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Rocky Intertidal Lab Questions – 2006 As you learned so well in Marine Ecology (Bio 160), the rocky intertidal environment has attracted the best and the brightest of ecologists fascinated by the marked zonation of species occurrences across the gradient of tidal heights. This compressed zonation of species has allowed ecologists to very efficiently test hypotheses posed to explain what environmental and biological processes are responsible for determining the upper and lower boundaries of species ranges. By extension, ecologists have examined the ecological processes responsible for spatial variation in community attributes, including species composition and relative abundance, as well as species richness and diversity. As described in the handout for this lab, the purpose of this lab is to introduce you to the diversity of algae and invertebrates that inhabit the rocky intertidal, expose you to these remarkable patterns of zonation, and learn some of the common methods ecologists use to quantitatively describe the distribution and abundance of species in this habitat. In particular, by using two different spatial sampling designs to estimate the relative cover of species across the intertidal gradient (linear transects vs. 2-dimensional quadrats), we can examine how well the patterns generated by these methods agree with one another. Therefore using these two sampling methods we pose the following questions: 1) How well do the patterns of abundance (percent cover) of common macroalgae and sessile invertebrates generated by the linear point intercept and the quadrat point intercept methods compare with one another? For each section of the linear transect across the tidal gradient and the quadrats included within each of those sections, how would you plot a species abundance to test how well the two measures correspond with one another? 2) How well do the estimates of species richness (i.e. number of species) generated by these two methods compare both across the entire intertidal range and within each of four segments from low to high tidal levels? 3) How do the descriptions of the macroalgae and invertebrate assemblages (i.e. relative abundance of common species) differ among these two sampling methods across the entire gradient and within each of four segments from low to high tidal levels? 4) Based on the above results, what can you say about how different spatial sampling designs (i.e. linear vs. 2-dimensional) influence your description of the intertidal community? 5) What attributes of species might explain why they are distributed the way they are? 6) Based on the above results, can you predict what section of the intertidal Yuri would choose to sunbathe in and why?