Coral micro-fragmentation assays for optimizing active reef restoration efforts

Abstract

The global decline of coral reefs has driven considerable interest in active coral restoration. Despite their importance and dominance on mature reefs, relatively few coral restoration projects use slower growth forms like massive and encrusting coral species. Micro-fragmentation can increase coral cover by orders of magnitude faster than natural growth, which now allows cultivation of slow growing massive forms and shows promise and flexibility for active reef restoration. However, the major causes of variation in growth and survival of outplanted colonies remain poorly understood. Here, we report simple outplanting assays to aid in active reef restoration of slower growing species and increase the likelihood of restoration success. We used two different micro-fragmentation assays. Pyramid assays were used to examine variation associated with fragment size (ranging from ≈1–9 cm2), nursery residence time (for both in-situ and ex-situ nurseries), and 2D vs. 3D measurements of growth. Block assays were used to examine spatial variation among individual performance at outplanting sites in the field. We found 2D and 3D measurements correlated well, so measured survivorship and growth using top-down planar images for two of the main Hawaiian reef building corals, the plating Montipora capitata and the massive Porites compressa. Pyramid assays housed and outplanted from the in-situ nursery showed no effect of residence time or size on overall survivorship or growth for either species. Results from the ex-situ nursery, however, varied by species, with P. compressa again showing no effect of nursery residence time or size on survivorship or growth. In contrast, nursery culture resulted in improved survivorship of small M. capitata fragments, but net growth showed a weak positive effect of nursery time for medium fragments. Small fragments still suffered higher mortality than either medium or large fragments. Due to their lower mortality, medium fragments (≈3 cm2) appear to be the best compromise between growth and survivorship for outplanting. Likewise, given weak positive gains relative to the investment, our results suggest that it could be more cost-effective to simply outplant medium fragments as soon as possible, without intermediate culture in a nursery. Furthermore, the block assay revealed significant differences in survivorship and growth among sites for individuals of both species, emphasizing the importance of considering spatial variation in coral survival and growth following outplanting. These results highlight the value of using short-term micro-fragmentation assays prior to outplanting to assess size, and location specific performance, optimizing the efficiency of active reef restoration activities and maximizing the probability of success for active coral restoration projects.

Deep-Sea Sponges and Corals off the Western Coast of Florida—Intracellular Mechanisms of Action of Bioactive Compounds and Technological Advances Supporting the Drug Discovery Pipeline

“…In situ Mariculture: In situ nurseries (i.e., sea-based cultures located in the natural habitat of the marine invertebrate) are sustainable methods for coral preservation and culturing to support future research [1,153], with comparatively lower maintenance and equipment costs [153]. In this cultivation approach, explants of sponges are placed on man-made substrates, such as glue, wood, cages, or rope [146,154], and then returned to their natural environment.…”

“…In this cultivation approach, explants of sponges are placed on man-made substrates, such as glue, wood, cages, or rope [146,154], and then returned to their natural environment. However, careful planning is needed to minimize the organisms' sensitivity to environmental conditions, including sedimentation, temperature, salinity, and pH [153,[155][156][157], to optimize their growth. Altogether, whether or not cultivation is successful is dependent on the optimal environmental conditions since it is well established that environmental stressors (e.g., predators, fouling, diseases, inclement weather, and climate change leading to bleaching events) [146,[158][159][160][161] can negatively affect growth and survivability.…”

“…Altogether, whether or not cultivation is successful is dependent on the optimal environmental conditions since it is well established that environmental stressors (e.g., predators, fouling, diseases, inclement weather, and climate change leading to bleaching events) [146,[158][159][160][161] can negatively affect growth and survivability. The inability to appropriately regulate such environmental parameters in the mariculture system has been shown to negatively affect the coral growth rate [153]. With regard to the sponge-symbiont populations, changes in temperature [159,162], heavy metal exposure [159,163], and diseases [159,164] (as well as movement from the natural habitat to containments [159,165,166]) can be detrimental to the health of marine invertebrates.…”

Tank fouling community enhances coral microfragment growth

“…In light of this reef crisis, scalable mechanisms to hasten the recovery of impacted reefs and the adaptation of corals to global stressors have been proposed ( National Academies of Sciences E and Medicine, 2019 ). However, focusing on in situ coral propagation strategies alone may be inadequate to meet this challenge, whereas land-based nurseries may significantly augment these restoration needs ( Knapp et al, 2022 ; O’Neil, 2015 ).…”

“…Recent studies with land-based culture techniques have led to increased growth and survival of juvenile coral ( Forsman et al, 2015 ; Hagedorn et al, 2021 ; Page, Muller & Vaughan, 2018 ), and have been proposed to augment in situ processes via large-scale restoration projects such as Mission: Iconic Reefs in Florida (USA) and the Reef Restoration and Adaptation Program in Australia. Despite these successes, outcomes between facilities are often variable due in large part to differing coral culture conditions ( Hagedorn et al, 2021 ; Knapp et al, 2022 ). This variable performance will greatly impact the utility and scale of land-based culture efforts if prolific, replicable, and transferrable techniques cannot be identified and implemented.…”