An 8-year time series of mesozooplankton fluxes in Kongsfjorden, Svalbard

Abstract

Abstract In Arctic regions the food availability for epi-pelagic fauna is strictly influenced by environmental stressors, such as solar radiation, ice cover, glacial and watershed runoffs. This study presents an 8-year time-series (2010–2018) of mesozooplankton collected from a moored automatic sediment trap in Kongsfjorden, Svalbard, at ~ 87m depth. The aim of this study is to observe the temporal variation in the abundance of epipelagic mesozooplankton species, collected as active flux (swimmers). Environmental stressors, including meteorological and hydrological datasets, are presented to evaluate the relative importance on the behavior of zooplankton populations. A principal component analysis (PCA) applied to the dataset revealed that the physical and chemical characteristics of seawater affected the mesozooplankton abundance and composition. Collectively, this result highlighted the role of the thermohaline characteristics of the water column on the Copepods behavior, and the correlation between siliceous phytoplankton and Amphipods. Overall, the zooplankton within inner Kongsfjorden did not show a clear seasonal trend, suggesting their high adaptivity to extreme environmental conditions. Although the swimmer fluxes have decreased from 2013 onwards, an increase in community diversity has nevertheless been observed, probably due to copepods decline and subsequent food availability. Despite the decreasing magnitude of the zooplanktonic community over time, we recorded the intrusion of subarctic boreal species, such as Limacina retroversa, since 2016. The uniqueness of this dataset is the continuous 8-year time series, which provide correlations between environmental and biological parameters in an understudied region. In a warming Kongsfjorden scenario, with the increase of submarine and watershed runoff, and the rapid Atlantification of the fjord, major changes in mesozooplankton communities are likely to be expected in the medium to long-term due to their adaptation to environmental changes and the introduction of alien species.