Jackson 2008 Ecological extinction and evolution discussion
University of Puerto Rico Río Piedras Campus College of Natural SciencesDepartment of Environmental Sciences By: Wilmer O. Rivera Course: Coastal Environments Prof. Loretta Roberson, Ph.D. September 6, 2012
Introduction There truly ecological extinction in marine ecosystems? Which factors should be considered in order to discuss a possible ecological extinction in marine systems? Great discussion about the main causes of ecological extinction. NRC- focus in overfishing.
Objectives Evaluation of diverse marine systems: a) Estuaries and Coastal Seas b) Continental Shelves c) The Open Ocean Pelagic Realm d) Coral Reefs • Data review of previous studies of different factors that may be conduct ecological extinction: 1) Exploitation 2) Biological and Chemical Pollution 3) Habitat destruction 4) Climate change 5) Loose of biodiversity (Top-Down, Bottom- Top effects) • Recommendations for better practices in order to reduce the effects of ecological extinction.
Estuaries and Coastal SeasI. Fundy Bay-Case of exploitation A. People have congregated along the coast that produce cumulative effects. 1. Pollution 2. Exploitation 3. Habitat degradation B. Fundy Bay-good example of ecological degradation caused by the effects of exploitation. 1. Hunting and whaling of sea whales, other marine mammals, birds and code 2. Extinction of 3sp. of sea mink. 3. Significant Reductions: a. 7Sp. of Atlantic gray whale b. Salmons, code and other marine groundfish. c. 40% of birds decline severely (3/83sp. hunted to extinction) 4. Regulations don’t increase the number of individuals.
Estuaries and Coastal SeasII. Global patterns-exploitation A. Evaluation of 12 coastal seas-Worst scenarios of overfishing. B. 80Sp. was examined and the results show: 1. Average global degradation range between 39%-(crustaceans) and 91% (oysters-extreme depletion). 2. Mammals, birds and reptiles were severely depleted by 1900 and had declined even further by 1950. 3. Of the 80sp. 7% are extinct. 4. One-half to two-thirds of global wetlands and seagrass beds also have been lost.
Estuaries and Coastal SeasIII. Biological and Chemical pollution A. Biological effects- Introduction of exotic species. 1. In 5 study areas (estuaries)- Average of 117 exotics sp. found. 2. Commonly displaced native animals and plants to become the dominant species. B. Chemical pollution-Water quality due the excess of nutrients from land areas. 1. Eutrophication due to deforestation and agriculture. 2.Runnoff of sediments and inputs of nitrogen fertilizers. 3. Estuaries experience massive nutrient inputs, extended eutrophication, hypoxia and population explosions of microbes.
Continental ShelvesI. Patterns-Exploitation A. Longline fishing and trawling removed 89% of the pristine abundance. 1. Degradation on the structure of sea floor 2. Effects on Biodiversity 3. Effects on large predatory fisches like: cod and haddock (North Atlantic Region). 4. Between 1986-2000 large sharks in the northwest Atlantic were reduced by 40–89%. B. Trophic cascade by the removal of predatory fishes. 1. Increase in the abundance of organism in other trophic level and the decrease of other organisms in low trophic levels by consumption. 2.Example: <cod >shrimp <zooplankton >plankton 3.Top and down control affects ecosystem structure. 4. Trophic cascades is closely linked to the phenomenon of fishing down the food web-(Exploitation of specific species population).
Continental ShelvesII. Eutrophication and dead zones A. Major river systems-Ej. (Amazon and Mississippi-Missouri ), discharge vast amounts of nutrients, into relatively small areas of open coast. B. Formation of vast eutrophic and hypoxic regions comparable with the worst conditions in estuaries. 1. Mississippi delta-Hypoxic zone has doubled in the past 20 years to 20,000km2, and the rate of increase in area. 2. This regions increase in function of nitrogen loading from the Mississippi drainage (Fig.1). 3. Increase the mortality of some species (Shrimps).
Open Ocean Pelagic RealmI. Exploitation A. Ward & Myers (2005), evaluated 19 oceanic fisheries. 1. 12sp. like sharks and tunas decrease. 2. Large predator showed significant decrease. 3. Trophic cascades are present in this systems.II. Climate Change A. Warming- Increase in sea surface temperature 1.Increase the stratification of water. 2. Inhibit upwelling of cooler and denser nutrient rich water from below. a. Drops productivity of oceans-(Ej.Nothern-Pacific) b. Effects on phytoplankton communities. 3.Models predict permanent “El Niño” conditions on sea water. B. Acidification-Increase in solution CO2 1. Effects on all calcareous marine organisms. 2. Measurements have already demonstrated a drop of 0.1 pH units in the oceans.
Coral ReefI. Demise of reef fauna A. Caribbean- Decrease in live coral cover from an average of 55% in 1977 to 5% in 2001. B. Indo-West Pacific- live coral cover still averages 22%, which is about one-half of that in 1980. C. Reef fishes decreases throughout the more than one-half between 1977 and 2003.II. Indirect effects of exploitation A. Overfishing increase macroalgal abundance 1. Effects on water quality 2. Decrease of coral reef and survival a. Increase in dissolved organic matter b. Destabilizes microbial communities on corals and promotes coral disease.III. Ocean warming and acidification A. Warming cause mass mortality of corals-Bleaching B. Low pH can decrease skeletal density and may stop calcification (Low production of colonies).
ConclusionsI. Overview A. The three ecosystems discussed are degraded 1. Overexploitation 2.Nutrient and toxic pollution 3. Climate change B. Some humans activity contribute to this degradation 1. Fisheries 2. Agriculture 3. Ways to obtain energy
RecommendationsI. Sustainable fisheries-Alternatives A. Industrial scale aquaculture of Sp.-low in food webs. B. Improve new regulations to prevent ecosystems degradation (mangrove, estuaries, shrimp farms)II. Coastal Pollution-Alternatives A. Evaluated soil management practices B. Regulations of animal production systems C. Removal of subsidies on fertilizers productsIII. Climate change and acidification A. Moderation of fossil fuels and improve new alternatives energy sources. B. Local protections form overexploitation and pollution C. Local conservation efforts on marine resources.