Observation of discarded appendicularian houses in the benthic and pelagic zones of Spitsbergen fjords using drop-camera imagery

This study documents previously unreported observations of abandoned Oikopleura vanhoeffeni (Chordata: Appendicularia: Oikopleuridae) houses accumulating on the seabed of various Spitsbergen fjords. The investigation utilized data from 253 video stations recorded during Arctic summer expeditions from 2015 to 2021. Notably, observations from 2021 revealed that O. vanhoeffeni houses were present both on the seafloor and in the pelagic zone, with densities reaching up to 973 structures m -2 , occasionally covering the entire surveyed seabed. According to existing literature, such densities could contribute up to 58 mg carbon m -2 . In regions of maximum house density, the water column contained significant mineral suspensions, which could potentially influence the rates of house occlusion, production, and sedimentation. This phenomenon underscores a potentially significant link between Arctic plankton and the intensification of meltwater runoff enriched with mineral suspensions, driven by the accelerating effects of climate change. Moreover, this observation may enhance our understanding of the carbon cycle in high-latitude marine ecosystems, such as the Spitsbergen fjords. Although short-lived, this occurrence may play an ecologically significant role for benthic communities and serves as a notable example of benthic-pelagic coupling, emphasizing its ecological significance.