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Bringing the paradigm for marine pelagic production into the 21st century: incorporating mixotrophy into mainstream marine research

Periodic Reporting for period 1 - MixITiN (Bringing the paradigm for marine pelagic production into the 21st century: incorporating mixotrophy into mainstream marine research)

Reporting period: 2017-10-01 to 2019-09-30

The basis upon which management tools for our oceans, seas and coasts operate are out-of-date as they assume, incorrectly, that the aquatic food-web operates like the terrestrial food-web. Thus, the expectation is that the single-celled “plant-like” phytoplankton (microalgae) produce food in the oceans through photosynthesis. The one-celled “animal-like” microzooplankton consume these microalgae and then themselves get eaten by fish and other predators. Over the last decade we have shown that this plant-animal division is not the rule in marine food-webs. The new paradigm in marine ecology recognises that most of the single-celled organisms at the base of the oceanic food-web can hunt like animals and also photosynthesize like plants, all in the one cell. These organisms are the mixoplankton; they use multiple strategies synergistically to acquire nutrition. Indeed, most of the organisms conventionally labelled as phytoplankton and as much as half of the organisms traditionally labelled as microzooplankton are actually mixoplankton. Science has been mislabelling these organisms that form the base of the marine food chain, and provide 50% of the oxygen we breathe.
Mixoplankton play a central role in the marine ecosystems and therefore on ecosystem services. As food for fish, mixoplankton support fisheries especially the juvenile fish during the summer months. Mixoplankton are also important in biogeochemical cycles are they remove atmospheric CO2. On the other hand, various mixoplankton can also cause severe harmful algal bloom events which could lead to massive fish kills or closure of shellfish hatcheries. Some mixoplankton blooms have so discoloured coastal waters that it has led to a decrease in sea-side property prices. Thus, from a societal point of view it is important to have an understanding of the conditions which lead to the proliferation of the mixoplankton – good or bad.
There are therefore two main objectives of MixITiN:
(i) to develop and deploy new methodologies for researching, monitoring and modelling the mixoplankton-based marine food chain to aid in the updating of environmental management tools and policies;
(ii) to train the next generation of marine researchers in the new mixoplankton paradigm.
The project started on 1 October 2017. It employs 11 Early Stage Researchers (ESRs). All the lead scientists were involved in the recruitment process of the 11 MixITiN ESRs. Since their appointments, ESRS have been undertaking research on their individual projects in the host institutes and have also undertaken secondments in other MixITiN Consortium institutes. Various network-wide training events have been delivered to the ESRs over the last two years - at Helsingør (Denmark) on mixoplankton ecology, physiology and modelling, and on environmental management and policy making; Roscoff (France) on molecular techniques and field sampling; Swansea (UK) on public and media engagement techniques. During secondments the ESRs have developed additional skill sets to those exploited in their core work, on aspects of the ecology and physiology of the fundamentally different groups of mixoplankton, and developing new experimental, molecular and modelling approaches.
Laboratory work has seen extensive study on cultured organisms and interactions with their prey. Much of MixITiN the field work (North Sea, Mediterranean) and laboratory work to date has included developing new approaches and enhancing skills of the ESRs in the complex and diverse facets of plankton photosynthesis and predation. This is work that is normally conducted separately, by different researchers, under the traditional phytoplankton-zooplankton paradigm. Molecular biological and modelling work is likewise far more complex under the mixoplankton paradigm. Against the challenges, there are good signs that the project is producing new and interesting advances. As scientific outputs, one paper has already been published in the peer-reviewed Journal of Plankton Research (Flynn et al. 2019). One paper (Anschütz & Flynn 2020, Marine Biology) is currently in press. Various manuscripts are submitted or in the process of being finalised for submission in 2020.
ESRs actively engage with different audiences through social media using different languages exploiting the multicultural composition of the MixITiN team. Examples include blogs (on the project website tweets (@mixotroph) and Facebook posts ( ESRs have also been involved in various outreach events. ESRs have thus had experience of delivering activities to non-English speaking audiences and also to school pupils with various levels of hearing impairment (including profoundly deaf). These have brought to the attention of the audiences the general importance of plankton (which fix 50% of the O2 we breathe), the exciting means by which mixoplankton feed, and even mathematical modelling.
MixITiN seeks to develop new means to enhance our understanding of mixoplankton ecology with respect to who-is-doing-what-to-whom-where-when-and-how, and developing laboratory, field and modelling techniques to further marine science. Providing information to enhance understanding and the construction of simulation models that ultimately define our understanding of the system, requires the development of new laboratory and field techniques. This is challenging work especially for culture and fieldwork; while output progress within MixITiN in some areas has been excellent, in other areas approaches will give rewards later in the project. Thus a great deal of effort has been expended in generating baseline skill sets and data that will over the second half of the project generate substantive advances; the learning curve is steep. Studies of living organisms, coupled with the exploitation of molecular tools, in both instances in controlled (laboratory) environments and at sea, are providing a catalogue of physiological data for rates of growth, photosynthesis and grazing, prey selection and the like, together with advances in single-cell molecular approaches.

Societal impact will emerge largely through the enhancement of management tools for safe-guarding and controlling the exploitation of marine resources. Plankton are key indicators of water quality, and their presence and activity have impacts all the way from public use of beaches to fisheries production and climate change mitigation. To enhance such tools requires both conceptual modification and appropriate simulation tools for “what-if?” tests. Perhaps of greater importance is the change in mindset required in established workers to break away from a century of phytoplankton-zooplankton dogma to embrace the mixoplankton paradigm. The next generations need to be informed of how the system really works as well. MixITiN is working to advance progress through public and scientific meetings and information. We have attended, and will increase attendance and engagement with, various public platforms from talks with school children through to senior citizens, radio, TV and the printed press (all across various European languages). Our own website, Twitter and social media feeds are also exploited to engage the public and students. We also attend scientific meetings (such as harmful algal bloom and modelling-focussed events), many of which are multi-disciplinary. This work will culminate in autumn 2020 with our own international conference.
Mixoplankton and the new paradigm in marine ecology (Flynn et al. 2019 JPR)
Finding poetry in mixoplankton with the help of Shakespeare