NIWA's Dr Ashley Rowden describes how the data from the echo-sounders and the video camera images are overlaid. The net result gives a habitat map of the site. In 2006, eight seep sites were studied in detail, and a follow-up voyage in 2007 discovered more. At least 20–30 seep sites exist, each with a community of organisms.
DR ASHLEY ROWDEN
So as well as arriving at descriptions of the communities from what species they’re composed of, we also try to understand how they’re spatially distributed. So what we do is we take the information that we got from those echo-sounders about the seafloor topography and also the hardness and softness of the substrate, and then we overlay on that information the information we get back from the video from the camera – so the distribution of the various organisms along the video track overlaid onto that lumps and bumps and the soft sediment and the hard sediment. So then we begin to understand what the relationship between particular sorts of animals is to their environment, whether they are always associated with a hard substrate or always associated with soft substrate, or are they at the centre of the seep site or are they at the periphery of the seep site.
In 2006, we studied eight seep sites in detail, but we discovered a few others. And in follow-up voyages in 2007, they went to some of those ones which we weren’t able to visit and they also found more. And so now our understanding is that at least 20–30 seep sites which have seep communities which is quite a large number for a relatively small area, and those seeps vary in size from being quite small in some instances, maybe the size of a large room, to 70 000 square metres which is like eight rugby pitches, so very large, and in fact, that one is deemed to be the largest known seep in the world.
So typically at cold seeps, the organisms which dominate the cold-seep community are abundant but the organisms are generally not very diverse, so the number of species is relatively few. And so that’s what we’ve also found at the New Zealand seeps. So there are a few species like the tubeworms and the clams which are in quite high abundance.
We still though need to confirm the identity of these species. We have certainly a good indication of what we think they are, but we still need to carry on with some genetic studies to fully determine whether they’re different from species which are found elsewhere. Indications so far are that some species are found elsewhere, but we also got a few species in there which we’ve only known to be at New Zealand seeps, so they’re endemic to New Zealand seeps which makes them, the seep community at New Zealand, quite distinct.
National Institute of Water and Atmospheric Research (NIWA)
Dr Dave Bowden