North-East Estonian coastal sea: recovery from the past anthropogenic pressure and new stressors on the background of natural variability

Abstract

The heavily industrialized NE part of Estonia has been an environmental hot spot for decades. The oil shale industry, thermal power plants, a cement factory and a Soviet-era depository of radioactive wastes have seriously impacted virtually every component of the environment. This study focuses on environmental changes in the coastal sea, which comprises the southern part of the Gulf of Finland. It is based on national marine monitoring data (since 1968), as well as on recent in situ measurements on hydrodynamics, pollution spread, and on bottom habitat recovery. Starting from the 1990s, improvement of the water quality in the Gulf of Finland is evident. After re-orientation into market economy, substantial economic recession took place in Estonia in the 1990s. The pollution load from both industrial sources and from Narva River decreased. On the other hand, new water protection directives were introduced. However, together with economic growth in the 2000s, some new threats arose, e.g. in relation with the construction of ports at Kunda, Muuga, Sillamäe, and a new pulp mill at Kunda. The replacement of oil shale-based energetics with a nuclear power plant is currently under discussion.

Hazardous substances in the water, biota and sediments of the North Estonian coastal sea

“…During the economic peak of 1980s, Kohtla-Järve and Kiviõli chemical companies discharged substantial amounts of phenols (650 t/yr), oils, and different hazardous substances to the rivers and coastal sea [2,3,15]. Due to a more than two-fold decrease in production, as well as construction of wastewater treatment plants over the last two decades, the pollution load to the coastal sea has decreased nearly two-fold.…”

“…1), which has an area of 29 500 km 2 and average depth of 37 m. The Gulf receives a relatively large pollution load both from rivers (Neva, Narva, Kymijoki), as well as from industries and municipalities [2,3]. The circulation scheme in the Gulf of Finland is mostly wind-driven and although certain statistical long-term patterns can be found [16], it is quite variable in time and space.…”

“…Although some blue-green algae produce natural toxins in substantial quantities, which can affect, for instance, reproduction and growth of fish [18], the anthropogenic (synthetic) toxic and hazardous substances vastly dominate in the marine environment. Despite the recent reduction in pollution load and good hydrodynamic dilution conditions, the area has not yet fully recovered from the past anthropogenic pressure [2] and some persistent compounds are bioaccumulated in the biota and bottom sediments [4,11].…”

“…It is also the major pollution source and a "hot spot" for the whole Baltic Sea environment [2,3]. Therefore, the main efforts in the monitoring of hazardous substances in Estonia have been concentrated into that area.…”