Thursday 12 August 2010

You can only love what you know

It’s August, the holiday season, when many of us will be taking trips to the coast and spending time next to the oceans. Many of us will even go “rockpooling” or fishing with a small net. The oceans are a source of fascination for many of us, harbouring strange and colourful animals. I am amazed at how early this fascination can begin. My two daughters, aged 3, now regularly demand to look at the “shark book” or the “fish book” and both will sit either side of me and identify “hammerhead shark” “leopard shark” or “blue shark”. They are particularly fascinated by the shark’s large teeth and that sharks are a bit scary and might eat you, which of course happens very rarely (even more rarely nowadays that we have decimated many shark populations). Their capacity to absorb information is a constant source of surprise to me. They are also identifying eels, stingrays, corals, sea anemones and sea horses. Of course, it helps when your dad is a marine biologist.

Several things occur to me when the girls are displaying proto-marine biologist behaviour. The first is what will the oceans look like when they are my age or older. Unfortunately, at the present rate of degradation, the oceans will be a poor place even compared to today. Many corals reefs will be gone completely. Those remaining will be under severe stress and probably a mix of coral and algal species, a shadow of the reefs my wife and I dived on when I was younger. Wild-caught fish will be a rare and expensive luxury. Many more stocks will be gone with some projections suggesting that all the major fish stocks targeted today will have collapsed by 2050. Dead zones will have spread, as will the toxic red tides that poison everything they come into contact with. It’s a pretty depressing picture and it is the future generations that will suffer from our carelessness.

The other thing that occurs to me is that young children have an innate fascination with the natural world. I guess mine are very lucky in that they are privileged to live in a comfortable house, they have plenty to eat and have parents that are interested in their welfare. This fascination is stimulated by the fact that mum and dad will answer all their questions on what animals they see and so on and they will take an active interest in what they are looking at and doing (snails are particularly popular, being examined for many minutes while they come out of their shells, as are butterflies, which are pursued around the garden, and froglets). It is great that such young people are so interested in the world they live in, which begs a further question. Why is it that so many people seem to lose interest in the world they live in when they get older? This of course is not a simple question. Life for many of us is fast-paced and stressful. Getting a few minutes to consider our place in the world and how to live in it is difficult. We’re bombarded by a huge advertising (brain-washing) machine to attempt to attain a lifestyle lived by the “rich and famous”. This happens to such an extent that many of us will buy luxuries that we cannot afford even to the detriment of basic requirements for life, such as nutritious food. Amazing.

There are many people (I am no exception), organisations, and even the governments calling for changes in our lifestyles, to live a life of lower consumption of resources, and pointing to various aspects of the degradation and destruction of the natural world. Many people now simply switch off when the next environmental doom story is put before them in the media. This is because these events do not affecting them directly but moreover, I am convinced in many cases it is because they have ceased caring. Perhaps we are targeting the wrong people or more correctly the wrong generation of people. Education about the importance of the Earth in supporting life, including human life, and the role which plants, animals and ecosystems have in maintaining the Earth system must begin at the earliest age. Only then will people grow up with enough passion about the environment that they actually care about the way in which they live. As the saying goes, you can only love and care for what you know about. It was how I got interested in the oceans. Spending hours on a small beach in Ireland and time out fishing with my grandfather and uncles and even, dare I say it, sitting in front of the TV with interested parents watching the “World About Us”, “Jaques Cousteau” and “Life on Earth”.


Evidence of the decline of ocean surface phytoplankton since the turn of the century

5th August 2010

You may have seen the press coverage of the paper by Boyce and colleagues (Nature 466: 591-596). The paper relates a clever study where scientists have examined chlorophyll data obtained through various methods, including very primitive ways of assessing the transparency of the sea, to figure out how levels of primary production have changed since 1899. For those of you who find that confusing let me explain. On land, the primary producers are the plants that we are all familiar with, grass, trees, shrubs and so on. These plants use the sun’s energy to trap (fix) carbon from atmospheric carbon dioxide and they use this to synthesise organic molecules (photosynthesis). These form the basis of the energy that drives life and the molecules that form structures, enzymes and so on. Animals graze plants and this energy and material is used by them to grow, and these animals in turn are eaten by other animals (predators) and so on, forming successive layers or trophic levels of food chains, many of which go to form foodwebs. In the oceans, carbon is fixed through the same process of photosynthesis but in this case most of the work is done by tiny cells, phytoplankton, that live in the surface layers of the ocean (upper 150m depth). The phytoplankton are grazed by zooplankton, tiny animals that also live in the surface layers of the ocean, and these in turn are preyed on by larger animals, including fish and so on up to the large marine predators we are familiar with such as sharks and tuna. Some very large animals also graze on zooplankton, such as baleen whales short-circuiting lengthy food chains which lose a lot of the energy of primary production at each step.

Whilst people are familiar with the process of photosynthesis on land, and they are aware that plants can be used as food (cereals like wheat etc), they may not be aware that about half of the production on Earth takes place in the oceans. We do not directly consume phytoplankton but we do eat fish, that ultimately live off the phytoplankton, and which feed many millions of people and provide a livelihood for many others. However, photosynthesis also has other critical effects that are important to maintaining the balance of the Earth’s life support system. These include the production of oxygen, a by-product of photosynthesis, and the draw-down of CO2 from the atmosphere into the deep ocean. It is the latter that has meant that the oceans have taken up nearly half of humankind’s CO2 emissions. The oceans are providing us with food, with the air we breathe and they clean up the atmosphere through the process of photosynthetic primary production.

The paper by Boyce and colleagues (2010) demonstrates that the concentrations of phytoplankton in the surface layers of the ocean have declined in 8 out of 10 of the major ocean regions of the world. This is occurring mainly through an effect of global warming. When the surface layers of the ocean are heated up they have a lower tendency to mix with the cooler deeper layers, a process called stratification (layering) of the surface of the oceans. The phytoplankton only live in the surface waters because they require sunlight to photosynthesise and therefore to live. However, they also require nutrients other than carbon to synthesise organic molecules, particularly nitrogen and phosphorus but also other nutrients such as sulphur and iron. As the phytoplankton grow in surface water layers they use up these nutrients and their growth becomes limited. The phytoplankton cells undergo a form of starvation. Tropical oceans are naturally stratified, whilst in temperate seas stratification occurs during the summer but storms during the winter mix up the surface layers of the oceans with deeper, nutrient rich water, annually replenishing the nutrients phytoplankton need to grow. Global warming has increased the level of stratification throughout the oceans and thus has caused a decrease in global primary production by phytoplankton through reducing the supply of nutrients from deep water to the oceans surface.

The simple fact is that almost all life in the oceans, with the exception of chemosynthetic communities that are based on chemical energy, depend on surface production by phytoplankton. Even the deepest living organisms live off the rain of dead cells and occasional carcasses descending from the surface layers of the ocean. Much of this material arrives in the deep sea in the form of marine snow, aggregates of dead phytoplankton cells, cast off skins of zooplankton, faecal material etc. The reduction in surface primary production will have impacted almost other marine life in the oceans, even reducing the production of the fish that we eat. That this has been happening for so long is disturbing. It seems that even by the turn of the twentieth century production was declining as a result of industrial activity, a long time before we became aware of climate change.