Wednesday 13th February

By breakfast time this morning Isis was back in action, thanks to the efforts of the ROV team overnight, and dive 201 was ready for launch. The objectives of this dive were to continue the wider geological survey of the slopes of Mount Dent, and collect sediment samples for geochemical analysis. Throughout the day the vehicle has been tracing a path among craggy outcrops on the seafloor, picking up rocks under the direction of the geology team to piece together the workings and history of the deep-sea vents here.

Geo team examining samples from an earlier dive (photo: Adrian Glover)

During today's dive we found a beer bottle on the seafloor, one of a few pieces of rubbish that we have seen so far. Human-generated rubbish unfortunately has a long history in the deep ocean: in the age of steamships, for example, ships would dump "clinker" (the remains of burned coal from their engine rooms) during their journeys, which changed the nature of the seafloor along well-travelled routes. At that time, however, we only had hazy notions about the depth of the oceans, let alone what was going on down there.

Today, plastic has replaced clinker as a common contaminant of the deep ocean, and we plan to collect sediment cores here that will be analysed to see if they contain microplastics - tiny ground-down remanants of plastic that may now be quite ubiquitous in the oceans.

Although we might not think about it much, our daily lives have an impact on the deep ocean, not just through items of litter that end up there, but increasingly through the resources that we use. But for the first time in the history of our species, we are in a position to explore and investigate the ocean floor to understand what our impact is likely to be, so that we can make more informed choices for the future.

While the geologists and geochemists have been surveying the seafloor today, we have had time to refine plans for the next phase of our expedition, during which we will take a break from ROV dives to survey the hydrography of this part of the Cayman Trough. That task should help us to understand the source and currents of the deep ocean water that bathes the vents here and potentially connects their colonies of creatures with the wider world.

Isis heads out for another dive (photo: Adrian Glover)

But first we have one more dive scheduled at the Von Damm Vent Field tomorrow, to collect instruments that have been recording data during our visit so far, and to deploy experiments and instruments that will be collected by a Japanese expedition here in June/July.

February 2013