Abstract
The long-spined sea urchin Diadema antillarum was once an abundant reef grazing herbivore throughout the Caribbean. During the early 1980s, D. antillarum populations were reduced by > 93% due to an undescribed disease. This event resulted in a lack of functional reef herbivory and contributed to ongoing ecological shifts from hard coral towards macroalgae dominated reefs. Limited natural recovery has increased interest in a range of strategies for augmenting herbivory. An area of focus has been developing scalable ex situ methods for rearing D. antillarum from gametes. The ultimate use of such a tool would be exploring hatchery origin restocking strategies. Intensive ex situ aquaculture is a potentially viable, yet difficult, method for producing D. antillarum at scales necessary to facilitate restocking. Here we describe a purpose-built, novel recirculating aquaculture system and the broodstock management and larval culture process that has produced multiple D. antillarum cohorts, and which has the potential for practical application in a dedicated hatchery setting. Adult animals held in captivity can be induced to spawn year-round, with some evidence for annual and lunar periodicity. Fecundity and fertilization rates are both consistently very high, yet challenges persist in both late stage larval development and early post-settlement survival. Initial success was realized with production of 100 juvenile D. antillarum from ~ 1200 competent larvae. While the system we describe requires a significant level of investment and technical expertise, this work advances D. antillarum culture efforts in potential future hatchery settings and improves the viability of scalable ex situ production for population enhancement.
Highlights
Coral reef ecosystems are declining worldwide at alarming rates due to a variety of additive local and global environmental threats including coastal pollution, disease, climate change, and the loss of h erbivores[1,2,3]
In 1983–1984, D. antillarum populations were reduced by 93–100% throughout their native range following the spread of an undescribed disease[33,34,35,36,37,38,39]
Natural recovery has been extremely limited throughout most historical geographic ranges, with reported population densities averaging fewer than 0.3 individuals m−2 31
Summary
Coral reef ecosystems are declining worldwide at alarming rates due to a variety of additive local and global environmental threats including coastal pollution, disease, climate change, and the loss of h erbivores[1,2,3]. Marine conservation paradigms, which have traditionally focused on regulating human behavior to protect ecosystems and promote natural recovery (e.g. marine protected areas, catch limits and moratoriums, direct and non-point source pollution restrictions), are rapidly expanding to include restoration strategies involving direct intervention[4,9,10] This expansion is evident in the Caribbean and Western-Atlantic, where unprecedented declines and lack of natural recovery of key reef-building corals[2,11,12] have driven the rapid growth of propagation and restoration programs[13,14,15,16,17]. Coral gardening should exist within a larger restoration framework that aims to reestablish functional natural reef structure and biodiversity via a multi-niche ecological approach Key to this ecological approach in the Caribbean and Western-Atlantic is the re-establishment of functional reef herbivory via recovery of long-spined sea urchin, Diadema antillarum, populations. While D. antillarum has been cultured s uccessfully[48,49,50], a lengthy and challenging larval development process, paucity of established culture methods, and lack of Scientific Reports | (2021) 11:11244 |
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