Natural Disturbances

Question 1

Physiological Tolerance to the Abiotic Environment

Answer 1

Determines where a species can be found, and under which conditions successful breeding will occur

Question 2

Water Movement

Answer 2

Most easily identifiable in rivers and coastal seas (with solid substratum) // Might be seen as harsh environments, but aquatic organisms rely upon water mobility

Question 3

Physical Disturbances

Answer 3

Are defined relatively, where abnormally larger currents would be a disturbance, or where a ice scour is something species are adapted to in polar regions and thus not a disturbance

Question 4

Biological Disturbances

Answer 4

For example, predation or an outbreak of parasitism

Question 5

Biotic Interactions

Answer 5

The primary determinants of gross community structure in ecological systems

Question 6

Biotic Interactions in Aquatic Systems

Answer 6

The effects of predation and competition are important components, yet are tempered by the underlying abiotic (and particularly physical) environment // ALSO the physical environment creates heterogeneity and disturbance across the range of spatial and temporal scales

Question 7

Drift (in rivers)

Answer 7

Individuals of normally benthic species suspended in the water column and being carried downstream by the current

Question 8

Nocturnal Increase in Drift

Answer 8

A technique to avoid increased predation from being suspended in the water column, since predators can’t see as well

Question 9

Catastrophic Drift

Answer 9

Could be caused by floods or other adverse events like the input of a pollutant

Question 10

Floodplain

Answer 10

The velocity of water is reduced in the floodplain, and organisms can be re-deposited here

Question 11

Hyporheic Zone

Answer 11

A layer of saturated sediments and subsurface water beneath the river channel, may be a refuge during floods/high flow

Question 12

River Channel

Answer 12

Dead zones of flow may occur, where the flow is low enough for vulnerable benthic or swimming species to persist

Question 13

Scales of Refugia

Answer 13

Often at the microhabitat scale, such as within a river stretch, yet may also occur between-habitats, particularly for species with complex life cycles

Question 14

Drought

Answer 14

Direct effects, like shallower pools, disjointed rivers, and increased population density as well as indirect effects, like higher water temperatures and deoxygenation, siltation, and high nutrient levels

Question 15

Disturbance-Dominated Communities

Answer 15

Composed of species among which there are no influential interactions, because physical disturbance is so intense and frequent

Question 16

Competitive Communities

Answer 16

Those governed by a resource which is both limiting and patchily distributed // the first species to colonize a patch may dominate in founder control, or species with slightly different requirements will partition the resource in partitioning competitive communities

Question 17

Predation-Structured Communities

Answer 17

The activity of predators has a significant impact on the numbers of their prey (positive and negative impacts for different populations of the community)

Question 18

What is the nature of many dominant species in stream systems?

Answer 18

Many are omnivores, and trophic levels are often poorly defined

Question 19

What is the major determinant in low-stress environments of disturbance?

Answer 19

Predation will be able to dominate

Question 20

Bioturbation

Answer 20

Local-scale biological disturbance that is the result of species living within the sediment, ingesting and egesting particles or drawing oxygen-rich water down to the depths

Question 21

Disturbance (general definition)

Answer 21

Any discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substratum availability, or the physical environment

Question 22

Why is disturbance important?

Answer 22

It is one of the MOST important ecological processes in the maintenance of diversity by opening up resources for colonization by opportunistic species

Question 23

Intermediate Disturbance Hypothesis

Answer 23

Describes the response of community diversity across gradients of disturbance, with highest diversity occurring at intermediate levels of disturbance, where both opportunistic and climax species flourish

Question 24

Temporal Duration of Disturbance

Answer 24

Pulse (e.g. cyclone or storm), Press (e.g. land reclamation or spoil disposal), Ramp (e.g. climate change)

Question 25

Community Stability

Answer 25

Ability of a community to maintain its structure during a disturbance

Question 26

Resistance

Answer 26

Degree of change in community structure (high resistance if little change // low resistance if much change)

Question 27

Resilience

Answer 27

Amount of time it takes for a community to return to normal

Question 28

Alternative Stable States

Answer 28

If a community can’t return to original state, it’s replaced by a new community structure better resistant to change

Question 29

Dynamic Equilibrium Model

Answer 29

Only strong disturbances can counteract effects of high competition

Question 30

Spate

Answer 30

Rapid and sudden increase in flow rate, aka flooding // can impact benthic sediment and composition, and biota in all levels of water column

Question 31

Direct Results of Drought

Answer 31

Reduced runoff, reduced soil moisture, reduced water levels, reduced stream flow

Question 32

Impacts of Drought

Answer 32

Reductions in habitat space for obligate aquatic fauna, increase in habitat fragmentation, decrease in water quality, increase in water temperature, hypoxia, and salinity (for estuaries)

Question 33

Flow Refuges

Answer 33

floodplains, hyporheric zone, stream channel

Question 34

what does the effect of an extreme flow depend on

Answer 34

magnitude of flow, refuge availability, stream morphology, species traits