Reducing HABs & Increasing Biodiversity in Lake Latonka

Lake Latonka is a 260-acre man-made freshwater lake in Mercer County, Pennsylvania. The lake serves as the centerpiece of the Lake Latonka community, and is used for fishing, boating, swimming, and a variety of recreation activities.

The watershed of Lake Latonka encompasses 8,000+ acres of rural land, which is comprised predominantly by agricultural type land uses (57%) and forest (27%) with low-density residential (12%) occurring along the immediate lake shores. The area is bordered by Ohio to the West and located midway between the cities of Erie and Pittsburgh.

The Lake, which was formed in 1965, has been studied and managed in some form since its formation with a record of consistent management and study since the mid-1990s. This work has included water quality monitoring, academic study of the sediment transport to the lake, herbicide and algaecide applications, and the development of generalized guidance for lake management. Additionally, some advanced management and restoration activities were implemented, including the installation of a community sewer system and maintenance dredging of the lake’s inlet area.

Despite these ongoing efforts, the lake has suffered from water quality impairments primarily due to excessive phosphorus from surrounding agricultural land that flows into the waterbody via stormwater runoff. These nutrients fuel algal growth and contribute to the increased deposition of sediment and nutrients at the lake bottom.

Over time, the increase in biological oxygen demand has led to anoxia (i.e. no oxygen) in the lake’s deep waters, which causes phosphorus to be ‘pumped’ from the sediments during the summer months. This process is termed ‘internal loading’ and leads to an acceleration of lake productivity that has fueled harmful algal blooms (HABs).

Recognizing the importance of the lake within the community, the Water Quality Committee (WQC) of Lake Latonka commissioned Princeton Hydro to perform an in-depth diagnostic/feasibility study and, based on the study’s findings, develop a comprehensive Lake Management Plan.

The diagnostic/feasibility study, in accordance with USEPA protocol, also analyzed background data; collected site specific water quality and fishery data; and computed the nutrient and hydrologic load. The study also included trophic calculations, the development of SMART (Specific, Measurable, Achievable, Relevant, and Time-based) goals, and the establishment of site-specific management recommendations.

In order to meet Lake Latonka’s water quality goals most expediently, Princeton Hydro recommended five primary management measures:

1. Phosphorus Loading Mitigation
2. Biomanipulation
3. Management of Submerged Aquatic Vegetation
4. Waterfowl Management
5. Regular Water Quality Monitoring and Testing.

Phosphorus Loading Mitigation

Although phosphorus is a nutrient utilized for plant growth, excessive phosphorus in waterbodies has problematic effects in that it speeds up weed production, reduces water quality, and can lead to HABs. One of the most sustainable means of controlling nuisance weed and algae proliferation is to control phosphorus inputs or reduce the availability of phosphorus for biological uptake and assimilation.

For Lake Latonka, Princeton Hydro recommended an alum treatment as a primary method for reducing internal phosphorus loading. Alum (aluminum sulfate) is a commonly used nutrient inactivation product that controls the internal recycling of phosphorus from the sediments of the lake bottom. On contact with water, the alum binds with the phosphorus so it can no longer be used as food by algae. On the bottom of the lake, the alum creates a barrier that prevents the phosphorus from releasing into the lake’s sediments under anoxia.

In addition, recommendations were made to address phosphorous loading from the larger agricultural watershed. These recommendations lead to the formation a Watershed Sub-Committee, which has been monitoring water quality and identifying nutrient-loading “hot spots.” As these areas are discovered, the community will work with local stakeholders to recommend watershed best management practices (BMPs) to reduce phosphorus and sediment loading at the source.

Biomanipulation

The diagnostic/feasibility study revealed a major change in Lake Latonka from a previous fishery study conducted in 2016: the establishment of gizzard shad. The gizzard shad, not found in any previous surveys, represented 29% of the total catch in the 2020 survey. These fish can, if present in significant densities, outcompete beneficial fish and aquatic species and alter the zooplankton population, which can lead to water quality impairment, HABs, and cyanobacteria.

Biomanipulation in lake management refers to the deliberate alteration of the lake’s ecosystem by adding or removing species. One of the main recommendations for Lake Latonka is to control the gizzard shad population by stocking the lake with hybrid striped bass (Morone saxatilis x Morone chrysops), which is a cross between striped bass and white bass that are not able to reproduce. The plan includes measures to bolster the walleye, largemouth bass, black crappie, and panfish populations to offer a robust recreational fishery. This “top down” approach to nutrient management serves as a complementary effort to the aforementioned phosphorus loading mitigation activities.

Management of Submerged Aquatic Vegetation

As phosphorus is reduced and water quality conditions improve, algae will diminish in abundance and water clarity will improve, and the shallow areas of the lake will become excellent habitat for increased growth of submerged aquatic vegetation (SAV).

SAV is a critical component of a healthy lake and important habitat for juvenile fish and invertebrates. Additionally, SAV serves to precipitate suspended solids and assimilates nutrients that may otherwise be taken up by algae for growth. Still, elevated levels of SAV may prove to hinder recreational use of the lake.

The Plan for Lake Latonka recommends regular SAV surveys in order to monitor densities, document species composition, and ensure proper management. As SAV increases, pragmatic, measured management will be recommended to maintain an optimal balance of plant growth while allowing for recreational lake access.

Waterfowl Management

Resident populations of Canada Goose (Branta canadensis) contribute acute sources of nitrogen, phosphorus, and bacteria to lakes via waste products.

Using loading coefficients derived from scientific literature, in combination with Canada geese population surveys, the team determined the approximate phosphorus load being contributed by the resident goose population each year is 88.6 lbs per year.

The Plan recommends a variety of deterrent/harassment actions as permitted through Federal and State agencies in order to minimize the resident population of these waterfowl.

Regular Water Quality Monitoring and Testing

The Management Plan also provided recommendations for routine water quality monitoring related to nutrient concentrations, algal types and densities, and safety for lake users. Lake monitoring helps track changes in water quality over time and is utilized to objectively assess the impacts of prescribed management measures. In this manner, monitoring can help to address potential issues before they become large problems.

Specifically, Princeton Hydro recommended growing season monitoring, which entails monitoring for five months each year, in order to build a lake water quality database for nutrients, in-situ measures, and plankton. Additionally, the team recommends robust contact testing at the beach and open water for E. coli sampling, fecal coliform, and cyanotoxins.

Simply put, there is more to lake management than weed and algae treatments alone. A customized plan acts as a “blueprint” that guides proactive, long-term lake management and care while remaining flexible enough to adapt to new challenges that may arise.

Our scientists, engineers, and Certified Lake Managers can assess the status of a waterbody and provide a holistic management plan that is based on the waterbody’s unique physical, hydrologic, chemical, and biological attributes. A management plan identifies water quality issues, determines the causes of those issues, and provides the guidance needed to correct the issues. The results are far more environmentally sustainable than simple (and often unnecessary) reactive weed and algae treatments.

During the Pennsylvania Lake Management Society Annual Conference held on March 2 & 3, Senior Aquatic Ecologist Michael Hartshorne gave a presentation about the the creation and implementation of the Lake Latonka Management Plan:

If you’re interested in reading more on the topic of lake management, click here:

• Lake and Pond Management
• Lake Restoration
• Natural Resource Management