Figure 3 - uploaded by Victor F. Medina
Content may be subject to copyright.
Stratification in a lake, found typically in the summer. Solid line indicates temperature trend while dashed line represents DO. The red region is considered the epilimnion, green thermocline/metalimnion, and blue the hypolimnion defined by the sharp temperature changes/differences between the regions.
Source publication
Koontz Lake is located in northern Indiana. The lake has had problems with eutrophication, harmful algae, invasive plants, and shallowing due to accumulation of sediment and muck. A study was conducted to assist in evaluating between two ecological restorative options under consideration: aeration and dredging. In this report, both approaches are d...
Contexts in source publication
Context 1
... stratification refers to a condition in which a physical gradient, such as temperature, serves to limit or restrict mixing in the lake. Stratification commonly occurs in summer when solar heating at the surface creates a high temperature region called the epilimnion ( Figure 3). Cooler, denser water is found with depth in the hypolimnion. ...
Context 2
... Lake, like most lakes in the U.S. Midwest, undergoes this stratification pattern. DO levels are closely linked to thermal stratification where the persistence of a thermocline inhibits the atmospheric diffusion of oxygen into the hypolimnion (Figure 3). Furthermore, light-harvesting autotrophs such as phytoplankton release oxygen at or above the thermocline where sunlight is readily available, contributing to a greater oxygen pool in surface waters. ...
Context 3
... natural aeration in lakes tends to be largely at or near the surface (via diffusion, turbulence/mixing, and photosynthetic inputs as mentioned above). Consequently, the near surface tends to have the highest oxygen concentrations (Figure 3). Wind and current mixing can keep oxygen levels relatively high for depth of 1 meter (m) or so, but at increasing depth oxygen diffusion can become more limited, particularly if the lake is highly stratified. ...
Similar publications
Coastal communities are performing at a level that is worse than the national average, across a number of key indicators. Despite this, they are located close to unique natural resources, which underpin the potential for generating good jobs and meeting local needs, while also protecting the marine environment. The New Economic Foundation’s Blue Ne...
Citations
... Remediation techniques are being developed to treat eutrophic conditions in polluted estuaries around the world, with approaches including environmental dredging, enhanced circulation, and aeration [5,[9][10][11]. Aeration has been proposed as a less expensive tool compared to dredging for reducing organic sediments and hypoxia [12]. It mixes the water column, increases dissolved oxygen (DO) concentrations and accelerates aerobic decomposition of organic matter [13][14][15]. ...
... In contrast, the cost of environmental dredging is $50-75 USD per cubic meter (i.e., $200,000 for~4,000 m 3 of muck from the same canal). Artificial aeration has been used in lakes and aquaculture ponds to enhance water quality, while little in situ data is available to inform predictions of ecosystem outcomes for estuaries undergoing aeration [12,[14][15][16][17][18][19]. Those freshwater studies focus on chemical reactions and microbial processes [14,[16][17][18][19]. ...
Fine-grained organic-rich sediments (FGORS) are accumulating in estuaries worldwide, with multi-faceted negative ecosystem impacts. A pilot experiment was carried out in a residential canal of the Indian River Lagoon estuary (IRL, Florida, USA) using an aeration treatment intended to mitigate the harmful ecological effects of organic-rich sediment pollution. Planktonic and benthic communities were monitored, and environmental data collected throughout the aeration process. Results were compared against control conditions to evaluate the efficacy of aeration in the mitigation of FGORS. During the aeration process, hurricane Irma impacted the study area, bringing heavy rainfall and spawning a brown tide event (Aureoumbra lagunensis). The overall thickness and volume of FGORS, and the organic content of surface sediments did not change during the aeration treatment. Dissolved oxygen was higher and ammonium concentrations were lower in aeration canal bottom water compared to the control canal. During treatment, aeration did facilitate benthic animal life when temperatures dropped below 25°C, likely due to water column mixing and the increased capacity of water to hold dissolved gasses. In general, aeration did not significantly change the planktonic community composition relative to the control canal, but, during the post-bloom period, aeration helped to weaken the brown tide and phytoplankton densities were 35-50% lower for A. lagunensis in aeration canal surface water compared to the control canal. Aeration has important management applications and may be useful for mitigating algal blooms in flow-restricted areas and promoting benthic communities in cooler environments.
... The capacity of water to hold oxygen is strongly associated with temperature [46]. The average initial temperature of all pretreatment mesocosms was 30.3 ± 0.08 (SEM) • C (n = 12) ( Figure 3B). ...
... The capacity of water to hold oxygen is strongly associated with temperature [46]. The average initial temperature of all pretreatment mesocosms was 30.3 ± 0.08 (SEM) °C (n = 12) ( Figure 3B). ...
A 72 h small-scale trial was conducted in enclosed mesocosms in the Lake Okeechobee waterway to evaluate the effectiveness of a USEPA-registered peroxide-based algaecide (formulated as sodium carbonate peroxyhydrate) for controlling a natural cyanobacteria population. Mesocosms were initially subjected to either no algaecide or the maximum label rate of 10 mg H2O2·L−1. A subset of mesocosms were then subjected to a sequential application of 5 mg H2O2·L−1 at 48 h after initial treatment. Following application, peroxide concentrations rapidly decreased and were undetectable by 48 h. At 24 h after treatment, significant decreases in all biomass indicators were observed (compared to untreated mesocosms), including extracted chlorophyll a, microscopic counts (total phytoplankton and total cyanobacteria), and cyanobacteria-specific 16S rRNA gene copies by over 71%. Although peroxide treatment reduced cyanobacteria biomass, there was no change in overall community structure and the remaining population was still dominated by cyanobacteria (>90%). After 48 h exposure, some biomass recovered in single application mesocosms resulting in only a 32–45% reduction in biomass. Repeated peroxide dosing resulted in the greatest efficacy, which had a sustained (60–91%) decrease in all biomass indicators for the entire study. While a single application of the peroxide was effective in the first 24 h, a sequential treatment is likely necessary to sustain efficacy when using this approach to manage cyanobacteria in the field. Results of this study support that this peroxide-based algaecide is a strong candidate to continue with scalable field trials to assess its potential future utility for operational management programs in the Lake Okeechobee waterway.
... • Formation of cyanobacterial/algal blooms, which can negatively impact human health, pets, and livestock. Medina et al. (2018B) provides a detailed discussion of nutrients (particularly phosphorus) and methods to address them. ...
This technical report (TR) details the results of a water quality/environmental management (WQ/EM) survey that was provided to U.S. Army Corps of Engineers (USACE) districts and divisions. The WQ/EM survey found that flood risk management was the most important congressionally authorized purpose, and was the highest funded activity. These results were followed by water quality, navigation, and recreation for importance. Agricultural impacts (i.e., nutrients, erosion, and pesticides) were the most critical upstream factors affecting WQ/EM. Critical reservoir factors were fisheries and algal blooms. In most cases, the results showed that there were very broad sets of WQ/EM purposes, factors, and issues. Limited resources in terms of funds and personnel will have to be applied to maximize positive benefits.
