Benthic algae control sediment—water column fluxes of organic and inorganic nitrogen compounds in a temperate lagoon

摘要: Coastal lagoons are a common land-margin feature worldwide and function as an important filter for nutrients entering from the watershed. The shallow nature of leads to dominance by benthic autotrophs, which can regulate benthic‐pelagic coupling. Here we demonstrate that both microalgae macroalgae in controlling dissolved inorganic well organic nitrogen (DIN DON) fluxes between sediments water column. Fluxes (NH , NO DON, urea, free combined amino acids [DFAA, 12 43 DCAA]) O2 were measured October 1998 through August 1999 sediment cores collected Hog Island Bay, Virginia. Cores four sites representing range environmental conditions across this lagoon: muddy, high-nutrient sandy, low-nutrient dominated microalgae, mid-lagoon site with fine sands covered dense macroalgal mats. Sediment‐water column DON highly variable comparable magnitude DIN fluxes; individual compounds (urea, DFAA, DCAA) often proceeded simultaneously different directions. Where metabolism was net autotrophic because microalgal activity, TDN (total nitrogen) fluxes, mostly comprised DIN, directed into sediments. Heterotrophic sediments, including those underlying mats, source TDN, DIN. Macroalgae intercepted sediment‐water accounted 27‐75% calculated N demand. uptake satisfying demand seasonally where concentrations low. Up 22% total released DCAA. Overall, assimilated, transformed, rereleased on short (minutes‐hours) long (months) time scales. Microalgae clearly coupling thereby influence transformations retention moving land‐sea interface.