Rosedale Lake HAB

Harmful Algal Blooms Impact Local Lakes

July 12th, 2019

Rosedale Lake, in Hopewell, NJ, was closed to recreation this week due to the growth of harmful algal blooms (HABs).  New Jersey currently has at least eight ongoing HAB advisories in local recreational lakes cautioning people and their pets not to come into contact with the water. The toxins produced by these HABs can cause various health impacts to people and animals.  According to the New Jersey Department of Environmental Protection (NJDEP), contact with HABs can cause sore throat, eczema, runny nose, headaches, diarrhea, rashes, and other skin and digestive issues. Severe reactions may also result in liver and neurological effects.  The impacts vary depending on the type of algae species and the severity of the bloom.

Rosedale Lake is not alone in having restrictions placed on lake activities.  This latest advisory comes on the heels of the widely-reported harmful algal blooms (HAB) advisory for Lake Hopatcong in Morris County.  Spruce Run, a drinking water reservoir and popular recreation area, is experiencing its second HAB event of the year.  In 2017 and 2018, there were a total of 64 HAB advisories. You can review a listing of all of the 2019 HABs on NJDEP’s website

HABs develop when certain kinds of blue-green algae encounter ideal conditions and form dense blooms.  These conditions include sunlight, warm temperatures, high nutrients, and calm water.  With climate change, we can expect to have more days of warm temperatures. These warmer days may, according to the EPA, favor more HABs.  

Another condition necessary for a HAB to occur are high levels of nutrients, like nitrogen and phosphorus, entering the lake.  One of the most common sources of nutrients is polluted runoff, especially fertilizers that are washed off of our lawns, gardens, farms and other surfaces into waterways after rainfall. High levels of nutrients not only cause HABs, but can also lead to low levels of dissolved oxygen in our lakes. After the algae blooms by feeding off excess nitrogen and phosphorus in the water, it dies off and the decomposition uses up dissolved oxygen. The resulting low levels of dissolved oxygen does not support aquatic life and can, if severe enough, lead to fish die-off.

Polluted stormwater runoff

Proper stormwater management will reduce, but not eliminate, the amount of nutrient-rich runoff that reaches our lakes.  This is why The Watershed Institute has been urging the State and municipalities to enhance the regulations and ordinances that regulate stormwater management.  Enhanced stormwater treatment will reduce both the amount of runoff and the concentration of water quality pollutants that flow from a site. If we can reduce the amount of pollution that is in stormwater runoff, we can reduce the amount of nutrients we discharge into our lakes.

Another very important tool in this fight is stormwater utilities.  Recently, NJ became the 41st state to authorize the use of this tool with the enactment of the Clean Stormwater and Flood Reduction Act.  Stormwater utilities can provide opportunities for government to fix failing stormwater basins, enhance others, and construct other stormwater management systems to better treated the polluted runoff before it enters our waterways.  

You can learn more about The Watershed Institute’s work on stormwater management and stormwater utilities on our website.  

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