Role of the meiobenthos in Antarctic ecosystems
Vanhove, S.; Wittoeck, J.; Beghyn, M.; Van Gansbeke, D.; Van Kenhove, A.; Coomans, A.; Vincx, M. (1997). Role of the meiobenthos in Antarctic ecosystems, in: Caschetto, S. (Ed.) Belgian research programme on the Antarctic: scientific results of phase III (1992-1996): 1. Marine biochemistry and ecodynamics. pp. A3/02/001/1-59 In: Caschetto, S. (Ed.) (1997). Belgian research programme on the Antarctic: scientific results of phase III (1992-1996): 1. Marine biochemistry and ecodynamics. Belgian scientific research programme on Antarctica. Federal Office for Scientific, Technical and Cultural Affairs: Brussel. 220 pp., more In: Belgian scientific research programme on Antarctica. Belgian Science Policy Office: Brussel. , more |
| Authors | | Top | - Vanhove, S., more
- Wittoeck, J., more
- Beghyn, M.
- Van Gansbeke, D., more
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| Abstract | To date meiobenthic research remained a big white spot in the systematic-ecological work on Antarctic zoobenthos. Therefore the relative importance of the meiofauna (organisms within the size range of 38-1000µm) in the Antarctic benthic community has been assessed by a combined field ecology and experimental approach. This was done in two contrasting conditions, e.g. the deep sea and low subtidal, where as to the depth of the water column the benthic characteristics were, respectively, indirectly or directly related to primary production. Deep-sea samples were collected at Kapp Norvegia and Halley Bay (Weddell Sea) during the EPOS-leg 3-campaign (summer 1989) with the RV Polarstern at depths between 200 and 2000 m. Samples for the ecological-experimental approach of the meiofauna in the low subtidal were taken at Signy Island (South Orkney Islands), at a water depth of 10 m, opposite the base of the British Antarctic Survey. This was done forthnightly during 18 months in 1991/92 and during the summer of 1994. A set of environmental variables (oxygen, pore-water nutrients, particulate and dissolved organic matter, sediment texture, chloroplastic pigments, bacteria and diatoms) were concurrently monitored. Despite the apparent harshness of the Antarctic environment the meiofauna thrived with high productive stocks, sometimes much higher than their temperate and tropical relatives. Numbers and biomass were more or less seasonal and interannual varying (in the case of the subtidal meiofauna). Correlation with environmental factors revealed that depth, sediment texture, oxygen availability, variations in organic matter flux to the sediment surface, and hence food, governed the meiobenthic distribution patterns. Towards this, minimum nematode production constituted 2% of primary production in the pelagial and 11% of the downward flux of organic matter to the seabed. The energetic position of the meiofauna, and their share in the remineralization processes and hence, reintroduction of regenerated nutrients and organic carbon through the sediment/water interface back into the water column, was inferred from flux measurements of nutrients, oxygen and organic matter. Grazing experiments with radiolabeled isotopes, used to quantify the carbon transfer between microbiota and their meiobenthic grazers (mainly epistratum and non- selective deposit-feeders), showed a clearance rate of 5.1 .10-4.h-1. Yet, about 10% of the annual benthic carbon production was grazed down by the nematodes. Nutrient and oxygen fluxes were measured from concentration changes in incubation chambers and vertical profiles in the sediment core. The results evidenced an efflux of ammonia and phosphate to the water column, and an uptake of nitrate and silicate by the sediments, Respiratory activity was measured by a combined method of individual nematode and bulk sediment oxygen uptake. With an individual respiration of 0.89-2.77 nl O2.ind-1.h-1 (Q10 = 2) the nematode community contributed to a substantial proportion of benthic remineralization processes ( 13-42% of the total benthic carbon demand was due to nematode respiration). Secondary production by the nematode community at Factory Cove was among the highest in the world (P varying between 2.2 and 72.4 gC.m-2.y-1), and accounted for 9.4 % of total benthic production, 4.1 % of phytoplankton production and 11.9 % of microphytobenthic production. From the flux measurements and production estimates it was suggested that, by using the substantial episodic food supply (both from water column and in situ production) very efficiently, the meiofauna might play a potentially important role in the energy-transfer through the differing benthic components and from the sediment back into the water column. |
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