Impacts of salinity and freshwater inflow on oyster-reef communities in Southwest Florida

Abstract

When assessing oyster-reef habitat in estuaries it is important to understand the influence of salinity on the spatial and temporal variability of associated organisms. How comparable is community structure among stations located at different points along the salinity gradients of estuaries or among tidal tributaries that experience different levels of freshwater inflow? Do assemblages vary seasonally in response to changing salinity and freshwater inflow? To address these questions, multivariate techniques were employed to analyze decapod crustacean and fish abundance data. Organisms were collected at three reefs along the salinity gradient of three estuaries: the Caloosahatchee River and estuary, Estero River and Bay, and Faka Union Canal and Bay. Additional collections were made from reefs located near the mouths of Estero Bay's five tidal tributaries. Samples were dominated by the decapods Eurypanopeus depressus and Petrolisthes armatus. Commonly occurring species included the decapods Panopeus obesus, Alpheus heterochaelis and Rhithropanopeus harrisii and the fishes Gobiosoma robustum, Lophogobius cyprinoides and Gobiesox strumosus. Analysis of similarities suggested differences among stations located along the salinity gradients of all three estuaries. Community structure also varied among stations located near the mouths of the tidal tributaries of Estero Bay. Multidimensional scaling identified community structure present at upper stations as distinct from that downstream and at high-flow tributaries as distinct from that near low-flow tributaries. Upper stations and stations near high-flow tributaries were typified by E. depressus and gobiid fishes. Downstream stations and stations near low-flow tributaries were typified by E. depressus and P. armatus. Percent dissimilarity was greatest when upper and lower stations were compared along the salinity gradient or when low salinity and high-salinity sites were compared among tributaries. Within-station sample variability tended to be higher upstream or in association with high-flow tributaries.

Too Much Freshwater, Not Enough, or Just Right? Long-Term Trawl Monitoring Demonstrates the Impact of Canals that Altered Freshwater Flow to Three Bays in SW Florida

“…This occurred despite square-root transforming the abundance data in our analysis, which downplays the differences among highly abundant species and enhances the influence of less common ones. This finding is a robust confirmation of earlier, shortterm assessments of the fish community in the area that found broad overlap in dominant species in these and other nearby estuaries along the Southwest Florida coast (Carter et al 1973;Colby et al 1985;Browder et al 1986;Sheridan 1992;Shirley et al 2004;Idelberger and Greenwood 2005;Tolley et al 2006). Not only was a similar set of species responsible for seasonal differences in all three bays studied here, but more importantly, their relative abundance tracked with season in similar ways despite large differences in hydrology.…”

Too Much Freshwater, Not Enough, or Just Right? Long-Term Trawl Monitoring Demonstrates the Impact of Canals that Altered Freshwater Flow to Three Bays in SW Florida

“…This occurred despite square-root transforming the abundance data in our analysis, which downplays the differences among highly abundant species and enhances the influence of less common ones. This finding is a robust confirmation of earlier, shortterm assessments of the fish community in the area that found broad overlap in dominant species in these and other nearby estuaries along the Southwest Florida coast (Carter et al 1973;Colby et al 1985;Browder et al 1986;Sheridan 1992;Shirley et al 2004;Idelberger and Greenwood 2005;Tolley et al 2006). Not only was a similar set of species responsible for seasonal differences in all three bays studied here, but more importantly, their relative abundance tracked with season in similar ways despite large differences in hydrology.…”

Trophic transfer and habitat use of oyster Crassostrea virginica reefs in southwest Florida, identified by stable isotope analysis

“…Eurypanopeus depressus and Petrolisthes armatus were the most abundant species found on oyster reefs in Estero Bay, both in this study and in previous work by Tolley et al ( , 2006). In the current study, E. depressus was more abundant at the Hendry/Mullock Creeks site and P. armatus was more abundant at the Estero River site (Table 1).…”

Oyster reef connectivity : ecological benefits and associated vulnerabilities

“…This example highlights the impact of habitat connectivity on the effect of reef connectivity: reduced freshwater input from upstream amplified a negative cost of reef connectivity downstream. Changes in salinity regime within the estuary also change larval transport and distribution of fish and crustaceans associated with reef habitat (Tolley et al 2006). Thus, management approaches should consider connectivity within the reef system as well as connectivity within the watershed.…”

Too Much Freshwater, Not Enough, or Just Right? Long-Term Trawl Monitoring Demonstrates the Impact of Canals that Altered Freshwater Flow to Three Bays in SW Florida

“…This occurred despite square-root transforming the abundance data in our analysis, which downplays the differences among highly abundant species and enhances the influence of less common ones. This finding is a robust confirmation of earlier, shortterm assessments of the fish community in the area that found broad overlap in dominant species in these and other nearby estuaries along the Southwest Florida coast (Carter et al 1973;Colby et al 1985;Browder et al 1986;Sheridan 1992;Shirley et al 2004;Idelberger and Greenwood 2005;Tolley et al 2006). Not only was a similar set of species responsible for seasonal differences in all three bays studied here, but more importantly, their relative abundance tracked with season in similar ways despite large differences in hydrology.…”

Trophic transfer and habitat use of oyster Crassostrea virginica reefs in southwest Florida, identified by stable isotope analysis

“…Eurypanopeus depressus and Petrolisthes armatus were the most abundant species found on oyster reefs in Estero Bay, both in this study and in previous work by Tolley et al ( , 2006). In the current study, E. depressus was more abundant at the Hendry/Mullock Creeks site and P. armatus was more abundant at the Estero River site (Table 1).…”

Oyster reef connectivity : ecological benefits and associated vulnerabilities

“…This example highlights the impact of habitat connectivity on the effect of reef connectivity: reduced freshwater input from upstream amplified a negative cost of reef connectivity downstream. Changes in salinity regime within the estuary also change larval transport and distribution of fish and crustaceans associated with reef habitat (Tolley et al 2006). Thus, management approaches should consider connectivity within the reef system as well as connectivity within the watershed.…”

Too Much Freshwater, Not Enough, or Just Right? Long-Term Trawl Monitoring Demonstrates the Impact of Canals that Altered Freshwater Flow to Three Bays in SW Florida

“…This occurred despite square-root transforming the abundance data in our analysis, which downplays the differences among highly abundant species and enhances the influence of less common ones. This finding is a robust confirmation of earlier, shortterm assessments of the fish community in the area that found broad overlap in dominant species in these and other nearby estuaries along the Southwest Florida coast (Carter et al 1973;Colby et al 1985;Browder et al 1986;Sheridan 1992;Shirley et al 2004;Idelberger and Greenwood 2005;Tolley et al 2006). Not only was a similar set of species responsible for seasonal differences in all three bays studied here, but more importantly, their relative abundance tracked with season in similar ways despite large differences in hydrology.…”

Trophic transfer and habitat use of oyster Crassostrea virginica reefs in southwest Florida, identified by stable isotope analysis

“…Eurypanopeus depressus and Petrolisthes armatus were the most abundant species found on oyster reefs in Estero Bay, both in this study and in previous work by Tolley et al ( , 2006). In the current study, E. depressus was more abundant at the Hendry/Mullock Creeks site and P. armatus was more abundant at the Estero River site (Table 1).…”

Oyster reef connectivity : ecological benefits and associated vulnerabilities

“…This example highlights the impact of habitat connectivity on the effect of reef connectivity: reduced freshwater input from upstream amplified a negative cost of reef connectivity downstream. Changes in salinity regime within the estuary also change larval transport and distribution of fish and crustaceans associated with reef habitat (Tolley et al 2006). Thus, management approaches should consider connectivity within the reef system as well as connectivity within the watershed.…”