The Influence of Phytoplankton Morphology on Dominance In Turbulent Regimes
Lead Research Organisation:
University of Bath
Department Name: Architecture and Civil Engineering
Abstract
This project looks to investigate the interactions between phytoplankton and turbulence under a variety of aquatic environments: freshwater reservoirs / lakes, brackish estuaries, and the coastal oceans. The primary aim of this study is to determine how the morphology (size, shape and structure) of various phytoplankton species dictates how they become dominant under a variety of turbulent regimes. This information is crucial in furthering our understanding of phytoplankton dynamics to better understand how growth, productivity, sedimentation and species diversity are affected especially as climate change continues to alter the physical and chemical characteristics of our ocean.
The project will involve a multi-disciplinary approach:
1) In-situ field verification via direct turbulence measurements and phytoplankton distribution analyses across a variety of aquatic environments. The proximity of the University of Bath to a number of freshwater lakes / reservoirs as well as the Bristol Channel makes this ideally suited to studying a variety of environments. In addition, current research into plankton-turbulence dynamics, turbulent-mixing and water quality at the WEIR unit would not only facilitate fieldwork logistics but also offers the opportunity for collaboration with researchers at Plymouth University.
2) An experimental approach to laboratory phytoplankton studies using 3D models in a turbulence simulator. Most laboratory work on phytoplankton sedimentation and turbulent-interaction is carried using either dead phytoplankton or idealised spherical models. Using 3D-printing technology, a variety of scale-models of phytoplankton would be produced and placed in a grid-generated turbulence simulator to investigate the effect of shape, size and buoyancy on how the species interacts with the turbulence. It is hoped that the production of tangible, macroscale phytoplankton models will also offer additional outreach opportunities in both schools and the local community. Dr M. Cherif at the University of Umea, Sweden has access to the 3D-printing centre and a 5m-deep mesocosm facilities with controlled mixing which would assist this component of the project.
3) The acquisition of existing data and the subsequent incorporation of this into conceptual phytoplankton models. This may involve developing a new way of representing how various phytoplankton species interact with turbulent diffusion processes particularly in terms of size dependence.
In this way, we aim to be able to predict which phytoplankton species will dominate at different depths and turbulent regimes, which is key for a range of scales and applications from reservoir water quality management up to global oceanic primary productivity.
The project will involve a multi-disciplinary approach:
1) In-situ field verification via direct turbulence measurements and phytoplankton distribution analyses across a variety of aquatic environments. The proximity of the University of Bath to a number of freshwater lakes / reservoirs as well as the Bristol Channel makes this ideally suited to studying a variety of environments. In addition, current research into plankton-turbulence dynamics, turbulent-mixing and water quality at the WEIR unit would not only facilitate fieldwork logistics but also offers the opportunity for collaboration with researchers at Plymouth University.
2) An experimental approach to laboratory phytoplankton studies using 3D models in a turbulence simulator. Most laboratory work on phytoplankton sedimentation and turbulent-interaction is carried using either dead phytoplankton or idealised spherical models. Using 3D-printing technology, a variety of scale-models of phytoplankton would be produced and placed in a grid-generated turbulence simulator to investigate the effect of shape, size and buoyancy on how the species interacts with the turbulence. It is hoped that the production of tangible, macroscale phytoplankton models will also offer additional outreach opportunities in both schools and the local community. Dr M. Cherif at the University of Umea, Sweden has access to the 3D-printing centre and a 5m-deep mesocosm facilities with controlled mixing which would assist this component of the project.
3) The acquisition of existing data and the subsequent incorporation of this into conceptual phytoplankton models. This may involve developing a new way of representing how various phytoplankton species interact with turbulent diffusion processes particularly in terms of size dependence.
In this way, we aim to be able to predict which phytoplankton species will dominate at different depths and turbulent regimes, which is key for a range of scales and applications from reservoir water quality management up to global oceanic primary productivity.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509589/1 | 01/10/2016 | 30/09/2021 | |||
| 1787179 | Studentship | EP/N509589/1 | 01/10/2016 | 30/09/2020 | Russell Arnott |
| Title | Sea Soup Quadtych |
| Description | As part of the "Visions in Science" exhibition at The Edge Arts Centre, University of Bath, I liaised with Bristol-based illustrator Scott Luis Masson to make an artwork based on my research. The exhibition called for "works that reflect, represent, capture or depict modern day scientific phenomena as studied by academics at The University's Faculty of Science. Visions of Science merges art and science, both fuelled by our curiosity as humans to understand the world and share our perspectives." In response, Masson produced the quadtych (each image representing a different turbulent regime), incorporating the phytoplankton species studied as well as technical drawings of the mesocosm facilities. |
| Type Of Art | Artwork |
| Year Produced | 2018 |
| Impact | As well as producing an eye-catching image which I now use to engage others with my research, the exhibit allowed artists that do not normally identify with science to engage with my research. Out of 180 artworks entered, Sea Soup won the Emerging Artist Award. |
| URL | https://slmillustration.com/sea-soup |
| Description | The overall aim of this project of this project is to ascertain to what extent morphology of the phytoplankton species studied dictates how they become dominant under different turbulent regimes. At present, there is some discrepancy between the output predictions of different ecological models and observations in the natural environment. It is hoped that this project will be able to, in part, account for these discrepancies thus improving future models. Further understanding of how turbulence and phytoplankton morphology influence resultant phytoplankton community and HAB distributions may contribute considerably to enhanced lake and reservoir management and general water quality awareness. Initially conceived with a view of refining the marine ecosystem model developed by Portalier et al. (2016), this research aims to increase the accuracy of predator-prey interactions within the model by accounting for turbulent processes. These processes originally focussed on turbulence as a means by which to influence predator-prey contact rates; here, I aim to facilitate the inclusion of turbulence effects as a key factor influencing the dominance of different groups of phytoplankton. This project also aims to continue to build a bridge between the realm of physical turbulence measurements and marine microbiology. While Peters and Redondo (1997) report a steep increase in the number of turbulence-phytoplankton interaction studies, there is still a tendency within the scientific community to work within carefully defined disciplinary spheres with biologists not fully appreciating the influence that turbulence can have on organisms and aquatic physicists overly simplifying biological interactions. The literature review found that most (82%) phytoplankton studies that make use of artificial turbulence feature some form of turbulence quantification. However, typical turbulent dissipation rates (e) used in these experiments (10-6 to 10-2 m2/s3) (Arnott et al., 2021) is often orders of magnitude higher than a cell would encounter in most natural environments (10-9 to 10-4 m2/s3)) (Wüest and Lorke, 2003; Fuchs and Gerbi, 2016). Furthermore, most cosm systems studied were not sufficiently large to accommodate the full range of turbulent length scales, omitting larger vertical overturns. Adding to the plethora of different techniques used to generate artificial turbulence in phycological studies, we used mild convective heating and cooling to generate different turbulent dissipation rates (e); a first in phytoplankton-turbulence studies. Regarding the quantification of e, the use of a microstructure profiler within a mesocosm facility was also a first, adding to the arsenal of methods that researchers can utilise in future studies. Using mild convective heating and cooling, we were able to generate a range of different turbulent dissipation rates (e) (between 5 x 10-10 m2/s3 to 3 x 10-8 m2/s3) resulting in a range of scenarios including stratified water columns, well-mixed water columns and two-layer mixed system separated by a strong thermocline. The range of e and the vertical overturns generated (Thorpe scales ranging from 0.015m to 0.728m) in this experiment were concurrent with those found in natural environments. Encouragingly, the various turbulent regimes initiated a biological response from the phytoplankton population; Chlorophyll-a and phycocyanin profiles suggest surfaces increases in cells in the weakly stratified regime while the strongly-stratified / two-layer mixed system observed increases at the thermocline. Looking at the response of the phytoplankton community, our findings are in line with phytoplankton-turbulence theory (Sverdrup, 1953; Huisman et al., 1999; Ross and Sharples, 2008) and field observations (Passow, 1991) that suggest motile cells have an advantage in calm, stable water columns in that they are able to position themselves preferentially in the upper photic layer. To this end, motile dinoflagellate groups (Peridiniales and Gymnodiniales) and the ciliate Mesodinium rubrum were able to achieve growth rates of 3.19 doublings over a 24-hour period in surface waters of stratified regimes. Conversely, immotile species and negatively buoyant diatoms were unable to maintain their position in the photic layer; thus, this regime had a detrimental impact on growth rates in these groups. More turbulent regimes allowed these immotile groups to persist by mixing them throughout the entire water column while motile species lost their competitive advantage. Focussing on the influence of morphology, cell size was found to be a significant determinant of growth rate in microplankton; large motile cells (>37 µm in diameter) out-performed motile cells of smaller diameters. However, attempts to separate the effect of morphology from other factors proved difficult as certain size-shape combinations were constrained to individual species, making a cross comparison difficult. Given the focus on morphology, it is recommended that particular species are chosen for specific functional traits (Fraisse et al., 2015) to better understand this influence in future studies In the nano- and picophytoplankton size ranges, picocyanobacteria (thought to be positively buoyant) and larger motile cells performed well in surface waters (2.26 doublings in 24 hours) while strongly mixed regimes experienced a reduction in growth (0.93 doublings in 24 hours). The influence of cell complexity on cells in the nano- and picoplankton range were seen to be non-significant. With regards to the HAB-forming ciliate, Mesodinium rubrum, hydrodynamic studies of Péclet numbers reveal that this species is unable to maintain an optimum position under mixed regimes while it was able to reach abundances of ~400 cells/ml in surface waters of stable, stratified water columns. While this association has been suggested from field observations (Lindholm and Mörk, 1990; Lips and Lips, 2017), often it has been attributed to high temperatures (Montagnes et al., 2008) and low salinities (Johnson et al., 2013) as opposed to a quantified water column stability. Modelling has shown that phosphate concentrations are a significant factor in determining M. rubrum abundances, in line with the field observations (Lips and Lips, 2017). Globally observed increases in water column stability (Li et al., 2020), eutrophication (Sinha et al., 2017) and HABs (Hallegraeff, 2010) all highlight the critical need for a better understanding of the drivers behind different HAB species, as highlighted by the research presented here. |
| Exploitation Route | Having developed and assessed an improved method for realistic turbulence generation, it is hoped that more practitioners adopt our technique in future experiments. It is hoped that this will in turn, make the prediction of Harmful Algal Blooms more reliable, especially in the face of cliamte change. |
| Sectors | Environment |
| Description | "Sea Soup - why you should care about plankton?" presentations for Cheltenham Science Festival / Royal Dublin Society |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Schools |
| Results and Impact | At Cheltenham Science Festival and then as part of the Cheltenham Science Festival LabLive schools tour, I spoke to audiences of primary & secondary pupils about plankton linking it to my research. I also did a number of talks as part of the Royal Dublin Society's Primary Science Fair in Limerick & Belfast to audiences of ~2000 primary schools. |
| Year(s) Of Engagement Activity | 2017,2018 |
| URL | https://www.cheltenhamfestivals.com/education/what-you-ve-missed/lablive/ |
| Description | "Sea Soup - why you should care about plankton?" workshops as part of National Science Week / Bath Taps Into Science |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Schools |
| Results and Impact | I trained members of department how do talk to primary school children about their research. Then we visited 3 primary schools local to Bath and conducted hands-on workshops about plankton which got children to use microscopes to find plankton and then draw it |
| Year(s) Of Engagement Activity | 2017,2018 |
| URL | https://www.flickr.com/photos/bathtaps/page3 |
| Description | European Researchers Night 2018 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | As part of European Researchers' Night (aka FUTURES NIGHT), I gave at talk about my research to a general public audience at We The Curious science centre. As part fo this I also helped organise a video-blogging course for GW4 academics so as to film other academics taking part in the event. The subsequent video I made on twitter has had over 10000 impressions and over 900 views. |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://twitter.com/Russell_Arnott/status/1047441587414990848 |
| Description | Maths skills and the marine environment : Does the shape of plankton affect how they sink? |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | Regional |
| Primary Audience | Public/other audiences |
| Results and Impact | Presented this hands-on activity as part of the Siren Calling climate festival in Aldeburgh, Suffolk, UK - taking place over 3 days, the festival saw 650 people from across the region visit the festival and engage with activities / talks themed around the impact of climate change on our ocean. |
| Year(s) Of Engagement Activity | 2019 |
| URL | https://www.sirencalling.org/ |
| Description | Micro-plants and mixing: The movements of 3D-printed phytoplankton |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Public/other audiences |
| Results and Impact | As part of a visit to the East Coast of the USA, I gave open presentations about my research to general audiences as well as undergraduates, post-graduates and academics. Talks were given at MBARI, Scripps Oceanographic Institute, & Moss Landing Marine Lab among others. |
| Year(s) Of Engagement Activity | 2018 |
| URL | https://www.mbari.org/february-28-russell-arnott-university-of-bath-united-kingdom/ |