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Geosciences Column: From the desolate to the diverse, a story of volcanic succession

18 Jul

When a volcano erupts and spews lava onto the surrounding terrain, it is merciless in its destruction. All that is green on the land is engulfed in flame, or buried by an insurmountable mass of molten rock. Whatever charred remains of what lies beneath it will not see the light of day once the lava cools, turning the landscape into a barren black mass of solid basalt.

But volcanoes around the world are not barren basaltic masses. On the contrary, many volcanic slopes are teeming with life. Much of the Hawaiian archipelago is a tropical paradise, its older lava fields thick with forest and foliage. Likewise, Iceland’s flotilla of fiery peaks hasn’t rendered the land completely barren. So how does life return to the scene after an eruption?

Hardy grass on Surtsey’s black sands. (Credit: Ragnar Sigurdsson (arctic-images.com via imaggeo.egu.eu)

Hardy grass on Surtsey’s black sands. (Credit: Ragnar Sigurdsson (arctic-images.com via imaggeo.egu.eu)

The answer lies in a process known as succession. One by one, starting with the hardiest life forms, the lava is recolonised by wind-blown spores and seeds that have managed to make it from areas unharmed by the latest eruption. Over time, the growing community of plants attracts animals that bring further seeds to the site, either clinging desperately to their fur, or deployed stealthily in their droppings.

A long-term investigation of two very different volcanoes has revealed what allows the earliest arrivals to take hold: Surtsey, an isolated volcanic island in the North Atlantic, and Mount St. Helens, a once towering and peak in Washington State. The findings are published in Biogeosciences, an open access journal of the European Geosciences Union.

Surtsey’s arrival in 1963 (left, credit: NOAA) and Mount St Helens during the 1980 eruption (right, credit: Austin Post/USGS)

Surtsey’s arrival in 1963 (left, credit: NOAA) and Mount St Helens during the 1980 eruption (right, credit: Austin Post/USGS)

Surtsey emerged off the Icelandic coast in 1963 amid billowing plumes of ash and steam. Erupting from underwater, Surtsey created its own island – a fresh field of lava that has been consistently monitored since 1990. Mount St Helens erupted violently in 1980, after a catastrophic landslide triggered a volcanic blast so large that the volcano’s entire north flank, together with 370 square kilometres of forest, were obliterated. The resulting fields of pumice, tephra and lava provided a blank canvas for life to start afresh in the area.

Surtsey and Mout St Helens differ in terms of their age, the way they’re isolated, their climate and their size. But, despite these differences, scientists Roger del Moral and Borgþór Magnússon found the way vegetation first established itself followed the same fundamental principles, regardless of where it set up camp.

It’s all down to two different filters: isolation and stress. Isolation creates the biggest filter; meaning only the most well-travelled species can take hold. Then stress further sorts the species that can survive – well-travelled weaklings wouldn’t stand a chance in a place with incredibly poor fertility.

Birds make life a little easier for all involved, particularly in coastal areas, where an entire colony of birds can become established. These birds import nutrients from the surrounding sea by consuming fish from and depositing their waste on land. On Surtsey, these nutrient imports have meant the richest plant life has developed where the bird colonies are.

On Mount St Helens, winds carrying nutrient-laden dust created the first fertile material. This let a group of flowering plants known as lupines take hold and, after several cycles of lupine blooms, the ground became much more fertile. The areas where lupines bloom are now the most species rich.

Vegetation on Surtsey (top, credit: Borgþór Magnússon) and Mount St Helens (bottom, credit: Roger del Moral). Images on the left are areas where the rate of succession is slow, those on the right detail areas with a faster succession rate.

Vegetation on Surtsey (top, credit: Borgþór Magnússon) and Mount St Helens (bottom, credit: Roger del Moral). Images on the left are areas where the rate of succession is slow, those on the right detail areas with a faster succession rate.

In a world where environments are rapidly changing and species are having to move into new territories to adapt, these findings can help shed light on how plants could keep pace with the change as they shift from one site to the next.

By Sara Mynott, EGU Communications Officer

Reference:

del Moral, R. and Magnússon, B.: Surtsey and Mount St. Helens: a comparison of early succession rates, Biogeosciences, 11, 2099-2111, doi:10.5194/bg-11-2099-2014, 2014.

 

Geosciences Column: Meshing models with the small-scale ocean

12 Jun

The latest Geosciences Column is brought to you by Nikita Marwaha, who explains how a new generation of marine models is letting scientists open up the oceans. The new technique, described in Ocean Science, reveals what’s happening to ocean chemistry and biology at scales that are often hard to model…

Diving into the depths of the ocean without getting your feet wet is possible through biogeochemical modelling – a method used by scientists in order to study the ocean’s living systems. These simulated oceans are a means of understanding the role of underwater habitats and how they evolve over time. Covering nutrients, chlorophyll concentrations, marine plants, acidification, sea-ice coverage and flows, such modelling is an important tool used to explore the diverse field of marine biogeochemistry.

Barents Sea plankton bloom: sub-mesoscale flows may be responsible for the twisted, turquoise contours of this bloom (Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC)

Barents Sea plankton bloom: sub-mesoscale flows may be responsible for the twisted, turquoise contours of this bloom (Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC)

There is one outstanding problem with this technique though, as the very-small scale or sub-mesoscale marine processes are not well represented in global ocean models. Sub-mesoscale interactions take place on a scale so small, that computational models are unable to resolve them. Short for sub-medium (or ‘sub- meso’) length flows – the smaller flows in question are on the scale of 1-10 km. They are difficult to measure and observe, but their effects are seen in satellite imagery as they twist and turn beautiful blooms of marine algae.

Sub-mesoscale phenomena play a significant role in vertical nutrient supply – the vertical transfer of nutrients from nutrient-rich deep waters to light-rich surface waters where plankton photosynthesise. This is a major area of interest since the growth of marine plants is limited by this ‘two-layered ocean’ dilemma. But the ocean is partially able to overcome this, which is where sub-mesoscale flows come in. Sub-mesoscale flows are important in regions with large temperature differences over short distances – when colder, heavier water flows beneath warmer, lighter water. This movement brings nutrient-rich water up to the light-rich surface. Therefore, accurately modelling these important small-scale processes is vital to studying their effect on ocean life.

Global chlorophyll concentration: red and green areas indicate a high level or growth, whereas blue areas have much less phytoplankton. (Credit: University of Washington)

Global chlorophyll concentration: red and green areas indicate a high level or growth, whereas blue areas have much less phytoplankton. (Credit: SeaWiFS Project)

A group of scientists, led by Imperial College’s Jon Hill, probes the technique of biogeochemical ocean modelling and the issue of studying sub-mesoscale processes in a paper recently published in the EGU journal Ocean Science.  Rather than simply increasing the resolution of the models, the team suggests a novel method – utilising recent advances in adaptive mesh computational techniques. This simulates ocean biogeochemical behavior on a vertically adaptive computational mesh – a method of numerically analysing complex processes using a computer simulation.

What makes it adaptive? The mesh changes in response to the biogeochemical and physical state of the system throughout the simulation.

Their model is able to reproduce the general physical and biological behavior seen at three ocean stations (India, Papa and Bermuda), but two case studies really showcase this method’s potential: observing the dynamics of chlorophyll at Bermuda and assessing the sinking detritus at Papa. The team changed the adaptivity metric used to determine the varying mesh sizes and in both instances. The technique suitably determined the mesh sizes required to calculate these sub-mesoscale processes. This suggests that the use of adaptive mesh technology may offer future utility as a technique for simulating seasonal or transient biogeochemical behavior at high vertical resolution – whilst minimising the number of elements in the mesh. Further work will enable this to become a fully 3D simulation.

Comparison of different meshes produced by adaptive simulations: (a) Bermuda, taking the amount of chlorophyll into account (b) the original adaptive simulation at Bermuda, without taking chlorophyll into account (c) adaptive simulation at Papa, taking the amount of detritus into account (d) the original Papa simulation, without taking detritus into account. (Credit: Hill et al, 2014)

Comparison of different meshes produced by adaptive simulations: (a) Bermuda, taking the amount of chlorophyll into account (b) the original adaptive simulation at Bermuda, without taking chlorophyll into account (c) adaptive simulation at Papa, taking the amount of detritus into account (d) the original Papa simulation, without taking detritus into account. (Credit: Hill et al., 2014)

The fruits of this adaptive way of studying the small-scale ocean are already emerging as the secrets of the mysterious, sub-mesoscale ocean processes are probed. The ocean holds answers to questions about our planet, its future and the role of this complex, underwater world in the bigger, ecological picture – adapting to life and how we model it may just be the key we’ve been looking for.

By Nikita Marwaha

Reference:

Hill, J., Popova, E. E., Ham, D. A., Piggott, M. D. and Srokosz, M.: Adapting to life: ocean biogeochemical modelling and adaptive remeshing. Ocean Sci., 10, 323- 343, 2014

Imaggeo on Mondays: Long-lived lakes have a lot to tell

2 Jun

The world’s oldest, deepest freshwater lake lies in southeast Siberia: Lake Baikal. Stretching some 600 kilometres across the Russian landscape, Baikal marks what the very early stages of a new ocean – an ancient rift that cleaved the centre of Asia apart throughout the Palaeozoic, Mesozoic and Cenozoic. Today, there are still signs of tectonic activity and the rift continues to diverge 4 mm further apart each year. Much like the East African Rift, Baikal provides scientists with a window into the way oceans are formed.

Where the Selenga River meets Lake Baikal. (Credit: Galina Shinkareva via imaggeo.egu.eu)

Where the Selenga River meets Lake Baikal. (Credit: Galina Shinkareva via imaggeo.egu.eu)

The Selenga River, which snakes across Asia for over 900 km, brings 30 cubic kilometres of water and more than 3.5 million tonnes of sediment to the basin each year, feeding a rich wetland ecosystem at the northern end of the lake. What’s more, the lake’s age and isolation has led to the establishment of a unique world of underwater flora and fauna – 70% of the lake’s inhabitants are found nowhere else in the world. This combination has earned the lake the nickname ‘The Galapagos of Russia’ and its designation as a World Heritage Site, as well as providing a prime site for evolutionary studies.

Not only that, but the lake is a key spot for climate science too. Baikal’s high latitude location means that it’s particularly sensitive to comate change, leading to numerous investigations into how climate has varied over the last 250,000 years. No doubt we have a lot more to learn from this incredible environment.

By Sara Mynott, EGU Communications Officer

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Geosciences Column: Could plants be a cheap solution to soil contamination in developing countries?

30 May

There are many ways to remove contaminants from the land, but it is a constant battle for scientists to find better and cheaper ways to the job. Recent research published in Soild Earth suggests plants may present a solution – one that’s particularly promising for poor areas. Jane Robb describes the findings…

Bolivia has a long and complicated mining history, going back to the 1500s. Untreated tailings are commonly left in rivers, causing widespread contamination of waters and soils downstream. These wastes often contain pyrite, which generates sulphuric acid when exposed to oxygen and water, leaching the surrounding rocks of heavy metals in a process known as acid mine drainage. Mines in Bolivia also use sulphuric acid in the mining process, which catalyses production of acid rock discharge. With growing conflict over the rapid environmental degradation that is causing public health problems across the country, the Bolivian government declared an emergency zone in the Huanuni watershed in 2009, just one of the areas in which heavy metal contamination occurs.

Acid mine drainage causing contamination of water and soils in areas close to Rio Tinto, Spain. (Credit: Carol Stoker, NASA)

Acid mine drainage causing contamination of water and soils in areas close to Rio Tinto, Spain. (Credit: Carol Stoker, NASA)

Soil heavy metal contamination has serious effects on microbial life and the taxonomic diversity of soils, not to mention the serious health effects that high concentrations of elements such as As, Cd, Cr, Hg and Pb can have. Other metals like Cu, Ni and Zn are also released, and although they are essential for growth, they can cause problems when present in high concentrations. While heavy metal remediation in soils is a highly researched topic, we can still do more. This year, Jorge Paz-Ferreiro and his team et al have assessed two techniques that use plants for mine waste remediation: adding biochar to the soil and planting hyperaccumulators (plants that can store heavy metals at levels 100-fold greater than common plants without reducing their growth) in the affected area. Both of these techniques could be applied to sites like Huanuni in the future.

Prevention is the best way to fight soil and water contamination from mining, but in countries such as Bolivia, the political and cultural environments can present barriers to progress in this area. The country’s history of low economic diversification, corruption and political instability (democratically elected governments only began in 1982), and rapid inflation have continually hindered development. In addition, low population growth, high incidence of disease and low life expectancy exacerbates the country’s economic position – 86th out of 179 countries in the World Bank’s GDP ratings in 2012. Bolivia’s principal commodity for export is natural gas, but until the 1980s mining of tin and silver were its top economic exports. Although mining is not as prevalent in the country as it was in the past, the country still suffers from the impacts hundreds of years of mine tailings have brought to the environment. For Bolivia, prevention is a small part of what needs to be done to tackle the problem of soil and water contamination.

The extraction, filtration or stabilisation of heavy metals using hyperaccumulators (a process commonly known as phytoremediation) is nothing new. In fact, it has been studied and used for years as a remediation technique with varying success. But with costs that are a fraction of that spent on traditional remediation techniques – at a few cents per square metre for cleanup or removal of material compared to up to $300 per square metre– phytoremediation could be a viable option for countries such as Bolivia.

Mining in Bolivia in 1981. (Credit: Wikimedia Commons user Meister)

Mining in Bolivia in 1981. (Credit: Wikimedia Commons user Meister)

Paz-Ferreiro’s team are the first to assess the possibility of using biochar in combination with phytoremediation to remediate heavy metal contamination in soils. Phytoextraction uses hyperaccumulators to take up heavy metals and transfer them to aboveground tissues, such as stems and leaves. This process takes the contaminant from the soil to the plant, providing a way to extract economically valuable metals while improving soil – and therefore crop – quality. Phytofiltration sequesters pollutants from waters through the plant’s root system, and phytostabilisation limits the mobility and bioavailability (availability to plants and animals) of polluting substances by immobilising them. While phytoextraction is the most common and promising technique, both filtration and stabilisation help remove contamination from soils and reduce the probability of heavy metals being stored within crops.

Although phytoremediation is currently used and holds a lot of promise, there are still issues associated with this technique. For instance, phytoremediation may not be suitable in areas of elevated contamination, as plants could begin to suffer from the soil’s toxicity, and many known hyperaccumulators produce low amounts of biomass, meaning that heavy metals are removed slowly. Information is also missing on how climate change could impact the ability of phytoextractors to take up heavy metals. Most importantly, research on phytoremediation has, to date, focused on laboratory tests – more data from field experiments is needed to inform scientists about the impacts of microclimate and soil type on the effectiveness of phytoremediation.

Modern mining in Seite Suyos, Bolivia, devastates the surrounding environment. (Credit: Wikimedia Commons user Mach Marco)

Modern mining in Seite Suyos, Bolivia, devastates the surrounding environment. (Credit: Wikimedia Commons user Mach Marco)

Biochar is formed from burning other organic materials – ranging from plants to manure. Biochars act on the bioavailable heavy metals in soils, reducing the amount that can be leached from the soil by crops. Heavy metals stick to the surface of biochar, and because they have a high surface area, they are the ideal medium for this task. Some biochars can also stabilise heavy metals by helping them precipitate as carbonate, phosphate and sulphate compounds. Unlike phytoremediation, biochar does not reduce the amount of heavy metals in the soil, but instead reduces the bioavailability of these elements.

As biochars effectively stabilise heavy metals, they reduce their ability to be taken up by plants, preventing phytoextractors from doing their job. This means that the use of biochar and phytostabilisors would be a more useful remediation approach. Paz-Ferreiro and his colleagues indicate that it could be possible to use biochar and phytoextractors together, if the biochar and phytoextractors target different heavy metals in heavily contaminated soils. Much larger, long-term trials are needed to see how well the two methods work together – something that will need to be tested in the lab and the field.

Today, the scale of mine-related contamination in Bolivia and the emergency zone of Huanuni is still staggering. To remediate contamination not only does the government need to address the continual contamination of soil and water, but also historical contamination. Paz-Ferreiro’s team have brought together two methods for soil heavy metal remediation that can help address historical contamination in areas such as Huanuni, and have hopefully paved the path for more research with these combined remediation techniques in the field.

By Jane Robb, Project Assistant, University College London

Reference:

Paz-Ferreiro, J., Lu, H., Fu, S., Mendez, A., Gasco, G.: Use of phytoremediation and biochar to remediate heavy metal polluted soils: a review, Solid Earth, 5, 65-75, 2014.

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