Search Results (3)

When cyanobacterial phytoplankton form harmful cyanobacterial blooms (HCBs), the toxins they produce threaten freshwater ecosystems. Hydrogen peroxide is often used to control HCBs, but it is broadly toxic and dangerous to handle. Previously, we demonstrated that glucose addition to lake water could suppress the abundance of cyanobacteria. In this study, glucose was compared to hydrogen peroxide for the treatment of cyanobacterial phytoplankton communities. The six-week study was conducted in the large mesocosms facility at Grand Valley State University’s Annis Water Resources Institute in Michigan. To 1000 L of Muskegon Lake water, glucose was added at either 150 mg or 30 mg glucose/L. Hydrogen peroxide was added at 3 mg/L to two 1000 L mesocosms. And two mesocosms were left untreated as controls. Triplicate 100 mL samples were collected weekly from each mesocosm, which were then filtered and frozen at −80 °C for 16S rRNA amplicon sequencing. The 16S rRNA amplicon sequencing results revealed that hydrogen peroxide treatment quickly reduced the relative abundance of the cyanobacteria compared to the control mesocosms, but the cyanobacteria population returned over the course of the 6-week study. On the other hand, both glucose concentrations caused a rapid proliferation of multiple low abundance proteobacterial and bacteroidotal taxa resulting in notable increases in taxonomic richness over the duration of the study and reducing the relative abundance of cyanobacteria. Although hydrogen peroxide quickly suppressed the cyanobacteria, the population later returned to near starting levels. The glucose suppressed the cyanobacterial phytoplankton apparently by promoting competitive heterotrophic bacteria. Full article

Hypolimnetic hypoxia is expanding globally due to anthropogenic eutrophication and climate warming. Muskegon Lake, a Great Lakes estuary, experiences annually recurring hypoxia, impairing ecological, social, and economic benefits. Using high-frequency, time-series Muskegon Lake Observatory (MLO) data, we quantified the dynamics of hypoxia and developed a hypoxia severity index to estimate the spatiotemporal extent of hypoxia during 2011–2021. We also analyzed United States Geological Survey’s temperature and discharge data on the Muskegon River to explain the annual variability in the hypoxia severity index. Severe hypoxia occurred in warmer years with greater stratification, fewer wind mixing events, warmer winter river temperatures, and less winter and spring precipitation, as in 2012 and 2021. Conversely, milder hypoxia was prevalent in colder years with a later stratification onset, more mixing events, colder river temperatures, and more winter and spring precipitation, as in 2015 and 2019. Thus, knowledge of environmental conditions prior to the onset of stratification may be useful for predicting the potential severity of hypoxia for any year. While consistent multi-year trends in hypoxia were not discernible, our findings suggest that temperature and precipitation are major drivers of hypoxia and that as surface waters warm, it will lead to the further deoxygenation of Earth’s inland waters. Full article

The presence of both microplastics and per- and polyfluoroalkyl substances (PFAS) is ubiquitous in the environment. The ecological impacts associated with their presence are still poorly understood, however, these contaminants are extremely persistent. Although plastic in the environment can concentrate pollutants, factors such as the type of plastic and duration of environmental exposure as it relates to the degree of adsorption have received far less attention. To address these knowledge gaps, experiments were carried out that examined the interactions of PFAS and microplastics in the field and in a controlled environment. For field experiments, we measured the abundance of PFAS on different polymer types of microplastics that were deployed in a lake for 1 month and 3 months. Based on these results, a controlled experiment was conducted to assess the adsorption properties of microplastics in the absence of associated inorganic and organic matter. The adsorption of PFAS was much greater on the field-incubated plastic than what was observed in the laboratory with plastic and water alone, 24 to 259 times versus one-seventh to one-fourth times background levels. These results suggest that adsorption of PFAS by microplastics is greatly enhanced by the presence of inorganic and/or organic matter associated with these materials in the environment, and could present an environmental hazard for aquatic biota. Full article