159 resultados para Local and regional procurement and distribution
Resumo:
Dependence of the faunal composition and species structure of the White Sea littoral Harpacticoida on sediment properties was studied. Three groups of species could be distinguished according to their relationship with sediment properties: (1) species typical of silty sediments, (2) species preferring sediments with high gravel content, and (3) species inhabiting well-sorted washed sands. Vertical distribution of crustaceans within sediments of different types was studied. Vertical migrations of harpacticoids (3) during the tidal cycle were described. Data on interannual variability of harpacticoid fauna are presented.
Resumo:
A set of 43 sediment cores from around the Canary Islands is used to characterise this region, which intersects meridional climatic regimes and zonal productivity gradients in a high spatial resolution. Using rapid and nondestructive core logging techniques we carried out Fe intensity and magnetic susceptibility (MS) measurements and created a stack on the basis of five stratigraphic reference cores, for which a stratigraphic age model was available from d18O and 14C analyses on planktonic foraminifera. By correlation of the stack with the Fe and MS records of the other cores, we were able to develop age depth models at all investigated sites of the region. We present the bulk sediment accumulation rates (AR) of the Canary Islands region as an indicator of shifts in the upwelling-influenced areas for the Holocene (0-12 ky), the deglaciation (12-18 ky) and the last glacial (18-40 ky). General observations are an enhanced productivity during glacial times with highest values during the deglaciation. The main differences between the analysed time intervals we interpret as result of the sea-level effects, changes in the extent of high productivity areas, and current intensity.