN, H. akashiwo = HETAKA, P. minimum = PROMIN, C. subsalsa = CHTCFSUB, G. splendens = 

GYMCFSPL, U. eriensis = URSERI, M. tenuissima = MERTEN. 

In any case, nutrient loading from the Perdido River 

system could have played an important role in the extent and 

duration of the plankton blooms. Any increase in the loading 

rates from the river could seriously exacerbate the bloom 

conditions in the bay. Nutrient gradients appeared to be 

involved in the some of the bloom successions. 

C. Egects of Plankton Blooms on Seconduly Production 

Previous analyses of the data [2] indicated that, after 

initiation of the blooms in 1993-1994, there was an 

immediate reduction of planktivorous infaunal 

macroinvertebrates. This group of herbivorous worms and 

bivalve mollusks, as primary biomass dominants, forms a 

major link between the microalgae and the upper 

(carnivorous) trophic levels of the bay. The loss of the 

herbivorous infauna continued, ending in the almost 

complete collapse of this important group during latter years 

of the study. There were associated reductions of the 

carnivore groups that represented the dominant epibenthic 

macroinvertebrates and fishes in the Perdido system (i.e., 

penaeid shrimp, blue crabs, sciaenid fishes). The most severe 

reductions of the overall secondary production in the bay 

occurred during a period of increasing numerical and 

biomass dominance by raphidophytes and dinoflagellates [2]. 

The bivalve Rangia cuneata, that was a droughtdominant form at upper bay stations P23, P25, and P26 

during the first few years of study (Fig. 5), had virtually 

disappeared at stations P23 and P26 during the 1993-1994 

blooms at which time relatively high numbers of this species 

were still found in the seagrass bed area (station P25) that 

remained relatively unaffected by blooms during this period. 

Following a period of reduced orthophosphate loadings by 

the mill from late 1997 through spring 1999, there was a 

partial recovery of the Rangia assemblages at the mouth of 

Elevenmile Creek (P23). 

1979 
2500 

Rangia cuneata 

Fig. 5: Means and ranges (A) and numbers m-* per station (B) of the bivalve mollusk Rangia cuneata taken monthly in 

cores at established stations in Perdido Bay from October 1988 through April 2001. 

Rangia feeds on phytoplankton and particulate organic 

matter [22], and reduction of this species in those areas of 

Perddo Bay most affected by the phytoplankton blooms could 

indicate an alteration of the trophic organization of the bay 

due to changes in the phytoplankton community. This species 

was thus viewed as an indicator species for the occurrence of 

plankton blooms. 

D. Restoration Program 

Determination of target nutrient loadings from the mill 

were made with reference to existing conditions of nutrient 

loading to upper Perdido Bay. The nutrient loading target 

analyses were carried out with models run by HydroQual, Inc. 

(T. Gallagher, pers, comm.) and calculations by S. Koelsch 

and V. Tschinkel. Targets for orthophosphate (high flow 

conditions in Elevenmile Creek) were taken from calculations 

based on quarterly nutrient loading conditions in Elevenmile 

Creek (Fig. 3). Other calculations were made to determine 

loading targets for orthophosphate during drought periods 

(7Q10 flows) of increased sensitivity of the bay to nutrient 

loading. The period 1988-1991 constituted a period of 

relatively natural conditions and a balanced food web in upper 

Perdido Bay [2]. Therefore, it was assumed that nutrient loads 

during this period would be protective of the biological 

integrity of the bay [23]. 

It was estimated that a quarterly average of 361 kg day-' 

of ammonia in the final effluent from the mill during a 7410 

1980 
low flow event would not adversely impact the biological 

integrity of Perdido Bay. A two level orthophosphate target 

was based on the flow in Elevenmile Creek with the lowest 

orthophosphate target loads imposed during periodic droughts. 

A safe orthophosphate target was determined to be 38.5 kg 

day-' during drought periods and 50 kg day-' during periods of 

river flows that exceeded non-drought flow rates. 

E. Efects of Bloom Species 

The various bloom species documented in the Perdido 

Bay system since 1994 represent a taxonomically diverse 

group dominated by diatoms, raphidophytes, dinoflagellates 

and bluegreen algae. The diatom Leptocylindrus danicus has a 

world-wide distribution in a variety of tropical coastal 

environments [24]. It is often a major constituent of spring 

phytoplankton outbursts as well as fall growing periods [25]. 

This species has been associated with red tide events in Japan 

and is believed to be harmful to caged sea trout (Cynoscion 

regalis), Atlantic salmon (Salmo salar), and smolt of coho 

salmon (Oncothuynchus butch) [2]. Another diatom, Miraltia 

throndsenii has been associated with blooms stimulated by 

effluents from sewage and industrial outfalls [26]. The diatom 

Cyclotella choctawhatcheeana responds to a combination of 

environmental factors that range along inshore-offshore 

gradients of light and nutrients with salinity as a possible 

modifying factor [2]. This species was first described from 

samples taken in the Choctawhatchee Bay system [2] where 

short chains of C. choctawhatcheeana were found during each 

month of the year. Overall, this species has a high tolerance 

for wide ranges of salinity and is stimulated by increased 

nutrient loading. 

Among the most notable of the many kinds of flagellates 

that have been recognized as components of these blooms is the 

raphidophyte Heterosigma akashiwo which frequently causes 

heavy and extensive red tide events [27]. During recent years, 

considerable attention has been focused on species of the genus 

Heterosigma as the cause of fish kills in New Zealand, Chile, 

and British Columbia [28]. There is multi-factorial control of 

blooms which, once released, have a "remarkably high degree 

of broad spectrum allelochemical allelopathic antagonisms" 

that are used against competing species and potential grazers. 

Imae et al. (1997) reported details concerning life cycle and 

bloom dynamics of Chattonella, represents a bloom genus with 

2 known fish-killing species (C. antiqua and C. marina.).[29] 

Nutrients and competitors (mainly diatoms) appear to affect the 

development of Chattonella populations. Anything interfering 

with diatom proliferation could give Chattonella an advantage. 

The dinoflagellate Prorocentrum minimum is a bloom species 

that is mostly estuarine and cosmopolitan in cold temperate to 

tropical waters. It is a toxic species associated with postulated 

shellfish poisoning and fish lulls [30]. This species can cause 

oyster (Ostrea iurida) mortality and cessation of feeding at high 

densities. Increased abundance of P. minimum also causes shell 

losses. This observation was based on feeding experiments 

where toxins from this species caused slow growth and 

mortality in shellfish [2]. Gymnodinium splendens, another 

dinoflagellate, is acutely toxic to oyster larval stages [3 11. 

F. Comparison With Other Coastal Systems 

There are virtually no detailed studies of phytoplankton 

community dynamics that have been coupled with long-term, 

detailed analyses of associated benthic and epibenthic coastal 

communities. The lack of such information has led to the 

publication of studies that purport to determine ecosystem-level 

processes when, in fact, such processes remain largely 

undetermined. 

The Chesapeake Bay system is one of the most studied 

estuaries in world. The Chesapeake was one of the prime 

sources of oysters (Crassostrea virginica) in the northern 

hemisphere [32]. The loss of most of the oyster production in 

Chesapeake Bay in recent years has been attributed mainly to 

dsease. However, plankton density in Chesapeake Bay has 

been such that seagrass beds have been reduced or completely 

eliminated in major parts of the system, and hypoxia at depth 

has increased. It has been hypothesized [33] that phytoplankton 

blooms have resulted, in part, from the loss of the oysters, 

which, in less polluted times, cropped most of the 

phytoplankton in a relatively short period. 

Recently, the distribution of low dissolved oxygen in the 

Chesapeake system has been extensive. Based on regression 

analyses, low D. 0. explained 42% of the benthic index of 

biotic activity [34]. Sediment contamination (i.e., toxic agents) 

accounted for 10% of the variation of this index. Residual 

variation of condition index was only weakly associated with 

eutrophication indices (total nitrogen, total phosphorus, 

chlorophyll 3) after removal of the effects of D. 0. The benthic 

condition was negatively associated with urbanization, point 

source loadings, and total nitrogen loadings. The naturally 

hypoxic condition due to stratification [35, 361 was mentioned 

as a possible cause in addition to high rates of deposition of 

particulates to the benthos [37, 381. 

An alternate hypothesis could be made concerning the 

deteriorated state of the Chesapeake system based on possible 

analogies to the results of the Perdido study. It is possible that 

nutrient loading into oligohaline portions of the estuary during 

winter-spring periods could have resulted in a series of 

plankton blooms in succeeding months that could have been 

translated into disjunct food web relationships and deterioration 

of the benthic communities. It is highly likely that hypoxia was 

a contributing factor during warm periods, but that basic 

alterations of the bay continued throughout the entire year with 

observed deterioration reflecting years of accumulated impacts 

due to bloom proliferation. Thus, dmolved oxygen, while an 

important contributing factor, could have been only part of the 

problem relative to the condition of the bay. Indeed, recent 

unpublished reports indicate the presence of toxic plankton 

blooms in Chesapeake Bay. The deterioration of the oyster 

industry in the Chesapeake system could thus be the result of 

altered phytoplankton communities due to anthropogenous 

nutrient loading and bloom formation. 

undergone extensive deterioration [39]. The Florida Bay 

situation, however, can only be understood within the context 

of the long-term, systematic destruction of the Kissimmee 

River-Lake Okeechobee-Florida Everglades-Florida Bayi 

Over the past decade, seagrass beds in Florida Bay have 

1981 
Florida Keys/Reefs system over the past half-century [40]. The 

Kissimmee River has been virtually destroyed by the U. S. 

Army Corps of Engineers as part of an extensive and largely 

successful operation to channelize the river. Currently, Lake 

Okeechobee is undergoing extensive blue green algae blooms 

due to cultural eutrophication based, in part, on erratic control 

of lake water levels and the loading of agricultural wastes (high 

in nutrients) into the lake. Major parts of the Florida Everglades 

have been destroyed by hydrological alterations by the U. S. 

Army Corps Engineers and nutrient (i.e., phosphorus) loadmg 

by agricultural interests. Florida Bay recently experienced algal 

blooms and corresponding losses of seagrass beds in major 

parts of the bay. There has been a general deterioration of 

Florida Bay between 1987 and 1991 [41]. For the past 3-4 

decades, the Florida Keys have undergone massive 

urbanization with very little in the way of regulation regarding 

water or sediment quality relative to urban runoff. The 

associated hermatypic reefs of south Florida are in a state of 

decline with recent reports of extensive algal growths. 

Despite a series of relatively well-funded studies that have 

been undertaken in Florida Bay in recent years, the factors that 

are responsible for the observed habitat deterioration of this 

system remain “poorly known” [40]. The deterioration of 

Florida Bay was at one time, considered to be associated with 

the anthropogenous destruction of the natural flow of 

freshwater from the Everglades into Florida Bay and rampant 

urbanization of the Florida Keys. However, the almost 

complete lack of relevant nutrient loading information and 

water quality data prior to the algal blooms contributed to 

confusion regarding the causes and effects of the observed 

losses of seagrass beds. A review of the Florida Bay research 

[42] indicated that algal blooms predated the seagrass die-offs, 

and that such deterioration may have been initiated by longterm increases of land-based nutrient loadmg somewhere in the 

system. This possible explanation was in direct conflict with 

other findings [4 11 that associated blooms with preceding 

deterioration of the seagrass beds. 

Another hypothesis of researchers in Florida Bay that is 

purported to explain the seagrass deterioration in Florida Bay is 

that reduced flow from the Everglades led to hypersaline 

conditions, which, in turn, caused the seagrass die-offs [43,44]. 

This hypothesis was used as the rationale for pumping fresh 

water in to Florida Bay [44]. However, there was little temporal 

or spatial correlation between high salinity and the seagrass 

losses [44]. Observational information indicated gradual 

deterioration from 198 1-1 986 with major declines starting in 

1987. The algal blooms persisted during the 1990’s long after 

the effects of the seagrass die-offs would have been effective if 

indeed they contributed to the blooms. The spatial distribution 

of the phytoplankton blooms was not consistent with the 

seagrass &e-off hypothesis. Inorganic nitrogen concentrations 

were highest in eastern sections of Florida Bay from 199 1 - 1999 

whereas average concentrations of total phosphorus (TP) 

occurred farther west [36]. These concentrations were not 

located in the same areas of the seagrass die-offs, 

There is evidence that the nutrient-rich water from 

Florida Bay makes its way into the coral reefs thus associating 

the Florida Bay situation with the macroalgal overgrowth of the 

coral reefs [45, 461. The loss of 100,000 acres of seagrass beds 

in Florida Bay in 1987 was associated with the coral loss (up to 

44%) at the Looe Key National Marine Sanctuary (LKNMS) by 

1991 [45]. Due to the “restoration” effort of increased water 

loading to the bay between 1991 and 1995, bay-wide salinity 

decreased by 44% while ammonium, chlorophyll 8, and 

turbidity increased significantly. This increase was mirrored by 

significant increases of dissolved inorganic nitrogen (DIN) and 

chlorophyll 3 at the LKNMS and further losses of corals due to 

infestations of coralline algae and macroalgae. Increased 

nutrient loading into Florida Bay from both the Shark River 

Slough and Taylor Slough during 1982-1985 is a more logical 

explanation for the seagrass die-offs than the hypersalinity 

hypothesis [47]. There is evidence that nitrogen loading from 

agricultural and urban runoff into the Florida Everglades has 

increased in recent years, and that the implications of such 

loading to Florida Bay and the Florida Keys has not been 

adequately assessed [40]. 

Studies of the Chesapeake and Florida areas are merely 

representative of research efforts world-wide. The problem 

concerning coastal research today lies in the systematic 

assumption by many aquatic ecologists that an ecosystem 

analysis can be successfully carried out based on a series of 

disconnected, short-term studies by diverse research interests 

that operate more or less independently of one another. The loss 

of ecologically unique coastal ecosystems continues, often 

without even the semblance of coordinated scientific efforts to 

determine causation and possible restoration. The current 

situation, that involves proposed restoration projects that can be 

measured in $billions, has been due, in part, to an almost 

complete lack of a systematic ecosystem approach leading to a 

reasonable base of information. The situations in Chesapeake 

Bay and Florida Bay are merely indicative of the inadequacy of 

“ecosystem-level” projects in coastal areas around the world. 

The almost blind adherence to a failed patch-quilt approach to 

ecosystem research by funding agencies, scientific journals, and 

the reductionist researchers who dominate these agencies has 

resulted in massive and continuing destruction of coastal 

systems. There is a need for comprehensive, long-term studies 

that include detailed evaluations of phytoplankton assemblages 

and the role of plankton blooms in the deterioration of coastal 

ecosystems. 

Acknowledgments 

Dr. A. K. S. K. Prasad and Dr. K. Rhew carried out 

phytoplankton taxonomy and systematics. Robert L. Howell, 

IV, ran the field collections and infauna identification. Mr. G. 

C. Woodsum designed the overall database organization and, 

together with Mr. P. Homann, ran database management and 

day-to-day data analysis and presentation. Dr. D. A. Flemer 

designed the overall approach for analytical chemistry. 

1982 
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