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ENVIROMENTAL RISK ASSESSMENT OF MARINE 7
INVASIVE SPECIES CARRIED BY BALAST WATER

study by combining their qualifications with a threat scoring system based on several existing
threat classification systems [12-14]
In this study four characteristics of invasive species were examined and from each
characteristic, every single species got an impact number and all these numbers are summed up
for total ecological impact factor for every single invasive species. Table 1 shows the negative
impact of invaders on a native ecosystem.

Table 2 presents the reproduction and invasive potential of invaders by a scoring system, as ‘4’
refer that the species has high reproduction rate and rapidly invaded areas after past
introductions and has huge potential of invasion after new introductions. ‘1’ is used for species
with low reproduction rate and has not invaded huge areas after past introductions but still has
some potential for spreading with new introductions.

Table 3 simply shows the number of seas invaded by invasive species. Turkey has 4 seas which
are Black Sea, Marmara Sea, Aegean Sea and Mediterranean Sea.

Table 1. Negative Impact on Ecosystem of Invaders [4]

Negative Impact on Ecosystem Score

Negative impact on entire ecosystem and biodiversity, reason for 4 (Very High)
extinction of native species 3 (High)

Impact on multiple species, keystone species or change dominant 2 (Medium )
native species 1 (Low)

Impact on single native species with little disruption

No important impact on any species and ecosystem

Table 2. Reproduction and Invasive Potential [4]

Reproduction Rate and Invasive Potential Score

High reproduction rate, currently spreading rapidly 4 (Very High)
3 (High)
Medium reproduction rate, currently spreading less rapidly
2 (Medium )
Low reproduction rate and did not spread yet but huge future 1 (Low)
potential for spreading

Low reproduction rate and did not spread and low future potential
for spreading

Sayı 5, 2016 GiDB|DERGi