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February’s phenomenal flood
NASA helps with measuring phytoplankton growth
Society for Conservation Biology (Marine Section) presidency
Where do larvae come from and where do they go?
The ecology of a disappearing river
That’s our buoy!
Estuary fish survey goes south
New snails in New Zealand
UV measurement: an international comparison
Recent publications by NIWA staff
February’s phenomenal flood
Inundated areas remaining on 24 February 2004 west of Palmerston North.

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February’s phenomenal flood

Inundated areas remaining on 24 February 2004 west of Palmerston North. (Source: NASA-supported Dartmouth Flood Observatory, USA)

Exceptionally heavy rainfall over the lower North Island on 15–16 February 2004 wreaked havoc in many places. The rainfall was caused by an unseasonal meteorological situation in which moisture-laden subtropical air met cold subantarctic air in a complex slow-moving depression. Two-day rainfall of up to 300 mm fell in some of the worst affected regions. The result was numerous landslides, wind damage and severe river floods, causing widespread inundation of low-lying areas. The magnitudes of flood peaks and their associated probabilities have not yet been assessed, but the flooding in the Manawatu was amongst the most severe known in the region. Further heavy rain later in the month caused additional severe flooding in several North Island locations.

Through our Natural Hazards research programme on floods and inundations, NIWA has for several years been developing various services such as flood forecasting, flood frequency analysis, inundation modelling, use of remote sensing and weather-related risk assessments. With this background, we have been assisting regional and central Government agencies in the response and recovery phases following the February floods.

One example of this assistance is providing satellite images of areas still under water one week after the 16 February event. These have been produced in partnership with the NASA-supported Dartmouth Flood Observatory (DFO) in New Hampshire (USA), who developed the technology using 250-m resolution data from sensors called MODIS and ASTER on the Terra satellite. The technique classifies and isolates areas that were dry before the flood, and overlays the information on high-resolution images of land surface features. The sample image shows inundation in an area centred on the Moutoa floodway between Foxton and Shannon.

For more information see The February 2004 New Zealand Floods and A winter storm in summer on this website; and

NASA helps with measuring phytoplankton growth

Data gathered by satellite can already tell marine scientists how much phytoplankton is growing where in the ocean. But what about how fast it is growing?

A recent visit to NIWA by leading NASA scientist Michael Behrenfeld has taken us a step closer to obtaining this information.

Phytoplankton is important because it is at the base of almost all open-ocean ecosystems. Our commercial and recreational fisheries, sea birds and mammals, and sea-floor resources all depend on phytoplankton. The rate of phytoplankton growth is controlled by the amount of nutrients available in the water (especially nitrogen and iron).

Dr Behrenfeld has shown that it may be possible to determine the degree of nutrient stress that these tiny plants cells are under (and from that, the growth rate of phytoplankton) by measuring the ratio of light absorbed by phytoplankton to their biomass. This ratio can potentially be obtained from satellite data. The method could give us information on phytoplank-ton growth on an enormous scale – both in space and over time. Such information promises to significantly improve our understanding of patterns of productivity in the oceans around New Zealand, and how this may be affected by climate change.

Dr Behrenfeld spent 8 weeks in New Zealand, working with NIWA scientists from Dunedin, Wellington and Christchurch. Work on developing the method continues.

For more information, contact: Matt Pinkerton NIWA Private Bag 14901 Wellington [email protected]

Society for Conservation Biology (Marine Section) presidency for NIWA scientist

NIWA scientist Carolyn Lundquist has recently been elected President of the Marine Section of the Society for Conservation Biology (SCB). SCB is an international professional organisation dedicated to promoting the scientific study of biological diversity. The Society’s membership of more than 8000 from over 110 countries includes scientists, resource managers, educators, government and private conservation workers, and students.

The Marine Section serves over 500 SCB members and Dr Lundquist has been on the Board of Directors since 2001. The goals of the Marine Section include furthering research in marine conservation, increasing awareness of marine conservation issues, both in public policy and through public education programs, and fostering collaboration and cooperation among marine researchers throughout the world.

SCB has recently been awarded a grant from the Christensen Fund to increase the participation of conservation scientists from outside North America, including New Zealand scientists, in the activities of the Society.

For further information, contact: Carolyn Lundquist NIWA PO Box 11115 Hamilton Phone +64 7 859 1866 fax +64 7 856 0151 [email protected]

Where do larvae come from and where do they go?

Russell Taylor collecting larval pump samples. (Photo: J. Fleming)

Although many rocky intertidal invertebrates are sedentary, they are able to disperse because they have a free-swimming larval stage. But how far can the larvae go in the complex currents of coastal waters? Can they get far enough from the coast to ride the currents of the open ocean? Answers to these questions could help us to understand how invertebrate populations are connected and how far larvae might disperse.

A multi-disciplinary programme at CEAME, the University of Canterbury/NIWA Centre of Excellence in Aquaculture and Marine Ecology, focuses on larval transport around coastal headlands. We are trying to determine the interactions of invertebrate larvae within complex coastal waters. The emphasis initially has been on the larval stages of the blue mussel Mytilus edulis and the green-shell mussel Perna canaliculus.

The work – a combination of ecology, invertebrate biology and physics – is being undertaken in the coastal waters around Banks Peninsula and Pegasus Bay, Canterbury. Since November 2003 we have made weekly collections of zooplankton, measured surface chlorophyll, conductivity, temperature and pressure, and gathered information on currents. Remotely sensed sea-surface temperature data are being used to locate large-scale eddies. The physical information will be used to calibrate a model of the region based on one developed by Roy Walters (NIWA, Christchurch), which can simulate currents around the Peninsula based on tidal and wind forcings.

This project will produce a general overview of the coastal physics around the Banks Peninsula region as well as a larval transport model of the area. The work will contribute to management of the coastal zone by providing fundamental knowledge about connections between populations, and modes and frequency of larval transport offshore.

Janelle V. Reynolds-Fleming David R. Schiel

The ecology of a disappearing river

Sometimes there’s water, usually there’s none. Part of the middle reach of the Selwyn River. Photos taken from the same point. (Photos: S. Larned)

The Selwyn River drains the Canterbury foothills and flows – sometimes – for 60 km across the Canterbury Plains to Te Waihora (Lake Ellesmere). A striking feature of the Selwyn is the absence of water in its middle reaches for most of the year. Water begins leaking from the river into the underlying aquifer as soon as the Selwyn flows onto the plains, and disappears within 10 km. The next 35 km of river has surface flow only in mid-winter, and during brief spring and autumn floods. About 15 km upriver from Te Waihora, shallow groundwater rises to the surface, and the Selwyn flows year-round from this point to the lake.

There is very little scientific information on intermittent rivers like the Selwyn. This represents a serious gap in our knowledge, because extreme low flows occur in rivers throughout drier regions of New Zealand (such as Otago, Canterbury, Marlborough, Hawkes Bay) where there are increased demands for abstraction of surface and groundwaters.

The environmental effects of changing surface flows in the Selwyn River is the topic of a new long-term, FRST-funded research project being conducted by NIWA and Lincoln Ventures, Ltd. We chose the Selwyn River for our research because of its strong responses to changes in both runoff and groundwater levels. Understanding an extreme system like the Selwyn can help us to predict future conditions in catchments where land-use is shifting toward intensive agriculture with high irrigation requirements.

Our research in the Selwyn combines several scientific disciplines: hydrology, geomorphology, biology, chemistry. We are looking at the river as a whole system, including linkages with surrounding landscapes, groundwaters, and downstream receiving waters. Our initial observations indicate that in the intermittent reach there are still significant permanent aquatic habitats in old, cut-off channels, and in areas of up-welling shallow groundwater (spring-fed channels). We expect that these remnant habitats play a vital role in maintaining biodiversity and river ecosystems in an otherwise dry riverbed.

For further details contact: Scott Larned (Project Leader) NIWA PO Box 8602 Christchurchph +64 3 348 8987 fax +643 348 5548 [email protected] or Dave Kelly (Liaison Group Coordinator) NIWA PO Box 8602 Christchurchph +64 3 348 8987 fax +643 348 5548 [email protected]

That’s our buoy!

It took two years for the buoy to drift almost halfway around Antarctica.

A drifter buoy used to track a patch of water south of Tasmania in 1999 has washed up in the Falkland Islands.

SOIREE (Southern Ocean Iron Enrichment Experiment) was a multi-national experiment led by NIWA that added iron to the surface waters to determine whether phytoplankton in the Southern Ocean are limited by iron availability. The drifter buoy was originally sent to New Zealand from Plymouth Marine Laboratory (UK), and was deployed from the Tangaroa during SOIREE. Following its second deployment 600 km off Antarctica the buoy stopped communicating, and was not seen for remainder of the experiment. However, a month later the buoy started transmitting again, via the ARGOS satellite, enabling us to track the buoy’s position for 4 months before the batteries ran out. The extra data proved invaluable, as locating the buoy position on satellite ocean-colour images confirmed that the added iron was still influencing the phytoplankton 5–6 weeks after the iron was added. A 150-kilometre ring of green chlorophyll provided strong evidence not only of the persistence and recycling of iron but also confirmation of how water is mixed and stirred in the upper ocean. In late

2003 Dr David Middleton, a fisheries scientist with the Falklands Islands Government, contacted us to say that the buoy had re-appeared.

Dr Middleton had written an article on a grounded US drifter buoy for the local Falklands paper, The Penguin News, and was contacted by a farmer who had found a buoy washed up almost 2 years previously on New Year’s Day 2001, on the southern tip of West Falkland. The buoy was identified by the number on the communications unit as the lost SOIREE buoy. Back-of-the-envelope calculations suggest it had taken 693 days to travel 8700 kilometres east from where it was first deployed, an average speed of 13 km per day. The buoy was recently transported to Port Stanley and was lined up for a journey home to Plymouth aboard the British Antarctic Survey vessel James Clark Ross, but unfortunately was too badly damaged to make the final leg back to the UK worthwhile.

For more information contact: Cliff Law NIWA Private Bag 14901 Wellington Phone +64 4 386 0300 fax +64 4 386 2153 [email protected]

Estuary fish survey goes south

Pipefish. (Photo: C. Middleton)

NIWA staff are surveying 21 estuaries from Banks Peninsula to Stewart Island to determine their small fish assemblages. This work will significantly extend our knowledge of biogeographic and north–south patterns of estuarine fish assemblages and follows our sampling of 31 estuaries in the upper half of the North Island (see Water & Atmosphere 9(1): 7). Local Department of Conservation and iwi representatives are helping with the fieldwork, providing valuable local knowledge and historical environmental insights as well as extra manpower.

The Mainland sampling component has been completed and some interesting spatial patterns are emerging. Fish not previously encountered in the programme include species of pipefish, sand diver, black and greenback flounder, several soles, true sprats, brown trout, blue moki, and the rather unlikely catch of a juvenile hoki in the New River estuary. Larger, turbid estuaries such as Lyttelton and New River contain large juvenile populations of pelagic sprats and pilchards, while many smelt have been sampled in the more freshwater-influenced estuaries such as the Toetoe River. We've found that seagrass meadows consistently have fish assemblages different from those in the surrounding sand and mud habitats. Also, the rich seaweed meadows of many of the South Island estuaries are in stark contrast to the sparsely vegetated northern estuaries. Bluff Harbour is especially striking with its clear waters and abundant plant assemblages.

We will use these data to extend fish-habitat predictive models we are currently completing for the North Island. The models will contribute to effective management of these important and productive fish nursery systems.

For more information contact: Mark Morrison NIWA Private Bag 109 695 Auckland Phone +64 9 375 2050 fax +64 9 375 2051 [email protected]

This survey is part of the FRST programme "Fish Usage of Estuarine and Coastal Habitats" (C01X0222)

New snails in New Zealand

A newly discovered species of Hydrobiidae in the genus Leptopyrgus, currently being described. (Photo: M. Haase)

Dr Martin Haase recently completed a two-year post-doctoral study of the taxonomy of New Zealand hydrobiid snails – small molluscs colonising freshwater and estuarine environments. Martin’s work was part of NIWA’s FRST-funded programme Biodiversity of New Zealand Aquatic Environments, and was done in collaboration with Te Papa National Museum, University of Waikato, Landcare Research and Australian Museum.

Sampling from Northland to Stewart Island has uncovered remarkable diversity in infrequently sampled freshwater habitats such as seepages, springs and groundwaters, especially in limestone-rich areas such as north-west Nelson.

Previously only 16 New Zealand species of Hydrobiidae belonging to six genera had been identified. Martin’s revision has revealed at least 63 species belonging to 15 genera. We suspect that many more species remain undiscovered.

Often, new species were found only in one locality. This, combined with the susceptibility of springs, seepages and groundwaters to modification from land-use change and water abstraction, provides important imperatives to incorporate these habitats into conservation planning and management.

For more information, contact: Kevin Collier NIWA PO Box 11 115 Hamilton Phone +64 7 856 7026 fax +64 7 856 0151 [email protected]

UV measurement: an international comparison

Dr Mario Blumthaler at Lauder adjusting the solar shading disk over the diffuser of his UV spectrometer. (Photo: R. McKenzie)

Dr Mario Blumthaler, a professor of physics at the Medical University of Innsbruck in Austria, recently visited NIWA, Lauder, to conduct measurements of UV radiation.

Dr Blumthaler is an international leader in UV research and was invited by NIWA to bring his equipment to New Zealand because his measurements complement those undertaken at Lauder. A main aim of his visit was to map the distribution of sky radiance in the UV region in the pristine atmospheric conditions at Lauder, and to relate the results to those in more polluted locations. Because Lauder is a Network for the Detection of Stratospheric Change (NDSC) site, we had available all the measurements needed for supporting model calculations. Despite the unsettled weather in February, the campaign was extremely successful and justified shipping over 400 kg of equipment to the other side of the world. An added bonus was the opportunity to cross-check calibrations of measurements at Lauder.

While in New Zealand, Dr Blumthaler worked mainly with Richard McKenzie and Mike Kotkamp.

For more information, contact: Richard McKenzie NIWA Lauder PB 50061 Omakau Central Otago Phone +64 3 440 0429 fax +64 3 447 3348 [email protected]

Recent publications by NIWA staff

Lists of the most recent publications by NIWA staff are compiled each month and posted on the NIWA website. These lists include papers published in refereed journals, proceedings, books and book chpters, as well as conference and seminar presentations and popular articles.