Foraminiferal Ecology, Ala Wai Canal, Hawai'i

Abstract

The foraminiferal fauna of the Ala Wai Canal, described for the first time here, is controlled principally by the canal's shallow coastal location, normal marine salinity range, sedimentation from a major point source, and phytoplankton productivity. Various pollutants may have produced up to 7% abnormalities in test growth, but low oxygen conditions in the back basin are counterbalanced by food availability there to produce the largest surface foraminiferal abundance of 140 tests per gram of sediment. For at least the past 50 yr, the Ala Wai Canal has harbored a foraminiferal assemblage dominated by five species that compose from 53 to 92% of the foraminifera. These dominant species, Ammonia beccarii (Linne) vars., Bolivinellina striatula (Cushman), Cribroelphidium vadescens Cushman & Bronnimann, Quinqueloculina poeyana d'Orbigny, and Quinqueloculina seminula (Linne), are widespread geographically, but are generally found together in lagoons or embayments where salinities are normal marine to hypersaline rather than in estuaries. The maximum number of species per sample (31) was found near the entrance and the diversity decreased into the canal.