A midsummer checkup confirmed a few, mostly discouraging, trends about the health of Narragansett Bay.

Equipped with submersible Sea-Bird monitoring devices, observers from Save The Bay, along with Brown University scientists and students, recently crisscrossed the bay in three boats, taking measurements of the water’s salinity, temperature and oxygen content.

The collaborative project, which includes considerable support from the Narragansett Bay Estuary Program, conducts the surveys as part of an 11-year study of dozens of areas with low levels of dissolved oxygen. It also aims to determine if hundreds of millions of dollars spent upgrading wastewater treatment facilities and managing stormwater runoff are improving the state’s complex aquatic ecosystem.

“There is very little actual water quality monitoring that is going on,” said Save The Bay’s John Torgan. The bimonthly surveys, he added, are “the best real-time information on the health of the bay.”

Data gathered by a crew in upper Narragansett Bay, from Warwick and Barrington up into the Seekonk River in Providence, underscored the chronic hypoxia, or low oxygen levels, that has been suffocating sea life in recent years.

Although cooler and deeper water tends to hold more life-sustaining oxygen, these lower depths were generally lacking air because of excessive decay of organic matter, infrequent surface winds and higher-than-average temperatures, research suggests.

“All the upper bay fishing stations are hot and dead. They’re pretty lifeless; there’s nothing going on there,” Torgan said.

The warmer water temperatures in Rhode Island may be preferable for recreational boating and swimming, but they are tough on sea life. A real-time reading of 76.3 degrees near the Pomham Rock lighthouse in Riverside elicits a “Yecck!” from Torgan. Followed by “it’s warm,” from Steven Clemens, a geologist and assistant research professor at Brown.

Soon after, an oxygen reading of zero, the lowest of the summer, is recorded in a shallow region a few hundred yards from Save The Bay’s waterfront headquarters.

“When it gets to zero, it’s called anoxic, not suitable for anything, as bad as it gets,” Torgan said.

Fortunately, the hypoxic conditions are seasonal and sea life is expected to return when water temperatures drop later in the year. Yet as summer heat takes hold, the habitat becomes less hospitable for fish and lobster, while other marine species, such as blue crab, thrive. Blue crabs are common in warmer waters and habitats with lots of rain such as Chesapeake Bay. “No one can ever remember seeing as many (blue crab) as we’re seeing this year,” Torgan said.

During breaks between hauling the 50-pound Sea-Bird in and out of the water, Clemens explained how global warming alters sea life. His years of studying carbon dioxide trapped in soil and ice samples show that the planet is warming more rapidly than at any point in the past 800,000 years. The numbers, he said, prove that manmade carbon dioxide has increased global warming at a rate 40 to 50 times faster than naturally occurring climate ebb and flows.

“Certainly, carbon dioxide is driving the change in temperature,” he said.

As the high-tech equipment was packed up and headed back to a Brown University science lab for further study, Torgan summed up what he’s observed during his six surveys this spring and summer.

“We’re seeing warmer water, lower oxygen, more algae blooms,” he said. While that’s trouble for the ecosystem in and around the northern half of Narragansett Bay, the lower portions have maintained more sea life thanks to cooler water temperatures, he added.

“As expected, the worst is in the upper bay,” Torgan said.

Wildlife, however, isn’t completely absent from upper Narragansett Bay. Along with countless minnows, osprey were seen feeding on a school of menhaden during a recent Save The Bay cruise. A porpoise and seal also were sighted in recent weeks.

With 10 years of data to draw from, Clemens said, the next five years of research in Narragansett Bay will be examined closely to see if stormwater runoff management and sewer system upgrades are improving life above and below the water. New studies also are underway to determine if low oxygen readings are the exception or an inevitable natural occurrence.

“The zeros, we’re used to them,” Clemens said. “They may be shocking to some people, but I don’t think we saw anything out of the ordinary from the last 10 years.”