Zonation in the Rocky Intertidal

Marine Ecology

Question Set #3

Zonation in the Rocky Intertidal

Download the class data from the website, follow the instructions on the lab handout, and then answer each question below. Support your written answers with results of statistical tests and graphs for each question. Email a file with your graphs in it to Dr. Steele. Make sure it is clear which question each graph refers to.

1. 
   Does species richness (the number of species in each quadrat) differ among the three zones (high, mid, and low intertidal)? If so, where is it highest and where is it lowest? Give the F-ratio, degrees of freedom (df), and p-value from ANOVA; and provide a bar graph of mean species richness (standard error, SE) in each zone.
   

2. 
   Does the density of Tegula funebralis, limpets, anemones (Anthopleura spp.), Chthamalus, or Balanus differ among the 3 zones? Give results from ANOVA (F ratio, df, and P-value) and a bar graph for each species.
   

3. 
   Does percent cover of surfgrass (Phyllospadix spp.), all macrophytes combined (algae + surfgrass), Phragmatopoma, rock, or sand differ among the 3 zones? Give results from ANOVA and a bar graph for each species.
   

4. 
   Do the qualitative answers to questions 2 & 3 change if you use ANOVA instead of a Kruskal-Wallis test? In other words, are some statistically significant differences among zones no longer significant, or vice versa? If so, which ones change?
   

5. 
   Is there a negative correlation between percent cover living organisms (summed) and bare substrate (rock + sand)? Give the results of a test of correlation (r value and P-value) and a graph (a scatterplot).
   

6. 
   Is there any evidence to support the hypothesis that macrophyte cover negatively affects the abundance of barnacles (Chthamalus + Balanus)? Give the results of a regression analysis (r² value and P-value) and a graph (a scatterplot).