monitoring change Flashcards
name two examples of chemical inputs into the marine environment
oil spills
runoff
name five examples of human impacts on the environment
- fishing (trawling)
- dredging/mining (e.g. Tauranga harbour)
- terrestrial runoff (important stressor in NZ)
- nutrient loading (causing algal blooms, eutrophication)
- organic enrichment (e.g. salmon farms)
What changes following a disturbance?
- Loss of some or all members of the community
- near-bed hydrodynamics (removal of biogenetic structure, alteration of channel flow)
- food supply (increase if there is organic loading, decrease if the surface organic layer is removed)
- chemical gradients (RPD disturbed)
- sediment grain size (smaller or larger dependent on dusturbance)
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describe macrofaunal succession
less successive diversity the higher the artificial stressors
how is the population growth rate related to the frequency of disturbance?
display the impacts of multiple impacts comparing stable and unstable assemblage
stable- populatoin goes back to initiate number
unstable - populatoin declines over time
what are three potential problems when detecting impacts?
- Many populations sustained by recruits from elsewhere so loss of a species may not be indicative of environmental degradation
- Substantial natural variation in time and space which must be assessed
- Ensuring adequate sampling effort to be certain a species is not present (see previous lecture)
describe a survey design to detect impacts
BACI - Before After Control Impact (common sampling design)
Problematic - temporal variation as two sights might not behave the same way
What are other ways of detecting impacts (not BACI)?
Beyond BACI and MBACI
What is the problem with this curve?
•Very simplistic measure and may miss fundamental changes in assemblage structure
How are changes in diversity measured when studying impacts of disturbances?
•Species richness
–Number of species in a defined unit
–eg. Margalef’s index
- DMg = (S-1)/lnN
- N = total number of individuals
- S = total number of species
- Ignores information on relative abundances
•Indices that include proportional abundances
–eg. Shannon-Wiener diversity index
- pi = proportion of individuals found in ith species
- S = total number of species
species abundance models ABC (go to)
- Abundance Biomass Comparison
- uses all community information
- e.g. impacts of salmon aquaculture
Based on species abundance data, how is the similarity (abundance and composition) among sites analyzed?
Multivariate techniques
commonly used method
involves advanced statistical routines (cluster analysis, multi-dimensional scaling)