Event Title

Twilight Reefs May Usher in a New Dawn for Depauperate, Shallow Reefs

Location

Guy Harvey Oceanographic Center Facility

Start

5-19-2016 3:45 PM

End

5-19-2016 4:15 PM

Description

As shallow reefs continue to decline, scientists are searching for the key to their persistence; as it turns out, they may just need to look a little deeper. Healthy and stable mesophotic coral reef communities are being discovered around the world and inspired the Deep Reef Refugia Hypothesis (DRRH), which suggests that mesophotic reefs are acting as a refuge for depauperate shallow communities by bolstering populations and enhancing sexual reproduction. However, several assumptions of this hypothesis remain untested: (1) vertical and horizontal spatial isolation has not led to reproductively isolated of shallow and deep conspecifics, and (2) larvae generated from deep corals are attracted to and survive in shallow coral reef habitats. This project was conducted on the barrier reef of Belize where the reefs grow along the vertical wall and shallow and mesophotic coral populations are separated by limited horizontal distance. Although 8 microsatellite markers demonstrated no population structure between shallow and mesophotic O. franksi, fine scale morphometric analysis using 25 landmarks revealed clear differences between mesophotic and shallow colonies. Gametes from Orbicella franksi inhabiting the shallow (14-20m) and the upper mesophotic (27-32m) were crossed and found to be compatible. Larvae produced in reciprocal crosses between deep and shallow parents developed normally and were equally viable as larvae obtained from intradepth crosses. While larvae from shallow parents did not exhibit any settlement preference between tiles conditioned at shallow depths versus in the mesophotic zone, there was significantly more mesophotic larvae that preferred to settle on shallow conditioned tiles. Yet, no difference was seen in the post-settlement survival between depths. These results suggest a close coupling between shallow and mesophotic reefs through gamete and larval export that likely play an increasingly vital role in shallow reef persistence and recovery.

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May 19th, 3:45 PM May 19th, 4:15 PM

Twilight Reefs May Usher in a New Dawn for Depauperate, Shallow Reefs

Guy Harvey Oceanographic Center Facility

As shallow reefs continue to decline, scientists are searching for the key to their persistence; as it turns out, they may just need to look a little deeper. Healthy and stable mesophotic coral reef communities are being discovered around the world and inspired the Deep Reef Refugia Hypothesis (DRRH), which suggests that mesophotic reefs are acting as a refuge for depauperate shallow communities by bolstering populations and enhancing sexual reproduction. However, several assumptions of this hypothesis remain untested: (1) vertical and horizontal spatial isolation has not led to reproductively isolated of shallow and deep conspecifics, and (2) larvae generated from deep corals are attracted to and survive in shallow coral reef habitats. This project was conducted on the barrier reef of Belize where the reefs grow along the vertical wall and shallow and mesophotic coral populations are separated by limited horizontal distance. Although 8 microsatellite markers demonstrated no population structure between shallow and mesophotic O. franksi, fine scale morphometric analysis using 25 landmarks revealed clear differences between mesophotic and shallow colonies. Gametes from Orbicella franksi inhabiting the shallow (14-20m) and the upper mesophotic (27-32m) were crossed and found to be compatible. Larvae produced in reciprocal crosses between deep and shallow parents developed normally and were equally viable as larvae obtained from intradepth crosses. While larvae from shallow parents did not exhibit any settlement preference between tiles conditioned at shallow depths versus in the mesophotic zone, there was significantly more mesophotic larvae that preferred to settle on shallow conditioned tiles. Yet, no difference was seen in the post-settlement survival between depths. These results suggest a close coupling between shallow and mesophotic reefs through gamete and larval export that likely play an increasingly vital role in shallow reef persistence and recovery.