Global Change 1
Range shifts tend to move species distributions in this direction.
Poleward
This process explains why corals bleach.
Coral bleaching = disintegration of symbiosis. When the host (coral) is stressed, usually by high temperature, freshwater input, or high UV, they expel endosymbionts.
The two main drivers of movement of phytoplankton & nutrients in pelagic habitats
1. Thermal stratification
2. Water mixing
The two types of sources of ecological disturbance (and give an example!)
1. Physical (e.g. wave impact, sedimentation, debris, chemical changes, tectonics)
2. Biological (e.g. sediment disruption, trampling, abrasion)
The two forms of 'webs' that can be created to understand linkages amongst members of a community.
1. Food webs: map consumer-resource interactions
2. Interaction webs: map all interactions (consumer-resource, mutualisms, interference)
These forms of oil that form the basis of oil spills are more toxic than others.
Light aromatics highly toxic (> heavy fractions)
Reefs change size through a combination of accretion (+) and loss (-). List a process that can contribute to each one.
1. Accretion: biomineralization from corals, coralline algae, sponges
2. Loss: Disturbance, bioerosion, inhibition of reef-builders by non-calcium carbonate builders
With water depth in soft sediment habitats, dependence on detritus changes in this way
Increased dependence with water depth; however, detrital inputs decrease with depth.
The process following a disturbance event, and their two types.
Ecological succession: the non-random patterns of changes in species abundances following a disturbance event.
Types: primary (all species removed), secondary (some species removed)
Two mechanisms that can explain why an ecological interaction may be modified.
Mechanism 1: Change environmental context
Mechanism 2: Change species traits/behavior
Describe the mechanisms controlling species replacements along the tide height gradients in salt marsh habitats.
Physical gradients: salinity peaks in middle zones (freshwater washout at high TH, saltwater washout at low TH), waterlogging/anoxia highest at low TH, lowest at high TH
Competition: competitive intensity increases with tide height (reduced waterlogging stress)
** Depends on coast: Eastern marshes have more species
** opposite to intertidal zones
Describe the bacterial communities in soft sediment habitats as they change with depth (into sediment).
Subsurface sediment anoxic (no oxygen), has chemosynthetic bacteria (fermenters, sulfate reducers, methanogenic bacteria)
The level of disturbance that promotes the highest amount of species diversity, and why.
Intermediate: Low risk of competitive exclusion (high competition, low disturbance), low risk of extinction (low competition, high disturbance)
The process through which one species affects another by changing the density of one or more intermediary species
Interaction chains
An ecological theory to describe changes in the "natural state" of an ecosystem, based on historical knowledge or informal understanding of these systems through time
"Shifting baselines"
Explain the theory behind why some corals show adaptive bleaching, while others don't
Hypothesis = variation in endosymbiont transition mode.
Horizontal transmission = recruitment from environment, zooxanthellae may be less adapted to host (more likely to become parasitic)
Vertical transmission = passed from parent to offspring, zooxanthellae more likely to adapt to host
Describe the mechanisms in hard substrate 'margin' habitats (e.g. the rocky intertidal) that generate patterns of species replacements/diversity.
Upper limits are governed by physiological tolerances (e.g. heat, desiccation), and lower limits set by biotic interactions.
Non-linear systems with multiple stable equilibria can create this type of phenomenon.
Alternative stable states
The reason why highly complex food webs can remain stable.
Low connectance and many 'weak' interactions/few strong ones
Describe two examples of positive interactions in salt marsh habitats.
1. Habitat modification by fiddler crabs: crabs aerate sediment for plants, plants shade crabs from predators
2. Mussels/oysters stabilize sediment, increase nutrient retention by filter feeding for plants, plants provide substrate for mussel settlement
Name the curves on the graph, with respect to seasonal plankton dynamics (see image).
Red = nutrients at surface
Orange = phytoplankton
Green = available sunlight
Blue = zooplankton
The three qualities that characterize a 'disturbance regime'.
1. Intensity (mortality)
2. Extent (spatial structure)
3. Frequency (temporal variation)
A type of predation that moderates species interactions, rather than strictly the amount of resource available.
Apparent competition (Chama and Tegula example).