Allocation of sampling effort for pelagic variables

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Allocation of sampling effort for pelagic
variables
Siv Huseby and Johan Wikner 1Umeå Marine
Sciences Centre, Umeå University,
Aim Determine the number of samples required for
desired precision of a status value Determine
the allocation of samples between waterbodies,
stations and replicates
Quality factors measured in August
2006 Chlorophyll-a, Phytoplankton biomass,
Bacterial growth, Oxygen, Total- and inorganic
nutrients, Temperature, Salinity Zooplankton,
Bacterial biomass, Carbon dioxide fixation,
Cyanobacteria, Dissolved organic carbon, Humus, pH
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Preliminary result for Chlorophyll-a and Oxygen
Number of measurements required for detecting a
true difference from a class limit with 80
probability.
Variation model random, normal, gradient (Chla
AB4) random, normal (O2 AB1)
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Study area and design
9 randomly selected waterbodies within 4
stratified sub-areas
2 randomly selected stations per waterbody
2 depth, one hose or haul per station
Previous estimates of variation between hoses and
hauls applied
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Spatial variation in a water type
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Distribution of the variability
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Current insights

• Marked difference in magnitude of variation
  between quality factors
• Quality factor dependent models for geografic
  variation should be applied
• 18 sampling stations require a sampling effort
  corresponding to 30 k