As the algae in the bloom die, they settle to the seafloor and decay using up oxygen. Reductions in dissolved oxygen to 4-5 mg/L have been observed by one of the autonomous underwater vehicles (Gliders) that have been deployed by Rutgers University to sample and monitor the Bight. Updates on glider data can be found here. Levels below the water quality of standard of 5 mg/L can stress and harm fish and other aquatic organisms. Clean Ocean Action (COA) has previously advocated for a glider to be used along the NJ coast by NJDEP and EPA and it is great to see that this effort has been funded, especially given this massive bloom event.
In addition to the upwelling process, another coastal oceanographic process off the northern part of the Jersey Shore has developed over the last week apparently in response to the extensive rain over the weekend in the New York/New Jersey region that resulted in high volumes of runoff and combined sewer overflows in the metropolitan area that discharge into the Hudson River Estuary. The bloom activity in the northern part of the Jersey Shore appears to be related to coastal runoff and the plume, the outflow, of the Hudson River.
COA is requesting the help of divers, fishermen, and boaters in the area to look for tell-tale signs of low dissolved oxygen and document their locations. Fishermen and boaters should be looking for fish floating on the surface or in their nets. Divers should look for lobsters, crabs and fish that usually hide in crevices, but are now in the open and lethargic. Also, divers should look for fish that are located higher on the wrecks and/or breathing with difficulty. If divers know how to use dissolved oxygen kits, they should take samples. COA is also asking government agencies to sample and monitor the bloom and its impacts.