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Chaetognatha are highly-effective predatory components of the marine planktonic assemblages. Many species exhibit disjunct biogeographical distributions throughout the global ocean, and thus serve as sentinel species for examining climate-driven changes in ocean circulation on zooplankton species, communities, and food webs. Of particular interest are ecological changes in the Arctic, a region being drastically affected by climate change. In this study, a 650 base-pair region of the mitochondrial cytochrome oxidase I (mtCOI) gene was sequenced for 131 individuals for the chaetognath Eukrohnia hamata collected from diverse regions throughout the Arctic. DNA sequence analysis was done to characterize population genetic diversity and structure, phylogeography (i.e., geographic distribution of genetic lineages within species), and connectivity among regional populations. High haplotype diversity (Hd) and significant (p <0.02) negative values for Fu’s and Li’s F statistic imply that E. hamata is undergoing population expansion.. Patterns and pathways of population connectivity examined to test several migration hypotheses revealed that pan-Arctic population connectivity followed the primary ocean currents. The reliance of this ecologically important zooplankton species on Arctic Ocean currents has implications for future warming conditions, which have the potential to modify these currents, resulting in altered biogeographical distributions and population connectivity of Arctic zooplankton. 

Suspension-feeding mollusks (e.g., bivalves) play a key role in improving the water quality of coastal environments by filtering out suspended matter from the water column. Microplastics are becoming ubiquitous in the marine environment, so it is important to understand if these particles affect feeding processes of bivalves. Additionally, previous studies regarding the impact of microplastic on bivalve physiology have not independently tested for the effects of surfactants which are often added to commercially available plastic particles to prevent aggregation. We measured the clearance rate of mussels (Mytilus edulis) exposed to one type of microplastic and three common surfactants. Mussels were given a dose of microalgal food (1 x 104 cells/mL) and 10-m polystyrene spheres (Polybead; 1 x 104 beads/mL). Experimental treatments tested were washed microspheres and microspheres coated with each of the following surfactants at a concentration of 2mg/L: triton X-100, benzalkonium chloride, and sodium dodecyl sulfate. These surfactants are nonionic, cationic, and anionic, respectively. Control mussels were given a microalgal diet only (2 x 104 cells/mL). Each mussel was placed in an individual 1-L chamber and exposed to one of the aforementioned treatments. Water samples were taken at the start of the experiment (t=0) and then every 10 minutes for 30 minutes to determine clearance rates. Particle concentrations were measured using an electronic particle counter (Coulter Counter) at an appropriate size range for the algae and microspheres. Our results indicate that microspheres with or without surfactant had no effect on clearance rates of mussel compared to those of the controls. Further, our research suggests that the use of polystyrene microspheres in future experiments without initial washing does not affect the clearance rate of mussels.