Benthic Cyanobacterial Diversity and Antagonistic Interactions in Abrolhos Bank: Allelopathy, Susceptibility to Herbivory, and Toxicity

Abstract

Benthic cyanobacterial mats (BCMs) are conspicuous components of coral reef communities, where they play key ecological roles as primary producers among others. BCMs often bloom and might outcompete neighboring benthic organisms, including reef-building corals. We investigated the cyanobacterial species composition of three BCMs morphotypes from the marginal reef complex of Abrolhos Bank (Southeastern Brazil). Also, we assessed their allelopathic effects on coral zooxanthellae, their susceptibility to herbivory by fish, and their toxicity to brine shrimp nauplii. Morphology and 16S rDNA sequencing unveiled the cyanobacteria Moorena bouillonii, Okeania erythroflocculosa, Adonisia turfae, Leptolyngbya sp., and Halomicronema sp. as components of BCMs from Abrolhos. BCMs cell-free filtrates and extracts exerted an allelopathic effect by reducing the growth of the ex hospite Symbiodinium sp. in culture. BCMs-only treatments remained untouched in field susceptibility assays in contrast to macroalgae only and mixed BCMs-macroalgae treatments that had the macroalgae fully removed by reef fish. Crude aqueous extracts from BCMs were toxic to brine shrimps in acute assays. Besides unveiling the diversity of BCMs consortia in Abrolhos, our results cast some light on their allelopathy, antiherbivory, and toxicity properties. These antagonistic interactions might promote adverse cascading effects during benthic cyanobacteria blooms and in gradual shifts to BCMs-dominated states.

Predation, community asynchrony, and metacommunity stability in cyanobacterial mats

“…varying biotic and abiotic context; Cissell et al 2019, Ford et al . 2021, Ribeiro et al 2022 ) to better understand the influence of predation in driving the structure and dynamics of cyanobacterial mat communities and metacommunities.…”

“…Linkages among metabolic asynchrony, biodiversity maintenance, predation pressure, and community spatiotemporal asynchrony warrant further exploration across diverse systems with differing levels of predation pressure (i.e. varying biotic and abiotic context; Cissell et al 2019, Ford et al 2021, Ribeiro et al 2022) to better understand the influence of predation in driving the structure and dynamics of cyanobacterial mat communities and metacommunities.…”

Divide and conquer: Spatial and temporal resource partitioning structures benthic cyanobacterial mats

“…The differences in the strengths of these interaction allow us to discern how communities and energy flow will change under predation pressure (Paine, 1980). Grazing of cyanobacteria and BCMs has been seen in coral reef environments by predators including fish, sea cucumbers, and other invertebrates (Cissell et al, 2019;Cruz-Rivera & Paul, 2000;Ford et al, 2021;Manning & McCoy, 2023;Ribeiro et al, 2022;Thacker et al, 2001). In addition to top-down control in tropical ecosystems, mats in temperate marine and freshwater ecosystems also experience grazing pressure from fish, ciliates, gastropods, and more (Ackermann et al, 2011;Aguilera et al, 2013;Armitage & Fong, 2004;Clements et al, 2017;Gerbersdorf & Wieprecht, 2015;Tuchman & Stevenson, 1991).…”

Top-heavy trophic structure within benthic viral dark matter

“…These shifts in reef carbon chemistry can alter systemic microbial energetic budgets, and favor the proliferation and stability of pathogenic taxa (43), potentially including pathogenic taxa involved in coral disease (44). Horizontally-spreading reef cyanobacterial mat carpets are subject to dynamic predation pressure from generalist reef fishes and specialist invertebrate mesograzers (45, 46), with substantial geographic and morphotypic-dependence in predation risk from macro- and mesopredators (32, 47, 48). Viral interactions with coral reef benthic cyanobacterial mats have only recently been explored (38, 49, 50), and viral ecology in cyanobacterial mats remains generally relatively unknown.…”