title: Effects of macroalgal blooms on carbon and nitrogen biogeochemical cycling in photoautotrophic sediments: an experimental mesocosm.
abstract: The effects of floating macroalgae (250 g DW m(-2)) on photoautotrophic microbenthos were studied in a flow-through mesocosm with a parallel mesocosm without macroalgae serving as Control. Vertical microprofiles of O(2) at the sediment-water interface showed a immediate and complete suppression of photosynthetic activity of microphytobenthos (MPB) under the macroalgal canopy, resulting in a shift of benthic metabolism from autotrophic to heterotrophic. MPB abundance and chlorophyll a content decreased and a change from a diatom-dominated to cyanobacteria-dominated community was observed. Inorganic nitrogen nutrients' concentrations increased in the porewater as a result of the inhibition of MPB nutrient demand, leading to an increase in net ammonification and anaerobic NO(x)(-) consumption rates. No organic matter transfer from macroalgae to the sediment was detected, resulting in a net consumption of the carbon and nitrogen stored in the sediment. In consequence, sediment was progressively impoverished in nitrogen, reducing sediment nutrient regeneration.
authors.affiliation: Dpto. Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Pol. Río San Pedro s/n, 11510 - Puerto Real, Cádiz, Spain. emilio.garcia@uca.es
authors.forename: E
authors.initials: E
authors.lastname: García-Robledo
authors.forename: A
authors.initials: A
authors.lastname: Corzo
mesh_terms: D044822:Biodiversity; D002244:Carbon / Q000032:analysis; D057486:Carbon Cycle; D002734:Chlorophyll / Q000032:analysis; D000077194:Chlorophyll A; D017753:Ecosystem; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis; D058458:Nitrogen Cycle; D010100:Oxygen / Q000032:analysis; D012624:Seaweed / Q000145:classification / Q000254:growth & development*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D002734:Chlorophyll; D002244:Carbon; D009584:Nitrogen; D010100:Oxygen; D000077194:Chlorophyll A