BRACKISH FORAMINIFERA IN NEW-ZEALAND - A TAXONOMIC AND ECOLOGIC REVIEW

Approximately one third (11 species) of the world obligate brackish fo raminiferal taxa occur in New Zealand's estuaries and upper reaches of enclosed harbours, inlets and lagoons. The previously confused local taxonomy of New Zealand's obligate (11 species) and common facultative (9 species) brackish foraminifera is integrated with current overseas usage. Nineteen of the 20 brackish species in New Zealand have a worl d-wide distribution. All 20 species occur in northern New Zealand (lat 35-degrees-S) with a progressive decrease in diversity to 13 species in the south (lat 47-degrees-S). Cluster analysis based on the quantit ative faunal counts of 68 samples from 5 study areas results in the re cognition of nine brackish foraminiferal associations. Within brackish settings, salinity and secondly tidal exposure, are the two environme ntal factors having the strongest influence on foraminiferal distribut ion. With increasing salinity, brackish faunas increase in diversity, decrease in abundance of agglutinated taxa and increase in abundance o f calcareous taxa. The associations exhibit the following general tren d correlated with increasing salinity: a. Trochamminita (least saline) ; b. Haplophragmoides wilberti, Miliammina; c. Ammonia - Miliammina; d . Elphidium excavatum, Ammonia - Elphidium, Ammonia; e. Marginal Marin e (most saline). Five associations are apparently restricted to the in tertidal zone: a. Trochammina inflata (above mean high water); b. Troc hamminita, Haplophragmoides wilberti (above mean sea level); c. Elphid ium excavatum (predominantly mid-tidal); d. Ammonia - Elphidium (betwe en mean low and mean high water). Tidal current transport of foraminif eral tests produces mixed assemblages in the mouths and lower channels of New Zealand estuaries (diurnal microtidal and low mesotidal ranges ).