In 2006, NIWA’s deep-sea research vessel Tangaroa was used to explore the Hikurangi Margin for cold-seep sites. Communities of organisms at the sites were monitored by video and specimen samples taken for identification and analysis. Dr Ashley Rowden, from NIWA, summarises the research expedition.
DR ASHLEY ROWDEN
In 2006, we took NIWA’s research vessel Tangaroa to the Hikurangi Margin to explore for seep communities.
Whilst we’d had some evidence that there were seep communities off our shores, no one had actually taken a sample of a live seep organism nor imaged what seep communities looked like off New Zealand. So we took part in an international programme called RENEWZ, which involved institutes from New Zealand and a number of participants from around the world. And we were funded by a programme which was funding international efforts to explore for new habitats, new communities, and we were also part of a project called Census of Marine Life, the ChEss programme, which was looking at chemosynthetic communities in particular. So we went out to potential target areas, and we used a variety of techniques then to try and locate these seep communities.
It’s not a straightforward task to go and find seep communities, which is why we didn’t actually manage it until 2006. So you need obviously a fairly large research vessel well equipped, a whole range of people and all of their sorts of skills.
We used a technique which we sort of standardised as we went on through the voyage and that was we first of all go to where we think a seep is based upon geological information, and then we used two types of echo-sounder which the vessel has to first of all map out the seafloor topography – the lumps and bumps if you like that are on the seafloor – but also the echo-sounder gives us some information about how hard or soft the seafloor is as well. So that should give you a signal which might relate for instance to those calcium carbonate structures on the seafloor, so you might see those little reef features standing out against the soft sediment. And then we used another type of echo-sounder, a single beam echo-sounder which looks at the water column, so it gives us a signal back from the water column. And on those images what we’re trying to find is a bubble flare, so the bubbles, the methane actually exuding from the seafloor. So if we put those two bits of information together and if those two things coincide, then we think, right, that’s going to be a pretty good seep site.
So then we follow up with a camera, and we tow it behind the vessel, and we run a series of transects, often centred on that flare or those lumps and bumps on the seafloor. And we keep running those transects for a few hours and then we bring the camera back on board and then we look at the video and hopefully what we’ll see in the video is evidence of the seep, and that’s what we’re looking for in terms of the tubeworms and the mussels and the clams, so the most obvious of the fauna. So once we’ve seen that, perhaps also some bacteria mats, then we can say, right, we’ve definitely got our seep community now. What we now want to do is collect some samples from there.
National Institute of Water and Atmospheric Research (NIWA)
Census of Marine Life Programme
ChEss, Census of Marine Life Programme
Jens Greinert et al., 2010;
Marine Geology; doi:10.1016/j.margeo.2010.01.017