Spatial and temporal variability of benthic community structure in high Arctic lagoons
Fraser, D.F. (2023). Spatial and temporal variability of benthic community structure in high Arctic lagoons. MSc Thesis. The University of Texas at Austin: Austin. 85 pp. https://dx.doi.org/10.26153/tsw/48588
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Document type: Dissertation
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| Abstract |
Shallow (<5 m) coastal lagoons of the Alaskan Arctic are highly dynamic environments that sustain benthic invertebrate communities critical to local food webs and sediment nutrient cycling. Invertebrate communities must cope with a variety of disturbances, including winter bottom-fast ice, spring freshwater inputs, and summer turbidity. From 2018 to 2022, quantitative benthic sampling during April, June, and August in four lagoons along 500 km of Alaskan Arctic coast have revealed depth-dependent spatial and temporal variations in benthic community structure. Multivariate analyses showed spatial variability was relegated to the deeper (> 2 m) stations of every lagoon, and all four lagoons possessed distinct assemblages (ANOSIM: R = 0.6955, p = 0.001) that were mostly driven by different polychaete species. Distance-based redundancy analysis (adjusted r² = 0.19) showed that these differences were mostly attributed to the static variables of longitude, depth, and sediment grain size. We observed an overall increase in deep station Shannon diversity (H`) and Margalef species richness (S) from east to west across the Beaufort Sea coast; the highest diversity occurred in Elson Lagoon (H` = 1.81 ± 0.07), the highest species richness in Simpson Lagoon (S = 2.78 ± 0.14), and the lowest diversity and richness in Jago Lagoon (H` = 0.58 ± 0.11, S = 1.06 ± 0.18). Seasonality of H`, S, and macrofaunal density was restricted to the highly perturbed shallow (< 2 m) stations of all lagoons while little to no seasonality was seen in the deeper stations of all lagoons, suggesting a more stable habitat that likely serves as the source populations for the annual recolonization of shallow benthic communities exposed to ice-related perturbations. A comparison of this study’s benthic abundance data with legacy data from the 1970’s showed no significant difference in infauna, suggesting these coastal ecosystems have not yet been irreversibly changed by regional climatic warming. However, the shift in species dominance to deposit-feeding polychaetes in Kaktovik Lagoon may reflect a response to increased organic matter deposition from marine or terrestrial sources. |
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