Benthic carbon processing in the sub-Antarctic Magellan Region: hotspots and coldspots of secondary production

Abstract Assessing benthic carbon stocks provides key insights into ecosystem functioning. We compiled macrozoobenthic data, including abundance, biomass, body mass, and environmental variables (e.g., chlorophyll-a (Chl-a), temperature, and total organic matter (TOM)), from 101 stations across the sub-Antarctic Chilean Patagonian Fjords and Channels between 1994 and 2010. Artificial neural networks were applied to estimate secondary production and productivity. The highest abundance and biomass were found in Beagle Channel and Bernardo O’Higgins National Park (BONP)/Kawésqar National Reserve (KNR), where mollusks accounted for the largest proportion of benthic carbon. Community production was highest values in BONP (~ 96.96 g C m − ² y − ¹), while the highest P/B ratios occurred in glacially influenced locations such as Gallegos Sound (~ 6.68 y − ¹), indicating rapid biomass turnover primarily contributed by arthropods and annelids. Depth and TOM were the strongest predictors of spatial patterns: production declined with depth, whereas elevated P/B ratios were associated with TOM-rich sediments, indicating efficient carbon recycling. These patterns reveal two contrasting benthic functional contexts: shallow, organic-rich fjords with high production, and deeper, glacially influenced systems with lower production but higher turnover. Mollusks contribute disproportionately to secondary production, arthropods drive biomass renewal, and annelids underpin sedimentary organic-matter processing. Together, these functional roles highlight the significance of different taxa within benthic communities in regional carbon cycling and offer essential context for aquaculture planning, conservation, and ecosystem-based management in sub-Antarctic marine environments.