Multivariate trait analysis reveals diatom plasticity constrained to a reduced set of biological axes

Trait-based approaches to phytoplankton ecology have gained traction in recent decades as phenotypic traits are incorporated into ecological and biogeochemical models. Here, we use high-throughput phenotyping to explore both intra- and interspecific constraints on trait combinations that are expressed in the cosmopolitan marine diatom genus Thalassiosira. We demonstrate that within Thalassiosira, phenotypic diversity cannot be predicted from genotypic diversity, and moreover, plasticity can create highly divergent phenotypes that are incongruent with taxonomic grouping. Significantly, multivariate phenotypes can be represented in reduced dimensional space using principal component analysis with 77.7% of the variance captured by two orthogonal axes, here termed a ‘trait-scape’. Furthermore, this trait-scape can be recovered with a reduced set of traits. Plastic responses to the new environments expanded phenotypic trait values and the trait-scape, however, the overall pattern of response to the new environments was similar between strains and many trait correlations remained constant. These findings demonstrate that trait-scapes can be used to reveal common constraints on multi-trait plasticity in phytoplankton with divergent underlying phenotypes. Understanding how to integrate trait correlational constraints and trade-offs into theoretical frameworks like biogeochemical models will be critical to predict how microbial responses to environmental change will impact elemental cycling now and into the future.

The global scientific literature on applications and trends in the use of functional morphological groups in phytoplankton studies

Aim The application of deconstructive approaches in aquatic ecology has been increasing recently. Especially for phytoplankton, some functional classifications summarize similar traits of a group of species to understand organisms’ response to landscape variability. One of these approaches deals with phytoplankton functional classification based on morphology (MBFG - Morphologically Based Functional Groups). Focusing on this approach, we systematic mapping the scientific literature to reveal this functional framework´s applications for freshwater phytoplankton. Methods For this study, we selected from the Thomson ISI Web of Science database all articles published between 2010 and 2018 dealing with MBFG. We recorded 179 manuscripts citing the phytoplankton functional classification based on morphology and, among them, we excluded three due to lack of access to information. Results A clear temporal trend occurred with an increase in citations involving the morphological approach, with Brazil, Uruguay, and China as the countries with the highest number of studies. Of the total records, 60 manuscripts applied morphological classification in their studies, of which 23 manuscripts comprised comparative studies with other functional approaches. Most applications were for phytoplankton in lakes, with biomass being the most used metric for framing taxa in MBFG. The most often recorded groups are MBFG IV (medium-sized organisms without specialization), VII (large mucilaginous colonies), and III (large filamentous organisms with aerotopes). Conclusion This study showed an increasing trend in the number of studies that used the functional approach based on MBFG. We believe that deconstructive approaches, such as MBFG, help assess issues of interest in phytoplankton ecology.

Under-Ice Phytoplankton Blooms: Shedding Light on the “Invisible” Part of Arctic Primary Production

The growth of phytoplankton at high latitudes was generally thought to begin in open waters of the marginal ice zone once the highly reflective sea ice retreats in spring, solar elevation increases, and surface waters become stratified by the addition of sea-ice melt water. In fact, virtually all recent large-scale estimates of primary production in the Arctic Ocean (AO) assume that phytoplankton production in the water column under sea ice is negligible. However, over the past two decades, an emerging literature showing significant under-ice phytoplankton production on a pan-Arctic scale has challenged our paradigms of Arctic phytoplankton ecology and phenology. This evidence, which builds on previous, but scarce reports, requires the Arctic scientific community to change its perception of traditional AO phenology and urgently revise it. In particular, it is essential to better comprehend, on small and large scales, the changing and variable icescapes, the under-ice light field and biogeochemical cycles during the transition from sea-ice covered to ice-free Arctic waters. Here, we provide a baseline of our current knowledge of under-ice blooms (UIBs), by defining their ecology and their environmental setting, but also their regional peculiarities (in terms of occurrence, magnitude, and assemblages), which is shaped by a complex AO. To this end, a multidisciplinary approach, i.e., combining expeditions and modern autonomous technologies, satellite, and modeling analyses, has been used to provide an overview of this pan-Arctic phenological feature, which will become increasingly important in future marine Arctic biogeochemical cycles.

Freshwater phytoplankton diversity: models, drivers and implications for ecosystem properties

Our understanding on phytoplankton diversity has largely been progressing since the publication of Hutchinson on the paradox of the plankton. In this paper, we summarise some major steps in phytoplankton ecology in the context of mechanisms underlying phytoplankton diversity. Here, we provide a framework for phytoplankton community assembly and an overview of measures on taxonomic and functional diversity. We show how ecological theories on species competition together with modelling approaches and laboratory experiments helped understand species coexistence and maintenance of diversity in phytoplankton. The non-equilibrium nature of phytoplankton and the role of disturbances in shaping diversity are also discussed. Furthermore, we discuss the role of water body size, productivity of habitats and temperature on phytoplankton species richness, and how diversity may affect the functioning of lake ecosystems. At last, we give an insight into molecular tools that have emerged in the last decades and argue how it has broadened our perspective on microbial diversity. Besides historical backgrounds, some critical comments have also been made.