Influence of Freshwater Inflow on the Distribution and Community Structure of Decapod Zooplankton in Estero Bay.

1. Influence of Freshwater Inflow on the Distribution and Community Structure of Decapod Zooplankton in Estero Bay. Jennifer Nelson1, James Evans1, Bethany Bachelor1, Scott Burghart2, and S Gregory Tolley1

2. Study objectives Study Location Methods / Study Design Distribution of decapod zooplankton Community structure of decapod zooplankton Potential management implications Presentation Overview Distribution of the decapods both spatially and temporally. Distribution of the decapods both spatially and temporally.

3. Describe the seasonal and spatial patterns of decapod crustacean zooplankton densities within Estero Bay. Describe the relationships of those patterns to freshwater inflows from the Bay�s tributaries Investigate the influence of freshwater inflow on the structure of the decapod zooplankton community Research Objectives Distribution and community structure within the context of freshwater inflow and salinity as a proxy for inflow Distribution and community structure within the context of freshwater inflow and salinity as a proxy for inflow

4. Estero Bay

5. Study Design / Methods Monthly plankton tows 16 Fixed Stations January 2005 thru December 2006 0.5m diameter plankton net w/ flowmeter 500 um mesh net Net towed on flood tides for 5 minutes at 1.0 to 1.5 m/s 3-step tow to capture entire water column Zooplankton captured are washed into jar and preserved Water quality parameters recorded: Temp, Salinity, DO, Sp.Conductance (YSI) Important to note that sampling was conducted during the day. Sampling at night may yield more shrimps and mysids, but the three-step tow was designed to capture the entire water column including the epibenthic zone just above the bottom where some of those species spend the daytime. Also, Estero Bay is very shallow and usually well-mixed. Important to note that sampling was conducted during the day. Sampling at night may yield more shrimps and mysids, but the three-step tow was designed to capture the entire water column including the epibenthic zone just above the bottom where some of those species spend the daytime. Also, Estero Bay is very shallow and usually well-mixed.

6. Study Design / Methods cont. Samples identified at University of South Florida in Ernst Peebles� lab Samples identified to species where possible Samples enumerated and stages identified Freshwater inflow: USGS gauge station data converted to average flows (cfs) Salinity used as proxy for freshwater inflow Contour plots constructed using species density data, wq data, and SURFER Spatio-temporal distributions Multivariate analysis performed using PRIMER Community structure Primary Taxonomist: Co-author Scott Burghart (Ralf Kitzmiller also assisted in the taxonomic ID) SURFER � A contouring and 3D surface mapping program PRIMER � Plymouth Routines in Multivariate Ecological Research Primary Taxonomist: Co-author Scott Burghart (Ralf Kitzmiller also assisted in the taxonomic ID) SURFER � A contouring and 3D surface mapping program PRIMER � Plymouth Routines in Multivariate Ecological Research

7. Decapods Most varied Order of Crustaceans Crabs, Shrips, Lobsters Most decapods have a planktonic larval phase (meroplankton) Generally mesozooplankton in size Decapods comprised 87.5% of the total catch in this study 41 species, 105 taxa Generally mesozooplankton in size: 0.2 � 20mm Portunus � Same family as Callinectes (Blue Crab) Petrolisthes armatus � Green porcelain crab Palaemonetes vulgaris � A species of grass shrimp (We had a lot of Palaemonetes spp. Mysis larvae and postlarvae in our samples as well as P. vulgaris and P. pugio)Generally mesozooplankton in size: 0.2 � 20mm Portunus � Same family as Callinectes (Blue Crab) Petrolisthes armatus � Green porcelain crab Palaemonetes vulgaris � A species of grass shrimp (We had a lot of Palaemonetes spp. Mysis larvae and postlarvae in our samples as well as P. vulgaris and P. pugio)

8. Seasonal Abundance Patterns Seasonal bimodal peaks in organism density; Habitat Use: Dry season vs. Wet Season (Organism density reduced at onset of wet season) One-month lag between years Seasonal bimodal peaks in organism density; Habitat Use: Dry season vs. Wet Season (Organism density reduced at onset of wet season) One-month lag between years

9. Seasonal Abundance Patterns & Freshwater Inflow Total inflow higher in 2005 by 42% Inter-annual lag in onset of wet season � reflected in abundance patterns Inflows influence decapod abundances differently depending upon taxa Inflow data not available for the entire study period for Hendry & Mullock Creeks (Terminated Sep 2005). Index used as a proxy for total inflow. Advection and behavioral factors at workInflow data not available for the entire study period for Hendry & Mullock Creeks (Terminated Sep 2005). Index used as a proxy for total inflow. Advection and behavioral factors at work

10. Spatial Abundance Patterns Peak zooplankton densities in dry season (2006) due to multiple species Dominated by Rhithropanopeus harrisii during wet season (2005 & 2006) The sampling stations located in or near the two highest freshwater inflow tidal tributaries (i.e. Imperial River and Mullock Creek) were characterized as seasonal low salinity zone (LSZ) habitats. These LSZ habitats were defined by Arthur & Ball (1979) and Lehman (2000) as areas with 0.6 to 4 psu, and can be zones within which suspended particles, including phytoplankton, become trapped. Within the LSZ habitats of Hendry and Mullock Creeks, Rhithropanopeus harrisii was the dominant species (out of entire zooplankton catch) during the wet months, while both Sesarma reticulatum and Rhithropanopeus harrisii were each dominant species during some of the wet months at the Imperial River site. In addition, juveniles and adults of these species are common on the oyster reefs located at the mouths of Hendry and Mullock Creeks within the LSZ habitat (Tolley et al., 2006). The sampling stations located in or near the two highest freshwater inflow tidal tributaries (i.e. Imperial River and Mullock Creek) were characterized as seasonal low salinity zone (LSZ) habitats. These LSZ habitats were defined by Arthur & Ball (1979) and Lehman (2000) as areas with 0.6 to 4 psu, and can be zones within which suspended particles, including phytoplankton, become trapped. Within the LSZ habitats of Hendry and Mullock Creeks, Rhithropanopeus harrisii was the dominant species (out of entire zooplankton catch) during the wet months, while both Sesarma reticulatum and Rhithropanopeus harrisii were each dominant species during some of the wet months at the Imperial River site. In addition, juveniles and adults of these species are common on the oyster reefs located at the mouths of Hendry and Mullock Creeks within the LSZ habitat (Tolley et al., 2006).

12. Spatio-temporal distributions Eurypanopeus depressus (flatback mud crab) Zoea density Upstream movement is a typical response of fishes and invertebrates to reduced inflows seen in riverine estuaries on Florida�s west coast (Peebles 2002b, MacDonald et al. 2005, Greenwood et al. 2006). Zoea density Upstream movement is a typical response of fishes and invertebrates to reduced inflows seen in riverine estuaries on Florida�s west coast (Peebles 2002b, MacDonald et al. 2005, Greenwood et al. 2006).

13. Mysis LarvaeMysis Larvae

14. Zoea densityZoea density

15. Zoea densityZoea density

16. Decapods and Salinity Decapod distributions related to physiological salinity tolerances of each taxa Decapod larvae rely on osmoregulation and behavioral responses to handle variable salinity conditions Advection is also a factor in distributions Species-specific variability in distributions of decapod larvae is related to the physiological salinity tolerances of each species, and the highly variable salinity conditions of estuarine environments. Decapod larvae rely on both active internal osmoregulation as well as behavioral responses to unfavorable salinity conditions (Anger, 2001; Capaldo, 1993) to deal with that variability. Density-weighted mean salinity of capture (organism central tendency) was calculated for a number of the common decapod taxa, the majority of which exhibited distributions that centered at salinities of ? 30 (Table 2). In contrast, Rhithropanopeus harrisii and Sesarma reticulatum both had much lower density-weighted mean salinities of capture, 12 and 26 psu, respectively. Density-weighted salinity of capture (Su), or the central tendency of organism distribution, was calculated as SU = ?(S*U)/ ?U, where U is organism density (no. m-3) and S is mean water-column salinity during plankton net deployment. Species-specific variability in distributions of decapod larvae is related to the physiological salinity tolerances of each species, and the highly variable salinity conditions of estuarine environments. Decapod larvae rely on both active internal osmoregulation as well as behavioral responses to unfavorable salinity conditions (Anger, 2001; Capaldo, 1993) to deal with that variability. Density-weighted mean salinity of capture (organism central tendency) was calculated for a number of the common decapod taxa, the majority of which exhibited distributions that centered at salinities of ? 30 (Table 2). In contrast, Rhithropanopeus harrisii and Sesarma reticulatum both had much lower density-weighted mean salinities of capture, 12 and 26 psu, respectively. Density-weighted salinity of capture (Su), or the central tendency of organism distribution, was calculated as SU = ?(S*U)/ ?U, where U is organism density (no. m-3) and S is mean water-column salinity during plankton net deployment.

17. Decapod community Structure

18. Decapod community Structure

19. Decapod community Structure Cluster analysis of decapod larval abundances for both the wet and dry seasons (Figures 9 and 10) indicated distinct differences in community structure between the low salinity stations (1, 2 and 9, 10) and all other stations. The northern stations 1 and 2 (Hendry and Mullock Creeks) grouped together as a distinct assemblage, as well as the southern stations 9 and 10 (Imperial River and Fish Trap Bay). During the wet season, station 3 was grouped with stations 1 and 2 as distinct from all other stations, possibly reflecting the seasonal influence of freshwater inflow from Mullock Creek on its community structure. Multidimensional scaling (MDS) plots (Figures 11 and 12) also demonstrated these distinctions, with stations 1 and 2 being grouped together, as well as stations 9 and 10. Both of these groupings were clearly separated in ordination space from all other stations in both the wet and dry season although the wet season shows much greater distinction and has a lower stress level than the dry season plot (.08 vs .15). Station 3 is located between the station 1 and 2 grouping and the remainder of the stations, again suggesting the wet season influence of inflows on its community structure. The station numbers are overlayed with salinity bubbles, making it clear that the lower salinity stations are those that are dissimilar to the rest of the stations in community structure. Cluster analysis of decapod larval abundances for both the wet and dry seasons (Figures 9 and 10) indicated distinct differences in community structure between the low salinity stations (1, 2 and 9, 10) and all other stations. The northern stations 1 and 2 (Hendry and Mullock Creeks) grouped together as a distinct assemblage, as well as the southern stations 9 and 10 (Imperial River and Fish Trap Bay). During the wet season, station 3 was grouped with stations 1 and 2 as distinct from all other stations, possibly reflecting the seasonal influence of freshwater inflow from Mullock Creek on its community structure. Multidimensional scaling (MDS) plots (Figures 11 and 12) also demonstrated these distinctions, with stations 1 and 2 being grouped together, as well as stations 9 and 10. Both of these groupings were clearly separated in ordination space from all other stations in both the wet and dry season although the wet season shows much greater distinction and has a lower stress level than the dry season plot (.08 vs .15). Station 3 is located between the station 1 and 2 grouping and the remainder of the stations, again suggesting the wet season influence of inflows on its community structure. The station numbers are overlayed with salinity bubbles, making it clear that the lower salinity stations are those that are dissimilar to the rest of the stations in community structure.

20. Decapod community Structure Higher StressHigher Stress

21. Conclusions The influence of freshwater inflow on decapod larval distributions and community structure in Estero Bay appears to be strong The strongest influence appears to be in areas of highest inflows (northern and southern tributary stations), which are also the areas of widest range of salinity conditions

22. Management Implications Identification of indicator species Species sensitive to high or low flows Regressions established describing abundance relationships with inflow Development of potential management tool Using specific species regressions indexed to percentile of inflow Indicator species utilized as performance measures after MFL or restoration implementation A more robust understanding of various biological communities (oysters, seagrasses, zooplankton) within an entire system (i.e. Estero Bay) and how those communities respond to different conditions, creates the capacity for better system management Framing indicators (i.e. indicator of high flow acceptable conditions and indicator of acceptable low flow conditions Framing indicators (i.e. indicator of high flow acceptable conditions and indicator of acceptable low flow conditions

23. Acknowledgements USF: Ernst Peebles, Scott Burghart, Ralf Kitzmiller FGCU Coastal Watershed Institute: Greg Tolley, Erin Dykes, Lesli Haynes, Amanda Booth, FGCU Marine Lab Interns USGS: Mike Byrne, Ed Patino, Carolyn Price SFWMD: Peter Doering, Bob Chamberlain, Kathy Haunert,Tomma Barnes