The good status of the marine environment with regard to the quality descriptor of non-indigenous species resulting from human activities is achieved when the presence of non-indigenous species does not harm the ecosystem, namely: the number of newly introduced non-indigenous species into nature resulting from human activity for each assessment period, measured from the reference, is reduced to a minimum; the abundance and spatial distribution of established non-indigenous species, especially invasive ones, which have a significant adverse effect on species and EUNIS2 habitat types is limited; the proportion of species or spatial range of the EUNIS2 habitat types resulting from the adverse effects of non-indigenous species, in particular invasive species, is negligible.

D2C1: Newly introduced non-native species The number of non-native species newly introduced through human activity into the wild per assessment period (six years), measured from the reference year and reported in the initial assessment, is minimised and where possible reduced to zero.

The number of non-indigenous species newly introduced into the natural environment through human activities per assessment period (six years), counted from the reference year used for the initial assessment carried out in accordance with Article 8(1) of Directive 2008/56/EC, shall be minimised and, if possible, reduced to zero (Decision 2017/848/EU).

D2C2: Established non-native species, in particular non-native invasive species that are included in the list of relevant species for use in the assessment of the criterion, are at levels of abundance and distribution that do not adversely affect the ecosystem

D2C3: Species groups and general habitat types exposed to risks from non-native species for descriptors 1 and 6 are in a proportion per species group and extent for each major habitat type assessed that does not adversely alter native species and habitat composition.

D2: The GES definition is placed at the descriptor level according to the data currently available for the assessment of the situation.

D2C1: Given the heterogeneity of the available data due to the lack of standardisation of methods, it is currently not possible to statistically assess the status of criterion D2C1 (decreasing trend in the number of new introductions). The definition of a quantitative threshold (number of newly introduced species) associated with the "minimum level" of ENI introduction compatible with good ecological status is currently not complete. The methodological standards relating to the D2C1 criterion for newly introduced non-native species will be specified following additional studies, as provided for in Ministerial Order 2019 on the definition of good ecological status of marine waters.