14 - On marine snow and copepod poo (#Planktonpoo)

Powering up now for the #Planktonpoo Twitterfest on Monday (1200h GMT) with a great team on board the RRS James Cook  to respond. This will be Morten Iversen from Bremen with insights into particle degradation, Stephanie Wilson from Bangor working on plankton faecal characterisation and me from NOC, Southampton who has expertise in particle sinking. On shore there will also be a team of experts eager to communicate their work, so I think this should be a really good event. We have in fact finished the research programme at sea and are now steaming back towards Glasgow, where we started off just over two weeks ago. By Monday we will be within sight of land after some highly successful observations and experiments.

A “typical” marine snow aggregate collected by the Marine Snow catcher showing how it is a mixture of different types of material scavenged as the particle sank. Copyright© Richard Lampitt.

As we have reported before, this expedition has been over the Porcupine Abyssal Plain which lies around 350 miles southwest of Ireland (water depth 4800m), an area we like to think of as “typical” of the open ocean between the icy polar regions and the tropics. There is still a load of work to do, analysing the samples we have collected and processing the mass of data already in the bag, much of it to do with particles in the ocean, both dead and alive. But without a doubt there will be some really important things to say over the coming months when the processing has be done and the dots between the different studies conducted, have been connected.

An image taken by Morten earlier in the week from one of his “Gel traps”, a really neat way to collect sinking particles but without them ending up as a homogeneous mush at the bottom of the collecting cup. Copyright© Morten Iversen.

So what do we actually mean by “Plankton poo”? Well, this faecal matter is just one of several types of particle which sink under their own weight and thus transport carbon from the upper parts of the ocean down thought the twilight zone into the ocean's interior. But it is not only the poo of small planktonic animals that sink to the deep ocean. A more general term for such sinking particles is Marine Snow. It describes aggregations of all sorts of dead organic material and includes not only faecal material (plankton poo) but also aggregations of dead phytoplankton cells (microscopic plants), dead zooplankton, plankton moults and some inorganic minerals scavenged for good measure. Stuck together with a gluey matrix they can sink at rates between 100 and 1000m per day. On their way down they sometimes get caught and eaten by zooplankton before they arrive at the bottom of the ocean where they provide nourishment for other animals living on the seafloor.

By Richard Lampitt (Chief Scientist on James Cook cruise “Down to the Twilight Zone”)

See the latest #Planktonpoo tweets!