Abstract
Benthic metazoa and stained foraminifera (>32 μm) were studied in relation to prevailing environmental parameters in the Aegean Sea (Sporades Basin and Cretan Sea) and Levantine Basin (Ierapetra Basin) during the METEOR Cruise 40 Leg 3 (December 1997–January 1998). The sampling stations differed in nutrient contents, which were indicative of the oligotrophy of the eastern Mediterranean Sea. Meiobenthic abundance decreased significantly with depth and the total standing stock in the top 6 cm sediment layer was significantly higher at the northern stations (204-231 ind./10 cm 2 ). In the abyssal Ierapetra Basin, the abundance for all meiobenthic taxa was minimal (10-26 ind./10 cm 2 ). Nematodes and foraminifera were dominant and accounted together for 79-93% of the total abundance. All taxa were concentrated near the surface of the sediment and only nematodes showed a deeper penetration into the sediments in the Sporades Basin. Concentrations of chloroplastic pigments, total organic carbon and total organic nitrogen were higher in the Sporades and Ierapetra Basins than in the Cretan Sea, reflecting: (a) the different productivity levels and, thus, the higher food availability in the former than in the latter; (b) the seasonal accumulation of organic matter from the euphotic zone down to the abyssal trenches; and (c) the transportation of large amounts of sediment and organic matter in the Sporades and Ierapetra Basins, which are located at the mouth of submarine canyons, through riverine inputs, flush flooding, sediment failure and dense shelf water cascading. Meiofaunal abundances in the Aegean Sea were positively correlated with chlorophyll a , phaeopigments and chloroplastic pigment equivalent (CPE), and were not correlated with any of the remaining sediment descriptors, thus indicating the dependence of meiofauna on food availability.
Highlights
Deep-sea sediments are food-limited environments, in which benthic communities depend strongly on the amount of organic matter reaching the sea floor (Rowe, 1983; Thiel, 1983; Gooday and Turley, 1990)
Meiofaunal abundances in the Aegean Sea were positively correlated with chlorophyll a, phaeopigments and chloroplastic pigment equivalent (CPE), and were not correlated with any of the remaining sediment descriptors, indicating the dependence of meiofauna on food availability
Since primary production decreases with distance from shore and energy transfer to the sea floor decreases with increasing water depth, benthic standing stock and biomass decrease towards more oligotrophic regions and at greater depths (Thiel, 1975)
Summary
Deep-sea sediments are food-limited environments, in which benthic communities depend strongly on the amount of organic matter reaching the sea floor (Rowe, 1983; Thiel, 1983; Gooday and Turley, 1990). Since primary production decreases with distance from shore and energy transfer to the sea floor decreases with increasing water depth, benthic standing stock and biomass decrease towards more oligotrophic regions and at greater depths (Thiel, 1975). This relationship applies to the larger benthic organisms and to all benthic size classes, including meiofauna, macrofauna and the deposit-feeding megafauna (Thiel, 1983; Lampitt et al, 1986; Sibuet et al, 1989; Vincx et al, 1994). Exceptions to this general pattern are the high meiofaunal abundances found in abyssal trenches (Tselepides and Lampadariou, 2004), and the higher abundances found in areas with seasonally or spatially higher production rates and areas with increased terrigenous organic matter inputs (Danovaro et al, 2000; Lampadariou and Tselepides, 2006)
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