By Tony Hagen • editor@newjersey.sierraclub.org
With sturgeon on the brink of extinction in the Delaware River, the Environmental Protection Agency (EPA) has introduced a draft rule (graphic) that would ease one of the threats to this highly sensitive—some might say “canary”—fish. The EPA plans to set limits on how low oxygen levels can drop in the river.
Survival rates of Atlantic sturgeon and shortnose sturgeon tend to drop as dissolved oxygen levels decline. The EPA believes it can improve conditions with tighter controls on discharges of sewage and industrial waste.
Anthropogenic activity (human waste), combined with warmer temperatures, causes algae to proliferate, and when algae die, their decomposition consumes oxygen in the river. This causes hypoxia, or oxygen-starved environments, which are especially harmful to sturgeon.
Heavy sewage discharge from the Philadelphia area has been a chief cause of this problem. Also, nutrients flowing into the Delaware River from farming, golf courses, and lawn maintenance in neighborhoods along the Delaware River also contribute to the growth of algae and hypoxia.
The numbers of adult sturgeon that return to the Delaware River each year to spawn have dwindled to the low hundreds, as opposed to hundreds of thousands two centuries ago, and hypoxia in the warmer months makes it very difficult for their young to survive. Great strides in cleaning up the river have been made over the years, but these hypoxic dead zones remain a problem.
In 2022, following pressure from environmentalists to improve water quality, an EPA investigation concluded that improved oxygenation was essential to make the river livable for sturgeon and other fish that are especially sensitive to low oxygen levels.
The proposed water quality standards would cover a 38-mile stretch of the river from Burlington County to Salem County. They would set minimum oxygen levels that occasionally could be breached but in the aggregate would help ensure that populations of young sturgeon survive to return to the river as adults and spawn anew.
The draft rule has been welcomed by environmental advocates who recognize that the sturgeon population in the Delaware River is in danger of extinction. However, they note that the draft rule is imperfect. For example, its built-in tolerance for long periods of substandard oxygen levels could still allow large populations of juvenile sturgeon to be wiped out.
Our Oxygen-Starved Waters
Hypoxia is a growing problem not just in the Delaware River but also along the East Coast and the Gulf of Mexico, which is notorious for hypoxic zones.
This past summer, an unexpectedly large algae bloom in the Gulf of Maine was believed responsible for reduced lobster catch off Cape Cod. Hypoxic zones off the coast of New Jersey are also believed responsible for recent deaths of fish and crustaceans.
Hypoxia in warmer, shallower waters may cause marine creatures to flee their accustomed ranges and expose them to deeper, possibly more perilous environments. Hypoxic zones may also travel with tides and wind. Some scientists theorize, in addition, that changes in summer storm patterns owing to climate change have influenced the development of hypoxic zones.
The EPA’s public comment period for the draft rule ended prior to publication of this issue of The Jersey Sierran. Advocates for sturgeon survival eagerly await a positive decision on the proposed rule.
Resources
EPA Draft Rule: shorturl.at/oGL48
Problem overview: tinyurl.com/36sv3mwk