Biology Ph.D. Dissertations

Terrestrial Influences on the Macroinvertebrate Biodiversity of Temporary Wetlands

Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biological Sciences

First Advisor

Helen Michaels

Second Advisor

Enrique Gomezdelcampo (Committee Member)

Third Advisor

Jeff Miner (Committee Member)

Fourth Advisor

Karen Root (Committee Member)

Fifth Advisor

Amy Downing (Committee Member)

Abstract

Vernal pools are temporary wetlands and local-scale biodiversity hot spots for a variety of amphibians, macroinvertebrates, and plants because their seasonal drying prevents the establishment of predatory fish populations. Vernal pools are often of conservation concern because of the amphibian populations; however, the emphasis on these organisms often eclipses the macroinvertebrates, which are important predators, prey, and nutrient cyclers in wetlands and the surrounding habitat. Hydroperiod and water chemistry are thought to be the primary regulators of vernal pool macroinvertebrates, but the surrounding habitat also affects these organisms. Specifically, canopy cover and forest composition can alter the autochthonous and allochthonous carbon sources for wetland food webs. My research objectives were to understand how variations in these factors affect macroinvertebrate diversity and community composition. In 2009, I conducted a field survey of fifteen vernal pools that varied in area, depth, hydroperiod, canopy and surrounding land use. I measured several habitat conditions, assessed the biotic communities of these wetlands, and found that canopy cover influenced bottom-up productivity and macroinvertebrate diversity. I used the results of this study to determine how known macroinvertebrate communities respond to variation in canopy cover in mesocosm wetlands. The low canopy treatments sustained the highest macroinvertebrate abundance, family richness, and Shannon diversity, as greater algal productivity increased resources available to support the macroinvertebrate communities. I conducted a second mesocosm experiment to explore how variation in canopy cover (low or high) and litter species (oak, maple, or a mixture of the two litters) affect vernal pool macroinvertebrates. Macroinvertebrate abundance and family richness were greater under low canopy and with oak litter, but the effects of canopy often depended on litter species. Canopy limits the amount of light that reaches a wetland, but litter and its impact on dissolved organic carbon (DOC) limit light transmittance and producer communities. Because forest composition and structure are changing from anthropogenic activities, these results suggest they will also alter the food webs of vernal pools. However, as some organisms utilize pools considered to be low quality for macroinvertebrates, vernal pools should be protected in a variety of habitat contexts to preserve regional species diversity.

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