Difference between revisions of "Sampling"
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'''Baseline studies''': data are collected to define the present state of a biological population or community. They are also called "''one-off''" studies, because by definition, they are not replicated in time. | '''Baseline studies''': data are collected to define the present state of a biological population or community. They are also called "''one-off''" studies, because by definition, they are not replicated in time. | ||
| − | '''Impact studies''': are designed to determine the changes brought about a particular disturbance or stressor by comparing the status of natural or unimpacted biological parameters with their status under unimpacted conditions. | + | '''Impact studies''': are designed to determine the changes brought about a particular disturbance or stressor by comparing the status of natural or unimpacted biological parameters with their status under unimpacted conditions. Green’s <ref> Green, R. H., 1979 Sampling design and statistical methods for environmental biologists. Wiley, New York.</ref> work on impact sampling design was pioneer in the development of impact assessment studies and statistical methods. Since then various authors has discuss the advantages and disadvantages of different impact study designs <ref>Underwood, A. J., 1991. Beyond Baci - Experimental-Designs for Detecting Human Environmental Impacts on Temporal Variations in Natural-Populations. Australian Journal of Marine and Freshwater Research 42: 569-587.</ref> |
| + | <ref>Underwood, A. J., 1992. Beyond BACI: The detection of environmental impacts on populations in the real, but variable world. Journal of Experimental Marine Biology and Ecology 161: 145-178.</ref> | ||
| + | <ref>Underwood, A. J., 1994. On Beyond BACI: Sampling Designs that Might Reliably Detect Environmental Disturbances. Ecological Applications 4: 3-15.</ref> | ||
'''Monitoring studies''': are designed to detect any changes from the present state. By definition, monitoring studies involve reapeted sampling in time. Monitoring programms in marine environments have focused on chemical, physical, and biological parameters, for example detecting microbial contamination of beaches, determining the concentration of potential harmful material on fish, estimating the population abundance of an endagered species inside a marine reserve. | '''Monitoring studies''': are designed to detect any changes from the present state. By definition, monitoring studies involve reapeted sampling in time. Monitoring programms in marine environments have focused on chemical, physical, and biological parameters, for example detecting microbial contamination of beaches, determining the concentration of potential harmful material on fish, estimating the population abundance of an endagered species inside a marine reserve. | ||
Revision as of 16:08, 10 March 2009
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Field sampling programs provide the information needed to determine the status and dynamics of populations and communities and thus are the basis for many kind of research. The physical and biological complexity and dynamism of most marine ecosystems results in high spatial and temporal variability in almost any measured parameter. Sampling methods and procedures need to be carefully analysed and selected so as to take into account this high variability of most marine systems.
The steps in designing a field sampling program include:
- Identifiying the study goals including the questions to be anwered by the study or the hypothesis to be tested.
- Developing and effective and statistically powerful study design.
These steps are followed by selecting study sites, the biological units to be sampled, the sampling design, layaout, and units to be employed, and the type of data to be obtained.
Field sampling studies can be clasified into four categories [1]:
Baseline studies: data are collected to define the present state of a biological population or community. They are also called "one-off" studies, because by definition, they are not replicated in time.
Impact studies: are designed to determine the changes brought about a particular disturbance or stressor by comparing the status of natural or unimpacted biological parameters with their status under unimpacted conditions. Green’s [2] work on impact sampling design was pioneer in the development of impact assessment studies and statistical methods. Since then various authors has discuss the advantages and disadvantages of different impact study designs [3] [4] [5]
Monitoring studies: are designed to detect any changes from the present state. By definition, monitoring studies involve reapeted sampling in time. Monitoring programms in marine environments have focused on chemical, physical, and biological parameters, for example detecting microbial contamination of beaches, determining the concentration of potential harmful material on fish, estimating the population abundance of an endagered species inside a marine reserve.
Pattern and process (ecological) studies: these studies involve describing distribution and abundance patterns of organisms, with the intention of identifying the processes resposible for them. For this, prupose descritive ('mensurative') and experiemntal approaches should be used. [6]
References
- ↑ Kingsford M, Battershill C (1998) Studying temperate environments. Canterbury University Press, Christchurch, New Zealand, 335 pp.
- ↑ Green, R. H., 1979 Sampling design and statistical methods for environmental biologists. Wiley, New York.
- ↑ Underwood, A. J., 1991. Beyond Baci - Experimental-Designs for Detecting Human Environmental Impacts on Temporal Variations in Natural-Populations. Australian Journal of Marine and Freshwater Research 42: 569-587.
- ↑ Underwood, A. J., 1992. Beyond BACI: The detection of environmental impacts on populations in the real, but variable world. Journal of Experimental Marine Biology and Ecology 161: 145-178.
- ↑ Underwood, A. J., 1994. On Beyond BACI: Sampling Designs that Might Reliably Detect Environmental Disturbances. Ecological Applications 4: 3-15.
- ↑ Andrew NL, Mapstone BD (1987) Sampling and the description of spatial patterns in marine ecology. Oceanography and Marine Biology: An Annual Review 25: 39-90
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