Marine organisms rely on chemical cues - most as scents - to obtain information (i.e. infochemicals) about their environment. Volatile organic compounds (VOCs) from plants represent one group of infochemicals that can shape ecological interactions and the structure of the ecosystems through the influence of behaviour of receivers. However, there is still little evidence about the ecological importance of VOCs on the structure and interactions of mesograzers community within ecosystems like the Mediterranean seagrass Posidonia oceanica.
The studies presented in this thesis were designed, using behavioural choice assays, to investigate the effects of epiphytes-borne VOCs from Posidonia oceanica on the associated benthic invertebrates and further clarify how their responses to these putative infochemicals could affect the spatial organization of this stable community. The objectives of this thesis were: 1) to standardize a behavioural choice method for benthic invertebrates (e.g. static chambers vs. flumes and the determination of the species-specific minimum number of replicates); 2) to define the existence of associative behavioural patterns of invertebrates (i.e. molluscs and decapods) to epiphyte-borne VOCs at the community level; 3) to identify the roles of VOCs as infochemicals (e.g. food or toxins cues); and 4) to investigate the behavioural responses to infochemicals within the range of pH levels predicted for the end of this century. Species-specific behaviours of mesograzers to VOCs depended on the method of investigation, the concentration of VOCs tested, body constraints and animal ecology.
Overall, the contribution of this thesis to knowledge is that, within ecosystems like the seagrass P. oceanica, co-evolutionary patterns of infochemicals create microhabitats and the coexistence of herbivores on a single plant leaf. These findings support a better understanding of the entire ecosystem for further coastal management also in prevision of near-future climate changes.
Table of Contents
1. Introduction
1.1 Overview
1.2 The general context of marine chemical ecology
1.3 The current knowledge on infochemicals
1.4 Volatile Organic Compounds from marine plants and their functions as infochemicals
1.5 The method: behavioural choices in the investigation of infochemicals
1.6 Behavioural traits and mechanisms of chemoreception in marine invertebrates
1.7 The seagrass Posidonia oceanica, its epiphytes and associated invertebrates
1.8 Epiphytes-herbivores interactions: the role of infochemicals within Posidonia oceanica ecosystem
1.9 Research aims and objectives
2. VOCs of epiphytes from Posidonia oceanica trigger infochemicals based communication for benthic inverterbrates
2.1 INTRODUCTION
2.2 MATERIALS AND METHODS
2.2.1 Isolation and culture of benthic epiphytes from the seagrass Posidonia oceanica
2.2.2 Extraction of algal odours: VOCs
2.2.3 Study organisms: animal sampling and biology
2.2.4 Experiment 1: choice assay in static chambers
2.2.5 Experiment 2: choice assay in straight flow-through flume
2.2.6 Baseline choice assays
2.2.7 Distribution of VOCs in static chambers
2.2.8 Distribution of VOCs in straight flow-through flume
2.3 STATISTICAL ANALYSIS
2.3.1 Standardization of behavioural data
2.3.2 Effect of time in behavioural responses of invertebrates
2.3.3 Recognition of algal odours and associative patterns
2.3.4 Distribution of odours in static chambers and in straight flow-through flumes
2.4 RESULTS
2.4.1 Kriging analysis for the diffusion in static chambers
2.4.2 Kriging analysis for the flow in straight flow-through flume
2.4.3 Behavioural responses of invertebrates to VOCs in static chambers
2.4.4 Behavioural responses of invertebrates to VOCs in flumes
2.4.5 Behavioural associative patterns to VOCs
2.5 DISCUSSION
2.6 CONCLUSION
3. Epiphyte-borne infochemicals rule the community structure of mesograzers in seagrasses
3.1 INTRODUCTION
3.2 MATERIALS AND METHODS
3.2.1 Study organisms: animal sampling and biology
3.2.2 Production of epiphytes: seaweeds and diatoms
3.2.3 VOCs extraction
3.2.4 Gel preparation and concentrations
3.2.5 Behavioural choice tests
3.2.6 Standardization of behavioural choice test: controls
3.3 STATISTICAL ANALYSIS
3.3.1 Standardization of controls
3.3.2 Behavioural choices to VOCs, effect of concentration and time of exposure
3.3.3 Multivariate analysis: taxonomy vs. environmental hypothesis
3.4 RESULTS
3.4.1 Control experiments: the need for standardization of behavioural data
3.4.2 Responses to VOCs, concentrations and time of exposure for each mesograzer
3.4.3 Responses of the community of mesograzers to infochemicals
3.5 DISCUSSION
3.5.1 The mesograzers’ standardized behaviour
3.5.2 Volatile epiphyte-borne infochemicals structure mesograzers’ microhabitat selection upon the leaves of Posidonia oceanica
3.6 CONCLUSION
4. Decoding the messages beyond epiphyte-borne volatiles: food kairomones, alarm and habitat cues
4.1 INTRODUCTION
4.2 MATERIALS AND METHODS
4.2.1 Animal collection
4.2.3 Preparation of artificial foods
4.2.4 Feeding test and survival
4.2.5 Statistical analysis
4.3 RESULTS
4.3.1 Putative toxicity
4.3.2 Feeding preferences
4.4 DISCUSSION
4.5 CONCLUSION
5. Ocean acidification effects on the behaviour of mesograzers to epiphyte-borne infochemicals
5.1 INTRODUCTION
5.2 MATERIALS AND METHODS
5.2.3 Animal collection and epiphyte cultures
5.2.4 Simulated ocean acidification treatment
5.2.5 Experimental design and behavioural choice tests
5.2.6 VOCs extractions and gels preparations
5.2.7 Statistical analysis
5.3 RESULTS
5.3.1 Responses of molluscs to volatile infochemicals at different pH
5.3.2 Responses of decapods to volatile infochemicals at different pH
5.3.3 Reactions of mesograzers’ community to infochemicals at different pH
5.4 DISCUSSION
5.5 CONCLUSION
6. Discussion and Conclusion
6.1 General discussion
6.2 Conclusions and future directions
6.2.1 Epiphyte-odours are infochemicals for benthic invertebrates
6.2.2 Epiphyte-borne infochemicals structure the benthic community within the Posidonia oceanica ecosystem
6.2.3 OA disrupts behaviour to infochemicals and indirectly the structure of ecosystems
Research Objectives and Themes
This thesis explores the role of volatile organic compounds (VOCs) released by algal epiphytes as infochemicals within the seagrass ecosystem Posidonia oceanica, investigating how these chemical cues influence the behavioral choices, habitat selection, and community structure of associated benthic invertebrates, especially in the context of predicted ocean acidification.
- Standardization of behavioral choice assays for benthic invertebrates.
- Assessment of behavioral patterns of molluscs and decapods in response to epiphyte-borne VOCs.
- Evaluation of VOCs as food-finding cues or toxic triggers for associated invertebrates.
- Analysis of the influence of taxonomic relatedness versus environmental plasticity on behavioral responses.
- Investigation into the impact of ocean acidification on chemical communication and ecosystem structure.
Excerpt from the Book
1.2 The general context of marine chemical ecology
Chemical signals represent the words of the ‘language’ of life in the sea (Kittredge et al. 1974; Atema, 1995; Hay, 1996) and marine chemical ecology refers to the study of these signals involved into the biotic and abiotic interactions among marine organisms and their environment (Hay, 2009). Thus, the main purpose of chemical ecology is to translate this language from chemistry to ecology in order to understand better how to manage the structure and functions of natural ecosystems (Kubanek, 2014; Hay, 2014).
Since the 1980s, chemical ecology was considered as an integrative science between the field of chemistry and ecology (Pawlik, 1993; Ianora et al. 2011). Indeed, at least four different fields of science convey in chemical ecology: (i) chemistry, that identifies molecules acting as chemical cues; (ii) ethology, that clarifies the effects of these chemicals on animal behaviour; (iii) neuroscience, that determines the mechanisms involved in the reception of these molecules and (iv) ecology, that recognizes the central role of chemicals in driving the structure of populations, communities and evolutionary processes (Fig. 1.1 from Derby and Sorensen, 2008).
Summary of Chapters
CHAPTER 1: Provides a comprehensive introduction to marine chemical ecology, defining the role of VOCs as infochemicals and setting the stage for the specific study of Posidonia oceanica interactions.
CHAPTER 2: Investigates the behavioral responses of various invertebrates to epiphyte VOC bouquets, evaluating two distinct methodologies and establishing the role of VOCs as potential infochemicals.
CHAPTER 3: Focuses on the role of epiphyte-borne infochemicals in structuring the community of mesograzers, testing the "taxonomic" versus "environmental" hypotheses through behavioral choice tests.
CHAPTER 4: Decodes the nature of the messages conveyed by VOCs, specifically analyzing whether they serve as food kairomones or indicate the presence of toxic compounds using forced feeding experiments.
CHAPTER 5: Explores the effects of ocean acidification on these chemical interactions, assessing whether lower pH levels disrupt behavioral responses and alter community chemical relationships.
CHAPTER 6: Synthesizes the findings of the thesis, providing a general discussion on the implications of chemical ecology for coastal management and outlining future research directions.
Keywords
Marine Chemical Ecology, Posidonia oceanica, Volatile Organic Compounds (VOCs), Infochemicals, Mesograzers, Benthic Invertebrates, Ocean Acidification, Behavioral Choice Assays, Kairomones, Community Structure, Microhabitat Selection, Epiphytes, Chemical Communication, Ecological Interactions.
Frequently Asked Questions
What is the central focus of this research?
The thesis examines how volatile organic compounds (VOCs) released by algal epiphytes on the seagrass Posidonia oceanica function as infochemicals to influence the behavior and community organization of associated benthic invertebrates.
Which organisms are specifically studied?
The research focuses on a range of benthic mesograzers, including gastropods (e.g., Alvania lineata, Rissoa italiensis), decapods (e.g., Hippolyte inermis, Cestopagurus timidus), and various polychaete species.
What is the primary scientific method used?
The work employs standardized behavioral choice assays, specifically using static chambers and flow-through flumes, combined with multivariate statistical analyses and separate-offer feeding experiments to quantify responses.
How do VOCs affect the community structure?
VOCs act as specific chemical cues that allow mesograzers to fine-tune their distribution based on their specific ecological niches and microhabitats on the Posidonia oceanica leaf axis.
Does ocean acidification disrupt these interactions?
Yes, the study indicates that ocean acidification can act as an 'info-disruptor,' causing invertebrates to switch their behavioral patterns and potentially leading to a simplification of chemical relationships within the ecosystem.
What do the findings suggest for environmental management?
The findings emphasize that chemical communication is a critical factor in maintaining biodiversity, and suggest that management strategies for coastal ecosystems should account for the indirect impacts of global climate change on these chemical networks.
What is the "Environmental hypothesis" tested in Chapter 3?
This hypothesis posits that mesograzers respond to VOCs based on their familiarity with the infochemicals of their own preferential microhabitat, rather than purely due to their taxonomic relatedness.
Are the VOCs from all epiphytes equally recognized?
No, the study reveals that responses are species-specific; for instance, some invertebrates showed strong attraction to cyanobacterial VOCs, while others were repelled or indifferent to those from macroalgae.
- Citar trabajo
- Emanuela Butera (Autor), 2015, Volatile Organic Compounds from Marine Plants: Effects on the Behaviour of Benthic Invertebrates, Múnich, GRIN Verlag, https://www.grin.com/document/368922
