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ENV100 - Marine, Coastal Systems & Fisheries- Lecture Notes.docx
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Department
Environment
Course
ENV100Y5
Professor
Monika Havelka
Semester
Winter

Description
ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 Lectures #37, 38 & 39 - Marine & Coastal Systems & Fisheries (Contd in Jan 22) Blue Planet • Water makes up 71% the of earth’s surface • Mean depth ~ 3.8 km (absolute darkness) • Oceans (deepwater ecosystems) are extremely poorly studied • NASA’s budget exceeds NOAA’s by 1,600X Ocean water: not just H 2 • 96.5% of oceans is water • There are also ions of dissolved salts in the oceans • Dissolved gas: • Oxygen (photosynthesis, bacterial metabolism, atmospheric diffusion) • Major reservoir for CO2 • Organisms that breathe in the water are getting the oxygen from the water = not true! Organisms (ex: fish) that breathe in the water extract dissolved oxygen gas = they are not breaking down the water chemically to access oxygen. Implications for where organisms are distributed in the ocean. • Gases are vertically stratified (not homogenous) - the amount of oxygen at the surface of the ocean is not the same as the amount of oxygen at the bottom of the ocean → influence on the distribution of organisms & what types of organisms can live in particular places. Ocean water is vertically structured • Vertical variation in: − temperature (thermocline) − salinity (halocline) − density (pycnocline) − cline = zone of rapid transition/ abrupt change • Oceans are very dynamic • Temperature declines with depth Page 1 of 15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 • Image: 80% of the volume of the ocean is really cold.About 18% is in the transitional zone. Organisms living in the deep zone will be different than the ones living in the transitional & surface zone. • Surface water heated by solar energy; colder, saltier water is denser and sinks The ocean has several layers • Temperature stratification varies with latitude − Arctic → low incoming solar radiation − Tropical → warm but deep down in tropical waters, it is very cold. − In the arctic, there isn't much variation in temperature as you go from the surface to the bottom. In tropical waters, there is huge variation in temps as you move from the surface to the bottom. − This has an effect on how water moves around/ the currents drive ocean motion. Ocean layers • Surface Zone: − Warmed by sunlight and stirred by wind; water density is at its lowest  • Transitional Zone: − Thermocline = temperature dropping rapidly↓ − Halocline = salinity is increasing ↑ (generally) Page 2 of 15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 − Pycnocline = density is increasing ↑ • Deep Zone: − Dense, cold, sluggish water − Unaffected by winds, storms, sunlight − Unless there is a seismic change/movement affecting the bottom of the ocean, the organisms at the bottom are mostly unaware of activities that happen near the surface/land. − Bottom of the ocean is very complex/dynamic → mountain ranges, waterfalls etc. • Diagram: The technical name for the shape of a basin is "bathymetry" • There are a lot of nutrients in the cold water at the bottom • Oceans: moderating influence on temperature • Water has high specific heat (capacity for storing heat energy); takes a lot of energy to change water temperature. • Oceans tend to hold their heat & give it back gradually → areas that are close to the ocean have moderate climates (doesn't get really hot in the summer nor does it get really cold in the winter). • Oceans absorb heat in summer; release in winter Page 3 of 15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 − Islands & coastal areas have moderate climates − Vancouver Island has moderate climate year-round. Vertical and Horizontal flows (fig 12.5) • Upwelling = upward flow of cold, deep water where winds blow away from, or parallel to, coastlines. − Offshore winds displaces water on the surface → water from the bottom is flown upward & brings nutrients. This new water which is nutrient rich & cold (holds more oxygen) comes in & feeds the coastal areas. Coastal areas have rich biotas. − Coral Reefs → lots of diversity b/c nutrient-rich waters arrive there. • Downwelling = oxygen-rich water sinks where surface currents come together Surface currents are driven by wind, through friction Gulf Stream − Edinburgh: Latitude: 55° 57' N 1.5°C − Moscow: 55° 46' N −10 °C − Warm water from the Caribbean is being funnelled up to the U.K − Oceans have a huge effect on how cold places are. − Edinburgh is much warmer (from a latitudinal p.o.v) b/c it sits in the Gulf Stream Page 4 of15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 Thermohaline circulation: deep circulation is driven by density − Surface circulation is largely driven by wind patterns. − Thermo = temperature − Haline = salt − Temperature + Salt varies by depth. − Largely driven by density. − Red - surface currents − What happens to salt water on the surface even if it's La Niña and El Niño demonstrate the atmosphere-ocean connection This weather pattern tends to happen during Christmas time → really evident near off-shores of SouthAmerica. • Pic: Normal conditions - upwelling brings cold water to the coast of S. America • Air moves from areas of high pressure to areas of low pressure. Strong winds blowing across the surface of the ocean → water is being pushed along by friction. *Bathtub sloshing ex* • Wind is pushing the water from S. America toAustralia → higher sea-level inAustralia. • This massive pushing of water from S. America toAustralia leads to deficit of water in S. America but before this water goes back to S.Ait gets a strong, cold water upwelling. • This is really good for fisheries b/c this upwelling brings a lot of nutrients & thus fishes aggregate in these areas near the coastline → more fish for fishers! • When this fails to happen, you don't get any fish → El Nino. Page 5 of15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 • Pic: El Niño - trade winds weaken; upwelling fails. • Failure of the trade winds • When normal conditions don't exist. High-pressure wind is not being pushed from one area to another. • Sea-level drops inAustralia → no nutrient-rich upwelling in S.America → fish don't congregate near their shores → no fish for fisherman → economic disaster. El Niño • Equatorial winds weaken • Warm water flows eastward and suppresses upwelling • Alters the weather worldwide • Canada abnormally warm and dry La Niña • Opposite to El Niño • Stronger conditions than usual - pushing more water than in normal conditions. • Massive amounts of water is being pushed toAustralia so S.American coastlines get more cold water than usual. • Canada abnormally cool and wet Impacts on biota El Niño event: − Failure of fisheries (Peruvian anchovy fishery) Page 6 of15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 − Marine mammals & birds suffer − Droughts inAustralia (counting on water to push the precipitation cycle but if normal conditions don't happen then it receives very little precipitation. Some ocean zones support more life than others − Photic zone = top layer supports primary productivity (~70% of surface : ⅓ total productivity) • Algae; diatoms (few plants) → photosynthesis. − Pelagic zone = water, habitats, and ecosystems occurring between the ocean’s surface and floor − Littoral zone = water, habitats, and ecosystems occurring in coastal zones (intertidal) − Neritic zone = between littoral and continental shelf - the shallow area, not affected by tides very much b/c it is always under water. • Around the edge of every shore, there is a zone which is relatively shallow but it is still always submerged. Intertidal zones undergo constant change − Intertidal organisms are adapted to being sometimes submerged and sometimes exposed − Benthic zone = water, habitats, and ecosystems occurring on the ocean floor • It can range from being a rocky substrate to a sandy substrate. Ocean zones • These are the most imp zones to remember! Open-ocean systems vary in their biological diversity • Oceans are also not homogeneous when it comes to diversity. • There is a lot of movement in oceans so defining ocean communities can be tricky. • Nekton = actively swimming organisms • Plankton = floating, drifting organisms − Hostages of the surface & deep-water currents Page 7of 15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 − Shows how currents in the ocean have a really big effect on biodiversity → they're dragging around the base of the trophic pyramid w/ them as they're moving. • Phytoplankton constitute the base of the marine food chain in the pelagic zone − Plankton usually photosynthesize at the surface of the ocean but there is a lot of vertical movement → Plankton are usually at the top during daytime & they sink down during night-time. As they sink, they're available as food for pelagic organisms. Deep water ecosystems • Shallow subtropical and tropical waters • Extremely biodiverse (25% of all marine species) • Weird things about the bottom of the ocean: No light at the bottom of the ocean → so a lot of organisms make their own light → bioluminescence. • There is also a lot of atmospheric pressure → if you brought some of these organisms to the surface, they'd explode b/c they're used to being under a lot of pressure; they've evolved in a high pressure system. • Alot of the fish have huge mouths → b/c there the fish population is small at the bottom so they can't risk their food/survival by having a small mouth & potentially not catching any food. Coral reefs are extremely biodiverse • Corals = colonial organisms (related to sea anemones and jellyfish) • Sessile (as adults): attach to substrate; capture passing food with stinging tentacles. − Float as around as larvae and then they settle & build coral reefs. • Corals are hosts for algae. They sequester/hold them → photosynthesize. • Symbiotic algae called zooxanthallae (photosynthesizers). • Reefs are composed of stony corals • Polyps secrete carbonate exoskeletons; new polyps settle on existing reef • The bigger a coral reef, the older it is. • Coral reefs provide a lot of ecosystem services: − Provide habitat for many species − Protect shorelines − Economically important (tourism, ecosystem services, etc.) Coral reefs are in worldwide decline Page 8 of 15 ENV100 Chapter 13 Notes Jan 17,20 & 22, 2014 − Coral bleaching: response to changes in light level and water temperature − Nutrient
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