Lecture 30- Marine ecosystems and seaweeds Flashcards
What are the marine ecosystems like?
-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
How is Australia special in terms of marine plants?
-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
Why is Australia different?
-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
What are the endemic seaweeds in Southern Australia?
-there are distinct floras in each region
What are some interactions between marine plants and animals?
-plants on plants -plants on animals (ascidians) -animals on plants (white stuff on algae, marine animals may look quite plant-like)
How do marine plants structure habitat?
-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
What are the characteristics of seaweeds?
-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
What are the divisions of seaweeds?
-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
How do algal pigments and light attenuation work?
-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
What are the green seaweeds like?
-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%)
What are filametous green seaweeds like?
-massive individual cells -each segment is a cell -also a salad green
What are the leafy and tubular green algae forms like?
-simplest parenchymous forms -common in intertida -respond to freshwater and nutrients= they like it
What are siphonous green seaweeds?
-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
What are calcified greens like?
-coenocytic= no internal walls -important contributors to sediments -largely tropical
What are red seaweeds like?
-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
What are filamentous red seaweeds like?
-this is what the majority of seaweeds are like -basic structural form is uniserate filament
What are some other shapes and colours for red seaweeds?
-yellowish, greenish = then see an accessory pigment that helps it to cope with excess of light -works as a sunscreen
What are coralline red seaweeds like?
-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!
What are brown seaweeds like?
-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
What are filamentous brown seaweed like?
-simplest forms are unbranched filaments
What does Hormosira banksii look like?
-bubbles, has receptacles (the bubbles) and they hold little pits: called the conceptacles (these are the reproductive structures)
What are the algal pigments like?
- 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!)
What are the microalgae? 1. phytoplanton
-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
What are the microalage? (2. attached)
-other microalgae are also attached -benthic or attached to to structures -important colonisers of new substrate
Can algae be pests?
-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
How can non-indigenous algae be dangerous?
-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
What are algae useful for in food?
-food stuffs -wakame= Japanese kelp -sushi -cochayuyo= replacement for meat
What are some other things that algae are useful for?
-extracts for industrial processes: alginates, agar, carrageenans -fertilisers -food additives
How are algae useful to us?
-pregnant cows eat the kelp -health and beauty products -nutritional supplements
What are the impacts of humans on seaweed?
-storm damage has big impact -sun burns them -and introduced species like urchins eat seaweeds= urchin barrens
What are some direct human impacts on seaweed?
-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
What are some indirect human impacts on seaweed?
-if we kill of a predator or part of the food web that can have flow on effects on the seaweed
What are the impacts that humans inflict on seaweed?
-stormwater -agriculture -sewage and industrial effluence
What are some new concerns about seaweeds?
-rising sea temperatures -ocean acidifiction= corals etc. -increasing frequency and intensity of storms (results in damage on the coast!)
