Featured Research

from universities, journals, and other organizations

'Dead Zone' Causing Wave Of Death Off Oregon Coast

Date:
August 14, 2006
Source:
Oregon State University
Summary:
The most severe low-oxygen ocean conditions ever observed on the West Coast of the United States have turned parts of the seafloor off Oregon into a carpet of dead Dungeness crabs and rotting sea worms, a new survey shows. Virtually all of the fish appear to have fled the area.

Hal Weeks, a researcher with the Oregon Department of Fish and Wildlife, worked on OSU's research vessel Elahka on Aug. 8 with a remote operated underwater vehicle to document the "dead zone" that is plaguing the region.
Credit: Image courtesy of Oregon State University

The most severe low-oxygen ocean conditions ever observed on the West Coast of the United States have turned parts of the seafloor off Oregon into a carpet of dead Dungeness crabs and rotting sea worms, a new survey shows. Virtually all of the fish appear to have fled the area.

Scientists, who this week had been looking for signs of the end of this "dead zone," have instead found even more extreme drops in oxygen along the seafloor. This is by far the worst such event since the phenomenon was first identified in 2002, according to researchers at Oregon State University. Levels of dissolved oxygen are approaching zero in some locations.

"We saw a crab graveyard and no fish the entire day," said Jane Lubchenco, the Valley Professor of Marine Biology at OSU. "Thousands and thousands of dead crab and molts were littering the ocean floor, many sea stars were dead, and the fish have either left the area or have died and been washed away.

"Seeing so much carnage on the video screens was shocking and depressing," she said.

OSU scientists with the university-based Partnership for Interdisciplinary Studies of Coastal Oceans, in collaboration with the Oregon Department of Fish and Wildlife, used a remotely operated underwater vehicle this week to document the magnitude of the biological impacts and continue oxygen sampling. This recent low-oxygen event began about a month ago, and its effects are now obvious.

Any level of dissolved oxygen below 1.4 milliliters per liter is considered hypoxic for most marine life. In the latest findings from one area off Cape Perpetua on the central Oregon coast, surveys showed 0.5 milliliters per liter in 45 feet of water; 0.08 in 90 feet; and 0.14 at 150 feet depth. These are levels 10-30 times lower than normal. In one extreme measurement, the oxygen level was 0.05, or close to zero. Oxygen levels that low have never before been measured off the U.S. West Coast.

"Some of the worst conditions are now approaching what we call anoxia, or the absence of oxygen," said Francis Chan, a marine ecologist with OSU and PISCO. "This can lead to a whole different set of chemical reactions, things like the production of hydrogen sulfide, a toxic gas. It's hard to tell just how much mortality, year after year, these systems are going to be able to take."

One of the areas sampled is a rocky reef not far from Yachats, Ore. Ordinarily it's prime rockfish habitat, swarming with black rockfish, ling cod, kelp greenling, and canary rockfish, and the seafloor crawls with large populations of Dungeness crab, sea stars, sea anemones and other marine life.

This week, it is covered in dead and rotting crabs, the fish are gone, and worms that ordinarily burrow into the soft sediments have died and are floating on the bottom.

The water just off the bottom is filled with a massive amount of what researchers call "marine snow" -- fragments of dead pieces of marine life, mostly jellyfish and other invertebrates. As this dead material decays, it is colonized by bacteria that further suck any remaining oxygen out of the water.

"We can't be sure what happened to all the fish, but it's clear they are gone," Lubchenco said. "We are receiving anecdotal reports of rockfish in very shallow waters where they ordinarily are not found. It's likely those areas have higher oxygen levels."

The massive phytoplankton bloom that has contributed to this dead zone has turned large areas of the ocean off Oregon a dirty chocolate brown, the OSU researchers said.

Scientists observed similar but not identical problems in other areas. Some had fewer dead crabs, but still no fish. In one area off Waldport, Ore., that's known for good fishing and crabbing, there were no fish and almost no live crabs.

The exact geographic scope of the problem is unknown, but this year for the first time it has also been observed in waters off the Washington coast as well as Oregon. Due to its intensity, scientists say it's virtually certain to have affected marine life in areas beyond those they have actually documented.

This is the fifth year in a row a dead zone has developed off the Oregon Coast, but none of the previous events were of this magnitude, and they have varied somewhat in their causes and effects. Earlier this year, strong upwelling winds allowed a low-oxygen pool of deep water to build up. That pool has now come closer to shore and is suffocating marine life on a massive scale.

Some strong southerly winds might help push the low-oxygen water further out to sea and reduce the biological impacts, Lubchenco said. The current weather forecast, however, is for just the opposite to occur and for the dead zone event to continue.

There are no seafood safety issues that consumers need to be concerned about, OSU experts say. Only live crabs and other fresh seafood are processed for sale.

Researchers from OSU, PISCO and other state and federal agencies are developing a better understanding of how these dead zone events can occur on a local basis. But it's still unclear why the problem has become an annual event.

Ordinarily, north winds drive ocean currents that provide nutrients to the productive food webs and fisheries of the Pacific Northwest. These crucial currents can also carry naturally low oxygen waters shoreward, setting the stage for dead zone events. Changes in wind patterns can disrupt the balance between productive food webs and dead zones.

This breakdown does not appear to be linked to ocean cycles such as El Niño or the Pacific Decadal Oscillation.

Extreme and unusual fluctuations in wind patterns and ocean currents are consistent with the predicted impacts of some global climate change models, scientists say, but they cannot yet directly link these events to climate change or global warming.


Story Source:

The above story is based on materials provided by Oregon State University. Note: Materials may be edited for content and length.


Cite This Page:

Oregon State University. "'Dead Zone' Causing Wave Of Death Off Oregon Coast." ScienceDaily. ScienceDaily, 14 August 2006. <www.sciencedaily.com/releases/2006/08/060812155855.htm>.
Oregon State University. (2006, August 14). 'Dead Zone' Causing Wave Of Death Off Oregon Coast. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2006/08/060812155855.htm
Oregon State University. "'Dead Zone' Causing Wave Of Death Off Oregon Coast." ScienceDaily. www.sciencedaily.com/releases/2006/08/060812155855.htm (accessed July 25, 2014).

Share This




More Plants & Animals News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

How to Make Single Serving Smoothies: Howdini Hacks

How to Make Single Serving Smoothies: Howdini Hacks

Howdini (July 24, 2014) — Smoothies are a great way to get in lots of healthy ingredients, plus they taste great! Howdini has a trick for making the perfect single-size smoothie that will save you time on cleanup too! All you need is a blender and a mason jar. Video provided by Howdini
Powered by NewsLook.com
Boy Attacked by Shark in Florida

Boy Attacked by Shark in Florida

Reuters - US Online Video (July 24, 2014) — An 8-year-old boy is bitten in the leg by a shark while vacationing at a Florida beach. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) — The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Tyrannosaur Pack-Hunting Theory Aided By New Footprints

Newsy (July 24, 2014) — A new study claims a set of prehistoric T-Rex footprints supports the theory that the giant predators hunted in packs instead of alone. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:  

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile iPhone Android Web
          Follow Facebook Twitter Google+
          Subscribe RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins