Enhancing Urban Water Quality through Biological-Chemical Treatment: Aquatic Macroinvertebrate Community and Temporal Chlorophyll-a Response

Authors

Matthew Chaffee, University of Nebraska-LincolnFollow

First Advisor

Aaron Mittelstet

Date of this Version

12-2023

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agricultural and Biological Systems Engineering

Under the supervision of Professor Aaron Mittelstet

Lincoln, Nebraska, December 2023

Comments

Copyright 2023, Matthew Chaffee

Abstract

With a growing human population, urbanization is impeding a plethora of natural waterways. Of these, urban ponds play a vital role in nutrient sequestration, flood prevention, and habitat sanctuaries. However, nutrient loading can reduce habitat effectiveness and promote harmful algae blooms. To reduce internal nutrient loads, a biological-chemical treatment strategy consisting of floating treatment wetlands (FTWs) and lanthanum were applied to two urban retention ponds, Densmore and Wilderness Ridge Ponds. To measure effectiveness, chlorophyll-a samples were collected and correlated with Sentinel-2. A novel band algorithm termed 3BR1 produced a strong correlation (R² = 0.72) to physical chlorophyll-a samples and had a better correlation compared to traditional chlorophyll-a band algorithms. The derived relationship estimated temporal chlorophyll-a concentrations prior to treatment installation in 2019 throughout the treatment process in 2022. ANOVA showed Densmore Pond algae was effectively reduced upon one full month of treatment. Wilderness Ridge and two control ponds did not show any significant reductions in chlorophyll-a throughout the treatment process. Thereby, FTWs can be effective but may be hindered by pond and environmental characteristics. To build upon this, aquatic macroinvertebrate samples were collected at Densmore and Wilderness Ridge Ponds. These samples were classified into pollutant tolerance groups and the Shannon Diversity Index was calculated from July 2021 to October 2023. The Shannon Diversity Index at Densmore Pond increased throughout the treatment process while Wilderness Ridge Pond remained unchanged. In addition, macroinvertebrate samples were collected under the FTWs. The Wilderness Ridge Pond’s FTW showed a drastically different macroinvertebrate assemblage compared to Wilderness Ridge Pond itself. Densmore Pond’s FTW assemblage varied little from within the pond, indicating this habitat type was already present within the pond itself. Thereby, the treatment’s algae reduction capabilities enabled water column light penetration, fostering aquatic vegetation to take hold, and created new habitat and niches for new organisms to thrive within Densmore Pond.