Contact- and Water-Mediated Effects of Macroalgae on the Physiology and Microbiome of Three Indo-Pacific Coral Species

Fong, Jim C.; Deignan, Lindsey K.; Bauman, Andrew G.; Steinberg, Peter D.; McDougald, Diane; Todd, Peter A.

doi:10.3389/fmars.2019.00831

Cited by 20 publications

(29 citation statements)

References 64 publications

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“…As with growth, impacts on coral photosynthetic efficiency were only evident when corals were in direct contact with macroalgae. This is consistent with previous evidence [26], but we also found that effects varied depending upon the approach used for measuring ϕ PSII values. When measurements taken haphazardly around the coral were averaged to acquire a mean photosynthetic efficiency for each individual, ϕ PSII values were significantly less for corals in direct contact with Sargassum, but not Galaxaura.…”

Section: Discussionsupporting

confidence: 93%

“…This again suggests macroalgal impacts are contact-mediated. Previous studies have found evidence for water-mediated algal effects on coral microbial communities, but these were either conducted in mesocosms [26,27] or involved some degree of coral-algal contact when conducted in the field [21,52]. Differences in experimental design, duration, or species used may explain discrepancies between these studies and our findings.…”

Section: Discussioncontrasting

confidence: 70%

“…It has been proposed that such indirect processes may harm corals that are centimetres to metres downstream of macroalgal competitors on reefs [23]. However, field-and tank-based studies, as well as hydrodynamic modelling efforts, suggest that water-mediated interactions are likely localized--operating at scales of centimetres or less near the coral-seaweed interface [10,13,[24][25][26][27]. Thus, the relevant scales and ecological effects of such mechanisms under realistic flow conditions in the field remain unclear.…”

Section: Introductionmentioning

confidence: 99%

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Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

et al. 2020

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A number of tropical reefs have transitioned from coral to macroalgal dominance, but the role of macroalgal competition in coral decline is debated. There is a need to understand the relative roles of direct coral-algal effects versus indirect, microbially mediated effects shaping these interactions, as well as the relevant scales at which interactions operate under natural field, as opposed to laboratory, conditions. We conducted a manipulative field experiment investigating how direct contact versus close proximity (approx. 1.5 cm) with macroalgae ( Galaxaura rugosa , Sargassum polycystum ) impacted the growth, photosynthetic efficiency, and prokaryotic microbiome of the common Indo-Pacific coral Acropora millepora . Both coral growth and photosynthetic efficiency were suppressed when in direct contact with algae or their inert mimics––but not when in close proximity to corals without direct contact. Coral microbiomes were largely unaltered in composition, variability, or diversity regardless of treatment, although a few uncommon taxa differed in abundance among treatments. Negative impacts of macroalgae were contact dependent, accounted for by physical structure alone and had minimal effects on coral microbiomes. The spatial constraints of these interactions have important implications for understanding and predicting benthic community dynamics as reefs degrade.

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Section: Discussionsupporting

confidence: 93%

Section: Discussioncontrasting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

et al. 2020

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“…Wainwright et al [13] attributed differences in coral microbiomes between Raffles and Kusu to the strong directionality of water movement from east to west differentially affecting the windward and leeward sides of Singapore's Southern Islands, particularly during the Northeast Monsoon [31]. The current study was conducted during the inter-monsoon period with light winds and relatively calm seas, which may explain why the coral microbiomes between the two reefs were not as divergent as in previous studies [13,30]. The mean seawater temperature of approximately 30 °C recorded at each reef and the nutrient concentrations are consistent with expectation for Singaporean waters [31,48].…”

Section: Discussionmentioning

confidence: 55%

“…This study focuses on Pocillopora acuta, a particularly resilient coral species found in relatively high abundance on reefs throughout Singapore's Southern Islands [25,29]. Previous studies have established that P. acuta located at Pulau Satumu (also referred to as Raffles Lighthouse) and Kusu Island, two of Singapore's Southern Islands separated by approximately 15 km, harbor distinct microbial communities, despite their spatial proximities [13,30]. The waters around the Southern Islands are thought to be well-mixed, but Kusu is located closer to the Singapore mainland and is therefore potentially more exposed to anthropogenic impacts [31].…”

Section: Introductionmentioning

confidence: 99%

Differential Response of the Microbiome of Pocillopora acuta to Reciprocal Transplantation Within Singapore

Deignan

McDougald

2021

Microb Ecol

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As corals continue to decline globally, particularly due to climate change, it is vital to understand the extent to which their microbiome may confer an adaptive resilience against environmental stress. Corals that survive on the urban reefs of Singapore are ideal candidates to study the association of scleractinians with their microbiome, which in turn can inform reef conservation and management. In this study, we monitored differences in the microbiome of Pocillopora acuta colonies reciprocally transplanted between two reefs, Raffles and Kusu, within the Port of Singapore, where corals face intense anthropogenic impacts. Pocillopora acuta had previously been shown to host distinct microbial communities between these two reefs. Amplicon sequencing (16S rRNA) was used to assess the coral microbiomes at 1, 2, 4, and 10 days post-transplantation. Coral microbiomes responded rapidly to transplantation, becoming similar to those of the local corals at the destination reef within one day at Raffles and within two days at Kusu. Elevated nitrate concentrations were detected at Raffles for the duration of the study, potentially influencing the microbiome’s response to transplantation. The persistence of corals within the port of Singapore highlights the ability of corals to adapt to stressful environments. Further, coral resilience appears to coincide with a dynamic microbiome which can undergo shifts in composition without succumbing to dysbiosis.

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Biodiversity of macroalgae does not differentially suppress coral performance: The other side of a biodiversity issue

Clements,

Pratte,

Stewart

et al. 2024

Ecology

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Hundreds of studies now document positive relationships between biodiversity and critical ecosystem processes, but as ecological communities worldwide shift toward new species configurations, less is known regarding how the biodiversity of undesirable species will shape the functioning of ecosystems or foundation species. We manipulated macroalgal species richness in experimental field plots to test whether and how the identity and diversity of competing macroalgae affected the growth, survival, and microbiome of a common coral in Mo'orea, French Polynesia. Compared to controls without algal competitors, coral growth was significantly suppressed across three macroalgal monocultures, a polyculture of the same three macroalgae, and plots containing inert seaweed mimics; coral mortality was limited and did not differ significantly among treatments. One macroalga suppressed coral growth significantly less than the other two, but none differed from the inert mimic in terms of coral suppression. The composition, dispersion, and diversity of coral microbiomes in treatments with live macroalgae or inert plastic mimics did not differ from controls experiencing no competition. Microbiome composition differed between two macroalgal monocultures and a monoculture versus plastic mimics, but no other microbiome differences were observed among macroalgal or mimic treatments. Together, these findings suggest that algal diversity does not alter harmful impacts of macroalgae on coral performance, which could be accounted for by physical structure alone in these field experiments. While enhancing biodiversity is a recognized strategy for promoting desirable species, it would be worrisome if biodiversity also enhanced the negative impacts of undesirable species. We documented no such effects in this investigation.

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Contact- and Water-Mediated Effects of Macroalgae on the Physiology and Microbiome of Three Indo-Pacific Coral Species

Cited by 20 publications

References 64 publications

Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

Differential Response of the Microbiome of Pocillopora acuta to Reciprocal Transplantation Within Singapore

Biodiversity of macroalgae does not differentially suppress coral performance: The other side of a biodiversity issue

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