Lecture 26- Diversity of Marine Fauna

Question 1

What are the two main currents going around Australia?

Answer 1

-warm water and nutrient poor

Question 2

How is the sea around Australia unique?

Answer 2

-it straddles many different latitudes -tropical, subtropical etc. -covers a diversity of habitats -has the largest coral reef in the world -and 3rd largest mangrove forest

Question 3

What are the zones in the ocean? -this is surface-wise

Answer 3

• intertidal zone (influenced by water)
• neritic zone (200m in depth)
• oceanic zone (the deep blue)

Question 4

What are the zones in the sea (3D wise) so depth?

Answer 4

• amount of light: photic zone to about 1000m, everything below that where light does not penetrate is the aphotic zone
• deeper part is pelagic zone (deep ocean)
• benthic zone= this is everything that is connected to the bottom

Question 5

What are the types of habitats in the intertidal zone?

Answer 5

-the intertidal zone is a nearshore habitat and is influenced by wave action -have some sort of substrate and can have 3 types: -have rocky shores, sandy shores, mud flats

Question 6

What is the rocky shore like?

Answer 6

-Animals need firm aIachment • sessile (fixed) – barnacle, mussel • use sucCon foot – limpet, snails Grazers and filter feeders

Question 7

What is the sandy shore like?

Answer 7

-don’t have substrate for animals to attach to -Animals burrow easily in the sand -Deposit feeders and filter feeder

Question 8

What are mud flats like?

Answer 8

-Animals either form burrows (infauna) or move over the mud (epifauna) - Deposit feeders and filter feeders -here most drill into the mud

Question 9

What is the subtidal (neritic) zone?

Answer 9

-it is a nearshore habitat, extends all the way to the end of the continental shelf -have warm or cold water -if have warm water = Low nutrients, corals dominate, form complex habitat for animals to live in and on. -if have cold water = high nutrients Kelp (macroalgae) dominates; provides shelter and habitat for fauna; more phytoplankton and zooplankton in water .

Question 10

What is the global distribution of coral reefs and kelp forest?

Answer 10

-kelp and coral are limited by temperature

Question 11

What are sea grass beds like?

Answer 11

-it is a subtidal (neritic) zone nearshore habitat -Sea grass beds: -Found at all latiudes Important habitat for many species • nursery habitat • feeding ground • shelter -Natural filtering systems for terrestrial inputs, filters the inputs

Question 12

What are the offshore environments?

Answer 12

-pelagic zone and benthic zone

Question 13

What is the pelagic zone like?

Answer 13

• photic zone: <150m, enough light for plants • so have lot of phytoplankton: microscopic drifting plants (algae) • zooplankton: tinny dribing animals that feed on phytoplankton -all are highly susceptible to currents -nekton: all the fishes, squid, manta rays, etc. that feed on zooplankton; active swimmers (not drifting) …and the predators that feed on smaller fish

Question 14

What is the benthic zone like?

Answer 14

• benthos = “bottom”, it can be on the: continental shelf: <200 m, the slope • or can be abyssal=extremely deep (up to 11km!), no light, freezing temperatures, and immense pressure

Question 15

What is the angler fish like?

Answer 15

-lives in the abyssal benthic zone, the deep ocean -has little appendage that has a bioluminescent properties that attracts prey -males are 1/100 size of the female -angler fish males attaches itself to the female permanently, becomes part of the female

Question 16

What is the viper fish like?

Answer 16

-lives in the abyssal benthic zone, the deep ocean -huge jaws and teeth -can eat large things

Question 17

What are some more examples of deep benthic zone fauna?

Answer 17

-gulper eel: huge jaw, can eat fish much larger than itself -bioluminiscent jellies -blob fish= has vestigal skeleton, the depth keeps its shape -dumbo octopus= has ear like flaps, one of the deepest occurring octopi

Question 18

What are the Chordata in the Australian sea?

Answer 18

• occur in abundance, turtles, sharks etc…

Question 19

What are the marine animal phyla in Australia?

Answer 19

• Porifera: Sponges • Cnidaria: Corals, Hydroids • Annelida: Polychaetes (segmented worms) • Arthropoda: Crustacea e.g. crabs • Mollusca: Gastropods e.g. snails, cowries, seaslugs Cephalopods e.g. squid • Bryozoa (Ectoprocta): Lace corals • Echinodermata: seastars, sea cucumbers, sea urchins • Subphylum of Chordata: Urochordata: ascidians (sea squirts or tunicates)

Question 20

What are the Porifera (sponges) like?

Answer 20

-simplest unicellular organisms, single layer of cells, many colours -don’t have anything that could be considered organs -cells are more specialized for some functions but can migrate and do almost everything -feed by sucking in water, eat the plankton, bacteria etc.

Question 21

What are the Cnidaria?

Answer 21

-Corals, Hydroids, jellies, sea anemones -more complex -have stinging cells -occur in two forms= polyps and medusa forms -some occur in both forms but at different stages in their life -corals are massive colonies of little polyps -include box jellies, has lot of poisionous cells

Question 22

What are the Annelida : Polychaetes?

Answer 22

-segmented worms -increased complexity -deposit feeders, burrowers -lot of these in mudflats -have bristle worms, fan worms: have leathery tube and from there extend fans with which they ear -can live in extreme environment

Question 23

What are the Arthropoda?

Answer 23

-the marine ones are usually crustaceans -shrimp, prawns, crabs, lobsters etc. -lot of zooplanktons -some are tiny, some are massive -largest is the japanese tiger crab

Question 24

What are the Molluscs like?

Answer 24

-the most diverse marine phyla -include abalone, octopus, nautilus, muscles, clams… -most molluscs have shells, some have the shell internalized like the octopus -the octopus are very intelligent and can change their colour very quickly, the change involves migration of pigment through the body, very fast! (cephalopods)

Question 25

What are the Bryozoa?

Answer 25

-lace corals -moss animals -they are more complex than corals -live in colonies -each has distinct bodyparts -the colonies are connected and each individual has specific roles -all the individuals are genetically identically, it is via chemical signalling that the jobs are determined

Question 26

What are the Echinoderms?

Answer 26

-the spiny skins -brittle stars, sea cucumbers… -all have a water vascular system -connectd their tube feed to movement

Question 27

What are the Urochordata (ascidians)?

Answer 27

-look a lot like sponges but are our closest relatives -early form of chordate -the larval form has a rudimentary backbone and nervous system -the ascidians then attach and the adult is sessile -have gill slits (also chordate like) -have circular system and looks similar to chordates

Question 28

What are the biogeographical zone of Australia?

Answer 28

• divided according to lattitudes
• have tropical, temperate
• in the tropics: eastern and western tropical zones
• the flora and fauna in each is distinct -eastern and western warm temperate zone -eastern and western cool temperate zone

Question 29

Where is the highest biodiversity?

Answer 29

-in the tropics -the warm temperate zones less and cool temperate zone the least -infux of nutrients in cool temperate (upwelling) means that you can support high biomass not necessarily high diversity

Question 30

Which areas are most diverse?

Answer 30

• Tropical areas e.g. tropical mangrove mudflats more diverse than temperate mudflats • Coral reefs are the most diverse of tropical habitats • Biodiversity Hotspot - “Coral Triangle” - area between Indonesia, Philippines, New Guinea • this applies to many taxa (fishes, corals, molluscs, etc)

Question 31

What is the coral triangle?

Answer 31

• a diversity hotspot
• along the north coast of Australia, PNG and indonesia

Question 32

What is the hypothesis for diversity of the coral triangle? (hypothesis 1, 2, 3, 4)

Answer 32

1. New species may evolve faster in the tropics

Diversity drops as move south and across Pacific

The average geological age of corals increases

New species appear to have arisen faster in the hotspot area

Some evidence from terrestrial systems - shorter generation times, higher mutation rates, faster evolution (is it the same in marine?)

2. • Species have had longer to evolve in tropics

Because the environment has been more constant

3.Zone of high range overlap, Species have evolved in Pacific and Indian Oceans,

Many species brought to Coral Triangle zone via ocean currents,

Low species endemism

4. “Centre of Origin” – Coral Triangle zone has provided many new places for new species to evolve

As sea level has changed many new reefs were born and lost Isolated areas allow new species to arise,

Then colonised other areas

Thus new species arise faster in the ‘hotspot’ area

Question 33

What is the hypothesis for diversity of the coral triangle? (hypothesis 5, 6, 7 )

Answer 33

• these hypothesis look more on communities and their processes -probably a combination of the hypothesis operating in defining diversity
  5. • Communities not at equilibrium Predation, Competition and Disturbance
  6. • Keystone predation:

Keystone predator – disproportionate effect given biomass

• Dominant competitors exclude others during succession
• But, keystone predator removes dominant competitor
• Other species, and more of them, can co-exist
  7. -Disturbance - Productivity Hypothesis
• Disturbances remove dominant competitors
• Allow many species to colonise, if not too frequent
• Productivity also affects competitive outcome – low productivity is less likely to favour competitive dominants

Question 34

What was the experiment about keystone predation?

Answer 34

-experiment in the intertidal zone of northwest coast USA -the mussels can competitively outcompete others on the rocky habitats -the presence of the pisaster makes it possible for other species to occur not just mussels -create disturbance and allow other species to survive

Question 35

What is the intermediate disturbance hypothesis?

Answer 35

• research of coral reefs and the effects of disturbance
• high disturbance is bad, if no disturbance= have one species dominating
• medium disturbance is best!

Question 36

What is the Australian diversity like? (marine)

Answer 36

• Australia has very diverse marine flora and fauna Why should this be, relative to other continents? • Australia has liIle upwelling Upwelling provides high nutrients, high productivity Large food supply leads to fast growth, dense populations But low diversity (few dominant species) • No obvious keystone predators in Australia • Disturbances promote diversity Low nutrients - slow colonisation: greater effect of disturbance? • History and geographic position Long history of independent evolution (like terrestrial fauna) High levels of endemism (>80% of known marine spp.) High levels of taxonomic distinctness in temperate waters

Question 37

Summary?

Answer 37

• Wonderful diversity of marine phyla • Tropical areas: highest diversity • Different hypotheses for diversity paIerns: • Time and opportuniCes for evoluCon • PredaCon • Intermediate Disturbance Hypothesis • Australia: very high diversity – why? • History and global oceanic currents