Data from: Predator exclusion and riverine input: Effects on sub-Arctic intertidal soft-bottom macrobenthos

Consumption significantly structures marine benthic communities, and understanding predator-prey interactions is crucial for determining the dynamics of these systems. Yet consumer effects in sub-Arctic regions, particularly at sites with riverine input, remain underexplored. This study investigated predator impact on macrobenthos abundance, biomass, and biodiversity at two intertidal sites with low and high freshwater influence. Moreover, microphytobenthos biomass and d13C and d15N stable isotope values of macrobenthos and different organic matter endmembers were assessed. A three-month predator-exclusion experiment, run in two consecutive years, revealed weak to moderate predator effects on macrobenthos abundance and biomass. Predator-exclusion effects were generally stronger at the more river-influenced site, while biodiversity remained unaffected by predator-exclusion and riverine input. Microphytobenthos biomass increased slightly with predator exclusion, indicating complex trophic interactions. Stable isotope analysis revealed limited assimilation of terrestrial organic matter by macrozoobenthos, suggesting that benthos is dependent on marine-derived carbon sources. These results suggest low predation pressure on macrobenthos at higher latitudes. The findings also indicate that riverine inputs potentially mitigate predator-mediated reductions in prey biomass through nutrient enrichment, as the latter leads to higher primary production and food availability, while direct utilization of terrestrial organic material seems to be of minor importance. This study underscores the importance of local environmental conditions in shaping predator-prey dynamics and highlights complex interplay between riverine inputs and the ecology of coastal ecosystems. The results contribute to understanding the interactions within sub-Arctic intertidal systems and indicate the need for future research to explore individual mechanisms and long-term effects of riverine-coastal interactions.