Invisible forests; and how marine dwelling microorganisms really rule the waves!

By Charlie Whittaker

For sure, the abundance of terrestrial plants we share our planet with are weird and wonderful in equal measure, but why should they get all the glory when there’s an equally as important component to the biomass on Earth? I’m of course talking about the much maligned, often overlooked, and most definitely misunderstood microscopic creatures that inhabit the murky depths of our oceans!

The marine environment is by far the planet’s largest habitat. Covering over 70% of the land area, it contains a huge diversity of organisms, co-existing in a harmonious, yet fragile, balance. Underpinning all the life that the oceans sustain are photosynthetic organisms. Tiny, often microscopic and unicellular, these organisms are responsible for roughly half of all the primary productivity of the planet. Their ability to capture sunlight and use it to synthesise new organic compounds provides the energy for the diversity of marine life found in the ocean. They are, for want of a better analogy, the oceans’ invisible forest.

Diatom2

These primary producers are exceptionally diverse, ranging from tiny photosynthetic bacteria that hitch a ride on the tiny particulate matter found in seawater, to the phytoplankton. These represent a hugely diverse group of unicellular organisms. Contained within this group are the diatoms, which enclose their cell in a glass box made out of silica, as well as the dinoflagellates, that tend to employ semi-opaque plates of cellulose to separate themselves from the external environment. And then who could forget the coccolithophores? Unicellular like their other phytoplankton counterparts, these microorganisms cover themselves with ornamented plates called coccoliths made out of calcium carbonate.

So why does any of this matter?

80 million tonnes of marine seafood are caught globally each year. Seafood forms a common constituent of diets worldwide and provides more than 1.5 billion people with at least 15% of their protein requirements. The entirety of this marine life, whether directly (animals that feed on the producers themselves) or indirectly (in the case of organisms several trophic levels above the primary producers), relies upon the productivity and photosynthesis these organisms are carrying out.

They also represent an important carbon sink. The ocean plays a huge role in mopping up and buffering CO2 released into the atmosphere: and a significant proportion of the ability to do this stems from the simply huge amount of photosynthetically capable biomass present.

Okay, that’s fine and dandy then?

Not quite. Unfortunately things are getting progressively less peachy. Climate change poses a serious issue to the future productivity of the oceans and marine life. Changes to the oceanic average temperature has implications ranging from alterations to the vertical stratification of the water column (important in mixing, thereby ensuring all the phytoplankton receive all the nutrients they need) to impacting the chemical reactions responsible for the productivity of the primary producers. Whilst of course, the response to rising sea temperatures will not be the same globally (a paper recently published in nature showed that “Some phytoplankton like it hot” and that warming oceans may increase productivity in some areas) there are important marine areas of human concern that are set to suffer substantially: the Atlantic Cod population has plummeted in number in recent years. Partly this has been driven by overfishing, but it was also shown this was due to rising temperatures. The alteration modified and impacted the plankton ecosystem in such a way that it reduced the survival rates of young cod, and thereby facilitated the population’s rapid decline.

They may be invisible, but the effects of these tiny photosynthetic powerhouses are quite the opposite. And unless something is done soon, they may be at the forefront of drastic alterations to our current marine system.

Further reading:

On the effect of increased temperatures on cod and phytoplankton populations.

On the propensity some phytoplankton show for warmer temperatures.

Marine Biology: A Very Short Introduction.

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Trees: Carbon Sinks or Sources?

by Joanna Wolstenholme

With a warming planet, you wouldn’t be laughed at for thinking that trees may come to our rescue: we release more CO2, the greenhouse effect leads to global warming, and this increase in temperature leads to plants being able to photosynthesise faster. Indeed, future climate warming is expected by many experts to increase plant growth in temperate ecosystems, and increase carbon sequestration. So is our planet coming to the rescue, is Gaia saving us from certain doom? Well, unfortunately, no. Heatwaves lead to droughts, and droughts put plants, trees in particular, under a lot of stress. Without sufficient water, plants struggle to transpire, and so are unable to take up enough nutrients and water for growth.

Amazon_Manaus_forest

Ciais et al (2005) found that during the heatwave and drought of 2003, plants in Europe managed to undo four years of their own carbon sequestration, by reverting to sources rather than sinks of carbon. Growth primary production was severely reduced, and respiration in plants and soil microbes fell dramatically. They suggested that increased extremes of temperature, as have been predicted if we fail to reign-in climate change, may counteract the effects of the mean warming and lengthened growing season.

This work was put into stark contrast by the 2005 and 2010 droughts in the Amazon. Usually, the Amazon acts as a vast carbon sink, absorbing 25% of atmospheric carbon, making it an important buffer against climate change. However, increased occurrence of droughts could lead to it becoming a net carbon source – a catastrophic positive feedback system which would cause a vast acceleration of climate change. The 2005 drought led to the release of approximately 1.6 billion tonnes of carbon to the atmosphere, and as much as 2.2 billion tonnes of carbon could have been released from the Amazon during 2010. That is about one-quarter of global emissions from fossil fuel use. The Amazon is such a vast forest (25 times the area of the UK, to put it into perspective) that even low level drought damage can have a large overall effect, and this is likely to be impounded in the coming years by more frequent drought stresses, even at a low level.

400px-DroughtNonetheless, fear not – a report published last year by University of Exeter and Colorado State University cast a more positive slant on the situation. They believed that previous models had failed to take into account the amount of water that the forest itself is able to recycle during droughts. As moisture cycling is normally a source of a third of the water rainforest plants use, it has the potential to act as a buffer during times of drought. However, moisture cycling is severely impacted in disturbed forest, so in order for the Amazon to still withstand periods of drought, forest conservation measures must be strongly enforced.

Lets hope the academics from Exeter and Colorado are right, and that the Brazilian government are able to protect their amazing forest. In the mean time, do your own little bit – plant a tree!

For more information, see: 

Ciais et al, 2005. ‘Europe-wide reduction in primary productivity caused by the heat and drought in 2003’. Nature 437 doi:10.1038/nature03972

Planet: Why Plants Matter

by Toby McMaster
 

As a world we currently face many major problems, to which we have yet to find specific solutions. The answers to many of these lie, at least partially, in plants. The first land plants appeared roughly 450 million years ago, primates around 80 million years ago and the first Homo sapiens only about 450,000 years ago. In short, for every year humans have inhabited planet Earth, land plants have inhabited it for a millenium. In fact, it seems likely that however hard we try to ruin our planet for ourselves, some vegetation will still outlive us. In the history book of plants, humans may yet just appear as a brief speck – a self-destructive species that got too big for its evolutionary boots and brought entire ecosystems tumbling down with it. Plants are here to stay – so why not use them to try and ensure that we are too? In this first blog entry we will explore the various ways in which plants can help us overcome the issues facing humankind.

Climate Change

AttributedEarthWith the recent IPCC report on climate change delivering a figure of 95% certainty that humans are causing the current rise in global temperature, it is surely necessary to act to mitigate the situation, even if only as a precaution. Given that 15% of atmospheric CO2passes through plants each year, they are certain to play a role if we are to keep global warming to a minimum. We desperately need a better understanding of the likely worldwide effects of climate change on plant life and to try to work out what we can do to minimise any damage such changes will cause.

Starvation and Malnutrition

According to the World Health Organisation, 842 million people in the world do not have enough to eat. 827 million of these people live in developing countries. The UN predicts that by 2050 the world population will reach 9.6 billion. Moreover that of developed regions is forecast to remain largely unchanged at around 1.3 billion from now until then while the 49 least developed countries are expected to double in size from around 900 million people in 2013 to 1.8 billion in 2050. This will lead to widespread hunger we can’t understand on a scale we can’t understand. These are an intimidating set of circumstances but as a planet we can rise to the challenge. To do this will require improving both crop yields and food distribution, and reducing waste. The fact is that as a massive proportion of the Earth’s ecological base plants represent the most efficient way to feed more people faster. To utilise them we need to explore all the techniques available to us, GM is undoubtedly one of these but is far from a magic bullet, we also need to put as many resources as we can into understanding how to optimise agriculture.

Biodiversity

BDWe are currently in the middle of the 6th mass extinction event in the history of our planet, and the first since 65 million years ago when the dinosaurs were wiped from the face of the Earth. Species are going extinct at somewhere between 100 and 1000 times the expected background rate. It is arguably unethical for our one species to have eliminated so many others, but in one sense extinction is a natural process we have merely accelerated through habitat destruction and climate change. The real issue is that we are reliant on so many species which are in danger of extinction and that we are rapidly losing the opportunities, including novel medicines, offered by so many more.

The approach taken in the past has often been based on the naïve human view that we can just hang on to the species we are interested in and let the remainder of the natural world disappear into oblivion. This is misguided for two main reasons: firstly, our knowledge of the natural world is nowhere near sufficient to rule out species as useless to us, and secondly, species do not exist in isolation but rather as complex ecosytems to be viewed as cohesive units. Plants will represent a massive part of future attempts at restorative ecology – trying to rebuild damaged ecosystems. They must also be carefully protected in the functional ecosystems we still have, as they are so often the foundation stone on which the rest of the community is built.

Medicines

AttributedMedicineIn an age where we have complex techniques such as X-ray crystallography to help probe molecular structures, we might like to think we are beyond simply taking compounds plants have already made for us, and using these chemicals to treat disease. Nothing could be further from the truth. According to the American Association for the Advancement of Science (AAAS) in the year 2000 around 25 percent of prescription drugs dispensed in the United States contain plant extracts or active ingredients derived from plants, and more than 60 percent of cancer drugs on the market were based at least in part on natural products. These are, admittedly, not incredibly recent statistics, but the timescale over which new drug discovery and production takes place means they are likely still approximately accurate. There are still countless conditions and diseases for which we have no or poor treatments, and plants will have a massive role to play in helping fight these ailments.

As demonstrated by the last two examples in particular, these problems are not isolated from each other. Plummeting biodiversity is cutting down our supply of potential new medicines, medicines which we will need to help treat a booming population in developing nations where mortality rates from infectious disease rates are highest. Any new drugs will likely be incredibly expensive to begin with, a problem which may be compounded by the economic impact of climate change on developing countries.

This is only a short list of the problems we face and plants may well not hold the solution to all of them, but they are an incredible natural resource which we should make use of. This blog is dedicated to discussing the ways in which we can do this, and to generating enthusiasm for plant science research.