A Pollution Case Study: The Black Sea

Background  Enclosed sea with only the Bosphorus as communicating waterway with Aegean and Mediterranean Bosphorus Danube

 Small flow of relatively freshwater out and beneath return flow of Aegean water (S~22)  Restricted turnover of deepwater, inputs of carbon  Result is anoxic deep basin  However anoxia developed over many thousands of years; relatively stable, no direct impact on coastal systems  NOTE that no large oxygenated water bodies to dilute any low oxygen waters

 Danube Dneiper and Dniester are major river inputs and all in NW  Adjacent shelf (<200m) circa 25% of total area of Black Sea  Danube conveyor belt collecting pollution from countries en route  Most of these countries are heavily industrialised and very poor treatment of wastes

Nutrient inputs to the NW shelf and Eutrophication  Rivers major input  Increased release to Black Sea of N and P (mid 70s)

 Corresponds to major industrialisation of central and eastern Europe  For Nitrogen, atmospheric input of N containing gases major input ;  Atmosphere =circa 50% of river source; dispersed in contrast to rivers

 Increased phytoplankton biomass, reduction in species diversity, red-brown-green tides Decrease in oxygen

Si fluxes to coastal waters decreased due to dams

Impact on ecosystem Changes in zooplankton:  Some species common pre 1970s, almost gone  Larger planktonic crustacea replaced by smaller species  Explosion in gelatinous species-  e.g. Aurelia aurita increased 1000X from 60s to 80s  Alien species introduced- bloom in gelatinous ctenophore mnemiopsis  Increase in jelly fish likely due to removal of predator (mackerel)

Reduced light due to high phytoplankton destroyed benthic algae (e.g. Phyllophora)  Important as habitat for range of fish and invertebrates Conventional fisheries heavily degraded

Heavy Metals  Recent measurements of dissolved (e.g.) Cu, Cd, Ni, Co only 2-5 times higher than e.g. open Mediterranean, so not at directly toxic levels  Better feel for inputs of metals is in sediments NW shelf has highest values (when normalised to Al) >>Reflects riverine inputs of contaminants to this zone

Organic Pollutants Hydrocarbons high relative to comparable regions, but mainly old & heavily degraded Organo-chlorines similar or lower than comparable regions However very limited high quality data so difficult to assess whole system! Radio-nuclides Chernobyl major impact; introduction by both air and specifically river

Conclusions For decades Black Sea used as waste receptacle Major reduction in quality, particularly in the NW Shelf Eutrophication most obvious problem Extent of problems for other contaminants hard to estimate because of limited data (e.g. synthetic organic compounds)- need for baseline studies Antagonistic and synergistic effects of “pollutant cocktail” unclear Baseline studies will require trained personnel and well equipped labs Money major limiting factor to obvious remediation actions