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New Zealand Journal of Marine and Freshwater Research abstractsM99054 Received 30 September 1999; accepted 8 May 2000
Aspects of the structure and variability of the low-salinity-layer in Doubtful Sound, a New Zealand fiordMARK T. GIBBS
Department of Marine Science
Abstract The concurrent actions of fresh water input from the
Manapouri power station and the extreme precipitation in the catchment of
Doubtful Sound, south-western New Zealand, results in the maintenance of a
surface low-salinity-layer (LSL). Although the role of the LSL in controlling
subtidal and inter-tidal assemblages in Doubtful Sound has been documented,
little is presently known about the characteristics of the LSL itself. The work
presented here aims to elucidate particular aspects of the structure and
variability of this ecologically important feature. Synoptic hydrographic data
collected during the Doubtful Sound Monitoring Program (DSMP) shows that the
LSL is robust and maintained throughout all seasons. Furthermore, hourly
salinity and temperature data acquired from four sites within Doubtful Sound
show that the major source of variability in the LSL lies in the weather bands
although the surface temperatures also exhibited a seasonal component.
Time-series analyses of these data revealed that large perturbations in the LSL
were associated with the combined actions of the local wind stress and
precipitation. In addition, analysis of data from moored quantum PAR
(photosynthetically active radiation) sensors revealed the important influence
of the LSL on the subsurface light field. |