Red tides and fish kills reported on Bayside of Northampton as algae bloom moves closer to Shore

Pictured: Smith Beach Friday morning.

Fish kills were reported Thursday and Friday in several bayside creeks across Northampton County, with dead and dying fish surfacing from Plantation Creek north to Hungars Creek and drifting or washing toward shore.

A wide variety of fish have been affected. Spot, flounder, menhaden and other species were among the fish reported floating at the surface and along shorelines in the affected creeks.

The cause of the fish kills has not yet been confirmed. They are occurring, however, as NOAA’s National Centers for Coastal Ocean Science and regional researchers continue tracking a significant harmful algal bloom in the lower Chesapeake Bay. NOAA reported in August that blooms were affecting the lower Bay and major tributaries along Virginia’s western shore.

The bloom has not remained stationary. Old Dominion University researchers first confirmed high concentrations of Margalefidinium polykrikoides in the Lafayette River in July, and NOAA has used satellite imagery to follow the bloom as it moves through the lower Bay with changing currents.

When ShoreDailyNews first reported on the bloom August 26, it appeared concentrated mainly along the western side of the Bay. Scientists noted at the time that normal lower-Bay circulation often keeps those waters to the west, although mixing can carry blooms toward the Eastern Shore. More recent imagery shows the bloom moving eastward, with concentrations observed south of Tangier Island.

The microscopic organism involved, Margalefidinium polykrikoides, can discolor the water reddish-brown, creating what is sometimes called a “mahogany tide.” The species is considered harmful because dense blooms can affect fish and shellfish, particularly young fish and oysters.

Researchers from Old Dominion University, the Virginia Institute of Marine Science and other regional partners have been identifying and monitoring the bloom. NOAA’s National Centers for Coastal Ocean Science is also working to improve monitoring and forecasting of Margalefidinium and other harmful algae in the lower Chesapeake.

Harmful algal blooms can affect marine life in several ways. Dense concentrations of Margalefidinium can interfere with fish and shellfish respiration, while large blooms can also contribute to falling dissolved-oxygen levels as algae respire, die and decompose.

By Friday night, another unusual condition was visible at Smith Beach. The water was bioluminescent, producing a blue-green glow when disturbed. Some dinoflagellates are capable of producing this effect. One species known for intense bioluminescence in the lower Chesapeake is Alexandrium monilatum, which can occur during late-summer harmful algal blooms. The visible glow does not confirm that Alexandrium is present, and water sampling would be needed to identify the organism responsible.

The presence of an algal bloom, bioluminescence and a fish kill at the same time does not by itself establish exactly what killed the fish. Investigators would need water samples, dissolved-oxygen measurements and identification of the algae present to determine whether the deaths resulted from direct effects of a harmful bloom, low oxygen or a combination of conditions.

Phytoplankton are a normal and important part of the Chesapeake Bay ecosystem, but problems can develop when one or two species multiply rapidly and reach unusually high concentrations. Drought followed by renewed rainfall may have created favorable conditions by washing accumulated nitrogen and phosphorus from the land into the Bay.

This year’s weather may have contributed to the size of the HAB bloom, but they happen every year. Drought reduced the nutrients washing into the Bay and helped produce unusually clear water earlier this year. When rain returned, it carried accumulated nitrogen and phosphorus from the land into the water.

NOAA uses satellite measurements of chlorophyll to track the size and movement of large blooms, while researchers analyze water samples to determine which species are present. With fish kills now reported from Plantation Creek north to Hungars Creek, red tide observed at Smith Beach and the tracked bloom moving toward the Eastern Shore, additional sampling will be needed to determine whether the events are connected.

The Virginia Department of Health advises people to avoid unusually discolored, murky or foul-smelling water or water containing visible algae. Suspected blooms can be reported to the state’s Harmful Algal Bloom program, and fish kills can be reported to the Virginia Emergency Operations Center at 1-800-468-8892.