Title
Biological Productivity in Arctic Lagoons: Pilot Study to Assess Diversity, Abundance, and Interannual Dynamics of Zooplankton Populations
Author(s)
Alexei Pinchuk; Martin Robards; Kevin Fraley
Published
2020
Abstract
Eight coastal lagoons in and around Cape Krusenstern National Monument and Cape Thompson, Alaska were sampled for zooplankton diversity and abundance during 2017-2018 field visits by Wildlife Conservation Society crews. Water quality and chemistry were also assessed and related to zooplankton findings. Zooplankton from 75 samples were sorted taxonomically and counted in the laboratory by Alexei Pinchuk at the University of Alaska, Fairbanks. Results showed that Arctic coastal lagoons support dense herbivorous calanoid copepod populations suggesting high levels of pelagic production. Zooplankton composition, abundance and biomass varied between geomorphologically similar lagoons, creating drastically different feeding environments for pelagic predators. However, the composition within lagoons was remarkably consistent even across decades, when compared with historical studies. Based on these findings, it is likely that lagoons act as a portfolio of diverse rearing and feeding habitats for planktivorous invertebrates and fish to utilize. The high inter-lagoon variation in zooplankton composition, yet stable intra-lagoon composition over years undoubtedly shapes fish life history strategies and facilitates fish population bet-hedging to ensure successful recruitment and overall population health. Thus, these lagoons are undoubtedly integral to the population health of important subsistence fishes that inhabit them (e.g.s, whitefish and salmon species). Given the diverse nature of lagoon zooplankton assemblages, accelerating anthropogenic or climate change-driven effects in the region such as coastal erosion, permafrost thawing, or infrastructure development could upset the habitat conditions that drive species composition. This could potentially cause homogenization of zooplankton assemblages among lagoons and result in a lack of diverse prey options for subsistence fish species, thus decreasing fish population bet-hedging ability. Recommended follow-on work includes investigating the “seeding” of lagoons in early spring to answer the question of where zooplankton originate from, and why this differs across lagoons. It is likely that lagoons which freeze to the bottom during winter are places where species with resting (dormant) eggs thrive, while the lagoons with ice free bottom water provide refugia for euryhaline species.
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