Lecture 25- Australia's Marine Environments

Question 1

How much of the Earth’s surface is water?

Answer 1

-70%

Question 2

What is special about blue ring octopuses?

Answer 2

-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

Question 3

What is special Nautilus?

Answer 3

-very ancient -marine environment is ancient

Question 4

What are some examples of interesting adaptations in marine anvrionments?

Answer 4

-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

Question 5

How do humans destroy the marine habitats?

Answer 5

-badly, huge impacts, depletion of fish stock -also unintended impact like trapping turtles in nests (ghost nets)

Question 6

How much of life in the southern oceans is found nowhere else?

Answer 6

-over 80% -Australia’s oceans are unique

Question 7

What is the ocean productivity mostly like?

Answer 7

-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

Question 8

What is productivity?

Answer 8

-the rate at which the primary producers convert sunlight into energy (biomass) -primary producers are those undergoing photosynthesis

Question 9

Why are oceans low in productivity?

Answer 9

-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

Question 10

Why are oceans important?

Answer 10

-ocean is important for transfer of heat, nutrients and carbon -oceans are incredibly important for weather, it drives the climate

Question 11

What are the ocean currents like?

Answer 11

-many currents -e.g. Antarctic circumpolar current

Question 12

What is the Great Ocean Conveyor?

Answer 12

-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

Question 13

What is the Southern Ocean and Antarctic Circumpolar Current special in?

Answer 13

-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

Question 14

What is the Global Conveyor Belt driven by?

Answer 14

-gradients of temperature and salinity

Question 15

What is the warm surface water like?

Answer 15

-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

Question 16

What is cool deep water like?

Answer 16

-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

Question 17

What is wind important for?

Answer 17

-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

Question 18

What is the Coriolis effect?

Answer 18

-the shift of the direction of the movement of wind -different deflection in the north (right) and (left) south hemisphere

Question 19

What is upwelling?

Answer 19

-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

Question 20

What is the role of algal growth in the sea?

Answer 20

-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

Question 21

Where are the upwelling zones in the world?

Answer 21

-the most productive areas in the oceans -red= phytoplankton activity= high productivity= upwelling

Question 22

What happens when upwelling fails? (example: Peruvian anchoveta)

Answer 22

-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

Question 23

What happens when upwelling fails? (example: South African Rock Lobster Fishery)

Answer 23

-South African Rock Lobster Fishery -failure of easterly winds -water warmed up -oxygen depleted -lobster walked up to wave zone to get oxygen

Question 24

What are the currents around Australia?

Answer 24

-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

Question 25

What happens on the Australian West coast?

Answer 25

-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

Question 26

What is the biggest upwelling zone around Australia?

Answer 26

-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

Question 27

What are some more details about Bonney upwelling?

Answer 27

-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

Question 28

What are the penguins that depend on upwelling?

Answer 28

-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

Question 29

What is the current along the East coast of Australia and what are its characteristics?

Answer 29

-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)

Question 30

What are the characteristics of East Australian Current?

Answer 30

-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?

Question 31

What are the effects of climate change on East Australian Current?

Answer 31

-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)

Question 32

What are the Australia’s Marine Areas?

Answer 32

-the marine area of Australia =huge!!!

Question 33

Summary:

Answer 33

-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?