Spatial distribution in sediment characteristics and benthic activity on the northwestern Black Sea shelf

Abstract

The influence of the River Danube as a major source of nutrients and suspended solids to the continental shelf of the Black Sea has been analyzed. In the framework of the EC project EROS-2000, sediment cores from 33 stations on the northwestern continental shelf were sampled in August 1995. Spatial patterns in structural sediment characteristics, macrobenthos composition and benthic mineralization rates were examined using ordination techniques. Three general areas could be distinguished according to the distribution of abiotic sediment characteristics and macrobenthos community:(1) The area just in front of the Danube Delta where large amounts of nutrients and suspended solids are discharged. High sedimentation rates of fine-grained sediments and high benthic mineralization rates characterized this area. The macrobenthos community was dominated by deposit feeders.(2) The northern part of the continental shelf where an anticyclonic gyre is located. The majority of the Danube discharges are transported to this region. This area was characterized by low sedimentation rates. However, the deposited material contained a larger fraction of fresh organic matter compared to the delta area, resulting in high benthic mineralization rates. Suspension feeders dominated the macrobenthos community. (3) The southern part of the continental shelf was characterized by low sedimentation rates and low rates of benthic mineralization. In this area suspension feeders dominated the macrobenthos community. Oxygen fluxes into the sediment ranged between 2 and 52 mm01 0' m-' d-' (average 21 mm01 O2 m-' d-l) decreasing with water depth. Macrobenthos accounted for 20% of the total benthic oxygen consumption. In the northern part of the continental shelf and in the coastal stations, microorganisms, and micro-and meiobenthos dominated benthic community respiration, while macrobenthos became relatively more important in terms of oxygen consumption in the southern part of the continental shelf.

Nitrogen budget of the northwestern Black Sea shelf inferred from modeling studies and in situ benthic measurements

“…To complement our measurements of oxygen fluxes with the benthic chambers and to assess the reliability of these measurements, sediment community oxygen consumption (SCOC) measured by incubation of sediment cores (Wijsman et al 1999, Wijsman 2001 will be used for a comparison. Stainless steel flux chambers are known to artificially increase oxygen flux due to electric potential gradients along the wall of the chamber (Cramer 1989).…”

“…These 2 data sets will be complemented by the results of an INTAS cruise conducted in May 1998. Measurements of benthic fluxes with in situ flux chambers during the EROS-21 and INTAS expeditions revealed large spatial differences in benthic nutrient regeneration (Friedl et al 1998, Wijsman et al 1999, Friedrich et al 2002 in response to the position of the river plume and the associated primary production, the intensity of the vertical mixing and the water depth.…”

On the Influence of the Nearbed Sediments in the Oxygen Budget of a Lagunar System: The Ria de Aveiro - Portugal

“…Accretion of sediment in intertidal areas can be influenced by vegetation: the role of vegetation is complex and is site specific, affected by a variety of physical factors as local topography, wave climate, sediment supply and vegetation patch size. The contribution of living root volume occupied by the different plant species may be important by the addition of the volume itself, as well as by binding sediments and minimising re-suspension (Wijsman, 1999;Brown et al, 1998). Oxygen is involved in the main processes occurring in the upper layer of the bottom sediments, namely, oxygen penetration into the bottom sediments, sediment respiration, nitrification processes (Henriksen et al, 1981;Henriksen and Kemp, 1988) and denitrication processes (Kaspar, 1982) in sediments.…”

An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments

“…However, the shelf is a complicated system, and local environmental conditions such as bottom water temperature, oxygen and nutrient concentrations and pelagic primary production inputs are all known to affect biogeochemical cycling within shelf sediments (e.g. Soetaert et al 1996Soetaert et al , 2000Dollar et al 1991;Wijsman et al 1999;Van Cappellen et al 2002;Fulweiler et al 2010;Dale et al 2011). Because the focus of the SSB work is on bed type, these local conditions are considered confounding variables, which can be a particular problem when smaller-scale variables are extrapolated (Morrisey et al 1992).…”