Benthic community metabolism in a coastal lagoon ecosystem

Abstract

Measurements of benthic oxygen production and consumption at 3 stations over a n annual cycle in a shallow (mean depth = 0.7 m) coastal lagoon on the Rhode Island (USA) coast provide evidence that shallow benthic communities may consume more organic matter than can b e provided by impressive rates of in situ epifloral production. While sandy sediment areas in Potter Pond lagoon showed a net daytime production of about 140 g C m-* y r l , the more extensive areas of fine-grained sediment did not show any significant amount of net benthic daytime production annually. Moreover when nighttime respiratory costs were included, the lagoon benthos a s a whole showed a net organic consumption of 30 g C m-2 y r l in spite of a net annual daytime production rate of 50 g C mS y r l . Rates of in situ oxygen uptake by fine-grained lagoon sediments in the dark were not separable from those of similar sediments in much deeper (mean = 8.6 m) Narragansett Bay. For the lagoon a s a whole, the benthos consumed about 40 to 5 0 % of the combined primary production by phytoplankton, macrophytes and benthic epiflora. This partitioning is slmilar to that found in deeper, plankton-based systems with completely heterotrophic bottom communities.