|Microphytobenthic productivity and biomass in sublittoral sediments of a stratified bay, southeastern Kattegat|Sundbâck, K.; Jönsson, B. (1988). Microphytobenthic productivity and biomass in sublittoral sediments of a stratified bay, southeastern Kattegat. J. Exp. Mar. Biol. Ecol. 122(1): 63-81. hdl.handle.net/10.1016/0022-0981(88)90212-2
In: Journal of Experimental Marine Biology and Ecology. Elsevier: Tokyo; Oxford; New York; Lausanne; Shannon; Amsterdam. ISSN 0022-0981, more
Chlorophyll a; Depth gradient; Light; Microphytobenthos; Primary productivity; Sediment
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The sublittoral sediment-associated microflora (microphytobenthos) of Laholm Bay, southeastern Kattegat, was investigated for a period of 3 yr by taking monthly sediment samples at depths of 2–20 m. The aims were to quantify the importance of the microphytobenthos in the primary production of a coastal area subjected to eutrophication and to assess the most important limiting factors. There was a considerable potential microphytobenthic production in Laholm Bay, but the actual in situ production was limited by light at a depth of > 5 m. Productivity and biomass did not, however, decrease linearly with depth and some of the highest values were measured at ˜ 15 m, where only a few percent of the surface light penetrated. This pattern of distribution along the depth gradient is interpreted as a result of the interaction of light and nutrient conditions, sediment type, and the degree of exposure to water movements. The range of photon-flux densities needed to saturate photosynthesis I (Ik) was large (30–320 µE · m-2 · s-1) and varied with season and depth. The microbenthic primary production occurred mainly during the period May–September and varied between < 1 and 20 gC · m-2 · yr-1 depending on depth and sediment type. Viable sedimented phytoplankton cells occasionally contributed to benthic primary production. The annual microphytobenthic production for the whole bay has been estimated as 5–10 gC · m-2, which corresponds to 5–10% of the annual phytoplankton production. Based on this study and previous laboratory experiments, it is suggested that in an early stage of eutrophication, before an extensive increase in turbidity caused by phytoplankton, the microphytobenthos will benefit from increased nutrient levels. Microphytobenthic production will then have a positive effect on the ecosystem by improving oxygen conditions at the sediment-water interface and by decreasing the release of inorganic nutrients, in particular ammonium and phosphate, from the sediment.