Quantifying the spatial and temporal variability of phytoplankton productivity from mobile autonomous platforms

The ability of remotely operated vehicles such as gliders and AUVs to combine physical data with information from biogeochemical sensors offers a potentially powerful, but currently under-evaluated tool, to understand complex physical-biogeochemical interactions controlling key processes such as carbon export to the deep ocean, controls on hypoxia and harmful algal blooms. Furthermore, these high-resolution datasets allow for the determination of process rates from state variables (e.g. Hull et al 2015). This capability presents opportunities for monitoring the health of the marine ecosystem from the ‘bottom up’; which is valuable to policy makers and implementing bodies in marine monitoring (for instance ensuring ‘good environmental status’ under the Marine Strategy Framework Directive in European waters); and relevant to future potential commercial initiatives to monitor the seas to ensure compliance with such legislation.
This project will focus on the factors governing the initiation and distribution of phytoplankton blooms, which have received recent attention (e.g. Behrenfield (2010), Mahadevan et al (2012)). The 40 year history of the Extended Ellett Line programme has shown that ships and gliders can measure the variability of large-scale physical properties in the open ocean. The next step is to relate this physical variability to biogeochemical indicators.
The student will use gliders equipped with biogeochemical sensors to collect oceanographic data and interpret the combined physical/biogeochemical observations.
This project will build on the technical expertise gained through a 2015 exploratory study (conducted by SAMS and AFBI) combining measurements from a glider and a ship to investigate the spatial and temporal evolution of a shelf based phytoplankton bloom.
In parallel to standard physical oceanographic measurements, biogeochemical sensors are capable of use on long deployments and can measure chlorophyll, CDOM, backscatter and oxygen concentrations.
Data will be collected during planned glider missions occupying the Extended Ellett Line (Scotland to Iceland) in 2016, 2017 and 2018. Results will be compared to ship and satellite based observations.

We will also take advantage of Cefas waveglider and UEA glider deployments in the North Sea to compare methodologies and results between deep ocean and a shallower environment and contextualize the glider data with parallel autonomous Smart Buoy measurements and the huge historical dataset available.
The project will allow an evaluation of the capacity for indirect determination of physical controls of phytoplankton bloom initiation and its horizontal/vertical distribution, water column biogeochemical characteristics, and from oxygen measurements (Hull et al. 2015), net community production (NCP).
The NEXUSS CDT provides state-of-the-art, highly experiential training in the application and development of cutting-edge Smart and Autonomous Observing Systems for the environmental sciences, alongside comprehensive personal and professional development. There will be extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial / government / policy partners. The student will be registered at the Scottish Association for Marine Science (SAMS). The student will primarily be based at SAMS, but will also spend extended periods of time at UEA to interact with Dr Johnson.
Specific training will include:
• Design and operation of remotely piloted marine glider surveys
• Physical and biogeochemical data collection and analysis
• Development of techniques to validate collected data
• Development of techniques to interpret and explain physical/biological interactions in contrasting environments
References
Behrenfield ML (2010) Abandoning Sverdrup’s Critical Depth Hypothesis on phytoplankton blooms. Ecology 91: 977-89
Hull T, Greenwood N, Kaiser J, Johnson M (2015) Uncertainty and sensitivity in optode-based shelf-sea net community production estimates, Biogeosciences Discuss 12:15611-15645
Mahadevan A, D’Asaro E, Lee C, Perry MJ (2012) Eddy-driven stratification initiates North Atlantic spring phytoplankton blooms. Science 337: 54–58.