Caribbean blue waters elude Delaware beaches

Forty miles north of Rehoboth Beach, the ocean off New Jersey has been as clear and blue as the Caribbean.

But not here. Our ocean still has that greenish-brown hue so common to the Mid-Atlantic.

If you want the clear blue, you need to swim out beyond the breakers where sand  and sediment aren't churning in the surf.

"We're not experiencing that kind of color," said Rehoboth Beach Patrol Capt. Kent Buckson of the Caribbean effect.

Instead, visitors to the Delaware Coast are seeing an amazing array of sea life in the near shore waters and, so far, have enjoyed a summer that is free from jellyfish, with water temperatures a perfect 74 degrees, he said.

The difference between the Caribbean blue in New Jersey from about Atlantic City north and the Delaware green has to do with wind and rain patterns that can vary widely along the coast.

NASA's Earth Observatory captured a satellite image of a massive phytoplankton bloom off the New Jersey Coast earlier this month.

Big phytoplankton blooms occur when there is both sunlight and nutrients to fuel their growth. When the blooms are really large they can be seen from space. NASA's Moderate Resolution Imaging Spectroradiometer ( MODIS) captured a photo of a bloom off New Jersey on July 6.

Not all blooms are good. Sometimes, the source of nutrients is pollution from onshore sources, a factor during a recent bloom off the coast of Florida.

Other times, the algae blooms form from coastal upwelling events. During an upwelling, the wind blows the warm surface water away from shore. Cooler, water that is often rich with nutrients rises from deeper in the water column. This shift can fuel a phytoplankton bloom.

Along our coast, prolonged winds from the west can blow the warmer water away from shore.

“These upwellings occur every summer, and fuel large phytoplankton blooms,” said Oscar Schofield, a marine scientist at Rutgers University. “Studies have suggested these upwelling events occur several times each summer and lead to large blooms that can discolor the water.”

At the University of Delaware's Center for Remote Sensing, researchers also picked up the large phytoplankton bloom north of Delaware Bay along the New Jersey shore. In all of the images, the bloom is light blue. The puffy white objects are clouds and the deeper blue is water. Land is green.

STORY: TGIF: 5 things to do this weekend

STORY: Beach, fair to make for busy travel weekend

Monitoring these blooms is important, said  Enhui Liao, a graduate student during research at the remote sensing center.

"The organic matter generated from the phytoplankton bloom can sink ... and result in an oxygen depletion over the sea floor," he said. "This can affect public human health, coastal ecosystems, and commercial fisheries. This bloom occurs in the summer in contrast to the more common spring and fall blooms, and expands far beyond the typical scale of summertime upwelling."

Bloom leads to fishkill

Four decades ago, a large phytoplankton bloom occurred in the Mid-Atlantic and caused oxygen levels to drop and hydrogen sulfide levels to rise. The end result: fish kills off the New Jersey coast from Sandy Hook south to Cape May.

Scientists at the time looked at the factors that led to the phytoplankton bloom and the subsequent fish kills. They concluded that the first six months of 1976 were warmer than normal, the wind direction was from the south in the early spring rather than the more typical northeast and there were few coastal storms that winter.

There was no sign of an environmental disaster until late July, according to a report compiled after the event by the National Oceanic and Atmospheric Administration.

Then, during the fourth week of July, sport divers started reporting dead fish around shipwrecks off the north Jersey coast. The second red flag came when a commercial trawl fisherman reported up to 75 percent of his catch was dead. The report described the fish and shellfish mortality as a "resource disaster."

In all, there was a 3,320-square-mile dead zone just off the coast of New Jersey that summer. It lingered into October until water temperatures started to drop and weather patterns shifted to allow better mixing in the ocean. The culprit was a microscopic algae, ceratium tripos, which normally lives in small numbers in cooler, bottom waters off the Mid-Attlantic.

Some blamed the proximity to an ocean dumping site as one possible cause but the scientists found no link between the bloom, the oxygen depletion and the fish and shellfish die-off.

There are other reasons to keep an eye on these blooms, Liao said. Scientists who study climate change also have an interest in monitoring these phytoplankton blooms, he said.

Movement of blooms can be driven by coastal currents, upwelling and ocean eddies, he said.

One reason New Jersey had this latest plankton bloom and Delaware didn't has to do with wind, Liao said. The prevailing wind along the New Jersey coast is northeast. This pushes the surface water off-shore, which can trigger upwelling.

Delaware can get upwelling events, too. But they are less common and typically take several days of west or southwest wind.

At the entrance to Delaware Bay, one of the Cape May Lewes Ferry vessels does continuous monitoring of the water with every crossing in a partnership with the University of Delaware.

Dana Veron, an associate professor and Environmental Science & Studies Director at the College of Earth, Ocean and Environment, said her team did notice a drop in the minimum water temperatures starting Sunday and continuing through Wednesday. That is a sign of a possible upwelling event, she said.

While wind direction is one factor triggering upwelling and because

the upwelled bottom water is rich in nutrients, it contains food that phytoplankton need to grow fast. That can lead to large blooms and because the surface water continually moves offshore, the bloom can expand, Liao said.

The satellite data lets scientists see what is happening very quickly and allow them to look at large areas, he said.

Rare species here

Meanwhile, at the beach, Rehoboth's top lifeguard Buckson said it's been a heck of a summer for sea life, besides the usual Atlantic bottle-nosed dolphins there have been skates, dogfish, blue fish, bait fish and even a few whales.

About a week-and-a-half ago, Buckson said he saw a whale rise out of the water and breach.

"That was actually one of the highlights of my career to see that," he said.

In fish surveys recently conducted in Delaware Bay, state fisheries biologist Mike Greco said they saw "the usual stuff" for a July. But state fisheries officials are hearing reports of southern species like pompano, permit and cobia being caught in Delaware waters this summer. And, he said, one angler caught a snowy grouper -- a fish more common in Florida -- in the Baltimore Canyon off the Delaware coast.

They are also seeing menhaden in the trawl survey. These bottom of the food chain fish often draw in other sport species like bluefish and even sharks, he said.

As for swimmers, if you want really clear water, you can find it in Delaware, said Dewey Beach Patrol Captain Todd Fritchman.

"You have to get several hundred feet off shore," he said.

Reach Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.