Wellington Harbour Research Articles

Seismic measurements in Wellington harbour

Abstract Seismic surveys in Wellington Harbour (Port Nicholson) show that the greywacke basement under the harbour is an undulating erosional surface which has been depressed to a depth of about 400 m in the northwestern part. For most of the harbour the basement lies at a depth of 200 to 300 m. The depression is likely to be a fault-angle depression caused by tilting in a westerly direction. No signs of faults or fault-block structures were found in the basement under the harbour. A ridge of basement rocks with high seismic velocity crosses the harbour and crops out at Somes Island and Miramar Peninsula. It is inferred that this ridge and other morphological features in the Wellington area aligned approximately north-south are not of tectonic origin but are erosional features. The seismic velocity structure of rocks in the direct vicinity of the transcurrent Wellington Fault, aligned along the northwestern side of the harbour, is not known in detail. The crush zone of the Wellington Fault is, however, li...

Combined effects of temperature and salinity on hemigrapsus edwardsi (Hilgendorf) and H. Crenulatus (Milne Edwards) from Wellington Harbour, New Zealand

Tolerances to combined levels of temperature and salinity were studied in the New Zealand intertidal grapsid crabs Hemigrapsus edwardsi (Hilgendorf) and Hemigrapsus crenulatus (Milne Edwards). Field sampling established the seasonal environmental variation in temperature and salinity to which these species are subjected within Wellington Harbour and provided a basis for the choice of experimental levels. Temperatures of 5, 15 and 25°C and salinities of 0, 15, 35 and 45‰ were combined to produce 12 combinations to which animals were subjected in the laboratory. Estimated optimum conditions of temperature and salinity based on the ‘fitted response surface’ method are presented for summer and winter populations of both species. H. edwardsi survived better at low salinities only at low temperatures. It is postulated that estuarine penetration of this species in Wellington Harbour is prevented by the inability to withstand low salinities at higher temperatures. H. crenulatus survives in marine conditions when the temperature is high; a combination of low temperatures and low salinities is detrimental and the species is suspected of burrowing in the substratum to avoid these lethal conditions during colder months.

Numbers of Giant Petrels in Wellington Harbour and Cook Strait, Nz

Numbers of Giant Petrels in Wellington Harbour and Cook Strait, Nz

Food and feeding of Kahawai (Teleostei: Arripididae)

Abstract Analysis of 326 stomachs of the kahawai, Arripis trutta (Bloch and Schneider), from Wellington Harbour showed that the fish is a voracious carnivore which feeds mainly on fishes and to a lesser extent on planktonic crustaceans. The kahawai is principally a pelagic feeder, but occasionally takes food from the sea bottom; it appears to feed on those fishes which are locally most abundant, and follows shoals of small fish on which it preys. Small kahawai below 100 mm in length eat mainly copepods.

A geothermal heat flow probe for in situ measurement of both temperature gradient and thermal conductivity

A heat flow probe, with which both temperature gradient and in situ thermal conductivity in sediments can be measured, is described. The relevant theory and design requirements are presented. Results of thermal conductivity measurements on sediments in Wellington Harbour are given and compared with values from a needle probe and from a standard divided bar apparatus. It is concluded that the accuracy of the in situ thermal conductivity measurement is comparable to that from the divided bar and that the instrument permits heat flow measurements to be made more reliably and conveniently than by any other method.

Some Problems of Zealand Geomorphology

Wellington Fault belongs to the major fault belt which extends NE-SW through New Zealand, Namely, Alpine Fault of South Island extends along the northwestern side of the Southern Alps and the fault branches at the north end of the South Island into the Wangamoa, Wairau, Awatere, Clarence, Kekerengu, Hop-kaikoura and Port Pass Faults. And so, the Weillington Fault is regarded as the continuation of the Awatere Fault, and the Wairarapa Fault is regarded as the continuation of the Kekerengu Fault. These faults are mostly active and even in the historic past of 120 years, numerous earthquakes took place associated with crustal deformations. Wellington Fault has a boldly defined, fairly straight course and can readily be traced north-east for 150 miles from Cook Strait through Wellington City and along the west of the Wellington Harbour and Hutt Valley. Wellington Fault is a clockwise transcurrent fault and upthrow of the crustal blocks bordering this fault has raised the hill country to the west of it, while downthrow and buckling of the land to the east has helped to form the Port Nicholson and Hutt Valley depressions. At the upper levels of the western side of Wellington City, there are remains of Peneplains which are called the 'K' Surface by C. A. Cotton. Perhaps the 'K' Surface can be classified into some surfaces.The periglacial deposits were found by C. A. Cotton and M. T. Te Punga for the first time at Wellington. The periglacial deposits of the South Island in New Zealand were found by Jane Soons, Mr. Brockie and others.Two periglacial deposits-stratified scree and stratified solifluction tongue-were classified by Jane M. Soons in South Island. But, there are many problems on the periglacial geomorphology in New Zealand.

Gravity Surveys in Wellington and Hutt Valley

Gravity observations in Wellington, Hutt Valley, and Wellington Harbour are reported. Cross sections are given and alluvium thicknesses estimated. Between 3,000 and 4,000 ft of light sediments overlie greywacke basement in Wellington Harbour off Ngauranga Gorge.

A textural analysis of Wellington Harbour sediments

Summary Grain‐size and carbonate analyses have been carried out on bottom sediment samples of Wellington Harbour. From grain‐size parameters it was possible to establish a number of facies types and to outline sediment sources and directions of transport.

Zooplankton of Wellington Harbour, New Zealand : Wear R. G., 1965. Zoology Publ., Victoria Univ., Wellington, No. 38: 31 pp.

Zooplankton of Wellington Harbour, New Zealand : Wear R. G., 1965. Zoology Publ., Victoria Univ., Wellington, No. 38: 31 pp.

PHYSIOLOGICAL AND ECOLOGICAL STUDIES ON THE BIVALVE MOLLUSK ARTHRITICA BIFURCA (WEBSTER, 1908) LIVING COMMENSALLY WITH THE TUBICOLOUS POLYCHAETE PECTINARIA AUSTRALIS EHLERS, 1905

1. The bivalve mollusk Arthritica bifurca (Webster), previously considered to be free-living, has been found in large numbers living commensally with the tubicolous polychaete Pectinaria australis Ehlers. 2. Arthritica bifurca is attached by several fine byssus threads to the outer surface of the head-end of the tube of Pectinaria australis, orientated vertically with its anterior end directed downwards. Biological reasons for this commensal relationship are obscure. 3. Ecological observations on the Peclinaria australis population at Petone Beach, Wellington Harbour, suggest that the polychaete lives for only 12 or 18 months, and is subject to an extremely high mortality rate during growth and maturation and also after breeding in the spring. There is evidence for a fairly extended breeding period, and the population is probably replenished mainly during late summer by settlement of larvae at or near the high tide level. 4. Larvae of Arthritica bifurca are incubated by the parent at least to the shelled prodissoconch stage. A short planktonic larval life supported by pelagic or postpelagic host-finding behavior is the probable means by which the commensal bivalve is dispersed. 5. Physiological experiments with live material established that A. bifurca is able to distinguish between sea water that has passed over the host and sea water which has not done so. The bivalves are attracted chemotactically to Pectinaria australis by way of exhalant water currents from the tube worm, and there is a direct orthokinetic response as the bivalves move closer to the host.

Fluctuations in the Number of Giant Petrels at Ngauranga, Wellington Harbour, New Zealand

SummaryWeekly counts of Giant Petrels were made at Ngauranga, Wellington Harbour, from May 1958 to May 1962. There is a definite correlation between the number of Petrels at the Ngauranga freezing works and the amount of offal available, Petrel numbers reaching a maximum from November to February coinciding with the peak period of lamb killing. Counts of Petrels were compared with the weekly whale killing figures at the Tory Channel Whaling Station, Cook Strait, indicating that Petrels were generally absent from Ngauranga during the whaling seasons. The effect of migratory movements of Giant Petrels on the numbers present at Ngauranga throughout the year is discussed.

Studies on Phytoplankton in Wellington Harbour

Abstract Phytoplankton organisms from four stations in Wellington Harbour are described. Particular attention is devoted to descriptions of living cells of nannoplankton both from field collections and from laboratory cultures. Organisms belonging to the following groups of algae were found: Schizophyceae, Chlorophyceae, Chrysophyceae, Xanothophyceae, Euglenophyceae, Cryptophyceae, and Dinophyceae. New species of Pyramimonas, Collodictyon, Heliapsis, Ellipsoidion, Petalomonas, Entosiphon, Cryptomonas, and Cryptochrysis are described.

A note on tidal circulation in Port Nicholson, New Zealand

Summary Dye patch movements and other indicators demonstrate a complex zoned tidal stream flow into Wellington Harbour. In the harbour, the flood stream makes clockwise and the ebb runs anti-clockwise at rates approximating a quarter-knot. The boundaries between zones moving with different horizontal velocities are marked by slicks.

Seasonal variations in sea-water surface temperatures within New Zealand harbours

Summary Surface temperature records for the harbours of Auckland, Wellington, Lyttelton, Timaru, Otago, and Bluff have been compiled from ubservations taken frolll 1952 to 1955. For certain of these years mean, highest, and lowest recordings for 6-day periods are presented to indicate in some detail the nature of seasonal trends. Monthly means, summer-winter extreme and mean ranges are also tabulated. Diurnal, and abrupt temperature variations in Wellington Harbour are demonstrated and their causes examined. A tidal oscillation in the summer daily temperature anomalies is shown for Portobello (Otago). Seasonal differences between harbour and offshore temperatures at Lyttelton and Otago are outlined, Some ecological implications of widely fluctuating temperatbres within harbomwaters are discussed, A bibliography of published temperature data for New Zealand ports and harbours is appended.