Drought caused salt in bay to rise; still in normal range

Keyport Harbor

A new survey released this month found the Raritan Bay is getting salty like the Atlantic Ocean, which is expected because of the overall lack of summer rain.

The Bayshore Watershed Council performs an annual survey of marine life using seining nets. The survey typically collects small baitfish and crabs and documents the species they find at different locations along the Bayshore.

Surveyors also take water samples and measure, among other things the amount of salt in the water.

From their report:

“An uncommon find were salinity readings. Salinity is a measure of the amount of dissolved salts in the water. It is usually expressed in parts per thousand (ppt). In the past during Seine the Bay Day events, salinity readings at sites were in the low 20s ppt. Now due to several drier months, the bay has become unusually saltier with readings on the low to mid 30s ppt, which is more typical of salinity readings in the ocean.”

Experts at Rutgers University agree that the long, hot dry spell this summer is causing the salt spike, but that’s nothing to worry about.

“Large changes in salinity are quite normal in estuaries, and the biology is well adapted to these extremes,” said Silke Severman, an associate professor at the Rutgers University Department of Marine and Coastal Sciences.

The amount of salt in estuaries, like the Raritan and Sandy Hook bays, is regulated by how much freshwater is flowing into the system through rivers, said Bob Chant, a physical oceanographer at Rutgers.

“Since we’ve been in a drought for the last month or so it’s not surprising that salinity is high,” Chant wrote in an email. “In fact, in real hot and dry conditions, some estuaries become “hypersaline” or more salty than the ocean.”

Rainfall has been exceptionally low, in the Raritan River Valley, said David Robinson, the state climatologist  at Rutgers.

In the 60 days prior to Sept. 18, “the ‘heart’ of the most recent dry spell, Somerset and Middlesex counties have had just four inches of rain, which is four-and-a-half inches below normal, Robinson wrote in an email.

“Surrounding counties, portions of which fall within the basin haven’t done much better,” he said.

The lack of rain spurred the state Department of Environmental Protection to issue a drought watch last week for parts of 12 counties, including Bergen, Essex, Hudson, Hunterdon, Mercer, Middlesex, Monmouth, Morris, Ocean, Passaic, Somerset and Union — all of which drain fresh water into the larger New Jersey and New York estuary.

State environmental officials have said that the watch was put in place because of low levels in reservoirs throughout the state, such as the Manasquan Reservoir, and the stress placed on streams throughout the drought-impacted region.

The lack of rain has pushed Raritan River flow to below the 25th percentile, Robinson, the climatologist, said.

Even with the higher amounts of salt in the bays, they are not at their saltiest. Water samples that Chant, the oceanographer took, in 2011 were higher.

“I think it’s been dryer this year than what occurred during my measurement period,” Chant said. “So again, I don’t think this is very unusual — or at least no more unusual than the modest drought we’ve recently experienced.”

Editor’s note: Matthew McGrath is also employed as the communications specialist for New Jersey Sea Grant Consortium of which Rutgers University and the state Department of Environmental Protection are members.