South Parks Road
I am a Departmental Research Lecturer in
of Zoology at Oxford
University. I am broadly
interested in the interaction between fluid dynamics and microbial
ecology, especially that arising in bacteria,
spermatozoa, and phytoplankton.
Using a combination of laboratory experiments (ranging from µm to cm in
scale), simple models, numerical simulations, and field observations, my
collaborators and myself try to better understand these small but very
important members of the Earth.
My CV is available here.
Phytoplankton Layers: Characteristics, Mechanisms, and Consequences
Review of Marine Science
'Thin layers' are a spectacular form of
patchiness in the distribution
of phytoplankton. By confining a large number of primary producers
to small depth intervals, these structures act as oases for higher
trophic levels in a ocean where
resources are often too scarce
to permit survival.
this review article, we survey the salient features of thin layers, the
mechanisms at play and mathematical techniques used to infer them in the
field, and their impacts on the marine ecosystem. We argue that the time
is ripe for the development of a quantitative, predictive framework to
better understand their occurrence and, consequently, their ecological
our article here.
in a steady vortical flow
We show that gyrotactic motility within a vortical flow leads to tightly
clustered aggregations of microorganisms. Two dimensionless numbers,
characterizing the relative swimming speed and stability against
overturning by shear, govern the coupling between motility and flow.
Exploration of parameter space revealed a striking array of patchiness
regimes. We find that patches form under conditions typical of small-scale
marine turbulence, suggesting that this mechanism may be responsible for
observed microscale heterogeneity in the distribution of phytoplankton.
Read our article here.
Microbial alignment in
ﬂow changes ocean light climate
Proceedings of the National Academy of Sciences, USA
Whirls of E.
The growth of microbial cultures in the laboratory is often informally
assessed with a quick flick of the wrist: dense suspensions of
microorganisms produce translucent ‘swirls’ when agitated. Here, we
rationalize the mechanism behind this phenomenon and show that the same
process may affect the propagation of light through the upper ocean.
Read the article.
Tumbling for Stealth?
In this perspective article, we comment on the implications of a recent
article by Polin et al. that
found the phytoplankton Chlamydomonas
reinhardtii can actively synchronize and desynchronize its
flagella to swim in a "run and tumble" manner reminiscent of the enteric
bacteria E. coli. We
suggest this movement behavior might be a strategy to reduce predator
Read our article here
and Polin et al. here.
Disruption of Vertical
Motility by Shear Triggers Formation of Thin Phytoplankton Layers
Thin layer development via gyrotactic trapping.
nivalis (small black dots) swimming in a variable
shear flow .
this paper we demonstrate that thin layers of phytoplankton can be
generated by a coupling between motility, cell morphology, and
hydrodynamic shear; a process we call 'gyrotactic
trapping.' Using a suite of physical experiments and
modeling, we show that the vertical motility of phytoplankton is inhibited
in regions of enhanced shear and leads to dense aggregations of
Read our article
and the accompanying perspective article by
- New York Times
articles about our work:
New York Times
Science Home Page
see page 5
Environmental Research Web (UK)
A sea urchin egg fertilized only minutes before.