Ecology Lesson 3 Flashcards
Salinity
How salty the water is
Levels of salinity
Low: Freshwater
Middle: Estuaries
High: Marine
Osmoregulation
What freshwater has no problem doing. It’s regulating the level of salt in the body. Meaning we can drink the freshwater.
Estuaries
A barrier between freshwater and ocean.
Animals crossing the salinity boarder?
Not many organisms can cross this boarder because you always have to balance the levels of salts in your body, and they all have different ways of doing this depending on what environment you live in. ie. salmon and bull sharks can do this.
Depth affects on ocean structure?
Light levels (no light in deeper)
Temperature (Colder is deeper)
Pressure (higher is deeper)
Intertidal zone
Between low and high tides. Exposed to air and water.
Across ocean zones
Intertidal, neurotic, and oceanic. And continental shelf (it’s shallow).
Vertical ocean zones
Photic, aphotic, abyssal. also mesopelagic.
Photic zone
Where you can see sunlight in the ocean, where photosynthesis occurs. At 200m.
Benthic zone
Anything on the seafloor.
Abyssal Zone
Deep down. Organisms here adapted to intense pressure. It’s very food limited because you can’t photosynthesis.
Important factor in ocean?
Depth and distance to shore
Mesopelagic zone
From 200 to 1000m. The biggest daily migration is the movement from 1000 to 200m to feed in the day.
Benthic vs pelagic
seafloor vs water column
Photic vs aphotic
Sunlight layer vs no light layer
Intertidal vs. neritic vs. oceanic
On shoreline vs close to coastline vs. far out
Differences in ocean vs. lakes
- Has littoral (very close to shoreline) vs. limnetic zone (open lake)
- Photic zone is very shallow.
- They have a lot of sediment so they tend to be quite turbid, so the light attenuates much faster, so it gets darker much faster.
Stratification
How fixed the water column is. Can dictate how much nutrients there are. One water layer sitting on top if another, with no mixing.
Thermocline
Zone of rapid temperature change. Why the layers don’t mix heat gradient.
Photic and Aphotic zones in lakes?
Photic: Warmer (it’s less dense so it floats on the cool water), oxygen-rich (from the photosynthesis), nutrient-poor.
Aphotic: Cooler (more dense), oxygen-poor, nutrient-rich (because there are no organisms using up the nutrients in the same way as the surface).
Lake stratification
In summer the layers don’t mix because the temp differences. Then in fall there is no thermocline because the water is the same density. Then in winter, the thermocline in the opposite direction (warmer at bottom, colder at top). Then in spring there is no thermocline and it mixes, with ramp in productivity. This is in temperate lake, as tropical lakes have different seasons.
Mixing during turnover
Oxygen to bottom, the nutrients to top. Important in terms of recycling the thing needed for photosynthesis. Occurs in fall and spring. The thermocline brakes down.
Open ocean stratification
Photic is 20 degrees and bottom drops to 2 degrees. The saltily affects the density. Has eutrophic and oligotrophic.
Eutrophic
High nutrients and high productivity
Oligotrophic
Low nutrients and low productivity. Mostly in tropics because always have the layer difference.
Photoplankin
Can see the lighter patch of it in NS/ They are patches of productivity with lots of organisms.
Shallow water marine habitats
Kelp forest
Coral reefs
Intertidal
(the last two have lots of species in a small area so has lots of interactions).
Competition
- and -
Mutualism
+ and +
ie. clownfish living in coral reef. Fish there for protection and reef gets fishes waste.
Predation/Herbivory/Parasitism
+ and -
Commensalism
+ and 0
Different intertidal zones
-Splash zone (mostly air with periwinkle snail)
-High Intertidal (barnacles)
-Mid-interidal (mussel)
-Low-intertidal (sea star and mostly water).
Interspecific competitors
Use the same resource and Resource is in limited supply. Intertidal - space is the limited resource.
Competition for resources equals:
* Lower birth rate (b)
* Higher death rate (d)
* Slower population growth (r)
Barnacles
Adults live on rocks. Free swimming
larvae. They are hermaphrodites (both make and female organs).
Intertidal barnacles in Scotland
Chthamalus – smaller, lives higher up the intertidal.
Balanus – larger, lives lower down the intertidal.
They are separated out and don’t overlap.
Possible explanations to why they don’t overlap?
- Settlement pattern (unlikely that they can’t get to certain places)
- Each adapted to its zone?
- Interspecific competition? (one species is preventing the other from living in a specific part).
Removal experiment 1
Experiment in Balanus zone (lower shore). Joseph Cornell scraped away the Balanus in one spot. They looked at removed and present (control). The Chtamalus settles in the removed and not in the present. So that’s competition. Balanus excludes Chthamalus from lower shore.
Removal experiment 2
Experiment in Chthamalus zone
(upper shore) They remove and present Chthamalus. The Balanus settles in but then dies in both. Chthamalus does not exclude Balanus. Dessication (drying out) limits Balanus distribution.
Conclusions from the experiment
Chthamalus excluded from the lower
shore by interspecific competition. Balanus is excluded from the upper
shore by physical factors.
Niche
A set of conditions that an organism can survive and thrive in.
Ecologist niche
Ecological niche – the position of a
species within an ecosystem.
* Conditions necessary for its survival
* The role it plays in an ecosystem
Realized niche
The ‘observed’ niche that it
occupies in the wild. Can be constrained by e.g. competition. R is always less than or equal to F.
Fundamental niche
the range of conditions in which it can survive and reproduce. Can only really get in a lab setting.
Niches with barnacles
Balanus R = F
Chthamalus R < F (due to interspecific competition) Because it could grow further but can’t because of Balanus.
Competitive exclusion principle
If two species compete for one resource, the better competitor will eliminate the other. Species must occupy somewhat different niches to coexist. If niches are the same one will eventually go extinct.
Competition on coral reefs
Very high species diversity (species richness). Corals, fishes, invertebrates etc.
Coral reefs
Shallow water and sunlight.
Tropics & sub-tropics.
Water temperature around 18-30 °C.
One of the most threatened ecosystem on earth because of climate change.
Coral Polyps
Coral polyps are small animals that live in colonies. They form the structure of corals. They are protected by hard calcium carbonate skeletons. Shallow coastal tropical waters have abundant light but are nutrient- poor. They have stinging cell to capture prey.
Why do corals need light?
because of Zooxanthellae
Symbiosis in corals?
Corals are in fact two species (polyps and zooxanthellae) living symbiotically together in direct, physical contact. They benefit from one another. It’s mutualism. Coral polyps ultimately die without zooxanthellae. Zooxanthellae are more abundant with corals. Symbiosis allows both to thrive where nutrients are scarce.
Zooxanthellae
Photosynthetic eukaryotes (microscopic algae) and they are protists. They live in polyps (coral cells) and give the corals the color.
Symbiosis
species living in close physical
association.
How coral polyps benefit from zooxanthellae?
Zooxanthellae photosynthesize
- produce carbohydrates
- feed the corals
Coral takes ~ 90% of production
How do zooxanthellae benefit from corals?
Coral polyp provides a place to live
* (safe from predation)
Coral polyp excretes CO 2 , N, (waste)
* used by zooxanthellae for
photosynthesis
Can live outside coral but choose to live with coral. It’s why corals do well in nutrient poor water.
Mutualism in coral
Allows abundant life in low nutrient tropical waters. Efficient use and recycling of nutrients.
Mutualistic organisms must keep partner happy
* Corals must live in shallow, clear water
* Zooxanthellae give up most of their production
The changing of coral face of reefs
Coral cover has declined dramatically
in many parts of the world
Caribbean
* ~50% cover in the 1970s
* ~10% cover in the 2000s
Switched from coral dominated state to macroalge dominated state. This is because it’s a space limited environment. Macroalgae can out compete coral.
Interspecific coral reefs on coral reefs
Disturbance opens space on reef lake: Storms, Disease, Coral predators. Cause coral death then
Open space is re-occupied by macro algae.
Colonization of new space depends on what?
Settlement rate
* Rate that coral larvae or algal spores
settle onto space
Growth rate
* Rate that colonizing organisms can
grow. The species that grows faster will out compete the other one.
What changed in the Caribbean?
Birth and growth rates influenced by the physical and biotic environment.
Overfishing
Decline in large herbivorous fish (parrotfish). Grazers on coral reefs eat macro algae and control it. But then they are overfished. So then the sea urchin (Diadema) became main herbivore and grazes on macro algae.
Disease
Massive die-off of Diadema then Macroalgae began to take over – on some reefs, because nothing was eating it. no grazers.
Reefs without parrotfish
Many more Diadema, which kept macroalgae small. But after 1983 Diadema die-off, few herbivores to
slow macroalgal growth and reproduction. In the absence of herbivores, macroalgae are superior competitors and outcompete corals, because they grow faster. Reefs with parrotfish are in better shape.
Other coral factors
- Increased coral disease rates. Tissue loss in corals.
- Sewage and agricultural run-off into the water -> high nutrient levels enhance macroalgal (not coral) growth and corals are adapted to low nutrients.
- Warm temperatures (coral bleaching). Waters to warm and get rid of zooxanthellae, so polyps don’t have enough enough food, then coral turn white and can’t survive forever.
Redundancy
several species have similar roles in a community. Redundancy can increase the resilience of a community.
Resilience
ability to recover after a disturbance.
Management of coral reefs
- Marine protected areas (herbivorous fish)
- Clean up of nutrient inputs in coastal waters
- Threat of climate change
What effects the outcome of competition?
The environment
