in the marine habitat and biota of Pelekane Bay, Hawai’i
Pelekane Bay has been subjected to large-scale alterations in the Kawaihae watershed over the last 200 years and the construction of the Kawaihae Harbor in the 1950’s and 1960’s. The goal of this study was to examine long-term changes in the marine habitat and biota by comparing the present abundance, diversity and distribution of marine organisms to those described 20 years earlier in previous studies. Quantitative and qualitative surveys were conducted within Pelekane Bay in the same area as previous studies. A species list and the relative abundance of all species was compiled for all habitats within the bay. In addition, quantitative sampling was conducted on three 50 m transects on patch reefs.
Although the absolute areas of different habitat types within the bay appear to have been stable, there have been striking declines in the abundance of all plants and animals associated with major changes in species diversity and composition since the last surveys in 1976. Seaweeds declined from 13 species to one, invertebrates from 106 to 21, and fishes from 64 to 57 over the intervening 20-year period. Similar declines occurred in the percent cover of live corals, which declined over 84%, and fish density which declined 35%.
Although the causes of these changes cannot be ascertained directly from this study, it seems likely that the community is changing in response to long-term sedimentation stress due to chronic terrestrial run-off and reduced ocean circulation in Pelekane Bay associated with massive deforestation in the Kawaihae watershed and the construction of the Kawaihae Harbor revetment. Several suggestions are made to restore Pelekane Bay to a more productive condition.