Patrick,

Good point on the dead crustaceans and bacterial activity, but I think
you brought out an even larger problem with regard to dead animals.  As
far as I've learned from grade school biology, dead animals do not
evacuate their guts.  To take care of this I would probably separate
the live from the dead by having the dead settle out.  The pelagic
copepods I am working with will most likely be swimming around while
alive.  Plus, if I take only the swimmers, that will ensure that I am
getting the critters that are in the best condition for gut
evacuation.

Overall, the whole gut evacuation problem could be easily tested in the
lab or field.  I am working off a cross-shelf transect that has
nearshore 13C enriched environment (i.e. high upwelling and diatom
rich) and a depleted offshore.  It would be good for me to test this
out because of the difference in enriched diets between the two
regions.  I could test for gut evacuated vs non-evacuated from enriched
and nonenriched environments.  Any comments on this?

Best fishes,
Todd



----- Original Message -----
From: patrick dauby <[log in to unmask]>
Date: Thursday, April 26, 2001 7:04 am
Subject: Re: [ISOGEOCHEM] stable isotopes in crustaceans

> >Greetings,
> >
> >I would like to address a similar question on analysis of small
> >crustaceans, but this time regarding whether to analyze them with or
> >without an evacuated gut.  If samples are taken directly from the
> field>then I would assume I would want the crustaceans to evacuate
> their guts
> >before processing.  Is this necessary, or is the C and N contribution
> >in the gut so small as to not make a difference (if they eat as
> much as
> >I do in one sitting, this may make a substantial difference)?
> >
> >Todd
> >
>
> Todd,
> I understand your answer, but....
> Do you know relevant techniques for emptying small crustaceans (as
> copepods, eg) guts?
> Just keeping them in an aquarium flown with fresh seawater for a while
> (egestion time ?=half a day??)
> will provide you with a lot of dead animals the delta of which
> should be
> altered by bacterial activity.
> It is a problem which should be questioned by biogeochemists and
> oceanographers working with (palaeo-)plankton data...
> Pat
>
> __________________________________________________________
>
> Patrick DAUBY
> Universite de Liege
> Laboratoire d'Oceanologie
> Unite de Recherche en Biogeochimie des Isotopes Stables (URBIS)
> B6 Sart Tilman
> B-4000 Liege, Belgium
> Phone: +32.4.3663322  -  3663307
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> __________________________________________________________
>