somelike it hot

Life in New Zealand’s Geothermal Environments Champagne Pool at Waiotapu. Photo Credit: GNS Science

New Zealand’s geothermal activity LOCATIONLOCATION occurs due to high heat flow in the Earth’s crust along the Pacific – LOCATION Australasian tectonic plate boundary. Faults and fractures channel heat to the surface creating volcanoes, hot springs, geysers, heated soils, hot streams, and fumaroles.

2 Why are geothermal areas Ngawha colourful? The brightly coloured rocks and soils in geothermal Taupō areas arise in different ways, due to chemicals Auckland Volcanic in the soil and the presence of pigmented Zone . Hot, acidic gases and fluids interact with rock to New Plymouth form colourful clay minerals. For example salmon pink is cinnabar (mercury sulphide), orange is realgar ( sulphide) and yellow to grey colours can be from sulphur-based minerals. Wellington When geothermal water discharges out of a spring or geyser, it cools quickly and forms what is known as a sinter deposit. Pure silica is white, Christchurch but sinters often contain traces of impurities or microorganisms which produce beautifully coloured forms. Some of the more common colours are pink from iron oxide or microbes, and Dunedin grey to black, from iron sulfide (pyrite). Microorganisms inhabit geothermal areas and can survive in very high temperatures. The type of The Taupō Volcanic Zone sits over the subduction zone boundary microbes will depend largely on the temperature where the Australasian and Pacific tectonic plates meet. and the chemical composition of the surrounding water, and each is pigmented differently. At lower The most well-recognised geothermal area in temperatures photosynthetic pigments produce New Zealand is the Taupō Volcanic Zone (TVZ). blues, reds and greens, while some higher This is a 100 km wide by 350 km long volcanic temperature microorganisms have carotenoid region of the central North Island. pigments that produce pinks, reds, yellows and browns. Māori legend says that geothermal fields in the central North Island were created when Te Pupu and Te Hoata, goddesses of fire, emerged from the What is that smell? Earth’s core in search of Ngātoroirangi who had That rotten egg smell in geothermal areas is due been stranded freezing on Mt Tongariro. Wherever to sulphide gas being released into the they surfaced, they left geysers, hot springs and atmosphere. Fortunately if you live here, or visit mud pools, leaving the path of geothermal activity often, you quickly get used to the smell! that remains today. Warm and hot waters are also discharging from springs throughout the country, including Ngawha and Northland, East Cape, the Hauraki and Auckland regions, around Tauranga, and along the Alpine Fault in the South Island such as Hanmer Springs.

Hot spring at Waimangu. The yellow Photo Credit: and green colours are associated with Jean Power photosynthetic microorganisms.

3 Hoani, a at Tokaanu. Photo Credit: Jean Power

Geothermal areas are unique islandson land and ecosystems that challenge the survival ability of most life forms. Their physical characteristics include high temperatures, steep soil temperature gradients, exposure to steam, highly mineralised soils and waters, extreme pH, infertile soils, and the presence of toxic metals and gases.

4 Geothermal ecosystems have a longitudinal zonation, which means the plant and animal TERRESTRIAL HABITATS life changes with distance from the heat and Fumarole margins & warm microclimates geothermal fluid source. This makes these areas Fumaroles are steam and gas vents. Constant small “islands” of unique and specialised species steam allows frost-sensitive plants to survive at the and communities. fumarole margins.

AQUATIC HABITATS Heated ground Hot pools & springs Geothermally heated soils result from heat flowing through the ground that is released at the surface Mineral waters journey through heated rocks to as steam. Ground temperatures (15 cm deep) can discharge naturally at the surface. Temperatures range from 40°C to over 100°C. Some flora species range from 30-100°C and pH from less than 1 such as the prostrate kanuka have evolved very (highly acidic) to 10 (highly alkaline). Depending on shallow root structures to avoid the heated and their chemical composition and gas content, these acidic soils at deeper soil depths. mineralised waters can be bubbly, salty, acidic, smelly or even flammable! Cooled, hydrothermally altered soils Geothermal streamsides Hydrothermally altered soils are often infertile. They have been changed by geothermal steam and Microhabitats are created where hot and cold become highly acidic, have low amounts of organic waters meet. This allows species, particularly those matter and phosphorus, and may contain toxic with tropical origins, to exist in areas that would concentrations of metals and trace elements. otherwise be too cold. What lives in or near warm water? What can live in or near heated Distinctive aquatic flora and fauna occur soils? downstream from thermal springs. Closest to the While microorganisms thrive in extreme high temperature water source (>60°C), aquatic temperatures, the hot conditions prohibit any communities are dominated exclusively by high- Eukaryotes, including any plant life and most temperature microorganisms ( and invertebrates (insects), from residing in the hottest ). As the water cools downstream (<60°C), thermal areas. However, a complex variety of a diverse array of algae and fungi appear, and then specialised microorganisms, plants and insects soft-bodied organisms (invertebrates) begin to readily colonise areas adjacent to these heated occur where temperatures are less than 50°C. areas. Cradles for early life The unusual food webs in geothermal areas may mimic conditions of the Earth billions of years ago when life originated. It is generally thought that life (primordial microorganisms) began in environments adjacent to geothermal features full of gases and toxic metals!

A diverse range of plants grows in this Photo Credit: geothermal microhabitat at Waikite. Jean Power

Fumarole and sinter terraces at Te Puia. Photo Credit: Jean Power 5 Array of geothermal habitats in a stream at Waimangu. Each colour indicates an environmental Photo Credit: Matthew Stott niche supporting different microbial life.

Microorganisms, insects and plants livingin a niche have made geothermal areas their home by adapting to extremes of temperature, acidity and alkalinity, turbidity and toxicity. The unique ecosystem biodiversity is so closely linked to chemical and physical conditions within each niche that community composition can vary between neighbouring hot springs, or even within a single pool or at different soil depths. 6 Some species and communities are endemic, The geothermal food web that is, they are found only in these habitats and locations. Where do they come from?

Many of the plant, insect and larger species are ANIMALS, BIRDS now uniquely adapted for life in geothermal areas and are exclusively found in these extreme habitats. PARASITIC FLIES Other opportunistic species have adapted to PREDATORY INSECTS tolerate geothermal conditions but are also found in non-geothermal areas. EPHYDRID FLIES The distribution and diversity of microorganisms within geothermal areas is thought to be a MICROORGANISMS consequence of: (e.g. ALGAE, FUNGI, BACTERIA, ARCHAEA) • physical dispersal by air, water, earth, and animals, Microorganisms are the backbone of the food • natural selection to the environmental web in all geothermal ecosystems, but even more conditions, and so in environments where conditions do not allow • beneficial DNA mutation by the species. photosynthesis. In these cases, microorganisms can use gases, such as and hydrogen sulphide, or metals, such as iron or arsenic, as energy sources. Other microorganisms are decomposers, with the ability to recycle nutrients from other organisms’ waste or break down plant material for energy and carbon. In turn, these primary producing microorganisms can be predated by other organisms in the food web. Grazing insects such as shore flies and midges are found in abundance living and feeding on microbial mats (up to 50°C). Predatory insects live on the cooler edges of hot springs and streams and feed on the larvae and other detritus. The adult geothermal-living insects then become prey for land-based predatory insects and birds.

Hot spring at Waimangu. Photo Credit: Jean Power

7 Silica sinters growing at the margin of Champagne Pool, Waiotapu. Photo Credit: Bruce Mountain

Microorganisms are present in almost extremophiles every environment on earth, including in the heated water-bodies and soils of geothermal environments. As a general definition, microorganisms are any life form that cannot be seen without magnification. Examples of microorganisms can be found in all three kingdoms of life including Eukaryotes (for example protozoa, algae and some fungi), Bacteria and Archaea. 8 Some microorganisms, primarily bacterial and Where are they? archaeal species, are the only life forms that survive While the individuals are invisible to the naked eye, such harsh conditions. Temperatures can be up these micro-communities can be “seen” in some to 122°C, the pH can range from highly acidic characteristic features of a geothermal ecosystem. to strongly alkaline, and there can be elevated concentrations of salts and/or heavy metals. These unique forms of microorganisms are appropriately termed ‘extremophiles’.

Extremes of temperature

deep sea vents 120°C HYPER- THERMOPHILES 100°C water boils 80°C hot springs 60°C scalding water THERMOPHILES warm springs body Scanning electron microscope image of Photo Credit: 40°C Kevin Lee temperature MESOPHILES thermophilic bacterium Chthonomonoas calidirosea. 20°C surface water

0°C water freezes ice PSYCHROPHILES A distinctive characteristic of algae and cyanobacteria is their ability to form microbial mats and films. Some mats change colour with the Extremes of pH season and sunshine hours, being dark green in crater lakes winter and orange in summer. 0 stomach acid acidophiles lemon juice acid springs In some areas, the silica structures are shaped the 2 vinegar way they are due to interaction with the microbial 4 communities. For example, when silica precipitation and microbial mats occur together, the mats are 6 neutrOPHILES pure water neutral springs encased in silica forming a spectacular structure. 8 seawater Many of the pink, yellow and orange colours 10 soap alkaline springs ammonia seen on silica terraces and structures are due to 12 alkalIPHILES pigmented microorganisms.

Microbial community members Microorganisms derive energy either via photosynthesis or via the chemical oxidation of organic or inorganic compounds. Photosynthetic microorganisms including algae, cyanobacteria and a small number of other bacterial species are capable of living in geothermal environments, but are limited to temperatures less than 65°C. Conversely, microorganisms generating energy from chemical oxidation processes use gases (e.g. methane or hydrogen), metals (e.g. iron) or organic compounds (e.g. sugars, fats or Whangapoa, hot spring Photo Credit: protein) as energy sources. They can be found near Atiamuri. Duncan Graham at temperatures up to 100°C in New Zealand’s terrestrial environments.

9 Chironomus larvae (midge) commonly found in geothermal areas. Photo Credit: Ian Hogg

Few invertebrate species live only in insects thermal areas. Most are pre-adapted to the high temperatures and low pH, or are found in geothermal waters as temporary visitors. Some proliferate in high abundance because there is less competition and fewer predators.

10 The factors regulating distribution are temperature, Diptera (flies) and Coleoptera (beetles) have the pH and food availability. Fewer invertebrates greatest tolerance to high temperatures with occur in close proximity to geothermal areas individuals having been found in waters of up to than in cooler neighbouring areas. The resident 55 °C. The most common geothermal specialists communities are also more diverse and abundant are the Ephydridae (the shore fly), chironomid where different habitats are available, for example, midge (Tanytarsus), the endemic mosquito (Culex sinter terraces support less life than areas rotoruae) larve and the larvae and adults of populated by vegetation. hydrophilid and dytiscid beetles. Invertebrate fauna includes: Acclimatised macroinvertebrates include Odonata (damselflies),Chironomus (midges), Hemiptera • Residents – specialist species found only in (swimming bugs) as well as a range of other flies, geothermal ecosystems that do not occur in beetles and a few snails. neighbouring colder areas. • Adapters – species also resident in non- geothermal areas that are tolerant of geothermal conditions. • Migrants - temporary visitors who transit areas influenced by geothermal heat and steam; some regularly, others only in winter. • Foragers – these predatory insects do not reside in geothermal ecosystems, but visit to raid the carcasses of other invertebrates that have been killed or knocked down by rising steam near hot springs and streams.

Fly grazing on geothermal Photo Credit: Duncan Graham microbial mat.

Acid versus alkaline environments Alkali-chloride and/or bicarbonate environments tend to have a community dominated by midges, ephydrid flies and cyanobacteria. Acid-sulfate and/or chloride waters tend to have communities dominated by Chironomus flies along with various other Diptera flies and diatoms.

Insect larvae living on a microbial mat in a Photo Credit: geothermal seep at Ngatamariki. Duncan Graham

11 Otamakokore geothermal stream flowing from the Te Manaroa spring at Waikite. Photo Credit: Karen Houghton

In New Zealand, geothermal vegetation geothermal has been identified as an ecosystem of historically limited extent, and naturally plants rare, even in pre-human landscapes. Combinations of temperature, chemistry, hydrology, and localised protection from frosts, produce rare and unusual habitats for plants.

12 Heat flow through the soil is the most important What can I see? factor in determining the vegetation that can thrive Prostrate kanuka only occurs in geothermal in geothermal areas. habitats. It is low in stature, becoming shorter Plants also must tolerate highly acidic soils with little as soil temperatures increase, and has shallow organic material, phosphorus and aluminium, but roots that enable it to survive in geothermal areas. high concentrations of metals and trace elements, Groundcovers are often a turf of unusual mosses, such as arsenic. liverworts, and lichens. Vegetation assemblages at geothermal sites Other species that are usually found only in include lichenfield, mossfield, herbfield, fernland, warmer climates can also survive in the higher scrub, shrubland, rushland, sedgeland, reedland, temperatures found in geothermal areas. forest, wetland and open water habitats. The constant presence of steam around hot They occur over a wide range of altitudes, from springs, fumaroles and streams allows frost- sea level to the summits of the Central North Island sensitive species to survive. Some geothermal volcanoes and Mt Tarawera. areas are home to rare tropical ferns and orchids that grow nowhere else in New Zealand. A number of plants found in geothermal sites in New Zealand are listed as threatened or at Some plants that occur in non-geothermal areas risk. These include orchids, grasses, ferns and can also adapt to tolerate conditions in geothermal prostrate kanuka. habitats. Examples include the low fertility shrublands of mingimingi, manuka and monoao.

Prostrate kanuka growing by a Photo Credit: Dicranopteris linearis (tangle fern) Photo Credit: geothermal spring at Waimangu; this Julie Deslippe at Karapiti. This tropical fern only Julie Deslippe species dominates geothermally altered survives in New Zealand in warm and heated soils in New Zealand. geothermal areas.

13 Red pigmented spring at Te Kopia - the colour is due to microoganisms and precipitated iron. Photo Credit: Mathew Stott

Geothermal habitats often generally EXTREMESURVIVAL have low biodiversity. There are limited types of species but they can be in a high abundance. The plant, animal and microbial species have evolved characteristics to help them survive in geothermal conditions.

14 Special characteristics of life in geothermal areas Threats include smaller sizes and slower growth rates Development of geothermal fields, land use change compared to their non-geothermal counterparts. and pest invasion have already had an impact on Some plants have shallower roots and only existing geothermal environments. intermittently flower. Extraction of geothermal energy for power Microorganisms have had to invent new ways generation and heating uses have affected surface of doing things too. For example, thermophilic activity, changed soil and hot spring temperatures, microorganisms utilise temperature stable and resulted in ground subsidence. enzymes to carry out metabolic functions. Likewise extremophilic microorganisms often synthesise Some flora and fauna that do not require the unusual fats to ensure the integrity of their cell thermal features for their survival, but have learnt to membranes to these extreme conditions. adapt to thermal areas, have become threats to the unique geothermal species. Resilience to change Additionally, some imported warm-water aquarium These geothermal communities need to be resilient species have been released into the environment to changing environmental conditions. and now thrive only in warmer geothermal waters, Hot springs, geysers, mud pots, and fumaroles are competing with indigenous fauna and flora for dynamic surface features that are sensitive to any resources. changes in their underground water supply. Blackberry (Rubus fruticosus agg.) is a major Geothermal features are easily affected by natural problem in some areas, as is buddleia (Buddleja events such as earthquakes and landslides. Man- davidii), wild introduced conifers and some exotic made impacts also include the development grasses. of geothermal power stations and drilling of Animal stock and people can trample vegetation geothermal bores for domestic and commercial when areas are not fenced. heating. This can all result in natural changes to Protection of geothermal areas temperature, water levels and chemistry. Geothermal areas are often protected because the geothermal features, fauna and flora are rare and easily damaged. Five geothermal areas, White Island (Whakaari), , Waimangu, Waiotapu and Tongariro, are considered to be of international significance and preservation takes precedence over development in these areas. Management of geothermal systems aims to balance development activities with the protection of highly-valued surface features and ecosystems.

Landscape immediately following a Photo Credit: hydrothermal eruption at Ngatamariki. Bruce Mountain

Monitoring geothermal environments is Photo Credit: an important part of sustainable resource GNS Science management. moreinformation www.1000springs.org.nz www.gns.cri.nz/extremophiles www.gns.cri.nz/geothermalecosystems

acknowledgements

Geothermal research funding from the New Zealand Government.

GNS Science Miscellaneous Series 77, ISBN 978-0-478-19910-9 ISSN 1177-2441 (Print), ISSN 1172-2886 (Online) May 2015

FRONT/BACK COVER: Boiling springs at Whakarewarewa. Photo Credit: GNS Science 16