Plasticity of Porites astreoides Early Life History Stages Suggests Mesophotic Coral Ecosystems Act as Refugia in Bermuda

Abstract

As the devastating impacts of global climate change and local anthropogenic stressors on shallow-water coral reefs are expected to rise, mesophotic coral ecosystems have increasingly been regarded as potential lifeboats for coral survival, providing a source of propagules to replenish shallower reefs. Yet, there is still limited knowledge of the capacity for coral larvae to adjust to light intensities that change with depth. This study elucidates the mechanisms underlying plasticity during early life stages of the coral Porites astreoides that enable survival across broad depth gradients. We examined physiological and morphological variations in larvae from shallow (8–10 m) and mesophotic (45 m) reefs in Bermuda, and evaluated differences in survival, settlement patterns and size among recruits depending on light conditions using a reciprocal ex situ transplantation experiment. Larvae released from mesophotic adults were found to have significantly lower respiration rates and were significantly larger than those derived from shallow adults, indicating higher content of energetic resources and suggesting a greater dispersal potential for mesophotic larvae compared to their shallow counterparts. Additionally, larvae released from mesophotic adults experienced higher settlement success and larger initial spat size compared to larvae from shallow adults, demonstrating a potential connection between parental origin, offspring quality, and recruitment success. Although both shallow and mesophotic larvae exhibited the capacity to survive and settle under reciprocal light conditions, all larvae had higher survival under mesophotic light conditions regardless of parental origin, suggesting that conditions experienced under low light may enable longer larval life, further extending the dispersal period. These results indicate that larvae from mesophotic Porites astreoides colonies are likely capable of reseeding shallow reefs in Bermuda, thereby supporting the Deep Reef Refugia Hypothesis.

Light and photoacclimatization drive distinct differences between shallow and mesophotic coral communities

“…Recent work shows strong evidence that mesophotic coral species, including M. cavernosa and P. astreoides , play an influential role in maintaining populations of shallow reefs (Goodbody‐Gringley et al, 2021; Sturm et al, 2021). Understanding the fundamental drivers of ecology in mesophotic corals, as well as the physiological light parameters of individual species, increases our ability to predict their distribution and identify potential areas that may serve as refuges, thereby increasing the resilience of global coral reef ecosystems.…”

“…Historically, shallow reefs have experienced declines, whereas MCEs have had a relatively stable coral population over time (Bak et al, 2005). Thus, MCEs are often suggested to increase the resilience of coral reefs overall by acting as a refuge to shallow reefs (Bongaerts et al, 2010; Glynn, 1996; Goodbody‐Gringley et al, 2021; Sturm et al, 2021). The idea of MCEs as a refuge, however, has been questioned due to increased frequencies of disturbances and anthropogenic impacts at mesophotic depth (Rocha et al, 2018).…”

The Genome of the Mustard Hill Coral,Porites astreoides

“…These taxa are often able to grow and reproduce in a "weedy" fashion, and thus increase in relative abundance on the reef (Darling et al 2012). One such weedy coral species is the mustard hill coral, Porites astreoides (Lamarak, 1826), which is a ubiquitous shallow Western Atlantic coral that is present across large environmental clines from mesophotic depths of ~45m (Goodbody-Gringley et al 2021) to shallow mangrove environments (Lord et al 2021) and a latitudinal range from Brazil (Pereira et al 2017) to Bermuda (Dodge, Logan, and Antonius 1982). In contrast to other Caribbean corals, P. astreoides has increased in abundance in recent years, with high juvenile (Vermeij et al 2011) and adult (Green, Edmunds, and was not certified by peer review) is the author/funder.…”

The genome of the mustard hill coral, Porites astreoides

“…One such weedy coral species is the mustard hill coral, Porites astreoides (Lamarak, 1826). This is a ubiquitous shallow Western Atlantic coral present across large environmental clines from mesophotic depths of ∼45 m [ 8 ] to shallow mangrove environments [ 9 ] , and a latitudinal range from Brazil [ 10 ] to Bermuda [ 11 ] . In contrast to other Caribbean corals, P. astreoides has increased in abundance in recent years, with high juvenile [ 12 ] and adult [ 13 – 15 ] abundances, but smaller colony sizes [ 16 ] .…”

“…In contrast to other Caribbean corals, P. astreoides has increased in abundance in recent years, with high juvenile [ 12 ] and adult [ 13 – 15 ] abundances, but smaller colony sizes [ 16 ] . P. astreoides is considered a ‘weedy’ species’ as it is a hermaphroditic, brooding coral species with a prolonged planulation period [ 17 , 18 ] of pelagic larvae that exhibit high phenotypic plasticity [ 19 – 23 ] and high recruitment rates [ 8 , 21 ] . Additionally, larvae and juvenile life stages have been well studied under ocean acidification [ 24 , 25 ] and temperature stress conditions [ 22 , 26 – 29 ] owing to the ease of brooded larval collection.…”