Shulte chose several areas in the lower chesapeake bay as his experimental sites. at each site, he constructed artificial reefs of two different heights. he also left portions of each site unrestored to serve as points of comparison. oysters were allowed to colonize the reefs and the unrestored bay bottom safe from harvesting. his hypothesis was that oysters would survive better in the plankton-rich upper waters away from the smothering sediments and hypoxic waters of the bay bottom. a) reef type is the independent variable. b) adult oyster density is a dependent variable. c) spat density is a dependent variable. d) high-relief and low-relief reefs are treatments.