A More Detailed Look at Zooplankton--Salps & Their Poop

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Editor's note: Some science from Karen.  Zooplankton poop is the most globally significant fecal material.

One of the zooplanktonic critters that we catch in our nets from time to time is salps.  The species seen most commonly here in large numbers is Salpa thompsoni.  Salps have received a lot of attention in marine science lately due to the nature of their poop.  Compared with the fecal pellets of other marine zooplankton, the poop produced by salps is denser and in a larger pellet-like form.  Krill on the other hand produce a long strand of poop.  Copepod fecal pellets are much smaller.  The result of having such dense, large turds is that salp poop sinks faster and is not broken down as quickly as others as it sinks, making it a first-rate organic matter transporter from the surface waters where it is generated, to depth where it eventually settles.  This process is one mechanism that naturally sequesters carbon (organic matter) in the ocean.  Futher, salps are thought to thrive in relatively nutrient-poor waters, making them able to proliferate where other organisms, such as krill, may not.  

Salp species are found in the ocean world-wide.  They have two different adult life-cycle forms: aggregate and solitary.  Aggregates can form long chains, up to several meters in length.
4_Salp aggregate.jpg
Salpa thompsoni in aggregate form- note its pointy ends, characteristic of aggregates.  Also, note the lighter muscle bands and bright orange gut.  

Solitary salps are more barrel-shaped than aggregates, and in our net tows are less common.  Their poops are larger than aggregate poops, in fact, Kate, a scientist conducting fecal pellet production experiments on this cruise, nearly collapsed a large hard plastic carboy while trying to filter a solitary salp's poop, though she had filter plenty of aggregate salps' poop before with no problems.  Solitary salps reproduce asexually by budding off chains of tens to hundreds of clones, whereas aggregate salps reproduce sexually.  Younger chains of salps produce the female gametes, which are fertilized by male gametes from older chains.  Eventually, embryos are released and grow in the solitary form.  We sometimes catch salp embryos.
5_Salp embryo.jpg
A salp embryo

When we collect net tows in an area rich with salps, it's a big mess and takes a long time to sort though to find other non-salp zooplankton. This tends to happen at our offshore stations, rather than inshore; we have only had this situation once thus far.

Miram holds graduated cylinders full of salps that we have picked through for other zooplankton; this took around 10 hours!

A handful of salps in a strainer.

The weather on this cruise has been (typical of Antarctica) highly variable.  The majority of the time has been overcast.  We have had a few snow storms, and just yesterday we had to cancel science for the day because it was blowing 50 knots with 15 foot seas.  However, we have also had several beautiful days, with nice sun and moon rises and sets.

A lovely sunset
Editor's note: sunset pic inserted to counterbalance the poop.

An equally lovely and coinciding moon rise on the other horizon.

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This page contains a single entry by Andy Pershing published on February 1, 2012 8:00 AM.

Is Winter Getting Shorter? was the previous entry in this blog.

Growing Copepods is the next entry in this blog.

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