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Marine Dead Zones

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Marine Dead Zones Marine Dead Zones: Case Study # 2 Presented By: Blair Dudeck, September 24, 2010 Materials Included in the Reading Package: 1. World Resources institute, Aqriculture and ‘dead zones’”, http://archive.wri.org/jlash/letters.cfm?ContentID=4283 accessed Sept 22, 2010 2. NOLA.com, “Despite promises to fix it, the Gulf's dead zone is growing”, http://blog.nola.com/times‐picayune/2007/06/despite_promises_to_fix_it_the.html, Accessed 10/20/2010 3. National Ocean Service, “What is a Dead zone?”, http://oceanservice.noaa.gov/facts/deadzone.html Accessed 10/15/2010 4. How Stuff Works, “Should we be worried about the dead zone in the Gulf of Mexico?”, http://science.howstuffworks.com/environmental/earth/oceanography/dead‐ zone1.htm , Accessed 10/15/2010. 5. NOAA, “Hypoxia in the gulf of Mexico”, by Nancy N. Rablais, Louisiana Universities Marine Consortium, http://www.csc.noaa.gov/products/gulfmex/html/rabalais.htm Accessed 10/16/2010 6. Environmental Chemistry aglobal perspective, “10.2 Two‐Variable Diagrams‐pE/pH Diagrams”, by Gary W.vanLoon, Stephen J. Duffy, 2008, 7. Science News, “Ocean 'Dead Zones' Trigger Sex Changes In Fish, Posing Extinction Threat”, http://www.sciencedaily.com/releases/2006/04/060402220803.htm, Accessed 10/17/2010 8. DAILY NEWS, “UBC professor wins award for developing phosphorus recycling technology”, http://www.solidwastemag.com/issues/story.aspx?aid=1000385128, Accessed 10/15/2010 • Ecosystem thresholds with hypoxia, affects on biochemistry”. Daniel J.Conley, Jacob Carstensen. Assessed sept 15/2010 • Answer Guide to Environmental Chemistry 2nd edition, by Nigel J Bunce, Accessed sept 21/2010 [1] Distribution of Dead zones across the globe [2] Table 1: Marine dead zone Definitions Hypoxia An queues environment with dissolved oxygen levels in the range between 1 and 30% saturation or less than 2‐3 ppm Anoxic An aquatic system lacking dissolved oxygen (0% saturation) Major Nutrients Phosphate, Nitrate [3] What is a Marine Dead Zone? "Dead zone" is a more common term for hypoxia, which refers to a reduced level of oxygen in the water (crabs killed by from lack of oxygen and toxins resulting from hypoxia.) In the Gulf of Mexico ( as other hypoxic zones the world over) Less oxygen dissolved in the water is often referred to as a “dead zone” because most marine life either dies, or, if they are mobile such as fish, leave the area. Habitats that would normally be teeming with life become, essentially, biological deserts. Hypoxic zones can occur naturally, but scientists are concerned about the areas created or enhanced by human activity. There are many physical, chemical, and biological factors that combine to create dead zones, but nutrient pollution is the primary cause of those zones created by humans. Excess nutrients that run off land or are piped as wastewater into rivers and coasts can stimulate an overgrowth of algae, which then sinks and decomposes in the water. The decomposition process consumes oxygen and depletes the supply available to healthy marine life. Dead zones occur in many areas of the country, particularly along the East Coast, the Gulf of Mexico, and the Great Lakes, but there is no part of the country or the world that is immune. The second largest dead zone in the world is located in the U.S., in the northern Gulf of Mexico.1 [4] Hypoxia occurs from late February through early October, nearly continuously from mid‐May through mid‐September, and is most widespread, persistent, and severe in June, July, and August. Hypoxic waters can include 20 to 80% of the lower water profile between 5 and 30 m water depth, and can extend as far as 130 km offshore. Throughout its distribution, the impact of hypoxic bottom waters is exacerbated by the release of toxic hydrogen sulfide from sediments (Harper et al., 1981, 1991).2 Basic Chemical Reaction: Removal of dissolved oxygen: Bio Mass ‐ + {CH2O} + O2(aq) HCO 3(aq) + H (aq) Inputs of dissolved oxygen: hѵ + Chlorophyll O2(aq) ↑ Mixing of water e.g. waves O2 (aq) ↑ [5] Relevant pE vs. pH Graphs: Dead Zone Formation: Majore Nutrients (P,N Rivers, Nutrients Rivers Coastal ect) spread on Streams, Consume Seas field + sewage Drainage (eg The d by Alge Ditches Mississippi) Rises in Massive Organism Populaons seasonal die off Massive Amounts of s which of Higher of algi Algae Bioc Waste Feed on Organisms exacerbated Blume Decompose Algae Die (eg Krill) Most of the dissolved O Hypoxia Marine life Marine Dead 2 leaves if it used up in Zone O2(aq) < 2‐3ppm can or dies decompsiton [6] Major Causes for the Gulf of Mexico dead zone: Oxygen depletion results from the combination of several physical and biological processes. In the Gulf of Mexico, hypoxia results from the stratification of marine waters due to Mississippi River system freshwater inflow and the decomposition of organic matter stimulated by Mississippi River nutrients. As a general rule, the nutrients delivered to estuarine and coastal systems support biological productivity. Excessive levels of nutrients, however, can cause intense biological productivity that depletes oxygen. The remains of algal blooms and zooplankton fecal pellets sink to the lower water column and seabed. The rate of depletion of oxygen during processes that decompose the fluxed organic matter exceeds the rate of production and resupply from the surface waters, especially when waters are stratified. Stratification in the northern Gulf of Mexico is most influenced by salinity differences year‐round, but is accentuated in the summer due to solar warming of surface waters and calming winds. Following a fairly predictable annual cycle beginning in the spring, oxygen depletion becomes most widespread, persistent and severe during the summer months. Other Chemical Effects: As the concentration of dissolved oxygen drops in the hypoxic dead zone the pE also drops resulting in the reduction of chemical species such as sulfate (a none toxic compound) to ‐ Hydrogen sulfide (H2S) and hydrosulfide (HS ) which are highly toxic compounds. The expression of these species results in further harm to the ecosystem and the wild life which inhabit it. [7] Ocean 'Dead Zones' Trigger Sex Changes In Fish, Posing Extinction Threat: Oxygen depletion in the world’s oceans, primarily caused by agricultural run‐off and pollution, could spark the development of far more male fish than female, thereby threatening some species with extinction, according to a study published on the Web site of the American Chemical Society journal, Environmental Science & Technology. The study is scheduled to appear in the May 1 print issue of the journal. The finding, by Rudolf Wu, Ph.D., and colleagues at the City University of Hong Kong, raises new concerns about vast areas of the world’s oceans, known as "dead zones," that lack sufficient oxygen to sustain most sea life. Fish and other creatures trapped in these zones often die. Those that escape may be more vulnerable to predators and other stresses. This new study, Wu says, suggests these zones potentially pose a third threat to these species — an inability of their offspring to find mates and reproduce. The researchers found that low levels of dissolved oxygen, also known as hypoxia, can induce sex changes in embryonic fish, leading to an overabundance of males. As these predominately male fish mature, it is unlikely they will be able to reproduce in sufficient numbers to maintain sustainable populations, Wu says. Low oxygen levels also might reduce the quantity and quality of the eggs produced by female fish, diminishing their fertility, he adds. In their experiments, Wu and his colleagues found low levels of dissolved oxygen — less than 2 parts per million — down‐regulated the activity of certain genes that control the production of sex hormones and sexual differentiation in embryonic zebra fish. As a result, 75 percent of the fish developed male characteristics. In contrast, 61 percent of the zebra fish spawn raised under normal oxygen conditions — more than 5 parts per million — developed into males. The normal sex ratio of zebra fish is about 60 percent male and 40 percent female, Wu says. [8] What is Being Done: The University of British Columbia's Dr. Donald S. Mavinic, a world expert in wastewater treatment, is to receive one of Canada's most distinguished innovation awards, the Ernest C. Manning Awards Foundation recently announced. Mavinic, a civil engineering professor and entrepreneur, will receive the $25,000 Dave Mitchell Award of Distinction for developing a unique technology to turn pipe‐clogging and polluting phosphorus compounds in wastewater into environmentally friendly fertilizer. His innovation turns a costly problem into a valuable product while addressing major environmental concerns. The dead zone‐inducing phosphorus pollution of natural waters is one of the most significant environmental challenges facing the planet. Yet phosphorus is also a dwindling resource that food crops can't grow without. Ostara's Pearl Nutrient Recovery Process rescues phosphorus from sewage sludge, recycling the would‐be pollutant as the environmentally friendly fertilizer, Crystal Green. Mavinic worked out the chemistry and engineering for the phosphorus recovery system with his research associate Frederic Koch and graduate students at the University of British Columbia. Mavinic also helped spin‐off the technology to Ostara Nutrient Recovery Technologies, Inc., the company that markets the Pearl Nutrient Recovery Process and Crystal Green fertilizer around the world. A single Pearl reactor can produce more than 500 kilograms of high quality fertilizer per day, while saving wastewater treatment plants about $100,000 a year in cleanup costs to get mineral buildup out of pipes and equipment. Removing the phosphorus from wastewater also keeps it out of rivers, lakes and oceans where it can wreak ecological havoc. "Ostara's technology not only helps to solve a major challenge faced by wastewater treatment facilities and communities around the world, but also serves an important role in protecting our natural waterways for future generations," says Robert F.
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