Vol.10 No.3 - October 2002

A rockhopper penguin from Campbell Island. Over the past 60 years rockhopper populations in New Zealand’s sub-Antarctic islands have declined alarmingly. A NIWA study has begun to identify possible reasons for the decline. See “Declining rockhopper penguin populations in New Zealand” for more details.

In this issue

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    Living on the edge: putting the heat on adult aquatic insects

    PDF of this article (254 KB)
    Brian Smith Kevin Collier Healthy populations of aquatic insects need a suitable environment on the stream bank as well as in the water.
    Adult Zelandoperla decorata (a stonefly).
    Adult Hydrobiosis parumbripennis (a caddisfly).
    Microclimate control chamber.
    Diurnal temperature ranges over 96 hours used in the study.
    Predicted LT50 for adult stoneflies and caddisflies.
    The term “aquatic insects” is collectively applied to the nymphs or larvae (young stages) of insects that spend part of their life cycle in water.
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    Do mussels eat zooplankton?

    PDF of this article (81 KB)
    Karen Robinson John Zeldis Alex Ross Experiments are helping to establish the feeding preferences of farmed mussels.
    Examples of some of the organisms found in mussel gut samples.
    The feeding experiment. A series of buckets each contained one feeding mussel. Buckets containing seawater only were included as controls.
    It has long been known that mussels are effective filterers of suspended material, including phytoplankton, bacteria, and non-nutritive material such as silt.
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    NIWA news forum

    On this page
    NIWA’s new executive team New home for NIWA, Nelson Sea and Learn 2002 NIWA’s National Centres Perlan: gliding to new heights New Zealand’s Sandy Coasts CD-ROM Where did all the water go? NIWA in the desert New Zealand–French collaboration: a symposium
    NIWA’s new executive team The new executive team, which met for the first time under Chief Executive Rick Pridmore on 22 August, consists of three directors and seven general managers, each with various portfolio responsibilities.
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    In our rivers: too much of a good thing?

    Regular monitoring of the growth of algal slimes is helping to identify trends in the overall health of our larger rivers.
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    Declining rockhopper penguin populations in New Zealand

    PDF of this article (180 KB)
    David Thompson Paul Sagar Feathers from museum specimens of rockhopper penguins are helping to throw light on the dramatic population decline of this bird in New Zealand’s sub-Antarctic islands since the 1940s.
    Map showing the locations of Campbell Island, the Antipodes Islands and the Auckland Islands – breeding sites of rockhopper penguins in New Zealand.
    Graph 1: Variation over time in δ15N (‰) for rockhopper penguins from Antipodes Island. Each dot represents an individual bird.
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    Wild southerlies of summer

    PDF of this article (495 KB)
    Lionel Carter Andrew Laing Rob Bell Occasionally huge storms from the south take us by surprise. Where do they come from and what are their characteristics?
    Not a war scene, but the debris-strewn coast road between Island and Owhiro bays, 6 February 2002. (Photo: Bill and Suzanne Main)
    Blue sky – white water: breaking waves fill Island Bay on Waitangi Day (6 February 2002).
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    The secret of a stable life: avoiding starvation

    PDF of this article (220 KB)
    Niall Broekhuizen Julie Hall To give a realistic picture of the marine food web, models need to take into account the fact that small oceanic organisms can starve.
    Simulated dynamics of algae, bacteria, active protozoa and cysts in the microbial food web.
    We tend to think of large animals such as fish and whales as the main occupants of the deep ocean, but most marine organisms are tiny, often less than 0.2 mm long. There are literally billions of these organisms for every whale.
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    Lake Taupo: clean and blue-green

    PDF of this article (255 KB)
    Ian Hawes Clive Howard-Williams Management of pristine lakes such as Lake Taupo requires an understanding of how the various constituents of natural waters affect their optical properties – water colour and clarity.
    Contributions to absorption in Lake Taupo water.
    Modelled light in Lake Taupo at 10 m depth.
    Water colour and clarity are both immediately evident to an observer and important in any assessment of water “quality”. Instinctively we look on clear blue water as better than turbid brown or green water.
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    High-tech tools for tackling fisheries problems in lakes

    PDF of this article (212 KB)
    Dave Rowe Gavin James Gavin Macaulay Ude Shankar Management of lakes to protect fish can be improved by the use of GIS methods and new echo-sounding techniques.
    Depth contours for Lake Taupo.
    Change in the total area of smelt spawning habitat with lake level for Lake Taupo.
    Typical echogram across Lake Rotoiti.
    Profiles from one side of Lake Rotoiti to the other showing changes in the distribution and density of adult rainbow trout and large smelt over 3 days.
    Changes to lakes such as greater water-level fluctuations, increased turbidity, or a decline in
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    Why is wood important in streams?

    PDF of this article (289 KB)
    Mark Meleason John Quinn Rob Davies-Colley Wood in streams isn’t debris: it plays an important role in shaping stream channels and providing diverse habitat for stream life.
    The “plunge pool”, located immediately downstream of this log, was formed by the erosive force of the small waterfall on the streambed. (Venture Creek, South Westland)
    Sediment, large wood, and small organic matter have accumulated behind the log being measured.