Ecological function of the North Caspian Sea: Production, nutrients and pollutants

TitleEcological function of the North Caspian Sea: Production, nutrients and pollutants
Publication TypeConference Paper
Year of Publication2004
AuthorsTartowski S., Butler T.J., Lychagin M.Y., Bashkin V., Sisengalieva G., Yergaliyev T.
Conference Name89th Annual Meeting, Ecological Society of America
Date PublishedAugust 1, 2004
Conference LocationPortland, OR
ARIS Log Number168838
Keywordscurrent ecological status, North Caspian Sea, nutrients, pollutants, production
AbstractThe Caspian Sea is the largest inland water body on earth (386,400 km2, maximum depth 1025 m). With its long history of oil and industrial development, the Caspian is often regarded as severely polluted and ecologically degraded. The North Basin of the Caspian Sea is a large (25% of the Caspian Sea surface area), shallow (median depth 4 m), well-mixed, slightly brackish estuary fed by the Volga and Ural Rivers. We have synthesized historical Soviet data, post-Soviet data and data from a recent sampling cruise in September 2003 to investigate the current ecological status of the North Basin of the Caspian Sea. The Volga River supplies approximately 80% of the water input to the entire Caspian Sea and is the major source of nutrients and pollutants to the North Basin. The North Basin of the Caspian Sea is less polluted with heavy metals, pesticides and probably hydrocarbons than commonly assumed and less polluted now than during the Soviet era. Pollutant levels in organisms such as fish and seals are generally lower or comparable to those of other large seas and lakes, such as the Mediterranean, Black, and Baltic Seas. Autochthonous primary production supplies the majority of the organic carbon inputs with more than 50% provided by phytoplankton (14-22 TG C /yr) and about 4-9 TG C /yr added by the Volga River. Primary production in the North Basin is usually phosphorus-limited and significant oxygen depletion seldom develops. Commercial fish stocks in the North Caspian have declined significantly in recent years due to overfishing. The Caspian Sea supplies about 90% of the world's caviar but less than 1% of the remaining Beluga sturgeon (Huso huso) are mature breeders. Accurate, independent information on the size and age class distribution of valuable sturgeon species and the Caspian Seal are not available.