Alien Species And Their Impacts In The Black Sea

Abstract

The Black Sea, a unique fragile ecosystem, has been under the threat of pollution, climate change, invasive alien species and overfishing over many years. Combined impacts of these threats caused serious problems in the Black Sea ecosystem, fisheries economy and welfare of Turkish fishermen by reduction of the catch of commercial fish species, decrease in biodiversity, loss of habitats, increased food competition of endemic species and related problems in the food web by changes in various trophic levels. In this presentation the impacts of the alien invasive species will be explained on certain species basis in the Black Sea. Unintentionally introduced new species to a certain area are known as invasive species. Alien species that become invasive are considered to be a main direct drive towards biodiversity loss across the globe. In addition, alien species have been estimated to cost global economies hundreds of billions of dollars each year (CBD, 2011). Some of the alien species i.e. Rapana venosa, Anadara inaequivalvis, Mnemiopsis leidyi, Beroe ovata, Mya arenaria, Balanus improvisus, Mugil soiuy, Potamopyrgus jenkinsi caused significant impacts on the Black Sea ecosystem and fisheries. All kinds of impacts due to invasive species had a big effect on the reduction of total fish production in the Black Sea as predation, food competition and major destruction in the food web. There are many other species introduced to the Black Sea from phytoplankton to top predators. Some of the invasive alien species and their impacts in the Black Sea are summarized in Table 1. Research studies on the impacts of alien species to the ecosystem and fisheries economy are very limited in the Black Sea. In order to support the ecosystem recovery in spite of all types of negative impacts for the sustainable management of the natural resources, it is very essential to understand, analyze and take urgent management measures regarding all aspects of the ecosystem. New research studies in the Black Sea should be focused on prey-predator relationships, reproduction and growth rates of invasive species, relationship between their distribution and environmental factors, assessment of limiting factors, natural barriers and mechanisms, etc.