Diatom (< 63 µm) distribution offshore of eastern New Zealand: Surface sediment record and temperature transfer function

Diatom microfossils preserved in 38 core top samples from offshore of eastern New Zealand are examined to develop the first offshore modern analogue dataset for diatoms in New Zealand waters. The sample set consists of seven, approximately E–W trending depth transects with samples from the continental shelf, slope and abyssal plain between latitudes 33° and 54°S. The identification of terrestrial and coastal species in open marine core top samples indicates that offshore transport of diatom microfossils occurs to an extent that could be useful for sediment provenance studies or at least to enable improved identification of transported versus in-situ deposition on the continental shelf. Cluster analysis and ordination indicate that the Chatham Rise and/or the overlying Subtropical Front are the most significant bathymetric/oceanographic features in the dataset as this location shows up as a major barrier or transition zone in terms of diatom distribution. The strongest environmental control on diatom distribution is the north–south sea surface temperature gradient. A statistically strong relationship (r2 = 0.81; RMSEP = 1.57) exists between diatom abundance and sea surface temperature making diatoms ideal for quantitative reconstruction of past sea surface temperatures in future paleoclimate studies.