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Title: Oceanic Dead Zones Off West Coast are the 'New Normal'
Source:
http://scienceblogs.com
URL Source: http://scienceblogs.com/grrlscienti ... nic_dead_zones_on_west_coa.php
Published: Feb 17, 2008
Author: http://scienceblogs.com
Post Date: 2008-02-17 14:56:48 by robin
Keywords: None
Views: 140
Comments: 12
Millions of dead crabs are washing up onto Oregon and Washington state beaches from the offshore "dead zone". Ever since it was first noticed by crab fishermen who hauled up hundreds of dead and dying crabs in 2002, the "dead zone" that popped up in the waters along the northwestern coastal shelf just off the coast of Oregon has claimed unknown millions of lives. This oxygen-depleted region has transformed formerly rich seafloor communities teeming with life into vast graveyards filled with the bodies of crabs, echinoderms, molluscs, sea worms and other creatures. This carnage was easily visible to a team of research scientists from Oregon State University, who sent an underwater vehicle, equipped with video cameras, into the depths to look around. "We saw a crab graveyard and no fish the entire day," noted Jane Lubchenco, co-author of the papers that report on their discovery. Lubchenco is the Valley Professor of Marine Biology at Oregon State University. "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." The team measured the dissolved oxygen in these dead areas and made a shocking discovery: there was almost none at all. When dissolved oxygen is 1.4 milliliters per liter, it is considered hypoxic for most marine life -- so a "dead zone" forms. However, some of the data collected by the team from one area off Cape Perpetua on the central Oregon coast showed that dissolved oxygen was as low as 0.5 milliliters per liter in just 45 feet of water; 0.08 in 90 feet; and 0.14 at 150 feet depth. Data collected from other areas off the Oregon coast are similar (figure 1); Figure 1: Dissolved oxygen profiles during the upwelling season (mid-April to mid-October) in the upper 800 m of the continental shelf and slope of Oregon (42.00°N to 46.00°N). (A) 1950 to 1999 from the World Ocean Database and Oregon State University archives (n = 3101 hydrocasts, blue). (B) (A) with additional data for 2000 to 2005 (n = 834 hydrocasts, green). (C) (A) and (B) plus data for 2006 (n = 220 hydrocasts, red). The black vertical line denotes the 0.5 ml l-1 threshold. (Insets) Overlapping locations of hydrographic (blue, green, and red) and remotely operated vehicle (black) stations through time and the 100-m and 1000-m isobaths. [larger view of data graphs]. Oxygen concentrations that low have never before been measured off the U.S. West Coast (figure 1A). According to scientists, the dead zone off the West Coast of North America has another cause: global warming. Here's how it works: Winds cause the oceanic rivers of nutrients, such as the California Current in this case, to flow upwards from the deep, carrying nutrients and phyoplankton into the sunlight, which triggers the phytoplankton to reproduce, to "bloom". This is the normal state of things, but since global warming has been causing land temperatures to increase, these winds have become stronger and more persistent. This is not normal because it prolongs the oceanic upwelling, producing a surplus of phytoplankton that isn't consumed and subsequently dies, and sinks to the seafloor to decay. As the bacterial-mediated breakdown occurs, dissolved oxygen in the surrounding water is depleted to dangerously low levels -- sometimes there is none at all. This causes every living thing in the area to either die or flee, further adding to the ecological imbalance. Unfortunately, this cycle has repeated itself every summer and autumn ever since those Oregon crab fishermen first noticed its effects in 2002. Neither El Nino nor La Nina have any demonstrable effect on this phenomenon. This particular dead zone represents one of the many ways in which climate change is damaging the global environment: by depleting the concentrations of dissolved oxygen in a benthic marine habitat, much larger marine communities that cannot adapt quickly enough are also severely disrupted. "We seem to have crossed a tipping point," Lubchenco observed. "Low-oxygen zones off the Northwest coast appear to be the new normal." This paper was published in Science. LATimes (quotes and "dead zone" graphic).
These low-oxygen "dead zones" have suddenly been appearing along various coastal regions throughout the world recently and result from a variety of causes. For example, a low-oxygen zone appears each spring off the coast of Louisiana due to fertilizers in farm runoff and sewage present in the Mississippi River. When the Mississippi flows into the sea, it creates a nutrient-rich area that triggers huge but short-lived algal blooms that soon die, sink to the seafloor and are decomposed by bacteria that produce toxic sulfide gases. As the bacteria break down the dead algae and other microscopic plants and animals, dissolved oxygen is removed from the seawater, thereby creating a low-oxygen "dead zone" where most creatures cannot survive.
Sources
Chan, F., Barth, J.A., Lubchenco, J., Kirincich, A., Weeks, H., Peterson, W.T., Menge, B.A. (2008). Emergence of Anoxia in the California Current Large Marine Ecosystem. Science, 319(5865), 920. | DOI: 10.1126/science.1149016 [PDF]. (story and data figure).
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#2. To: robin, rowdee, Dakmar, Jethro Tull, christine, lodwick, Jethro Tull, angle, Ferret Mike, buckeye, richard9151 (#0)
Years ago I used my newspaper column in MD to support the dredging and improving of the shipping lanes in the Chesapeake Bay, the Delaware river and the C&D canal which connects the north end of the bay in MD with the Delaware river in DE. In addition to wanting Baltimore and Philadelphia to remain competitive ports (which means accommodating deeper draft tankers and merchant vessels) I also support the Army Corps of Engineers' plan to provide emergency anchorages in the bay and the river, so that ships with mechanical and/or steering problems or those that are suddenly overwhelmed by severe weather such as rain or ice can safely anchor out of the channels and away from delicate estuaries that would be destroyed if a ship cracks open and leaks oil. In the course of my dogfights with opponents within the pages of the paper I learned that fishers had lobbied the MD legislature to pass a law to prevent the dumping of dredge spoils in the deep water trough off Annapolis, MD. Despite the fact that the trough is 100 feet deep and there's no oxygen or critters to speak of in it, fishers are superstitious, and, they didn't want the COE to dump what would have amounted to a 6 inch thick layer of spoils on the bottom of this dead zone in the middle of the bay. This article triggered that memory trace and the battles I fought with stubborn, silly, superstitious fools who won't let the facts get in the way of their beliefs. Many of the folks who viewed me and my column with suspicion changed their views, and I won over a lot of watermen when I told them the story of my father's last trip through the bay and canal to Philadelphia. _____________________________________ The Story Before I was born my dad was the first mate on a seagoing tugboat. He took pity on a man suffering from cancer of the face, and hired the man to ride on the first of two barges to be towed on the trip, and the man (who couldn't get work because of his disfigurement) was thrilled and grateful according to my mother who also met him. My oldest half brother was also making this, his first trip. They had no way of knowing that for most it would be their last. When my dad boarded the tug he checked with the captain to see if he had the weather report, and the captain signaled to take her out. The captain was entertaining two "ladies" in his cabin and was drinking, so my father assumed that it was another one of those trips when he would run the tug to its destination while the old man played in his quarters. A few hours after leaving Norfolk the tug was caught in the middle of the bay in a horrendous rainstorm. My brother ran to the wheel house and informed Pappy that the first barge in tow, The Ecky was gone! My father directed my brother to cut the hawser (tow line) with an axe, and my brother departed. He returned a moment later and said, "DO YOU MEAN CUT THE LINE???" My brother left again and freed the tug from its doomed cargo. (This was my brother's first trip and he quite understandably didn't want to mistake THAT instruction!) Dad began spinning the wheel and making right angle turns, timing them with the waves to avoid scuttling the boat, and spotlighting the water for the missing man. The tug had an electric steering mechanism and would sometimes blow fuses if the wheel was turned too quickly, but my father ignored that and rolled the dice in the frantic search for the man overboard. The captain was awakened and briefed on the disaster, and he "sat down and cried like a baby". I'll never know if he wept for the lost man or the shameful end of his own career. When it became apparent that the missing man was not to be recovered that morning, Dad proceeded to Philadelphia where the tug was boarded by investigators and company officials. The captain was fired on the spot and he and the two bimbos were escorted to shore, and my Dad was offered the job of captain, which he declined. He agreed to bring the tug home to Norfolk where he and my brother stepped off the boat, never to board another. The captain surrendered his papers and was allowed to retreat into a well deserved anonymity, and the cancer victim's body was recovered. Navy divers set charges and flattened The Ecky and the 2nd barge The Fell on the bottom so they wouldn't pose hazards to shipping in the relatively shallow waters of the Chesapeake Bay. A few months after the tragedy my father ran into the only crew member who was still in the business, the engineer. Dad asked why the steering mechanism hadn't popped a fuse when he spun the wheel, and the engineer said, "The first time I felt you make a hard turn I pulled the fuse and put in a screwdriver!" When my parents first told me this story I felt my father's grief for the man that he had hired to ride on the barge, and I do to this day. But, I had to ask why he had declined the position of captain of the seagoing tugboat that had taken him to South America and other places. "There was nothing stopping me from getting my own weather report when I saw the captain's condition" he said. And, despite the fact that I wanted to comfort my father, it was one of those times in my life when there was simply nothing I could say. ______________________ After this story ran many of the MD watermen and others who had questioned my motives for supporting the bay and river project understood me better. Had my father had fair warning of the storm he could have ducked behind Solomon's Island and still had room to turn the tug (with two scows in tow) around after the storm passed. But, anywhere farther North in the bay or in the Delaware river there were no safe anchorages to protect shipping from monster waves and wind. And, safe anchorages could mean that the precious bay assets like the Chesapeake Blue Crab and the striped bass or rockfish are less likely to be devastated by a catastrophic Exxon Valdez-type of disaster. The damage to Alaska's Prince William Sound may never completely mitigated, and the thought of that happening to my beloved Chesapeake and Delaware bays is too terrible to contemplate, and, THAT is why I support the presently stalled Corps of Engineers' plan to improve the bay, canal and river.
Strong stuff - thank you for sharing this story with us.
#4. To: lodwick (#3)
Thank you, Sir.
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#3. To: HOUNDDAWG (#2)
"There was nothing stopping me from getting my own weather report when I saw the captain's condition" he said. And, despite the fact that I wanted to comfort my father, it was one of those times in my life when there was simply nothing I could say.
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