Document Type

Thesis - University Access Only

Award Date

2000

Degree Name

Master of Science (MS)

Department / School

Agronomy

Abstract

Invertebrates are important in aquatic food chains. They form a crucial link between phytoplankton and aquatic macrophytes, and higher level consumers such as waterfowl. I hypothesized that high concentrations of nutrients in wetland water would lead to high invertebrate abundances through the transfer of nutrients and energy resources up the food chain. Three seasonal wetlands in agricultural landscapes of eastern South Dakota were sampled monthly from May through August during 1994 and 1995. Wetland water nitrate-N and orthophosphate concentrations were determined using a Hach DR2000 spectrophotometer. Aquatic invertebrates were sampled using activity traps placed midway in the water column for 24 hours. Nitrate-N -1 concentrations ranged from 0.0 to 0.2 mg L in 1994 and -1 from 0.0 to 0.2 mg L in 1995. Orthophosphate -1 concentrations ranged from 0.65 to 1.65 mg L in 1994 and -1 0.66 to 1.24 mg L in 1995. Ten taxa of invertebrates exhibited correlations with nutrients in the water column. Culicids (r=.72), copepods (r=.49) and Hydroporus spp. Of (aquatic beetles) (r=0.58) had significant positive correlations with nitrate-Nin the water column. Several genera of aquatic beetles (Acilius r=0.42, Hydaticus r=0.42, Hydroporus r=0.55, Celina r=0.54, Dytiscus r=0.45 and Hydrophilius r=0.47) and Rhynchobdellida (r=0.47) had significant positive correlations with orthophosphate in the water column. One genus of aquatic beetles (Agabus r=0.48) had a significant negative correlation with orthophosphate concentrations in the water column. Our results indicated that higher nutrient concentrations in the water column were generally followed by higher invertebrate abundances. This suggests that nutrient availability is an important link in wetland food webs. Increased nutrient availability could increase plant and phytoplankton production, and in turn cause a subsequent increase in primary consumers through higher food availability and better nutritional content. Additional research was conducted to determine the effects of land use on wetland ecosystems. Many of the wetlands in the Prairie Pothole Region(PPR) of Eastern South Dakota occur on privately owned land and are subject to disturbances from different land uses. The objectives of this study were to evaluate the effects of land use on invertebrate abundances in Prairie Pothole wetlands and to determine the correlation between wetland water, plant and soil nutrient concentrations and aquatic invertebrate abundances. Eleven seasonal wetlands located on three different land management systems (conventional and organic farming systems and a natural prairie setting) in Eastern South Dakota were sampled from May through August during the summer of 1998 and 1999. Wetland water orthophosphate and nitrate-N concentrations were determined using a Hach DR2000 spectrophotometer. Wetland invertebrates were sampled using a benthic corer and sorted using a magnesium sulfate floatation method. Two families (Daphnidae and Chironomidae) of invertebrates exhibited significant differences due to the conventional, organic and natural systems of land use during 1998 season. One family of invertebrates (Tubificidae) exhibited significant differences due to the conventional, organic and natural systems of land use during the 1999 season. Orthophosphate concentrations ranged from 0.01 to 1.71 - 1 - 1 mg L in 1998 and 0.01 to 1.49 mg L in 1999. Nitrate-N - 1 concentrations ranged from 0.0 to 1.8 mg L in 1998 and 0.1 - 1 to 1.5 mg L in 1999. Seven taxa of invertebrates exhibited significant correlations with orthophosphate in the water column. The highest r values were: Gyrinidae r=0.75, Helodidae r=0.58 and Daphnidae r=0.46. Results indicated that higher wetland water orthophosphate concentrations typically resulted in higher abundances of certain families of aquatic invertebrates. Since most invertebrates cannot aquire the necessary nutrients directly from the water column, nutrient transfer must occur by other means. Significant positive correlations were likely a result of food web dynamics.

Library of Congress Subject Headings

Aquatic invertebrates -- Prairie Pothole Region -- Nutrition
Wetlands -- South Dakota
Land use -- Environmental aspects -- South Dakota

Format

application/pdf

Number of Pages

112

Publisher

South Dakota State University

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