Date of Award

2011

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

The Great Alaska Earthquake of 1964 (magnitude 9.2) greatly altered the coastal landscape in southcentral Alaska and had particularly dramatic effects on the Copper River Delta (CRD), an ecologically and economically important area within the Chugach National Forest. The earthquake caused tectonic uplift (up to 3.5m) of the CRD coastal tidal marsh and transformed it into a perched freshwater marsh. Copper River Delta ponds, which are crucial habitat to a myriad of migrating songbirds, shorebirds, and waterfowl, are of particular interest to wildlife managers in the CRD and along the Pacific coasts of North, Central and South America. This study was conducted to characterize the general ecology of CRD ponds, with particular focus on aquatic insect communities.

Twelve ponds in two geomorphologic zones were studied to compare physicochemical characteristics, aquatic insect community structure and annual secondary production. Six ponds were in the Uplifted Marsh (UM), which was formed as a result of the tectonic uplift, and six ponds were in the Outwash Plain (OP), an area that was present before the earthquake and was relatively unaffected by tectonic activity. Uplifted Marsh and OP ponds were similar with respect to basic physicochemical parameters. Callicorixa vulnerata (Uhler 1861) (Hemiptera: Corixidae) was the numerically dominant non-dipteran taxon in 11 of the 12 study

ponds and represented 30-81% of all non-dipterans collected. Densities of the numerically dominant predators, Aeshna spp. (Odonata: Aeshnidae) and Enallagma spp. (Odonata: Coenagrionidae) were higher in OP ponds (<1-20/m2) compared to UM ponds (<1-4/m2), and production was 5X higher in OP than in UM ponds (507 vs. 97 mg AFDM/m2/yr). In contrast, secondary production of aquatic insect primary consumers such as Agrypnia spp. (Trichoptera: Phryganeidae) and Nemotaulius hostilis (Trichoptera: Limnephilidae), although found in relatively low densities (<1-3.3/m2), was almost 10X higher in UM ponds than in OP ponds (246 vs. 30 mg AFDM/m2/yr). Overall, annual secondary production of non-dipterans was greater in UM ponds than in OP ponds (3091 vs. 2205 mg AFDM/m2/yr). Results from this study indicate distinct differences in aquatic insect community structure, secondary production, and functional feeding group composition in UM and OP ponds. Creation of the UM ecosystem by tectonic disturbance increased the availability of suitable habitats for aquatic insects, particularly primary consumers, e.g., Trichoptera, and omnivores, e.g., C. vulnerata, which subsequently colonized UM ponds to take advantage of the newly abundant primary food resources (aquatic vegetation). In comparison, more mature OP ponds supported higher densities of aquatic insect predators, particularly Odonata, while supporting lower densities of Trichoptera and C. vulnerata.

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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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