Cruise News

Today it’s my turn to say a bit about myself and why I’m here on board the Discovery. Actually this is a question I’ve asked myself a few times, considering I’m one of the few people here with pretty much no experience in marine biology or oceanography, and who has never been to sea before; finding myself aboard a research vessel in some of the remotest waters of the world is not something I ever expected. By training I’m a molecular biologist (meaning that I work with DNA), with a particular interest in applying DNA-based techniques to studying the biodiversity of small and obscure animals. My PhD was on nematode worms in agricultural soil, for which my fieldwork never took me further than 60 miles from Edinburgh.

Then, as I was finishing my thesis, the British Antarctic Survey and the Natural History Museum were beginning a collaborative project to study the nematodes living in deep-ocean mud. I was employed as a postdoc at BAS, and that, to cut a long story short, led me here to collect samples, along with Margaret Packer and Adrian Glover from the NHM, who are involved in the same project.

An unidentified nematode from one of our samples (photo courtesy of Adrian)

So why are we interested in nematode worms? Well, they may be small (around 1mm long on average), but they have strength in numbers. A typical square metre of topsoil may contain a million individuals. Similar numbers seem to exist in marine sediments (though far less is known about distributions there), and when one considers that seven tenths of the Earth’s surface is covered by water, and much of the remainder by soil, it becomes clear that nematodes must account for a substantial fraction of all animals on the planet.

In variety of species, too, they surpass all other animal groups (with the possible exception of insects) – though all nematodes share the same basic body plan, they have evolved into a wide range of forms, filling many different ecological niches. There are around 12,000 described nematode species, but this is undoubtedly an underestimate of the real number, since every survey of a new environment unveils a multitude of new ones; the true total is likely to run into the millions.

Why does this matter? If there’s a common thread that ties together all of the disparate research activities we’re doing on this voyage, it’s understanding natural ecosystems, the varieties of life which make them up, the cycle and flow of nutrients and energy from one level to another. Given the rate at which human activity is altering natural processes, we consider it important to understand these systems, given that we all depend on them for our survival. What we know about nematodes, put simply, is that there are a lot of them, they eat a lot of different things, and a lot of different things eat them.

This makes them a significant component of ecosystem function, one about which relatively little is known compared with other groups. Therefore we wish to know more; however, those numbers I mentioned earlier should give some idea of just how difficult it is in practice to build a realistic picture of how many species exist and how they are distributed. The problem is exacerbated by the fact that nematode taxonomy - the identification of individuals to species by examining their physical features down a microscope - is extremely difficult and laborious.

Adrian and Margaret slicing a core into horizontal sections

Hence, DNA barcoding, which is my particular specialist subject. Rather than identifying an animal by its morphology, it is possible to read a particular segment of its genome, then, by comparing many such segments from different individuals, to use that information to tell us how many types are present; this is potentially far more rapid than traditional taxonomy (though the DNA approach has pitfalls of its own, but that’s another story). The hope is that this will enable us for the first time to generate some broad-scale data on nematode biodiversity, especially in environments such as the deep ocean where they have seldom been studied before, and to begin to answer some of those basic evolutionary and ecological questions.

So that in essence is why I’m here, braving the cold and the waves, sifting through mud from 4000 metres below, and trying to do molecular biology in a lab which is constantly rolling from side to side. Of course, the main part of the DNA work will be done back on land; Margaret and I are really only collecting and preserving the animals while we’re on ship. I’ve been learning some microbiology as well – when I haven’t had any nematode material to work with (that megacorer is a temperamental thing), I’ve been assisting my BAS colleagues David Pearce and Rachel Malinowska with their work on seafloor bacteria. All in all, I may have found myself somewhere I never expected to be, but I wouldn’t be anywhere else.

Me, on deck