. Discovery. Science. 176 DISCOVERY Mayor has made exact determinations of the abund- ance and distribution of the various species of corals b}' tracing a line across the reef from shore to edge and surveying squares of 50 feet along it. In each square the number of heads of coral was counted and classified according to species. A survey of this kind made at Murray Island on the Great Barrier Reef brought out many interesting points. It showed, for instance, that the greatest number of coral heads (belonging to eighteen species) was found about 200 feet behind the Lithothamnion ridge and about
. Discovery. Science. 176 DISCOVERY Mayor has made exact determinations of the abund- ance and distribution of the various species of corals b}' tracing a line across the reef from shore to edge and surveying squares of 50 feet along it. In each square the number of heads of coral was counted and classified according to species. A survey of this kind made at Murray Island on the Great Barrier Reef brought out many interesting points. It showed, for instance, that the greatest number of coral heads (belonging to eighteen species) was found about 200 feet behind the Lithothamnion ridge and about 1,400 feet from the shore, while the greatest number of species occurred on the ridge itself, though the number of colonies is smaller, many being broken off in time of storm. In the middle region of the reef, where growth is easy in the calm water and nutritive conditions good, there is a struggle between the various species for mastery, and one, Seriatopora hystrix, emerges as an undoubted victor, crowding out a number of others. Its zone of dominance is restricted, however, and else-. FIG. 2.—POCILLOPORA GROWTH VARIETIES. where it never occurs. Toward the shore colonies become fewer and fewer with many gaps between, and it is found by experiment that they belong to the hardy species, which will stand exposure to over- heating of the shallow water by the sun and suspended mud or sand from the adjacent shore. These, like some species of Poriks, are very different, in this respect, from the more delicate corals of the middle region and reef edge. Some genera are distributed widely over the breadth of the reef, and in this case there are several species replacing each other, or, as in the genus Pocillopora, one very variable species. The photo- graph here given (Fig. 2) illustrates a colony with massive branches from the reef edge, and a looser delicately branching one from the quieter waters toward the shore, but both belonging to this species. Even more interesting than the
Size: 2285px × 1093px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookleafnumber190, booksponsoruniversityofto, booksubjectscience
