Interannual and regional variability of ecosystem dynamics in the BlackSea

Fach, Bettina A
Cannaby, H.
Dorofeyev, Vl
Kubryakov, Aı
Salihoğlu, Barış
Korotaev, Gk
Oğuz, Temel
Kıdeyş, Ahmet Erkan
A three-dimensional hydrodynamic ecosystem model developed for the Black Sea was used to investigate theinfluence of anthropogenic drivers on marine ecosystem functioning in the Black Sea with a special focus onregional differences. Data from the ECMWF 40 Year Re-analysis global atmospheric circulation model (ERA-40)were used to force a coupled hydrodynamic ecosystem model (BIMS) for a hindcast simulation from 1980-2000.Model skill was assessed by model comparisons with SeaWiFS surface chlorophyll distributions. We studythe regional differences the introduction of invasive comb jelly Mnemiopsis leidyi has on modeled ecosystemdynamics as well as the regional influence of changing river nutrient loads on ecosystem dynamics.We can demonstrate clearly that the appearance of M. Leidyi changes ecosystem functioning through exertinggrazing pressure on zooplankton and thereby changing the seasonal cycle of phytoplankton and zooplanktonspecies significantly. On the north-western shelf this effect is less pronounced than in the southeast Black Sea,where zooplankton is grazed down more heavily, allowing for higher phytoplankton biomass. In addition, theBlack Sea ecosystem shows strong regional nitrate limitation, and high sensitivity to increased eutrophication:A 50% increase in nutrient loading causes a 48% increase in primary production in the eastern regions of theBlack Sea, while the north-western shelf reacts more moderately. Despite an increase in primary production,chlorophyll-a concentrations typically respond weakly to changes in nitrate availability. This indicates thatincreased grazing closely mirrors an increase in productivity. This is confirmed by an increase in zooplanktonbiomass. It is important to note that for this reason simulated chlorophyll concentration is not a good indicator ofeutrophication in the Black Sea. The reduction in the productivity of the entire Black Sea system associated with areduction in riverine nutrient loadings is much greater than the increase in productivity associated with an increasein nutrient loadings. Hence the model simulations represent a Black Sea ecosystem, which is highly sensitive toa reduction in nutrient loadings, suggesting management of river water quality is vital for the improvement of theecosystem state of the Black Sea.
Citation Formats
B. A. Fach et al., “Interannual and regional variability of ecosystem dynamics in the BlackSea,” presented at the European Geosciences Union General Assembly (EGU2013-12174), (01 - 31 Ocak 2013), 2013, Accessed: 00, 2021. [Online]. Available: