Day 9: 4th June 2006

Day 9: 4th June 2006

Having completed all of the camera transects for the Graveyard seamount complex our full attention has now turned to sample collection. Whilst most of our work is non-destructive, it is essential to collect some samples so that we can compare what we see in the photographs to what animals are down there, as well as collect animals that the camera cannot image, such as those that live hidden on other organisms or substrates.

On this trip we have been collecting samples using an epibenthic sled (see pictures above). This is a 1m wide sled that contains a net (this has a mesh size of 25mm, with an outer net to prevent chaffing/damage to the smaller one) so that it can scoop up and collect samples as it skims along the seafloor. The crew of the Tangaroa organize the often complicated logistics of lowering the sled down to depths of around 1000m - taking into account the weather conditions, ship speed etc to ensure that the sled arrives at the designated 'start' position of the tow. The sled is towed for approximately 15 minutes, generally covering a distance of 0.25 – 0.3 nautical miles (in a down slope direction), at a speed of 1 – 1.5 knots. It is then pulled back to the surface and the samples emptied out on deck (see photo below, left) to be sorted by the scientists.

The sorting process starts by picking through the sample - looking for anything that's alive. A lot of what has been collected so far on the Graveyard seamounts is 'coral rubble' (see photo above, right) with animals living in amongst this substrate. The coral rubble can be a consequence of damage by trawling but can also be a natural phenomenon. The sorted animals (see photo below, left) are then categorized into groups and stored so that the taxonomic team back on shore can identify them. The taxonomy team will create an entire inventory of what has been found during this voyage – including the common species as well as any 'new'/rare ones. The time it takes to sort through a sample can vary considerably depending on how much the sled collects and how many animals are there, and on a busy day the team can spend a full shift sorting samples in all weather conditions - as the photo below (right) shows.