Spatial and temporal variability in the chemical properties of the oxic and suboxic layers of the Black Sea

2014-07-01
Tuğrul, Süleyman
Murray, James W.
Friederich, Gernot E.
Salihoglu, Ilkay
The Black Sea, a land-locked deep basin with sulfide bearing waters below 150-200 m, has been subject to anthropogenic pressures since the 1970s. Large inputs of nutrients (nitrate - N, phosphate - P, silicate - Si) with high N/P but low Si/N ratios and subsequent development of intensive eutrophication over the basin have changed vertical distributions and inventories of nutrients and redox-sensitive metals in the oxic, suboxic and anoxic layers. Chemical data sets obtained between 1988 and 2010, and older data from before 1970 were evaluated to assess spatial/temporal variations of the dissolved oxygen (O-2), nutrients and dissolved/particulate manganese (Mn-d, Mn-p) in the water column from the lower salinity, oxygenated surface waters through the SubOxic Layer (SOL; O-2 50). The surface waters over the basin were rich in silicate (25-70 mu M), but poor in nitrate (500) but very low N/P (<1.0) ratios. After the mid 1970s, construction of dams, especially on the Danube River, resulted in lower Si concentrations. At this time the increased loads of anthropogenic nitrate and phosphate by the major rivers resulted in lower Si/N, but still high N/P molar ratios, which enhanced eutrophication (production of particulate organic matter, POM) drastically in the coastal waters. This led to reductions in the surface Si/N ratio by up to 500-fold in the western basin while the N/P ratio increased. The enhanced POM export increased the nitrate inventory and thus N/P ratios of the NW shelf waters spreading over the whole basin. The increased export of POM decreased the Si inventory of the upper layer down to the boundary of sulfidic waters. This export also increased O-2 consumption and removal of nitrate to N-2 form by denitrification in the oxic/suboxic interface, leading to seasonal/decadal changes in the boundaries of the nitracline and main oxycline and changes in the slopes of the nitrate-phosphate and Apparent Oxygen Utilization (AOU)-nitrate regressions in the steep oxycline down to the SOL. These slopes are much smaller than those observed in the lower layer of Marmara Sea fed by the Black Sea outflow. The enlargement of SOL by similar to 15-20 m after the 1970s modified the vertical features of nitrate, phosphate and manganese (Mn-d, Mn-p) species in the redox gradient zone.
JOURNAL OF MARINE SYSTEMS

Suggestions

Particulate and dissolved primary production along a pronounced hydrographic and trophic gradient (Turkish Straits System-NE Aegean Sea)
Lagaria, A.; Psarra, S.; Gogou, A.; Tuğrul, Selen; Christaki, U. (Elsevier BV, 2013-06-01)
The rates of particulate (PPp) and dissolved primary production (PPd) were estimated along a trajectory of variable environmental regimes formed in a narrow shelf area, following the course of Black Sea water masses (BSW) passing through the Turkish Straits System (TSS) into the NE Aegean Sea (BS-AS outflow). Seven stations in total were sampled, covering a transect from the eastern edge of the Marmara Sea basin to the NE Aegean Sea, during two consecutive cruises performed in October 2008 within the framew...
Spatial and temporal variations of tintinnids (Ciliata: Protozoa) in the Bay of Mersin, Northeastern Mediterranean Sea
POLAT, SEVİM; TERBIYIK KURT, TUBA; Tuğrul, Süleyman (National Documentation Centre (EKT), 2019-01-01)
Seasonal variations in species composition and abundance of tintinnids were investigated in the eutrophic coastal and offshore waters of Mersin Bay. Twelve sampling cruises were performed from September 2008 to February 2011. A total of 85 tintinnid taxa were identified. Among the recorded genera, agglutinated Tintinnopsis had the largest number of species (12 species), followed by hyaline loricated Eutintinnius (9 species), and Proplectella (7 species). Stenosemella ventricosa, Tintinnopsis beroidea, T. co...
Water Exchange through Canal İstanbul and Bosphorus Strait
Sözer, Adil; Ozsoy, E. (National Documentation Centre (EKT), 2017-2-13)
The Turkish Straits System (TSS) regulates the transports of water, material and energy between the Black Sea and the Mediterranean Sea. Amidst existing environmental threats to the region surrounding I.stanbul, the environmental footprint of the proposed Canal I.stanbul project needs to be evaluated through methods of natural science. We take the elementary step to answer the particular problem of coupled strait dynamics by adding the Canal to an existing hydrodynamic model and estimate changes in their co...
A comparison of the contribution of zooplankton and nekton taxa to the near-surface acoustic structure of three Turkish seas
Mutlu, E (Wiley, 2005-03-01)
The bioacoustics of upper waters of the Black Sea, the Sea of Marmara, and the Mediterranean Sea were studied in October 1999 with an echosounder with 120 and 200 kHz dual-beam transducers. Net tows were taken to ground-truth the acoustic volume backscattering. A forward solution was applied to determine significant scatterers of the three seas with regard to detection limits of the frequencies and background noise measured in each sea. The noise was 4 dB higher in the Sea of Marmara than in the other two s...
Distribution and abundance of ctenophores and their zooplankton food in the Black Sea. II. Mnemiopsis leidyi
Mutlu, E (Springer Science and Business Media LLC, 1999-12-01)
The distribution of Mnemiopsis leidyi Agassiz, 1865 in the Black Sea was determined using plankton samples collected above the anoxic zone (maximum depth 200 m) in the summer, winter, and spring from 1991 to 1995. Distribution was patchy. Average biomasses of 15 to 500 g m(-2) were measured, and abundances varied from 10 to 180 ind m(-2). Biomass and abundance peaked in winter, and there was a secondary peak in the summer. The distribution of M. leidyi was correlated with hydrographic features in the Black ...
Citation Formats
S. Tuğrul, J. W. Murray, G. E. Friederich, and I. Salihoglu, “Spatial and temporal variability in the chemical properties of the oxic and suboxic layers of the Black Sea,” JOURNAL OF MARINE SYSTEMS, pp. 29–43, 2014, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/56830.