Sand Bottom Microalgal Production and Benthic Nutrient Fluxes on the Northeastern Gulf of Mexico Nearshore Shelf

Benthic microalgal production on the continental shelves may be an important contributor to the overall productivity of offshore eco - systems. We used light and dark benthic chambers to measure in situ production, respiration, and benthic nutrient flux on the nearshore quartzite sands of the northeast Gulf of Mexico shelf. Net exchange of O 2 , NH 4 + , NO 3 — + NO 2 — , PO 4 /hr. Benthic respiration was 24.8 ± 0.7, 30.8 ± 1.4, and 11.3 ± 0.3 mg C/m 2 /hr, respectively. Benthic gross production was thus 42.5 ± 5.2, 40.3 ± 1.2, and 20.3 ± 1.7 mg C/m 2 /hr, respectively. Benthic nutrient fluxes were highly variable and generally low. Sediment uptake was observed for NH 4 + and PO 4 —3 throughout the study. NO 3 — + NO 2 — and SiO 2 uptake was observed in 2004 with sediment release seen in 2005.