Atmospheric Nitrogen Deposition Increases the Possibility of Macroalgal Dominance on Remote Coral Reefs

Chen, Xiaoyan; Yu, Kefu; Huang, Xueyong; Wang, Yinghui; Liao, Zhiheng; Zhang, Ruijie; Yu, Xiaopeng; Wang, Jikun; Wang, Wenhuan; Tao, Shichen; Zhang, Huiling

doi:10.1029/2019jg005074

Cited by 26 publications

(14 citation statements)

References 54 publications

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“…Hence, our results may reveal the dynamics of marine primary productivity and phytoplankton variability, highlighting anthropogenic P input as an important stress on remote and oligotrophic coral reefs. We also concluded that P could stimulate long‐term gross primary productivity in these coral reefs, in addition to the “atmospheric nitrogen hypothesis” proposed by Chen, Yu, et al (2019).…”

Section: Discussionsupporting

confidence: 75%

“…However, in light of the rich source of nitrogen for coral islands (D'Elia, 1988) and strong P limitations on Yongxing Island (Chen et al, 2016), we concluded that additional input of P due to guano exploitation should lead to increased marine primary productivity, as shown by coral δ 13 C. It is noteworthy, however, that sudden increases in P in seawater that exceed the threshold that coral reef systems can withstand could lead to the degeneration of coral reef ecosystems due to rapid and unchecked algal growth (Dunn et al, 2012; Ke et al, 2018; Martinez‐Escobar & Mallela, 2019). Field surveys of the Yongxing Islands, which were the major site of phosphate extraction, demonstrate that the reef hosts a much greater macroalgal cover than the other islands (Chen, Yu, et al, 2019). Furthermore, live coral cover, which is inversely correlated with macroalgal/turf cover (Guo et al, 2019), has decreased by nearly 20% on Yongxing Island over the past 30 years (Yu, 2012).…”

Section: Discussionmentioning

confidence: 99%

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Porites Coral on a Remote Reef Reveal Marine Phosphorus Biogeochemical Cycling Following Artificial Disturbance

Jiang

Yang

et al. 2020

JGR Oceans

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Excess anthropogenic phosphorus (P) supplied to marine systems, which may subsequently jeopardize ecosystem structure and function, has altered the P balance and quadrupled its flow. However, due to the diversity of P sources, the unpredictability and variability of human activities, and the absence of long‐term records, it remains uncertain how long the effects of excess P persist in aquatic ecosystems, and whether it stimulates gross primary productivity. In this study, we utilized geochemical proxies in coral skeletons from an atoll in the Xisha Islands of the South China Sea to reconstruct historical patterns of P in surface seawater. This atoll has remained in a natural state for an extended period of time, except for a short period of unambiguously documented guano extraction. Analyses of coral skeletons dating back to 1851 CE distinctly show that the P concentration in surface seawater increased abnormally in the 1960s. We deduced that guano extraction at that time led to an abrupt increase in the long‐term equilibrium of seawater P concentration. Subsequent P addition appeared to have continued for at least ~30 years after phosphorite exploitation ceased, and P showed a decay period that was longer than that of other elements. Similar temporal trends of coral P/Ca and δ13C indicated that elevated marine primary productivity was associated with increased P. Large inputs within a short period, as well as the continued influence of P over the long term, can serve as a natural ecological analog for coral reefs subject to nutrient contamination.

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Porites Coral on a Remote Reef Reveal Marine Phosphorus Biogeochemical Cycling Following Artificial Disturbance

Jiang

Yang

et al. 2020

JGR Oceans

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“…The Xisha Islands are rich in seabird populations (Xu et al, 2016), and nutrient subsidies from seabirds, therefore, may promote the growth of Halimeda. The most dominant herbivorous fish in the Xisha Islands seem to prefer turf algae over macroalgae (Chen et al, 2019). In contrast, Halimeda or other macroalgae species were rarely observed in reefs of the Nansha Islands, possibly because of the extremely low nutrient levels, high fish herbivory and lack of nutrient subsidies from seabirds, since there is no land for seabirds to nest on subtidal atoll reefs.…”

Section: Effective Regulation Of Environmental Factors Influencing mentioning

confidence: 96%

“…Evidence of nutrient subsidies from atmospheric nitrogen deposition and seabirds may help to explain this anomaly. Chen et al (2019) suggested that atmospheric nitrogen was the most likely potential source of nutrients for the promotion of macroalgal blooms in the Xisha Islands. In addition, nutrients from seabirds were found to promote the growth of Halimeda in the remote Chagos Archipelago of the central Indian Ocean (Benkwitt et al, 2019).…”

Section: Effective Regulation Of Environmental Factors Influencing mentioning

confidence: 99%

“…Live coral cover has declined by over 70% in the coastal reefs of the northern SCS over the last several decades (Liao et al, 2019;Yu et al, 2019;Zhao et al, 2012) as a consequence of coastal urbanization, coral harvesting, pollution, tourism, overfishing and destructive fishing (Hughes et al, 2013;Yu et al, 2019;Zhao et al, 2012). Similarly, live coral cover in the central SCS has declined from over 70% in the 1980s (Hughes et al, 2007) to 16% in 2015 (Chen et al, 2019), as a consequence of frequent human activities mainly overfishing, and destructive fishing, and recurrent natural events, such as coral bleaching, and outbreaks of crown-of-thorns starfish (Hughes et al, 2013; Li…”

Section: Introductionmentioning

confidence: 99%

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Spatial distribution of benthic algae in the South China Sea: Responses to gradually changing environmental factors and ecological impacts on coral communities

Liao

Chen

et al. 2021

Diversity and Distributions

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Aim: In this study, we investigated whether environmental factors can effectively control the spatial distribution of various benthic algae and examined the critical ecological impacts of algae on corals across the South China Sea (SCS). Relationships between benthic algae and environmental factors were assessed, and potential ecological impacts of algae on coral communities were evaluated across spatial scales.Location: A total of 104 sites at 12 coral reefs in four coral reef regions (CRRs) of the SCS (latitude range of 9-22° N).Taxa: Turf algae, macroalgae (including fleshy macroalgae and Halimeda), crustose coralline algae (CCA), coral and juvenile coral.Methods: Using diver-based surveys (2015-2018), we investigated four CRRs with different reef distance to mainland (RDM) across the SCS. We obtained field data on benthic algal composition and cover, coral cover and diversity, and juvenile coral density. We also measured and collected the environmental factors (including seawater environmental parameters and reef fish diversity). Results:The cover of turf algae and CCA gradually decreased and increased, respectively, with an increase in RDM, which had a strong relationship with the gradually changing environmental factors. Random forest models suggested that nutrients, reef fish diversity, seawater transparency and temperature were the most important factors for predicting turf algae and CCA cover. Linear regression analyses showed a significant relationship between the turf algae, macroalgae, and CCA covers, and juvenile coral density. Main conclusions:Our results showed that gradually changing environmental factors were correlated with the spatial distributions of turf algae and CCA. However, the natural biophysical relationships between macroalgae and environmental factors may be disrupted by turf algal overgrowth and nutrient subsidies. Increases in all benthic algal groups significantly impacted coral recruitment, highlighting the critical role of benthic algae in determining the recovery trajectory of the Indo-Pacific reefs that are threatened by human activities.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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A review of a decade of lessons from one of the world’s largest MPAs: conservation gains and key challenges

et al. 2020

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Given the recent trend towards establishing very large marine protected areas (MPAs) and the high potential of these to contribute to global conservation targets, we review outcomes of the last decade of marine conservation research in the British Indian Ocean Territory (BIOT), one of the largest MPAs in the world. The BIOT MPA consists of the atolls of the Chagos Archipelago, interspersed with, and surrounded by, deep oceanic waters. Islands around the atoll rims serve as nesting grounds for sea birds. Extensive and diverse shallow and mesophotic reef habitats provide essential habitat and feeding grounds for all marine life, and the absence of local human impacts may improve recovery after coral bleaching events. Census data have shown recent increases in the abundance of sea turtles, high numbers of nesting seabirds and high fish abundance, at least some of which is linked to the lack of recent harvesting. For example, across the archipelago the annual number of green turtle nests (Chelonia mydas) is ~20,500 and increasing and the number of seabirds is ~1 million. Animal tracking studies have shown that some taxa breed and/or forage consistently within the MPA (e.g. some reef fishes, elasmobranchs and seabirds), suggesting the MPA has the potential to provide long-term protection. In contrast, post-nesting green turtles travel up to 4000 km to distant foraging sites, so the protected beaches in the Chagos Archipelago provide a nesting sanctuary for individuals that forage across an ocean basin and several geopolitical borders. Surveys using divers and underwater video systems show high habitat diversity and abundant marine life on all trophic levels. For example, coral cover can be as high as 40-50%. Ecological studies are shedding light on how remote ecosystems function, connect to each other and respond to climate-driven stressors compared to other locations that are more locally impacted. However, important threats to this MPA have been identified, particularly global heating events, and Illegal, Unreported and Unregulated (IUU) fishing activity, which considerably impact both reef and pelagic fishes.

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Atmospheric Nitrogen Deposition Increases the Possibility of Macroalgal Dominance on Remote Coral Reefs

Cited by 26 publications

References 54 publications

Porites Coral on a Remote Reef Reveal Marine Phosphorus Biogeochemical Cycling Following Artificial Disturbance

Porites Coral on a Remote Reef Reveal Marine Phosphorus Biogeochemical Cycling Following Artificial Disturbance

Spatial distribution of benthic algae in the South China Sea: Responses to gradually changing environmental factors and ecological impacts on coral communities

A review of a decade of lessons from one of the world’s largest MPAs: conservation gains and key challenges

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