Date of Award

8-2013

Degree Type

Thesis

Degree Name

Biology (M.S.)

Department

Biology

Abstract

Land use change from forest to agriculture can alter the physical, chemical, and biological integrity of stream ecosystems. The objective in this study was to use macroinvertebrate community structure and function, physicochemical measurements, and watershed land cover type to assess stream ecosystem health in response to the effects of agriculture and predicted changes in temperature regime due to climate change. I used key biotic indices include the % Ephemeroptera, Plecoptera, and Trichoptera (EPT), taxa richness, total abundance, and Shannon’s diversity to make a comparison of six agriculturally impacted tributaries in the Muskegon River Watershed located in Michigan, USA. The stream surrounded by the most agriculture, Brooks Creek, had a relatively high Richards-Baker flashiness value and low macroinvertebrate abundance. Diversity and %EPT were highest in Mosquito Creek, which was surrounded by less agriculture and had a low flashiness index. The other streams had comparable biotic indices intermediate between Brooks and Mosquito Creeks. Chironomidae represented the most abundant taxa for all streams. Results indicate that there were no major differences between the low and high agriculturally impacted streams, with the exception of Mosquito and Brooks Creek. Although not tested experimentally, the patterns in land use suggest that even though some of the impacted watersheds contained notable agriculture, the presence of generally intact riparian zones has maintained relatively clean water and high quality aquatic insect communities. How close these stream communities are to potentially shifting into an alternative and lower quality state is less certain. This study suggests that there is a lack of existing information on the potential response of macroinvertebrates to warming. I also used the temperature tolerances from Huff et al. (2004) and climate forecasts from Wiley et al. (2010) to make general predictions on future responses of the macroinvertebrates in the Muskegon River Watershed. In all stream sites the increase in future temperatures would likely cause certain temperature tolerant taxa to increase like the tricopteran Helicopsyche, temperature intolerant taxa to decrease like the dipteran Hexatoma, or experience no change. These results show that climate change will alter abundance of certain macroinvertebrate species, which can lead to variation in the community structure and food web.

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