FORAMINIFERA SPECIES DISTRIBUTION AND GEOCHEMISTRY: A TOOL FOR ECOLOGICAL ASSESSMENT OF LYTTELTON HARBOUR, NEW ZEALAND

Benthic foraminifera species and population analysis is a powerful tool for ecological and paleoclimatological assessment. To date little is known about foraminifera within Lyttelton Harbour and this study characterises presence, abundance, and species diversity, and highlights the use of foraminifera in recording changes in environmental conditions in response to anthropogenic development. Nine samples from the top 2-3cm of sediment were collected from four intertidal bays in Lyttelton Harbour. Samples underwent qualitative sediment texture assessments and assigned quantitative grain values. Fourteen species of modern foraminifera were identified and foraminiferal abundance and diversity, sediment trace element chemistry, and percent organic sediment component were analysed.

Foraminifera and trace elements were more abundant in finer grained sediments, as they were most likely washed out of coarser, more porous areas by tidal currents. An exception to this occurred at one site, where it is possible that sedimentation rates and dynamics have been altered by dredging as part of maintenance at Lyttelton Port. Percent organic sediment component was higher near mean sea level than mean high water, possibly due to the lower-energy conditions in the moderate tidal geography, allowing for development of vegetative communities and accumulation of sedimentary organic material. Trace elements found in the harbour can be related to anthropogenic activities, and may have been redistributed away from the port itself by sedimentary processes, an aspect that requires further investigation.

Foraminiferal abundance and sediment geochemistry in Lyttelton Harbour are primarily controlled by sedimentary processes, and intertidal foraminifera present are typical New Zealand forms. This project demonstrated that foraminifera are abundant in Lyttelton Harbour, and thus provided the foundation for future investigations. Such work can be used to assess the extent to which activity at the large commercial Lyttelton Port and other urban development in and near the Lyttelton Harbour have impacted its water quality, sediment chemistry, and local biota.