Variability in turbulence fine structure and phytoplankton vertical distribution around Eddystone Rocks, western English Channel, UK 

Lead supervisor: Dr Jill Schwarz

Location: School of Biological & Marine Sciences, University of Plymouth

Duration: 7 weeks

Suitable undergraduate degrees: Marine biology, environmental science, maths, physics, computer science

Project background

The objectives of this work are to

i.  relate vertical variability in the dissipation rate of turbulent kinetic energy (ε) around the Eddystone Rocks (western English Channel) to the vertical structure in phytoplankton biomass and absorption properties;

ii.  quantify the sensitivity of ε to measured variability in the kinematic viscosity of seawater (ν),

on three days between June and August. Ancillary data, including satellite remote sensing and eDNA, will be used to aid interpretation and to place the findings in a broader spatial and temporal context.

Phytoplankton support the marine food web and account for some 50% of sequestration of anthropogenic CO2. The complex biotic-abiotic interactions that control the composition and performance of the pelagic microbial community remain a large source of error in climate models (Heinze et al., 2015; Holt et al., 2017). In situ measurements are still needed to develop parametrisations and support the use of remote sensing data to constrain model predictions (Bisson et al., 2018). This project will gather such data in a shelf sea area that is of interest as a fishing ground as well as in the climate context. The results will inform the next stage of research, which will include characterisation of biogenic material exported out of the mixed layer.

The study site lies 18 km south of Plymouth, in water depths up to 60 m. Previous work has demonstrated the sensitivity of phytoplankton abundance, vertical distribution and absorption to stochastic changes in turbulent mixing (Cross et al., 2014; Ford, 2017). This project will build on those results, focussing on three dates spanning summer 2021, with the expectation that the microbial community will be adapting to nutrient limitation. The student will gather high quality profiles of turbulent mixing parameters, using a shear profiler (ISW MSS) which includes temperature, salinity, pressure, chlorophyll fluorescence and turbidity sensors. Discrete water samples will be collected at a range of depths for filtration, microscopy and viscosity measurements. Other students and staff will focus on these data collection tasks but students will learn about each other’s focus areas (peer-teaching and staff guidance) and share processing duties in the lab. The placement student will be responsible for analysing the turbulence, fluorometer and viscosity data, though there is room to focus in on an aspect of especial interest to the student.

Bisson et al., 2018; doi:10.1029/2018GB005934

Cross et al., 2014; doi:10.1016/j.jmarsys.2014.03.009

Ford, 2017: http://hdl.handle.net/10026.1/14159

Heinze et al., 2015; doi: 10.5194/esd-6-327-2015

Holt et al., 2017; doi:10.5194/gmd-10-499-2017