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1. Understanding the Role of Macroalgal Complexity and Allelochemicals Production in Invasive and Non-Invasive Macroalgae in the North-Western Adriatic Sea: Effect on the Associated Communities

Author

Denise Lenzo, Marina Antonia Colangelo, Andrea Pasteris, Fabio Rindi, Rossella Pistocchi, and Laura Pezzolesi

Subjects
macroalgal structural complexity, polyunsaturated aldehydes, microphytobenthos, meiofauna, non-indigenous species, chemical ecology, Hydraulic engineering, TC1-978, Water supply for domestic and industrial purposes, TD201-500
Abstract

Highly diverse microphyto and meiobenthic communities are associated with large-sized marine macroalgae. Both morphological traits and allelochemical responses of macroalgae affect the composition of these communities, but the relative importance of these factors remains incompletely understood. In this study we investigated the microphytobenthic and meiobenthic communities associated with some native macroalgae and a non-indigenous species (Sargassum muticum) of the north-western Adriatic Sea. These seaweeds were sampled in two coastal sites subjected to different impacts. The possible effects of the structural complexity of the macroalgae and the potential role of allelochemicals (specifically polyunsaturated aldehydes, PUAs) on the associated communities were examined using univariate and multivariate analyses. The results indicate that distinct assemblages were associated with the macroalgae collected at the two different sites. Differences in microphytobenthic communities could be ascribed to differences in the macroalgal morphological traits and in their PUAs production. Conversely, variation of the meiobenthic community seemed to be related mainly to differences in the macroalgal communities at the two sites. This apparent inconsistency between the two analyzed communities suggests that microphytobenthos and meiofauna were differently shaped by the environmental habitat provided by macroalgae in the two sites, that are subjected to different environmental conditions and human activities. Overall, these results indicate that interactions between organisms belonging to different trophic groups (e.g., microphytobenthos and meiofauna) should be investigated in detail to better understand the global role of macroalgae as habitat formers on coastal ecosystems, especially in the case of large-sized introduced species.

Published
2023
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2. Allelopathic interactions between phytobenthos and meiofaunal community in an Adriatic benthic ecosystem: Understanding the role of aldehydes and macroalgal structural complexity

Author

Andrea Pasteris, Rossella Pistocchi, Fabio Rindi, Marina Antonia Colangelo, Laura Pezzolesi, Chiara Samorì, Denise Lenzo, Lenzo D., Pezzolesi L., Samori' C., Rindi F., Pasteris A., Pistocchi R., and Colangelo M.A.

Subjects
Aldehydes, Environmental Engineering, Brown macroalgae, biology, Ecology, Meiobenthos, Meiofauna, Community structure, Chemical ecology, biology.organism_classification, Pollution, Harpacticoid copepods, Food chain, Benthic zone, Microalgae, PUAs, Environmental Chemistry, Ecosystem, Epiphyte, Fucales, Waste Management and Disposal, Copepod, Harpacticoid copepod
Abstract

Macroalgae produce several allelopathic substances, including polyunsaturated aldehydes (PUAs), which may inhibit photosynthesis and growth rates of other algal species, and grazing. Additionally, macroalgal structural complexity is an important factor in determining abundance patterns and size structure of epiphytic organisms. In this study the PUAs production of two Mediterranean macroalgae, Dictyopteris polypodioides, (DP, Phaeophyceae, Dictyotales) and Cystoseira compressa (CC, Phaeophyceae, Fucales), was characterized to clarify the relationships between the meiobenthic and microphytobenthic communities. Results showed a higher PUAs production and a diverse qualitative profile for DP, which reported long-chain compounds (i.e. C14-C16) as main aldehydes, than CC, with the short-chain C6:2 as the main compound, as well as variability among sampling times. A clear separation of the meiofauna and microphytobenthos assemblages was found for the macroalgae, but with different temporal trends. Dissimilarities were due to five microalgal orders, namely Naviculales, Lyrellales, Gonyaulacales (i.e. Ostreopsis), Bacillariales, and Licmophorales, and to the meiofaunal groups nematodes, copepods, and copepod nauplii, which were more abundant on DP than on CC. Results indicate that macroalgal complexity is a major determinant of the meiofaunal community structure (accounting for 26% of the variation), rather than PUAs production itself (17%). PUAs effects seem species-specific, thus affecting some grazers instead of the entire community. Conversely, microphytobenthos affected the meiofauna assemblages, particularly harpacticoids, confirming the role of these organisms as the primary food source of all marine food chain producers. Since PUAs are produced also by several epiphytic diatoms, the understanding of their effects on the community structure and on the relationships among taxa in the field is complicated and requires further in-depth investigations in simplified systems (i.e. microcosms).

Published
2022

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