Plankton Communities

Plankton is a group of small organisms that are passively displaced by water, that is, they are dragged by marine tides and currents. Marine plankton, which includes organisms such as protozoa, microalgae, small crustaceans, and jellyfish, play an important role in maintaining the health and balance of the ocean and its complex food chains. Over three sections and eight chapters, this book provides a comprehensive overview of zooplankton and phytoplankton as well as their environmental and economic importance

Invasive non-native species and the management and exploitation of freshwater ecosystems

The effects of climate warming, hydrological intensification, and eutrophication are driving unfavourable shifts in phytoplankton communities. In particular, harmful algal blooms (HABs), dominated by toxic cyanobacteria, are becoming increasingly common and often lead to ecosystem collapse and unsafe drinking water. Freshwater ecosystems are also vulnerable to the establishment of invasive non-native species (INNS), whose prevalence has rapidly accelerated through the expansion of global travel, trade, and transportation. INNS can drive significant changes in habitat suitability and native community composition. I investigated how INNS affect the tipping points of freshwater ecosystems, between clear water and phytoplankton-dominated states, and influence phytoplankton community structure and cyanobacteria abundance. Through a meta-analysis of the global impacts of INNS on freshwater lake ecosystems, I identified that molluscs were potential drivers of a clear water state in lake ecosystems, encouraging system recovery and delaying ecosystem collapse. Invasive fish and crustaceans, however, were identified as potentially pushing systems towards a turbid state and resisting recovery. I further assessed the effects of invasive molluscs by quantifying the impacts of quagga mussels (Dreissena rostriformis bugensis) in UK reservoirs. I identified that impacted sites demonstrated: an increase in overall reactive silica and soluble reactive phosphorus concentrations; reductions in overall diatom, cyanobacteria and Aphanizomenon sp. abundance; and an increase in chlorophyll a concentration. However, no significant changes were seen in overall green algae, Microcystis sp., Anabaena sp., or Euglena sp. abundance, ammonium concentration or turbidity. The selective grazing behaviour of quagga mussels has been shown to vary between studies, an effect hypothesised to be driven by phenotypic plasticity or genotype selection between mussel populations. I explored putative population level differences in the discriminatory grazing behaviour of quagga mussels by observing mussels from both lentic and lotic environments, as hydrology is a known driver of phenotypic plasticity in mussels. I show that different populations of quagga mussels have the potential to drive different outcomes in phytoplankton communities. While both populations expressed comparable clearance rates and cleared green algae (Chlorella vulgaris) at a higher rate than cyanobacteria (Synechococcus elongatus), mussels from lotic environments ejected significantly greater quantities of cyanobacteria in pseudofaeces. Rejection of cyanobacteria by invasive mussels may drive HABs. Beyond invasive mussels, I also assessed the allelopathic effect of invasive plants Hydrocotyle ranunculoides and Crassula helmsii on phytoplankton communities. The allelopathic effect of each plant was tested in both a whole, and crushed state, to test for natural excretion of allelochemicals. In its whole state, H. ranunculoides supressed the growth of green algae (C. vulgaris), whereas crushed C. helmsii supressed the growth rate of both green algae and cyanobacteria (Synechocystis sp.). The species-specific nature of these allelopathic interactions suggests that the use of allelopathy for controlling phytoplankton abundance may have to be assessed on a case-by-case basis. Although, a sophisticated understanding of this differential sensitivity may also allow for some targeted management of phytoplankton populations towards specific desirable end points. Finally, I explored the potential role of invasive zebra mussels (Dreissena polymorpha) in the novel concept of Synthetic Ecology. I investigated how zebra mussel grazing behaviour could be harnessed to maintain favourable conditions for the cultivation of commercially valuable algae species in outdoor raceways by supressing the growth of competing cyanobacteria. Their potential was confirmed through the consistent preference for cyanobacteria (Synechocystis sp.) over green algae (C. vulgaris) observed across all treatment conditions. The results of this thesis suggest, in certain contexts and where risks are appropriately managed, there may be opportunities to harness INNS in order to drive favourable changes in the alternative equilibria of freshwaters, reducing both overall phytoplankton and cyanobacteria abundance in biologically depleted ecosystems

Festival of Research Abstracts, 2023

The collection of abstracts accepted for the 2023 Festival of Research hosted by the Wright State University College of Science and Mathematics

Advances on Applications of Bioactive Natural Compounds

This is a reprint of articles from the Special Issue published online in the open access journal Applied Sciences (ISSN 2076-3417) (available at: https://www.mdpi.com/journal/applsci/special issues/Bioactive Natural Compounds).info:eu-repo/semantics/publishedVersio

Advances on Applications of Bioactive Natural Compounds

Natural compounds, from terrestrial and marine sources, are the result of an evolutionary process which originated in compounds with great structural diversity, multiple biological activities and miscellaneous applications. A large and very active research field is dedicated to identifying biosynthesized compounds; to improve/develop new methodologies to produce/reuse natural compounds; to assess their potential; and to understand their mechanism of action. This Special Issue brings together excellent original and review works, focused on the most recent advances related to the secondary metabolites’ composition of natural sources, and the proposal of new applications for their constituents, such as therapeutic agents, and pesticides or food ingredients

Taxonomy and Ecology of Marine Algae

The term “algae” refers to a large diversity of unrelated phylogenetic entities, ranging from picoplanktonic cells to macroalgal kelps. Marine algae are an important primary producer in the marine food chain, responsible for the high primary production of coastal areas, providing food resources in situ for many grazing species of gastropods, peracarid crustaceans, sea urchins or fish. Recent findings indicate that marine environments have rapidly changed due to global warming over the past several decades. This change has led to significant variations in marine algal ecology. For example, a long-term increase in ocean temperatures due to global warming has facilitated the intensification of harmful algal blooms, which adversely impact public health, aquatic organisms, and aquaculture industries. Thus, extensive studies have been conducted, but there is still a gap in our understanding of the variation in their ecology in accordance with future marine environmental changes. To fill this gap, studies on the taxonomy and ecology of marine algae are highly necessary. We have invited algologists to submit research articles that enable us to advance our understanding of the taxonomy and ecology of marine algae. Fourteen papers have been collected so far, which cover different aspects of the taxonomy and ecology of marine algae, including understudied species, interspecific comparisons, and new techniques

State of the Art in Separation Science

In this Topical Collection, ten articles (one review and nine research articles) are published in a time span of 2021–2022. All articles are written by experts in the field of Separation Techniques who were invited to contribute to the presentation of the current status in separation science. The authors were invited to answer the questions: What is the state-of-the-art in Separation Sciences? What advances have been reported recently? Last but not least, what are the future perspectives? The Editor and authors hope that the readers will find valuable information in the topic

Application of Cytotoxicity Assays for Detection of Potentially Harmful Bioactive Compounds Produced by Freshwater Bloom-Forming Algae

Detection of harmful bioactive compounds produced by bloom-forming pelagic algae is important to assess the potential risks to communities. We applied two cell-based assays, an erythrocyte lysis assay (ELA) that assesses membrane integrity, and a RTgill-W1 cytotoxicity assay (RCA) that detects changes in cell metabolism, to evaluate the cytotoxic effects of: (1) individual toxins and noxious compounds; and (2) complex mixtures of compounds produced by cyanobacteria and chrysophyte isolates. ELA was insensitive to toxins and noxious compounds except at exceptionally high concentrations (EC50≥106 nM). RCA was sensitive to noxious compounds only, at concentrations greater than reported environmental averages (EC50≥103 nM). Cultured isolates produced bioactive compounds that had recognizable, dose dependent, toxic effects. Toxicity of these bioactive compounds depended on the taxa (cyanobacteria, not chrysophytes), growth stage (stationary phase more toxic than exponential phase), location (intracellular more toxic than extracellular), and iron status (iron-replete cells more toxic that iron-deplete cells)

Commercial and Therapeutic Potential of Plant-Based Fatty Acids

This chapter reviews plant-based fatty acids as well as their methods of production, applications in the industry, and benefits in treatments of cardiovascular and cerebral diseases, besides being a source of food. The fatty acids obtained from vegetable matrices have been acting as alternatives to the use of lipids of animal origin, due to their limitation in relation to the increase in demand. Thus, plants have been investigated in order to act as sources of fatty acids and assist in the supply of such demands. Vegetable oils represent not only an economical alternative but also a beneficial source of human health