Vol.10 No.2 - June 2002

Soil erosion during heavy rainfall has resulted in the deposition of a thick layer of mud on an intertidal flat in this estuary, smothering much of the shellfish bed shown, and killing the shellfish. This is one example of how human activities in the surrounding catchment can impact on a fragile estuarine ecosystem. NIWA is developing and applying a range of modelling techniques to help understand and predict effects such as this. Examples are given in the news forum, Alien predator: freshwater jellyfish in New Zealand and Assessing human impacts on estuaries: it’s a risky business in this issue.

In this issue

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    Alien predator: freshwater jellyfish in New Zealand

    PDF of this article (1 MB)
    Ian Boothroyd
    Kay Etheredge
    John Green
    Jellyfish are familiar marine animals, but they are also found in freshwater. One species is quite common in New Zealand.
    Many people will have seen jellyfish washed up on the beaches around the New Zealand coastline following storms at sea. Some will be aware of the notorious “stingers” (box jellyfish – Chironex sp.) that make Northern Queensland beaches potentially lethal for swimming during December and January.
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    Bouncing back: how fast can stream invertebrates recolonise?

    PDF of this article (1 MB)
    Kevin Collier
    Steph Parkyn
    John Quinn
    Mike Scarsbrook
    For invertebrates intent on recolonising a stream after a disturbance or during stream restoration, simply getting to the stream site is only half the battle.
    How far may a mayfly fly? Answers to this sort of question are important for understanding how long it takes a stream to recover from major disturbances, and for predicting whether sensitive stream insects will recolonise restored areas of stream.
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    Predicting the future of global ozone

    PDF of this article (607 KB)
    John Austin
    Greg Bodeker
    Hamish Struthers
    Climate change is one problem, ozone depletion is another. True? Maybe not. New modelling techniques are helping to unravel the links between these two environmental issues, and to assess the implications of changes.
    Perhaps the two most debated environmental issues in recent years have been climate change and ozone depletion. In the past these have usually been treated as two different and unconnected phenomena. However, recent research has revealed a range of processes that link them.
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    Assessing human impacts on estuaries: it's a risky business

    PDF of this article (1 MB)
    Alastair Senior
    Malcolm Green
    A team of modellers at NIWA Hamilton has developed a way to help environmental managers assess "risk" in sediment-impacted estuaries.
    Estuaries are often muddy – ask any Helice crassa (mud crab). The reason is that clay, mud and silt are continuously being eroded from the land and then delivered to the estuary by streams and rivers. Most sediment arrives during and after heavy rainfall.
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    Determining impacts on marine ecosystems: the concept of key species

    PDF of this article (1 MB)
    Pip Nicholls
    When one marine animal has a large influence on other parts of its ecosystem, we call it a key species. These animals can be very useful in monitoring programmes.
    One of the goals of marine ecology is to detect and assess the scale of human effects – such as scallop dredging, heavy metal contamination or increasing turbidity – on marine ecosystems.
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    Is stream cover important for inanga?

    PDF of this article (1 MB)
    Jody Richardson
    Bankside and overhanging vegetation not only provides shelter for fish; it also helps a stream to form diverse habitat.
    Inanga are one of five galaxiid species that make up the whitebait catch, and in most rivers and streams they form the bulk of the catch. After they have migrated from the sea in spring, inanga spend about six months growing to maturity in fresh water.
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    NIWA news forum

    On this page
    Chief Executive succession
    NIWA’s National Centres
    NIWA scientist to take up international role
    Coastal & Storm Hazards workshop
    Sea levels on New Zealand’s eastern flank monitored
    Self-cleaning air: prize-winning research
    Filthy fumes killing us?
    SKINDEEP visits New Zealand
    Marine biodiversity – capacity-building in communities
    Granular surfaces: structure, organisation, memory
    Mapping team discovers underwater volcanoes north of New Zealand
    NIWA joins with DHI Water and Environment group
    Chief Executive succession
    NIWA’s Chief Executive, Paul
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    Stream restoration in Christchurch

    PDF of this article (2 MB)
    Alastair Suren
    Eric Graynoth
    Barry Biggs
    Shelley McMurtrie
    Rachel Barker
    Stream restoration in Christchurch is turning drains into living streams.
    Have you ever thought what happens when it rains in a city? Rainwater and oily road grime mix into a greasy cocktail, causing traffic accidents on slippery roads. Water and debris quickly flow off impervious roads, carparks and roofs. Stormwater drains can become blocked, causing localised flooding. Stormwater is often conveyed to small streams, which run dirty as the water races to the sea.
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    Second-hand smoke

    PDF of this article (1 MB)
    Ben Liley
    The products of burning in the tropics can be detected in the atmosphere as far away as New Zealand.
    When bush fires rage across parts of Australia, as they did from Boxing Day 2001, they produce spectacular sunsets, and sometimes a haze visible by day as the plume crosses the Tasman Sea.
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    Waves in shallow water

    PDF of this article (1 MB)
    Murray Smith
    Richard Gorman
    Craig Stevens
    John McGregor
    Waves generated in shallow, enclosed estuaries can have a big impact on marine life. Computer modelling of these wave systems is helping us to predict their effects.
    A familiar sight along New Zealand’s coast is waves growing, steepening and breaking as they approach the shore. Even to the most casual observer it is clear these waves must have major impacts on any aquatic plants tough enough to grow beneath them.