Insights from extreme coral reefs in a changing world

Abstract

Coral reefs are one of the most biodiverse and economically important ecosystems in the world, but they are rapidly degrading due to the effects of global climate change and local anthropogenic stressors. Reef scientists are increasingly studying coral reefs that occur in marginal and extreme environments to understand how organisms respond to, and cope with, environmental stress, and to gain insight into how reef organisms may acclimate or adapt to future environmental change. To date, there have been more than 860 publications describing the biology and/or abiotic conditions of marginal and extreme reef environments, most of which were published within the past decade. These include systems characterized by unusually high, low, and/or variable temperatures (intertidal, lagoonal, high-latitude areas, and shallow seas), turbid or urban environments, acidified habitats, and mesophotic depth, and focus on reefs geographically spread throughout most of the tropics. The papers in this special issue of Coral Reefs, entitled Coral Reefs in a Changing World: Insights from Extremes, build on the growing body of literature on these unique and important ecosystems, providing a deeper understanding of the patterns and processes governing life in marginal reef systems, and the implications that these insights may have for the future of tropical coral reefs in our rapidly changing world.

Light Limitation and Depth-Variable Sedimentation Drives Vertical Reef Compression on Turbid Coral Reefs

“…Deeper reef slope sites experienced very low light or "twilight" conditions (≤0.8 DLI) (Jones et al, 2015) on 31% of days at Kusu and 91% of days at Hantu. These data highlight the marginal, and fluctuating, conditions on turbid reefs that are distinct from clearwater reefs (Burt et al, 2020), as well as the complexities of establishing relevant baseline environmental data to characterize these systems. Light levels were consistent with other turbid reef environments, where data is available (Macdonald, 2015;Morgan et al, 2017;Chow et al, 2019;Loiola et al, 2019), but we found substantial differences in irradiance levels between reefs of close proximity (∼12 km) and a similar distance offshore (∼5 km).…”

“…Turbid coral reefs are well-adapted to inhabit areas of naturally high turbidity and low light (e.g., , and exhibit a tolerance and morphological plasticity to fluctuating abiotic conditions, such as sedimentation, eutrophication, temperature, and light (Anthony et al, 2005;Goodkin et al, 2011;Guest et al, 2012;Morgan et al, 2017). These marginal conditions for coral growth may afford turbid reefs a degree of protection from global climate-related disturbance events (e.g., prolonged ocean warming), as the shading effect of the overlying seawater turbidity can reduce the additive stress of solar irradiance on corals (Morgan et al, 2017;Burt et al, 2020). However, turbid coral reefs remain susceptible to increasing localized inputs from human activities (e.g., seafloor dredging) that may push environmental conditions beyond the threshold for coral growth (Erftemeijer et al, 2012;de Soares, 2020).…”

Symbiont shuffling across environmental gradients aligns with changes in carbon uptake and translocation in the reef-building coral Pocillopora acuta

“…Our work builds on the growing body of evidence (e.g. Camp et al 2018;Morikawa and Palumbi 2019;Burt et al 2020) that corals from extreme environments, including mangrove lagoons, have the potential to act as important stocks of stress-hardened corals. However, our findings highlight costs associated with survival into extreme environments, specifically lower quantities of Ci uptake by Symbiodiniaceae and organic carbon translocated to their coral host, P. acuta.…”

“…Reef-building corals can thrive under unexpected suboptimal conditions, providing unique opportunities to identify the physiological trade-offs underpinning their stress tolerance (Palumbi et al 2014;Camp et al 2018;Burt et al 2020). Such extreme environments include: low light availability (mesophotic (Baird et al 2018) or turbid (Suggett et al 2012a; Sully and van Woesik 2020)), warmer waters (e.g.…”

Study of Sea Surface Temperature (SST), Does It Affect Coral Reefs?

“…contribution of coral bleaching and disease because we found a higher positive anomaly and better condition of coral prevalence in the Wakatobi compared with the condition in the BNP. There are some other factors besides temperature that contribute to coral bleaching and disease incidence, such as water quality, competition, predator, and human activities Burt et al (2020) even with future global climate change, coral reefs will be able to adapt to disturbances. Other factors that greatly affect the resilience process are the acclimatization process, intragenerational effects and the evolutionary pressure of the coral reefs itself (Drury, 2020).…”