2-6 Pollution in the Sea

2-6 Pollution in the Sea - Pollution in the Ocean •...

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Unformatted text preview: Pollution in the Ocean • Chapter 11 • Pages 520-536 • Topic 25 OCEAN POLLUTI ON • Nutrients, pesticides, hydrocarbons, metals and chlorinated hydrocarbons are important sources of pollution • Non-point sources are diffuse – include atmosphere and stream, river run off – hardest to prevent and most difficult to mitigate • About 70% of the human population lives in coastal environments Nutrient pollution • Eutrophication/ human activities has lead to increased nutrients in coastal oceans • Number 1 problem for oceans Oceans may be dying from too much production Nitrogen in coastal waters causes: increasing frequency of harmful algal blooms, loss of seagrass and coral, increased occurrences of hypoxia, reductions in light penetration and profound changes in the composition of plankton, suspension feeder (e.g., oyster) and plant communities Dead zones due to human impact: Figure 11.19 Figure 19.10 Trophic cascades may enhance nutrient effect • I n non-eutrophic water, top predator fish keep the density of small, zooplankton feeding fish low. Zooplankton density is high, and grazing on phytoplankton keep density low • When large fish are removed by overfishing, this trophic cascade increases phytoplankton populations Louisiana’s Dead Zone • A large fraction of nitrogen in fertilizers applied to farmland enters the watershed and, ultimately, the Mississippi River • The Dead Zone could be reduced by decreasing fertilizer application in the mid-west • How do we protect the GOM continental shelf while maintaining farm production in I owa? Other problems • Overfishing – do top-down cascades occur? • Bycatch and fishing/ trawling disturbance – side effects of fishing • I nvasive species – becoming more common • Sediment contamination Sediment contamination • A localized problem – long-lived and difficult/ expensive to “fix” • Sources include industries and spills as well as non-point sources Sediments are a “sink”: • Organic contaminants (hydrocarbons, pesticides, herbicides) are hydrophobic – adsorb to the organic carbon fraction of suspended sediments • Metals adsorb to ligand binding sites on suspended clay particles and humic acid • Particles settle to the seafloor Sediment contamination: • Concentrations of contaminants in sediments may be high, altering biotic communities and creating a human health risk • Many contaminants are long-lived (months-years-decades) in sediment and enter food chains after accumulation into benthic animals I ssues for contaminated sediments: 1) US EPA - legal authority mandated to control/ manage sediments • Sediment-quality triad estimates hazards of contaminated sediments, and determines if risk justifies costly clean up 1. Benthic community monitoring: – Crustaceans are sensitive indicators but deposit-feeding annelids and nematodes are tolerant – Species diversity typically decreases but abundance may go up or down at contaminated sites 2. Sediment chemistry monitoring...
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This note was uploaded on 09/13/2010 for the course BIOL 4262 taught by Professor Stickle during the Spring '10 term at LSU.

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2-6 Pollution in the Sea - Pollution in the Ocean •...

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