St. Joseph Bay and St. Andrews Jetties

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# St. Joseph Bay and St. Andrews Jetties - PowerPoint PPT Presentation

St. Joseph Bay and St. Andrews Jetties. Plot and Transect Density Sampling. Plot Sampling Ten 1m 2 quadrats Belt Transect Sampling Two 10m long transects Counted urchins in an area 0.5 m on either side of the transect = total of 10 m 2 sampled per transect. 1 m. 10 m.

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### St. Joseph Bay and St. Andrews Jetties

Plot and Transect Density Sampling
• Plot Sampling
• Belt Transect Sampling
• Two 10m long transects
• Counted urchins in an area 0.5 m on either side of the transect = total of 10 m2 sampled per transect

1 m

10 m

Plot and Transect Density Calculations
• Di = ni/A
• Di = Density for species I
• ni = Total number of individuals counted for species I
• A = Total area sampled (will be 1 m2 for quadrats and 10 m2 for transects)
• Calculate average density of urchins (#/m2 ) by quadrat sampling and by belt transect methods
• Are they in close agreement?
• If not, why do you think they are different?
Community Structure: Trawling
• Graphical Examination
• Species-Sample or Collectors Curve
• Relative Abundance Curve
• Lognormal Curve
• Species Diversity Indices
• Shannon-Weiner Index (H’)
• Simpson Index (C)
Graphs: Collectors Curve
• Cumulative number of species (Number of new species) is plotted against the number of samples taken

Curve has not become asymptotic. What does this suggest we need to do?

Graphs: Species Abundance (Dominance Density) Curve
• Rank the species based on number collected (1 = most abundant, 2 = next most abundant, etc.)
• Plot abundance on logarithmic scale against the corresponding rank
Graphs: Lognormal Curve
• X-axis is divided into geometric abundance intervals (each interval width is a multiple of 2, so that the scale is the logarithm of the abundance to the base 2)
• Plot number of species having certain abundances against the logarithmic abundance intervals
Species Diversity Indices
• Shannon-Weiner Diversity Index (H’)
• Combines two components of diversity
• Number of species (higher number increases diversity)
• Species evenness (evenness increases diversity)
• The greater the value of H, the greater the diversity
• Simpson Index (C)
• Probability of picking two organisms at random that are different species
• Gives less weight to more rare species and more weight to common species
• Values range from 0 (low diversity) to 1-1/S (S = number of species)
Community Structure Assignment
• Graphs
• Collectors Curve
• Seagrass trawls only
• Species Abundance (Dominance Density) Curve
• Seagrass combined data
• Lognormal Curve
• Seagrass combined data
• Species Diversity Indices
• Shannon-Weiner
• Total collection for seagrass
• Simpson
• Total collection for seagrass
• Answer questions on pg 34 (a and b)
• Also, bonus question on pg 34