Coral growth, survivorship and return-on-effort within nurseries at high-value sites on the Great Barrier Reef

Abstract

Coral reefs are deteriorating worldwide prompting reef managers and stakeholders to increasingly explore new management tools. Following back-to-back bleaching in 2016/2017, multi-taxa coral nurseries were established in 2018 for the first time on the Great Barrier Reef (GBR) to aid reef maintenance and restoration at a “high-value” location–Opal Reef–frequented by the tourism industry. Various coral species (n = 11) were propagated within shallow water (ca. 4-7m) platforms installed across two sites characterised by differing environmental exposure–one adjacent to a deep-water channel (Blue Lagoon) and one that was relatively sheltered (RayBan). Growth rates of coral fragments placed onto nurseries were highly variable across taxa but generally higher at Blue Lagoon (2.1–10.8 cm2 month-1 over 12 months) compared to RayBan (0.6–6.6 cm2 month-1 over 9 months). Growth at Blue Lagoon was largely independent of season, except for Acropora tenuis and Acropora hyacinthus, where growth rates were 15–20% higher for December 2018-July 2019 (“warm season”) compared to August-December 2018 (“cool season”). Survivorship across all 2,536 nursery fragments was ca. 80–100%, with some species exhibiting higher survivorship at Blue Lagoon (Acropora loripes, Porites cylindrica) and others at RayBan (A. hyacinthus, Montipora hispida). Parallel measurements of growth and survivorship were used to determine relative return-on-effort (RRE) scores as an integrated metric of “success” accounting for life history trade-offs, complementing the mutually exclusive assessment of growth or survivorship. RRE scores within sites (across species) were largely driven by growth, whereas RRE scores between sites were largely driven by survivorship. The initial nursery phase of coral propagation therefore appears useful to supplement coral material naturally available for stewardship of frequently visited Great Barrier Reef tourism (high-value) sites, but further assessment is needed to evaluate how well the growth rates and survival for nursery grown corals translate once material is outplanted.

Toward bio‐optical phenotyping of reef‐forming corals using Light‐Induced FluorescenceTransient‐FastRepetition Rate fluorometry

“…To further assess the range in phenotypic signatures in corals, several species were collected at Opal Reef, on the northern GBR (16°13′S 145°53.5′; 24.7 km 2 ), at sites “RayBan,” “Blue Lagoon,” and “Mojo,” where coral nurseries and out‐planting have been underway since 2018 (Howlett et al 2021). As with other reef sites of the GBR, plating (tabular) Acroporid corals at Opal Reef were particularly impacted by the 2016/2017 back‐to‐back mass coral bleaching events (Hoogenboom et al 2017; Hughes et al 2017), and so represent priority species for nursery‐based site rehabilitation (e.g., Acropora cf.…”

“…As with other reef sites of the GBR, plating (tabular) Acroporid corals at Opal Reef were particularly impacted by the 2016/2017 back‐to‐back mass coral bleaching events (Hoogenboom et al 2017; Hughes et al 2017), and so represent priority species for nursery‐based site rehabilitation (e.g., Acropora cf. hyacinthus ; Howlett et al 2021), and therefore the focus to examine for intraspecies phenotypes. Sites of Opal Reef that were less impacted by recent heat waves are characterized by many plating colonies of Acropora across all topographies, with other taxa more topographically restricted (e.g., Echinopora lamellosa and Pocillopora verrucosa , which predominantly grow on cryptic or exposed reef topography, respectively) (John Edmondson, David Suggett, Emma Camp pers.…”

“…We recently established the Great Barrier Reef's (GBR) first multispecies coral nursery and intensive mass out‐planting practices (Suggett et al 2020; Howlett et al 2021) to aid maintenance and rehabilitation of “high‐value” tourism reef sites. To date, selection of coral colonies—as well as “fragments of opportunity” ( see Suggett et al 2020)—has been at random from the neighboring reef site, adhering to permitting criteria of coral species population density and colony size.…”

Horizon scan of rapidly advancing coral restoration approaches for 21st century reef management

“…Adult coral is commonly propagated asexually using in situ nurseries as well as land-based aquaria [8] (Figures 1 and 2). In situ nursery practices have advanced by tailoring species choice, location to optimise growth, and/or design to improve cost-effectiveness [79][80][81], enabling both long term housing of parental stocks as well as short term 'grow out' of material (e.g. [82]).…”

Revealing the Systematic Nature of Coral Attachment to Reef Substrates

“…The paucity of observations of coral attachment through the initial stages of contact obscures the systematic nature by which the coral fragment changes from the time of substrate contact; therefore, the tissue and skeletal processes and factors that promote or inhibit rapid and robust attachment are absent from the literature. If aquaculture and outplanting are to improve return on effort for targeted sites 42,43 and be viable for large-scale interventions for coral reef restoration, it is vital to assess coral responses to external environmental factors with appropriate spatial and temporal resolution.…”