Broadcast-spawning scleractinian corals undergo mass spawning annually, the timing of which is determined by a series of environmental and chemical cues. Flower Garden Banks reefs (FGB, NW Gulf of Mexico) have high coral cover compared to the rest of the Tropical Western Atlantic and exhibit highly synchronous coral spawning, although spawning observations have been largely limited to shallower depths (17–24 m). Using a remotely operated vehicle (ROV), we report observations of mesophotic (39–42 m) broadcast spawning of three major reef-building coral species at East FGB. We observed spawning of 20 Montastraea cavernosa colonies, an order of magnitude more than has been previously reported for this population at mesophotic depths. Spawning times of the three target species (M. cavernosa, Orbicella franksi, and Pseudodiploria strigosa) ranged from 45 min prior to sunset up to 1 h, 33 min after sunset, consistent with shallow conspecifics. We place these observations in the context of other spawning reports of the same species at the FGB and throughout the Tropical Western Atlantic. In addition, the ROV was directed to collect eight genetically unique fragments of gravid Orbicella faveolata and employed a novel gamete collection device designed to capture gametes from actively spawning colonies in situ. These data and collection techniques highlight the benefits of using ROV technology for coral-spawning research, particularly for mesophotic coral reef ecosystems, where gamete release occurs across time ranges exceeding limits imposed by recreational diving. Finally, our observations of overlap in the timing of spawning along the shallow to mesophotic continuum at the FGB suggest—at least for the corals monitored here—that the potential for cross fertilization across depths exists.

Depth range
39- 42 m

Mesophotic “mentions”
40 x (total of 5161 words)

Classification
* Presents original data
* Focused on 'mesophotic' depth range
* Focused on 'mesophotic coral ecosystem'

Fields
Reproduction

Focusgroups
Scleractinia (Hard Corals)

Locations
USA - Gulf of Mexico

Platforms
Remotely Operated Vehicle (ROV)