Explaining Those Harmful, Even Deadly, Algal Blooms

Jul 1, 2016

Tanks of different types of algal blooms at Stony Brook University’s School of Marine and Atmospheric Sciences on Long Island, N.Y.
Credit Jordan Bowman / WSHU

Long Island officials say that the Island has a serious wastewater problem. But what makes the water so dangerous?

When household wastewater leaks into the groundwater, it has a lot of nitrogen.

If the nitrogen reaches still water, like a lake, then a chain reaction may start.

Some of the bacteria in the water, called blue-green algae, can consume the nitrogen for energy and reproduce—explosively.

This creates an algal bloom, which can be harmful in two ways.

It can cut off the exchange of oxygen from the air to the water, depleting the supply of oxygen to fish.

This becomes worse when the blue-green algae, technically a type of bacteria, die.

Other organisms that live in the water eat the dead bacteria for nutrients, and use more oxygen in the process.

This could kill the fish due to lack of oxygen.

The dead bacteria also might make the water toxic depending on the chemicals they release when they die.

Even the fish and marine life that survive may become unsafe to eat if they’ve accumulated enough toxins.

In small quantities, like when the bacteria were in the water before the algal bloom, the toxins don’t affect humans.

The danger of the bloom is that it concentrates the toxins to dangerous levels.

However, not all algal blooms are the same. Only some are toxic. Others don’t block the water from the air.

The difference is based on the species of bacteria.

To stay safe, use common sense. Do not drink or swim in water containing an algal bloom.

To report a cyanobacteria bloom where bathing is permitted, call the Suffolk County Department of Health Services’ Office of Ecology at 631-852-5760.

To report one at a body of water in Suffolk County without a bathing beach, call the Division of Water at the New York State Department of Environmental Conservation at 518-402-8179.

Suffolk County Government page on Algae Blooms: http://www.suffolkcountyny.gov/Departments/HealthServices/EnvironmentalQuality/Ecology/MarineWaterQualityMonitoring/HarmfulAlgalBlooms.aspx