Around the world, freshwater lakes are increasingly suffering from harmful algal blooms (HABs) as a result of anthropogenic eutrophication. Muskegon Lake (Muskegon, Michigan, USA), a drowned river mouth, Great Lakes estuary, was declared an Area of Concern by the Environmental Protection Agency in 1987 with nuisance algal blooms cited as a beneficial-use impairment. The objective of this study was to quantify changes in HAB prevalence and assemblage composition in Muskegon Lake over 14 y (2003-2016) and explore the environmental factors potentially driving the changes. We performed univariate and multivariate analyses on long-term monitoring data, including environmental and phytoplankton data, to understand their relationships and temporal variation. Using linear regressions, we assessed changes in environmental variables over time and relationships between cyanobacteria biovolume and environmental variables. We used non-metric multidimensional scaling to visualize variation in annual cyanobacteria assemblage composition and association with environmental variables. Analyses revealed that, despite generally rising water temperatures, which would be expected to increase HABs, a reduction in nutrient concentrations caused by restoration efforts has likely led to substantial decreases in HAB abundance over time. Additionally, HAB assemblage composition appears to be driven by temperature and nutrient form and amount, with Microcystis (Lemmermann, 1907) often dominating. HABs in freshwater bodies should be closely monitored into the future as we enter an era of uncertain climatic conditions.

Rising atmospheric carbon dioxide levels are impacting global temperatures, ecological systems, and human societies. Natural carbon sequestration through the conservation of soil and native ecosystems may slow or reduce the amount of CO₂ in the atmosphere, and thus slow or mitigate the rate of global warming. Most of the research investigating carbon sequestration in natural systems occurs in forested ecosystems, however rare ecosystems such as coastal plain marshes and wet-mesic sand prairie collectively may serve as significant carbon sinks. Our objectives were to measure and assess the importance of carbon sequestration in three rare ecosystems (oak-pine barrens, coastal plain marsh, and wet-mesic sand prairie) in western Lower Michigan. We measured carbon in standing vegetation, dead organic matter, and soils within each ecosystem and adjacent encroaching forested areas. Driven by tree carbon, total carbon stocks in encroaching areas were greater than in intact rare ecosystems. Soil organic carbon was greater in all intact ecosystems, though only significantly so in coastal plain marsh. Principal components analysis explained 72% of the variation and revealed differences between intact ecosystems and their encroaching areas. Linear models using the ratio of red to green light reflectance successfully predicted SOC in intact coastal plain marsh and wet-mesic sand prairie. Our results infer the importance of these rare ecosystems in sequestering carbon in soils and support the need to establish federal or state management practices for the conservation of these systems.

Predicted climate-induced changes in the Great Lakes include increased variability in water levels, which may shift periphyton habitat. Our goal was to determine the impacts of water level changes in Lake Superior on the periphyton community assemblages in the Keweenaw Peninsula with different surface geology. At three sites, we identified periphyton assemblages as a function of depth, determined surface area of periphyton habitat using high resolution bathymetry, and estimated the impact of water level changes in Lake Superior on periphyton habitat. Our results suggest that substrate geology influences periphyton community assemblages in the Keweenaw Peninsula. Using predicted changes in water levels, we found that a decrease in levels of 0.63 m resulted in a loss of available surface area for periphyton habitat by 600 to 3000 m² per 100 m of shoreline with slopes ranging 2 to 9°. If water levels rise, the surface area of substrate will increase by 150 to 370 m² per 100 m of shoreline, as the slopes above the lake levels are steeper (8–20°). Since periphyton communities vary per site, changes in the surface area of the substrate will likely result in a shift in species composition, which could alter the structure of aquatic food webs and ecological processes.

Logistics often limit the number of field-based labs that include different types of ecosystems. Moreover, few lab classes allow students the opportunity to measure ecosystem-level changes. This article describes an activity appropriate for high school biology or introductory collegiate biology courses, where bottle biology can provide an opportunity for students to measure differences in temperature and humidity that result with different types of vegetation. This approach allows students to develop an understanding of how ecosystems transfer energy and cycle water, as well as the implications of land use change, such as timber harvest or grassland restoration, on regional climate.