Influence of terrestrial inputs on Arctic planktonic community structure at eroding permafrost coasts

The Arctic is currently warming about four times faster than the global average. This increases permafrost thaw, and the supply of carbon, nutrients and sediment into the nearshore zones. However, it remains understudied how these changes influence planktonic community structure, that form the basis of the Arctic food web. Here, we investigated the interplay between seawater physical and chemical parameters and planktonic composition and abundance at Herschel Island (Canadian Arctic). In July 2022 and 2023, we sampled up to 2000 m along a retrogressive thawing slump-affected transect area, and along a non-slump-affected area. We found significantly higher turbidity and concentrations of particulate carbon and nitrogen, near the shore, and in the slump-affected transect, confirming increased input of terrestrial material in degrading permafrost coasts. Phytoplankton and microzooplankton abundances were higher in the non-slump affected transect than in slump affected transect. However, bacterial biomass did not differ significantly between the transects. Although diatoms groups of Pseudo-nitzchia delicatissima and Skeletonema costatum dominated the phytoplankton community in both transects, Dinobryon were only observed in slump-affected transect. Shannon-Weiner diversity index also confirmed a higher diversity in the non-slump affected transect. Our results show that permafrost thaw affects planktonic community composition and abundance. Higher slumping activity enhances input of carbon and nutrients, but light attenuation due to sediment input might be  negatively affecting phytoplankton productivity.

Presentation Preference: Oral

Primary Presenter: Gabriel Juma, Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (gabriel.juma@awi.de)

Authors:

Gabriel Juma, Alfred Wegener Institut Helmholtz Zentrum für Polar- und Meeresforschung  (gabriel.juma@awi.de)

Cedric Meunier, Alfred Wegener Institut Helmholtz Zentrum für Polar- und Meeresforschung  (cedric.meunier@awi.de)

Maarten Boersma, Alfred Wegener Institut Helmholtz Zentrum für Polar- und Meeresforschung  (maarten.boersma@awi.de)