Blog - specimens collected by epibenthic sled - 10 March

10 March 2018To verify the identities of animals we see on the DTIS camera, we use an epibenthic sled to collect physical samples of animals from the seafloor.

10 March 2018

To verify the identities of animals we see on the DTIS camera, we use an epibenthic sled to collect physical samples of animals from the seafloor.

A brittle star, Ophiura sp., shown in dorsal and ventral view collected from Iselin bank. 

Our sites for sledding are chosen from what we see on the video and still images so that we minimise impact on the fauna but still get a representative selection of creatures from the catch. After a ten-minute tow on the bottom the crew empty the catch onto the trawl deck for the scientists to pick through. A rough sort is done on deck and fragile creatures, like corals and sea pens are picked out and placed into trays before we shovel the rubble and rocks into fish bins to determine the total catch weight. 

Delicate organisms being picked out of the catch from the epibenthic sled on the trawl deck. The epibenthic sled is just on the left of the trawl deck.
There’s a lot of rubble to sort through from this sled tow. The substrate at this station was mainly brachiopod shells, pieces of bamboo coral skeleton and cobbles. Everyone has forceps at the ready to help sort through it. 

A finer sort through the muddy rubble is done in the shelter of our benthic lab, which is set up inside a shipping container. We use a large sorting table with a 5 mm mesh fitted into it, so that we can wash down the catch with seawater and pick out the fauna.

Malcolm Clark, NIWA and Amelia Connell, University of Auckland washing mud off the rubble, and sorting through to find animals.
Malcolm Clark and Sadie Mills, NIWA trying to determine what one of the animals pulled out of the sled is to figure out how to preserve it best for identification back on land.

After sorting, the fauna are put into appropriately sized jars and vials, registered into the NIWA Invertebrate Collection database and some are selected for live specimen photography before they are finally preserved. We use either ethanol or formalin to preserve our samples depending on the type of animal and to keep the specimens in the best condition for later identification and other analyses (such as phylogenetics, population genetics, aging, or stable isotope analyses) by experts back on land.

The photography of physical specimens collected from the seabed is an important part of the identification process because it allows taxonomists to see the live colour of the animal before we preserve them, and the tiny details and differences between species that are not visible in the seafloor images from DTIS.

A polychaete worm with delicate and slightly iridescent scales on its back and golden bristles which it uses to crawl along the sea floor, taken from one of the sled catches on Iselin Bank.
The same type of polychaete worm, and brittle stars seen roaming about on the seafloor at ~1000m on Iselin Bank.