Trophic heterogeneity in salt marshes of the northern Gulf of Mexico

Abstract

Predator-prey interactions in salt-marsh ecosystems are driven primarily by interactions among tidal dynamics, local physiography, and macrophyte density. Distinct seaward-to-landward predation gradients have been described for the continuous and expansive meadows of Spartina alterniflora on the Atlantic coast of the United States. In the northern Gulf of Mexico, Juncus roemerianus dominates and Spartina is generally limited to fringing bands or disjunct patches in low-lying areas. It is not known whether predation regimes vary consistently among subhabitats in these disjunct marshes. We investigated whether small-scale variations in topography and habitat structure produce persistently distinguishable predation regimes among marsh patches in coastal Alabama. Each of our study sites was representative of the principal subhabitats found within continuous Spartina meadows: vegetation bordering open water, tidal creeks within the marsh, and interior subhabitat. We assessed a strong trophic interaction in these subhabitats: predation pressure exerted by the blue crab Callinectes sapidus on the periwinkle Littoraria irrorata. The distribution of sublethal repairs in Littoraria shells demonstrated that attacks by Callinectes were randomly inflicted, irrespective of attack frequency. The occurrence of sublethal shell repair was positively related to the frequency of predatory attacks on experimentally tethered snails, the abundance of crabs, and the degree of antipredatory architectural defense in the snail shells. Among-site differences in shell repair and architectural defense were related to topography and habitat structure, and these differences persisted over multiple seasons and years. Physical variations thus maintain strong, persistent predation regimes among subhabitats in disjunct Spartina marshes.

Effect of durophagy on drilling predation: a case study of Cenozoic molluscs from North America

“…Although it must be recognised that repair scars represent failed attacks and are thus analogous to incomplete rather than complete drill holes (Vermeij 1987;Allmon et al 1990;Leighton 2001Leighton , 2002Harper 2006), they can be used as proxy for predatory activity. This is supported by a recent study with live blue crabs and periwinkles by Moody and Aronson (2007) which demonstrated that the occurrence of sublethal shell repair in Littorina was positively correlated with the frequency of predatory attacks and the abundance of crabs.…”

Patterns of unsuccessful shell‐crushing predation along a tidal gradient in two geographically separated salt marshes

“…1982; Warren 1985; Schindler et al. 1994; Lewis & Eby 2002; Silliman & Bertness 2002; Moody & Aronson 2007). Blue crabs invade the marsh with flood tides and prey on Littoraria that migrate upward from the sediment surface along Spartina stems during flood tides, typically returning to open‐water areas and tidal creeks on ebbing tides.…”

Trophic Relationships of a Marsh Bird Differ Between Gulf Coast Estuaries

“…Tidal estuaries are unique environments where a distinct array of physical and chemical properties can vary over relatively short time periods (Dardeu et al 1992) and small distances (Mannino and Montagna 1997). Predicting the response of estuarine ecosystems to changing environmental conditions is therefore challenging, as it necessitates understanding interactions among several trophic levels and multiple nutrient sources (marine, freshwater, and terrestrial) (Day et al 1993;Moody and Aronson 2007). Because birds are relatively well studied, they have been used to measure ecological conditions and evaluate the impacts of environmental change within tidal estuaries (Shriver et al 2004;DeLuca et al 2008).…”