Elevated Temperature and Allelopathy Impact Coral Recruitment

Abstract

As climate change continues to alter seawater temperature and chemistry on a global scale, coral reefs show multiple signs of degradation. One natural process that could facilitate the recovery of reef ecosystems is coral recruitment, which can be influenced by the benthic organisms in a local habitat. We experimentally tested both a global stressor (increased seawater temperature) and a local stressor (exposure to microcolin A, a natural product from a common marine benthic cyanobacterium) to determine how these stressors impacted coral larval sublethal stress, survival and settlement. Larvae of Porites astreoides had the same survival and settlement as the controls after exposure to increased temperature alone, but elevated temperature did cause oxidative stress. When exposed to natural concentrations of microcolin A, larval survival and settlement were significantly reduced. When larvae were exposed to these two stressors sequentially there was no interactive effect; but when exposed to both stressors simultaneously, there was a synergistic reduction in larval survival and an increase in oxidative stress more than in either stressor treatment alone. Increased seawater temperatures made larvae more susceptible to a concurrent local stressor disrupting a key process of coral reef recovery and resilience. These results highlight the importance of understanding how interactive stressors of varying spatial scales can impact coral demographics.

Recent advances in allelopathy for weed control: from knowledge to applications

“…This alkaloid is synthesized by marine benthic cyanobacteria and causes oxidative stress in coral when delivered in high‐temperature media. The allelopathic effect caused by an increase in water temperature can impact coral demography . The exudates of Oscillatoria sp., another cyanobacterium, contain a new complex alkaloid, portoamide A, which inhibits the growth of the microalga Chlorella vulgaris …”

“…The allelopathic effect caused by an increase in water temperature can impact coral demography. 170 The exudates of Oscillatoria sp., another cyanobacterium, contain a new complex alkaloid, portoamide A, which inhibits the growth of the microalga Chlorella vulgaris. 171 The modes of action of natural products with a nitrogen atom have been studied extensively in animal cells, owing to their pharmacological properties.…”

Reefs under Siege—the Rise, Putative Drivers, and Consequences of Benthic Cyanobacterial Mats

“…The presence of cyanobacterial mats also directly impairs coral recruitment which is an essential ecological process for reef recovery following disturbances (McClanahan et al, 2012). Recruitment success may be reduced by (i) coral larvae avoiding settling near to cyanobacteria due to negative settlement cues, or (ii) cyanobacteria killing newly settled corals (Kuffner and Paul, 2004;Ritson-Williams et al, 2016). Benthic cyanobacterial mats have been implicated in reducing the recruitment success of both broadcast spawning and brooding corals (Kuffner and Paul, 2004;Kuffner et al, 2006).…”

“…Similarly, in Curaçao, spawning takes place in September/October (Van Veghel, 1994), and mats are particularly prevalent in October/November (Brocke et al, 2015a) when the coral spat would be settling on the substrate. At this critical time, the effects of cyanotoxins on coral recruits are also strongly exacerbated by warmer temperatures (Ritson-Williams et al, 2016). Further studies into the temporal prevalence of mats together with information on coral spawning times are needed to assess the extent of this potential threat, as large-scale inhibition of coral recruitment by cyanobacterial mats could have severe implications for the replenishment of coral populations.…”

Developmental carry over effects of ocean warming and acidification in corals from a potential climate refugium, Gulf of Aqaba

“…Typically ( present study included), coral planulae are pooled from multiple parental genotypes (Putnam and Gates, 2015;Ritson-Williams et al, 2016;Jiang et al, 2018;Bergman et al, 2018;Puisay et al, 2018). This not only removes the direct traceability of parental origin and therefore colony condition, but also may result in significant cohort differences with time or treatment simply because different parent colonies contribute more or less planulae at discrete sampling points.…”