Lecture 30- Marine ecosystems and seaweeds

Question 1

What are the marine ecosystems like?

Answer 1

-have subtidal, intertidal and spray areas -different things living in each -then the water column is on top of sediments or rocky reef or coral reef (type of substrates) -the place in the ecosystem determines what plants are there -seaweeds are abundant on rocky reefs -on coral reefs have microalgae zooxanthellae that are extremely importants

Question 2

How is Australia special in terms of marine plants?

Answer 2

-high levels of endemism among marine macroalage in S. Australia -greatest diversity and biomass of seagrasses in world (a lot in Western Australia) -mangroves at highest latitude in world

Question 3

Why is Australia different?

Answer 3

-continental drift: timing of Australian/Antarctic separation -ocean currents, the warm polwards-flowing current on west coast! that is unusual! (louwen current)= allows warmer water to extend their range far further south than in other land masses -sea temperature: fluctuating through geological time, varying spatially in modern times -shape of southern hemisphere land masse

Question 4

What are the endemic seaweeds in Southern Australia?

Answer 4

-there are distinct floras in each region

Question 5

What are some interactions between marine plants and animals?

Answer 5

-plants on plants -plants on animals (ascidians) -animals on plants (white stuff on algae, marine animals may look quite plant-like)

Question 6

How do marine plants structure habitat?

Answer 6

-like Hormosira banksia -there is nothing like it in Northern hemisphere -provides shelter in the intertidal zone, determines what lives on that patch of the reef -plants provide food and provide habitat, hiding places -many interactions

Question 7

What are the characteristics of seaweeds?

Answer 7

-mostly simply constructed, mostly photosynthetic, plant-like organisms and their close relatives -marine macroalgae -no flowers, no roots (have holdfasts instead, do not intake any nutrients), no leafy shoots -generally no sophisticated tissues for transport of nutrients or storage products

Question 8

What are the divisions of seaweeds?

Answer 8

-Greens (chlorophyta (4 classes) sea lettuce) -Browns (Phaeophycaea, kelps) -Reds e.g. nori -the divisions are based on the mix of pigments but beware they do not have to be the colour that the name suggests

Question 9

How do algal pigments and light attenuation work?

Answer 9

-the first colours that disappear are red colours -each algae have appropriate pigments to capture the wavelengths that are available in the depths that they live in -some function best at red end of the spectrum and others on the blue end of the spectrum

Question 10

What are the green seaweeds like?

Answer 10

-Chlorophyta: mostly unicellular and freshwater -about 10% of those are macroscopic and marine and those we call seaweeds -the pigments: chlorophyll a, b, beta-carotene and others -green seaweeds most diverse in tropics -at least 125 seaweed species in southern Australia= 45 species are endemic (35%)

Question 11

What are filametous green seaweeds like?

Answer 11

-massive individual cells -each segment is a cell -also a salad green

Question 12

What are the leafy and tubular green algae forms like?

Answer 12

-simplest parenchymous forms -common in intertida -respond to freshwater and nutrients= they like it

Question 13

What are siphonous green seaweeds?

Answer 13

-weird forms -no internal cell walls, one oozing mass of cytoplasm, almost like one cell -Caulerpa (60-70 species), can grow in soft sediments which is very unusual! -Codium: over 50 species, colourless internal coenocytic siphons -most seaweeds need a hard substrate

Question 14

What are calcified greens like?

Answer 14

-coenocytic= no internal walls -important contributors to sediments -largely tropical

Question 15

What are red seaweeds like?

Answer 15

-Phylum Rhodophyta -interesting branching -pigments: chlorophyll a, alpha and beta carotenes, phycobilins + others -mainly marine -about 4100 species in 675 genera -many endemic species in Australia: 70-80% species, over 30 genera and at least 5 entire families

Question 16

What are filamentous red seaweeds like?

Answer 16

-this is what the majority of seaweeds are like -basic structural form is uniserate filament

Question 17

What are some other shapes and colours for red seaweeds?

Answer 17

-yellowish, greenish = then see an accessory pigment that helps it to cope with excess of light -works as a sunscreen

Question 18

What are coralline red seaweeds like?

Answer 18

-calcified -articulated or encrusting -some are free living -major structural components of coral reefs, act as glue, help holding the coral structure together when in wave action -fossil record!

Question 19

What are brown seaweeds like?

Answer 19

-class Phaeophycaeae -these are the large ones! the ones that form the kelp forests and create a completely different environment! -chlorophylls a and c, beta carotene, fucoxanthin + others -nearly all marine -over 1500 species in about 265 genera -Southern Australia over 235 species in 105 genera= about 60% endemic

Question 20

What are filamentous brown seaweed like?

Answer 20

-simplest forms are unbranched filaments

Question 21

What does Hormosira banksii look like?

Answer 21

-bubbles, has receptacles (the bubbles) and they hold little pits: called the conceptacles (these are the reproductive structures)

Question 22

What are the algal pigments like?

Answer 22

• 3 groups of seaweed distinguished by the pigments = summary of pigments in each type
• all have chlorophyll a, distinguished by presence of chlorophyll b or c, carotenes and fucixanthin and phycobilins (in red= can photosynthesize in deep water, =200m depth!)

Question 23

What are the microalgae? 1. phytoplanton

Answer 23

-these are not seaweeds, microsocpic algae are extremely important for us as well -the phytoplankton= basis for most marine food webs -provide about 1/2 of the planet’s oxygen -photosynthetic action is also responsible for storing some of the CO2

Question 24

What are the microalage? (2. attached)

Answer 24

-other microalgae are also attached -benthic or attached to to structures -important colonisers of new substrate

Question 25

Can algae be pests?

Answer 25

-yes - can be a pest, not good for us -they are good first colonizers= on boats etc. -commercial shipping particularly,= fouling organisms -on beaches, structures and in the water

Question 26

How can non-indigenous algae be dangerous?

Answer 26

-they can be dangerous -japanese kelp! -displaces native kelps, and fronts die off during summer and the animals that live there are exposed and negatively impacted -dinoflaggelates= it can produce toxins, can damage fish tissue and gets into shellfish and when we eat it and get sick

Question 27

What are algae useful for in food?

Answer 27

-food stuffs -wakame= Japanese kelp -sushi -cochayuyo= replacement for meat

Question 28

What are some other things that algae are useful for?

Answer 28

-extracts for industrial processes: alginates, agar, carrageenans -fertilisers -food additives

Question 29

How are algae useful to us?

Answer 29

-pregnant cows eat the kelp -health and beauty products -nutritional supplements

Question 30

What are the impacts of humans on seaweed?

Answer 30

-storm damage has big impact -sun burns them -and introduced species like urchins eat seaweeds= urchin barrens

Question 31

What are some direct human impacts on seaweed?

Answer 31

-e.g. Hormosira banksii -trampling on the bubbles -they need bubbles to prevent desiccation and the trampling adds another stress and cannot deal with it and can have flow on effects

Question 32

What are some indirect human impacts on seaweed?

Answer 32

-if we kill of a predator or part of the food web that can have flow on effects on the seaweed

Question 33

What are the impacts that humans inflict on seaweed?

Answer 33

-stormwater -agriculture -sewage and industrial effluence

Question 34

What are some new concerns about seaweeds?

Answer 34

-rising sea temperatures -ocean acidifiction= corals etc. -increasing frequency and intensity of storms (results in damage on the coast!)