Current and historic distribution and abundance of the inarticulated brachiopod, Lingula reevii Davidson (1880), in Kaneohe Bay, Oahu, Hawaii, USA

Abstract

The inarticulated brachiopod, Lingula reevii Davidson (1880) is a Wlter-feeding invertebrate that bur- rows vertically in sandy or mixed sediments. Its only recorded occurrence is from Kaneohe Bay, Oahu, Hawaii, southern Japan, and Ambon, Indonesia. Past surveys of Kaneohe Bay populations suggested a distinct decrease in abundance following the diversion of sewage eZuent from the bay in 1978/1979. In the summer of 2004 and 2007, visual surveys were conducted in areas of historical L. reevii abundance as well as in areas appearing to have suit- able habitat. In 2004, approximately 2,950 m 2 at 20 sites within the bay were surveyed using quantitative belt tran- secting methods. A maximum density of 4 Lingula/m 2 was observed, a decrease from previous maximum estimates of 500 individuals/m 2 (Worcester, Dissertation, Zoology Department, University of Hawaii, pp 49, 1969) and 100 individuals/m 2 (Emig, J Exp Mar Biol Ecol 52:47-61, 1981). When these 20 sites were revisited in 2007, many had fewer or no L. reevii; therefore, broader scale presence/ absence surveys were conducted at 16 additional sites in the bay (also surveyed in 2004). The highest density of L. reevii found in 2007 was 0.94 individuals/m 2 . The con- tinued decline in abundance of L. reevii in Kaneohe Bay may be due, in addition to decreased organic enrichment from diversion of sewage discharge almost 30 years ago, to the more recent reduction of suitable habitat by the invasion of mat-forming alien algae species.