# Oyster monitoring in the northern estuaries on the Southeast coast of Florida 2008 Annual Report

Melanie L. Parker Stephen P. Geiger

Florida Fish and Wildlife Research Institute 100 Eighth Avenue SE St. Petersburg, Florida 33701

June 25, 2009

Contract Number: 4600001084 File Code: F2724-08-A12 TABLE OF CONTENTS

Executive Summary ........................................................................................................3 Introduction .................................................................................................................5
Methods ......................................................................................................................8 Results..... ............................................................................................................................................12 St. Lucie Estuary

............................................................................................................................... ..............12 SLE Figures.............................................................................................................16 Loxahatchee River........................................................................ .....................................................32 LOX Figures....................................................................................................35 Lake Worth Lagoon

............................................................................................................................... .........50 LWL Figures....................................................................................................53 Discussion

................................................................................................................................. ....................60 References

................................................................................................................................... .................673 Executive Summary In this report we present the 2008 observations by the Molluscan Fisheries research group at the Florida Fish and Wildlife Resear ch Institute (FWRI) on oysters in southeast Florida. The main objective of this project is to continue a long-ter m monitoring program intended to document the response of oysters, Crassostrea virginica , in south Florida to CERP activities. FWRI monitored changes in oyster ecology at six sites in three estuaries in southeast Flor ida: the St. Lucie estuary (3 sites), the Loxahatchee River (2 sites) and Lake Worth Lagoon (1 site). Four aspects of oyster ecology were monitored: spatial and size distribution patterns of adult oysters, distribution and frequency patterns of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX), reproduction and recruitment, and juvenile oyster growth. Water quality parameters including salinity, temperature and chlorophyll a concentrations were also monitored at each study site. Salinities in the St. Lucie estuary (SLE) were n ear the optimal range (15-20 ppt) for oyster survival and recruitment success during the first six mont hs of the year, decreased ra pidly in July leading to the subsequent oyster die-off at a ll sites in the fall and recovered qu ickly enough to to allow successful settlement of the last recruits of the year. Salinities in the Loxahatchee River (LOX) were near the optimal range (15-20 ppt) for oyster survival and recruitment success in early months of the year, but throughout the rest of the year salinities were erratic and often eith er too high (increased predation and disease) or too low. Salinity was highly variable in the Lake Worth Lagoon (LWL), but was generally higher than salinities recorded in the other estuaries. Oysters were abundant at all nine stations in S LE during the spring 2008 survey but declined dramatically by the fall survey and were limited to only a scattering of live oysters in central estuarine reefs. Oyster densities at both the LOX and LW sites were high and increased from spring to fall 2008. Dermo infection was consistently present in oysters from the LOX and LWL study sites. Oysters from the St. Lucie-Central study site also had a consistent presence of the parasite until salinities substantially declined in late summer. However, infection intens ity levels were low throughout the year in oysters sampled from all sites. Reproductive development in creased steadily through sp ring in the SLE and LOX study sites Both estuaries exhibited a spring and fall peak in recruitment. In contrast, gametogenesis was delayed and increased more rapidly in the LWL study site. Recruitment in LWL was much higher and had4 a single peak which lasted for several months. Juvenile growth rates were high in both the SLE and the LOX. Observed juvenile growth rate was low in Lake Worth, but may have been biased by the continual recruitment of small oysters to the population.5 Introduction The Comprehensive Everglades Restoration Program (CERP) has been implemented as a means of reinitiating, to the greatest degree possible, natural freshwater flow to coastal waters on both coasts of south Florida. The Monitoring and Assessment Program (MAP) component of CERP is designed to provide a diverse approach to documenting and describing the impacts of changed freshwater flow to the flora and fauna inhabiting inland landscapes and coas tal waters. Because of their wide distribution, historical context, and essential habitat value, the eastern oyster ( Crassostrea virginica ) is included as a target species for monitoring. Oyster beds provide important habitat for numerous organisms and are indicators of a healthy estuary. Changes in the spatial extent and health of oyster beds in southeast Florida estuaries are key performance measures that will help a ssess the success of CERP. The eastern oyster occupies estuarine and nearshor e habitats throughout the eastern and Gulf of Mexico coasts of the United States. This animal su pported a subsistence fishery even before European colonization of the United States (MacKenzie et al., 1 997), and throughout recent history has provided an important economic and cultural resource to coastal inhabitants. In addition to its direct economic benefits, the oyster also provides essential habitat for many other estuarine inhabitants (Bahr and Lanier, 1981). The eastern oyster is one of the most culturally, economically, and ecological ly important residents of U.S. coastal waters. In Florida, oysters occur along bo th the Atlantic and Gulf of Mexico coasts in almost all estuarine and nearshore waters. Along the Atla ntic coast, oysters are generally confined within bays and lagoons such as Lake Worth Lagoon or the Indian River. Thes e areas are expected to experience changes in water quality, quantities and timing due to the implementation of the C-44 and Indian River Lagoon – South CERP components. Those waters, and other coastal waters on the southeast coast of the state, have experienced altered patterns of water delivery and quality as a result of water management practices related to the St. John’s River and Kissimmee River basins, Lake Okeechobee, and the Everglades. In particular, the redirection of freshwater out of those inland ba sins and into the coastal waters mentioned above has altered both the timing and the range of salinity variation in those coastal waters. Alterations in freshwater flow have reduced or eliminated many oyster reef areas and have impacted both the timing and extent of oyster reproduction (Berrigan et al., 1991). The diverse community associated with the oyster reefs has6 been impacted to an equivalent or greater degree. Monitoring in th e St. Lucie estuary, the Loxahatchee River, and Lake Worth Lagoon began in 2003 to esta blish pre-restoration conditions to assess and evaluate any changes related to the implementation of the previously mentioned restoration components. The main objective of this project is to continue a long-term monitoring program intended to document the response of oysters, Crassostrea virginica , in south Florida to CERP activities. The Molluscan Fisheries research group at the Florida Fish and Wildlife Research Institute (FWRI) in conjunction with Dr. Aswani Volety at Florida Gulf Co ast University (FGCU) monitored changes in oyster distribution and abundance at a variety of sites on the Atlantic and Gulf of Mexico coasts of south Florida. Six sites in three estuaries in southeast Florida were monitored by FWRI (Figure 1): the St. Lucie estuary (3 sites), the Loxahatchee River (2 sites) and Lake Worth Lagoon (1 site). The Caloosahatchee River and nearby Ten Thousand Islands were monitored by FGCU. The data collected by FWRI and FGCU use methods that, to the greatest degree possible, ensure the resultant data from these contemporaneous projects are statistically and conceptually comparable. Four aspects of oyster ecology are monitored: spatial and size distribution patterns of adult oysters, distribution and frequency patterns of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX), reproduction and recruitment, and juvenile oyster growth. In this report we present the 2008 observations by FWRI on oysters in southeast Florida.7 Figure 1 . CERP oyster monitoring study sites and stations on the east coast of Florida.8 Methods Study Sites Oyster sampling occurred on oyster reefs within th ree estuarine ecosystems on the southeast coast of Florida that included the St. Lucie estuary, the Lo xahatchee River, and Lake Worth Lagoon. Within the St. Lucie estuary, we considered the north fork, the so uth fork, and the central estuary to be separate sites and we sampled three oyster reefs (= stations), or th ree potential oyster reef locations if no oysters were present, within each of thos e sites. Similarly, in the Loxahatchee River, we considered the south fork and the northwest fork to be separate sites and we sampled three oyster reefs within eac h of those sites. Three oyster reefs were also selected as st udy sites within Lake Worth Lagoon. This strategy resulted in a total of six separate study sites (St. Lucie-North, St. Lucie-Central, St. Lucie-South, Loxahatchee-North, Loxahatchee-South, and Lake Worth) each with three stations (i.e., oyster reefs) that were monitored. Station locations can be seen in Fi gure 1, and coordinates for each sampli ng reef are provided in Table 1.

Table 1 . Station locations for CERP oyster monitoring sites in southeast Florida. Site Station Latitude o N Longitude o W St. Lucie North Fork 1 27 13.232 80 16.737 St. Lucie North Fork 2 27 12.686 80 15.846 St. Lucie North Fork 3 27 12.459 80 17.072 St. Lucie Central Estuary 1 27 12.743 80 14.599 St. Lucie Central Estuary 2 27 12.087 80 14.493 St. Lucie Central Estuary 3 27 12.096 80 15.282

St. Lucie South Fork 1 27 11.691 80 15.636 St. Lucie South Fork 2 27 11.228 80 16.149 St. Lucie South Fork 3 27 09.949 80 15.671 Loxahatchee NW Fork 1 26 58.164 80 07.688 Loxahatchee NW Fork 2 26 58.237 80 07.649 Loxahatchee NW Fork 3 26 58.370 80 07.686 Loxahatchee SW Fork 1 26 56.574 80 07.112 Loxahatchee SW Fork 2 26 56.630 80 07.280 Loxahatchee SW Fork 3 26 56.560 80 07.257

Lake Worth Lagoon 1 26 40.181 80 02.618 Lake Worth Lagoon 2 26 38.848 80 02.436 Lake Worth Lagoon 3 26 35.851 80 02.417
Adult Sampling Adult sampling was conducted in the late spring and fall of 2008. On each sampled reef, we haphazardly deployed fifteen replicate 1/4-m 2 quadrats and harvested all oysters within each quadrat for9 determination of the number of live and dead oysters w ith articulated shells. A maximum of 10 live oyster shell heights (SH = maximum linear distance from the umbo to the ventral shell margin) were also measured from each quadrat.

Reproductive and Disease Monitoring Oysters were collected for analysis of physiolo gical condition, gonadal de velopment state, and for the prevalence and intensity of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX) on a monthly basis. A sample of ten oysters from each of the three reefs with in a study site (total N = ten oysters x three reefs x six sites = 180 per month if live oysters were available at all stations) were transported, live and chilled, to the FWRI laboratory for processing. Ea ch individual oyster was measured (SH mm), shucked, and the tissues processed for reproductive stage, disease status and physiological condition according to the methods described below. For condition analysis, five of the oysters collected from each station within a site were processed by thoroughly cleaning each individual, measuring the shell height, weighing the whole animal, then shucking each oyster and obtaining th e tissue wet weight. The shells and tissues were dried for 48 hours and then the shell and tissue dry weights were recorded . Oyster condition index was calculated as the ratio of tissue dry weight to shell dry weight. The rema ining five animals collected from each station were processed for reproductive and disease analysis.
For Perkinsus marinus (dermo) disease analysis, prevalence and intensity was diagnosed with Ray’s fluid thioglycollate method (RFTM) as described by Bushek et al. (1994). Small (1 cm 2 ) pieces of gill and mantle tissue were incubated in RFTM media with antibiotics for seven days in the dark at 25 o C. Tissue pieces were then placed onto glass microscope slides, macerated with razor blades, stained with Lugol’s, and examined at 400x for the presence of hypnospores. Parasite density (infection intensity) was ranked using the Mackin scale, which ranges from 0 to 5 (Table 2). Average parasite densities were calculated for each sample

. For reproductive and MSX diseas e analyses, the remaining oyster tissue was preserved in Dietrich’s fixative solution (Barber, 1996). Following 20 hours of fixation, the oyster tissues were10 Table 2 . Mackin scale showing different stages of Perkinsus marinus (dermo) infection intensity. Stage Category Cell Number Notes

0 Uninfected No cells detected 0.5 Very light <10 cells in entire preparation

1 Light 11-100 cells in entire preparation Cells scattered or in localized clusters of 10-15 cells 2 Light-moderate Cells distributed in local concentrations of 24-50 cells; or uniformly distributed so that 2-3 cells occur in each field at 100X 3 Moderate 3 cells in all fields at 100X Masses of 50 cells may occur 4 Moderate heavy Cells present in high numbers in all tissues Less than half of tissue appears blueblack macroscopically 5 Heavy Cells in enormous numbers Most tissue appears blue-black macroscopically
thoroughly rinsed in tap water and preserved in 70% ethanol for subsequent histological preparation. Histological preparation consisted of dehydrating each oyster in 95% ethanol for a minimum of three hours, then embedding the tissue in paraffin. Depending upon the size of the individual oyster, a minimum of one to a maximum of six 3.5 micrometer sections were cut from each embedded sample using a microtome mounted with a glass knife, maintaining a minimum separation of 60 micrometers (the approximate maximum diameter of an oocyte) between sections. The sections were stained with hematoxylin and eosin, and then mounted onto pre-labeled glass slides for an alysis. Resultant slides were examined at 200-400x on a compound microscope and each sample was assigned to a reproductive stage following the classification scheme (Table 3) modifi ed from the work of Fisher et al. (1996). Finished slides were also examined at 100x for the presence of MSX parasites.

Spat Recruitment Juvenile oyster recruitment wa s monitored at each of the reefs within each study site. Three replicate spat monitoring arrays were deployed and retrieved at each station on a monthly schedule. Each array consisted of 12 axenic adult oyster shells (5 -10 cm SH) strung onto two separate lengths of galvanized wire. The shells were oriented with th eir inner surface facing downward when suspended off the bottom, and spat recruitment was estimated by count ing the number of settled sp at on the underside of the strung shells.11 Table 3 . Qualitative reproductive staging criteria for oysters collected from Florida waters. Value Observations

__________________________________________________________ 0 Neuter or resting stage with no visible signs of gametes 1 Gametogenesis has begun with no mature gametes 2 First appearance of mature gametes to approximately one-third mature gametes in follicles 3 Follicles have approximately equal proportions of mature and developing gametes 4 Gametogenesis progressing, but follicles dominated by mature gametes 5 Follicles distended and filled with ripe gametes, limited gametogenesis, ova compacted into polygonal configurations, and sperm have visible tails 6 Active emission (spawning) occurring; general reduction in sperm density or morphological rounding of ova 7 Follicles one-half depleted of mature gametes 8 Gonadal area is reduced, follicles two-thirds depleted of mature gametes 9 Only residual gametes remain, some cytolysis evident 10 Gonads completely devoid of gametes, and cytolysis is ongoing

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Juvenile Growth Monitoring Juvenile growth monitoring was initiated at each study site in March 2008. Growth arrays were constructed of 12.7-mm-mesh plastic-coated wire mesh with dimensions of approximately 0.6-m L x 0.6-m W. On each of these growth arrays, 25 adult, axenic oyster shells were attached by fishing line to serve as substrate for wild juvenile oysters. Cage sampling in volved measuring the shell heights of 30 haphazardly selected live oysters (or all live oysters if <30). Th is monitoring was conducted in concurrence with the monthly recruitment sampling at all sites. Monitoring of juvenile oyster growth continued until February 2009 at all sites.

Water Quality Monitoring Monthly water quality sampling was conducted in conjunction with field sampling at all stations within each study site. Recorded parameters includ ed water depth, temperature, salinity, turbidity, pH, dissolved oxygen concentration and chlorophyll a concentration. Water depth was determined with a sounding line and turbidity was obtained using a standard Secchi disk. All other parameters were measured with a YSI 6820 multi-parameter data logger.12 Results St. Lucie Estuary Adult Sampling During the spring oyster survey in May 2008, mean live oyster densities exceeded 100 m -2 at all sampled stations in the north fork, the central estuary and at one station in the south fork (Figure 2). These live densities were among the highest recorded in the St. Lucie estuary since the start of our oyster monitoring program in early 2005. Mean shell heights of these oysters ranged from approximately 50 to 80 mm (Figure 3) suggesting that oysters were surviving many months and thus achieving larger sizes. Unfortunately, storm activity coupled with water releases into the estuary caused salinities to fall below 5 ppt at all stations in September and October. As a result, during the fall survey in October 2008, we found that oyster populations were completely decimated in the north and south forks and reduced by approximately 99% in the central estu ary. Numbers of dead oysters gr eatly increased and almost mirrored the live densities that were present duri ng the previous spring survey (Fig ure 2). Because only dead oysters with articulated shells are counted during our surv eys, some recently dead oysters may not have been accounted for in the north fork. Oysters in this study site are pr esent in clumps rather than in a more traditional benthic reef structure. When oysters in th ese areas die-off, the she lls become disarticulated much more rapidly than would typically occur at a reef site. As previously mentioned, not all oysters were lost in the central study site. However, mean shell heights at these three stations only ranged from approximately 5 to 14 mm (Figure 3). The small size of these oysters suggests that they were actually new recruits that were able to settle onto the reefs be fore the end of the spawning season.

Disease Monitoring When present, live adult oysters were collected monthly from each station in the St. Lucie estuary for determination of the prevalence an d intensity of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX). However, at Station 3 in the St. Lucie-South study site, oysters were not collected during the months of January through March 2008. This was due to an oyster die-off that occurred at that station in November 2007. This di e-off can be attributed to decreased salinities resulting from increased freshwater flow into the area from the nearby canal. Oy sters were also not collected for13 analyses from all stations in all three study sites during the months of September through December 2008. This is the die-off mentioned in the previous section that resulted from a combination of local storm events and freshwater releases. Those few live oysters that su rvived and were present in the central estuary during the fall were too young to exhibit any degree of disease infection or prevalence and as such were not collected for these analyses. Dermo infection was almost absent from oysters collected from the north and south fork study sites but was present in low to moderate levels in oy sters from the St. Lucie-Central study site (Figures 4 and 5). Even these infection levels were relatively low with mean intensities remaining below 1, indicating that sampled oysters were only lightly infected w ith the parasite. The pr evalence of dermo reached moderate levels in oysters collected from the central estuary, especially at Station 1 where 60% of the oysters collected during the months of March through July were infected with dermo. Infection levels began declining in August which suggests that the lower salinities associated with the wet season were inhibiting the parasite. At this time we have found no evidence of Haplosporidium nelsoni (MSX) infection in any of the oysters coll ected from the St. Lucie estuary.

Physiological Condition and Reproductive Development When present, live adult oysters were collected monthly from each s ite in the St. Lucie estuary for determination of physiological condition and reproductiv e development. As previously mentioned, oyster collections did not occur at Station 3 in St. Lucie-Sout h from January through March and at all stations in all study sites from September through December. Reproductive tissues were sexed (neuter, male or female) and then assigned a reproductive development stage (Table 3). Analysis of gonadal tissues indicated that most oysters are in various stages of reproductive development including gametogenesis, active spawning and gonadal recycling throughout most of the year (Figures 6, 7, and 8). However, most oysters collected in January and February were found in a resting (i.e., neuter) stage with gonads completely devoid of gametes. In previous years’ stud ies, we found that oysters are in this resting state throughout the winter which would also include the month of December. Changes in physiological condition generally reflected these reproductive patterns in that condition index values were typically14 higher in the spring at the beginning of the spawning season and slowly declined throughout the summer as fall approached (Figure 9).

Spat Recruitment Juvenile oyster recruitment was monitored at each station in the estuary on a monthly basis. Three replicate spat monitoring arrays were deployed at each station for a period of approximately 28 days and then collected and returned to the lab for processing. Larval recruitment is reported as the mean number of spat counted per shell per month. Peak larval oyster recruitment rates occurred in July followed by a second peak in November at most stations (Figure 10 ). In St. Lucie-Central larval recruitment occurred almost continuously from April through November. The spat recorded at Station 3 in January are likely recruits from the 2007 spawning s eason. Recruitment occurred over a slightly shorter time frame in both the north and south forks ranging from May or June through November. Overall these recruitment rates are fairly low, rarely exceeding 1 spat/s hell/month. This reflects a decrease in mean recruits at most stations when compared with peak recruitment ra tes in 2006 and 2007.

Juvenile Growth Monitoring The juvenile growth monitoring component of our project was initiated in March 2008. At each station within a site, one growth array containing 25 ad ult, axenic oyster shells attached by fishing line was deployed directly on the reef or monitoring location. Each shell was checked monthly for the presence of wild oyster spat and up to 30 shell height measuremen ts were recorded at each station. Juvenile oysters first appeared in St. Lucie-Central in May, in the sout h fork in June and in the north fork in July (Figure 11). This closely corresponds to the spat recruitmen t results in that juvenile oysters were found in each study site exactly one month following the first recruits recorded in each study site. However, survival of these juveniles was short-lived as the wet season progressed and by September juveniles at most stations were dead. Fortunately, salinities recovered quickly and recruits from the last pulse of the spawning season settled onto the growth arrays in each study site. These juveniles exhib ited a rapid growth rate adding an average of over 5 mm shell height per month. When the study was completed in February 2009, the juvenile oysters had reached a mean size of approximately 30 mm shell height.15 Water Quality Monitoring Several water quality parameters were recorded in conjunction with monthly field sampling at each station. These parameters included water depth, temperature, salinity, turb idity, pH, dissolved oxygen concentration and chlorophyll a concentration. Salinity was highly variable in the estuary ranging from a low of nearly 0 ppt to almost 25 ppt throughout the year. Salinities were near the optimal range (15-20 ppt) for oyster survival and recruitment success during the first six months of the year, but decreased rapidly in July leading to the subsequent oyster die-off at all sites in the fall (Figure 12). In November, the rapid increase in salinities coincided with the last recruitment peak of the year. As a result, it’s likely that those spat will survive to grow and spawn in the 2009 and a llow for some recovery of oyster populations in the estuary. Temperatures recorded at each station in the estuary exhibite d a typical seasonal pattern with values ranging from approximately 16 o C to 32 o C over the year (Figure 13). Dissolved oxygen concentrations and pH measurements in the estuary we re as expected ranging from approximately 4 mg/L to 11 mg/L and 6.3 to 8.2 respectively (Figures 14 and 15). Chlorophyll a concentrations ranged from a minimum of 6 ug/L to a maximum of 28 ug/L (Figure 16). Turbidity in the water column is presented as a Secchi penetration value which is calculated as the percentage of the water column through which the Secchi disk could be seen. Turbid ity was low at most stations from January through August but began increasing in the fall when freshwater inputs in to the estuary increased (Figure 17).16Mean LiveOysters per m2

0 200 400 600 800 1000 St. Lucie-Central

Spring 2008 Fall 2008Mean DeadOysters per m2

0

200 400 600 800 1000Mean LiveOysters per m2

0

50 100 150 200 250 Station 1 Station 2 Station 3 St. Lucie-North

Spring 2008 Fall 2008Mean DeadOysters per m2

0 50 100 150 200 250Mean LiveOysters per m2

0

50 100 150 200 250

Spring 2008 Fall 2008Mean DeadOysters per m2

0

50 100 150 200 250 St. Lucie-South

Figure 2 . Mean number (+ S.D.) of live and dead oysters present at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites during the spring and fall 2008 surveys. Filled bars represent the number of live oysters and th e hollow bars represent the number of dead oysters with articulated shells. Please note the differences in the y-axis rang e among the different study sites.17 St. Lucie-South

Spring 2008 Fall 2008Mean Shell Height (mm)

0 20 40 60 80 100 120 Spring 2008 Fall 2008Mean Shell Height (mm)

0 20 40 60 80 100 120 Spring 2008 Fall 2008Mean Shell Height (mm)

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20 40 60 80 100 120 Station 1 Station 2 Station 3 St. Lucie-North

St. Lucie-Central 

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* * *

Figure 3 . Mean shell height (+ S.D.) of live oysters present at stati ons in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites during the spring and fall 2008 surveys. Asterisks denote stations where no live oysters were present for measurement.18 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Intensity

0 1 2 3 4 5 Station 1 Station 2 Station 3



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St. Lucie-South



### Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Intensity

0 1 2 3 4 5



## * * * * * * * * * St. Lucie-North

St. Lucie-Central



## * * * * * *

Figure 4 . Monthly mean infection intensity (+ S.D.) of oyster s infected with Perkinsus marinus at stations in the St. Lucie-North (top), St. Luci e-Central (middle) and St. Lucie-South (bottom) study sites. Asterisks denote stations where no live oysters were present for collection and disease analyses.19 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

0 20 40 60 80 100 Station 1 Station 2 Station 3

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

0 20 40 60 80 100

St. Lucie-South



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

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## * * * * * * * * * * * *

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* * * * * * * * * * * * * * * St. Lucie-North

St. Lucie-Central



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Figure 5 . Monthly mean prevalence (% ) of oysters infected with Perkinsus marinus at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites. Asterisks denote stations where no live oysters were pres ent for collection and disease analyses.20 Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes

Stage 5 - Follicles distended and filled with ripe gametes Stage 4 - Follicles dominated by mature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Stage 3 - Equal numbers of mature and immature gametes

Figure 6 . Reproductive development of oysters collected from the St. Lucie-North study site in 2008. The gray shaded areas represent the time period when live oysters were not available for collection from any of the three stations.21 Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes

Stage 5 - Follicles distended and filled with ripe gametes Stage 4 - Follicles dominated by mature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Stage 3 - Equal numbers of mature and immature gametes

Figure 7 . Reproductive development of oysters collected fr om the St. Lucie-Central study site in 2008. The gray shaded areas represent the time period when live oysters were not available for collection from any of the three stations.22 Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes Stage 4 - Follicles dominated by mature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Stage 3 - Equal numbers of mature and immature gametes

Stage 5 - Follicles distended and filled with ripe gametes

Figure 8 . Reproductive development of oysters collected from the St. Lucie-South study site in 2008. The gray shaded areas represent the time period when live oysters were not available for collection from any of the three stations.23 St. Lucie-South



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8



## * * * * * * * * * * * * Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8 Station 1 Station 2 Station 3



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* * * * * * St. Lucie-North

St. Lucie-Central

Figure 9 . Monthly mean condition index (+ S.D.) of oysters collected from stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites. Asterisks denote stations where no live oysters were present for collec tion and physiological condition analysis.24 St. Lucie-South



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 1 2 3 4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 1 2 3 4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 1 2 3 4 Station 1 Station 2 Station 3 St. Lucie-North

St. Lucie-Central

Figure 10 . Mean number (+ S.D.) of oyster recruits collected per shell each mont h from stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites.25 

### Month Ma

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0 08

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l 2

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r 2009Mean Shell Height (mm)

0 20 40 60 80Mean Shell Height (mm)

0 20 40 60 80Mean Shell Height (mm)

0 20 40 60 80 Station 1 Station 2 Station 3 St. Lucie-North

St. Lucie-South St. Lucie-Central

Figure 11 . Monthly mean shell height (+ S.D.) of wild juvenile oyster s settled onto growth arrays at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites. Growth arrays were planted in March 2008. Months with no data indicate months when no juvenile oysters were present on the growth arrays.26 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40 St. Lucie-South St. Lucie-Central

Figure 12 . Monthly salinity recorded at stations in the St. Lucie-North (top), St . Lucie-Central (middle) and St. Lucie-South (bottom) study sites.27 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40 St. Lucie-South St. Lucie-Central

Figure 13 . Monthly temperature recorded at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites.28 Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20 St. Lucie-South St. Lucie-Central

Figure 14 . Monthly dissolved oxygen concentration recorded at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lu cie-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.29 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10 St. Lucie-South St. Lucie-Central

Figure 15 . Monthly pH recorded at statio ns in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lucie-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.30 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50 St. Lucie-South St. Lucie-Central

Figure 16 . Monthly chlorophyll a concentration recorded at stations in the St. Lucie-North (top), St. Lucie-Central (middle) and St. Lu cie-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.31 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100 Station 1 Station 2 Station 3 St. Lucie-North

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100 St. Lucie-South St. Lucie-Central

Figure 17 . Monthly percent Secchi penetration recorded at stations in the St. Luci e-North (top), St. LucieCentral (middle) and St. Lucie-South (bottom) study sites.32 Loxahatchee River Adult Sampling Live oyster densities in the Loxahatchee River reached a mean of nearly 300 m -2 at all stations in the northwest fork and over 200 m -2 at two of the three stations in the south fork during the spring oyster survey in May 2008 (Figure 18). In the northwest study site, these numbers are comparable to densities seen in previous years but in the south fork these values were slightly higher with approximately 80 to 100 more live oysters m -2 present. Oyster shell heights in the Loxahatchee were similar to those from previous years with a mean size of approximat ely 40 mm in both study sites (Figure 19). During the fall survey in October 2008, live oyster densities more than doubled at all stations in the Loxahatchee-North study site yielding a mean of over 700 live oysters m -2 (Figure 18). Live densities also increased at two of the three stations in the south fork with an average of more than 300 m -2 at a Stations 1 and 3. Mean density at Station 2 did not decrease but was identical to the mean from the spring survey. In the Loxahatchee, fall mean shell heights are typically lower than those fro m the spring surveys due the presence of recently settled larval oysters. Fall 2008 was no exception with mean shell heights in the northwest fork ranging from 33 mm to 38 mm at each of the stations and in the south fork from 34 mm to 41 mm (Figure 19).

Disease Monitoring Live adult oysters were collected monthly fro m each station in the Loxahatchee River for determination of the prevalence and intensity of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX). Dermo infection was consistently present in oysters collected from both the northwest and south fork study sites. Prevalence of the disease in was moderate to high with anywhere from 7% to 67% of oysters from the northwest fork and 20% to 92% from the south fo rk infected each month (Figure 21). Howeve r, infection intensity was low with leve ls rarely exceeding a score of 1 (light infection) on the Mackin scale (Figure 20). At this time we have found no evidence of Haplosporidium nelsoni (MSX) infection in any of the oyster s collected from the Loxahatchee River.33 Physiological Condition and Reproductive Development Live adult oysters were collected monthly from each site in Loxahatchee River for determination of physiological condition and reproductive development. Reproductive tissues were sexed (neuter, male or female) and then assigned a repr oductive development stage (Table 3). Analysis of gonadal tissues indicated that most oysters are in various stages of reproductive development including gametogenesis, active spawning and gonadal recycling throughout most of the year (Figures 22 and 23). However, the majority of oysters collected in Ja nuary, February, November and Decembe r were found in a resting (i.e., neuter) stage with gonads completely devoid of gametes. Changes in physiological condition generally reflected these reproductive patterns in that condition index values were slightly higher during the winter months when oysters are able to devote energy to somatic growth (Figure 24).

Spat Recruitment Juvenile oyster recruitment was monitored at all six stations in the Loxahatchee River on a monthly basis

. Three replicate spat monitoring arrays were deployed at each station for a period of approximately 28 days and then collected and returned to the lab for processing. Larval recruitment is reported as the mean number of spat counted per she ll per month. Recruitment rates peaked twice in both study sites the Loxahatchee River. In the northwes t fork, there was a recrui tment peak in June and September while in the south fork the peaks occurred in April and September (Figure 25). In both study sites, recruitment occurred continuou sly from April th rough December. The spat recorded at 5 of the 6 stations in January are likely recruits from the 2007 spawning season. Overall, the peaks and duration of the recruitment season are comparable to rates seen in previous years at the Loxahatchee River study sites.

Juvenile Growth Monitoring The juvenile growth monitoring component of our project was initiated in March 2008. At each station within a site, one growth array containing 25 ad ult, axenic oyster shells attached by fishing line was deployed directly on the reef or monitoring location. Each shell was checked monthly for the presence of wild oyster spat and up to 30 shell height measurements were recorded at each station. Juvenile oysters first appeared in Loxahatchee-South in April and in Loxahatchee-North in May (Figure 26). This34 corresponds to the spat recruitment resu lts in that the first recruits recorded in each study site were found in April. In the northwest fork, juvenile oysters at stations 1 and 2 exhibited a moderate growth rate adding an average of 3.5 mm shell height per month while juveniles at station 3 achieved a growth rate of only 1.5 mm per month. In the south fork, growth rates were si milar to the stations 1 and 2 in the northwest site with rates ranging from 3.4 mm to 4.1 mm per month. When the study was completed in February 2009, the juvenile oysters had reached a mean size of approximately 30 mm shell height in the northwest fork and 42 mm shell height in the south fork.

Water Quality Monitoring Several water quality parameters were recorded in conjunction with monthly field sampling at each station. These parameters included water depth, temperature, salinity, turb idity, pH, dissolved oxygen concentration and chlorophyll a concentration. Salinity was highly variable in both Loxahatchee study sites ranging from a low of 2 ppt to over 30 ppt throughout the year. Salinities were near the optimal range (15-20 ppt) for oyster survival and recruitment success in early months of the year, but throughout the rest of the year salinities were erratic and often either to o high (increased predation and disease) or too low (Figure 27). Temperatures recorded at each station in the es tuary exhibited a typical seasonal pattern with values ranging from approximately 17 o C to 33 o C over the year (Figure 28). Dissolved oxygen concentrations and pH measurements in the estuary we re as expected ranging from approximately 4 mg/L to 8 mg/L and 7.3 to 8.3 respectively (Figures 29 and 30). Chlorophyll a concentrations ranged from a minimum of approximately 3 ug/L to a maximum of 30 ug/L (Figure 31). Turbidity in the water column is presented as a Secchi penetration valu e which is calculated as the percen tage of the water column through which the Secchi disk could be seen. Secchi penetra tion was 100% at all six stations in the Loxahatchee River for almost the entire year (Figure 32). The only exception was in Loxahatchee-South during the months of October and November. Even so, Secchi penetration was still greater than 75% of the water column in both months.35Mean LiveOysters per m2

0 200 400 600 800 1000 Loxahatchee-South

Spring 2008 Fall 2008Mean DeadOysters per m2

0

200 400 600 800 1000Mean LiveOysters per m2

0

500 1000 1500 2000 Station 1 Station 2 Station 3 Loxahatchee-North

Spring 2008 Fall 2008Mean DeadOysters per m2

0 500 1000 1500 2000

Figure 18 . Mean number (+ S.D.) of live and dead oysters present at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites during the spring and fall 2008 surveys. Filled bars represent the number of live oysters and the hollow bars represent the number of dead oysters with articulated shells. Please note the differences in the y-axis range between the two study sites.36 Spring 2008 Fall 2008Mean Shell Height (mm)

0 20 40 60 80 100 120 Spring 2008 Fall 2008Mean Shell Height (mm)

0

20 40 60 80 100 120 Station 1 Station 2 Station 3 Loxahatchee-North

Loxahatchee-South

Figure 19 . Mean shell height (+ S.D.) of live oysters present at sta tions in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites during the spring and fall 2008 surveys.37 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Intensity

0 1 2 3 4 5 Station 1 Station 2 Station 3



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Intensity

0 1 2 3 4 5 Loxahatchee-North

Loxahatchee-South

Figure 20 . Monthly mean infection intensity (+ S.D.) of oysters infected with Perkinsus marinus at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites.38 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

0 20 40 60 80 100 Station 1 Station 2 Station 3



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

0 20 40 60 80 100 Loxahatchee-North

Loxahatchee-South

Figure 21 . Monthly mean prevalence (% ) of oysters infected with Perkinsus marinus at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites.39% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes

Stage 5 - Follicles distended and filled with ripe gametes Stage 4 - Follicles dominated by mature gametes Stage 3 - Equal numbers of mature and immature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Figure 22 . Reproductive development of oysters collected from the Loxahatchee-North study site in 2008.40% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes

Stage 5 - Follicles distended and filled with ripe gametes Stage 4 - Follicles dominated by mature gametes Stage 3 - Equal numbers of mature and immature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Figure 23 . Reproductive development of oysters collected from the Loxahatchee-South study site in 2008.41 

### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8 Station 1 Station 2 Station 3 Loxahatchee-North

Loxahatchee-South

Figure 24 . Monthly mean condition index (+ S.D.) of oysters co llected from stations in the LoxahatcheeNorth (top) and Loxahatchee-South (bottom) study sites.42 

### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 5 10 15 20 25 Station 1 Station 2 Station 3 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 5 10 15 20 25 Station 1 Station 2 Station 3 Loxahatchee-North

Loxahatchee-South

Figure 25 . Mean number (+ S.D.) of oyster recruits collected per shell each m onth from stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites.43 

### Month Mar 2008 A

p r 2

008 Ma

y 20

0 8

Ju

n 2008 J

u l 2 00

8

Aug 2

008 S

e p 2008 O

ct 20 0 8

Nov 2 0 08

D

e c 2

00

8

Jan 2 0 09

F

e b

2 00

9 Mar 2 0 09Mean Shell Height (mm)

0 20 40 60 80Mean Shell Height (mm)

0 20 40 60 80 Station 1 Station 2 Station 3 Loxahatchee-North

Loxahatchee-South

Figure 26 . Monthly mean shell height (+ S.D.) of wild juvenile oyster s settled onto growth arrays at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites. Growth arrays were planted in March 2008. Months with no data indicate months when no juvenile oysters were present on the growth arrays.44 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40 Loxahatchee-South

Figure 27 . Monthly salinity recorded at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites.45 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40 Loxahatchee-South

Figure 28 . Monthly temperature recorded at stations in the Loxahatchee-North (top) and LoxahatcheeSouth (bottom) study sites.46 Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20 Loxahatchee-South

Figure 29 . Monthly dissolved oxygen concentration recorded at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.47 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10 Loxahatchee-South

Figure 30 . Monthly pH recorded at stations in the Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.48 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50 Loxahatchee-South

Figure 31 . Monthly chlorophyll a concentration recorded at stations in Loxahatchee-North (top) and Loxahatchee-South (bottom) study sites. Missing data is due to our malfunctioning YSI unit.49 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100 Station 1 Station 2 Station 3 Loxahatchee-North



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100 Loxahatchee-South

Figure 32 . Monthly percent Secchi penetration recorded at stations in the Loxa hatchee-North (top) and Loxahatchee-South (bottom) study sites.50 Lake Worth Lagoon Adult Sampling In Lake Worth Lagoon, mean live oyster densities during the spring survey were approximately 250 m -2 at the large reef found at Station 2, 50 m -2 at Station 1 and 20 m -2 at Station 3 (Figure 33). Spring oyster densities have been steadily decreasing in Lake Worth Lagoon over past few years with densities at Station 2 almost 50% reduced since spring 2006. In stark contrast to the spring survey, fall densities at Station 2 increased by over 4-fold with a mean density of over 1100 m -2 , while densities at the other two stations were both greater than 300 m -2 (Figure 33). This substantial in crease in live oysters can likely be attributed to the large recruitment event that occurred from the months of April through October. The influence of new recruits can be further demonstrated by comparing the mean shell heights of live oysters from both surveys. Mean shell heights of oysters at all stations in the spring were approximately 34 mm which is comparable to sizes seen in previous year s (Figure 34). However, in fall 2008 the mean shell height of oysters ranged from approximately 13 mm to 25 mm at the three stations in Lake Worth Lagoon (Figure 34).

Disease Monitoring Live adult oysters were collected monthly from each station in Lake Worth Lagoon for determination of the prevalence and intensity of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX). Dermo infection was present al most every month in oysters collected from all three stations in Lake Worth with prevalence ranging from 7% to 80% (Figure 36). Despite the persistent presence of dermo, infection intensity levels were low with scores rarely exceeding a rank of light infection on the Mackin scale (Figure 35). At this time we have found no evidence of Haplosporidium nelsoni (MSX) infection in any of the oyster s collected from the Lake Worth Lagoon.

Physiological Condition and Reproductive Development Live adult oysters were collected monthly from Lake Worth Lagoon for determination of physiological condition and reproductive development. Reproductive tissues were sexed (neuter, male or female) and then assigned a reproductive development stage (Table 3). Analysis of gonadal tissues51 indicated that most oysters are in various stages of reproductive development including gametogenesis, active spawning and gonadal recycling throughout most of the year (Figure 37). However, the majority of oysters collected in January, Februa ry, March, November and December were found in a resting (i.e., neuter) stage with gonads completely devoid of gametes. When compared to oysters from St. Lucie estuary and Loxahatchee River, this appears to be a somewhat protracted period of time for oysters to remain in the resting state. In the other estuaries, condition index values are typically higher in the winter months when oysters are devoting energy to somatic growth. In Lake Worth Lagoon oysters, condition index values exhibited the opposite pattern with peak values occurring in the summer and fall months (Figure 38). The impacts of this gonadal development pattern will be demonstrated in the following section.

Spat Recruitment Juvenile oyster recruitment was monitored at all three stations in Lake Worth Lagoon on a monthly basis. Three replicate spat monitoring arrays were deployed at each station for a period of approximately 28 days and then collected and returned to the lab for processing. Larval recruitment is reported as the mean number of spat counted per shell per month. At all three stations in Lake Worth, recruitment occurred from the months of April throug h November with peak recruitment rates occurring in August (Figure 39). This is in stark contrast to recr uitment patterns observed in the other estuaries in that they typically exhibit a bimodal pattern with peaks occurring in the both spring and fall. In previous years, recruitment patterns in Lake Worth also appeared to be bimodal but this pattern was much less pronounced than those seen in the Loxahatchee River. The reduced period of reproductive development described in the previous section is likely responsible for the recr uitment pattern observed in Lake Worth in 2008. As far as the recruitment season duration and peak recr uitment rates, the values recorded in 2008 are comparable to previous years in the Lake Worth Lagoon study site.

Juvenile Growth Monitoring The juvenile growth monitoring component of our project was in itiated in March 2008. At each station within a site, one growth array containing 25 ad ult, axenic oyster shells attached by fishing line was52 deployed directly on the reef or monitoring location. Each shell was checked monthly for the presence of wild oyster spat and up to 30 shell height measuremen ts were recorded at each station. Juvenile oysters first appeared at all stations in Lake Worth in May (F igure 40). Initial growth es timates appeared high with an average of over 10 mm of shell height added in the first month. However, after June mean sizes of juvenile oysters began decreasing. Data is missing from station 1 for the months of September and October because the growth array became untethered and drif ted behind the nearby mangrove. The growth array was relocated in November during a low tide sampling trip. When the study was completed in February 2009, the juvenile oysters had only reached a mean size of approximately 26 mm sh ell height in the Lake Worth study site.

Water Quality Monitoring Several water quality parameters were recorded in conjunction with monthly field sampling at each station. These parameters included water depth, temperature, salinity, turb idity, pH, dissolved oxygen concentration and chlorophyll a concentration. Salinity was highly variable, but generally higher than salinities recorded in other estuaries, in the Lake Wort h study site ranging from a low of 12 ppt to 35 ppt throughout the year (Figure 41). Salinities were typica lly higher than the optimal range (15-20 ppt) which likely impacted Lake Worth oysters by increasing the incidence of preda tion and disease infection (dermo). Temperatures recorded at each station in the estuar y exhibited a typical seasonal pattern with values ranging from approximately 17 o C to 31 o C over the year (Figure 42). Dissolved oxygen concentrations and pH measurements in the estuary were as expected rang ing from approximately 4 mg/L to 8 mg/L and 7.7 to 8.1 respectively (Figures 43 and 44). Chlorophyll a concentrations ranged from a minimum of approximately 3 ug/L to a maximum of 29 ug/L (Figure 45). Turbidity in the water column is presented as a Secchi penetration value which is calculated as the percentage of the water column through which the Secchi disk could be seen. Secchi penetration was 100% at all three stations in Lake Worth for almost the entire year (Figure 46). The only exception was during the months of April, September, October and November.53Mean LiveOysters per m2

0 500 1000 1500 2000

Spring 2008 Fall 2008Mean DeadOysters per m2

0

500 1000 1500 2000 Lake Worth

Figure 33 . Mean number (+ S.D.) of live and dead oysters present at stations in the Lake Worth study site during the spring and fall 2008 surveys. Filled bars represent the number of live oysters and the hollow bars represent the number of dead oysters with articulated shells.

Lake Worth

Spring 2008 Fall 2008Mean Shell Height (mm)

0 10 20 30 40 50 Station 1 Station 2 Station 3

Figure 34 . Mean shell height (+ S.D.) of live oysters present at stations in the Lake Worth study site during the spring and fall 2008 surveys.54 Lake Worth



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Intensity

0 1 2 3 4 5 Station 1 Station 2 Station 3

Figure 35 . Monthly mean infection intensity (+ S.D.) of oysters infected with Perkinsus marinus at stations in the Lake Worth study site.

Lake Worth



### Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Dermo Infection Prevalence

0 20 40 60 80 100 Station 1 Station 2 Station 3

Figure 36 . Monthly mean prevalence (% ) of oysters infected with Perkinsus marinus at stations in the Lake Worth study site.55% Frequency 0 20 40 60 80 100 Female Male Neuter

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

0 20 40 60 80 100

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 0 20 40 60 80 100 0 20 40 60 80 100

0 20 40 60 80 100 Stage 8 - Follicles 2/3 depleted of mature gametes Stage 9 - Only residual gametes remain Stage 10 - Gonads completely devoid of gametes

Stage 6 - Active spawning occuring Stage 7 - Follicles 1/2 depleted of mature gametes

Stage 5 - Follicles distended and filled with ripe gametes Stage 4 - Follicles dominated by mature gametes Stage 3 - Equal numbers of mature and immature gametes Stage 2 - Up to 1/3 mature gametes Stage 1 - Early gametogenesis

Figure 37 . Reproductive development of oysters collected from the Lake Worth study site in 2008.

Lake Worth



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Condition Index

0 2 4 6 8 Station 1 Station 2 Station 3

Figure 38 . Monthly mean condition index (+ S.D.) of oysters collected from stations in the Lake Worth study site.56 Lake Worth



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecMean Spat/Shell/Month

0 10 20 30 40 50 Station 1 Station 2 Station 3

Figure 39 . Mean number (+ S.D.) of oyster recruits collected per shell each m onth from stations in the Lake Worth study site.



### Month M

a r 2008 Apr

2

0 0 8 Ma

y 2008 Ju

n 2008 J

u l 2 008 Aug 2008 Sep 2 008 O

ct 2008 Nov 200 8

D

e c 2

0 0 8

Jan 2 0 0 9

Feb 2 009

M

a r 200 9Mean Shell Height (mm)

0 20 40 60 80 Station 1 Station 2 Station 3 Lake Worth

Figure 40 . Monthly mean shell height (+ S.D.) of wild juvenile oyster s settled onto growth arrays at stations in the Lake Worth study site. Growth arrays were planted in March 2008. Months with no data indicate months when no juvenile oysters were present on the growth arrays.57 

### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecSalinity

0 5 10 15 20 25 30 35 40

Station 1 Station 2 Station 3 Lake Worth

Figure 41 . Monthly salinity recorded at stations in the Lake Worth study site.



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTemperature (oC)

0 5 10 15 20 25 30 35 40

Station 1 Station 2 Station 3 Lake Worth

Figure 42 . Monthly temperature recorded at stations in the Lake Worth study site.58 

### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct NovDO (mg/L)

0 5 10 15 20 Station 1 Station 2 Station 3 Lake Worth

Figure 43 . Monthly dissolved oxygen concentration recorded at stations in the Lake Worth study site. Missing data is due to our malfunctioning YSI unit.



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecpH

5 6 7 8 9 10

Station 1 Station 2 Station 3 Lake Worth

Figure 44 . Monthly pH recorded at stations in the Lake Worth study site. Missing data is due to our malfunctioning YSI unit.59 

### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecChla(ug/L)

0 10 20 30 40 50 Station 1 Station 2 Station 3 Lake Worth

Figure 45 . Monthly chlorophyll a concentration recorded at stations in Lake Worth study site. Missing data is due to our malfunctioning YSI unit.



### Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec% Secchi Penetration 0

20

40

60

80

100 Station 1 Station 2 Station 3 Lake Worth

Figure 46 . Monthly percent Secchi penetration recorded at stations in the Lake Worth study site.60 Discussion This study continued a previous monitoring effort (Arnold, Parker, and Stephenson, 2008) in three estuaries: St. Lucie Estuary, Loxahatchee River, and Lake Worth Lagoon. Four estuaries were discontinued: Tampa Bay, Biscayne Bay, Sebastian River, and Mosquito lagoon. Monitoring oysters in the estuaries of southeast Florida was initiated in Janua ry 2008 and consisted of four major tasks: spatial and size distribution patterns of adult oysters, distri bution and frequency patterns of the oyster diseases Perkinsus marinus (dermo) and Haplosporidium nelsoni (MSX), reproduction and recruitment, and juvenile oyster growth. Oysters in each estuary were subjected to large va riations in salinity. Salinities in SLE were near the optimal range (15-20 ppt) for oyst er survival and recruitment success du ring the first six months of the year, decreased rapidly in July leading to the subseque nt oyster die-off at all sites in the fall and recovered quickly enough to allow successful settlement of the la st recruits of the year. Salinities in LOX were near the optimal range (15-20 ppt) for oyst er survival and recruitment success in the early months of the year, but throughout the rest of the year salinities were er ratic and often either too high resulting in increased predation and disease, or too low for survival. Salinity was highly variable in the LWL, but was generally higher than salinities recorded in the other estuaries, typically higher than the optimal range (15-20 ppt) ranging from a low of 12 ppt to a high of 35 ppt throughout the year (Figure 41). At no point were salinities low enough that they should have negatively impacted growth or recruitment, but high salinities likely impacted Lake Worth oysters by increasing the incidence of predati on and disease infection (dermo). The estuary most heavily impacted by an extreme salinity event was the St. Lucie Estuary. Although there was nearly a complete mortality of adult oysters, and failure of the recruit class during midsummer, the event was less severe than that obser ved during 2005. In 2005, the freshwater event associated with repeated hurricane events continued throughout th e fall recruit season, such that most oyster reefs in SLE were devoid of oysters throughout the winter of 2006, and only showed minimal adult densities in the fall. The result was that an entire year of oyster growth was lost - potentially having serious implications for siltation and subsidence of the reef. After the die-off in fall 2008, the salinity increased sufficiently to allow some settlement and growth of oysters in the fall. We anticipate that there were61 oysters over-wintering on the reef, and that there will be a much more rapid recovery of the reefs in the estuary during 2009. The eastern oyster thrives in salinities from 10-30 ppt but does poorly when salinity falls below 5 ppt for a period of from one to five months (Shumway, 1996). Our adult density measures for the SLE reflect these salinity tolerance limits, particularly duri ng our spring and fall samplings in 2008. Oysters were present at all nine stations in numbers which generally exceeded any seen during the 2005-2007 monitoring. By the fall survey, the numbers of d ead oysters increased and almost mirrored the live densities that had been present in the spring, while only a scattering of live oysters were found on the central estuarine reefs, none in either fork. Both the LOX and LW sites also experienced salinity fluctuations , but none sufficient to cause large mortalities . As a result, both estuar ies had increased density from spring to fall 2008 and oyster density greatly exceeded the average dens ities observed during the 2005-2007 study. The mean shell heights observed during the spring 2008 survey were roughly comparable to those observed in the fall of 2007, with each site showing modest growth over th e winter. In both Loxahatchee and Lake Worth, there were modest declines, reflective of the large recruit class over the summer entering the population. In St. Lucie, the m ean shell height declined dramatically . No large oysters were detected, indicating that virtually all of the observed oysters in the fall survey were recent recruits to the reef. The patterns of disease intensity and prevalence ar e markedly different between the three estuaries studied. Both intensity and preval ence were much higher in LOX an d LWL, where salinities were both higher and more stable, than in St. Lucie, where a protracted period of low salinity occurred. Those patterns match the 2005-2007 study. The most straightforward explanation is that the salinities experienced in much of the SLE are too low for co mpletion of the life history of the Perkinsus parasite. Perkinsus prevalence and intensity in LOX and LWL are compar able with those patterns observed in our 2005-2007 study in Mosquito Lagoon and Tampa Bay, sites anticip ated to be unaffected by Everglades restoration activities and large salinity fluctuations. The severity of dermo in southeast Florida estuaries remains considerably less than it is in most Gulf of Mexico po pulations (Craig et al., 1989). We have not detected MSX ( Haplosporidium nelsoni ) in any sample examined.62 Reproductive development showed some similarities among our study sites, and some notable differences. In general, there were few oysters in what would be considered developmental or fully ripe stages (Stage 1-5) in any estuary. Most oysters collected in Janu ary, February, and December were classified as Stage 10, completely devoid of gametes, or resting. There were some oysters in the resting period as late as March, or as early as November. E ach site also had some Stage 10 oysters present in midsummer. Those may represent young-of-the-year oysters which have not matured, or could represent early spawning oysters which were completely spent by the end of the spring There are also important differences between stud y sites, even within es tuaries. The greatest variation observed was related to the nearly complete mo rtality of oysters throughout the St. Lucie Estuary, making collection of samples for assessment of reproductive development impossible from September through December. No such mortalit y was observed in either LOX or LW L. In the St. Lucie-Central and Loxahatchee-North sites, there is a gradual and regular progression of the oyster population having increasing frequencies of spawning activity (Stages 6-8) beginning in January, peaking in April and May,and declining through August. At the remaining sites, St. Lucie-North, St. Lucie-South, LoxahatcheeSouth, and Lake Worth, there appears to be a less regular pattern, with suggestions of bimodal peak in March/April and again in July/August. Recruitment patterns did not necessarily match the predicted spawning season based on histology. At each St. Lucie site, there were protracted periods with minimal but non-zero recruitment. There was also a large distinct peak of recruitment in July, sugge sting that the large population of oysters in the central estuary supplied larvae throughout the system. In th e Loxahatchee system, ther e were also protracted periods with minimal but non-zero recruitment. However, each fork had two strong peaks in recruitment. Both forks had a strong fall peak (September), but the spring peak occurred much earlier in the south fork (April) than in the nor th fork (June). In Lake Worth Lagoon ma turation occurred late st accompanied by the latest peak in recruitment. Though less regular than other estuaries, the protracted reproductive period in LWL resulted in a large and protracted recruitment event - lasting from June through October. The source of recruits that reestablished the S LE oyster population remains a mystery - similar to the event that occurred in 2005-2006. Although we could find almost no live oysters in SLE during the fall survey, it is probable that a small relict population remained in the estuary. This population may have63 contributed the recruits that were detected in bot h November 2005 and November 2008 in the central portion of SLE and at all sites during mid-2006. It is also possible that those recruits were contributed by oysters living outside of the SLE, but there is no direct evidence to support either alternative. The source of these recruits is of more than academic interest. Whether the larval source was autochthonous or allochthonous, it is possible that continued coastal development will degrade the oyster population of southeast Florida to the point that recruits are no longer available at some sites. This condition does not have to remain for long, as eviden ce from consecutive oyster reef mappi ng efforts in the SLE suggest that at least the smaller reefs can subside in only a few year s. This subsidence will eliminate the essential larval settlement substrate provided by an exposed reef, and once removed from the system it may require decades to rebuild (Mann and Powe ll, 2007) withou t intervention. In both the St. Lucie estuary sites and the Loxahatchee sites physiological condition began the year high, and gradually declined, representative of the transfer of energetic reserves into gamete production. In the Lake Worth Lagoon sites, physiological condition actually climbed gradually throughout most of the spawning season and only began to decline as summer turned to fall. This pattern is suggestive of one where metabolic demands are low enough and food supply high enough that acquired food is sufficient for both growth and reproduction. This result corresponds well with the observation that adult density increased tremendously in 2008 between sp ring and fall. In 2005-2007, most sites, when oysters were present, exhibited the pattern of high cond ition early in the year, with a gradual rate of decline as the reproductive season progressed. In some years the condition would begin to climb again in November and December, after reproduction had fallen off for the year. At one CERP impacted site in one of the three years, LWL in 2006, oy sters exhibited the pattern of highest condition in mid-summer, at the peak of spawning season. This pattern was al so observed in some years in our outlier populations, Tampa Bay and Mosquito Lagoon, suggesting it may be a characteristic of populations in higher salinity habitats. In our 2005-2007 study, the oysters, when present, exhibited a more gradual increase in reproductive development, rather than the rapid progression observed in 2008. Gradual development should lead to a prolonged recruit period whereas rapid development may lead to a shorter recruit period. In general, the population with a broader recruit period would be more resilient to modest departures from64 ideal water quality because the settling spat would have multiple chances to opportunistically settle throughout the estuary. The rates of development an d patterns in recruitment may correlate with certain physical parameters, may have threshold values belo w or above which no development and recruitment occurs, or may have complex relationships with multiple physical parameters. Interpretations of the variations in observed development and recruitment patterns of oysters in these estuaries can only be formulated after multiple years of data have been compiled. Juvenile growth rate was high in both the St. Lucie estuary and the Loxahatchee River. Observed juvenile growth rate was low in LWL. This may be expl ained by the higher levels of spat recruitment that began in June. If new recruits were settling to the grow th array in June, July and August, their smaller sizes would decrease the mean shell height recorded during those months. This is one drawback to setting up a growth study in this manner in that there is no efficient way to mark and follow the same cohort of oysters throughout the experiment. The steady growth rates in the SLE and LOX sites are reflective of our ability to track the growth of a single recruit class of oyster s which settled in relatively discrete peaks. Following recruitment, the juvenile oysters grew very rapidly and at most s ites will exceed 40 mm SH by the following spring. These growth rates are typical of oysters in the southeastern United States and particularly in the Gulf of Mexico, but are more ra pid than those typically reported for more northern populations (Shumway, 1996). Consistent with other bivalves, the more rapid growth of oysters in southern latitudes may be attributed to the longer growin g season rather than to an inherently more rapid growth rate (Jones et al., 1990). This distinction is important, because factors other than temperature also influence growth rate. In particular, oysters do no t grow well at salinities less than 10 ppt (Loosanoff, 1953). Ramifications of growth variation can be si gnificant, as faster growing oysters will more quickly escape the ravages of size-limited predators and also wo uld be expected to reallo cate energy from growth to reproduction at an earlier age. Water quality parameters generally fell within expected ranges with the exception of the low salinity event we have noted above. Temperatures rose and fell almost as expected, with the exception of a slight cooling in April. The water column at each study site remained well oxygenated. pH was usually near or slightly below 8, even during low salinity events. Chlorophyll a concentration was perhaps most variable. At the St. Lucie and Lake Worth Lagoon sites, chlorophyll a generally remained at or below 1065 ug/L. The exceptions to these relatively low and stable concentrations occurred atone station in St. LucieSouth and at both Loxahatchee sites. At LOX, all six stations began the year with relatively high chl a concentrations suggesting that a source of nutrients ha d initiated a plankton bloom, which appeared to have been grazed down by May. Unfortunately, all chl a data was lost in June-August when the chlorophyll probe of our YSI meter was inoperable. Water clarity was generally good, with Secchi depth penetrating to the bottom at most sites. The notable exceptions were at the St. Lucie sites impacted by low salinity. Interestingly, the low visibility seems to have persiste d longer than the lowest salinity readings, but did not initiate a large phytoplankton bloom during the fall despite the probable large input of nutrients to the system and reduced filtering capacity of the benthic community. Comparing parameter values recorded within our st udy estuaries to a range of values typical of Florida estuaries (not affected by CERP activities) provides a pragmatic and real-time view of the consequences of water management practices that aff ect the study estuaries. Our results from the 2008 monitoring effort and the 2005-2007 study indicate that the CERP impacted estuaries may undergo more frequent low-salinity periods than outlier populations. Outlier populations, although not perfect because of physical, geological, and landscape diff erences, nonetheless provide some context within which events in the study estuaries can be evaluated. This is in ag reement with accepted statisti cal practices regarding the analysis and interpretation of event-driven resear ch and monitoring programs (Underwood and Chapman, 2003). This report summarizes oyster population monitoring at six sites within three estuaries in southeast Florida within the South Florida Water Management Dist rict’s domain. Results indicate that the patterns of oyster abundance, health, and popu lation ecology within two (LOX an d LWL) of the study estuaries generally fell within the bounds expected for central and south Florida oyster populations. The impact of anthropogenic events, particularly introductions of fre shwater into the estuaries to manage inland water levels, forced salinity values outside of expected an d suitable ranges in the St. Lucie Estuary. Detailed examination of those events and their consequences c ontinues as we correlate act ual control structure flow rates with the biological and ecological responses of the oysters. In the meantime, it is apparent that such freshwater releases must be carefully considered with respect to their impact on a host of downstream organisms but particularly oysters. 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