effective-techniques-for-feeding-ex-situ-culture-brooding

Effective Techniques for the Feeding and <em>Ex Situ</em> Culture of a Brooding Scleractinian Coral, <em>Pocillopora acuta</em>

Climate change is affecting the survival, growth, and recruitment of corals globally, with large-scale shifts in abundance and community composition ...

National Museum of Marine Biology & Aquarium

Corals are comprised of a coral host and associated microbes whose interactions are mediated by the coral innate immune system. The diversity of immune factors identified in the Pocillopora damicornis genome suggests that immunity is linked to maintaining microbial symbioses while also being able to detect pathogens. However, it is unclear which immune factors respond to specific microbe-associated molecular patterns and how these immune reactions simultaneously affect coral-associated bacteria. To investigate this, fragments of P. damicornis and P. acuta colonies from Taiwan were subjected to lipopolysaccharide (LPS) treatment to stimulate immune responses and measure bacteria community shifts. RNA-seq revealed genotype-specific immune responses to LPS involving the upregulation of immune receptors, transcription factors, and pore-forming toxins. Bacteria 16S sequencing revealed significantly different bacteria communities between coral genotypes but no differences in bacteria communities were caused by LPS. Our findings confirm that Pocillopora corals activate conserved immune factors in response to LPS and identify transcription factors coordinating Pocillopora corals' immune responses. Additionally, the strong effect of coral genotype on gene expression and bacteria communities highlights the importance of coral genotype in the investigation of coral host-microbe interactions.

Lipopolysaccharide treatment stimulates Pocillopora coral genotype-specific immune responses but does not alter coral-associated bacteria communities.

Ocean warming induced by climate change is the greatest threat to the persistence of coral reefs globally. Given the current rate of ocean warming, there may not be sufficient time for natural acclimation or adaptation by corals. This urgency has led to the exploration of active management techniques aimed at enhancing thermal tolerance in corals. Here, we test the capacity for transgenerational acclimation in the reef-building coral  as a means of increasing offspring performance in warmer waters. We exposed coral colonies from a reef influenced by intermittent upwelling and constant warm-water effluent from a nuclear power plant to temperatures that matched (26 °C) or exceeded (29.5 °C) season-specific mean temperatures for three reproductive cycles; offspring were allowed to settle and grow at both temperatures. Heated colonies reproduced significantly earlier in the lunar cycle and produced fewer and smaller planulae. Recruitment was lower at the heated recruitment temperature regardless of parent treatment. Recruit survival did not differ based on parent or recruitment temperature. Recruits from heated parents were smaller and had lower maximum quantum yield (Fv/Fm), a measurement of symbiont photochemical performance. We found no direct evidence that thermal conditioning of adult  corals improves offspring performance in warmer water; however, chronic exposure of parent colonies to warmer temperatures at the source reef site may have limited transgenerational acclimation capacity. The extent to which coral response to this active management approach might vary across species and sites remains unclear and merits further investigation.

Effects of thermal conditioning on the performance of  adult coral colonies and their offspring.

Ocean warming and marine heatwaves induced by climate change are impacting coral reefs globally, leading to coral bleaching and mortality. Yet, coral resistance and resilience to warming are not uniform across reef sites and corals can show inter- and intraspecific variability. To understand changes in coral health and to elucidate mechanisms of coral thermal tolerance, baseline data on the dynamics of coral holobiont performance under non-stressed conditions are needed. We monitored the seasonal dynamics of algal symbionts (family Symbiodiniaceae) hosted by corals from a chronically warmed and thermally variable reef compared to a thermally stable reef in southern Taiwan over 15 months. We assessed the genera and photochemical efficiency of Symbiodiniaceae in three coral species:  and . Both  and  were present in all coral species at both reef sites across all seasons, but general trends in their detection (based on qPCR cycle) varied between sites and among species. Photochemical efficiency (, maximum quantum yield; ) was relatively similar between reef sites but differed consistently among species; no clear evidence of seasonal trends in  was found. Quantifying natural Symbiodiniaceae dynamics can help facilitate a more comprehensive interpretation of thermal tolerance response as well as plasticity potential of the coral holobiont.

Article	Year
Lipopolysaccharide treatment stimulates Pocillopora coral genotype-specific immune responses but does not alter coral-associated bacteria communities. Developmental and comparative immunology\| PubMed ID: 32348787	2020
Effects of thermal conditioning on the performance of adult coral colonies and their offspring. Coral reefs (Online)\| PubMed ID: 34720373	2021
Baseline dynamics of Symbiodiniaceae genera and photochemical efficiency in corals from reefs with different thermal histories. PeerJ\| PubMed ID: 37283898	2023

Crystal J. McRae

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