Aquatic Insect Community Structure and Secondary Production in Coastal Wetland Ponds of the Copper River Delta, Alaska: Influence of Water Temperature and Macrophyte Community Structure

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Caldwell, Chantel
Alaska; Aquatic Insects; Coastal Wetlands; Macrophytes; Secondary Production; Entomology
thesis / dissertation description
The Copper River Delta (CRD), southcentral Alaska, is one of the world’s largest continuous coastal wetlands and is largely composed of sloughs, lakes, and ponds. Due to coastal topography the east side of the Copper River (East Delta) is disproportionately impacted by a cold continental air mass. Wetland communities of the CRD were also impacted by a 9.2 magnitude earthquake in 1964 that shifted the more coastal portion of the CRD from tidally influenced ponds to freshwater ponds.The West-East temperature gradient across the CRD coupled with landscape type (uplifted marsh (UM) and outwash plain (OP)) creates four regions (West-UM, West-OP, East-UM, and East-OP). The goal of this study was to assess the impact of water temperature, landscape type, and macrophyte community structure on aquatic insect community structure and secondary production. Mean water temperatures during the study were higher in uplifted marsh ponds than in outwash plain ponds. The warmer, geologically younger UM ponds were dominated by submerged macrophytes, while the colder, later successional OP ponds were dominated by long-lived perennial emergent macrophytes.Taxa richness was highest in West-UM ponds and lowest in East-OP ponds. West-UM ponds had the second highest aquatic insect densities of the regions, and relative abundance of Odonata, Hemiptera, Trichoptera, and Diptera each comprised 20-35% of the aquatic insectcommunities. Predator-engulfers, a functional feeding group (FFG) with significantly higher densities in West-UM ponds than in OP ponds, had three times higher annual secondaryproduction in West-UM ponds than in other regions. East-OP ponds had the lowest mean diversity and highest mean density of all four regions. Hemiptera relative abundance in East-OP ponds was 49.3% followed by Diptera relative abundance of 35.5%, all other remaining orders were below 11% relative abundance. Predator-piercers, an FFG composed mainly of hemipterans and coleopterans, had densities four times higher and annual secondary production rates two times higher in East-OP ponds than in other regions. Results from this study revealed significant differences in aquatic insect community structure and secondary production between the four regions of the CRD. These results have strong implications for the potential impacts of climate change in both early successional and late successional northern latitude coastal wetlands.