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Click below to go to the Cruise Logs - (photo credit: Lophelia Coral - Open-File Report 2008-1148 & OCS Study MMS 2008-015)

DISCOVRE 2009



Cruise Log: 9/17/2009    



Population Connectivity

Cheryl Morrison

Lophelia pertusa reef at the West Florida Slope, Gulf of Mexico. (Credit: USGS DISCOVRE) - click to enlarge
Lophelia pertusa reef at the West Florida Slope, Gulf of Mexico. (Credit: USGS DISCOVRE) - click to enlarge
One of the themes that ties many of our research objectives together is 'connectivity', or the extent to which spatially separated populations are linked through the exchange of juveniles or adults. As you may imagine, animals that swim have the potential to move between geographically separated locations (in this case reefs) throughout their lives, while animals that live attached to a hard substrate, such as corals, can reach new reef locations only during larval stages when they swim or drift with prevailing currents. Therefore, some animals may be more connected than others. It is difficult to observe and quantify patterns of connectivity between Lophelia reefs.

Connectivity in Lophelia
In our connectivity studies, we aim to identify the pathways in which animal exchanges take place among Lophelia reef habitats, the spatial scales that exchanges are likely to occur, and ultimately, the biological and physical forces that shape these patterns. However, studies of connectivity are not straightforward because it remains difficult to observe and quantify animal movements. Therefore, we use indirect methods to assess connectivity. One such method is population genetics, where highly variable molecular markers are utilized to characterize populations. Since movements will homogenize the genetic signature between populations, we can examine the extent of shared genetic markers and then estimate levels of connectivity. In our initial survey of Lophelia populations in the Gulf of Mexico (see picture from the West Florida Slope Lophelia habitat taken yesterday) and the North Atlantic Ocean off the southeastern U.S. (see Map), we found that connectivity was fairly high within ocean regions (Gulf vs. Atlantic), but was restricted between regions. Additionally, populations that occur at similar depths had higher connectivity.

Map of Lophelia pertusa collection localities in the North Atlantic Ocean and Gulf of Mexico (Credit: M. Carlson, UNCW) - click to enlarge
Map of Lophelia pertusa collection localities in the North Atlantic Ocean and Gulf of Mexico (Credit: M. Carlson, UNCW) - click to enlarge
Connectivity and Resource Management
Knowledge of connectivity patterns helps resource managers develop effective plans to protect these fragile deep-sea ecosystems. For example, we can identify populations that act as sources of animals to other populations because animals often move (or disperse) from these source populations. Sources may become very important in replenishing neighboring reef areas that are damaged. On the other hand, reefs that are less connected are more isolated, potentially making them vulnerable to extinction should they be damaged. From connectivity studies we also learn about how reef communities are structured and how biodiversity is distributed in the Gulf. An interesting aspect of the Gulf of Mexico is that many man-made structures such as shipwrecks and oil rigs occur here. Such structures may essentially increase connectivity between natural reef areas if they occur in an intermediate location between reefs. We are still discovering new Lophelia reef habitats. As knowledge of connectivity patterns improves and more data regarding bottom topography and currents becomes available, we will be able to predict where additional reef habitats are located with more accuracy, allowing for protective measures to be established.



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