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ENVIROMENTAL RISK ASSESSMENT OF MARINE 11
INVASIVE SPECIES CARRIED BY BALAST WATER

caused the extinction of anchovy, which has huge economic importance for fishery, and also
resulted in high amount of pollution on the bottom of the sea with other negative effects on
ecosystem [10]. Because of these negative impacts on environment it was scored with the
highest number ‘4’.

Mnemiopsis leidyi has very high reproduction rate because adult ones can produce 2000-8000
eggs during spawning and the population of the invader reaches high amounts easily. After
invasion of Black Sea, they spread through Marmara and Mediterranean seas quickly so they get
also the highest score for reproduction rate and invasive potential assessment.

Mnemiopsis leidyi is followed by Prorocentrum minimum which is a native phytoplankton in
Atlantic coasts of America and introduced to Black Sea by ballast waters. Prorocentrum
minimum is a common, neritic, bloom-forming dinoflagellate, is the cause of harmful blooms in
many estuarine and coastal environments. The toxic algae can be accumulated in the food chain
and reach to humans via seafood consumption [16].

The invasive species with the lowest risk index number is Rapana venosa with no vital effect on
ecosystem and native species [17]. Although it invaded three seas of Turkey which are Aegean
Sea, Black Sea and Marmara Sea, negligible effects on ecosystems and easy management for
eradication keeps it at the bottom of the risk index table.

Table 7. Risk Indexes of Marine Invaders

Species Ecological Frequency Risk İndex References
Impact Factor
Mnemiopsis leidyi Number 4,20 [5]
15 0,28
Prorocentrum minimum 2,48 [16]
Caulerpa toxifolia 9 0,28 2,12 [7]
Collinectus sapidus 10 0,21 1,84 [18]
Polydora cornuta 11 0,17 1,84 [19]
Beroe ovata 11 0,17 1,50 [20]
Asterias amurensis 9 0,17 1,13 [21]
11 0,10 1,09 [22]
Phyllarhiza punctata 8 0,14 1,03 [23]
Bryopsis pennata 10 0,10 0,82 [17]
Rapana venosa 8 0,10

The results show that Mnemiopsis leidyi requires the most attention and prevention from future
introductions because of its high risk index number. Therefore ships carrying ballast water from
Atlantic Coasts of North and South America needs to be prioritized for investigations and
controls. However most of the countries have limited funds for ballast water management so
prioritization of ships and regions is essential as well as the local studies and classifications.

Sayı 5, 2016 GiDB|DERGi