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Here are three pairs of
species in the same genera, plotted again with months on the x axis and
density per cubic meter on the y axis.
Note, though, that each chart now shows both depths, with the light
color representing water above the pycnocline, and the dark color
representing water below it.
Note also that the scales are not standardized. These graphs show some very
interesting results.
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The two species of Centropages show incredibly sharp temporal
differentiation, with hamatus declining just as typicus appears in the water
column. Contrast this with
Acartia, in which both species have peak abundances in the same month. However, look at the vertical
distributions of Acartia: longeremis is much more prevalent in the
sub-pycnocline waters, while hudsonica shows slightly higher numbers above the
thermocline.
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Lastly, both species of
pseudocalanus show the same pattern: newmani is much more abundant in
surface waters, while moultoni is almost absent from surface waters until
the fall. These species show
strong affinities for certain depths, which in turn has large consequences
in how they are differentially transported by currents in the gulf of maine.
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Now I want to broaden our
view again, and re-address the entire community. The graphs I showed before are nice for picking out the
dominant species, but it is difficult to perceive how the community is
changing as a whole. For this
purpose, I am using Multi-Dimensional Scaling, or MDSÉ
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