Dear Dana, and all others;
The type of research focused on what we might call "functional aspects of (benthic) biodiversity" has been, and is being, conducted for quite some time. This includes the role of benthivorous fish on the benthos (and vice versa), the role of benthic key species, and the role of the habitat structure(s) - exemplified by e.g. algal mats and hypoxia. The role of the invasive species has so far been poorly analysed, and mainly circumstantial evidence has been produced (and some experimental evidence, but not linking all levels of analysis: mechanistical aquarium tests; field manipulative experiments; field analysis - verification). As for e.g. Marenzelleria, I feel it has come to stay, yes, but we do not know if it will be as dominant as first feared. Even if it would have a high frequency of occurrence in sample units, that does not mean it dominates the functions, and there are even cases where the populations are on the decline after an initial (and typical in such cases) "overshoot" in abundance. The Gulf of Riga may prove to be such a case.
But the take-home message from this is that we need experimental evidence, and solid verification from critically designed field surveys.
Best regards,
Erik Bonsdorff
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