Extensive microphytobenthos mats of invasive Vaucheria aff. compacta and abiotic environmental factors influencing its abundance in Adventfjorden tidal flat, Svalbard

Arctic coastline ecosystems are affected by current sea level rise together with increasing anthropogenic and environmental physical and biogeochemical pressures. Changes in nutrient concentrations followed by changes in primary productivity and biodiversity are also connected with the growth of global trade, urbanization, and travel activity. All these anthropogenic activities create biotic homogenization. The occurrence of massive extensive mats of the yellow-green alga Vaucheria aff. compacta is a unique phenomenon in the High Arctic tidal flat ecosystem. The objective of this study was to outline which physicochemical conditions are connected with the massive presence of V. aff. compacta mats across the Adventfjorden tidal flat. The Adventfjorden tidal flat is a very dynamic system. Fine silt sediment (68% to 80%) dominates across the studied tidal flat. The sediment cover of V. aff. compacta mats was always very thin and felt-like coatings can grow out. Beneath the V. aff. compacta mats a second distinct layer of dead filaments were observed in the black and anoxic mud layer. V. aff. compacta area cover was positively correlated with water salinity, pH, temperature, and sediment Na and organic carbon content. In addition, potential abiotic factors related with the local distribution and abundance of V. aff. compacta showed positive correlations between area cover and N-nitrate and P-phosphate. N-nitrate concentration appears to significantly promote V. aff. compacta abundance. V. aff. compacta distribution and abundance in the Adventfjorden tidal flat is influenced by a wide spectrum of environmental and structural variables including anthropogenically induced micronutrients.