Abstract Summary
We demonstrated that assisted gene flow between genetically-distinct Caribbean coral populations, using cryopreserved sperm, could be a viable option to help restore coral reefs. We used frozen coral sperm from three genetically-distinct populations of the endangered coral Acropora palmata to fertilize A. palmata eggs collected in Curaçao, producing the first-ever pan-Caribbean coral crosses conducted in a laboratory. The frozen sperm that we used represented three genetically-distinct populations: Western Caribbean (Key Largo, FL), central or mixed Caribbean (Rincon, Puerto Rico) and Eastern Caribbean (Curacao). The Puerto Rico and Florida sperm samples, which had been frozen for up to 10 years, were sent to CARMABI Research Station in Curaçao from the USDA. The experimental crosses with fresh eggs consisted of four treatment groups: CUR (fresh sperm), CUR (frozen sperm), FL (frozen sperm), and PR (frozen sperm). All four categories of crosses were successful. Specifically, fertilization success ranged from 86% to 99% for CUR (fresh sperm), 32% to 88% for CUR (frozen sperm), 1% to 20% for FL (frozen sperm) and 0% to 24% for PR (frozen sperm). Embryos and larvae were reared at CARMABI in 1L polystyrene static bins and 10L conical rearing cones for up to 8 days post-fertilization. Then, thousands of swimming larvae were transported to The Florida Aquarium Center for Conservation and Mote Marine Laboratory for settlement and grow-out. Their respective settlement numbers were approximately 50% to 60%, producing over 10,000 settlers including over 3,500 settlers from CUR (frozen) sperm, 1,247 settlers from FL (frozen sperm), and 233 settlers from PR (frozen sperm). This is the largest living wildlife population ever created from cryopreserved sperm, demonstrating that cryopreservation can be an effective tool for assisted migration, assisted gene flow, and the preservation of genetic diversity to help restore and invigorate coral populations.
