Energy flow through the SE Kattegat: a comparative examination of the eutrophication of a coastal marine ecosystem
Pearson, T.H.; Rosenberg, R. (1992). Energy flow through the SE Kattegat: a comparative examination of the eutrophication of a coastal marine ecosystem. Neth. J. Sea Res. 28(4): 317-334
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, more
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| Abstract |
Energy flow through the major compartments of the ecosystem of the south-east Kattegat has been assessed based on observations made between 1985-1989. In this increasingly eutrophic semi-estuarine coastal area, energy inputs are dominated by autochthonous production during the spring and autumn bloom periods (>90%), and by allochthonous fluvial sources during the winter (>50%). An unbalanced annual carbon budget is presented, which demonstrates the predominance of infaunal benthic suspension feeders in the shallow areas (above 13 m), where their demand alone is 2.4 times the calculated carbon supply to the sediment. Benthic demand does not diminish below 13 m, but the proportion utilized by macrofaunal deposit feeders and meiofauna increases with lower suspension feeder demand, emphasizing the close coupling between pelagos and benthos at all depths in this system. Excess benthic demand over planktonic production is assumed to be met by lateral imports across the system boundaries. Intermittent summer hypoxia below the halocline (mean depth 15 m) has a severe effect on the benthos of the area, leading to a reduction in epifaunal predation prior to the reduction of macrobenthic organisms. Such events lead to the temporary accumulation of sedimentary carbon before late autumnal mixing initiates the re-oxygenation and eventual recolonization of the affected areas. Comparisons with published carbon budgets for the Chesapeake Bay and the Baltic Sea suggest major differences between the relative roles of pelagos and benthos in these systems. In the Baltic, which is fuelled predominantly by autochthonous processes, pelagic carbon flows are about 4 times those of the benthos. Allochthonous inputs predominate throughout much of the year in the Chesapeake Bay, where pelagic flows are proportionately 1.5 x those of the benthos, whereas in the SE Kattegat benthic flows exceed those within the pelagos by about 25%. The higher populations of epifaunal and nektonic predators found in the SE Kattegat system, as opposed to the other two systems, is a corollary of the greater energy flows through the benthic components. The demonstrable vulnerability to anoxia of these commercially important organisms emphasizes the sensitivity of such coastal systems to the consequences of increased nutrient inputs. |
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