Effects of sediment deposition on the seaweed Sargassum on a fringing coral reef

Umar, M. J.; McCook, Laurence; Price, Ian R.

doi:10.1007/s003380050111

Cited by 92 publications

(53 citation statements)

References 17 publications

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“…The increased benthic sediment loads may be the explanation. Such increases have the potential to prevent the development of macroalgae (Airoldi and Virgilio 1998, Umar et al 1998, Goatley and Bellwood 2013 and by suppressing herbivory (Bellwood and Fulton 2008, Clausing et al 2014, Gordon et al 2016) these sediments promote the development of long algal turfs (Goatley and Bellwood 2013). If this is the case, these LSATs now found on the reef crest in Pioneer Bay could represent a new and relatively stable state (Goatley and Bellwood 2013;cf.…”

Section: Subtle Signs Of Ecosystem Degradation: Browsers and Macroalgaementioning

confidence: 99%

Sediments and herbivory as sensitive indicators of coral reef degradation

Goatley¹,

Bonaldo²,

Fox³

et al. 2016

E&S

107

142

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ABSTRACT. Around the world, the decreasing health of coral reef ecosystems has highlighted the need to better understand the processes of reef degradation. The development of more sensitive tools, which complement traditional methods of monitoring coral reefs, may reveal earlier signs of degradation and provide an opportunity for pre-emptive responses. We identify new, sensitive metrics of ecosystem processes and benthic composition that allow us to quantify subtle, yet destabilizing, changes in the ecosystem state of an inshore coral reef on the Great Barrier Reef. Following severe climatic disturbances over the period 2011-2012, the herbivorous reef fish community of the reef did not change in terms of biomass or functional groups present. However, fish-based ecosystem processes showed marked changes, with grazing by herbivorous fishes declining by over 90%. On the benthos, algal turf lengths in the epilithic algal matrix increased more than 50% while benthic sediment loads increased 37-fold. The profound changes in processes, despite no visible change in ecosystem state, i.e., no shift to macroalgal dominance, suggest that although the reef has not undergone a visible regime-shift, the ecosystem is highly unstable, and may sit on an ecological knife-edge. Sensitive, process-based metrics of ecosystem state, such as grazing or browsing rates thus appear to be effective in detecting subtle signs of degradation and may be critical in identifying ecosystems at risk for the future.

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Section: Subtle Signs Of Ecosystem Degradation: Browsers and Macroalgaementioning

confidence: 99%

Sediments and herbivory as sensitive indicators of coral reef degradation

Goatley¹,

Bonaldo²,

Fox³

et al. 2016

E&S

107

142

View full text Add to dashboard Cite

show abstract

“…These factors are frequently associated with human population densities, and few governments will establish marine protected areas in polluted waters or allow marine scientists to artificially pollute protected areas. However, there are studies that suggest that the response of coral reefs to a combination of these factors may be different from their response to these factors in isolation (e.g., McCook 1996, McClanahan and Obura 1997, Umar et al 1998). …”

Section: Synergistic Stressorsmentioning

confidence: 99%

Ecological States and the Resilience of Coral Reefs

McClanahan¹,

Polunin²,

Done³

2002

175

116

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ABSTRACT. We review the evidence for multiple ecological states and the factors that create ecological resilience in coral reef ecosystems. There are natural differences among benthic communities along gradients of water temperature, light, nutrients, and organic matter associated with upwelling-downwelling and onshoreoffshore systems. Along gradients from oligotrophy to eutrophy, plant-animal symbioses tend to decrease, and the abundance of algae and heterotrophic suspension feeders and the ratio of organic to inorganic carbon production tend to increase. Human influences such as fishing, increased organic matter and nutrients, sediments, warm water, and transportation of xenobiotics and diseases are common causes of a large number of recently reported ecological shifts. It is often the interaction of persistent and multiple synergistic disturbances that causes permanent ecological transitions, rather than the succession of individual short-term disturbances. For example, fishing can remove top-level predators, resulting in the ecological release of prey such as sea urchins and coraleating invertebrates. When sea urchins are not common because of unsuitable habitat, recruitment limitations, and diseases, and when overfishing removes herbivorous fish, frondose brown algae can dominate. Terrigenous sediments carried onto reefs as a result of increased soil erosion largely promote the dominance of turf or articulated green algae. Elevated nutrients and organic matter can increase internal eroders of reef substratum and a mixture of filamentous algae. Local conservation actions that attempt to reduce fishing and terrestrial influences promote the high production of inorganic carbon that is necessary for reef growth. However, global climate change threatens to undermine such actions because of increased bleaching and mortality caused by warm-water anomalies, weakened coral skeletons caused by reduced aragonite availability in reef waters, and increased incidence of diseases in coral reef species. Consequently, many coral reefs, including those that are heavily managed, have experienced net losses in accumulated inorganic carbon in recent decades and appear likely to continue this trend in coming decades. Reefs urgently need to be managed with a view to strengthening their resilience to the increased frequency and intensity of these pressures. Ecological targets must include the restoration or maintenance of species diversity, keystone species, spatial heterogeneity, refugia, and connectivity. Achieving these goals will require unprecedented cooperative synergy between human organizations at all political levels, from intergovernmental to local.

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“…Macroalgal assemblage inhabiting sedimentinXuenced environments may also be favorably related to other factors correlated with sediments, e.g. nutrient availability (Umar et al 1998). Changes in salinity due to freshwater input can, however, impose other adverse physiological eVect.…”

Section: Discussionmentioning

confidence: 99%

Transient sediment load on blades of Arctic Saccharina latissima can mitigate UV radiation effect on photosynthesis

2008

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We studied the short-term impact of sediment load on the photosynthetic performance of Saccharina latissima sporophytes exposed to ultraviolet radiation (UVR). The algae were collected from diVerent sedimentinXuenced environments in Svalbard in August 2007. Initial optimum quantum yield (F v /F m ) of sediment-covered sporophytes was signiWcantly higher compared to sediment-free sporophytes. Experimental sediment coating on blade discs had a photoprotective function by screening out 92% of the weighted UV-B (UV ery ) treatment. No UVRinduced photoinhibition was observed in sediment-coated blade discs while sediment removal caused a reduction in F v /F m not only after 12-h UVR exposure but also after 6-h recovery in low white light compared to the initial value. Thus, sediment coating has a short-term functional signiWcance in mitigating the negative eVect of UVR on photosynthesis of an important kelp species and set a baseline for further studies.

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Effects of sediment deposition on the seaweed Sargassum on a fringing coral reef

Cited by 92 publications

References 17 publications

Sediments and herbivory as sensitive indicators of coral reef degradation

Sediments and herbivory as sensitive indicators of coral reef degradation

Ecological States and the Resilience of Coral Reefs

Transient sediment load on blades of Arctic Saccharina latissima can mitigate UV radiation effect on photosynthesis

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