Spatial patterns of fish communities along two estuarine gradients in southern Florida

Abstract

In tropical and subtropical estuaries, gradients of primary productivity and salinity are generally invoked to explain patterns in community structure and standing crops of fishes. We documented spatial and temporal patterns in fish community structure and standing crops along salinity and nutrient gradients in two subtropical drainages of Everglades National Park, USA. The Shark River drains into the Gulf of Mexico and experiences diurnal tides carrying relatively nutrient enriched waters, while Taylor River is more hydrologically isolated by the oligohaline Florida Bay and experiences no discernable lunar tides. We hypothesized that the more nutrient enriched system would support higher standing crops of fishes in its mangrove zone. We collected 50 species of fish from January 2000 to April 2004 at six sampling sites spanning fresh to brackish salinities in both the Shark and Taylor River drainages. Contrary to expectations, we observed lower standing crops and density of fishes in the more nutrient rich tidal mangrove forest of the Shark River than in the less nutrient rich mangrove habitats bordering the Taylor River. Tidal mangrove habitats in the Shark River were dominated by salt-tolerant fish and displayed lower species richness than mangrove communities in the Taylor River, which included more freshwater taxa and yielded relatively higher richness. These differences were maintained even after controlling for salinity at the time of sampling. Small-scale topographic relief differs between these two systems, possibly created by tidal action in the Shark River. We propose that this difference in topography limits movement of fishes from upstream marshes into the fringing mangrove forest in the Shark River system, but not the Taylor River system. Understanding the influence of habitat structure, including connectivity, on aquatic communities is important to anticipate effects of construction and operational alternatives associated with restoration of the Everglades ecosystem.

Restoration of the annual flood pulse in Breton Sound, Louisiana, USA: habitat change and nekton community response

“…In comparison with other studies of tidal freshwater marsh during peak seasons (e.g. Rozas & Odum 1987, Castellanos & Rozas 2001, Green et al 2006, we caught about half the number of species and lacked transient species that occupy the marsh surface later during the season. The resident species in our study comprise a guild of omnivores that rapidly colonize the marsh surface once it is inundated, feeding on detritus, epiphytic bacteria, insect larvae, and infauna (Kneib 1997(Kneib , 2000.…”

“…m -2 in flooded intertidal marsh sites. In 2 studies using a 1 m 2 throw trap in the Florida Everglades, Green et al (2006) reported mean densities of 6.6 ind. m -2 at freshwater sites in the Taylor River drainage, and Williams & Trexler (2006) documented mean fish densities of 21.6 ind.…”

Wading bird foraging ecology in a disturbed mangrove estuary in northwest Ecuador : commercial shrimp ponds vs. natural mangrove mudflats

“…Mean standing crop within the natural estuary was similar to maximum values in Florida dwarf mangrove areas («4 g/m2) (Green et al 2006;Lorenz 1999) and less than…”

“…However, biomass was not significantly different between mesohaline and polyhaline environments in the same study region of the Everglades (Lorenz and Serafy 2006), where mangrove habitats are largely non-tidally dominated and oligotrophic relative to the riverine mangrove system, at the study site (Ewel 1998). Seasonal differences in biomass in Everglades mangroves may be more a function of hydrography, hydroperiod, and connectivity rather than salinity per se (Green et al 2006;Faunce et al 2004;Lorenz 1999). Although largely an invertebrate feeder, American flamingo food items increased in abundance during the wet season in the Celestun Lagoon in Yucatan, Mexico (Arrengo and Baldasarre 1999).…”

Examining Gradients in Novelty: Native and Non-native Fish Assemblages in Everglades Canals

“…Differences in native fish abundance between WC and MC canals likely reflect the variation in productivity of the marshes they bisect. WC canals connect to longer hydroperiod marshes almost year-round, which have been shown to have higher fish abundances relative to the shorter hydroperiod marshes that connect to MC canals only during the wet season (Chick et al 2004;Green et al 2006). Additionally, canal connectivity to marsh species pools with different community structure may also have contributed to the observed patterns in this Study.…”