Associations of benthic foraminifera (Protozoa: Sarcodina) of inner shelf sediments around the Cavalli Islands, north‐east New Zealand

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Abstract
Census data on foraminiferal tests (live plus dead) from 55 dredge samples (0-41 m depth) of surficial sediments around the Cavalli Islands were analyzed by non-hierarchical classification, principal components and minimum spanning tree techniques. The samples are grouped into 4 associations with 5 subassociations. Species of each association are found by calculating association scores for each species, based on its dominance, fidelity and relative abundance within each group. The 4 associations are: A. Elphidium charlottensis, subassociations E. charlottensis/E. oceanicum/(Virgulopsis turris), E. charlottensis/(E. oceanicum/E. simplex), in sandy beach gravel or fine to very fine sand in shallow bays (intertidal to 6 m depth) on a sheltered coast; Pileolina zealandica/Cibicides marlboroughensis, subassociations Discorbis dimidiatus/E. novozealandicum/P. zealandica, P. zealandica/C. marlboroughensis/Neoconorbina pacifica, C. marlboroughensis/Quinqueloculina seminula/Notorotalia olsoni, widespread in clean, medium to coarse sand or shell gravel in moderately exposed or current-swept locations (5-10 m depth); Planoglabratella opercularis/Pileolina harmeri/Neoconorbina pacifica, in shelly, very coarse sand or shell gravel in shallow (6-9 m), strongly current-swept, wave-battered channels; Cassidulina carinata/Bulimina submarginata/Globocassidulina canalisuturata, in fine to very fine sand in the deeper (29-41 m), northern parts of the Cavalli Passage. Associations or variants are recognizable in similar environments elsewhere around northern New Zealand. Associations characterized by abundant plastogammic foraminifera, such as glabratellids and buliminoidids, have not previously been identified around New Zealand and are rare elsewhere. The habit of fusing together in plastogammic pairs during the sexual phase of reproduction appears to be an adaptation to survival in strongly current-swept environments. Species diversity (Fisher .beta. index, Information Function) and Evenness increase regularly with increasing depth. There is good correlation between these foraminiferal associations and the macrofaunal associations recognized from the same dredge samples.