Multiple trait approach to inform ecosystem service value of corals propagated for restoration on the Great Barrier Reef

Abstract

Coral propagation- and planting-based reef restoration practices are accelerating globally, yet short-term “success” continues to be measured as broad metrics of coral survival and growth, even though goals are often centred on recovering broad ecosystem service values. As such, how restoration activities may impact healthy reef functioning remains uncertain. For example, trade-offs in resource acquisition and partitioning that potentially regulate growth vs survival may yield very different outcomes towards factors governing reef biogeochemical cycles. Here we considered a proof-of-concept “multi-trait” approach to capture how a broader range of functional traits reflect the expression of growth and survival for a key coral species (Acropora cf. hyacinthus) — impacted by recent mass bleaching events — propagated for restoration activities on the Great Barrier Reef (GBR), Australia. We examined a diverse array of bio-physical, bio-chemical, and skeletal traits (n = 91 traits) for wild (donor) colonies and their nursery-derived fragments from a 12-month growth period (Opal Reef, northern GBR). Nursery corals grew 20-25 times faster than their donor (wild) colonies, but both exhibited similar survivorship. Faster growth within nurseries was accompanied by more pigmented colonies (darker-coloured and with more symbionts), and higher photosynthesis, respiration, and calcification rates. However, despite these metabolic changes, biogeochemical properties of the nursery and reef corals (carbohydrates, lipids, proteins, elemental stoichiometry, and skeletal properties) remained largely the same after 12 months, suggesting the bio-energetic value to trophic transfer as well as the structural rigour of corals was unaltered by nursery propagation. Thus, a “multi-trait” approach enables more informed evaluation as to how propagation activities impact diverse ecosystem service values, highlighting the immense importance of this knowledge in choosing coral individuals for restoration. Our example provides confidence to practitioners that key ecosystem service attributes of native corals are largely retained through an intermediate nursery growth phase that can accelerate coral biomass gains.