Marina 27 | Ramp Parking – a reminder that the Marina 27 parking lot is intended for the Marina Parking during business hours. If you have relatives or friends parking here and being picked up by boat please make sure they park in the upper lot across the street. The goal is to keep the lower parking lots available for customers at the Marina 27 restaurant.
Lake Trophic States
Trophic state is a scientific classification describing the biological productivity of a lake based on nutrient enrichment, algae growth, water clarity, and oxygen conditions. Natural lakes generally range from oligotrophic (low productivity and clear water) to eutrophic or hypereutrophic (high productivity, greater algae growth, lower clarity, and greater oxygen stress). Trophic state is not solely a water testing label; it is a lake condition indicator that helps guide long-term management of water quality, aquatic vegetation, fish habitat, and overall recreational usability.
We have re-joined the Lakes Missouri Volunteer Program (LMVP) for free annual water testing through the University of MO extension office. Ron DeCombes participated for years ending in 2022. That report shows the lake is Eutrophic, meaning high phosphorus levels. The assumption has not improved over the past 4 years, especially with no dredging. To lower phosphorus, we all need to be mindful of not over fertilizing our lawns especially if you DIY (lawn services are regulated) and especially along the Parkway. However, the runoff from all the fields around the lake are the big contributor, hence why we are working on silt mitigation planning.
That leaves us with removing silt through dredging. We now know dredging is more than keeping the cove depths; it is really a key aspect of managing water quality for recreational use. The LMVP report will be another tool in our belt, however it is published in April each year, so we have a bit of a wait on that information. We do have to test water back in the lake from the Silt Basins when dredging, so we are investigating doing some water testing for phosphates and nitrates in the process.
Impact of Dredging
Dredging a lake cove is a bit like stirring a giant, underwater tea bag; it significantly impacts the concentration and behavior of nutrients like phosphorus and nitrogen that have been sequestered in the sediment over time. While dredging is often intended to improve water quality by removing nutrient-rich “sludge,” the physical act of disturbing the silt can trigger several chemical and biological responses.
- Phosphorus (Phosphate) Release
Phosphorus is often the “limiting nutrient” in freshwater, meaning its availability controls how much algae can grow. In silt, phosphorus is typically bound to iron, aluminum, or calcium.
- The “Internal Loading” Risk: when you stir up silt, you expose buried phosphorus to the water column. If the water is anoxic (low oxygen), the chemical bonds holding phosphate to iron can break, causing a massive release of dissolved reactive phosphorus. More likely in the back of coves.
- Resuspension: even if the bonds don’t break, the physical movement of silt particles into the water column makes the phosphorus available to floating algae, potentially triggering a harmful algal bloom.
- Long-term Benefit: Once the dredging is complete and the nutrient-rich top layer is physically removed, the “internal loading” of phosphorus from the bottom is usually significantly reduced.
- Nitrogen Impact
Nitrogen behavior in silt is more complex because it exists in several forms (ammonium, nitrate, and organic nitrogen).
- Ammonium Release: silt is often rich in ammonium. Disturbing it can lead to a sudden spike in ammonium levels in the water, which can be toxic to fish and further fuel plant growth.
- Nitrification & Oxygen Demand: As ammonium is released, bacteria work to convert it into nitrate. This process (nitrification) consumes a lot of dissolved oxygen, which can stress or suffocate aquatic life in the cove.
- Turbidity: The “cloudiness” caused by suspended silt reduces light penetration, which might temporarily slow down the growth of rooted plants, even if nitrogen levels are high, but with our Zebra Mussels not much of a factor.