Contribution of green macroalgal mats (Enteromorpha spp.) to seasonal production in an estuary

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Abstract
Benthic green macroalgal mats, composed primarily of Enteromorpha spp., were studied on a mudflat in the Coos Bay estuary (Oregon, USA) during 1981 and 1982. Monthly field collections indicated highest biomass during Aug. of both years. From April to Sept. maximum algal abundance progressed from low to mid-intertidal elevations until storms physically removed algae from the mudflat. Annual production was estimated at 1100 g C m-2 by integration of field measurements of standing crop, light, salinity and temperature; laboratory measurements of C fixation rates under varying conditions of desiccation, light, salinity and algal density; computer generated estimates of tidal emersion and submergence for the Coos Bay estuary. Submerged photosynthesis accounted for an average of 95% of total production despite light attenuation by the water column at the lowest intertidal elevations sampled. Emersed production was restricted by desiccation, light attenuation within the compressed algal mat, inorganic C limitation, and decreasing time of daylight emergence through the growing season. Enteromorpha contributes to the estuarine production chiefly through release of dissolved organic C, burial of algae in sediments, herbivore-enhanced fragmentation and whole-plant loss.
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