Byllesby Lake vs Marion Lake
Water quality, depth, fish species, and recreation comparison.
Marion Lake reads lower on nutrients and algae than Byllesby Lake. Both are in Dakota County, Minnesota.
Both Byllesby Lake and Marion Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any differences in the readings here are about the lakes themselves, not the agencies sampling them. Marion Lake reads materially cleaner than Byllesby Lake on nutrients and algae. A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.
For a recreational visitor, the wider gap in the readings is decisive: Marion Lake has the lower nutrient and algae numbers. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?
Byllesby Lake
Very murky, less than 3 ft of visibility.
Marion Lake
Moderate clarity, visible to about 7 ft.
Side-by-Side Metrics
| Metric | Byllesby Lake | Marion Lake |
|---|---|---|
| Water Clarity | 3 ft | 7 ft Better |
| Phosphorus | 227 µg/L | 20 µg/L Better |
| Chlorophyll-a (Algae) | 40.7 µg/L | 4.6 µg/L Better |
| Maximum Depth | 50 ft Better | 21 ft |
| Surface Area | 1,368 acres | 530 acres |
| Public Access | Yes | Yes |
| Fish Species | 19 Better | 14 |
| Trophic State | hypereutrophic | mesotrophic |
A green ✓ marks the better value for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better). Surface area and trophic state carry no tick — a bigger lake is not a better lake.
Verdict
Marion Lake reads lower on nutrients and algae than Byllesby Lake. Water clarity: 7 ft vs 3 ft. For more fish-species variety, Byllesby Lake edges ahead with 19 documented species.
Source: EPA National Aquatic Resource Surveys, 2026.