Evaluating the influence of river discharge on marine benthic ecosystems using benthic foramanifera and lithology as the main tools

Abstract

River discharge has a significant impact on marine environment through its effect on the salt balance of the thermohaline structure and convection circulation of the water masses. Being enriched in the various organic and inorganic compounds, river flow is actively involved in biological processes and sedimentation, affecting the equilibrium state of the benthic ecosystems. Spatial distribution of river flow in the marine environment depends on meteorological and hydrological conditions that are characterized by inter-annual variability and varying proximity to the source. Coastal areas located in the confluence of major rivers experience the strongest impact of freshwater discharge. The northwestern shelf of the Black Sea—where the second largest river in Europe, the Danube, discharges annually 190.7 knf and 51.7 million tonnes of liquid and solid waste, respectively (Bondar et al., 1991; Panin, 1996), is a good example of such areas. Tracing the spatial distribution of river water into the sea and assessing its impact on benthic ecosystems have important theoretical and practical significance, both for understanding the causes affecting their balance, and for the development of methods and approaches to maintain their stability. Therefore, the choice of a reliable group of organisms as indicators of river discharge into the sea has primary significance. Such organisms should be benthic, small in size, and abundant (for population statistics), have a short life cycle, and be well preserved after death.