Large-scale algae blooms in the Albemarle Sound and its tributaries are prompting water quality experts to remind the public to avoid contact with green or blue water where algae may be over-abundant.
"You'll see bright green water, and as it begins to die off, it turns into a milky blue color. It almost looks like spilled paint," said Brian Wrenn, Ecosystems Branch supervisor at the state Department of Environmental Quality. "The decay of the algae can put off some pretty unpleasant odors as well."
Heavy rains last fall and this spring, followed by high temperatures and low recent rainfall created conditions that allowed the algae to thrive.
Algae blooms are common during the summer, when nutrients, warm water and sunlight are plentiful. Wrenn says blooms this large hadn't been seen in the Albemarle area for roughly 30 years, but since 2015, they've begun cropping up again. This year, the blooms in the northeastern part of the state started in May, earlier than scientists expected.
Nutrient run-off from upstream sources contribute to the algae blooms. Wrenn says there is a statewide effort to create water quality standards related to nutrients, but with many stakeholders and many miles of watershed, it's a slow process.
Algae blooms can absorb the oxygen available in a waterway, triggering fish kills. Some types also produce toxins that can sicken people and pets.
"The general guideline is to just stay out of green water, because that means that algae are over-excited," said algal ecologist Elizabeth Finson. "They're really, really, happy, and they may or may not be toxic, so just err on the side of caution and stay out of green water."