Lecture 25- Australia's Marine Environments Flashcards
How much of the Earth’s surface is water?
-70%
What is special about blue ring octopuses?
-has deadliest venom in the world, more than any terrestrial animal -can kill 26 human adults -can kill you within minutes, interferes with muscle contractions, so die of heart failure
What is special Nautilus?
-very ancient -marine environment is ancient
What are some examples of interesting adaptations in marine anvrionments?
-leafy sea dragon= has appendages that hide it in algae, some are for swimming but some only for hiding -neutrobranchs= sea slugs, related to snails, have nice colourful patterns -lace corals, pink and complex -marine habitats are complex -kelp forests around Tasmania -many coral habitats endangered by crowned of thorns sea stars= can eat many coral in particular
How do humans destroy the marine habitats?
-badly, huge impacts, depletion of fish stock -also unintended impact like trapping turtles in nests (ghost nets)
How much of life in the southern oceans is found nowhere else?
-over 80% -Australia’s oceans are unique
What is the ocean productivity mostly like?
-low -terrestrial environment is high -most of marine environments are not very productive -estuaries and reefs are relatively productive thanks to the runoff from land, continental shelf also productive
What is productivity?
-the rate at which the primary producers convert sunlight into energy (biomass) -primary producers are those undergoing photosynthesis
Why are oceans low in productivity?
-in the open oceans even tough there is much light there is a lack of nutrients -that is why in shallower areas you have more productivity -the stuff that grows in the open ocean= get eaten quickly or sink
Why are oceans important?
-ocean is important for transfer of heat, nutrients and carbon -oceans are incredibly important for weather, it drives the climate
What are the ocean currents like?
-many currents -e.g. Antarctic circumpolar current
What is the Great Ocean Conveyor?
-transfer system in the ocean -renewal and transfer system -driven by differences between salinity and temperature -important for moving nutrients and water around the planet -carries heat in the world’s oceans, helps moderate the world’s climate, the heat is transferred to the poles -takes 1000 years to complete
What is the Southern Ocean and Antarctic Circumpolar Current special in?
-unique because only place on earth where ocean circles the globe -provides means of water exchange between Atlantic, Pacific and Indian oceans= the only way -collects nutrients in deep water, transports it northward -major site of carbon sequestration= sinking of carbon, trapped in the ocean -opened up when Gondwana broke up -Gulf stream is part of this, so part in heating up places plus nutrients -also part of the conveyor belt
What is the Global Conveyor Belt driven by?
-gradients of temperature and salinity
What is the warm surface water like?
-sun heats the surface (esp. in tropics) -warm water less dense, stays on top -lots of light= lots of plants (phytoplankton) grow -but they use up the nutrients -when they die, the plants and animals sink
What is cool deep water like?
-100-200 m -saltier and denser -no light -bacteria break up dead matter that sinks from surface -this release the nutrients -so cool deep water accumulates nutrients
What is wind important for?
-also drive global circulation patterns -atmosphere convection cells -at the equator the hot air rises and cools, descends at about 30 degrees latitude -these winds go to the equator -Trade winds= easterly direction -winds close to the poles go towards the poles
What is the Coriolis effect?
-the shift of the direction of the movement of wind -different deflection in the north (right) and (left) south hemisphere
What is upwelling?
-when easterly trade winds blow over the West coasts of continents, they blow surface water away and cold water from below rises up, rich in nutrients -higher productivity
What is the role of algal growth in the sea?
-light and nutrients produce algal growth -alage provide food for many animals =phytoplankton: filter feeders (e.g. mussels), fish (anchovies, sardines) =attached algae: herbivores (e.g. urchins -these for basis for food chain for predators, including humans
Where are the upwelling zones in the world?
-the most productive areas in the oceans -red= phytoplankton activity= high productivity= upwelling
What happens when upwelling fails? (example: Peruvian anchoveta)
-Peruvian anchoveta -was largest fishery in the world -catch at peak: over 12M tonnes a year -1972: failure of of easterly winds (El Nino) -cool, nutrient rich waters not brought up to surface -low phytoplankton productivity -fishery collapsed -took over 10 years to start to recover
What happens when upwelling fails? (example: South African Rock Lobster Fishery)
-South African Rock Lobster Fishery -failure of easterly winds -water warmed up -oxygen depleted -lobster walked up to wave zone to get oxygen
What are the currents around Australia?
-in the north the South Equatorial current -south the Antarctic Circumpolar current (important in the conveyor belt and in navigation) -Leeuwin current -have no west coast upwelling
What happens on the Australian West coast?
-warm water flows north of Australia, then down the West coast as the Leeuwin current -warm current -there is no upwelling along the west coast
What is the biggest upwelling zone around Australia?
-south coast -called Bonney upwelling -cold flinders current flows up the west coast of tasmania towards SA -during summer, SE winds blow surface water offshore along the West coast of Tasmania and South coast of Victoria and SA
What are some more details about Bonney upwelling?
-get upwelling of cold water with nutrients -diatoms grow and krill eat them -blue whales come to feed on them, only recently discovered, the whalers of the 1800s missed this one so didn’t hunt there -some of the few Blue Whales left in the World
What are the penguins that depend on upwelling?
-depend on upwelling zones -little penguin (fairy): world’s smallest penguin, feeds on southern coast of Australia, where there is some but not much upwelling -can contrast it with South America’s Humboldt penguin: much larger, feeds along the west coast of S. America where there is strong upwelling, which means many fish
What is the current along the East coast of Australia and what are its characteristics?
-East Australian Current -driven largely by winds blowing across the Pacific and hitting the Australian continent -winds push surface water against Australia’s east coast -water then flows south along the coast -important mode of dispersal for many tropical species (planktonic larvae are transported this way)
What are the characteristics of East Australian Current?
-water is warm and nutrient-poor -low productivity= clear water (GBR) -but some mixing of deep water onto continental shelf due to tides -also some nutrient runoff from the land -so how can the great barrier be so biologically rich?
What are the effects of climate change on East Australian Current?
-warm water from north spreading further south, even to Tasmania -water along southern NSW are warming faster than all the other places in the ocean -tropical and subtropical species are being carried to new habitats where some are having major impact on local ecosystems (urchins impact on kelp forest, eat the seedlings so the kelp won’t grow tall)
What are the Australia’s Marine Areas?
-the marine area of Australia =huge!!!
Summary:
-oceans are low in productivity compared to terrestrial habitats -but they are dynamic, interconnected systems that drive global climate patterns -role of Southern Ocean and Antarctic Circumpolar Current in global circulation patterns -How does upwelling occur? And why is it important for fauna? -How are Australia’s currents unique?
