Citizen science is pretty cool. As a participant you can learn new things, explore new places and ideas, and have fun! It can even make a valued contribution to science – which is exactly what trained recreational scuba divers participating in the global project Reef Life Survey did for a new paper published in ‘Nature’ just a few days ago. These citizen scientists have been a busy bunch, undertaking some 4,357 transects at 1,844 sites. These divers weren’t just found in those nice warm tropical waters either, spreading out to 74 of the world’s marine ecoregions*, finding some 2, 473 species of fish. This very wide-ranging data – all collected in the same manner – has thrown up something interesting. Sure coral reefs have really high fish species richness – a raw count of the number of different species (actually as far as we know the most species rich of all marine habitats), but does that mean that coral reefs are the most diverse system?
Perhaps not. Rick Stuart-Smith of the University of Tasmania's Institute for Marine and Antarctic Studies in Australia and a team of international scientists have taken a new tack in measuring diversity. As well as species richness, and evenness (the distribution of individuals in a species), they have also calculated functional diversity, which is based on a species functional position in the ecosystem they are found. These traits include their trophic group, what periods of the day/night they are most active, and what their preferred substrate is. As one of the authors Jon Lefcheck of the Virginia Institute of Marine Sciences in the USA notes in the University press release “by gathering information on the animal's traits - what they eat, how they move, where they live -- we can understand more about how dissimilar they are. Dissimilarity is the essence of diversity".
This functional diversity showed some very different global patterns to richness. Instead of highlighting those nice warm tropical areas, the work pointed to nutrient rich temperate regions as being the most diverse. Perhaps more importantly, functional diversity wasn’t necessarily correlated to species richness or evenness. For example, temperate region hotspots tended to have higher functional diversity and evenness relative to richness than the tropics.
Here’s the “so what” factor. When we are looking at protecting the marine environment, we tend to use richness as a way of selecting areas in most need of protection. These areas may have many species that can perform the same role, so if you lose one species of fish another may step in its place and the ecosystem will function. But if you have only a few species – or even just one that can perform a particular functional role and that species is lost, then the impact on the ecosystem can be much more significant. What managers need to do to ensure the long-term persistence of vulnerable marine ecosystems, argue the researchers, is to take into account functional diversity when prioritizing areas for protection.
The original paper is published in the journal ‘Nature’, and is only accessible by subscription or paying for the article. The direct link to the publication is http://dx.doi.org/10.1038/nature12529
* Ecoregions are defined as: “Areas of relatively homogeneous species composition, clearly distinct from adjacent systems. The species composition is likely to be determined by the predominance of a small number of ecosystems and/or a distinct suite of oceanographic or topographic features. The dominant biogeographic forcing agents defining the ecoregions vary from location to location but may include isolation, upwelling, nutrient inputs, freshwater influx, temperature regimes, ice regimes, exposure, sediments, currents, and bathymetric or coastal complexity” (Spalding, et a., 2007). If you want to learn a little more about the marine ecoregions used (and where this definition came from), have a look at this paper – made open access courtesy of The Nature Conservancy.
Image: Taken in the Mediterranean Sea near Marseilles at 40m deep near the wreck of a Messerschmitt aircraft. Credit Arnaud Abadie/Flickr (CC BY 2.0)