The view of a data scientist - BONUS BIO-C3 & BONUS INSPIRE
Functional diversity aka "how big are the zooplankton"?
Today I had to figure out, how big are different members of zooplankton. The best way of visualising it was to look up their sizes (and for the sake of fun, how they look like), and then draw them in the same scale on one page. Although I like numbers, sometimes I still need visualize them in some way to better understand the difference in values, for example.
As a side note - it's also easier to memorise new facts if you connect them with pictures. I often look up the authors or research papers – knowing how they look like makes their papers and research to come alive for me. So - that's how my top picks from the Pärnu Bay zooplankton community look like, were they to swim next to each other:
From species richness to functional diversity
My drawing above also illustrates most important functional trait for all living organisms, from bacteria to whales – the body size. In this drawing, I’ve only picked examples from multicellular zooplankton in Pärnu Bay, but it already covers one magnitude of size differences (from 0.3mm to 3.0 mm).
Functional diversity has become a hot topic over the last one or two decades. It is believed to be more informative for understanding the ecosystem functioning than simple species richness. But functional traits are also used to unravel the rules of coexistence in natural communities. Researchers look at the species, and try to figure out, whether some species are more likely to tolerate each other, if they are more similar or less similar to each other. And that similarity is measured from the characteristics of species that matter for their success. Size is the most obvious of all functional traits, but it can also be the way you gather food, or how long it takes you to grow up, and so forth.
An order of magnitude
Smallest of the zooplankton in my drawing are the rotifers Keratella and Synchaeta, in the lower left corner, reaching at most 0.3 mm in length. Small cladoceran (based on the photos of Bosmina) above them is slightly bigger – 0.6-0.9 mm long. Same size (0.5mm) are the nauplii of small copepods (small "tick" next to the tail of the the biggest animal in this drawing), while the adults can be 1.2-1.3 mm long.
Then come the large cladocerans – Daphnia (big guy in the middle) and Cercopagis (with a long tail). I was especially interested to see the size differences between Cercopagis, and small copepods and Bosmina. Cercopagis is a non-native and invasive predator, who has in other ecosystems before shaped the zooplankton community, especially by preying on the small cladocerans and copepods. Cercopagis is peculiar for its long tail that did not even fit on this picture (can be 10 mm long), and an alien like body, which is ironic (since non-native species are sometimes also called “alien” species).
And, at the top, the true giant here with its 3 mm body length in right side of the picture is Limnocalanus macrurus, most frequent representative of large copepods in the Baltic Sea.
And after this exercise, I think I will never forget the size difference between small cladocerans and large copepods.