. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 36 Our first project was to map the marine environments all around St. John to the 10-fathom curve. The Park Service provided a 10-m vessel with an operator for this survey. We did not realize what an enormous task it was until we started it. St. John is 8 miles long west to east and nearly 4 miles wide at the widest point; it is deeply dissected with bays, so the coast line and that of nearby cays is more than 58 miles long. We finally devised what we called a dive sled whereby a snorkeler could be towed behi
. Atoll research bulletin. Coral reefs and islands; Marine biology; Marine sciences. 36 Our first project was to map the marine environments all around St. John to the 10-fathom curve. The Park Service provided a 10-m vessel with an operator for this survey. We did not realize what an enormous task it was until we started it. St. John is 8 miles long west to east and nearly 4 miles wide at the widest point; it is deeply dissected with bays, so the coast line and that of nearby cays is more than 58 miles long. We finally devised what we called a dive sled whereby a snorkeler could be towed behind the vessel, and by depressing the inclined plane of the sled, could quickly descend and even more rapidly come up by reversing the process. We obtained aerial photos of St. John from the Coast and Geodetic Survey. While Helen consulted the aerial photos, Herb and I alternated in being towed as we zigzaged in transects around the coast reporting the bottom type to Helen. One feature of the photos made our survey much easier. Along most of the coast there is a band of bare sand between the fringing reef and the seagrass beds that showed well on the aerial shots (Fig. 7). Herb and Helen published the survey (Kumpf w and Randall, 1961). I had wondered why the seagrass did not grow adjacent to the reef. At first I thought that the sand near the reef was coarser and more shifting, but samples of sand across the band did not show any difference. Then I saw a parrotfish swim up from the bottom to eat a piece of seagrass that was drifting down. When detached from the bottom, pieces of seagrass float to the surface. In time, small encrusting organisms grow on them and they eventually sink. I then knew the answer. Parrotfishes and other herbivorous reef fishes will not venture far from the shelter of the reef because of fear of predation, so their grazing on the seagrasses is concentrated near the reef. How to show this? I decided to transplant a corrider of seagrass across the ba
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