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closeDisappearing ctenophores
Posted by shaddock on 04 Mar 2014 at 22:03 GMT
The data are pretty convincing for migration among smaller individuals, especially in Anholt (figure 3), but where do the large ctenophores go at night (Figure 4)? If it is solely a matter of vertical migration, then there should be "conservation of individuals" but there are essentially no adults sampled in the night data shown in Figure 4.
RE: Disappearing ctenophores
MatildaHaraldsson replied to shaddock on 07 Mar 2014 at 15:47 GMT
Dear Shaddock, thanks for your comment.
First of all we want to clarify that we showed DVM only for small and medium sized Mnemiopsis at Anhold station. Large individuals were in average found at the same depth at all times, hence, no DVM.
Having said that we agree that ultimately there should be a “conservation of individuals” between sampling occasions. However, as most pelagic ecologists has experienced, it is more or less impossible to sample “the same” water mass (and the individuals therein) twice. The movement of water (and individuals) will cause a variation between samples which you can see clearly form table 3, and is a common “problem” during zooplankton sampling. In addition, large individuals were generally underrepresented, and small changes in abundance between occasions will have a larger effect on underrepresented groups.
Despite that we found lower abundances at Ven C (I assume you mean the central panel Ven C, the noon station), all large individuals were found below the pycnocline at all times, and did not change our overall conclusion, that smaller sized Mnemiopsis (small and medium size classes in our case) are capable of DVM.