# Nutrient Loading and Coastal PlanktonBlooms: Seasonalhnterannual Successions and Effects on Secondary Production

Robert 

### J. Livingston Center for Aquatic Research and Resource Management 136b Conradi Building,Florida StateUniversity, Tallahassee, Florida 32306-1 100

Abstract-A 13-year field analysis of the Perdido Bay system (Gulf of Mexico) indicated that orthophosphate and ammonia loadingfrom a pulp millwas associatedwith 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) definedvarying susceptibility to bloom development.The initiationand proliferationofplankton bloomswere also affected by seasonal changes of temperature, phosphorus and nitrogen loading, and associated nutrient concentration gradients. Plankton blooms were associatedwith deteriorationofsecondary production through food web interactions. The bivalve Rangia cuneafawas 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 disorganizedand inadequate data acquisitionand 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 ofmany 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, stratificationcharacteristics, 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 formsof 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 Gulfof 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

### knownto 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 ofthese speciesproduce toxins that can affect both natural marine populations ofplants and animals as well

as human beings [111. These so-calledHarmful Algal Blooms

or 

### HABs have become the focus of increased research over the past decade as part ofthe 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 

### 197311. 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 lowestin October andNovember. Tidalrange 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 intothe estuaryabout 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 drainsa residential area ofwestern 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 allowminimal 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 andweighed. Statistical tests were developed to compare serially correlatedpopulations

### ofnumberstaken at subject stationsby 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 transformationwas 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. RESULTSAND DISCUSSION



### A. River

### Flowsand NutrientLoading

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 studyperiod. 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 duringthe stormperiods [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 stationsfor 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 duringthe 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 ofElevenmile 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 speciessuch as 

### H. akashiwo andP. 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 duringthe 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 interannualdrought-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 couldhave contributed to the nature of the bloom successions. Each bloom species had a very different relationshipto nutrientloading 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



### 19762000
1800
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## Quarter Fig. 3: Ammonia (A) and orthophosphate (B) loading fromthe Perdido River system (Blackwater,

### Styx and PerdidoRivers) and Elevenmile Creek averaged quarterlyfrom October 1988through 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 concentrationsin 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 ofthe 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 forblooms.



### 1977Table 

### 1: Occurrences 

### ofblooms (> 

### 1x106cells 

### L-') in the Perdido Bay system from October 

### 1988 through July 

### 2001.Data

are 

### shownby 

### month 

### and year 

### invarious areas

### ofthe bay 

### (Fig. 

### 1)

Month BloomArea Bloom Soecies BloomYear BloomArea Bloom Soecies BloomYear December

February March upper M. throndsenii 1994,1997, 1999,2001 April baywide C.choctawhatcheeana 1994, 1998,1999,2001 upper M. throndsenii 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

11-MileCk 11-MileCk 11-Mile

### Ck 1 1 -MileCk 11-MileCk

11-MileCk 11-MileCk 11-MileCk 1 1

-Mile Ck 1 1

-MileCk 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 Synedropsissp. 1996,1998 upper Synedropsissp. 1996,1997,1998
upper Synedropsissp. 1996

upper U.eriensis 1998



### 1978CYCCHO 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

0.1

# 1E

0.01

wmm 

### 252m 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 importantrole 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 involvedin the some of the bloom successions.

C.EgectsofPlanktonBloomson SecondulyProduction

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, sciaenidfishes). 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).



### 19792500 

## Rangia cuneata

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

coresat established stationsin PerdidoBay 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 affectedby the phytoplankton blooms could indicate an alteration of the trophic organization of the bay due to changesin the phytoplanktoncommunity. 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 conditionsin 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 relativelynatural conditions and a balancedfood web in upper Perdido Bay [2]. Therefore,it was assumed that nutrient loads during this period would be protective of the biological integrity ofthe bay [23]. It was estimated that a quarterly averageof 361kg day-' of ammonia in the final effluent from the mill during a 7410



### 1980low 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 

### ofBloom 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 diatomLeptocylindrus 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 specieshas been associatedwith 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 (Oncothuynchusbutch) [2]. Another diatom,Miraltia throndsenii has been associated with blooms stimulated by effluentsfrom 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 attentionhas 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 Chattonellapopulations. Anything interfering with diatom proliferation could give Chattonellaan advantage. The dinoflagellateProrocentrum 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 (Ostreaiurida)mortalityand cessation of feeding at high densities.Increased abundance ofP.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 [311. 

### F. ComparisonWith Other CoastalSystems

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 phytoplanktonin 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, chlorophyll3) after removal ofthe 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 ishighly 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 loadingand 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 KissimmeeRiver-Lake Okeechobee-Florida Everglades-Florida Bay

### i

Overthe past decade, seagrassbeds in Florida Bay have



### 1981Florida 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 lakewater levels and the loading of agriculturalwastes (high in nutrients) intothe 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 declinewith recent reports of extensive algal growths. Despitea series ofrelativelywell-funded studies that have been undertaken in FloridaBay 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, consideredto 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 [411 that associated blooms with preceding deterioration

### ofthe seagrass beds. Another hypothesis of researchers in Florida Bay that is purported to explain the seagrassdeteriorationin FloridaBay is that reduced flow from the Everglades led to hypersaline conditions,which, in 

### turn,caused the seagrassdie-offs [43,44]. This hypothesis was used as the rationale for pumping fresh
water in to Florida Bay [44].However, there was littletemporal

or spatial correlation between high salinity and the seagrass losses [44]. Observational information indicated gradual deterioration from 1981-1 986 with major declines starting in 1987. The algal blooms persisted during the 1990’s long after the effects of the seagrassdie-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 easternsectionsof FloridaBay from 199 1 

### -1999 whereas average concentrations of total phosphorus (TP) occurred farther west [36]. These concentrations were not locatedin the same areasof the seagrassdie-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 100,000acres of seagrass beds in Florida Bay in 1987 was associated with the coral loss (upto 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 operatemore 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 involvesproposed restoration projects that can be measured in $billions, has been due, in part, to an almost completelack of a systematic ecosystem approach leadingto 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 analyticalchemistry.



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## 1984