Benthic response to chronic natural physical disturbance by glacial sedimentation in an Arctic fiord
Wlodarska-Kowalczuk, M.; Pearson, T.H.; Kendall, M.A. (2005). Benthic response to chronic natural physical disturbance by glacial sedimentation in an Arctic fiord. Mar. Ecol. Prog. Ser. 303: 31-41
The activity of Arctic tidal glaciers results in high turbidity, high rate of inorganicparticulate sedimentation and sedimentary instability in near-glacier marine basins. The chronicphysical disturbance of sediments is accompanied by low input levels of organic matter. The responseof soft-bottom macrofauna to glacial disturbance was studied in Kongsfjord, Svalbard. The quantitativecharacteristics of the macrofauna of 4 associations located along a gradient of glacier-induceddisturbance were examined. Benthic biomass decreased with increased proximity to the glacier (from10.9 g wet weight (ww) m-2 in the outermost association to 2.7 g ww m-2 in the glacial bay). Faunaldensity was highest in the transitional zone (592 ind. 0.1 m-2) between the central basin (425 ind.0.1 m-2) and the inner glacial bay (442 ind. 0.1 m-2). The average individual biomass was lowest in theglacial bay as a result of the smaller body size of organisms. A decrease in the size of organisms indisturbed sites was not accompanied by a classical shift from ‘equilibrium’ to ‘opportunistic’ species.The functional structure of the faunal associations was simplified in the impoverished glacial bayassociation where 1 guild, the mobile surface-detritus feeders, strongly dominated. Average speciesnumber per sample was lowest in the glacial bay (22 species) and highest in the transitional association(42 species). Species diversity expressed by the Shannon-Wiener and Hurlbert rarefactionindices and evenness expressed by the Pielou index was lower in the glacial bay than in the remainingassociations. The decrease in biomass, mean size of organisms, species diversity and evenness aswell as the peaked distribution (i.e. maximum in the transitional zone) of density and species richnessare consistent with patterns reported in studies of different natural and anthropogenic disturbances.Some distinct features of the case of glacial-induced disturbance include relatively high taxonomicdistinctness and low beta diversity and low faunal dispersion in the near-glacier association.
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