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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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## PowerPoint Slideshow about ' St. Joseph Bay and St. Andrews Jetties' - serena

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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

• 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?

• Graphical Examination

• Species-Sample or Collectors Curve

• Relative Abundance Curve

• Lognormal Curve

• Species Diversity Indices

• Shannon-Weiner Index (H’)

• Simpson Index (C)

• 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?

• Rank the species based on number collected (1 = most abundant, 2 = next most abundant, etc.)

• Plot abundance on logarithmic scale against the corresponding rank

• 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

• 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)

• 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