Cyanobacterial Harmful Algal Bloom Ecology and Cyanotoxins in the Eutrophic Lake Winnebago-Green Bay Water System

Abstract

Cyanobacterial harmful algal blooms (cyanoHABs) are frequently observed in water bodies used for recreation and drinking water production and can be detrimental to humans, animals, and general water quality. CyanoHABs are natural occurrences, but human activities such as agriculture, land use change, and runoff from urban and rural landscapes can promote and accelerate their expansion. The blooms are aesthetically unpleasing scums and can be laden with toxins (cyanotoxins) and toxic or otherwise bioactive peptides (TBPs) that can be harmful to humans and animals. Despite the vast research on cyanoHABs, cyanotoxin and TBP diversity and dynamics within a water column are not well studied. Furthermore, the variability in lake cyanotoxin and TBP concentrations is not fully understood at time-scales relevant to drinking water production. There is a great need for information about cyanoHABs and their toxins that may pose recreational risk to swimmers, particularly children. To begin to assess the temporal variability of cyanotoxins and TBPs, Chapter 2 sought to use a proven technology, an automated water sampler, deployed to a water quality-monitoring buoy, to achieve a high temporal resolution sampling strategy for cyanotoxins and their associated pigments in a eutrophic lake. Chapter 3 sought to analyze environmental variables that may be associated with cyanotoxin and TBP blooms from multiple depths (surface water to bottom waters). Cyanobacteria have the ability to move throughout the water column in response to light or nutrient availability, however many sampling strategies focus on a singular depth. Chapter 4 describes the first spatial assessment of cyanotoxins and TBPs in Green Bay over a two-year period and sought to characterize a cyanotoxin gradient that follows the spatial trophic gradient. There are many accounts of toxin-producing blooms in the Laurentian Great Lakes. Surprisingly, there is a lack of information on cyanotoxins in Green Bay, a highly productive region in Lake Michigan. This dissertation seeks to describe the temporal and spatial variability of cyanotoxins and TBPs in two connected water bodies that are extremely important as drinking water and recreation resources in Wisconsin. The resulting work provides important insights into less studied, but frequently TBPs in drinking water and recreational waters. Cyanotoxin and TBP sampling was paired with in situ fluorometers, a common tool used for monitoring cyanoHABs, to assess the variability of pigments and cyanotoxins.