Dead zone (ecology): Difference between revisions
Content deleted Content added
No edit summary |
←Replaced content with ' this is the most confusing thin to study evrrr!!!! hhaahhaha im hot =]] hahhah' |
||
| Line 1: | Line 1: | ||
this is the most confusing thin to study evrrr!!!! hhaahhaha im hot =]] hahhah |
|||
:''This page is about the oceanic phenomenon adn the great sea, and maddybeing amazing, and bored, and confusedd [; see ''[[Dead Zone]]'' for other uses.'' |
|||
{{ocean fisheries topics}} |
|||
'''Dead zones''' are [[hypoxia (environmental)|hypoxic]] (low-[[oxygen]]) areas in the world's oceans, the observed incidences of which have been increasing since oceanographers began noting them in the 1970s. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans which naturally have little life are not considered "dead zones".) The term could as well apply to the identical phenomenon in large lakes. |
|||
In March 2004, when the recently-established [[UN Environment Programme]] published its first [[UN Environment Programme|Global Environment Outlook Year Book]] (''GEO Year Book 2003'') it reported 146 dead zones in the world oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometre (0.4 mi²), but the largest dead zone covered 70,000 square kilometres (27,000 mi²). A 2008 study counted 405 dead zones worldwide.<ref name="sfgate" /> |
|||
==Causes of dead zones== |
|||
Aquatic and marine dead zones can be caused by an increase in chemical nutrients in the water, known as [[eutrophication]]. Chemical [[fertilizer]] is considered the prime cause of dead zones around the world. <ref name="msnbc">http://www.msnbc.msn.com/id/22301669 Corn boom could expand ‘dead zone’ in Gulf</ref> |
|||
The Pacific coast of the [[United States]] between California and Washington has a 1120 square mile (2900 km²) dead zone caused by stronger winds that many associate with global warming. <ref name="oregondeadzone">http://www.latimes.com/news/local/la-me-deadzone15feb15,0,3979313.story Dead zones off Oregon and Washington likely tied to global warming, study says</ref>. This dead zone has recurred between June and September every year since 2002. <ref name="oregondeadzone"/> |
|||
Additionally, natural oceanographic phenomena can cause deoxygenation of parts of the water column. For example, enclosed bodies of water such as [[fjords]] or the [[Black Sea]] have shallow sills at their entrances causing water to be stagnant there for a long time. The eastern tropical Pacific Ocean and Northern Indian Ocean have lowered oxygen concentrations which are thought to be in regions where there is minimal circulation to replace the oxygen that is consumed (e.g. Pickard & Emery 1982, p 47).<ref>http://www.nodc.noaa.gov/OC5/WOA01F/oxsearch.html</ref> |
|||
Remains of organisms found within [[sediment]] layers near the mouth of the [[Mississippi River]] indicate four hypoxic events before the advent of artificial fertilizer. In these sediment layers, [[anoxia]]-tolerant species are the most prevalent remains found. The periods indicated by the sediment record correspond to historic records of high river flow recorded by instruments at [[Vicksburg, Mississippi|Vicksburg]], [[Mississippi]]. |
|||
==Effects of dead zones== |
|||
[[Image:Fishkillk.jpg|frame|left|Underwater video frame of the sea floor in the Western [[Baltic Sea|Baltic]] covered with dead or dying crabs, fish and clams killed by oxygen depletion]] |
|||
Low oxygen levels recorded along the [[Gulf Coast]] of [[North America]] have led to reproductive problems in fish involving decreased size of reproductive organs, low egg counts and lack of spawning. |
|||
In a study of the Gulf [[killifish]] by the [[Southeastern Louisiana University]] done in three bays along the Gulf Coast, fish living in bays where the oxygen levels in the water dropped to 1 to 2 parts per million (ppm) for 3 or more hours per day were found to have smaller [[Sex organ|reproductive organs]]. The male gonads were 34% to 50% as large as males of similar size in bays where the oxygen levels were normal (6 to 8 ppm). Females were found to have ovaries that were half as large as those in normal oxygen levels. The number of eggs in females living in hypoxic waters were only one-seventh the number of eggs in fish living in normal oxygen levels. (Landry, et al., 2004) |
|||
Fish raised in laboratory-created hypoxic conditions showed extremely low [[hormone|sex-hormone]] concentrations and increased elevation of activity in two [[gene]]s triggered by the hypoxia-inductile factor (HIF) [[protein]]. Under hypoxic conditions, HIF pairs with another protein, ARNT. The two then bind to DNA in cells, activating genes in those cells. |
|||
Under normal oxygen conditions, ARNT combines with estrogen to activate genes. Hypoxic cells in a test tube didn't react to estrogen placed in the tube. HIF appears to render ARNT unavailable to interact with estrogen, providing a mechanism by which hypoxic conditions alter reproduction in fish. (Johanning, et. al, 2004) |
|||
It might be expected that fish would flee this potential suffocation, but they are often quickly rendered unconscious and doomed. Slow moving bottom-dwelling creatures like clams, lobsters and oysters are unable to escape. All colonial animals are extinguished. The normal mineralization and recycling that occurs among [[benthos|benthic]] life-forms is stifled. |
|||
==Locations of dead zones== NORTH AMERICCAA!!! =]] |
|||
In the 1970s, marine dead zones were first noted in areas where intensive economic use stimulated "first-world" scientific scrutiny: in the U.S. East Coast's [[Chesapeake Bay]], in Scandinavia's [[strait]] called the [[Kattegat]], which is the mouth of the [[Baltic Sea]] and in other important Baltic Sea fishing grounds, in the [[Black Sea]], (which may have been anoxic in its deepest levels for millennia, however) and in the northern [[Adriatic]]. |
|||
Other marine dead zones have apparently appeared in coastal waters of South America, China, Japan, and southeast Australia. In the case of New Zealand, with a population of only 4 million people, set in a region of low to moderate nitrate nitrogen supply at 100 m (330 ft)[http://www.nodc.noaa.gov/OC5/WOA01F/nusearch.html], previous reports of dead zones arise because of misinterpretations of two papers (Taylor et al. 1985; Morrisey et al. 2000) and the most recent UNEP report omits New Zealand from the affected regions [http://www.gpa.unep.org/bin/php/igr/igr2/supporting.php]. |
|||
A 2008 study counted 405 dead zones worldwide.<ref name="sfgate">http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/08/15/MNLD12ADSN.DTL</ref> |
|||
===Oregon=== |
|||
[[Image:Dead Zone - Sediment.jpg|thumb|200px|right|Sediment from the Mississippi River carries fertilizer to the Gulf of Mexico]] |
|||
Off the coast of [[Oregon Coast|Cape Perpetua, Oregon]], there is also a dead zone with a 2006 reported size of 300 square miles (780 km²).<ref>[http://news.wired.com/dynamic/stories/D/DEAD_ZONE?SITE=WIRE&SECTION=HOME&TEMPLATE=DEFAULT Wired News - AP News<!-- Bot generated title -->]</ref> This dead zone only exists during the summer, perhaps due to wind patterns. |
|||
===Gulf of Mexico=== |
|||
Currently the most notorious dead zone is a 22,126 square kilometre (8,543 mi²) region in the [[Gulf of Mexico]], where the [[Mississippi River]] dumps high-nutrient runoff from its vast drainage basin, which includes the heart of U.S. [[agribusiness]], the Midwest, affecting important [[Shrimp fishery|shrimp fishing grounds]]. This is equivalent to a dead zone the size of [[New Jersey]]. A dead zone off the coast of [[Texas]] where the [[Brazos River]] empties into the Gulf was also discovered in July 2007.<ref>[http://www.bloomberg.com/apps/news?pid=20601109&sid=a4Tb2AFv6CRk&refer=home Bloomberg.com: Exclusive<!-- Bot generated title -->]</ref> |
|||
==Reversal of dead zones== |
|||
Dead zones are reversible. The [[Black Sea]] dead zone, previously the largest dead zone in the world, largely disappeared between 1991 and 2001 after fertilizers became too costly to use following the collapse of the [[Soviet Union]] and the demise of centrally planned economies in [[Eastern Europe|Eastern]] and [[Central Europe]]. Fishing has again become a major economic activity in the region.<ref name="Mee 2006">{{cite news | last = Mee | first = Laurence | title = Reviving Dead Zones | work = Scientific American | date = November 2006 | accessdate = 2006-12-09}}</ref> |
|||
While the Black Sea "cleanup" was largely unintentional and involved a drop in hard-to-control fertilizer usage, the U.N. has advocated other cleanups by reducing large industrial emissions.<ref name="Mee 2006"/> From 1985-2000, the [[North Sea]] dead zone had nitrogen reduced by 37% when policy efforts by countries on the [[Rhine|Rhine River]] reduced sewage and industrial emissions of nitrogen into the water. Other cleanups have taken place along the [[Hudson River]]<ref>[http://www.npr.org/templates/story/story.php?storyId=93619388 'Dead Zones' Multiplying In World's Oceans] by John Nielsen. 15 Aug 2008, Morning Edition, NPR.</ref> and [[San Francisco Bay]].<ref name="sfgate" /> |
|||
The chemical [[Aluminium sulfate]] can be used to reduce phosphates in water.[http://www.dnr.state.wi.us/org/water/fhp/papers/alum_brochure.pdf] |
|||
==Notes== |
|||
{{Reflist}} |
|||
==References== |
|||
* Osterman, L.E., et al. 2004. Reconstructing an 180-yr record of natural and anthropogenic induced hypoxia from the sediments of the Louisiana Continental Shelf. Geological Society of America meeting. Nov. 7-10. Denver. http://gsa.confex.com/gsa/2004AM/finalprogram/abstract_75830.htm Abstract. |
|||
* Pickard, G.L. and Emery, W.J. 1982. Description Physical Oceanography: An Introduction. Pergamon Press, Oxford, 249 pp. |
|||
* Landry, C.A., S. Manning, and A.O. Cheek. 2004. Hypoxia suppresses reproduction in Gulf killifish, ''Fundulus grandis''. e.hormone 2004 conference. Oct. 27-30. New Orleans. |
|||
* Johanning, K., et al. 2004. Assessment of molecular interaction between low oxygen and estrogen in fish cell culture. Fourth SETAC World Congress, 25th Annual Meeting in North America. Nov. 14-18. Portland, Ore. [http://abstracts.co.allenpress.com/pweb/setac2004/document/41689 Abstract]. |
|||
*Taylor, F.J., N.J. Taylor, J.R. Walsby 1985. A bloom of planktonic diatom Ceratulina pelagica off the coastal northeastern New Zealand in 1983, and its contribution to an associated mortality of fish and benthic fauna. Intertional Revue ges. Hydrobiol. 70: 773-795. |
|||
*Morrisey, D.J. 2000. Predicting impacts and recovery of marine farm sites in Stewart Island New Zealand, from the Findlay-Watling model. Aquaculture 185: 257-271. |
|||
== Further reading == |
|||
*[http://news.mongabay.com/2006/0731-osu.html David Stauth (Oregon State University), "Hypoxic “dead zone” growing off the Oregon Coast"] July 31, 2006 |
|||
*[http://www.wri.org/climate/pubs_description.cfm?pid=3803 Suzie Greenhalgh and Amanda Sauer (WRI), "Awakening the 'Dead Zone': An investment for agriculture, water quality, and climate change"] 2003 |
|||
*[http://www.nutrientnet.org NutrientNet], an online nutrient trading tool developed by [http://www.wri.org the World Resources Institute], designed to address issues of eutrophication. See also the [http://pa.nutrientnet.org PA NutrientNet] website designed for Pennsylvania's nutrient trading program. |
|||
*[http://www.greenpeace.org/canada/en/documents-and-links/publications/dead-zones] Reyes Tirado (July 2008) Dead Zones: How Agricultural Fertilizers are Killing our Rivers, Lakes and Oceans. Greenpeace publications. See also: [http://www.greenpeace.org/canada/en/recent/dead-zones] |
|||
*[http://www.msnbc.msn.com/id/4624359/ MSNBC report on dead zones], March 29, 2004 |
|||
*Joel Achenbach, [http://www.washingtonpost.com/wp-dyn/content/story/2008/07/31/ST2008073100349.html?hpid=topnews "A 'Dead Zone' in The Gulf of Mexico: Scientists Say Area That Cannot Support Some Marine Life Is Near Record Size"], ''Washington Post'', July 31, 2008 |
|||
*Joel Achenbach, [http://www.washingtonpost.com/wp-dyn/content/article/2008/08/14/AR2008081401910.html?hpid=topnews "'Dead Zones' Appear In Waters Worldwide: New Study Estimates More Than 400"], ''Washington Post'', August 15, 2008 |
|||
==External links== |
|||
*[http://www.lumcon.edu/ Louisiana Universities Marine Consortium] |
|||
*[http://www.unep.org/geo/yearbook/yb2003/089.htm UN Geo Yearbook 2003 report on nitrogen and dead zones] |
|||
*[http://www.nasa.gov/vision/earth/environment/dead_zone.html NASA on dead zones (Satellite pictures)] |
|||
*[http://www.smm.org/deadzone/top.html Gulf of Mexico Dead Zone - multimedia] |
|||
*[http://www.ncddc.noaa.gov/ecosystems/hypoxia Gulf of Mexico Hypoxia Watch], [[NOAA]]Joel Achenbach |
|||
{{fisheries and fishing}} |
|||
[[Category:Water pollution]] |
|||
[[Category:Aquatic ecology]] |
|||
[[Category:Chemical oceanography]] |
|||
[[Category:Fisheries]] |
|||
[[Category:Ocean pollution]] |
|||
[[de:Umkippen]] |
|||
[[fr:Zone morte]] |
|||
Revision as of 15:52, 3 October 2008
this is the most confusing thin to study evrrr!!!! hhaahhaha im hot =]] hahhah