Recent and quaternary deep-sea ostracoda from the sub-polar North Atlantic : paleoecological and paleoceanographical applications

Abstract

The potential impact of the environmental changes that our planet is currently undergoing is of major concern to current ecological research. Both, natural and anthropogenically induced, their assessment, extent and consequences consume the efforts of scientists. This thesis focuses on elucidating dominant environmental factors controlling meiobenthic distribution patterns to provide insight into this area, in particular the impact of environmental change on the deep sea. Deep-sea research remains a comparably neglected field of study: commonly perceived as remote where conditions shift slowly, it is regarded relatively immune to environmental shifts at the surface. This thesis challenges the validity of this conception. Here, I assess deep, sub-polar North Atlantic ostracod assemblages from the climatically sensitive region of Icelandic and adjacent waters. Their abundance, diversity, species composition, and both living and fossil assemblages are reported. Both temporal, and spatial distribution patterns were investigated to discern predominant environmental factors, responsible for the observed faunistic trends. Temporal distribution studies focused on the understudied Pleistocene glacial/interglacial transition between 592,8 ka and 362,4 (MIS 15–10). Spatial distribution patterns were regarded in their geographical and in-situ vertical context. Knowledge regarding vertical distribution of infaunal ostracods within the seafloor is essential for accurate interpretations of paleo-assemblages. This thesis presents the first findings on the in-sediment depth range of ostracods in deep-sea environments. Another pioneering technique applied here was the use of statistical regression models, evaluating environmental parameters for their potential to control observed faunistic patterns. Regression models to test controlling factors have never been applied before in this context. This thesis also provides a detailed taxonomy of sub-polar North Atlantic ostracods from Pleistocene and Holocene sediments with phylogenetic information. Such an overview establishes an essential baseline for detecting faunal change in future monitoring programs. Six deep-sea species potentially new to science are described here. Suitable indicator taxa for effective environmental reconstruction are isolated. The results of this thesis indicate that the idea of the deep sea being unaffected by environmental changes is a misconception. Both, particulate organic carbon and near-bottom temperatures show major control over species richness in the deep sea, establishing that these ecosystems are sensitive to climatic shifts and anthropogenically-induced changes at the surface. The work presented here expands the ostracod toolkit of marine research. Ecological regression models applied to assemblage data sets have determined dominant controlling factors of species richness patterns. Observed environmental preferences to specific depth ranges, or near-bottom temperatures of major genera were statistically validated. The vertical depth distribution of living benthic deep-sea ostracods was recorded in detail, revealing them to be either epifauna or shallow (0.5–2 cm) and very shallow (0–1 cm) infauna. The significance of the sampling area, in respect to its complex hydrography and bathymetry, broad geographical range, and its vulnerability to global warming, further increases the scientific importance of this study.