New Challenges in the Biodiversity and Ecosystem of Phytoplankton

Dear Colleagues,

Biodiversity plays a central role in supporting ecosystem functioning and maintaining healthy ecosystems while providing numerous services which are vital for human well-being. Phytoplankton organisms, by fixing CO₂ from the atmosphere through photosynthesis, are a key component of the structure and function of marine ecosystems. Although the oceans cover a substantial portion of the Earth’s surface, our knowledge of biodiversity patterns in marine phytoplankton is very limited compared to that of the terrestrial world.

Phytoplankton forms a highly diversified group of prokaryotic and eukaryotic microorganisms and represents one of the paradigm systems for studies on the maintenance of species diversity. The maintenance of species diversity occurs in a constantly evolving network of chemical, physical, and biotic constraint interactions, which has only recently begun to be explored.

Phytoplankton cells span more than 4 orders of magnitude in size, varying from cells smaller than a micrometer to large diatom chains that can reach several millimeters in length. As a result, the pathways and efficiencies of transfer of carbon and energy to higher trophic levels depend on the abundance and composition of phytoplankton. Cell size not only defines the metabolic activity, growth rates, and numerical abundance, but it also strongly impacts biogeochemical cycles via size-dependent sinking and affects community structure and dynamics via size-dependent species interactions.

Several factors are known to affect phytoplankton species coexistence at a local scale, such as productivity, nutrient supply ratios, micronutrients (e.g., Fe), and underwater light. Geographical variation in these environmental factors has been implicated as a major determinant of large-scale patterns in phytoplankton diversity and consequently in trophic dynamics (e.g., size and grazing, grazing deterrents, toxin or allelopathic substances).

The available evidence suggests that many diversity productivity patterns are possible, and that these patterns change with the scale of observation, depending also on the history of the phytoplankton community. However, a complete understanding of the relative importance of different environmental drivers across small as well as large spatial scales is still lacking, and little is known about how future global warming might alter the phytoplankton biodiversity and associated ecosystem functioning.

Although microscopic, over recent decades, phytoplanktonic organisms have been shown to help to drive the global carbon cycle, providing important ecosystem services and benefitting human activities, such as aquaculture or biotechnological applications, including those linked to promoting human health.

Phytoplankton organisms, in fact, have exploited their metabolic systems to produce a frame of structurally- and functionally-diverse molecules to adapt to different ecosystems. Since natural products are the result of evolutionary selection for a function, microalgae can potentially produce specific secondary metabolites with different biological activities, such as allelopathic, antiproliferative, cytotoxic, anticancer, photoprotective, and antifouling. Because microalgae are very diverse and adapted to a broad variety of environmental conditions, the chances to find novel and unexplored bioactive metabolites with properties of interest for biotechnological and biomedical applications are high. For all these reasons, in the last decade, microalgae have attracted scientific attention, and cost-effective technologies are being developed to improve microalgal biomass production for the above applications.

In this Special Issue, we would like to understand how climatic variations interact with or override anthropogenic changes, affecting phytoplankton by eliciting physiological and adaptive responses, and indirectly by inducing hydrological and biological changes that influence both bottom–up and top–down processes. In addition, considering the capabilities of phytoplankton to synthetize bioactive metabolites with properties of interest for biotechnological and biomedical applications, we would like to provide a snapshot of some of the exciting research currently happening in this field and present a comprehensive overview of the current studies and also the available solutions to produce, explore, and exploit novel natural marine phytoplankton products.

Prof. Dr. Olga Mangoni
Guest Editor

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• Phytoplankton diversity
• Taxonomy
• Chemotaxonomy
• Size-classes
• Ecophysiology
• Photosynthetic pigments
• Photosynthetic efficiency
• Primary production
• Trophic relationships
• Nutrient uptake
• Iron
• Harmful algal blooms
• Eutrophication
• Water pollution
• Aquaculture and fisheries
• Time series
• Climate trends
• Changing Polar Environment
• Phytoplankton drug delivery
• Natural products
• Bioactive compounds
• Biotechnology