Winter oceanographic observations in some New Zealand fiords

The winter oceanography of four New Zealand fiords is discussed using data obtained from July 1983, and comparisons are made with data collected on previous summers. Surface waters were more saline in winter than in summer and were everywhere cooler than the underlying water. Deep water renewal in the fiord basins was re‐examined using all available data. For Milford Sound and the other deep silled fiords renewal appears to be related to the arrival of dense water at sill depth offshore by an as yet unknown advective or meteorologically forced process. In the more isolated Long Sound, Preservation Inlet, deep water renewal requires the subtle interplay of tidal flows and mixing processes over the shallow double sill. Complete renewal of Long Sound bottom water appears to be a slow process.     

Reconnaissance survey of the mineralogy and geochemistry of some New Zealand lake and nearshore sediments

131 sediment samples representing 4 different environments (lakes, sounds, harbours, and fiords) in New Zealand have been studied and characteristic differences in chemical composition and mineralogy noted. These differences are related principally to the lithology of the sediments and the productivity of the lake waters. This study should provide a baseline for future surveys of lake sediment geochemistry in New Zealand.     

Life‐history studies on New Zealand Brachyura

A brief account is given of the systematics and distribution of Heterozius rotundifrons A. Milne Edwards, Ozius truncatus H. Milne Edwards, and Heteropanope (Pilumnopeus) serratijrons (Kinahan). Keys are given for the separation of Zoea larvae of New Zealand xanthid Brachyura and to the Megalopa larvae of Heterozius rotundifrons and Ozius truncatus

Notes are given on the seasonal breeding cycle of Heterozius rotundifrons, and the pre‐Zoea larva, two Zoea larval stages, and Megalopa larva reared in the laboratory are described. Larval characters of H. rotundifrons are specialised and do not support its recently suggested classification in the family Atelecyclidae. The larvae show no relationships with those of the Cancridae or of the Corystidae, and affinities with described larvae of the Xanthidae or even the Brachyrhyncha are obscure. Larval development is incompletely abbreviated possibly to reduce dispersal in response to restricted intertidal habitat requirements of the adult crabs.

The pre‐Zoea larva, four Zoea larval stages, and the Megalopa larva of Ozius truncatus reared in the laboratory are described. A key to the Zoea larval stages is given. Larvae of this species are distinct both at the generic and specific levels, but are generally similar to those known of xanthid crabs. It is difficult to relate the genus Ozius to other xanthid genera on the basis of larval characters alone.

The pre‐Zoea larva and stage one Zoea larva of Heteropanope (Pilumnopeus) serratifrons are described. There are probably four Zoea larval stages in the development of this species. Zoea larval characters suggest that in the family Xanthidae, Heteropanope and Pilumnopeus should be separated from other genera in the subfamily Pilumninae with which they are currently classified.     

Heavy metal levels in New Zealand molluscs

Cadmium, lead, copper, mercury, zinc and iron were analysed by atomic absorption spectrophotometry in 13 species of edible molluscs from 199 sites around New Zealand; these included all molluscs commonly eaten in New Zealand. From each sampling site, a minimum of 14 specimens were combined and analysed together, so that the result would be representative of the population in that area. Wide variations are shown to occur in heavy metals from one location to another, and explanations for some of these variations are given.     

Environmental assessment from the sedimentary record of high-latitude fiords

The sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution (the scale of millennia) and high resolution (decadal to less than daily). Unlike the lacustrine record which has been used very successfully in these studies, the sedimentary processes and thus the sedimentary deposits of fiords differ (1) in the role of salt water in inhibiting mixing and promoting flocculation, and through the role of sea-ice, (2) in the exchange of mass and energy with the much larger ocean beyond, and (3) in the role of benthic biota in the sedimentary environment. The work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes, as well as glacial, periglacial and geomorphic history, and that they are important proxies for long-term climate and hydrology. Recommendations for advancing this work include long-term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment. Integration of results from fiords in opposite polar latitudes, and among proxies especially from lacustrine and ice-core records will produce valuable insights. Assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type.     

Effects of sea urchin (Evechinus chloroticus) grazing in Dusky Sound,Fiordland, New Zealand

Evechinus chloroticus (Val.) is known to be an important grazer of subtidal barren habitats in northern New Zealand but its role in structuring rocky reef communities at colder southern localities is poorly understood. The present study was prompted by a proposal for the establishment of an E. chloroticus fishery in Dusky Sound, Fiordland, New Zealand. To determine the ecological importance of E. chloroticus in Dusky Sound, sea urchins were experimentally removed from shallow fucoid fringe (upper zone), mid‐depth barrens (middle zone), and deeper algal meadow (lower zone), at eight sites and compared with a paired set of eight control sites. Two years of continuous removal of E. chloroticus resulted in conspicuous changes to the algal community at all depth zones examined. The density of fucoid algae (Carpophyllum spp., Sargassum spp., Cystophora spp., and Landsburgia quercifolia) increased mostly in the upper and middle zones, although smaller increases were also observed in the lower zone. Changes in cover of herbaceous, turfing and crustose algae observed in the middle and lower zones were larger than in the upper zone. Density increases of the kelp Ecklonia radiata were observed mainly in the lower zone, although still important in the middle zone. These results show that E. chloroticus can have a strong influence on the structure of algal assemblages in Dusky Sound hence the development of an E. chloroticus fishery in this area should be treated with caution.