MEPS 505:145-159 (2014)  -  DOI: https://doi.org/10.3354/meps10756

ABSTRACT: The spread of the sibling polychaete species Marenzelleria neglecta, M. viridis, and M. arctia in the Baltic since the early 1980s has been accompanied by various effects on the biogeochemistry of bioturbated sediments. Their influence on benthic nutrient fluxes (NH₄⁺, NO₃^- PO₄^3-) and oxygen uptake was examined in a laboratory experiment. Confirming a previous experiment, M. neglecta and M. viridis are more similar to each other with respect to their direct and indirect ecosystem function than to M. arctia. In contrast to the predominantly non-local transport mode of the deep-burrowing species M. viridis (solute transport coefficient α = 284.1 yr^-1) and M. neglecta (α = 277.1 yr^-1) in the sediment, the solute transport mode of M. arctia is more diffusive in character (11.8-fold enhanced diffusivity and α = 4.3 yr^-1). While the release of ammonium and phosphate, as well as the total oxygen uptake (TOU) of the sediment, was stimulated by the presence of all polychaetes, the fluxes (NH₄⁺, PO₄^3-, TOU) in cores colonized with M. viridis and M. neglecta were substantially higher than those of M. arctia. The presence of M. arctia had only slight stimulatory effects on nitrification, whereas M. neglecta and M. viridis enhanced nitrification. This suggests negligible stimulation of denitrification for M. arctia and leaves the source of ammonium in M. neglecta and M. viridis unresolved. Consequently, M. viridis and M. neglecta may affect eutrophication-related benthic fluxes considerably more than M. arctia, and a functional grouping of all 3 sibling species in terms of bioirrigation is not reasonable.

KEY WORDS: M. viridis · M. neglecta · M. arctia · Solute transport · Ammonium · Nitrate · Phosphate · Functional diversity