Many CT municipalities see algae blooms occur in their lakes and ponds beginning around mid-summer each year. The warmer water temperatures help foster favorable conditions for excessive algae (and cyanobacteria) to grow. But water temperature alone does not cause these blooms to form, it’s the additional nutrients that end up in our waterbodies when stormwater runoff ushers them from their source, places like yards, fields, sidewalks and roads and into receiving waterbodies. Typically, algae blooms in fresh water are due to elevated levels of phosphorus and algae growth concerns in salt water are due to elevated levels of nitrogen.
In our smaller watersheds, local nutrient sources like lawn fertilizer, Canadian geese, and leaking septic systems are key causes of nutrient loading in waterbodies. If you’re from a coastal town, data from studies by Dr. Jamie Vaudrey are shedding light the local sources of nitrogen on the embayments along Long Island Sound. You can see what the main sources of nitrogen are to your local embayment on this map viewer. Wastewater treatment plants also contribute nutrients to the rivers they discharge into. Many Connecticut treatment plants are now investing millions of dollars to make improvements to reduce the amount of phosphorus they discharge into rivers in response to DEEP’s Phosphorus Strategy.
Connecticut has taken some legislative steps to try to reduce phosphorus to our waterbodies. One law requires detergents to be clearly labeled with the amount of phosphorus they contain and sets the maximum recommended use amount for certain detergents sold in the state. Although the law exempts detergents used in dish washing machines and food processing or dairy equipment from the limit.
More recently, Connecticut passed a law restricting the use of fertilizer, soil amendments, or compost with phosphorus (over .67% phosphate) in 2012. The law generally bans applying these products: on established lawns and impervious surfaces, during winter months, or within 20 feet of a water body unless applied in a particularly discriminating way, in which case, it may be applied 15 feet or more from a water body. There are key exceptions for this law too: Farms and golf courses, two significant sources of nutrients, are not subject to these phosphorus application limits.
What else can be done to avoid algae blooms? Municipalities regulated under the 2016 MS4 General Permit are required to conduct targeted outreach if they have a nutrient (phosphorus or nitrogen) impaired waterbody in town. For example, if a lake is impaired by phosphorus, the municipality could send a mailing to lake residents explaining the importance of maintaining septic systems and properly applying fertilizer. There are plenty of example materials available on CT NEMO’s MS4 website in the Public Outreach section.
Aside from educating the public, MS4 towns must also require developers to use practices that reduce impacts to water quality during construction and allow for future rainfall to seep into the ground to avoid creating more nutrient and pollution-rich stormwater runoff. Finally, towns need to set the example on their own properties, using proper practices that minimize the amount of nutrients carried away by stormwater during the next rainfall.