AB - Vol. 15 No. 1 - Feature article

Herbivorous fish grazing within the seagrass canopy. Photo: John Carroll

Peterson BJ, Stubler AD, Wall CC, Gobler CJ

 

Nitrogen-rich groundwater intrusion affects ­productivity, but not herbivory, of the tropical ­seagrass Thalassia testudinum

 

This study demonstrates that benthic primary producers utilize terrestrially derived nitrogen delivered through submarine groundwater discharge. Meadows of Thalassia testudinum located within a groundwater discharge zone in Discovery Bay, Jamaica, had significantly more above-ground biomass, higher rates of productivity, and leaves enriched in nitrogen. While recent studies have shown that herbivores preferentially graze seagrass blades with elevated tissue nitrogen, reciprocal transplant experiments revealed that herbivores avoided the nitrogen-enriched leaves to preferentially consume leaves that were stoichiometrically enriched in phosphorus. This suggests that herbivore grazing was influenced more by the ecological stoichiometry of these plants than the absolute nitrogen content in this phosphorus-limited, tropical marine system.

 

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