Kevin entered the Denny Lab shortly after recieving his B.A. in Physics from the University of Chicago. His research interest is concerned with the role of size in biology. Size is considered one of the most important factors in an organism, from its physiology to it's ecological niche to it's mechanical constraints. He is currently engaged in two research projects related to this issue, in diatom buoyancy and coralline algal reproductive strategies.
Diatoms are arguably the most successful group of photosynthetic organisms on the planet. They are without a doubt the most abundant and diverse group of primary producers in the oceans, surpassed on land only by flowering plants. In terms of oxygen productions, they are unequalled, producing 40% of all marine oxygen. Not bad for a unicellular plant. Added to this impressive resume is the fact that this group of phytoplankton has no means of locomotion, meaning no way of moving up, towards the sun. Now you've worked yourself into a real conundrum. How did a group that can't even move around become one of the most successful photosynthetic groups on the planet?
Although possessing no means of locomoting, diatoms are not without movement- they can sink through the water. Kevin thinks the key to understand the success of diatoms lies in understanding their sinking- how they control it, how much it varies, etc. Yet there is a discrepancy in the literature concerning diatom sinking rates. Stokes law says that the sinking speed of a small, slow moving particle should scale with the size of a particle squared, or V~r^2. Diatoms are small, slow moving particles, so it seems reasonable that this theory should apply to them. Instead, empirical data on diatom sinking rates has found the exponent between sinking rate and size to be anywhere from 1 to 1.5, which is quite far from 2. Kevin's specific research is involved in solving this conundrum, and setting a baseline sinking rate for diatoms. So far, Kevin has created a way to accurately predict a diatom's sinking rate, which will aide models of diatom population dynamics and the cycle of carbon flux in the ocean, and generally help explain why diatoms are such a successful group.
Although a seemingly unrelated issue, the reproduction of coralline algae also concerns the mechanical constraints of an organism based on size. Coralline algae are calcified red algae that reproduce in unique structures called conceptacle. The conceptacles are hollowed cavities in the algal tissue in which spores are produced. Spores release from the conceptacle is a mostly undescribed process, though it is probably linked to mucilage production in some manner. The size and shape of both spores and the conceptacle can vary quite a bit, and seems to be somewhat correlated with the overall size of the alga.
Coralline alga are a very successful group of organisms, occupying nearly every marine coastal environment on the planet. They are also the deepest photosynthetic organism to be found yet, some reports finding corallines at depths greater than 250 m. How have corallines been able to occupy such a large range of niches? And what role has size played (spore size, plant size) in defining this niches? Kevin's research is concerned with understanding how size scaling issue in the reproduction of corallines can explain the diversity and success of this group.
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