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

Abstract

Oyster reefs have been identified as essential fish habitat for resident and transient species. Many organisms found on oyster reefs, including shrimp, crabs, and small fishes, find shelter and food on the reef and in turn provide food for transient species that frequent oyster reefs. The objective of this study was to determine trophic transfer on oyster reefs in a subtropical environment using stable isotope compositions. Water, sediment, particulate organic matter, various crustaceans, fishes, as well as oysters were collected at 2 sites in Estero Bay, Florida, during the wet and dry seasons, and processed for δ 13 C and δ 15 N stable isotope analyses. Differences in freshwater input (salinity) resulted in differences in carbon and nitrogen isotope ratios. Overall, fish and shrimp are secondary consumers, with crabs and oysters as primary consumers, and organic matter sources at the lowest trophic level. Results of the study further demonstrate that reef-resident organisms consume other organisms found on the reef and/or primary producers and detrital organic matter on the reef. Transient fish species come to the reef to feed on the reefresident species. KEY WORDS: Oysters · Crassostrea virginica · Carbon and nitrogen isotopes · Trophic transfer · EstuariesResale or republication not permitted without written consent of the publisher

Effects of oyster harvest activities on Louisiana reef habitat and resident nekton communities

“…This lack of difference in nekton density at reefs with different physical and biological characteristics is similar to that found with other studies of artificial reefs of varying heights (Lenihan et al, 2001), Table 3 Mean stable isotope values (δ 13 C and shell density and vertical relief (Humphries et al, 2011b), and reefs with and without the presence of live oysters (Tolley and Volety, 2005;Summerhayes et al, 2009). Although ecological theory holds that structurally complex habitats are expected to sustain higher densities and more diverse communities than structurally simple ones, defining structural complexity has never been straightforward (Beck, 1998;Bartholomew et al, 2000), and it is not clear whether the harvested and nonharvested sites represented different levels of complexity or just differences in habitat characteristics. No consensus exists as to how to define oyster reef complexity; in some experiments oyster or shell density, vertical relief, or mixtures of unaggregated shells (simple) versus clusters (complex) were used, making it difficult to determine when complexity had actually changed (Grabowski and Powers, 2004;Grabowski et al, 2008;Humphries et al, 2011a).…”

“…Benthic microalgae could also contribute to the food webs of oyster reef communities; however, in San Antonio Bay, Texas (also a shallow, turbid estuary), the microphytobenthos contributed less than 2% of the primary production found in the water column (MacIntyre and Cullen, 1996). Benthic macroalgae, seagrass epiphytes, and upstream terrestrial plant matter can also contribute to the basal food source (Abeels et al, 2012), but these sources were not observed within the studied reef areas.…”

“…Although deriving a TEF specific to these systems may result in different estimates of trophic positions, the trends observed would not change. Differences in trophic position of resident species have also been found between reefs and mud-bottom sites (Quan et al, 2012) and between reefs that were experiencing different riverine exposures (Abeels et al, 2012).…”

“…At each of the 4 sites, 3 sample stations, measuring 10 m×10 m, were established on reef habitat located more than 100 m from the marsh edge and in the centers of reef areas to remove confounding effects of adjacent habitats and reef edge (Fig. 2;Acosta and Robertson, 2002;Grabowski et al, 2005). At each sample station, reef structure, water quality, and resident nekton communities were sampled according to protocols listed below.…”

Diurnal Fluctuations in Acidification and Hypoxia Reduce Growth and Survival of Larval and Juvenile Bay Scallops (Argopecten irradians) and Hard Clams (Mercenaria mercenaria)

“…habitat (Tolley and Volety, 2005;Abeels et al, 2012), decreasing coastal erosion (Meyer et al, 1997;Coen et al, 2007), and improve the surrounding water quality through the removal of suspended particulates (Officer et al, 1982;Wall et al, 2008). Finally, shellfish also provide a significant source of income and economic stimulus within coastal communities (Shumway et al, 2003;Ekstrom et al, 2015).…”