Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find cause of dead crabs, fish off coast

31.07.2002


An unusual combination of oceanic and atmospheric events may be to blame for a mysterious and sudden die-off of numerous crabs, fish and invertebrate animals off the central Oregon coast during the past two weeks.

Oregon State University researchers who are studying near-shore ecosystems say extremely low oxygen levels - especially in the lower water column - appear to be the culprit.

"Though we are just beginning to amass the evidence, it appears that there has been a confluence of events relating to coastal upwelling and wind patterns," said Jane Lubchenco, the Wayne and Gladys Valley Professor of Marine Biology at OSU. "There isn’t any sign that this was the result of human activities. It appears to be a natural event, albeit an unusual one."



Scientists first began to suspect a problem in mid-July. Oregon Department of Fish and Wildlife staff members who were surveying the near-shore ocean off Cape Perpetua with a remotely operated vehicle were surprised to find no live fish swimming in an area that in previous years had been densely populated with rockfish. This time, they saw only dead sculpins and invertebrates on the ocean floor.

Calls to ODFW soon began coming in from crabbers, who were pulling up pots that were full of Dungeness crabs, other shellfish, octopus, other invertebrates and fish - and most of them were dead. Then small numbers of dead fish and other sea life began washing ashore near Seal Rock, between Newport and Waldport on the central Oregon coast.

"Some of the crabbers offered to set their pots in certain places and ways to help us learn more," said Dave Fox, marine habitat project leader with ODFW. "There has been a real cooperative effort between the crabbers and the scientists from OSU to help us determine what happened."

Initially, Fox said, the crabbers were concerned the deaths may have been caused by naturally occurring toxins. ODFW sent samples to the Oregon Department of Agriculture for testing, and those tests came back negative. A team of scientists led by Jane Huyer from OSU’s College of Oceanic and Atmospheric Sciences has been monitoring ocean conditions off Newport and off Heceta Head several years, and as part of their routine research measured seawater conditions in mid-July. Huyer reported that the water contained some of the lowest oxygen levels the researchers had ever seen near shore.

Huyer said there is always a large pool of very low oxygen water at depths 2,500 feet below the surface, but this does not normally affect marine life near the coast.

Lubchenco is co-principal investigator for another ongoing research project called the Partnership for Interdisciplinary Studies of Coastal Oceans, or PISCO. Bruce Menge, also co-principal investigator for PISCO, and his team of field researchers recorded more of the same - dead wolf eels, Dungeness crabs and sculpins as well as smaller numbers of dead ling-cod and other rockfish at sites along the central coast. Further water samples taken by PISCO scientists aboard the university’s research ship, the R/V Elakha, provided evidence to explain the mysterious die-off.

"What we found were surprisingly low levels of oxygen in the water column - as low as one or two milligrams per liter, which classified it as hypoxic," said Francis Chan, a post-doctoral researcher on the PISCO project. "That means it cannot sustain most marine life.

"It is almost an unprecedented event around here," he added. "We have a lot of researchers who have been studying this part of the coast for more than 25 years who have never seen such a situation."

Brian Grantham, a research associate in OSU’s Department of Zoology, said the low oxygen levels may have been the result of strong upwelling and unusual atmospheric conditions. From spring through early fall, he said, upwelling brings colder, deeper and more oxygen-depleted water close to shore. There, the high-nutrient waters are exposed to sunlight and microscopic marine plants grow abundantly. As these decay and sink, they consume some of the remaining oxygen in the water.

When summer winds are weak, the surface waters are warm, and there is reduced mixing of oxygen from the surface to the bottom. This allows the low values of oxygen at the bottom to persist and intensify, in effect, smothering much of the sea life in the area.

"If this happens for a day or two, the fish and crabs probably survive," Grantham said. "But over a period of time, perhaps 3-5 days or longer, the oxygen deprivation becomes deadly. It seems to affect the animals that stay hunkered down in one spot, particularly sculpins, wolf eels, worms and young fish. The larger fish may have the ability to swim away and find patches of water that have more oxygen."

Lubchenco said the scientists are not yet sure how widespread the hypoxic zone is, the extent of the damage to sea life, or how long it will last. OSU researchers are planning to collect more samples and download data from PISCO’s network of environmental monitoring stations during the next few days to determine if low oxygen levels are still present, and to identify the physical boundaries of the problem.

ODFW also plans to take out its ROV off Cape Perpetua beginning Aug. 24.

The researchers from OSU and ODFW both reported that the water in the hypoxic zone was murky and there was an odor in the air - "kind of a strong, low-tide smell you’d find in the bay," Fox said.

Oregon is not alone in facing unusual low-oxygen phenomena. The so-called "Dead Zone" in the Gulf of Mexico is experiencing widespread loss of marine life, though the problems there are caused by agricultural runoff via the Mississippi River, said Karina Nielsen, an OSU post-doctoral researcher with PISCO. A more relevant and naturally occurring hypoxic zone takes place off South Africa, she added.

"They have an upwelling system that is similar to that of Oregon, and almost every year for the past 10 years they have seen rock lobsters literally walk out of the water and onto the beach," Nielsen said. "They are desperately looking for oxygen."

The Oregon hypoxic zone is "an unusual event that appears to be naturally occurring," according to Lubchenco. "This is exactly why the research we are doing on near-shore ecosystems is so critical - to better understand the mechanisms behind such events, and increase our ability to respond to them in the most appropriate manner," she said.

ODFW officials are interested in learning if hypoxia has affected other parts of the coast, Fox said. Crabbers and fishermen who encounter unusual numbers of dead marine life are asked to call 541-867-4741.


###
The Partnership for Interdisciplinary Studies of Coast Oceans is a five-year, $20 million project funded by the David and Lucile Packard Foundation. OSU is the lead institution for the study, which also includes Stanford University, the University of California at Santa Cruz, and the University of California at Santa Barbara.

By Mark Floyd, 541-737-0788

SOURCES: Jane Lubchenco (OSU), 541-737-5337; Brian Grantham (OSU), 541-737-5359; Dave Fox (ODFW), 541-867-0300, ext. 228


Jane Lubchenco | EurekAlert!
Further information:
http://www.orst.edu/

More articles from Ecology, The Environment and Conservation:

nachricht Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München

nachricht Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>