Monday, 28 January 2013

COTF4: The Graveyard Shift

A well planned research expedition makes use of every available minute. The old adage ‘time is money’ definitely rings true for offshore scientific surveys. In order to make the most of this ship time we employ surveying and sampling techniques which don’t rely on daylight. These can include oceanographic mapping, video surveys for pelagic fauna and continuous sampling for plankton & microplastics.

My role onboard revolves around plankton sampling for which we make use of a CTD probe (which measures conductivity, temperature & depth, amongst other parameters). This probe is dropped vertically while the ship is stationary. It provides us with a good way of taking water samples, mounting plankton nets and other equipment such as a video camera system all at the same time. In addition to this it allows us to assess the different water masses from which we are sampling. The water below us is often stratified, with the strata having different salinities, temperatures and oxygen concentrations. The diversity of strata leads to diversity of organisms. We can measure photosynthesis (eg. phytoplankton) in each of these strata, as well as taking water samples at specific depths. This allows us to assess the origin of what we find in water samples, as each water mass, with its own distinct signature, comes from a different area (for example Mediterranean and Arctic waters can be distinguished from each other).

CTD being lowered for sampling (c) Emilia Chorazyczewska

CTD read out (c) Emilia Chorazyczewska

Plankton are sampled continuously on these vertical tows, and give us an idea of the various groups living in a column of water. So far on Cetaceans on the Frontier 4, our deepest drop has been to a depth of around 4.5km. During Cetaceans on the Frontier 3 in 2012, these small samples went on to be involved in studies involving genetic analysis of plankton and understanding how cetaceans fit into food webs using stable isotope analyses (their trophic ecology). This time around, despite some limitations related to weather, we have managed to take plankton samples for trophic studies of fish, sampled water to look for microplastics, aided in a test of acoustic releases for sensor moorings and tested an experimental camera system for studying plankton.

 Purpose built, deep sea camera (c) Fergal Glynn

 Plankton sample; a Euphausiid krill & two copepods (c) Fergal Glynn

There’s no working around the weather at the moment unfortunately. Even after we changed methods to try to deal with the swell and wind, we had to temporarily suspend sampling when it reached a solid seven (rather more wet and windy than solid!). We look forward to getting out and dropping some more sampling stations when we make a break for sea.

Watch this space for more updates from the graveyard shift.

Fergal Glynn
(Queen’s University Belfast)

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