Abstract
Communication among marine organisms are generally based on production, transmission, and interpretation of chemical cues. Volatile organic compounds (VOCs) can act as infochemicals, and ocean acidification can alter their production in the source organisms as well as the interpretation of the information they drive to target organisms. Two diatoms (Cocconeis scutellum var. parva and Diploneis sp.) and a macroalga (Ulva prolifera), all common epiphytes of Posidonia oceanica leaves, were isolated and cultured at two pH conditions (8.2 and 7.7). Their biomass was collected, and the VOCs produced upon wounding were extracted and analyzed using gas chromatography. Chemotactic reactions of invertebrates triggered by VOCs were tested using a static choice experimental arena and a flow-through flume system. Odor choice experiments were performed on several invertebrates associated with P. oceanica meadows to investigate the modification of behavioral responses due to the growth of algae in acidified environments. Complex patterns of behavioral responses were recorded after exposure to algal VOCs. This study demonstrated that a) ocean acidification alters the bouquet of VOCs released by diatoms and macroalgae and b) these compounds act as infochemicals and trigger peculiar behavioral responses in benthic invertebrates. In addition, behavioral responses are species-specific, dose-dependent, and are modified by environmental constraints. In fact, the static diffusion in choice arenas produced different responses as compared to flow-through flume systems. In conclusion, we demonstrate that in future marine environments higher CO2 concentrations (leading to a pH 7.7 by the end of this century) will modify the production of VOCs by micro- and macroalgae as well as the recognition of these infochemicals by marine invertebrates.
Highlights
Marine organisms use chemical cues to interact and communicate within environments suffused with information produced by prey, predators, competitors, and conspecifics (Brönmark and Hansson, 2000; Pohnert et al, 2007; Zupo and Maibam, 2011; Mutalipassi et al, 2019, 2021; Zupo et al, 2019)
Algae living in an acidified environment may modify the patterns of production of secondary metabolites, and this additional factor should be taken into consideration to understand “wrong” responses of target organisms (Poore et al, 2013; Jin et al, 2020). To understand these fundamental aspects within the complex ecology of the seagrass P. oceanica (L.) Delile, 1813 and the relationship among VOCs, vagile epifauna, and seawater acidification, we investigated the behavioral responses of invertebrates associated with P. oceanica meadows, exposed at current (8.2) and acidified (7.7) pH to volatile infochemicals produced by three sympatric algae, Cocconeis scutellum var. parva (Grunow) Cleve 1895, Diploneis sp
We confirmed that diatoms and macroalgae both produce VOCs acting as infochemicals for the invertebrates associated with the leaf stratum of P. oceanica
Summary
Marine organisms use chemical cues to interact and communicate within environments suffused with information produced by prey, predators, competitors, and conspecifics (Brönmark and Hansson, 2000; Pohnert et al, 2007; Zupo and Maibam, 2011; Mutalipassi et al, 2019, 2021; Zupo et al, 2019). This communication has evolved from bacteria to plants and animal to be considered a biological machineries able to sense and process key information (Vos et al, 2006). The term “infochemical” refers to compounds that bring an information possibly received and interpreted by various species living in the closer environment (Vet and Dicke, 1992; Zupo et al, 2019) Such chemical cues may play a key role in the ecology of organisms, both vertebrates, and invertebrates, associated with aquatic environments (Derby and Sorensen, 2008). Co-evolutionary constraints cause, as consequence, that invertebrates associated with seagrass meadow should be a) able to identify native “odors,” originally present in their specific habitat in comparison to a bouquet of various VOCs, and b) unable to identify and interpret “odors” typically produced by organisms living in different habitats (Jüttner et al, 2010)
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