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

Reporting period: 2019-10-01 to 2021-09-30

The basis upon which management tools for our oceans, seas and coasts operate are out-of-date as they assume, incorrectly, that the aquatic food-web operates like the terrestrial food-web.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 produce food in the oceans through photosynthesis. These are then assumed to be eaten by single-celled “animal-like” microzooplankton which themselves are eaten by larger organisms, and so on up to fish and other top predators. Over the last decade we have shown that this assumed plant-animal division at the base of marine food-webs is incorrect. The new paradigm 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, simultaneously. These organisms are the mixoplankton; they use multiple strategies to acquire nutrition. Many if not most of the organisms traditionally labelled as phytoplankton and as much as half of the organisms traditionally labelled as microzooplankton are actually mixoplankton. By mislabelling the organisms that form the base of the marine food chain, science and thence management policies have been hitherto labouring under false assumptions, with serious consequences.

Mixoplankton play a central role in the marine ecosystems and therefore in ecosystem services. As food for fish, mixoplankton support fisheries especially the juvenile fish during the summer months. Mixoplankton are also important in biogeochemical cycles as they remove atmospheric CO2. On the other hand, various mixoplankton can also cause severe harmful algal bloom events which can lead to extensive fish kills and closure of shellfisheries. 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.

The overarching objective of MixITiN was development and deployment of new methodologies for researching, monitoring and modelling the mixoplankton-based marine food chain to aid in updating environmental management tools and policies, and also to train the first of the next generation of marine researchers in the new paradigm.

At the end of 4 years, both those objectives have been met. A range of peer-reviewed scientific manuscripts have been published, and a suite of open access manuals (guides for field and laboratory techniques, protocols for molecular techniques and models for in silico experiments) have been developed and published. These manuals will not only enable the marine sector to start to integrate mixoplankton-facing research within their activities but also provide education material for the generation beyond MixITiN.
MixITiN employed 11 Early Stage Researchers (ESRs) who undertook research on individual projects in their host institutes and via secondments in other Consortium institutes. Various network-wide training events were delivered to the ESRs on mixoplankton eco-physiology, laboratory and field techniques, modelling, molecular techniques, public and media engagement, environmental management and policy making. During secondments the ESRs developed additional skillsets 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. ESRs also actively engaged with different audiences at face-to-face events and through social media using different languages exploiting the multicultural composition of the MixITiN team. These have brought to the attention of the audiences the general importance of plankton (which fixed 50% of the O2 we breathe), the curious means by which mixoplankton feed, and even mathematical modelling.

Work on mixoplankton brought together research approaches that are normally conducted separately, by different scientists, under the traditional phytoplankton-zooplankton paradigm. Established techniques do not cater for mixoplankton, so one of the aspirations of MixITiN was to develop and publish a range of guides and protocols to enable integration of mixoplankton within mainstream marine research. Against various challenges, the project has produced various new and interesting advances. To date there are 20 peer reviewed scientific outputs; additional manuscripts are in the process of being finalised for submission in 2021/22. Various protocols, manuals and booklets, even including an open access simulation model, have been published to address these challenges; most of these have been published as free e-books.

Different facets of MixITiN research have aided development and enhancement of skills of the ESRs in marine research. To date, 6 ESRs have been awarded PhDs and 3 ESRs have attained employment. As none of the latter 3 ESRs have been awarded a PhD, indeed 2 have not even submitted their theses, their success in gaining employment could be attributed directly to the excellent MixITiN training programme.
MixITiN aimed 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. Thus, a great deal of effort has been expended in generating baseline skill sets that have generated substantive advances in techniques.

MixITiN has worked to advance progress through public and scientific meetings and peer-reviewed publications. MixITiN also engaged with various public platforms from talks with school children through to senior citizens, radio, TV and the printed press. MixITiN social media have engaged the public and students. We organised the first ever mixoplankton conference which had over 250 pan-global registrants. MixITiN societal impact included direct communications as well as production of material to aid enhancement of management tools for safe-guarding and controlling the exploitation of marine resources. As members of the plankton, mixoplankton 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.

One of the aspirations of MixITiN has been to ensure a linkage between pure research and real world concerns. Highlights of MixITiN outputs in this regard include:
(i) “HABs and the mixoplankton paradigm” published in UNESCO Harmful Algae News no.67.
(ii) “Mixoplankton – marine organisms that break the rules!” published in highlighting importance of mixoplankton paradigm for ocean health and policies especially under climate change in the UN Ocean Decade.
(iii) MixoEdu - open access simple systems dynamics model to aid understanding of importance of the different plankton functional types under changing scenarios.
(iv) State-of-the-art protist plankton “perfect beast plus” model integrating the synergistic utilisation of traits by mixoplankton was deployed for the first time in a water column model showing importance of integrating mixoplankton functional types within climate change modelling studies.
Mixoplankton Science in MixITiN (Mitra & Irigoien 2021 EU Research)
Mixoplankton Paradigm in Un Ocean Decade (Mitra & Irigoien 2021 EU Research)
Mixoplankton Definition (Flynn et al. 2019 JPR)