Marine Pollution Bulletin 62 (2011) 596–601

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Marine Pollution Bulletin

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Harmful algal bloom species and phosphate-processing effluent:Field and laboratory studies

Matthew Garrett a,⇑, Jennifer Wolny b, Earnest Truby a, Cynthia Heil a, Charles Kovach c

a Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, 100 8th Avenue SE, Saint Petersburg, FL 33701, USAb Florida Institute of Oceanography, 830 1st Street S, Saint Petersburg, FL 33701, USAc Florida Department of Environmental Protection, 13051 N. Telecom Parkway, Temple Terrace, FL 33637, USA

a r t i c l e i n f o

Keywords:Harmful algal bloomsKarenia brevisPhosphate-processing effluentTampa BayBioassay

0025-326X/$ - see front matter � 2010 Elsevier Ltd.doi:10.1016/j.marpolbul.2010.11.017

⇑ Corresponding author. Tel.: +1 727 896 8626; faxE-mail address: matt.garrett@myfwc.com (M. Garr

a b s t r a c t

In 2002, the Florida Department of Environmental Protection began discharging phosphate-processingeffluent into Bishop Harbor, an estuary within Tampa Bay. Because of concerns that the effluent wouldserve as a nutrient source for blooms of the toxic dinoflagellate Karenia brevis, a field monitoring programwas established and laboratory bioassays were conducted. Several harmful algal bloom (HAB) species,including Prorocentrum minimum and Heterosigma akashiwo, were observed in bloom concentrationsadjacent to the effluent discharge site. Blooms of diatoms were widespread throughout Bishop Harbor.K. brevis was observed with cell concentrations decreasing with increasing proximity to the effluent dis-charge site. Bioassays using effluent as a nutrient source for K. brevis resulted in decreased cell yields,increased growth rates, and increased time to log-phase growth. The responses of HAB species withinBishop Harbor and of K. brevis to effluent in bioassays suggested that HAB species differ in their responseto phosphate-processing effluent.

� 2010 Elsevier Ltd. All rights reserved.

1. Introduction

More than 75% of the phosphate fertilizer produced in the USoriginates from natural Hawthorne deposits of phosphatic ore incentral Florida, a region that has supported a phosphate miningindustry since 1888 (Pittman, 1990). Florida phosphate companiesemployed almost 7000 people in the Tampa Bay area in 2001(Breeze, 2002) and had an economic impact of $5.9 billion (Hoppe,2005). In 2001, as a result of bankruptcy, the Mulberry Corpora-tion abandoned the Piney Point phosphate plant, located adjacentto Bishop Harbor in southern Tampa Bay (Fig. 1). The State ofFlorida was then left to dispose of more than 1.9 billion liters ofnutrient-rich effluent stored in above ground, unlined phospho-gypsum stacks at the facility. Phosphate plant effluent, a byprod-uct of the fertilizer manufacturing process, consists of radioactivephosphorus, heavy metals, and acidic ammonium nitrogen com-pounds (Kennedy et al., 1992). Instabilities in the aging phospho-gypsum stacks of the Piney Point phosphate plant, along withpotential increases in wastewater volume from heavy rainfallduring Florida’s wet season, increased the likelihood of a massivespill of untreated wastewater into Tampa Bay. Methods of dispos-ing of the large volume of wastewater, including trucking to local

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: +1 727 550 4222.ett).

sewage-treatment plants for use as reclaimed water, and reverse-osmosis filtering, proved to be inadequate or cost-prohibitive. InJuly 2002, the Florida Department of Environmental Protection(FDEP) authorized the release of wastewater treated to reducephosphorus, metals, and radiologicals (double-lime-treated) intoBishop Harbor via pipeline at the rate of 1.9 million liters perday, which continued until January 2003, when heavy rains forcedthe FDEP to increase the discharge rate to 7.6 million liters perday. Because of the continuing threat of a wastewater spill intoTampa Bay and the detection of algal blooms in Bishop Harbor,the US Environmental Protection Agency in April 2003 grantedan emergency permit to the FDEP allowing transport by barge ofwastewater to an area greater than 74 km offshore of the mouthof Tampa Bay. The transport and dispersal of 2 billion liters ofwastewater occurred from July to December 2003 at a location222 km offshore of Tampa Bay.

The input of a large volume of nutrient-rich wastewater fromPiney Point raised concerns both about the degradation of waterquality in Tampa Bay and about an increase in the occurrence ofharmful algal blooms (HABs) in the region. The Tampa Bay estuaryhas been characterized by substantially improved water quality inthe past 15 years due to nutrient reductions derived from a regio-nal nutrient control management plan (Greening and Janicki, 2006;Morrison et al., 2006). The central west coast region of Florida issubject to almost annual blooms of Karenia brevis. K. brevis is anaturally occurring toxic dinoflagellate responsible for massive fish

Fig. 1. Map of study area. Map of Bishop Harbor, Tampa Bay area and sites monitored during the discharge of effluent from the Piney Point phosphate plant, with distancefrom the outfall indicated for each site.

M. Garrett et al. / Marine Pollution Bulletin 62 (2011) 596–601 597

kills in Florida coastal waters and has direct impacts on bothhuman and environmental health (Steidinger et al., 1998).Although these blooms initiate 18–64 km offshore, well out ofthe range of the influence of coastal nutrient inputs, the bloomscan be transported shoreward, and their coastal maintenancestages can persist in nearshore regions as long as 21 months(Steidinger et al., 1998). K. brevis can use both inorganic and organ-ic nitrogen and phosphorus compounds. Blooms are supported bydiverse nutrient sources, including estuarine, atmospheric, andbenthic sources (Vargo et al., 2008); nutrients derived from zoo-plankton grazing (Lester, 2005); decomposing fish from fish kills(Walsh et al., 2006), and from nitrogen-fixing cyanobacteria suchas Trichodesmium (Mulholland et al., 2004). Vargo et al. (2008) esti-mated that as much as 20% of the nitrogen and 80% of the phospho-rus required to support these nearshore blooms may be derivedfrom estuarine sources.

Concerns about HABs, specifically the impact on a K. brevisbloom, caused by the Piney Point effluent discharge necessitatedthe establishment of a monitoring program in Bishop Harbor dur-ing the discharge period. Changes in composition of natural phyto-plankton populations were monitored during the period ofcontrolled effluent discharge into Bishop Harbor, and laboratorybioassays were conducted to examine the effects of effluent onthe growth of K. brevis. Here we present data addressing the rela-tionship between the effluent discharged into Bishop Harbor andthe observed differential stimulation or repression of differentHAB species.

2. Methods

2.1. Bishop Harbor HAB monitoring

Water samples were collected every 2 weeks at four stations inBishop Harbor (Fig. 1). The stations were located at 0.3, 1.4, 2.3, and3.2 km from the effluent discharge site. Bishop Harbor water sam-ples were examined for HAB species from March 2002 throughSeptember 2005. Discharge of Piney Point wastewater was initi-ated in July 2002. Samples were collected by submerging a 250-ml plastic bottle 5 cm below the water surface and allowing thebottle to fill from depth. Sample bottles were wrapped in wetnewspaper, placed in a cooler, and returned to the laboratory with-in 2 h of sampling. Samples were examined live on the day of col-lection for taxonomic identification of all algal species. Of each livesample, 125 ml was preserved with Lugol’s iodine at a 1% final con-centration for enumeration. Preserved subsamples were gentlymixed by inversion 20 times, then 3 ml were pipetted into a Lab-Tek coverglass chamber (Nunc #155380) and allowed to settlefor at least 30 min prior to examination. Phytoplankton, includingall potentially toxic or harmful microalgae, were identified to spe-cies level when possible.

2.2. K. brevis effluent bioassays

Effluent water was collected in May 2005 for laboratory bioas-say experiments using K. brevis. Water was taken from the final

Table 2List of toxic, harmful, or nuisance phytoplank-

598 M. Garrett et al. / Marine Pollution Bulletin 62 (2011) 596–601

stage of the wastewater processing and thus chemically repre-sented the effluent being discharged into Bishop Harbor. Effluentwater was collected in 20-L plastic carboys that had been cleanedwith 10% HCl and rinsed three times with deionized water. Effluentwas stored in the dark at 4 �C for no more than 2 weeks before usein the bioassays. Immediately before use, the effluent was sterile-filtered with a 0.2-lm (Nucleopore) filter and chemically analyzedfollowing methods for water chemistry set forth in EPA Title 40,Code of Federal Regulations, Part 136 (US Environmental Protec-tion Agency, 2003). The chemical characteristics of the effluentused in the bioassays are given in Table 1. Direct measurementsof orthophosphate were not made because it was assumed themajority of the total phosphorus measured existed as orthophos-phate, and that Bishop Harbor is a nitrogen-limited system (Wanget al., 1999).

Stock cultures of K. brevis (CCFWC #257) used in the bioassayexperiments were maintained in general purpose (GP) growthmedium (Loeblich, 1975) at 26 �C at 100 lE m�2 s�1. Sterile filtered(0.2 lm) natural seawater (36‰) used to prepare GP medium andas a seawater control, was collected 78 km offshore of Tampa Bayduring times when K. brevis blooms were not occurring in the area.Experimental treatments were run in triplicate and consisted ofsterile-filtered seawater supplemented with effluent such thatthe final concentrations of effluent in treatments were 20%, 10%,5%, and 2%. Salinities of the four treatments following effluentadditions were 29‰, 32‰, 35‰, and 36‰, respectively, and all fellwith the range for near optimal growth, (Magaña and Villareal,2006). Two control groups were run in conjunction with treat-ments, one containing only sterile-filtered natural seawater, theother containing sterile-filtered natural seawater supplementedwith GP growth medium. Controls were run in duplicate, withsalinities adjusted to match those of the four effluent treatmentsby the addition of sterile deionized water. Treatments and controlswere run in 500-ml Erlenmeyer flasks, with 400 ml of either treat-ment or control water. Flasks were randomly arranged in an incu-bator on a 12:12:L:D cycle at 100 lE m�2 s�1 and 26 �C. At the startof the experiment, K. brevis concentrations in treatment and con-trol flasks were approximately 2.0 � 104 cells L�1. Bioassays wererun for 10 days.

Flasks were swirled gently to ensure homogeneity and 10 mlsubsamples were collected for determination of cell concentra-tions. Subsamples were collected every 6 h for the first 48 h, andthen every 24 h for the remainder of the study period. Cellconcentrations were monitored for 10 days. Subsamples were

Table 1Chemical characterization of effluent water collected for effluent bioassays withKarenia brevis cultures.

Parameter Unit September 3, 2003 May 11, 2005

Temperature (�C) 27.4 13.9Specific conductance (ls cm�1) 71 77pH 7.2 6.87Turbidity (NTU) 0.1 1.4Total suspended solids (mg L�1) 1.8 3.2Dissolved oxygen (mg L�1) 4.8 5.42NH4 (as N) (mg L�1) 3.18 1.44NH4 (un-ionized) (mg L�1) 0.0153 0.0101Total Kjeldahl nitrogen (mg L�1) 4.37 2.16NO3 + NO2 (mg L�1) 0.786 2.64Total nitrogen (mg L�1) 5.16 4.81Total phosphorus (mg L�1) 3.14 3.92PO4 (mg L�1)a n/d n/dFluoride (mg L�1) 1.04 0.415

n/d: not determined.a Although PO4 concentrations were not measured on dates of effluent collection

for experiments, the PO4 concentration of effluent water was 39 mg P/L during thecourse of discharge into Bishop Harbor from 2002 to 2005.

immediately preserved with Lugol’s iodine solution. Within 1 weekof collection the preserved material was examined with anOlympus CK30 microscope. Subsamples were inverted 20 timesto mix, and 1.0 ml or 0.1 ml of material was withdrawn and wasallowed to settle for at least 30 min in a 24-well tissue-cultureplate (Costar #3524) and examined.

The growth rate (k0) of K. brevis was calculated as the natural logof (N2/N1)/(t2–t1), where N1 and N2 were the cell concentrations attimes t1 and t2, and t1 and t2 were the beginning and ending timesof the exponential growth interval obtained by visual examinationof the plot of cell concentration vs. time. Growth rate, as divisionsper day (div day�1), was calculated as k0/ln2. Lag period (time untilonset of log phase) was also obtained by visual examination of theplot of cell concentration vs. time. Final cell yield was determinedfor each treatment from cell counts in Lugol’s-preserved samplesover the full course of the experiment.

Statistical differences between treatments in the time beforeonset of the log phase and in cell yield were tested by an analysisof variance (ANOVA) with fixed factors of treatment (effluent, GPgrowth medium, and sterile-filtered seawater) and salinity (29‰,32‰, 35‰, and 36‰). Differences in growth rate were testedaccording to treatment and salinity by an analysis of covariance(ANCOVA) including water treatment as the fixed, categorical var-iable and salinity as the continuous covariate. Differences wereconsidered significant at p < 0.05.

3. Results

3.1. Bishop Harbor discharge

During monitoring over the course of the discharge, a variety ofharmful microalgal species were noted in Bishop Harbor (Table 2).Algal blooms were dominated by dinoflagellate species, althoughdiatom and raphidophyte species also achieved bloom concentra-tions (>1.0 � 105 cells L�1).

Three patterns of HAB occurrence were noted in relation to thedistance from the effluent discharge location (Fig. 2). Severaldinoflagellate and raphidophyte species bloomed in the greatestconcentration at the station 0.3 km from the discharge site anddeclined in concentration with increasing distance from the outfall.

ton species detected during routine monitor-ing in Bishop Harbor during the period ofdischarge of effluent water.

DinophyceaeAkashiwo sanguineaAlexandrium cohorticulaAlexandrium monilatumCeratium hircusGonyaulax digitaleGonyaulax veriorKarenia brevisKarenia mikimotoiKarenia sp.Kryptoperidinium foliaceumPeridinium quinquecorneProrocentrum minimumProrocentrum rhathymumPyrodinium bahamense

BacillariophyceaeChaetoceros spp.Pseudo-nitzschia spp.

RaphidophyceaeChattonella subsalsaHeterosigma akashiwo

Heterosigma akashiwo

0.00E +001.00E +062.00E +063.00E +06

4.00E +065.00E +066.00E +067.00E +06

0.3km 1.4km 2.3km 3.2km

Prorocentrum minimum

0.00E +00

5.00E +06

1.00E +07

1.50E +07

2.00E +07

2.50E +07

0.3km 1.4km 2.3km 3.2km

Pseudo-nitzschia spp.

0.00E +00

5.00E +04

1.00E +05

1.50E +05

2.00E +05

2.50E +05

0.3km 1.4km 2.3km 3.2km

Karenia brevis

0.00E +005.00E +031.00E +041.50E +042.00E +042.50E +043.00E +043.50E +04

0.3km 1.4km 2.3km 3.2km

Cells/L

Cells/L

Cells/L

Cells/L

a b

c d

Fig. 2. Distribution of harmful algal bloom species relative to the effluent outfall site in Bishop Harbor. Relative abundance reported as cells L�1 for the duration of eachbloom.

M. Garrett et al. / Marine Pollution Bulletin 62 (2011) 596–601 599

These species did not maintain high concentrations for more than aweek (<1 week), except Heterosigma akashiwo (Fig. 2a) andProrocentrum minimum (Fig. 2b), whose blooms lasted as long as5 weeks. Potentially harmful diatom species (e.g., Chaetocerosspp. and Pseudo-nitzschia spp.) were present in varying bloom con-centrations from mid-April through mid-September but displayedno spatial relationship to the discharge site. An example of the dis-tribution of Pseudo-nitzschia spp. during a spring–summer bloom ispresented in Fig. 2c. K. brevis displayed the opposite pattern whencompared to other dinoflagellate and raphidophyte HAB speciesobserved in this study. A K. brevis bloom was transported into low-er Tampa Bay from coastal waters on 15 January 2004. Wind andtides transported the bloom into Bishop Harbor on 21 January2004. The bloom lasted for 1 month, during which concentrationsof K. brevis were highest at the station farthest from the dischargesite (3.2 km) and declined with proximity to the discharge site(Fig. 2d). K. brevis was not detected at the discharge site duringthe bloom. At 3.2 km from the discharge site K. brevis concentra-tions increased from 1 � 103 cells L�1 to 9.5 � 104 cells L�1 duringthe bloom.

Table 3Influence of salinity and treatment on time before onset of log phase, cell yield, andgrowth rate of Karenia brevis.

Treatmenta Salinity Growth rate Time to log (±SD) Cell yield (±SD)(‰) k0 (div day�1) (day) (cells L�1)

GP 29 0.71 0.25 ± 0.00 2.4 � 105 ± 4 � 103

GP 32 0.43 0.38 ± 0.18 1.9 � 105 ± 1 � 104

GP 35 0.37 0.38 ± 0.18 1.9 � 105 ± 2 � 103

GP 36 0.37 0.38 ± 0.18 2.1 � 105 ± 5 � 104

FSW 29 0.93 0.38 ± 0.18 4.0 � 104 ± 5 � 103

FSW 32 0.53 0.75 ± 0.00 6.5 � 104 ± 2 � 104

FSW 35 0.58 0.88 ± 0.18 7.9 � 104 ± 2 � 104

FSW 36 0.72 0.75 ± 0.00 7.1 � 104 ± 1 � 104

Effluent 29 0.60 1.83 ± 0.29 8.4 � 104 ± 2 � 104

Effluent 32 0.81 1.75 ± 0.025 9.0 � 104 ± 1 � 104

Effluent 35 0.99 1.67 ± 0.029 8.8 � 104 ± 7 � 103

Effluent 36 1.22 1.67 ± 0.29 6.3 � 104 ± 2 � 104

a Treatments consisted of GP growth medium (GP), sterile-filtered (0.2 lm)seawater (FSW), and filtered (0.2 lm) effluent (Effluent). Salinities were adjustedwith sterile deionized water to the value listed for each treatment.

3.2. K. brevis effluent bioassays

Cell concentrations (cells L�1) were determined initially every6 h to document time to log-phase growth and the exponentialgrowth phase, and then every 24 h to monitor stationary-phasegrowth and decline. Average growth rate for the four salinitieswas greatest in the effluent treatments (0.91 div day�1), least inthe GP growth medium treatments (0.47 div day�1), and inter-mediate in the sterile-filtered-seawater treatments (0.69 divday�1). The average time to onset of exponential growth for the foursalinities was longest in the effluent treatment (1.73 days), shortestin the GP growth media treatment (0.35 days), and intermediate inthe filtered-seawater treatment (0.69 days). Average cell yieldswere greatest in the GP growth medium treatments (2.1 �105 cells L�1), least in the filtered-seawater treatments (6.4 � 104

cells L�1), and intermediate in the effluent treatments (8.1 � 104

cells L�1). Table 3 presents the growth rates, time to onset ofexponential growth, cell yields, and standard deviations calculatedfor the bioassays.

ANOVAs showed that treatment had a significant effect(p < 0.0001) on time to onset of log-phase growth but that salinitydid not (p = 0.5860); ANOVAs also stated that treatment had a sig-nificant effect (p < 0.0001) on cell yield but that salinity did not(p = 0.8187). ANCOVA analyses states that a significant differenceexisted between treatments (p = 0.0037) and between salinityand treatment (p = 0.0024).

4. Discussion

The relationship between eutrophication and the occurrence ofHABs is complex. A variety of factors, including HAB species, bloomlocation, circulation patterns, hydrology, and trophic dynamics,can play a role in the initiation and maintenance of blooms ofdifferent species (Anderson et al., 2008). Increases in the amountof nutrients entering coastal, estuarine, and marine ecosystemshave long been recognized to result in increases in phytoplanktonbiomass (as chlorophyll a) (Nixon, 1995; Anderson et al., 2002).Glibert and Burkholder (2006) suggested that the quality (i.e.,form) of nutrient inputs may be significant in determining thecomposition of the phytoplankton community, and stimulation of

600 M. Garrett et al. / Marine Pollution Bulletin 62 (2011) 596–601

HABs because different HAB species use organic and inorganicnutrient pools differently. Evidence presented here further sup-ports this differential stimulation of HAB species.

Three types of responses to the effluent were observed duringmonitoring for HABs in Bishop Harbor. Within 2 weeks of initiationof effluent discharge, a large bloom of the macroalga Ulva sp. hadoccurred. More than 90.7 tones of Ulva spp. were mechanically re-moved from Bishop Harbor (FDEP, unpublished data). All subse-quent algal blooms in Bishop Harbor during discharge consistedof microalgae. Blooms of the dinoflagellate P. minimum and theraphidophyte H. akashiwo in Bishop Harbor during effluent dis-charge were ephemeral (�1 month in duration), with the greatestcell concentrations found adjacent to the effluent discharge site.These species are natural components of Tampa Bay and have abroad salinity tolerance. However, P. minimum (Glibert et al.,2001; Heil et al., 2005) and H. akashiwo (Honjo, 1993; Smaydaet al., 2004) have been documented in other coastal systems to re-spond rapidly to changes in nutrient concentration, and blooms ofUlva spp. have been directly linked with effluent outfall (Harlin,1993).

A second type of response is represented by the harmful or nui-sance diatom genera observed in Bishop Harbor. The distribution ofPseudo-nitzschia spp. displayed no apparent spatial relationshipwith the effluent discharge location during the five-month bloom.Because the Pseudo-nitzschia spp. bloom was not concentrated atthe effluent outfall, its growth was probably not limited by a nutri-ent component of the effluent, nor was the effluent water dis-charged into the harbor inhibitory toward its growth. The abilityof diatoms including Pseudo-nitzschia spp., to achieve and sustaina large biomass in Bishop Harbor was probably a function of theirability to take up nitrogen rapidly and outcompete other groups ofphytoplankton. Similar opportunistic growth patterns have beenreported for diatom populations during nutrient loading eventsin other Gulf of Mexico estuaries (Örnólfsdóttir et al., 2004;Pinckney et al., 2009).

A third response type is represented by the distribution ofK. brevis, which was present in Bishop Harbor only when tidallyintroduced from a bloom in lower Tampa Bay. During the monthin which K. brevis was present in Bishop Harbor, its abundancedecreased with increasing proximity to the effluent discharge site.K. brevis cells observed in water samples from Bishop Harbor weremorphologically distorted, with a rounded plasmolemma and lossof the cloverleaf shape characteristic of healthy K. brevis cells.Similar morphologically aberrant K. brevis cells have been observedupon exposure to suboptimal conditions for growth (Wilson, 1966)and when exposed to salinities <24‰ (Maier-Brown et al., 2006).This suggests that the effluent did not provide the conditionsneeded for growth by this species, causing cell stress and prevent-ing the bloom from increasing in concentration and geographicalextent within the harbor. A salinity effect was discounted sincethe average salinity during the course of the K. brevis bloom inBishop Harbor was 29‰ and never less than 27‰ (data notshown).

In the bioassays, although the growth rates of K. brevis cells inthe effluent treatments were greater than in the GP growth med-ium or sterile-filtered-seawater treatments, the cells in the effluenttreatments had a longer lag phase. Shortly after log-phase growthof K. brevis began, a sharp decline in cell numbers occurred in alleffluent treatments, regardless of salinity. This boom-and-bustgrowth curve is not a trend observed in monitoring of extensiveK. brevis blooms along the west Florida coast (Steidinger et al.,1998). Moreover, cell yields in the GP growth medium treatmentswere greater than those in effluent treatments. Therefore, althoughthe K. brevis cultures grown in the effluent treatments were able togrow at a faster rate, not only did they never reach the biomass ofthe cultures of the GP growth medium treatments, they also never

reached a stationary or maintenance growth phase, at least overthe duration of the bioassays. The long lag phase for the effluenttreatments compared with that of the GP growth media treat-ments, further suggests that addition of effluent resulted in subop-timal conditions for sustaining a K. brevis bloom. Differences insalinity had no statistically significant effect on the three growthvariables examined.

These results suggest that elevated concentrations of anthropo-genic nutrients related to phosphate-processing effluent are not di-rectly linked with coastal K. brevis blooms but may be implicated inblooms of other HABs in Florida bays and estuaries. The decay andregeneration processes of other algal blooms may provide nutri-ents to support coastal K. brevis blooms, as hypothesized by Walshet al. (2006). The specific compound or compounds within theeffluent that influenced these HAB species was not identified.However, in 2003, nutrient-limiting algal growth studies per-formed using Piney Point effluent indicated that phosphorus wasthe primary limiting nutrient and nitrogen was the secondary lim-iting nutrient (FDEP, unpublished data). Greening and Janicki(2006) describe Tampa Bay as a nitrogen-limited system. Thisscenario provided an opportunity to examine the response ofeuryhaline HAB species to nutrient inputs on a local scale. Growthof P. minimum and H. akashiwo growth was stimulated, but thegrowth of K. brevis was inhibited.

5. Summary

Different HAB species exhibited different growth responses tothe presence of effluent resulting from the manufacture of phos-phate fertilizer. Some species (P. minimum and H. akashiwo) formedephemeral, high-concentration blooms adjacent to the effluentoutfall site, while others (Pseudo-nitzchia spp.) exhibited no rela-tionship between bloom and proximity to effluent outfall. Thered-tide dinoflagellate K. brevis, which blooms extensively in thecoastal waters of southwest Florida, showed an inverse relation-ship between cell abundance and proximity to the effluent outfall.Moreover, laboratory bioassays in which K. brevis cultures weretreated with effluent resulted in suboptimal conditions for growthand maintenance of a bloom. The findings in this study support thehypothesis that phosphate-processing effluent can have a differen-tial influence on the growth of various HAB species.

Acknowledgments

Financial and logistic support was provided by the FloridaDepartment of Environmental Protection and the Florida Fish andWildlife Conservation Commission. The authors thank Erin Leonefor assistance with statistical analyses, Jacob Tustison for assis-tance with graphics, Dr. Bill Richardson for assistance with labora-tory work and logistical support, and Michael Dirks and KevinHarkinson for assistance with field work.

References

Anderson, D., Glibert, P., Burkholder, J., 2002. Harmful algal blooms andeutrophication: nutrient sources, composition, and consequences. Estuaries25, 704–726.

Anderson, D., Burkholder, J., Cochlan, W., Glibert, P., Gobler, C., Heil, C., Kudela, R.,Parsons, M., Rensel, J., Townsend, D., Trainer, V., Vargo, G., 2008. Harmful algalblooms and eutrophication: examining linkages from selected coastal regions ofthe United States. Harmful Algae 8, 39–53.

Breeze, M., 2002. Public knowledge and attitudes regarding the Florida phosphateindustry and related issues. University of Florida publication, #00-PUB-184.

Glibert, P., Burkholder, J., 2006. The complex relationships between increasingfertilization of the earth, coastal eutrophication, and HAB proliferation. In:Graneli, E., Turner, J. (Eds.), The Ecology of Harmful Algae. Springer-Verlag, NewYork, pp. 341–354.

M. Garrett et al. / Marine Pollution Bulletin 62 (2011) 596–601 601

Glibert, P., Magnien, R., Lomas, M., Alexander, J., Fan, C., Haramoto, E., Trice, T., Kana,T., 2001. Harmful algal blooms in the Chesapeake and coastal bays of Maryland,USA: comparison of 1997, 1998, and 1999 events. Estuaries 24, 875–883.

Greening, H., Janicki, A., 2006. Toward reversal of eutrophic conditions in asubtropical estuary: water quality and seagrass response to nitrogen loadingreductions in Tampa Bay, Florida, USA. Environmental Management 38, 163–178.

Harlin, M., 1993. Changes in major plant groups following nutrient enrichment. In:McComb, J. (Ed.), Eutrophic Shallow Estuaries and Lagoons. CRC Press, Inc., BocaRaton, pp. 173–187.

Heil, C., Glibert, P., Fan, C., 2005. Prorocentrum minimum (Pavillard) Schiller: areview of a harmful algal species of growing worldwide importance. HarmfulAlgae 4, 449–470.

Honjo, T., 1993. Overview on bloom dynamics and physiological ecology ofHeterosigma akashiwo. In: Smayda, T., Shimizu, Y. (Eds.), Toxic PhytoplanktonBlooms in the Sea. Elsevier, Amsterdam, pp. 33–41.

Hoppe, M., 2005. Phosphate at the crossroads. Bay Soundings 4, 8–10.Kennedy, G., Soroczak, M., Meischen, S., Clayton, J., Driver, J., 1992. Chemistry of

gypsum systems. Florida Institute of Phosphate Research publication, #85-05-025R.

Lester, K., 2005. Zooplankton of the West Florida Shelf: relationships with Kareniabrevis blooms. Ph.D. Dissertation, University of South Florida.

Loeblich, A., 1975. A seawater medium for dinoflagellates and the nutrition ofCachonia niei. Journal of Phycology 11, 80–86.

Magaña, H., Villareal, T., 2006. The effect of environmental factors on the growthrate of Karenia brevis (Davis) G. Hansen and Moestrup. Harmful Algae 5, 192–198.

Maier-Brown, A., Dortch, Q., Van Dolah, F., Leighfield, T., Morrison, W., Thessen, A.,Steidinger, K., Richardson, B., Moncreiff, C., Pennock, J., 2006. Effect of salinity onthe distribution, growth, and toxicity of Karenia spp.. Harmful Algae 5, 199–212.

Morrison, G., Sherwood, E., Boler, R., Barron, J., 2006. Variations in water clarity andchlorophyll a in Tampa Bay, Florida, in response to annual rainfall, 1985–2004.Estuaries and Coasts 29, 926–931.

Mulholland, M., Heil, C., Bronk, D., O’Neil, J., Bernhardt, P., 2004. Does nitrogenregeneration from the N2-fixing cyanobacteria Trichodesmium spp. fuel Kareniabrevis blooms in the Gulf of Mexico? In: Steidinger, K., Landsberg, J., Tomas, C.,Vargo, G. (Eds.), Harmful Algae 2002. Proceedings of the 10th InternationalConference on Harmful Algae. Florida Fish and Wildlife Conservation

Commission, Florida Institute of Oceanophgraphy, and IntergovernmentalOceanographic Commission of UNESCO, pp. 47–49.

Nixon, S., 1995. Coastal marine eutrophication: a definition, social causes, andfuture concerns. Ophelia 41, 199–219.

Örnólfsdóttir, E., Lumsden, S., Pinckney, J., 2004. Phytoplankton community growth-rate response to nutrient pulses in a shallow turbid estuary, Galveston Bay,Texas. Journal of Plankton Research 26, 325–339.

Pinckney, J., Wee, J., Hou, A., Walker, N., 2009. Phytoplankton community structureresponses to urban effluent inputs following hurricanes Katrina and Rita.Marine Ecology Progress Series 387, 137–146.

Pittman, W., 1990. The Florida phosphate industry. Fertilizer Research 25, 193–196.Smayda, T., Borkman, G., Beaugrand, G., Belgrano, A., 2004. Ecological effects of

climate variation in the North Atlantic: phytoplankton. In: Stenseth, N.,Ottersen, G., Hurrell, J., Belgrano, A. (Eds.), Ecological Effects of ClimateVariations in the North Atlantic. Oxford University Press, pp. 49–54.

Steidinger, K., Vargo, G., Tester, P., Tomas, C., 1998. Bloom dynamics and physiologyof Gymnodinium breve with emphasis on the Gulf of Mexico. In: Anderson, D.,Cembella, A., Hallegraeff, G. (Eds.), Physiological Ecology of Harmful AlgalBlooms. Springer-Verlag, Berlin, pp. 133–153.

US Environmental Protection Agency, 2003. Title 40 Code of Federal Regulations,Part 136. Available from: <http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div5&view=text&node=40:22.0.1.1.1&idno=40/>.

Vargo, G., Heil, C., Fanning, K., Dixon, L., Neely, M., Lester, K., Ault, D., Murasko, S.,Havens, J., Walsh, J., Bell, S., 2008. Nutrient availability in support of Kareniabrevis blooms on the central West Florida Shelf: what keeps Karenia blooming?Continental Shelf Research 28, 73–98.

Walsh, J., Jolliff, J., Darrow, B., Lenes, J., Milroy, S., Dieterle, D., Carder, K., Chen, F.,Vargo, G., Weisberg, R., Fanning, K., Muller-Karger, F., Steidinger, K., Heil, C.,Prospero, J., Lee, T., Kirkpatrick, G., Whitledge, T., Stockwell, D., Tomas, C.,Villareal, T., Joachens, A., Bontempi, P., 2006. Red tides in the Gulf of Mexico:where, when and why? Journal of Geophysical Research 111, C11003.doi:10.1029/2004JC002813.

Wang, P., Martin, J., Morrison, G., 1999. Water quality and eutrophication in TampaBay, Florida. Estuarine, Coastal and Shelf Sciences 49, 1–20.

Wilson, W., 1966. The suitability of sea-water for the survival and growth ofGymnodinium breve Davis and some effects of phosphorus and nitrogen on itsgrowth. Florida Conservation Board, Florida State University Professional PaperSeries, Report #7.