Mechanisms shaping size structure and functional diversity of phytoplankton communities in the ocean

The factors regulating phytoplankton community composition play a crucial role in structuring aquatic food webs. However, consensus is still lacking about the mechanisms underlying the observed biogeographical differences in cell size composition of phytoplankton communities. Here we use a trait-based model to disentangle these mechanisms in two contrasting regions of the Atlantic Ocean. In our model, the phytoplankton community can self-assemble based on a trade-off emerging from relationships between cell size and (1) nutrient uptake, (2) zooplankton grazing, and (3) phytoplankton sinking. Grazing 'pushes' the community towards larger cell sizes, whereas nutrient uptake and sinking 'pull' the community towards smaller cell sizes. We find that the stable environmental conditions of the tropics strongly balance these forces leading to persistently small cell sizes and reduced size diversity. In contrast, the seasonality of the temperate region causes the community to regularly reorganize via shifts in species composition and to exhibit, on average, bigger cell sizes and higher size diversity than in the tropics. Our results raise the importance of environmental variability as a key structuring mechanism of plankton communities in the ocean and call for a reassessment of the current understanding of phytoplankton diversity patterns across latitudinal gradients

Proceedings - 2010 IEEE Electronics, Robotics and Automotive Mechanics Conference, CERMA 2010

569239

PhytoSFDM version 1.0.0: Phytoplankton Size and Functional Diversity Model

Biodiversity is one of the key mechanisms that facilitate the adaptive response of planktonic communities to a fluctuating environment. How to allow for such a flexible response in marine ecosystem models is, however, not entirely clear. One particular way is to resolve the natural complexity of phytoplankton communities by explicitly incorporating a large number of species or plankton functional types. Alternatively, models of aggregate community properties focus on macroecological quantities such as total biomass, mean trait, and trait variance (or functional trait diversity), thus reducing the observed natural complexity to a few mathematical expressions. We developed the PhytoSFDM modelling tool, which can resolve species discretely and can capture aggregate community properties. The tool also provides a set of methods for treating diversity under realistic oceanographic settings. This model is coded in Python and is distributed as open-source software. PhytoSFDM is implemented in a zero-dimensional physical scheme and can be applied to any location of the global ocean. We show that aggregate community models reduce computational complexity while preserving relevant macroecological features of phytoplankton communities. Compared to species-explicit models, aggregate models are more manageable in terms of number of equations and have faster computational times. Further developments of this tool should address the caveats associated with the assumptions of aggregate community models and about implementations into spatially resolved physical settings (one-dimensional and three-dimensional). With PhytoSFDM we embrace the idea of promoting open-source software and encourage scientists to build on this modelling tool to further improve our understanding of the role that biodiversity plays in shaping marine ecosystems

The Marine Biodiversity Observation Network Plankton Workshops: Plankton Ecosystem Function, Biodiversity, and Forecasting—Research Requirements and Applications

Plankton is a massive and phylogenetically diverse group of thousands of prokaryotes, protists (unicellular eukaryotic organisms), and metazoans (multicellular eukaryotic organisms; Fig. 1). Plankton functional diversity is at the core of various ecological processes, including productivity, carbon cycling and sequestration, nutrient cycling (Falkowski 2012), interspecies interactions, and food web dynamics and structure (D'Alelio et al. 2016). Through these functions, plankton play a critical role in the health of the coastal and open ocean and provide essential ecosystem services. Yet, at present, our understanding of plankton dynamics is insufficient to project how climate change and other human-driven impacts affect the functional diversity of plankton. That limits our ability to predict how critical ecosystem services will change in the future and develop strategies to adapt to these changes. The Marine Biodiversity Observation Network (MBON; https://geobon.org/bons/thematic-bon/mbon/, last accessed date: 22 Dec 2021), with the support of the Modelling Different Components of Marine Plankton Biodiversity team (MODIV; https://modiv.w.uib.no/, last accessed date: 22 Dec 2021), organized four virtual workshops (first in November 2020, second and third in October 2021, and fourth in November 2021) titled: “Plankton ecosystem functions, biodiversity, and forecasting—research requirements and applications” (https://eqmh.github.io/MBON-Plankton/index.html, last accessed date: 22 Dec 2021). The first workshop held in November 2020 was an initiative of the US-MBON and MODIV teams to bring together members of the ocean sciences community involved in plankton observing and modeling to meet, build rapport, and exchange expertise. The following workshops were organized to accommodate time differences: one for South, Central, and North America in October 2021; one for Africa, Europe, the Middle East, and India in October 2021; and one for East Asia and Oceania in November 2021. Each workshop was held for two consecutive days, and participation was limited to 20–25 participants per workshop to enable interactive discussions. In total, 80 participants from 26 countries attended at least one of the workshops (Fig. 2). A detailed list of participants can be found in the workshops' website (https://eqmh.github.io/MBON-Plankton/participants.html, last accessed date: 22 Dec 2021). The United States of America and Australia were the countries with the most participants, followed by Canada, Germany, China, the United Kingdom, and Argentina. The objectives of the workshops were to: (1) identify requirements with respect to the definition of essential ocean variables (EOVs) and associated measurements, as well as compile the data needed to address critical knowledge gaps related to the role of plankton biodiversity functions to provide ecosystem services; (2) discuss ways to better link empirical observations to theoretical concepts of plankton biodiversity and ecosystem dynamics; and (3) suggest methods to better communicate the value of plankton to peers and non-scientific audiences

The Marine Biodiversity Observation Network Plankton Workshops: Plankton Ecosystem Function, Biodiversity, and Forecasting—Research Requirements and Applications

ISSN:1539-6088ISSN:1539-607