| Summary: | The biological pressure represented by non-indigenous macroinvertebrate species (NIMS)
should be addressed in the implementation of EU Water Framework Directive as this can have
a direct impact on the ’naturalness’ of the invaded macroinvertebrate assemblage. The
biocontamination concept allows assessment of this deviation from naturalness, by
evaluation of abundance and disparity contamination of an assemblage. This study aimed to
assess the biocontamination of macroinvertebrate assemblages in Lithuanian rivers, thereby
revealing the most high-impact non-indigenous species, and to explore the relationship
between biocontamination and conventional metrics of ecological quality. Most of the
studied rivers appeared to be impacted by NIMS. The amphipods Pontogammarus
robustoides, Chelicorophium curvispinum and snail
Litoglyphus naticoides were revealed as high-impact NIMS for Lithuanian
lotic systems. Metrics of ecological quality which largely depend upon the richness of
indicator taxa, such as the biological monitoring working party (BMWP) score and
Ephemeroptera/Plecoptera/Trichoptera (EPT) taxa number, were negatively correlated with
biocontamination, implying they could provide unreliable ecological quality estimates when
NIMS are present. Routine macroinvertebrate water quality monitoring data are sufficient
for generation of the biocontamination assessment and thus can provide supplementary
information, with minimal extra expense or effort. We therefore recommend that
biocontamination assessment is included alongside established methods for gauging
biological and chemical water quality.
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