When I first spoke to Lauren regarding project ideas, I was given two choices of current projects to work on: larval settlement behaviour in turbulence (focused on Matlab analyses) or on deep-sea hydrothermal vent larvae identification (focused on microscopy). Being a sucker for statistics and data analyses, I naturally picked the former. Additionally, the lab’s work using particle image velocimetry (PIV) is a relatively new method of quantifying larval behaviour, and I wanted to gain some exposure to a new field since I’ve already done some larval identification work for a previous field course.
PIV. The vectors between the two annuli, in bold, are used to calculate local flow (Wheeler et al., 2013)
Larvae of benthic organisms, such as those of our study organism the eastern oyster (C. virginica), may adopt sensitivity to specific settlement cues for habitat optimization (there may be strong selection against those who don’t, who may then likely settle in unfortunate places such as the open ocean). Benthic regions such as oyster reefs are characterized by turbulent conditions, and it has been speculated that oyster larvae may use turbulence as a settlement cue. There has been mixed results in whether turbulence does induce settlement, and controversy over the possible confounding effects of artificial particles used in PIV (since an effective control, without particles, does not exist in these experiments since one cannot calculate relative larval velocity to the same degree of accuracy without them).
My project attempts to address 1. whether particles indeed affect the larvae (done by comparing the relative observed larval abundance and absolute verticle velocities in water seeded with algae and with particles); 2. whether turbulence affects the frequency of larval helical swimming behaviour (done by programming a script that can identify helical tracts); 3. how turbulence can affect phototaxis (done by the addition of light in turbulence experiments, which are typically done in the dark).
Experimental tank setup that we will be using for turbulence experiments. The two grids stir the tank at various frequencies to emulate different turbulence levels (Wheeler et al., 2013)
The experimental work, which will commence once the hatcheries have larvae available in mid-July, is done in a separate wet lab, the Shore lab. Although we will be using another tank set-up for the experiment (above), Jeanette Wheeler (a third-year graduate student) is piloting a new flume tank set-up, and we had a chance to poke around some of the setup there last week:
Class IV laser used to light the field of view
Larval injector (from which the larvae can enter the water column) with the camera setup. Since this tank is much bigger than the older experimental tank, it is more budget-friendly to inject the larvae upstream of the camera field of view, rather than distribute them randomly throughout the tank
Visualizing turbulence characteristics as the water flows around the injector (to emulate what the larvae would face) using fluorescein
Flourescein is pretty cool
As fun as Matlab is (<- I’m actually being completely serious), I’m definitely looking forward to the experimental work in mid-July. I wonder if I can raise baby oysters in a tank/watch them under a dissecting microscope when we’re done using them? One can certainly hope!