Sessile invertebrate settlement in Kongsfjorden, Svalbard, observed with Camera To Analyze Invertebrates (2023-2025)

Settlement, the transition from a pelagic larva to a benthic juvenile, is a critical step in the life-history of benthic invertebrates, yet it is severely understudied. We used CATAIN (CAmera To Analyze INvertebrates) to track daily settlement and post-settlement mortality patterns in of a fouling community in Kongsfjorden, Svalbard (Arctic Ocean). The camera recorded images every 24 hours, so that newly-arrived settlers and organisms disappearing through mortality could be tracked over nearly 2 years. Spirorbids settled over the winter and had low mortality until spring, when other taxa settled and nearly all spirorbids disappeared. Bryozoans including Lichenopora sp. settled during spring-summer and had very low post-settlement mortality, counter to traditional models. The barnacle, Semibalanus balanoides was the most common taxon on CATAIN. This species had a very narrow settlement window in June 2023 and 2024, with large peaks in settlement that coincided with spikes in temperature, likely due to being advected in fronts. By understanding settlement and post-settlement processes, we can create a mechanistic understanding of how environmental factors influence Arctic organisms and better predict the consequences of climate change.