Search

Examines the porewater profiles of inorganic and organic nutrients in seagrass-vegetated sediments in a shallow bay in Bermuda Islands. Concentration of dissolved and inorganic nutrient; Use of stoichiometric nutrient regeneration model; Depletion of sediment porewaters.

Abstract: Herbivory has an important influence on seagrass abundance and distribution, yet there is limited understanding of grazing behavior in communities at geographic margins of species ranges. We used 24-h seagrass-tethering experiments to measure the effect of foliar nitrogen content and time of year on bucktooth parrotfish Sparisoma radians herbivory in high-latitude Thalassia testudinum meadows of Bermuda. Parrotfish preferentially grazed nitrogen-enriched tethered shoots especially at offshore sites that had relatively low background nutrient levels. Selective feeding was pronounced during periods of high grazing intensity. We found strong seasonal patterns, likely because Bermuda is at the northerly limit of these two species. Herbivory rates peaked in late summer when the mean leaf removal rate by S. radians was 3.38±1.11cmshoot−1 day−1, which exceeded the daily seagrass growth rate by 10-fold. Seagrass meadows are in decline in this region and we suggest that seasonal episodes of clustered, intensive grazing could make these habitats more vulnerable to other environmental or human-induced stresses, such as storms and runoff of sediment and nutrients. [Copyright &y& Elsevier]