Abrupt transition of the northwestern Black Sea shelf ecosystem from a eutrophic to an alternative pristine state

Download

index.pdf

Date

2010-01-01

Author

Oguz, Temel
Velikova, Violeta

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

290
views

0
downloads

Long-term (1960-2005) ecological data were used to identify a regime shift in the northwestern Black Sea shelf and to assess whether it has recovered from its former eutrophic state. Following the collapse of fish stocks and the population explosion of the ctenophore Mnemiopsis leidyi between 1988 and 1991, anthropogenic P-PO4 loads from the River Danube dropped strongly in 1992-1993. This decline in P-PO4 levels was caused by reductions in fertilizer use and emissions from land-based point sources during the economic recession of former Eastern Bloc countries, as well as by the low discharge rate of the River Danube. Commencing in 1993, the phosphate limitation apparently maintained a low-energy, inefficient food web dominated by the dinoflagellate Noctiluca scintillans and jellyfish, and relatively low levels of phytoplankton, bacterioplankton, mesozooplankton and fish. This 'post-eutrophication' regime was markedly different from the classical phytoplankton-mesozooplankton-fish chain of the similarly low nutrient 'pre-eutrophication' regime prior to 1970. Therefore it appears that the food web can attain 2 alternative regimes during periods of low productivity of the ecosystem. The post-eutrophication state cannot be considered as a major improvement or restoration of the northwestern coastal ecosystem.

Subject Keywords

Black Sea, Trophic control, Regime shift, Alternative community states, Nutrient limitation, Coastal eutrophication

URI

https://hdl.handle.net/11511/64509

Journal

MARINE ECOLOGY PROGRESS SERIES

DOI

https://doi.org/10.3354/meps08538

Collections

Graduate School of Marine Sciences, Article

Suggestions

OpenMETU
Core

SEASONAL TO DECADAL VARIABILITY IN THE PHYSICAL AND BIOLOGICAL PROPERTIES OF THE BLACK SEA AND LEVANTINE BASIN AS INFERRED FROM SATELLITE REMOTE SENSING Akpınar, Anıl; Fach Salihoğlu, Bettina; Department of Oceanography (2016-12-10) Black Sea and Eastern Mediterranean (Levantine basin) have gone through a number of documented changes in the recent decades. Recently acquired satellite data document rapid warming, increased sea level and decreased chlorophyll-a (phytoplankton) in the Black Sea and Levantine basin. Aim of this study is to address warming in the Black Sea and Levantine basin, as well as to investigate the phytoplankton response to changing environmental conditions at seasonal to interannual timescales. In the first part of...
Current state of overfishing and its regional differences in the Black Sea OGUZ, Temel; Akoğlu, Ekin; Salihoğlu, Barış (2012-03-01) Long-term (1950-2006) changes of fish landings in combination with some ecosystem indicators are used to evaluate the status and sustainability of the Black Sea fishery. Following the depletion of large pelagic predator and demersal fish stocks during the 1950-1960s, the main fishery was targetted on small and medium pelagics that declined abruptly to similar to 200 kton (kton 10(3) t) at 1989-1991 after a highly productive (similar to 750 kton) but overfished state in the 1980s. Thereafter, total landings ...
Seasonal Changes in the Composition and Abundance ofZooplankton in the Seas of the Mediterranean Basin Kovalev, Av; Mazzocchı, Mg; Toklu Alıçlı, Benin; Skryabın, Va; Kıdeyş, Ahmet Erkan (2003-01-01) Seasonal changes in the composition, abundance and biomass of zooplankton in the seas of the Mediterranean basin (the Mediterranean, Black and Azov seas) have been reviewed using our own data and data from the literature. In the deep-water central regions of the seas, the seasonal cycle of zooplankton abundance is characterised by one maximum occurring in spring or summer. In the coastal regions, two to three peaks (spring, summer and autumn) exist for the zooplankton abundance. The amplitude of seasonal fl...
Recent changes in the spawning grounds of Black Sea anchovy, Engraulis encrasicolus Gücü, Ali Cemal; Ok, Meltem; Sakinan, Serdar (2016-01-01) Towards the end of the 1980s, when the spawning grounds in the northwestern shelf (NWS) of the Black Sea were lingering with the effects of eutrophication and of an exotic invasive ctenophore, a series of basin-wide international ichthyoplankton surveys pointed out an increase in the anchovies spawning in the southern half of the Black Sea. Later, with the help of international conservation efforts, several key littoral ecosystem components within the anchovy's historical spawning grounds showed signs of re...
The diel vertical distribution of zooplankton in the southeast Black Sea Erkan, F.; Gücü, Ali Cemal; Zagorodnyaya, J. (2000-01-01) The diel changes in the vertical distribution of zooplankton in the southeast Black Sea were described in this study. The zooplankton were sampled using two different sampling methods throughout one day in October 1996 and July 1997 at the same station. The zooplankton counts, the length measurements and biomass estimates showed that the zooplankton in the southeast Black Sea is dominated by small organisms, among which Noctiluca scintillans is the dominant species. In the vertical distribution of zooplankt...

Citation Formats

T. Oguz and V. Velikova, “Abrupt transition of the northwestern Black Sea shelf ecosystem from a eutrophic to an alternative pristine state,” MARINE ECOLOGY PROGRESS SERIES, pp. 231–242, 2010, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/64509.