Articles | Volume 13, issue 2
01 Dec 1994
 | 01 Dec 1994

Computer analysis of benthic foraminiferal associations in a tidal New Zealand inlet

Bruce W. Hayward and Christopher M. Triggs

Abstract. Census data on benthic foraminiferal tests in 45 surface sediment samples from Pauatahanui Inlet, Wellington, New Zealand, are analysed by Correspondence Analysis and Non-Hierarchical classification techniques. The faunas are grouped into 7 associations: (A) Trochamminita irregularis/Miliammina fusca - at high tide level in a small tidal creek at the limits of salt water influence; (B) Trochammina inflata/Jadammina macrescens - in an extreme high tidal pool, close to the mouth of a small stream; (C) Miliammina fusca/Haplophragmoides wilberti/Trochammina inflata - intertidal and shallow subtidal (to 0.6 m depth), muddy sand over a large area in the upper reaches of the inlet, where most freshwater runoff enters; (D) Elphidium excavatum/Miliammina fusca - intertidal muddy sand associated with shelly beaches on the fringe of association C; (E) Ammonia beccarii/Haynesina depressula - in a wide variety of intertidal and shallow subtidal (to 3 m depth) sediments that form a belt between the more brackish associations (A–D) and the more normal salinity associations (F–G); (F) Bolivina cf. translucens/Textularia earlandi/Bolivina subexcavata - in mud to muddy, very fine sand in a shallow basin (1–2.5 m deep) in the middle of the inlet and in a small, sheltered backwater; (G) Elphidium charlottensis/Patellinella inconspicua/Quinqueloculina seminula - in sandy mud and muddy fine sand, intertidal to 10 m depth, in the mouth, entrance channel and adjacent outer and middle parts of the inlet, where a flush of normal salinity water enters during each tidal cycle.

Using Canonical Correspondence Analysis, the factors most influential in determining the faunal distribution are, in decreasing importance: freshwater influence (salinity), exposure to the air during tidal cycles, proximity to the open sea, tidal current strength and percentage of mud in the substrate.