Assessment of Mesophotic Coral Ecosystem Connectivity for Proposed Expansion of a Marine Sanctuary in the Northwest Gulf of Mexico: Larval Dynamics

Abstract

In coral reef ecosystems, mesophotic coral habitat ( >30 m to the end of the photic zone) are extensions of shallow reefs and contribute to the persistence of coral reef populations. In the North West Gulf of Mexico (NW GOM), the Flower Garden Banks National Marine Sanctuary (FGBNMS) is an isolated reef ecosystem comprising contiguous shallow and mesophotic reefs habitats on two central banks along the margin of the continental shelf. A future expansion of the sanctuary is proposed to include additional mesophotic banks and aims at building a network of protected areas in the NW GOM to ensure the persistence of the coral reef populations inhabiting the sanctuary. To evaluate the feasibility of this expansion and investigate the overall dynamics of coral species in the region, we studied the patterns of larval connectivity of Montastraea cavernosa, a common depth generalist coral species, using a larval dispersal modeling approach. Our results highlighted larval exports from the NW GOM banks to the northeastern and southwestern GOM, larval connectivity between all banks investigated in this study, and the potential for exporting larvae from mesophotic to shallower reefs. Our study associated with Studivan and Voss (2018; associate manuscript) demonstrates the relevance of combining modeling and genetic methods to consider both demographic and genetic timescales for the evaluation of the connectivity dynamics of marine populations. In the case of the NW GOM, both studies support the future management plan for expanding FGBNMS.

Blue crab larval dispersal highlights population connectivity and implications for fishery management

“…This model was also used to predict likely drift tracks of sea turtle carcasses in the north central GOM (Nero et al 2013). In a more recent study, Garavelli et al (2018) used AMSEAS to simulate coral reef larvae transport within and from the Flower Garden Bank in the northwestern GOM.…”

“…These studies showed an overall gene flow throughout the US blue crab population, except those populations near Apalachicola, Florida, which have been found to exhibit a degree of isolation (Darden 2004, Feng et al 2017. This isolation may be due to their proximity to the Loop Current (LC) (Feng et al 2017), which could be a prominent larval transport feature in the GOM (Lee et al 2002, Garavelli et al 2018. Assessing the connectivity of blue crab larvae along the Florida coast is essential for identifying the population structure of the species.…”

Assessment of Mesophotic Coral Ecosystem Connectivity for Proposed Expansion of a Marine Sanctuary in the Northwest Gulf of Mexico: Population Genetics

“…Historical migration models based on genetic data predicted panmixia of M. cavernosa across the NW GOM. The comparisons between genetic and biophysical models (see Garavelli et al, 2018) highlight not only the importance of incorporating multiple assessments of connectivity into management schemes, but also the potentially stochastic nature of oceanographic patterns in the NW GOM and their effect on migration estimates among coral habitats. These trends indicate that M. cavernosa populations have remained well-connected in the NW GOM and that coral populations on each bank have likely been receiving larval recruitment through time.…”

Coral Reefs in the Gulf of Mexico Large Marine Ecosystem: Conservation Status, Challenges, and Opportunities

“…Virtual larvae of red grouper (Epinephelus morio), lionfishes (P. volitans, and P. miles), and a "generic" marine organism showed physical connectivity among the Campeche Banks -particularly the NE perimeter -to the NE GoM defined as locations within the gulf, and western Atlantic explained by the position, and strength of the Loop Current (Johnston and Bernard, 2017). Garavelli et al (2018) studied the connectivity along banks in the NW GoM using virtual larvae, concluding that Montastraea cavernosa larvae, a common reef-building coral species in CR and banks in the region, is exported to the northeastern, and southwestern GoM. This same species is a key element in shallow reefs in the region, making deep banks potentially important as refugia for the changing condition that shallow reefs are experiencing .…”

“…It is important to understand how human activity can impact connectivity or create connectivity that otherwise would not exist, as this can modify the way invasive species, and disease pathogens are spread throughout the region. Thus, as suggested by Garavelli et al (2018), future connectivity research among all mesophotic coral ecosystems, and beyond to include other important coral habitats in the region using multiple species models to assess the possibility of establishing a regional conservation plan are needed. Using large-scale mapping might help with prioritizing areas for protection and/or restoration to get a higher return on investment not just locally but regionally as well.…”