The Lakes
Lake glossary
The words we use on the lake, in plain English. Jump to a letter or read top to bottom.
A
Algal bloom
A bloom is a rapid increase in algae — the tiny plants that live in the water. Some blooms are harmless and pass with a cold front; others are made of cyanobacteria and can produce toxins. Blooms are most common in warm, sunny stretches when the lake is loaded with nutrients.
Why it matters to the lake: * A bloom is the loudest, most visible sign that the nutrient
Association (we say "the Association")
The volunteer-run group — the Koonz & Beaulieu Lake Association — that stewards both lakes: monitoring water quality, organizing events, and working with the DNR on issues like weeds and invasive species.
Why it matters to the lake: * The Association is how a few hundred neighbors turn into one
C
Chlorophyll-a (we say "chl-a")
Chlorophyll-a is the green pigment algae use to make food from sunlight. Labs measure it in water samples as a proxy for how much algae is currently in the water — higher numbers mean more algae.
Why it matters to the lake: * It's our algae "thermometer" — the number behind the
Clarity (water clarity)
Clarity is how far you can "see" into the water — how deep light penetrates before the water gets milky or brown. We measure it with a Secchi disk; a deeper reading means clearer water.
Why it matters to the lake: * Clear water is what makes the lake a lake — and the first
D
Die-off
A die-off is when an algal bloom crashes: the algae die, sink, and decompose. The surface may clear, but the decomposing material can drop dissolved oxygen and leave an odor — sometimes a week or two after the bloom itself faded.
Why it matters to the lake: * A "quiet" week after a bloom can still be a stressful week
Dissolved oxygen (DO)
Dissolved oxygen is the oxygen dissolved in the water that fish, insects, and plants breathe. It's replenished by wind, waves, and plants' photosynthesis, and it's lowest on warm, still, stratified summer nights.
Why it matters to the lake: * Low DO is how a lake stresses its fish — usually in deep,
E
Eutrophication
Eutrophication is the slow enrichment of a lake with nutrients (mainly phosphorus and nitrogen). Over years, it drives more algae growth, muddier water, and thicker weed beds. "Oligotrophic" (nutrient-poor), "mesotrophic" (moderate), and "eutrophic" (nutrient-rich) describe where a lake sits on that spectrum.
Why it matters to the lake: * It's the long game we're playing: every storm that washes
H
Hypoxia
Hypoxia is a condition where dissolved oxygen in the water drops so low (generally below 2 mg/L) that fish and other aquatic life can't survive in that zone. In stratified summer lakes it usually hits the deep water first.
Why it matters to the lake: * Hypoxia in deep water is how a lake quietly loses its fish
N
Native plants
Native plants are species that evolved in the region and are part of the lake's natural community — like the cattails and arrowheads in a healthy shoreline. "Invasive" species arrived later, outcompete natives, and often take over.
Why it matters to the lake: * Native plants hold shorelines and feed local wildlife —
Nutrient loading
Nutrient loading is the flow of nutrients — mainly phosphorus and nitrogen — into the lake from runoff (lawn fertilizer, septic systems, soil erosion), wildlife, and the air. It's the "input side" of the nutrient budget.
Why it matters to the lake: * Loading is the cause; blooms, weeds, and muddiness are the
P
Phosphorus
Phosphorus is the nutrient that most often limits algae growth in lakes — take it away and algae starve; add it and they multiply. We measure it in parts per billion (ppb); lower is better. Phosphorus in a lake mostly comes from runoff, soil, and sediment.
Why it matters to the lake: * It's the number behind "nutrient level" on our [Lake Status](/lake-status)
pH
pH measures how acidic or alkaline the water is, on a scale from 0 to 14. Most healthy lakes sit between about 6.5 and 8.5. It's affected by algae (which shift pH through the day), rainfall, and minerals in the watershed.
Why it matters to the lake: * A stable pH is a quiet sign the lake's chemistry is in a
S
Scum line
A scum line is a line of algae or debris pushed up against the shore or a dock — often the first visible sign of a forming bloom, before the whole surface turns.
Why it matters to the lake: * It's what our "report a sighting" form exists for: a scum
Secchi disk
A Secchi disk is a 10-inch white-and-blackquartered disk on a rope. You lower it into the water until it disappears from view; that depth is the "Secchi depth." It's the simplest tool in lake monitoring and one of the most useful.
Why it matters to the lake: * It's the tool behind the "Secchi depth" on our [Lake Status](/lake-status)
Secchi depth
The Secchi depth is the depth at which the Secchi disk disappears from view, measured in feet. Bigger number = clearer water. It's a snapshot, not a trend: a single reading can swing with wind, rain, and boat traffic.
Why it matters to the lake: * It's the clearest single number we have on whether the
Stratification (thermal stratification)
Thermal stratification is when a lake splits into layers: a warm, mixed surface layer (epilimnion), a rapid temperature drop in between (thermocline), and a cold, dense bottom layer (hypolimnion). In most temperate lakes it forms in late spring, holds through summer, and breaks down in the fall "turnover."
Why it matters to the lake: * Stratification is why the deep water can run low on oxygen
T
Turbidity
Turbidity is how "cloudy" water looks — the amount of suspended sediment, silt, or particulates scattering light. It's related to but distinct from clarity: a lake can be turbid (muddy) without being algal (green).
Why it matters to the lake: * A muddy look after a storm is usually runoff, not a bloom —
W
Watershed
A watershed is the entire land area — fields, lawns, forests, streets — that drains into the lake. Everything that happens on that land eventually shows up in the water, carried by rain and runoff.
Why it matters to the lake: * You can't fix a lake by working on the lake. The watershed
Zebra mussels
Zebra mussels are tiny (under half an inch), striped, filter-feeding mussels native to Eastern Europe that arrived in North American waters through ballast water and have since spread through recreational boating. They colonize hard surfaces — docks, hulls, intake screens — and can clog them and displace native mussels.
Why it matters to the lake: * Prevention is a member habit: clean your boat, drain your