Researchers in Melbourne net dolphins for health probe
By Jim Waymer
3rd August 2003
The Associated Press
MELBOURNE -- More than three dozen bottlenose dolphins' dorsal fins don numbered tags.
The tags, to prevent recapture, will fall off in a few weeks. But biologists will continue to track the health of bottlenose dolphin in the Indian River Lagoon for the next five years.
They'll look for signs of emerging microbes and chemicals that may be making dolphins sick. They'll test for diseases more common to people but becoming more prominent in dolphins.
"What happens to the dolphin down the road could definitely happen to us,'' said Greg Bossart, director of marine mammal research at Harbor Branch Oceanographic Institution in Fort Pierce.
Bossart and 50 other researchers on eight boats recently spent two weeks capturing 43 bottlenose dolphins in the Indian River Lagoon. Their five-year, $1.25 million study will be the first in-depth health assessment of the lagoon's top predator.
Along with 50 other biologists, they'll examine bottlenose dolphins in the lagoon and in Charleston, S.C., to compare the health of the two populations.
What they find could yield clues to human disease and how better to protect the lagoon and other estuaries.
"If dolphins are not doing well, it says something about what humans may be exposed to and can link both ocean health and human health,'' said Pat Fair, head of the living marine resources branch of the National Ocean Service Center in South Carolina.
There are an estimated 400 to 600 bottlenose dolphins that spend most of their lives in the lagoon. Bossart wants to know why a third of the 500 bottlenose dolphins Harbor Branch has tracked in the past six years look so sickly. Researchers know some by their diseased dorsal fins and torsos covered with knotty cauliflower-like tumours and fungal infections.
"The coastal animals, they're the one's that are going to be affected most by man's activities,'' Bossart said.
The assaults on dolphin habitat are many, biologists say. Like people, dolphins throughout the world have been building up internal stocks of chemicals such as DDT, PCBs, as well as heavy metals such as mercury.
Pesticides can disrupt hormones in dolphins, fish and in humans, dampening reproductive rates.
Excess nitrogen and phosphorus from septic tanks and farm and fertilizer runoff also feed algae blooms that emit toxins dolphins ingest and breathe.
The problem is knowing what's harmful, said Randy Wells of Mote Marine Laboratory in Sarasota. Wells has studied Sarasota Bay's dolphin since the 1980s.
"There's 10,000 chemicals that humans have put into the environment, and trying to figure out the effects of those is a pretty daunting task,'' Wells said.
He captures dolphin twice a year in Sarasota Bay for health studies he says are becoming increasingly complicated by new chemicals released into the environment, such as fire retardants.
"We're using a weight-of-evidence approach,'' Wells said. ``It's a risk assessment.’’ Bossart suspects such an assessment of Indian River Lagoon dolphins will show signs of environmental stress, caused by man-made chemicals and by pathogens strengthened by global warming.
"In the past two decades, 30 diseases new to medicine have emerged,'' Bossart said, adding that cholera and tuberculosis have also surged back.
In the summer of 2001, at least 35 northern lagoon bottlenose dolphins died within two months, within about 25 miles of each other. After a yearlong federal investigation, biologists couldn't say why the dolphins died. They suspect a new red-tide like toxic algae never seen before in Florida which bloomed that summer, releasing toxins that built up to fatal levels in the dolphins or caused immune suppression. The same poison, saxitoxin, made 20 people sick who ate pufferfish caught near Titusville that summer. The fish remains under a state ban for harvest and consumption.
Many of the dolphins recovered that summer were too decomposed to tell what exactly killed them.
Bossart and the other scientists captured about 20 dolphins near Titusville this month to gain answers about what might have contributed to the unusual deaths.
Bossart and his colleague at Harbor Branch, Steve McCulloch, led the team, which included researchers from as far as Connecticut, California, Canada and Mexico.
Part of the study will be to compare bottlenose here to those in South Carolina. Field work in Charleston, S.C., will start next month.
Researchers capture the dolphin in large nets, hoist them aboard research vessels for examinations that take about an hour.
"There have been no injuries or accidents of any sort,'' McCulloch said.
The scientists record the animal's gender, estimated age, length and weight, and then collect faeces, urine, blood and blubber samples.
They'll measure changes in the health of the two dolphin populations from year to year. For six years, Harbor Branch scientists have seen drastic symptoms of skin infections, most near Stuart.
But Bossart said the dolphins caught this month near the ones in the northern lagoon seemed thinner and less healthy, while dolphins caught near Stuart tended to have more skin problems.
But Dan Odell, who studies dolphin behaviour in the northern lagoon, said the dolphin he sees look healthy. He has yet to witness the extreme skin problems the Harbor Branch scientists documented in the southern lagoon.
"Most of what I've heard is rumour and hearsay,'' said Odell, a researcher at Hubbs-SeaWorld Research Institute in Orlando. “ The animals I've seen look extremely clean... The tough part of all of this is what's normal.''
Between February 2001 and July 2002, Bossart found 17 lagoon dolphins that died from starvation and diseases spurred by immune suppression. He found skin diseases on nine of the 17 dolphins.
Researchers hypothesized that pollution and climate change may be weakening dolphins' immune systems. "It wasn't any one thing specifically, but the pattern was disturbing,'' Bossart said.
Their study, researchers say, could help set priorities in dealing with the most harmful pollution problems. "This is the type of information that resource managers can utilize to better manage resources that we all depend on,'' McCulloch said