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Fifteen

Time for action?

Forum: Climate Change…

Time for action?

Time for action?

Forum: Climate Change

In Scotland and around the world, the evidence for climate change is mounting all the time, and the sea is one of nature’s best barometers. Marine ecologists in Scotland are not only helping to monitor the rate of climate change, but also trying to do something about it – and set the pace for similar research around the world.

The climate always changes (something called “natural variability”) but according to the evidence, the rate of change in recent years has started to accelerate, and due to an increase in carbon emissions, temperatures are increasing and sea levels are rising. More frequent and more violent storms are starting to persuade the general public that climate change is really happening, but most marine ecologists are no longer debating whether or not the change is real but are trying to establish how fast it is accelerating and come up with a strategy to deal with it – or at least manage its impact in the future.

These were the conclusions of a recent panel discussion on climate change involving Dr Nick Kamenos of the University of Glasgow, Dr Natalie Hicks and Dr Henrik Stahl of SAMS (the Scottish Association for Marine Science) and Dr Heidi Burdett from the University of St Andrews, chaired by Professor David Paterson, Executive Director of MASTS (the Marine Alliance for Science and Technology for Scotland).

“We are more certain now that climate change is happening,” says Stahl, “but there are still many questions to answer.”

For Paterson, the evidence for climate change is becoming increasingly clear; rising sea levels are hard to ignore (a global average of 3 mm per year and an estimated 1.5 mm in Scotland), and increasing acidification of the sea (more carbon dioxide dissolved in the water). No single figure tells the full story, however.  At the moment, global temperatures even appear to be falling, but this is just because they’re on “the downward part of an upward trend” – in other words, the average is rising but in some years there is a temporary drop along the way. As Paterson puts it: “The climate is not the same thing as the weather.” Also, the impacts will be very different across the globe, but Scotland will not be immune.

The Scottish marine context

Kamenos cites two examples of “wonderful” marine habitats in Scotland which are particularly vulnerable to physical and chemical damage: maerl (coralline red algae) and cold-water corals.

Maerl is an unusual type of algae which grows in shallow unpolluted waters. It grows very slowly (about a quarter of a millimetre a year) and plays a key role as an ecosystem service provider – a “kindergarten” for juvenile fish. This ecosystem would take thousands of years to recover from serious damage and this would mean not just a loss of habitat, but also a reduction in the fish population. 

Corals are not confined to tropical water. Scotland has its own coral habitats and the full extent of the cold water coral mounds in the Atlantic was only recently recognised. Cold-water corals grow faster than maerl and cover very large areas. Like maerl, they also rely on producing hard calcareous coverings, and they also form important nurseries for fish. However, the coral beds are fragile and are easily damaged by physical disturbance (fisheries) or environmental changes (e.g. temperature, ocean acidification). 

These sensitive maerl and coral habitats are not so well known in Scotland, but other anecdotal evidence of changing environmental conditions from more familiar habitats is increasing. For example, the shells of mussels being farmed on the west coast of Scotland are softer than in the past, making them more vulnerable to predators. This may be a response to climate change and, as water warms, other species (e.g., jellyfish, algae and invertebrates) may “invade” and displace the indigenous species, causing disruption of the natural ecosystem. This problem of invasive species is widely recognised but very difficult to manage, and some regions (the Clyde area, the Hebrides and Shetland) are developing “biosecurity” policies to manage the threat of these potential invaders.

However, a marine ecosystem is a highly complex network of interactions which are hard to fully understand and predict, and not all the news of climate change is bad news. Some species will be winners and others losers, says Hicks. For example, kelp (large brown algae) may become more abundant as the temperature rises, increasing coastal productivity and creating economic opportunities, but there are also dangers.

According to Burdett, the increase in sulphur gases (dimethylsulphide or the “smell of the sea”) released into the atmosphere by algae, because of rising temperatures, forms clouds which help reduce warming – a paradoxical “knock-on” effect that has to be included in the scientific mix. The planet also has a “climate regulation mechanism” which keeps things in a state of equilibrium most of the time, but the evidence is mounting that human activity has “upset” this natural balance since the start of the industrial age. Says Paterson: “The engine of the Earth’s biogeochemistry is bacterial metabolism, and after millennia of evolution we have reached the point where we may be superseding the bacteria as agents of climate change ”

What can we do?

It may be hard to get agreement on long-term solutions but “doing nothing is not an option” for scientists like Paterson. “There's much more we can do and much more we should do,” he says. “In addition to raising awareness and basic measures like better transport and reducing our power consumption, we can adjust our fisheries policies (including eating different fish and better targeting of fish stocks) and plan to cope with  rising sea levels by managing coastal defence more efficiently. We can also manage natural habitats, enhance marine environments and provide advice on the deployment of renewables.”

According to Stahl, we can also create marine protected areas which give the ecosystems a chance to recover. “By saving relatively small areas,” he says, “you can get huge economic benefits over the longer term.” And the first step towards doing something about it is to fully understand what’s going on.

Even if we stop polluting now and eliminate carbon emissions completely, the environment will continue to change, and some habitats may never recover. Paterson believes we are already past “the tipping point” and that a two-degree centigrade rise in global temperatures is unavoidable. Stahl is frustrated that “no-one wants to take the first step” in addressing the problem, despite
the fact that measures such as carbon capture and storage (CCS) could reduce emissions by as much as 25%. “The technology is there but not the incentives,” he says. “CCS could make a difference, but is seen as too expensive.”

Public opinion

In coastal areas, it’s possible to manage the impact of rising sea levels, but Burdett says the problem with the sea is “out of sight, out of mind,” and that “the further you go out, the more uncertainties there are and the greyer international legislation becomes.”

Hicks describes public opinion as “jaded” and thinks that all the “doom and gloom” of climate change discussion in the media can turn people off. She also wants to see more coverage of positive developments – for example, the fact that we know more and thus can avoid future problems, as well as the emergence of new industries such as seaweed-based products as a side-effect of temperature changes.

More “scientific” coverage would also raise the standard of public debate, drawing attention not just to the “hidden depths” of the ocean itself but also to the complexity of climate change. Personal experience can be misleading, says Paterson, particularly when people jump to conclusions after very hot summers or very cold winters. 

“It’s important to focus on what is most relevant to the general public and how a particular biogeochemical cycle relates to them personally,” says Kamenos. “We should talk about resources like fishing and explain natural variability and the huge timescales involved.” 

Kamenos thinks drawing attention to rising sea levels is one of the best ways to demonstrate changes in climate, because they are something that everyone can see and relate to – especially if people are “hit in their wallets.” If the Greenland ice sheet melts, sea levels will go up by 7-8 metres, but what makes people sit up and notice today is when insurance companies increase their premiums or even refuse to cover some homes because of the danger of flooding. 

“We can never make precise predictions,” Paterson adds, “but we can advise on how to adapt to the changes, to put in place the strategies and green measures needed. We can also help to re-create the habitats which are good at dealing with change – for example, mangrove swamps and salt marshes.” and new technology will be a major part of the scientists' toolkit, whether it is used to implement physical measures or simply to help to monitor the rate of change so people can prepare for the worst.

Smart sensors

Top of most environmental scientists' wish list is the funding to set up a network of intelligent sensors that covers the globe, to monitor what's happening in coastal waters and the deep ocean. The sensors would be costly to install and maintain, but they would gather valuable data over the long term, which could be put in databases open to the public. One problem, however, is that governments operate in five-year cycles rather than the 30–40 years ecologists say they would need. According to Stahl, US researchers are already building large networks of sensors, but Europe has been slow to get going. 

Instrumental data plays a critical role in understanding current and historical trends in the climate, but the picture is far from complete – e.g., baseline data for acidification. Ocean temperatures have only been measured in detail since the mid 1850s and Burdett says acidification is a “relatively recent problem” which has only been monitored for about the last decade. According to Hicks, we are “only starting to develop reliable sensors to measure pH and carbon dioxide,” and new technology is needed. Scientists also need to know how to use “smart” devices and process the data.  For example, says Paterson, “pH has weather” and varies through the day and in different locations – e.g., open ocean versus coastal systems and near CO2 vents on the seabed.

Taking advantage of the latest technology, Hicks and her colleagues at SAMS have been conducting experiments to observe the effects of changes in temperature and levels of carbon on micro-organisms living in the mud; but sometimes this can feel like “taking one step forward, two steps back”, as the results prove much more complex than expected. Stahl explains that sediments are carbon sinks and that it's important to understand the “potential feedback effects” as temperatures and carbon dioxide levels continue to rise, in coastal areas and the deep ocean. “Acidification may increase or decrease the ability of micro-organisms to process and sequester carbon,” says Stahl, who is also concerned about hypoxia – when excess nitrogen and phosphorus feeds algal blooms which starve the sea of oxygen, killing marine life. 

“This is one part of a much bigger puzzle,” says Stahl. “And it's only by working together that we can prove that climate change is happening and address the many complex issues involved.” 

“No single piece of research can provide the whole answer,” adds Kamenos, “and that is why government organisations analyse all the available literature to find common trends, examining different components of climate change over the long term.” No computer model or reconstruction is perfect, he adds, but when hundreds of reports show ocean temperatures are rising, and instrumental data matches simulations, that tends to confirm the trend. For example, says Kamenos, when you model the climate based on “natural” factors alone (including variations caused by volcanic eruptions, etc.) and compare this with the instrumental data from the real world, there is a gap between the model and reality. When you add anthropogenic and natural factors together and compare this with the instrumental data, the figures match more closely – thus demonstrating that the climate is being affected by human activity.

 

Scotland the test bed?

The problem with ecology, according to ecologists, is not just the complexity but also the timescales involved, and natural variability can be confusing. For example, says Burdett, there are very large changes in carbon dioxide and oxygen levels in the vicinity of coral reefs over the course of a day, so you have to be careful how you measure and analyse data. Studying one factor in isolation may lead to certain conclusions, but as soon as you add other factors, the complexity increases exponentially. When you study the responses of an individual species, you also have to look at how it interacts with other species. Says Paterson: “We tend to think in terms of individual factors, but the real environment integrates everything – living organisms are affected by multiple factors.” For example, when the temperature rises and the icecap melts, a “feedback mechanism” comes into play, which makes it harder to predict how much the ocean will expand. If you focus on what seems to be the single most damaging factor – e.g., carbon dioxide or nitrate or phosphate pollution – this can limit your perspective. “When you combine two different stressors, the effect is not just additive, but can be synergistic,” says Paterson.

People think in terms of generations, and the shorter the timescale, the “noisier” the data may appear and the less people tend to believe any change is occurring. To solve this problem, scientists use proxies such as fossils, shells and sediments to recreate a model of the climate in the past and compare this with current conditions and trends, to demonstrate that change is really happening. 

“We don't want to be backed into a corner,” says Kamenos, “without any options. We can't sit back waiting for something to happen then think we can do things, like stopping pollution, and all will be fine. The climate system has a lot of inertia in it. Even if we stop emissions now, there's still a century of change ahead, and that’s why it’s important to do something now.” 

When it comes to climate change, the members of the panel say we need an holistic approach – for example, joining forces with economists and industry, as well as helping governments draw up new legislation. They also think that Scotland could become an international “marine laboratory” to monitor the rate of climate change and help develop strategies to mitigate adverse effects, with MASTS researchers playing a key role. The waters around Scotland's coast are a rich source of energy (oil and gas, wave, wind and tidal) and food (fish and seaweed, etc.), so whatever we can do to protect these resources and advance the sum of scientific knowledge would have a major impact on the economic future of the country, as well as the rest of the planet. 

The panel

Dr Henrik Stahl is a Principal Investigator in Marine Biogeochemistry at SAMS, where he has been based for the last seven years. His scientific work focuses on benthic mineralisation, with an emphasis on carbon and nitrogen cycling in coastal and deep-sea sediments. He is also particularly interested in sediment–animal relations, such as solute and particle transport induced by the macrofauna and the associated effects on the oxygen and pH dynamics in marine sediments, as well as the development and application of new microsensor technology.

Dr Nick Kamenos is an Honorary Lecturer in the School of Life Sciences and a Research Fellow in the School of Geographical and Earth Sciences at the University of Glasgow. He describes his background as “classic marine ecology,” and says that he uses “biological techniques to answer geological questions and geological techniques to answer biological questions.” He is interested in global change “from the perspective of marine calcifiers,” as well as algae and coral, and the synergy between natural and anthropogenic change, using marine organisms as a proxy for climate change, with an emphasis on temperature, salinity and acidification, particularly in the North Atlantic.

Dr Natalie Hicks is a Post-Doctoral Research Associate in the Effects of Ocean Acidification on Benthic Biogeochemistry at SAMS, where she has worked for three years.  Her research focuses on the effects of environmental change (including acidification and temperature) on marine benthic systems, with an emphasis on sediments and nutrient cycling. Her PhD (at the University of St Andrews) focused on “determining the effects of elevated CO2 and temperature on benthic primary production under different macrofaunal diversity levels.” Natalie says she is “excited” by mud and the complex effects of climate change on different organisms and the ecosystem, and is also interested in how ecologists and biogeochemists work together.

Dr Heidi Burdett is a MASTS Research Fellow based in the Department of Earth & Environmental Sciences at the University of St Andrews. A biogeochemist, she is currently doing research into sulphur gases (dimethylsulphide) and benthic habitats, particularly the carbon storage potential of coral and algae, as well as kelp forests and sea grass meadows, with an emphasis on “the link between ecosystem function and biogeochemical cycling in estuarine, coastal and marine environments, in response to both natural variability and projected changes in climate (e.g. ocean acidification and global warming).” 

Professor David Paterson, of the Scottish Oceans Institute, School of Biology at the University of St Andrews, is the Executive Director of MASTS (the Marine Alliance for Science and Technology for Scotland). He has always been interested in “how biology and physics interact,” and how organisms respond to the environment – and how they adapt and evolve. His work encompass the study of how biodiversity contributes towards ecosystem function and the provision  of ecosystem services under different scenarios of climate change. Paterson’s career has spanned a range of different attitudes to climate change in scientific circles, and he recalls how, in the early 1990s, his colleagues advised him not to mention the subject in a grant application because it was regarded as already “old hat.”

Maerl under threat from acidification?

By Nick Kamenos

Scotland’s seas are home to a pink, plant-like organism called maerl, or coralline algae, that lays down a hard skeleton similar to corals. Each individual is the size of a tennis ball and many individuals are often found together in beds. Maerl beds form an important three-dimensional habitat on the sea floor, comparable to sea-grass beds in terms of their biodiversity. In addition to their role in maintaining high biodiversity, they are important in ecosystem service provision (e.g. acting as a nursery area for juvenile species) and play a large role in cycling and sequestering carbon at geological time scales. Indeed, some of the Scottish maerl beds may have been growing since the end of the last Ice Age, around 8,000 years ago. Whilst their hard skeleton allows them to perform important biogeochemical functions, it is also their Achilles heel – they only grow at a quarter of a millimetre per year and this makes them very sensitive to physical damage. There is uncertainty regarding how maerl beds will fare in warmer, more acidic waters; a key threat being ocean acidification, which may reduce the strength of their skeleton and lead to a breakdown in their three-dimensional structure. This could have devastating impacts on the services maerl beds provide, because any such damage would take centuries to regrow. Research is progressing to understand the sensitivity of these important systems to climate change.

 

Making sense of the smell of the sea

by Heidi Burdett

Many of us know about the ‘greenhouse effect,’ which is being strengthened by increased emissions of greenhouse gases from human activities. However, there are other gases in the atmosphere, loosely referred to as ‘anti-greenhouse gases,’ which are involved in climate-regulation feedback systems and act as natural atmospheric thermostats. One of these gases
is dimethylsulphide (DMS), and anyone who has been to the seaside will have breathed it in at some point, because it is one of the gases that make up the ‘smell of the sea’. 

DMS originates from sulphur compounds produced by most algae in the oceans, from coastal seaweeds to tiny single-celled algae called phytoplankton that float in the surface waters of the open ocean. Once in the atmosphere, the gas is oxidised into ‘cloud condensation nuclei’ – tiny sulphate particles that allow water droplets to cluster together. This promotes the formation and growth of clouds, limiting the amount of solar radiation reaching the Earth’s surface. It is suggested that, as algal growth increases, DMS emissions and thus cloud cover increase, reducing surface temperatures. This in turn reduces algal growth, subsequent DMS emissions and cloud formation decline, increasing the temperature again, and so the cycle continues.

Feedback mechanisms such as this are composed of complex biological, chemical, physical and geological interactions that are sometimes not well understood. However, given their potential importance in regulating climate, climate scientists are now trying to understand how these processes will change in the future, as atmospheric CO2 continues to increase. 

Clear as mud

by Natalie Hicks

At first glance, a mudflat (Figure1) may not appear to be as charismatic or important as a coral reef, but you don’t need to dig very deep to discover why these fine sediment habitats are so interesting. Marine sediments (sand and mud) cover a huge proportion of the sea bed, from deep sea to coastal regions, and provide a variety of important services, such as carbon sequestration and nutrient cycling.

Coastal mudflats and subtidal deposits thrive with varied communities of – often invisible – plant and animal life. These habitats cover vast areas and may seem uninhabited, since the organisms that live there are often small or buried and thus can’t be seen with the naked eye. Where the deposits are shallow enough for light to reach the surface of the bed, there is energy for photosynthesis and there may be sea grasses growing or, more often, communities of microscopic algae.

These are single celled organisms (Figure 2), usually dominated by a group known as diatoms. Despite their small size, these microalgae can spread across large areas and contribute a significant proportion of the carbon and oxygen cycling. They provide food for other organisms, and even influence sediment erosion due to secretion of an organic material that acts like glue, protecting the bed against erosion.

 

Also living on top of and within the mud are many invertebrates (Figure 3) that feed on the microalgae. The movement of these burrowing organisms through the sediment stimulates the penetration and recycling of oxygen, carbon and nutrients. The rich diversity of invertebrates also attracts predators, such as fish and, in intertidal regions, large native and migrant wading bird populations.


Climate change pressures, such as increasing temperature, rising sea levels and elevated CO2, are likely to cause changes to these muddy habitats, and affect the behaviour and occurrence of the organisms that live within them. As the ‘meeting zone’ of the atmospheric, terrestrial and marine systems, these habitats are also under extensive pressure from human activity. Scientists investigating the ecology of these habitats often spend long days sampling and taking measurements, and have learnt to work quickly enough to beat the incoming tide (Figure 4). Knowledge gained through this research will be invaluable in deciding how best to manage these habitats under future environmental change.


Next time you pass an expanse of intertidal mud, take a second glance and see if you can spot any signs of this secret diversity – brownish or greenish patches indicate the presence of the microalgae, and small ‘hills’ or dents in the sediment surface are often the burrows of the invertebrates, in their 'secret' but important kingdom.

 

 

"Time for action?". Science Scotland (Issue Fifteen)
Printed from http://www.sciencescotland.org/feature.php?id=221 on 26/06/17 02:44:41 PM

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