Vol.12 No.4 - December 2004

NIWA scientists have documented a warming trend in the Tasman Sea using data collected as part of a collaboration with scientists from Scripps Institution of Oceanography (USA) and CSIRO (Austalia). We hypothesise a link with declining hoki stocks in Ocean variability and hoki decline.

In this issue

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    Classifying stream invertebrate communities

    PDF of this article (200 KB)
    Thomas Wilding
    A study of almost 700 invertebrate samples from around New Zealand is helping to extend our understanding of stream ecosystems.
    Water managers in New Zealand are increasingly using invertebrates to monitor stream health, encouraged by initiatives such as the Ministry for the Environment’s national sampling protocol. But as the use of invertebrates as a monitoring tool becomes more widespread, the limits of our understanding become more of an issue.
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    Coral rings in the deep ocean: using SEM to date New Zealand's bamboo corals

    PDF of this article (282 KB)
    Juan Sánchez
    Di Tracey
    Helen Neil
    Peter Marriott
    Thickets of coral on the deep-ocean floor have secrets to tell us about past environmental conditions. But first we have to get them to tell us their age.
    Some bamboo corals from New Zealand waters (Isididae: Keratoisidinae).
    With their segmented trunks made of alternating calcareous white nodes and organic dark internodes, “bamboo corals” get their common name from their tropical plant lookalikes.
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    Squeezing information from an elusive ocean: surface currents from satellite imagery

    PDF of this article (156 KB)
    Melissa Bowen
    Ken Richardson
    Matt Pinkerton
    Aarno Korpela
    Michael Uddstrom
    Computer analysis of satellite data is giving us new insight into how the ocean moves around New Zealand.
    Pictures of the surface of the ocean taken by satellites often show beautiful swirls, curls, and plumes. When the pictures are animated, the features can appear to be slowly moving. Some of this apparent movement reflects underlying currents pulling the features along.
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    Forecasting ocean "weather"

    PDF of this article (244 KB)
    Graham Rickard
    Mark Hadfield
    Modelling ocean currents helps focus our view of the “big picture”.
    We take for granted the weather forecast: it’s a familiar feature in newspapers, radio, and television, and we spend most of our time in the atmosphere where this weather happens. We are often less aware of the effects of ocean “weather”.
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    Ocean variability and hoki decline

    PDF of this article (392 KB)
    Janet Bradford-Grieve
    Mary Livingston
    Philip Sutton
    Mark Hadfield
    Changing conditions in the Tasman Sea may have brought hard times for newly hatched hoki larvae.
    Declining hoki stocks
    Hoki catch. (Photo: N. Bagley)
    Fisheries managers and fishers have become worried about the ongoing decline in the western stock of hoki. This stock is now estimated to be at about 13% of the biomass that existed before fishing developed for this species in 1972.
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    Nutrient enrichment in mangrove ecosystems: a growing concern

    PDF of this article (314 KB)
    Pip Nicholls
    Anne-Maree Schwarz
    Nicole Hancock
    Fertilisation experiments are showing that some mangroves grow well with a little nitrogen.
    Love them or loathe them, mangroves are an integral part of New Zealand’s estuarine ecosystems. Like all large plants, they significantly influence many key processes, such as nutrient cycling. They also play a vital role in coastal sediment stabilisation. In the tropics, mangroves are highly valued as habitats for many fish and invertebrate species; however, many of these mangrove ecosystems are under threat.
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    NIWA news forum

    On this page
    Tsunami: the great waves – knowledge is safety
    Fuelling science by young people
    NIWA hosts meeting of infrared experts from NDSC
    Winston Churchill Fellowship
    End of a trap
    New quick guides simplify identification of freshwater flora and fauna
    Focus on corallines
    Recent publications by NIWA staff
    Tsunami: the great waves – knowledge is safety
    Tsunami is one of New Zealand’s underrated natural hazards. The last major event was caused by a massive earthquake in Chile in May 1960.
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    Managing Te Roto o Wairewa: lessons from the past

    PDF of this article (224 KB)
    Michael Reid
    Robin Wybrow
    Craig Woodward
    Scientists have probed the secrets of the lake sediments to help in the rehabilitation of Te Pātaka o Rakaihautū.
    Ko Te Waka Uruao, Ko Rakaihautū te tangata tuatahi, Ko Te Pātaka o Rakaihautū te whenua nei.
    The first man was Rakaihautū, his canoe was the Uruao, the name of this land is the Storehouse of Rakaihautū.
    According to Ngāi Tahu tradition, a great waka – Uruao – arrived out of the mists of time to the shores of Te Wai Pounamu.
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    The role of sediment in keeping seagrass beds healthy

    PDF of this article (219 KB)
    Anne-Maree Schwarz
    Fleur Matheson
    Trevor Mathieson
    Seagrasses are integral to our estuaries and coastlines, but they are vulnerable to the impacts of development.
    Seagrasses in the estuarine landscape
    Subtidal seagrass fringe in Whangapoua Harbour. (Photo: M. Francis)
    Seagrasses are the only flowering plants that grow in the sea. They probably colonised the marine environment about 100 million years ago from freshwater and coastal saltmarsh ancestors, and now they play an important role in coastal ecosystems.
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    Stream biomonitoring using species traits

    PDF of this article (175 KB)
    Ngaire Phillips
    A better understanding of how freshwater creatures fit into their habitats can point the way to conserving ecosystems.
    Next time you look at a mayfly in a fast-flowing stream you might notice that it has a nice flat body shape and that it hugs the pebbles. You might even think that these characteristics (or traits) would be pretty useful in helping it to resist the flow and allow it to “fit” into this rather harsh environment (at least from the mayfly’s viewpoint).
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    How invasive weeds affect lake sediments and native plant growth

    PDF of this article (317 KB)
    Fleur Matheson Mary de Winton John Clayton Tracey Edwards Experimental work points to yet another way that a major aquatic weed damages New Zealand lakes. Hornwort (Ceratophyllum demersum) is an invasive, submerged weed that has a major effect on habitat quality in New Zealand’s freshwater environments. Like other water weeds (such as egeria and lagarosiphon), hornwort can form dense, unsightly, and hazardous weed beds which can displace our valuable native plant communities and remove vital habitat for fish and other freshwater biota.