Ecology: Lecture 3 Flashcards
What are some examples of aquatic biomes?
Freshwater, estuaries, and marine biomes.
What are estuaries?
they form a barrier between the freshwater systems (rivers) and the marine systems (the ocean).
How do aquatic biomes vary with salinity?
Freshwater has low salinity
Estuaries are med. salinity
Marine has high salinity
What does salinity effect?
Osmoregulation:
- The level of salt in the body
- It can be a big challenge and change the structure of the biomes.
Salinity does what to biomes and how?
Salinity is. factor that structures biomes, separating freshwater from marine biomes.
- It affects physiological systems and other systems.
Examples of animals being in multiple habitats/biomes?
Bull sharks (marine) to rivers
Salmon (freshwater) to marine
Depth is what kind of factor?
Depth is an important structuring factor in the ocean.
What does depth affect?
Depth affects:
- Light levels (deeper = darker)
- Temperature (deeper = colder)
- Pressure
How much light is gone below 200m?
99% of light is gone below 200m.
Different zones of the ocean - distance to shore?
Intertidal: Sometimes exposed to air and other times exposed to water
Neritic: Nearshore
Offshore: Oceanic zone
Different zones of the ocean - depth?
Photic zone: sunlight and photosynthesis occur here. 0-200
Aphotic zone: darker, no photosynthesis occurs here. 200-2000
Mesopelagic zone: 200-1000m deep, the twilight zone
Abyssal zone: Very dark, still som penetration of light. 2000-6000m
Pelagic Zone vs. Benthic Zone?
Pelagic Zone: the water column
Benthic Zone: things are attached here, the “sea floor”
What happens daily?
A large migration daily for marine animals to feed. They come up the water column then down again.
Why do so many feeders swarm skeletons on the bottom?
There is no photosynthesis down:
- Deep sea is therefore limited in food and most productivity occurs much higher up.
- Therefore, when a large amount of food comes down, there is an aggregation of organisms that come to feed.
Benthic vs Pelagic?
seafloor vs water column
photic vs. aphotic?
sunlight vs. no light
Intertidal vs. Neritic vs. oceanic?
shoreline, coastline area, offshore
Zoning in lakes?
Similar zoning!
Distance from shore in lakes?
Littoral zone = air and water depending on the day
Limnetic zone = farther out
Depth in lakes?
Photic = light reaches
Aphotic = no light can reach
Other zones in lakes?
Pelagic = water column
Benthic = lake floor
What is stratification?
How fixed the water column is
What does stratification in lakes control?
Nutrients can be a limiting factor, one thing controlling nutrient availability is stratification.
- It tends to have nutrients circulate by waters mixing vertically.
- Could be stratified (layers that don’t mix).
What is a thermocline?
A thermocline is a zone of rapid temperature change.
- This means that you have a gradient in temperature throughout the water (warm on top of hot).
In the summer - stratification?
Photic zone:
- Warmer
- Oxygen rich
- Nutrient poor
- Less dense
Bottom:
- Cooler
- Oxygen poor
- Nutrient poor
- More dense
Is there thermocline in fall or spring?
No! The water circulates during these seasons.
Thermocline in winter?
Colder on top and warmer on bottom.
Mixing during turnover?
-Oxygen to bottom
- Nutrients are going to the top
Open ocean stratification?
There is a thermocline (seasonal in temperate regions)
- Breakdown in the fall or winter, cycles the nutrients available
Eutrophic?
High nutrients and productivity
- temperate regions (Canada)
Oligotrophic?
Low nutrients and productivity
- tropical regions with no seasons
What are phytoplankton blooms?
A burst in marine productivity.
Shallow water marine habitats?
Are very crowded.
Ex. Intertidal, coral reefs, and kelp forests
Interactions between species?
interspecific interactions
Types of interspecific interactions?
Competition
Mutualism
Predation/Herbivory/Parasitism
Commensalism
Competition?
Fighting for the same resources.
- both have negative effects
Mutualism?
Both species benefit mutually
- both have positive effects
Predation/Herbivory/Parasitism?
One harms and the other benefits
- one has positive and the other has negative effects
Commensalism?
One benefits and the other is neutral
- Hard to find in nature
- One has negative and the other has no effect.
Interactions between species affect?
Negative or positive effects on population growth rate of the other species.
How much space is in the intertidal?
Intertidal is very limited in space and there is a lot of competition in this area.
Interspecific Competitors?
They use the same resources (food or space) and the resource is in limited supply.
Intertidal competition?
space is the limited resource as it is one of the most space limited environments.
Competition for resources leads to what?
- Lower birth rates (b)
- Higher death rates (d)
- Slower population growth (r)
Barnacle Biology?
- Adults live on rocks
- Larvae are free-swimming
Intertidal barnacles in Scotland?
There are two species: Chthamalus and Balanus
What are Chthalamus?
Smaller barnacles that live higher up in the intertidal.
What are Balanus?
Larger barnacles that live lower down on the intertidal.
Why do the two species not overlap?
- They have a different settlement pattern (limited in where they go)
- Unlikely because free-swimming larvae - Each adapted to its own zone?
- Interspecific competition?
Removal experiment 1?
Balanus were removed in one area.
- Chthalamus settled in both experiments
- Chthalamus was nearly gone from the part with balanus at the end.
Conclusion from first experiment?
Balanus excludes Chthalamus from the lower shore.
Removal experiment 2?
Chthalamus was removed in one area
- Balanus settles
- Balanus dies in both environments
Conclusion from second experiment?
Chthalamus does not exclude Balanus
- They die because of drying out (desiccation) which limit the Balanus distribution without competition.
Final conclusions?
- Chthalamus excluded from lower shore by interspecific competition.
- Balanus is excluded from the upper shore by physical factors.
Ecological niches?
The position of a species within an ecosystem. This includes their environmental conditions and food availability, as well as:
- Conditions necessary for its survival
- The role it plays in an ecosystem
What is another way of defining a niche?
The conditions that an organism can survive and thrive in.
Realized niche?
The “observed” niche that it occupies in the wild.
Can be constrained - competition does it.
Fundamental niche?
The range of conditions in which it can survive and reproduce. This is in the absence of biotic factors and competition.
Realized is always….?
Less than or equal to the fundamental niche.
Balanus niche?
Realized = Fundamental
- They grow to their limits
Chthlalamus niche?
Realized < Fundamental
- Due to interspecific competition
Competitive exclusion principle?
- If two species compete for one resource, the better competition will eliminate the other
- Species (competitors) must occupy somewhat different niches in order to both exist.
Competition on coral reefs?
- There is very high species diversity and richness
- Corals and fish and invertebrates all co-exist with one another.
Coral reefs features?
- Shallow water
- Tropics and sub-tropics
- Water temperature is around 18-30 degrees celsius.
Coral reefs are the most threatened habitats on earth?
- Destructive fishing
- Nutrient pollution
- Many other threats also exist
Coral Polyps?
Coral Polyps are small animals that live in colonies.
- Shallow coastal tropical waters have abundant light but are nutrient poor
- Their hard skeleton form physical structure, where coral polyps live in colonies and build up the reefs.
Why do corals need light?
Because they are symbiotic creatures that contain zooxanthellae which are photosynthetic organisms.
What is symbiosis for corals?
Corals are in fact two species (polyps and zooxanthellae) living symbiotically together in direct physical contact.
- They mutually benefit one another.
What are zooxanthellae?
They are photosynthetic eukaryotes (microscopic algae).
- They live inside the polyps
- They are symbiotic colonial organisms that give corals their colours.
What are polyps and zooxanthellae an example of?
They are an example of mutualism, as both species benefit.
- Zooxanthellae have a place to live and get nutrients from them
- Polyps get photosynthesis and can synthesize food for themselves.
How much of the photosynthetic production does the coral take?
The coral takes 90% of the zooxanthellae production to feed the corals.
What does the mutualism do for the corals?
IT creates an efficient loop of natural resources, which is why they do well in nutrient poor environments.
- WELL ADAPTED
Overall benefit of zooxanthellae and polyps?
- Coral polyps ultimately die without zooxanthellae
- Zooxanthellae are more abundant with corals
- Symbiosis allows both to thrive where nutrients are scarce
What does mutualism allow?
Mutualism allows abundant life in low nutrient tropical waters
- Efficient use and recycling of nutrients
What do mutualistic organisms do?
Mutualistic organisms must keep partner happy
- Corals must live in shallow, clear water
- Zooxanthellae give up most of their production
How fast are coral reefs changing?
They are changing faster than any other habitat/environment.
- Coral cover has declined dramatically in many parts of the world.
Caribbean coral cover?
~50% cover in the 1970s
~10% cover in the 2000s
How are corals shifting now?
They are shifting from being coral-dominated to being a macro algae dominated area.
Why are macro algae dominating?
They “choke” the corals and outcompete them for resources, prevention the establishment of corals.
Interspecific competition in corals?
The corals and macro algae compete for space.
- Disturbances (storms, disease, competition) open space on the reef
- open space is occupied by the macro algae
What does the colonization of new spaces depend on?
- Settlement rate
- Growth rate
Settlement rate?
Rate that coral larvae or algal spores
settle onto space
Growth rate?
Rate that colonizing organisms can
grow
What changed in the carribean?
Birth and growth rates influenced by the physical and biotic environment - which changed
Overfishing - carribean?
Decline in large herbivorous fish (parrotfish) which ate away at macro algae to help control them.
- Sea urchins took over as the main herbivore, taking the role of the parrotfish. (Diadema)
Disease - carribean?
In 1983 there was a massive die off of Diadema and macro algae began to take over on some reefs (no grazers were taming the macro algae)
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
Other factors in the carribean?
- Increased coral disease rates
- Sewage and agricultural run-off ->
high nutrient levels enhance
macroalgal (not coral) growth - Warm temperatures (coral bleaching) cause zooxanthellae to be expelled.
Environment affects the outcome of competition?
Mechanism – effects on birth, death, growth rates
Environment – abiotic and biotic
Communities have a complexity of species interactions?
- Interspecific competition
- Herbivory
- Predation
- Mutualism
Redundancy can increase the resilience of a community?
Redundancy: several species have similar roles in a community
Resilience: ability to recover after a disturbance
Management of corals?
- Marine protected areas (herbivorous fish)
- Clean up of nutrient inputs in coastal waters
- Threat of climate change
