Beseck Lake
Beseck Lake, Middlefield
2025 Survey Report
Beseck Lake was surveyed for the sixth time by the Connecticut Agricultural Experiment Station Office of Aquatic Invasive Species (CAES OAIS). In 2025, 20 aquatic plant species were observed in the lake, with four species being invasive: curlyleaf pondweed (Potamogeton crispus), Eurasian watermilfoil (Myriophyllum spicatum), minor naiad (Najas minor), and phragmites (Phragmites australis). Curlyleaf pondweed increased in abundance and frequency compared to 2024, found frequently along the western shoreline of the lake. Eurasian watermilfoil continued to decrease in abundance, only being found in the northern cove of the lake in a few sparse patches. Minor naiad was observed for the first time since 2017 in a small patch by the town beach and another small patch by the Lakeview Estates beach. As a seed-borne annual, it is not uncommon for minor naiad to bloom in some years and not others. It is a low-growing plant that rarely needs management in Connecticut. Phragmites was found in the same locations as previous years. Water chestnut (Trapa natans) was not found in the lake for the second year in a row. Since CAES OAIS pulled the only plant found in 2023, it is unlikely that it was able to establish, but the lake association should continue to monitor in case it reappears. Overall, invasive vegetation did increase from 2024 but did not reach nuisance levels at the time of the survey. Consistent with our visual observations, the frequency of invasive species on transect points did increase from 7.5% in 2024 to 24.2% in 2025 but was still lower than 2011, 2017, and 2023.
Native vegetation was abundant throughout the lake and a nuisance at times. Vasey’s pondweed (Potamogeton vaseyi) and clasping-leaf pondweed (Potamogeton perfoliatus) were the most common. Vasey’s pondweed was found along nearly the entirety of the shoreline in large, dense patches that can impede recreation. Since the appearance on CAES OAIS surveys in 2017, Vasey’s pondweed has increased in abundance and in 2025, occurred on 40.8% of transect points. Clasping-leaf pondweed also appears frequently, but it has maintained a similar frequency since 2004, so the increase in vegetation in 2025 can largely be attributed to Vasey’s pondweed. There were 14 other native species observed in 2025, bringing the total native species richness to 16 species, similar to the 14 species found in 2024 and 18 found in 2023.
Analysis of 2025 water quality results are still ongoing; however, transparency remained low at 5.9 ft, similar to 2023 and 2024. Large blue-green algal blooms have been common throughout the lake in 2023-2025 which is likely responsible for the reduced transparency compared to previous years.
2025 Invasive Aquatic Vegetation Map
| 2004 | 2011 | 2017 | 2023 | 2024 | 2025 | |
| Number of Total Species | 13 | 19 | 21 | 22 | 17 | 20 |
| Number of Native Species | 11 | 16 | 17 | 18 | 14 | 16 |
| Number of Invasive/Non-Native Species | 2 | 3 | 4 | 4 | 3 | 4 |
| Native Species | 2004 | 2011 | 2017 | 2023 | 2024 | 2025 |
| Arrowhead (Sagittaria species) | Present | Present | Present | Present | Present | Present |
| Berchtold's pondweed (Potamogeton berchtoldii) | - | Present | - | - | - | Present |
| Bur-reed (Sparganium species) | - | Present | Present | Present | - | - |
| Cattail (Typha species) | - | - | Present | Present | Present | Present |
| Clasping-leaf pondweed (Potamogeton perfoliatus) | Present | Present | Present | Present | Present | Present |
| Coontail (Ceratophyllum demersum) | Present | Present | Present | Present | - | - |
| Common duckweed (Lemna minor) | - | Present | Present | - | Present | Present |
| Eelgrass (Vallisneria americana) | - | Present | Present | Present | - | - |
| Flat-stemmed pondweed (Potamogeton zosteriformis) | - | Present | - | Present | - | - |
| Horned pondweed (Zannichellia palustris) | Present | Present | - | Present | - | - |
| Leafy pondweed (Potamogeton foliosus) | - | - | Present | - | - | - |
| Pickerelweed (Pontederia cordata) |
- | - | Present | Present | Present | Present |
| Primrose-willow (Ludwigia species) | - | - | - | Present | - | Present |
| Rush (Juncas species) | - | - | - | Present | - | Present |
| Sedge | - | - | - | - | Present | Present |
| Slender naiad (Najas flexilis) | Present | Present | Present | Present | Present | Present |
| Small pondweed (Potamogeton pusillus) | Present | - | Present | Present | Present | - |
| Snailseed pondweed (Potamogeton bicupulatus) | Present | Present | Present | - | - | - |
| Spikerush (Eleocharis species) | - | - | Present | Present | Present | Present |
| Thread-leaf naiad (Najas gracillima) | Present | Present | - | - | - | - |
| Vasey's pondweed (Potamogeton vaseyi) | Present | - | - | Present | Present | Present |
| Watermeal (Wolffia species) | - | Present | - | - | - | - |
| Waterwort (Elatine species) | Present | Present | Present | Present | Present | Present |
| Water smartweed (Polygonum amphibium) | - | - | - | - | Present | Present |
| Water starwort (Callitriche species) | - | Present | Present | - | - | - |
| Western waterweed (Elodea nuttalli) | Present | Present | Present | Present | Present | Present |
| Invasive/Non-Native Species | 2004 | 2011 | 2017 | 2023 | 2024 | 2025 |
| Curlyleaf pondweed (Potamogeton crispus) | Present | Present | Present | Present | Present | Present |
| Eurasian watermilfoil (Myriophyllum spicatum) | Present | Present | Present | Present | Present | Present |
| Minor naiad (Najas minor) | - | Present | Present | - | - | Present |
| Phragmites (Phragmites australis) | - | - | Present | Present | Present | Present |
| Water chestnut (Trapa natans) | - | - | - | Present | - | - |