Friday, August 25, 2006

Another Manifestation of Climate Change

Despite the self-serving rants of some conservative pundits and politicians, global warming is real. The causes are still a subject of debate, though it seems likely that pollution from fossil fuel combustion is the prime culprit. Sea level rise is now included as a constant on USGS maps of the coast and average water temperatures are up both in terms of averages and extreme events.

The manifestation of climate change in Narragansett Bay is sometimes subtle, and at other times strikingly obvious. The clam kill we saw earlier this month was caused, in part, by hot water temperatures in the Bay following a record-setting heat wave. Temperature alone doesn't cause fish and clam kills, it also takes excessive decomposing algae from blooms fueled by nitrogen in wastewater. Rotting algae suck up the dissolved oxygen and the higher the temperature, the less oxygen the water can hold.

The exotic creatures we're observing in the Bay this year are unusual, even for late summer. It's true that we see "bubbles" of the gulfstream bringing tropicals every year, but this year has brought some really strange accidentals. Meanwhile, the native fish assemblage is crashing and this is not a good sign for the Bay. The excellent story by Tom Mooney of the Providence Journal (below) treats this subject well.

What is the take-home message and what can we do about climate change? In addition to supporting policies and elected leaders who are committed to weaning us off our fossil fuel dependency and who have the courage to support wind and renewables, we can act locally to reduce pollution from wastewater. While reducing sewage pollution alone will not reverse climate change, it will help take some of the pressure off the highly-stressed Bay ecosystem, and allow the fish and other marine life to breathe easier. -JT

Fish follow warm water
01:00 AM EDT on Friday, August 25, 2006
BY TOM MOONEYJournal Staff Writer

Mike Laptew has snorkeled for 45 years and makes underwater photography his profession. But the school of fish that filled his viewfinder Wednesday afternoon in the warm waters off Newport mystified him.

About 60 to 80 of the six-inch fish darted around, feeding above a bed of eel grass in eight feet of water.

Curious, Laptew, of North Kingstown, snapped some pictures and sent them yesterday by e-mail to a biologist with the state Department of Environmental Management. "Mystery fish," read his attachment.

The identification came back soon thereafter: the fish were mackerel scud, a sub-tropical fish more often found along southern coastal states.

If the scud are lost, at least they're not alone.

An unusually large number of tropical fish, as well as southern game fish such as cobia, black and red drum, even tarpon, have been reported in Rhode Island waters this month -- not to mention a several-hundred pound manatee, a gentle and endangered mammal that is more than 1,000 miles from its Florida home.

All seemed to have hitched what for most will be a one-way ride on the Gulf Stream. For once the local waters, now in the 70s, start to cool, swimming home won't be an option.
The Gulf Stream is a warm and powerful current that originates in the Gulf of Mexico and swings around Florida before flowing north along the eastern United States and Newfoundland. Its strongest current is usually found over the continental shelf that sits about 90 miles off Rhode Island's coast.

Often in summer or the start of autumn, winds or storms will force a bubble or eddy of warm Gulf water to split off from the stream. As the Gulf Stream heads northeast, the eddy will spin off, continue traveling north, and get trapped between the islands of Southern New England and arm of Cape Cod.

Temperatures in Narragansett Bay and Rhode Island Sound yesterday hovered in the 70s. And earlier this summer, following a heat wave, temperatures in the Upper Bay surpassed 80 degrees, a temperature that exacerbated the problem of low dissolved oxygen levels and may have contributed to a massive die off of soft-shelled clams.

Scientist point to the summer's warm spell, the Gulf current and global warming as possible contributors for the number of warm-water visitors this summer.

"I don't know for sure what the reason is," says John Torgan, baykeeper with Save the Bay. "I've been careful about linking all of this to global climate change. There have been some unusual winds and currents that have brought some of this tropical warm water in. However, there are some things we do know that are different."

For instance, said Torgan, the average Bay water temperature has increased 3 degrees over the past few decades, which could be contributing to a shift in the assemblages of fish species, with cold-water species like cod and haddock moving farther north and fish more tolerant of warmer water moving in.

"What's different is we've seen warmer water and we're seeing an increased sighting of these rare or accidental species in Narragansett Bay and Rhode Island Sound."

Jean Bambara is an aquarist at Save the Bay's Exploration Center at Easton's Beach in Newport, which helps educate people about fish and plant life in Narragansett Bay. Once a week or so Bambara will pull a seine net through the shallow waters of Jamestown looking for tropical fish that she can display at the center.

"We're always catching tropicals during the summer months but I mean there are a lot more," said Bambara. "Probably about double the amount."

Among her catches so far this season have been juvenile orange filefish, snowy grouper and lookdowns -- "all the pretty tropical ones that people pay a lot of money for." Often she will catch banded rudderfish, spotfin butterflyfish, grey triggerfish, bandtail puffer fish and bicolor damselfish.

Larger tropical fish such as crevalle jacks, permit and sennets -- which are a smaller version of a barracuda -- are also being caught in Rhode Island waters, said Torgan.
Bambara said she received a phone call from a local lobsterman the other day who wanted to donate to the center something he caught in one of his traps: a large trigger fish.
Dave Beutel works as a sustainable fisheries specialist at the University of Rhode Island, where he is often talking to commercial fisherman, several of whom run fish traps off the Rhode Island coast.

Among the fish caught in those traps so far this summer, he said, have been cobia, which looks like a cod with a flatter head, red drum, which rarely travel north of Virginia, a pilot fish and a sheepshead, a fish common off Florida and Georgia that looks like a giant scup and eats barnacles off pilings.

"I'm going to bet that somebody will call any day with a report of a barracuda," Beutel said. "That usually happens around now."

Tarpon were reportedly caught off Newport a few weeks ago, which was not the first time. A picture of a 5-foot tarpon caught at the Goat Island Causeway a quarter-century ago still hands in the Clambake Club in Middletown.

As for the traveling manatee, the DEM says it hasn't received a reported sighting of the plant-eating creature since Tuesday, when it was seen nosing around Wickford Harbor.
The manatee has caught the attention of the U.S. Geological Survey, which has a team of researchers who track the endangered animals.

Survey researchers at first thought the manatee might be Chessie, a manatee that wandered by the Statute of Liberty in 2001. But researchers compared pictures of both animals and determined the markings on their skin did not match.

"In previous centuries it was probably common for manatees to migrate up the coast," said Catherine Puckett with the geological survey. Sightings of "sea monsters" in Chesapeake Bay were probably migrating manatees. "But there are so few of them now" -- a few thousand -- "that fewer of them migrate at all anymore."

Manatees like water temperatures above 68 degrees. They can swim 30 miles a day. Last week it was spotted off Woods Hole. If it is now in Rhode Island, it could be making its way back home.

"The thinking is," said Puckett, "he is probably going to turn around and head back south because of the onset of cooler weather." / (401) 277-7359

No comments:

Post a Comment