According to the State of Europe´s seas report, available information shows that the main pathway of non-indigenous species introduction in European seas is shipping (51 %), followed by the Suez Canal (37 %), aquaculture-related activities (17 %), the aquarium trade (3 %), and inland canals (2 %). Large scale biodiversity patterns are modified causing entire shifts to the novel habitats, with substantially modified ecosystem functions.

Source: EURO-Lex

See: Ecosystem.  A complex of organisms and their environment, interacting as a defined ecological unit (natural or modified by human activity, e.g. agroecosystem), irrespective of political boundaries.

Source: EEA Glossary