Date of Award
Master of Science
Natural Resource Ecology and Management
Joseph E. Morris
Chapter 2 Abstract - ABIOTIC FACTORS INFLUENCE OF AQUATIC VEGETATION ABUNDANCE IN IOWA LAKES
In spite of the importance of aquatic vegetation to lakes, there are ongoing conflicts between the need to manage vegetation for multiple users of a lake and the need for aquatic vegetation for the aquatic biota. In 2007, a study was undertaken to assess the relationships between water quality and aquatic vegetation communities in 13 Iowa lakes. These lakes varied in location and fishery management protocols. The total number of emergent/floating aquatic vegetation species per lake varied from six to 14 species, while the total number of submerged aquatic vegetation species per lake varied from three to 11 species. Mean emergent/floating aquatic vegetation abundance and submerged aquatic vegetation were compared against physical-chemical parameters. There were four significant relationships between physical-chemical parameters (alkalinity, hardness, chlorophyll a, and temperature) and emergent/floating vegetation abundance and significant relationships between submerged aquatic vegetation and chlorophyll a, Secchi-depth, total suspended solids, and total Kjeldahl nitrogen. The lakes with the best values of physical-chemical indicators typically had higher submerged aquatic vegetation abundance, but not necessarily diversity. The nMDS plot shows relationships the lakes have with emergent/ floating vegetation and submerged aquatic vegetation species as well as abundance. The emergent/floating aquatic vegetation ordination indicates that lakes Meadow, Greenfield, Anita, and Mormon Trail share similar plant species. The submerged aquatic vegetation nMDS plot reiterates the strong negative relationship between Secchi-depth and chlorophyll a levels, and lakes that share these characteristics. Overall, each lake seemingly similar at first, has many unique characteristics, making it difficult to set up a comprehensive guideline for all Iowa lakes vegetation management practices. By using simple linear regression, Shannon diversity index, and nMDS plots, managers can start to understand similarities and differences among lakes with reference to aquatic vegetation and physical-chemical parameters.
Chapter 3 Abstract- LITTORAL INFLUENCES ON ZOOPLANKTON POPULATIONS AND JUVENILE BLUEGILLS IN IOWA LAKES
Aquatic vegetation helps maintain the overall integrity of aquatic ecosystems. Lakes with vegetation are characteristic of reduced chlorophyll concentrations, lower phytoplankton densities, and large-bodied cladocerans. Littoral zones with dense vegetation beds accommodate invertebrate communities that are richer in abundance and diversity compared to barren littoral zones. Two objectives of this research were to determine whether vegetated and non-vegetated littoral zones have similar zooplankton populations, and the role of the littoral zone upon juvenile bluegills food habits. Vegetation-loving cladocerans, e.g., Chydorus spp., were typically found in higher abundance in vegetated areas compared to open littoral and limentic zones, while limnetic zooplankton, Daphnia spp. was often found in higher concentrations in pelagic zone. Regardless of fish size (≤50mm and >50mm), prey selectivity was similar. However, different sampling periods (spring/summer vs. fall) showed different prey choices.
Ernst, Megan, "The role of aquatic vegetation in Iowa lakes" (2008). Graduate Theses and Dissertations. 11871.