Christian Roy, Renaissance Lac Brome

Aquatic plants play several important roles: they absorb phosphorus and release oxygen while serving as feeding and spawning grounds and nurseries for a number of aquatic species. In excessive amounts, however, they can interfere with recreational activities such as swimming and boating. An overabundance of aquatic plants may also indicate eutrophication, a lake’s premature aging.

One might think that aquatic plants are what cause the blue-green blooms on the lake, but no, those are caused by cyanobacteria.

A study on the plants in 2009, then in 2020: situation unchanged

Bays and stream mouths are where aquatic plants are most likely to grow and Brome Lake is no exception. That is why grass beds and aquatic plants are heavily concentrated in the bays at Fisher’s Point, Elisabeth Ann Beach and Knowlton Marina and at the mouth of Quilliams Brook.

An inventory of Brome Lake conducted in 2020 identified 32 aquatic plant species, representing a healthy variety.

Dominant species include American eelgrass, Eurasian water-milfoil and longleaf pondweed.

Comparing the more recent study with one conducted in 2009 shows that the situation in Brome Lake is relatively stable. This is good news for users of the lake because there has been no significant deterioration, but it also confirms that the areas that were problematic in 2009 remain so today.

“Zombie plant”

Eurasian watermilfoil is an aquatic alien invasive species (AAIS) that reproduces through fragmentation, meaning that a fragment will break off and become a new rooted shoot.This has earned it the nickname “zombie plant.” Unfortunately, Eurasian watermilfoil remains a major threat to Brome Lake: it is present in 29 of the lake’s 74 aquatic grass beds and is dominant in 10 of them.

Renaissance Brome Lake wants to increase annual monitoring of certain grass beds in order to better understand the spread of this invasive species. A public awareness plan will also be completed in 2021. The map shows the sectors of Brome Lake where Eurasian watermilfoil is present.

Translation: Brian McCordick