Reef corals in Kaneohe Bay six years before and after termination of sewage discharges
Maragos JE, Evans C, Holthus P. 1985. Reef corals in Kaneohe Bay six years before and after termination of sewage discharges. Proceedings of the Fifth International Coral Reef Congress, Tahiti. 4
Watersheds surrounding Kaneohe Bay were dominated by rural and agricultural use before 1939. Reef coral communities flourished on lagoon reef slopes and were protected from the open ocean by a large barrier reef. After 1939, military dredging and filling, residential development, and population growth occurred, especially in and around the confined southeast bay. As population grew, sewage discharges into the lagoon increased, culminating in the construction of large sewage outfalls in the southeast bay by 1936. After 1965, the scientific community, including Maragos (1972), began to study changes in the lagoon. It was speculated that eutrophication and sedimentation, as a result of urbanization and construction, were the cause of an observed decline in lagoon coral communities in the south lagoon and explosive growth of the green algae Dictyosphaeria cavernosa, which was smothering coral, in the middle lagoon. Reef corals in the bay's northwest lagoon remained abundant and appeared unaffected. Pressure from the public and scientific community compelled the local government and military to terminate large sewage discharges in the southeast lagoon by 1978. Now only a minor amount of sewage is discharged in the northwest lagoon. In 1983 we re-surveyed the lagoon and coral transect site of Maragos (1972) using the same methods. These surveys revealed a remarkable recovery of corals, especially, Porites compessa and Montipora verrucosa, in the southern and middle lagoon and continued high coral abundance in the nothern lagoon. Minor coral species, Pocillopora damicornis and Cyphastrea ocellina, also were more abundant in the lagoon. In contrast, Dictyosphaeria declined greatly except for a minor increase in the northern lagoon. This study and other recent investigations corroborate that sewage was a major stress to lagoon corals and a stimulant to Dictyosphaeria growth. In addition, these studies indicate that the detrimental effects of sewage on corals are generally magnified in confined embayments with restricted circulation. Abstract provided by author.
- Type
- Journal Article
- Authors
- Maragos, J; Evans, C; Holthus, P
- Units
- BUIS
- Keywords
- Coral Reefs, Dictyosphaeria cavernosa, Ecology, Green algae, Human Impact, Kaneohe Bay, Montipora verrucosa, Pollution, Population, Porites compessa, Sedimentation