Foraminiferal associations in the upper Waitemata Harbour, Auckland, New Zealand

Abstract

Census data on 68 benthic foraminiferal tests in 56 seafloor sediment samples from the upper Waitemata Harbour, Auckland, New Zealand (36° 50' S, 174° 40' E) are analysed by Cluster Analysis. The faunal samples, taken from extreme high tide to 8 m depth, and from strongly brackish to normal marine salinities, are grouped into 7 associations. Characterising species of each association are found by calculating Association Scores for each species, based on its mean abundance, relative abundance, fidelity, persistence, and dominance within each association. The foraminiferal associations are: JE, Jadammina macrescens‐Elphidium excavatum f. clavata – high tidal, sandy mud, in salt meadow and dwarf mangrove swamp, with near normal marine salinity; Tn, Trochammina inflata – around mean high water springs in salt marsh and salt meadow, with variable salinity; M, Miliammina fusca – subtidal channels and intertidal mud banks, mangrove swamp, and salt marsh with reduced salinity; H, Haplophragmoides wilberti – above mean high water, in salt meadow and salt marsh, with slightly reduced salinity; Tr, Trochamminita salsa – intertidal sandy mud banks at head of estuary, with lowest salinity; AM, Ammonia beccarii‐Miliammina fusca – intertidal and shallow subtidal mud fiats and channels, with near normal marine to slightly reduced salinity; A, Ammonia beccarii – intertidal and subtidal (to 8 m+ depth) muddy sand, with near normal marine to slightly reduced salinity. In the cluster analysis dendrogram of samples, the first‐order division produces a three‐way split of: (1) near‐normal marine salinity agglutinated associations (JE, Tn); (2) low‐salinity, agglutinated associations (M, H, Tr); and (3) near‐normal marine salinity, calcareous associations (AM, A). The dominant foraminiferal species are grouped by cluster analysis into five species associations; these correlate closely with the sample associations. There is an overall trend of increasing species diversity from brackish to saline and from intertidal to subtidal. This study supports earlier conclusions that salinity and tidal exposure are the two most influential factors in determining foraminiferal distribution patterns in sheltered tidal harbours and estuaries. A common species in the near‐normal salinity subtidal channels, Siphogenerina striata, may have been introduced into the harbour with foreign shipping. © 1997 Taylor and Francis Group, LLC.