Nutrient starvation impairs the trophic plasticity of reef‐building corals under ocean warming

Ezzat, Leïla; Maguer, Jean‐François; Grover, Renaud; Rottier, Cécile; Tremblay, Pascale; Ferrier‐Pagés, Christine

doi:10.1111/1365-2435.13285

Cited by 38 publications

(33 citation statements)

References 65 publications

(125 reference statements)

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“…Given our 8-week observation period and a comparatively cold water temperature, our study did not provide a setting to trace severe bleaching effects and for the Southern Red Sea it was speculated that higher nutrient availability might even benefit P. verrucosa to resist higher water temperature (Sawall et al, 2014a). This corroborates that effects of eutrophication on coral health are not always negative (Bongiorni et al, 2003;Sawall et al, 2011;Ezzat et al, 2019) and do not necessarily harm or kill individual coral colonies but get outcompeted or overgrown over time (reviewed in Fabricius, 2005). Longer (3 years; Vega Thurber et al, 2014), and both longer and stronger (1 year, 36.2 mM NH þ 4 ; Koop et al, 2001) N manipulation could, however, lead to increased coral mortality (Koop et al, 2001).…”

Section: Utilization Of Excess N By Benthic Functional Groupssupporting

confidence: 59%

Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea

Karcher

Roth

Carvalho

et al. 2020

PeerJ

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While various sources increasingly release nutrients to the Red Sea, knowledge about their effects on benthic coral reef communities is scarce. Here, we provide the first comparative assessment of the response of all major benthic groups (hard and soft corals, turf algae and reef sands—together accounting for 80% of the benthic reef community) to in-situ eutrophication in a central Red Sea coral reef. For 8 weeks, dissolved inorganic nitrogen (DIN) concentrations were experimentally increased 3-fold above environmental background concentrations around natural benthic reef communities using a slow release fertilizer with 15% total nitrogen (N) content. We investigated which major functional groups took up the available N, and how this changed organic carbon (Corg) and N contents using elemental and stable isotope measurements. Findings revealed that hard corals (in their tissue), soft corals and turf algae incorporated fertilizer N as indicated by significant increases in δ15N by 8%, 27% and 28%, respectively. Among the investigated groups, Corg content significantly increased in sediments (+24%) and in turf algae (+33%). Altogether, this suggests that among the benthic organisms only turf algae were limited by N availability and thus benefited most from N addition. Thereby, based on higher Corg content, turf algae potentially gained competitive advantage over, for example, hard corals. Local management should, thus, particularly address DIN eutrophication by coastal development and consider the role of turf algae as potential bioindicator for eutrophication.

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Section: Utilization Of Excess N By Benthic Functional Groupssupporting

confidence: 59%

Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea

Karcher

Roth

Carvalho

et al. 2020

PeerJ

View full text Add to dashboard Cite

show abstract

“…Given our eight-week observation period and a comparatively cold water temperature, our study did not provide a setting to trace severe bleaching effects and for the Southern Red Sea it was speculated that higher nutrient availability might even benefit P. verrucosa to resist higher water temperature (Sawall et al, 2014a). This corroborates that effects of eutrophication on coral health are not always negative (Bongiorni et al, 2003;Sawall et al, 2011;Ezzat et al, 2019) and do not necessarily harm or kill individual coral colonies but get outcompeted or overgrown over time (reviewed in Fabricius, 2005). Longer (3 years;Vega Thurber et al, 2014), and both longer and stronger (1 year, 36.2 μM NH 4 + ; Koop et al, 2001) N manipulation could, however, lead to increased coral mortality (Koop et al, 2001).…”

Section: Utilization Of Excess N By Benthic Functional Groupssupporting

confidence: 58%

Peer Review #1 of "Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea (v0.1)"

2020

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While various sources increasingly release nutrients to the Red Sea, knowledge about their effects on benthic coral reef communities is scarce. Here, we provide the first comparative assessment of the response of all major benthic groups (hard and soft corals, turf algae, and reef sands-together accounting for 80 % of the benthic reef community) to in-situ eutrophication in a central Red Sea coral reef. For eight weeks, dissolved inorganic nitrogen (DIN) concentrations were experimentally increased 3-fold above environmental background concentrations around natural benthic reef communities using a slow release fertilizer with 15 % total nitrogen (N) content. We investigated which major functional groups took up the available N, and how this changed organic carbon (C org) and N contents using elemental and stable isotope measurements. Findings revealed that hard corals (in their tissue), soft corals, and turf algae incorporated fertilizer N as indicated by significant increases in δ 15 N by 8 %, 27 % and 28 %, respectively. Among the investigated groups, C org content significantly increased in sediments (+24 %) and in turf algae (+33 %). Altogether, this suggests that among the benthic organisms only turf algae were limited by N availability and thus benefited most from N addition. Thereby, based on higher C org content, turf algae potentially gained competitive advantage over e.g. hard corals. Local management should, thus, particularly address DIN eutrophication by coastal development and consider the role of turf algae as potential bioindicator for eutrophication.

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“…Seascape-Scale Effects across Habitats and Taxa. Coral bleaching stems from multiple mechanisms operating at a variety of spatial and temporal scales (36,37), where finer-scale processes are constrained by processes at higher levels [i.e., hierarchy theory (38)]. For example, within a coral colony, bleaching can be variable, and likewise two colonies side by side can exhibit vastly different bleaching responses (39).…”

Section: Discussionmentioning

confidence: 99%

Nitrogen pollution interacts with heat stress to increase coral bleaching across the seascape

Donovan

Adam

Shantz

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

121

106

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Climate change is increasing the frequency and magnitude of temperature anomalies that cause coral bleaching, leading to widespread mortality of stony corals that can fundamentally alter reef structure and function. However, bleaching often is spatially variable for a given heat stress event, and drivers of this heterogeneity are not well resolved. While small-scale experiments have shown that excess nitrogen can increase the susceptibility of a coral colony to bleaching, we lack evidence that heterogeneity in nitrogen pollution can shape spatial patterns of coral bleaching across a seascape. Using island-wide surveys of coral bleaching and nitrogen availability within a Bayesian hierarchical modeling framework, we tested the hypothesis that excess nitrogen interacts with temperature anomalies to alter coral bleaching for the two dominant genera of branching corals in Moorea, French Polynesia. For both coral genera, Pocillopora and Acropora, heat stress primarily drove bleaching prevalence (i.e., the proportion of colonies on a reef that bleached). In contrast, the severity of bleaching (i.e., the proportion of an individual colony that bleached) was positively associated with both heat stress and nitrogen availability for both genera. Importantly, nitrogen interacted with heat stress to increase bleaching severity up to twofold when nitrogen was high and heat stress was relatively low. Our finding that excess nitrogen can trigger severe bleaching even under relatively low heat stress implies that mitigating nutrient pollution may enhance the resilience of coral communities in the face of mounting stresses from global climate change.

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Nutrient starvation impairs the trophic plasticity of reef‐building corals under ocean warming

Cited by 38 publications

References 65 publications

Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea

Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea

Peer Review #1 of "Nitrogen eutrophication particularly promotes turf algae in coral reefs of the central Red Sea (v0.1)"

Nitrogen pollution interacts with heat stress to increase coral bleaching across the seascape

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