Foraminiferal associations in Wanganui Bight and Queen Charlotte Sound, New Zealand

Abstract

Eight benthic foraminiferal associations are recognised in Wanganui Bight and Queen Charlotte Sound, New Zealand, based on cluster analysis of census data from 52 sediment samples. Distribution of the four associations in Wanganui Bight correlates with increasing water depth: Elphidium charlottense/Haynesina depressula/ Patellinella inconspicua association (17–27 m); Patellinella inconspicua/ Quinqueloculina suborbicularis association (20–42 m); Cassidulina carinata/Miliolinella subrotundata association (42–66 m); and Cassidulina carinata/Bulimina submarginata (72–109 m). The four associations in Queen Charlotte Sound are: Quinqueloculina seminula/Elphidium advenum/Haynesina depressula in sandy shallows (0.5–7 m); Epistominella vitreal Haynesina depressula in shallows of the outer Sound (4–12 m); Elphidium vellai/Haynesina depressula in the mouth of the Sound (9–25 m); and Nonionella flemingi/ Notorotalia finlayi in a muddy, sheltered basin (25–42 m). The most important physical factors influencing benthic foraminiferal distribution patterns in these two areas appear to be the characteristics of the water (e.g., temperature, turbidity, salinity) and factors that vary with water depth (e.g., wave and current energy, substrate, light penetration, food availability). Species diversity (α, H) and the relative abundance of planktic foraminiferal tests are mostly greater in the open sea conditions of Wanganui Bight than in Queen Charlotte Sound. In Wanganui Bight both generally increase with increasing depth, although there is a local diversity peak at 70–80 m depth.