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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.

AbstractSalinization in freshwater ecosystems has become an increasingly prevalent issue. Past studies indicate that increased salinity levels in lakes can impact biota, stimulate internal nutrient loading, and prevent seasonal turnover, potentially resulting in impairment to the lake ecosystem. Salt retention in soils and groundwater causes elevated salt concentrations in fresh water long after road salt was applied. We examined salt retention and release in soils collected near the tributaries flowing into and out of a salt-impacted urban lake. We distributed each soil sample into plastic trays and exposed them to three treatments, conducted in series: (1) non salt-contaminated water as a conditioning rinse; (2) salt-contaminated water to mimic salt de-icer runoff; and (3) non salt-contaminated water to determine salt release. We measured retention of chloride from each soil sample based on how much chloride was measured in water draining the soil (effluent). We observed considerable variability among sites presumably because of soil heterogeneity, although overall the soils in our study area retained a modest amount of chloride (mean of ∼29 mg/L) from simulated salt runoff events, even at short exposure times (

Eutrophication is a major problem in lakes and rivers throughout the world. One such system is Lake Macatawa, located in West Michigan, which hydrologically connects to Lake Michigan. Lake Macatawa and its watershed suffer from excess phosphorus and sediment loads. The total maximum daily load for the lake calls for a total phosphorus (TP) reduction of 75%, which would reduce the water column total phosphorus concentration from 125 μg/L to 50 μg/L. Understanding how P moves through this landscape, into Lake Macatawa, and ultimately to Lake Michigan and the St. Lawrence Seaway, is critical to managing and controlling P runoff. A potentially significant source of P to Lake Macatawa occurs through agricultural tile drainage. Various best management practices (BMPs) have been implemented in the Macatawa watershed to reduce P loading, especially surface runoff, but their overall effectiveness has been limited. Electric arc furnace (EAF) slag, a waste product from the steel industry, can chemically bind P and has been used previously in agricultural settings. Three iron slag filters were installed at the end of agricultural tile lines in the Macatawa watershed and evaluated to assess their effectiveness in removing P, while also monitoring for the presence of potentially toxic chemicals leaching from the slag. After 1 year of slag filter performance, both SRP (soluble reactive phosphorus) and TP decreased in the tile drain effluent: percent reductions of soluble reactive phosphorus and TP ranged from 7.4% to 57.3% and 59.5–76.5%, respectively. Absolute concentrations of TP were reduced to between 100 and 329 μg/L, which still exceeds the 50 μg/L goal for Lake Macatawa. Concentrations of toxic metals, polycyclic aromatic hydrocarbons compounds, and cyanide all were at levels below drinking water standards. Our preliminary conclusions are that the installation of these filters should be targeted to areas where tile drain effluent P levels are very high (SRP > 250 μg/L) to obtain an optimal cost/benefit ratio. While they are not a panacea, when installed in combination with other BMPs (Best Management Practices), EAF slag filters may play an important localized role in reducing P to Lake Macatawa and farther downstream.

We evaluated whether sediment excavation improved water quality in a former (pre-European settlement) wetland complex that was a farm in the early 1900s and then later in the 1990s/early 2000s was allowed to naturally refill with water and became nutrient-rich ponds plagued by legacy phosphorus issues. Two ponds were recently restored via dewatering, excavation of the surface sediment, and hydrologic reconnection to an adjacent creek to re-establish a flow-through marsh. The removal of ~103,000 m3 of phosphorus-laden sediment and reconnection to the adjacent stream resulted in improved water quality, with a reduction in total phosphorus concentration from ~1000 μg/L to ~20 μg/L and a 40% reduction in specific conductivity in both former ponds. Soluble reactive phosphorus concentrations declined substantially in one pond, from ~720 μg/L to 3 μg/L, but not in another pond, which was partially dredged by the landowner prior to restoration. Additionally, phosphorus concentration in the downstream receiving water body also declined but to a much more modest degree. Sediment excavation was an effective restoration tool in this former agricultural system, but given the expense and potential impact on pre-existing biota, a full-system diagnosis, including cost, sediment characterization, and control of external nutrient loading, is recommended before its implementation elsewhere.

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.

Excessive anthropogenically-caused nutrient loading from both external and internal sources has promoted the growth of cyanobacteria in Lake Taihu from 2005 to 2014, suggesting increased production and release of cyanotoxins. In order to explain the spatial distribution and temporal variation of microcystins (MCs), the intracellular concentrations of MCs (MC-LR, -RR and -YR, L, R and Y are abbreviations of leucine, arginine and tyrosine) were monitored monthly from July 2013 to June 2014. Three MC variants are present simultaneously in Lake Taihu; the MC-LR and -RR variants were dominant (accounting for 40% and 39% of the total), followed by MC-YR (21%). However, MC-YR accounted for a higher proportion in colder months, especially in March. The highest concentrations of intracellular MCs were found in July and October when cyanobacteria cell density also reached the maximum. The average concentrations of MC-LR, -RR and -YR in July were 4.69, 4.23 and 2.01 μg/L, respectively. In terms of the entire lake, toxin concentrations in northern parts were significantly higher than the eastern part in summer, when MC concentrations were several times higher than the guideline value by WHO throughout much of Lake Taihu. Results from correlation and redundancy analysis (RDA) showed that total MCs, including all variants, were strongly and positively correlated with cyanobacteria cell density, water temperature, total phosphorus (TP) and pH, whereas each variant had different correlation coefficients with each of the considered environmental variables. MC-RR showed a stronger relationship with temperature, in contrast to MC-YR and -LR. Dissolved inorganic carbon (DIC) showed a negative relationship with each variant, suggesting that rising DIC concentrations may inhibit cyanobacterial growth and thereby reduce MC production in the future.

Periphyton communities have received relatively little attention in lake ecosystems. However, evidence is increasing that they play a key role in primary productivity, nutrient cycling, and food web interactions. This review summarizes those findings and places them in a conceptual framework to evaluate the functional importance of periphyton in lakes. The role of periphyton is conceptualized based on a spatial hierarchy. At the coarsest scale, landscape properties such as lake morphometry, influence the amount of available habitat for periphyton growth. Watershed-related properties, such as loading of dissolved organic matter, nutrients, and sediments influence light availability and hence periphyton productivity. At the finer scale of within the lake, both habitat availability and habitat type affect periphyton growth and abundance. In addition, periphyton and phytoplankton compete for available resources at the within-lake scale. Our review indicates that periphyton plays an important functional role in lake nutrient cycles and food webs, especially under such conditions as relatively shallow depths, nutrient-poor conditions, or high water-column transparency. We recommend more studies assessing periphyton function across a spectrum of lake morphometry and trophic conditions.

Drowned-river mouth lakes, transitional zones between a lake and an inflowing river, have unique physical and hydrological dynamics. However, our knowledge about these ecosystems and their phytoplankton communities is limited by data availability, especially how well they conform to conventional phytoplankton models, such as the Plankton Ecology Group (PEG). We sampled Mona Lake, MI, on a monthly basis between May 2002 and August 2003 to: i) describe phytoplankton community structure (species composition and functional groups) in three hydrologic zones (Great Lake-influenced, transitional, and lotic-influenced) and at four temporal scales (spring, summer, fall, and winter); and ii) assess whether the phytoplankton dynamics in Mona Lake can be explained by PEG. Distinct patterns in Mona Lake phytoplankton communities and functional groups were not evident among the three hydrologic zones, which can be explained, at least in part, by the horizontally well-mixed waters in this system. However, there was a strong seasonal change in phytoplankton composition and functional groups, with summer dominance by large filamentous cyanobacteria with aerotopes, nitrogen-fixing Nostocaleans, and diatoms. In general, seasonal changes were related to increasing levels of dissolved oxygen and pH in spring, total phosphorus and temperature in summer, and ammonia in fall. Phytoplankton dynamics in Mona Lake were partially explained by the PEG model; our observations revealed different fall (cyanobacteria and chlorophytes) and winter (chlorophytes and dinoflagellates) communities than predicted. Temporal influence resulted in distinct changes in phytoplankton dynamics, whereas the hydrologic influence tended to homogenize phytoplankton community structure in this drowned river-mouth lake. This seasonal change conformed relatively well to the PEG model, which might have predictive applications in the management (e.g., control of algal blooms) of the lake.

In order to reverse the damage to aquatic plant communities caused by multiple years of high water levels in Lake Okeechobee, Florida (U.S.), the Governing Board of the South Florida Water Management District (SFWMD) authorized a "managed recession" to substantially lower the surface elevation of the lake in spring 2000. The operation was intended to achieve lower water levels for at least 8 weeks during the summer growing season, and was predicted to result in a large-scale recovery of submerged vascular plants. We treated this operation as a whole ecosystem experiment, and assessed ecological responses using data from an existing network of water quality and submerged plant monitoring sites. As a result of large-scale discharges of water from the lake, coupled with losses to evaporation and to water supply deliveries to agriculture and other regional users, the lake surface elevation receded by approximately 1 m between April and June. Water depths in shoreline areas that historically supported submerged plant communities declined from near 1.5 m to below 0.5 m. Low water levels persisted for the entire summer. Despite shallow depths, the initial response (in June 2000) of submerged plants was very limited and water remained highly turbid (due at first to abiotic seston and later to phytoplankton blooms). Turbidity decreased in July and the biomass of plants increased. However, submerged plant biomass did not exceed levels observed during summer 1999 (when water depths were greater) until August. Furthermore, a vascular plant-dominated assemblage (Vallisnera, Potamogeton, and Hydrilla) that occurred in 1999 was replaced with a community of nearly 98% Chara spp. (a macro-alga) in 2000. Hence, the lake’s submerged plant community appeared to revert to an earlier successional stage despite what appeared to be better conditions for growth. To explain this unexpected response, we evaluated the impacts that Hurricane Irene may have had on the lake in the previous autumn. In mid-October 1999, this category 1 hurricane passed just to the south of the lake, with wind velocities over the lake surface reaching 90 km h-1 at their peak. Output from a three-dimensional hydrodynamic / sediment transport model indicates that during the storm, current velocities in surface waters of the lake increased from near 5 cm s-1 to as high as 100 cm s-1. These strong velocities were associated with large-scale uplifting and horizontal transport of fine-grained sediments from the lake bottom. Water quality data collected after the storm confirmed that the hurricane resulted in lake-wide nutrient and suspended solids concentrations far in excess of those previously documented for a 10-year data set. These conditions persisted through the winter months and may have negatively impacted plants that remained in the lake at the end of the 1999 growing season. The results demonstrate that in shallow lakes, unpredictable external forces, such as hurricanes, can play a major role in ecosystem dynamics. In regions where these events are common (e.g., the tropics and subtropics), consideration should be given to how they might affect long-term lake management programs.