The Relevance of Marine Chemical Ecology to Plankton and Ecosystem Function: An Emerging Field

Abstract

Marine chemical ecology comprises the study of the production and interaction of bioactive molecules affecting organism behavior and function. Here we focus on bioactive compounds and interactions associated with phytoplankton, particularly bloom-forming diatoms, prymnesiophytes and dinoflagellates. Planktonic bioactive metabolites are structurally and functionally diverse and some may have multiple simultaneous functions including roles in chemical defense (antipredator, allelopathic and antibacterial compounds), and/or cell-to-cell signaling (e.g., polyunsaturated aldehydes (PUAs) of diatoms). Among inducible chemical defenses in response to grazing, there is high species-specific variability in the effects on grazers, ranging from severe physical incapacitation and/or death to no apparent physiological response, depending on predator susceptibility and detoxification capability. Most bioactive compounds are present in very low concentrations, in both the producing organism and the surrounding aqueous medium. Furthermore, bioactivity may be subject to synergistic interactions with other natural and anthropogenic environmental toxicants. Most, if not all phycotoxins are classic secondary metabolites, but many other bioactive metabolites are simple molecules derived from primary metabolism (e.g., PUAs in diatoms, dimethylsulfoniopropionate (DMSP) in prymnesiophytes). Producing cells do not seem to suffer physiological impact due to their synthesis. Functional genome sequence data and gene expression analysis will provide insights into regulatory and metabolic pathways in producer organisms, as well as identification of mechanisms of action in target organisms. Understanding chemical ecological responses to environmental triggers and chemically-mediated species interactions will help define crucial chemical and molecular processes that help maintain biodiversity and ecosystem functionality.

Chemotaxis of Marinobacter adhaerens and Its Impact on Attachment to the Diatom Thalassiosira weissflogii

“…Consequently, future experiments will elucidate the importance of molecular interaction mechanisms on global processes (30), particularly on the efficiency of the oceanic carbon pump.…”

Growth and bioactive secondary metabolites of arctic Protoceratium reticulatum (Dinophyceae)

“…Allelochemical, or lytic activity in marine phytoplankton is an emerging field, and numerous reports have published negative effects in protist interactions such as inhibition of growth or photosynthesis or even death of competitors or grazers (Cembella, 2003;Legrand et al, 2003;Ianora et al, 2011). Allelochemical effects are well documented for a number of dinoflagellate HAB species and were found to be unrelated to the presence of the known phycotoxins.…”

Host-released dimethylsulphide activates the dinoflagellate parasitoid Parvilucifera sinerae

“…The suggestion has faced opposition on the basis of the lack of knowledge on their specificity, the mechanisms of infection and the potential side effects (Anderson, 2009). The debate has prompted the need for a better understanding of parasitoid À host interactions, along the same lines as the increasing interest in chemical ecology and interspecific communication in oceanic plankton (Ianora et al, 2011).…”

“…Therefore, its release must be unavoidable or its costs must be outweighed by the aforementioned physiological benefits. In any case, this stands as one of the scarce examples of a chemically-mediated arms race in the coevolution of plankton microbes (Smetacek, 2001;Ianora et al, 2011).…”