lecture 3 ecology Flashcards
aquatic biomes, what is the key to distribution
the key is the levels of salinity. we have fresh (low salinity) – estuaries (mid salinity) and marine (high salinity)
what does the estuaries act as
it acts as a barrier between the fresh water and saltwater. many organisms cannot cross this barrier, however salmon can
what is the depth of the ocean
it is an important structuring factor
what does depth affect
temperature and light levels. (the deeper you go the darker and colder it gets).
what is another thing that separates the ocean
the distance to shore (intertidal, neritic, oceanic)
intertidal
close to shore, between low and high tides – mostly exzposed to air
neritic
near shore zone
oceanic
off shore
depths on the ocean
photic, aphotic, abyssal, pelagic, mesopelagic, benthic, continental shelf
photic zone
99% of the light around this zone, top 200m – where photosynthesis happens, therefore all photosynthesizing organisms live here.
aphoticx zone
1% of light – beyond light, res of the depth.a
abyssal zone
deep deep ocean – very food limited.
pelagic zone
the water column, basically all zones tg
mesopelagic
200-1000m – intermediate, the twilight zone. entire marine food web lives in this zone
benthic
seafloor – corals attached to the floor
continental shelf
shallow region
different zones summary
benthic vs pelagic – seafloor vs water column
photic vs aphotic – light vs no light
intertidal vs neritic vs oceanic – shore vs near shore vs offshore
Lakes – structre
similar to oceans in depth (photic (more shallow than ocean), aphotic, benthic (lake floor), pelagic(water column)). however distance to shore is diff (naming wise) – Limnetic (open lake (far offshore)) – littoral (close to shore line)
what are aquatic environments in terms of nutrients
nutrien limited – not much productivity. `
what does stratification do / describe
it controls the nutrient availability – basically how ‘fixed’ the water column is.
stratified lake – description
layers sitting on top of each other – not much mixing due to differing densities
Lake stratification (summer)
in the summer – we have 2 layers – warm and cold – the warm layer : is photic, photosynthesis occurs, it is oxygen rich but nutrient poor because all the nutrients are being used for photosynthesis– the cold layer is: aphotic, oxygen poor because no photosynthesis and nutrient rich because not as many organisms are present so it is not used up.
why are there two layers in the sumer
because of the thermocline – this is why they dont mix. this is the zone of rapid temperature change, also known as the gradient of temperature. – the warmer water is less dense so it floats ontop of the colder, more dense water.
lake stratification (fall)
the surface water in the lake cools down – thermocline breaks down therefore no more temperature gradient – this means the water at the surface is getting more dense – eventually surface water will get to sae density, or higher as the bottom layer and they will mix – bottom layer brings up nutrients and top layer will bring down oxygen.
lake stratification (winter)
the thermocline will reappear but it will be a different temperature gradient (colder on top then on bottom) – fresh waters max desnity is at 4ºC this is the bottom layer – top layer is frozen at 0ºC
lake stratification (spring)
surface will start warming up until it is the same density as the bottom layer – mixing happens again– and bottom will bring nutrients, top will bring oxygen–
open ocean stratification overview
thermocline rapidly drops off –surface temp = 20ºC bottom = 5ºC – seasonality plays a role – temperature in temperate regions. – thermocline will need to breakdown for nutrients in fall and winter.
eutrophic
high nutrient – high productivity – temperate, seasonal
oligootrophic
low nutrients – low productivity – no thermocline breakdown to re introduce nutrients. – tropical systems
shallow water marine habitats, examples
kelp forest, coral reefs (a lot of species packed in small area), intertidal (barnacles; sometimes exposed to air, sometimes water)
interspecific interactions (between species)
competition, mutualism, predation/herbivory/parasitism, commensalism
competition species 1 and 2
both are negatively affected in terms of population growth rate – each species is competing for the same thing, therefore both will get less of it – consequence is reduced growth rate.
mutualism species 1 and 2
both positively affected in growth rate – two species interact in a way that benefits both of them
predation/herbivory/parasitism species 1 and 2
positive for one, negative for the other win for one species, loss for another - -example is when herbivores graze gass, plus on herbivores (FOOD) loss on grass (negative growth rate)
commensa;lism species 1 and 2
positive on one, and no affect on other – very rare to find in. nature
competitiopn in the rocky intertidal
barnicles live in the intertidal zone
barnicles line in intertidal – explain high, mid, low
`high intertidal – mostly exposed to air, mid intertidal – middle
low intertidal – mostly covered by water
barnicles – what happens in intertidal
crowding happens, barnicles are pushed up against one another because of small strip of habitat
interspecific competitors relative to intertidal
use same resource – competiing for same reosurce (space) – resource is limited in supply
competition leads to .. b..d..r.
lower birthh rates, higher death rates, and slower population growth
barnicle bio
have both male and female sex organs, adults live on rocks, but larvae (early barnicles) are free swimming
chthalamus
smaller, lives higher up the intertidal
balanus
bigger, lives lower down the intertidal
separation between chthlamus possible hypothesis
settlement pattern - -dispersal – thats unlikely because larvae are free swimming so they are able to get anywhere
each adapted to its zone,
interspecific competition – one species preventing the other to live in particular part of intertidal
experiments were condsucted – removeal 1
scraped away balanus in intertidal and compared w control group of balanus.
– mid experiment - chthalamus settled in both areas (cleared and with balanus)
– end experiment – chthalamus nearly gone in balanus crowded area, but persisted in empty, scraped away area. – identified that competition was what was going on – Balanus EXCLUDED Chthalamus as it is a bigger competitor
removeal 2
further up the shore line – scarped away chthalamus, and compared to control group of chthalamus
mid exp – balanus settles
end exp – balanus dies in both areas – concludes that adaptations are also a result for the pattern – Balanus is better suited in more submerged water areas. Chthalamus does NOT exclude Balanus because it is not outcompeting, it is just better adapted to drier environments.
Conclusions of both experiments
both species CAN coexist as long as different exposure to air and water – diff parts of intertidal
– in the lower intertidal – chthalamus is outcompeted by balanus
– in the upper intertidal – balanus is excluded by physical factors (drying out) due to adaptation
what can both balanus and chthalamus occupy then
different niches
what is a niche
set of conditions an organism can survive and thrive in (like bees and pollination) (position of a species within an ecosystem)
there are two types of niches
realized and fundamental
realized nuche
where you see organisms in the wild, – may be constrained by competition (otters in lakes and streams because in larger bodies of water more predators)
ALWAYS ≤ FUNDAMENTAL
Fundamental niche
absence of competion or other biotic factors – range of cxonditions in which it can survive and reproduce (ideal conditions)
ALWAYS ≥ REALIZED
Balanus – terms of realized vs fundamental
R=F – grwoing where it can survive – it is not being constrained by competition
Chthalamus – termins of realized vs fundamental
R<F – due to interspecific competition – could grow further does BUT IS LIMITED due to competition
Competitive exclusion principle
if two species compete for one resource, the bettewr competitor will eliminate the other, if they have same niche, one will go towards extinction.
– species must occupy somewhat different niches,.
Coral reefs introduction (distribution etc.)
very high species diversity, (fishes, corals, invertebrates) distribution – shallow waters, tropics and sub tropics, and temperatures at around 18-30ºC
Coral biology
Corals are formed of polyps– they are restricted to shallow coastal tropical waters – have abundant light but are nutrient poor (oligotrophic) – corals are TWO THINGS living together in symbiosis
what are the two organisms that make up coral (live together)
polyps and zooxanthellae
polyps
small animals that live in colonies – protected by hard calcium carbonate skeleton – the skeleton forms the strcuture of the reef. `
zooxanthellae
photosynthetic eukaryotes (microscopic algae) – give the coral its colour, and gives polyps source of food.
give rough sketch of coral
tentacles, algae within tentacle, little squiggles is the polyps
what is symbiosis a form of
mutualism – interactions between species benefits them both
what are both organisms (polyps and zooxanthellae)) getting out of symbiosis
Polyps: zooxanthellae photosynthesize therefore produce carbohydrates and feeds the polyps (they take 90% of the products)
zooxanthellae: they can live outside the corals, but they choose to live inside because the polyps excrete waste in the form of O2 and N which are nutrients need for more photosynthesis. They also choose to live in corals because it is safer, and keeps them away from predators.
coral reefs are changing
coral cover has decline dramatically in many parts of the world
– carribean ~50% cover in 1970s and now ~10%. in 2000s’
the reefs are switching from reef/coral dominated to macroakgae dominated
what do macroalgae do to dominate
they choke/smother the corals and therefore outcompeting the corals as they grow really fast. (in hiogh nutrient conditions)
intersepcific competition (space) disturbances open space on reef like (diseas, storm, coral predators) and that space is reoccupied by the macroalgae.
thew sepcies that gets to persist dsepends on a few things :
settlement rate – how fast are macroalgae spores coming in, or how fast is the rate that coral larvae settle onto thje space.
growth rate – rate that colonizing organisms can grow
what changed in the carribean?
birth and growth rates influenced by the biotic and abiotic factors
OVERFISHING – decline in large herbivorous fish (parrotfish) – these fish feed on the macroalgae and keeps its abundance down – another herbivore took its role (diadema) (sea urchin) and grazed the macroalgae to limit them – massive die off of sea urchin occurred in 1983(possible due to disease) – then macroalgae bgan to takeover
– without thesew herbivores macroalgae outcompete corals as they are more superior
other factors that might have increased abundants of macroalgae
`increased coral disease rates – tissue loss and discolouration – eventually die off)\
sewage and agriculture run off – high nutrient levels enhance the macroalgal growth NOT coral as coral is adapted to LOWER nutrient environments.
warm temperatures – coral bleaching – polyps expel zooxanthellae because it gets too hot, this means loss of food, will turn white then eventually die.
key points
environment affects the outcome of competioton (abiotic and biotic) – mechanism – effects on bith, deatt, and growth rates.
communities have a complexitiy of species interactions (interspecific competition, herbivory, predation, mutualism `
critical points
rebundancy can increase the resilience of a community
rebundancy
multiple species fulfilling the same role – can lose one species and still be okay
resilience
ability to bounce back / recover after a disturbance has improved
management (our control)
- marine protected areas (herbivore fish)
- clean up of nutrient inputs in coastal wayters
- mitigating threat of climate change.
