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291 ≋ Hidalgo et al. 2008). About the same time as the first signs of concern for the state of the reefs appeared (Chávez and Hidalgo 1988; Tunnell 1992), a catastrophic demise of the acroporid corals in the western Gulf reefs was reported (Jordán-Dahlgren 1992). This further increased the need to understand the nature of the ecological connectivity among the Gulf of Mexico reefs and between Gulf reefs and reefs in the Caribbean as potential larval sources. The purpose of this contribution is to present an analysis of the biogeography and potential connectivity from scleractinian data, and to discuss briefly the results in terms of coral reef conservation. To do this, a brief characterization of the reef systems involved is necessary. Southwestern Gulf Reefs Characterization and Setting Coral reefs in the Gulf of Mexico are found mostly on the outer reaches of the continental shelf, and their distribution can be grossly divided in 2 main environmental settings : those directly influenced by the Gulf Stream (such as the northwestern Cuban reefs and the Florida Keys) and those in the inner Gulf. Among the latter, there are environmental differences between those on the northern shelf (Flower Gardens Banks and Middle Grounds) and reefs in the southwestern Gulf. For instance, offshore Flower Gardens Banks reefs on the Texas–Louisiana shelf flourish in relatively deep waters (> 20 m) upon diapiric Coral reefs in the Gulf of Mexico are found not along the continental shelves, but rather in restricted locations where environmental conditions have been adequate for the coral biota to build up the reefs. Because coral reefs are determined by the environmental particularities of the location where they are formed, the formations in the southwestern Gulf are quite different from the ones located in the northern Gulf. Reefs in the latter region are generally well developed, but they are clustered in a few distant localities and therefore are relatively isolated. Because of this spatial layout, understanding how these reefs might be ecologically connected is of great scientific and practical interest, and this is now possible because scleractinian species composition of most reefs was well characterized between the 1960s and 1980s (see review in Jordán-Dahlgren and Rodríguez-Martínez 2003). Gorgonian fauna analyses of the ecological connectivity among southwestern reefs suggest a variable and sporadic process (Jordán-Dahlgren 2002), whether this is also true for all or some scleractinian corals is unknown at present because ecological connectivity is taxon dependent. The first comparisons of coral species composition between reefs in the Gulf of Mexico and Caribbean were published in the 1970s and 1980s (Glynn 1973; Chávez et al. 1985; Ferre D’Amare 1985). By the late 1980s and 1990s, the information was comprehensive enough to support the first quantitative evaluations (Liddell and Ohlhorst 1988; Gutiérrez et al. 1993; Chiappone et al. 1996), which continued through the last decade (Horta-Puga et al. 2007; Chávez16 Southwestern Gulf of Mexico Reefs Connectivity, Biogeographical Relationships, and Management Implications Hector Reyes-Bonilla and Eric Jordán-Dahlgren 292 ~ Reyes-Bonilla and Jordán-Dahlgren enced by continental discharges and contains several offshore reefs in a calcareous environment. In both areas, the western shelf and Campeche Bank, emergent coral reefs are relatively scarce and relatively isolated. Coral reefs cover less than 1.5% of the more than 60,000 km2 of the shallow shelf area in the southwestern Gulf. However, the area that may be suitable for coral biota colonization may be far larger than the emerged reef area on Campeche Bank. The general setting and characteristics of these reefs have already been described by many authors (see review by Jordán-Dahlgren and Rodríguez-Martínez 2003), and here we provide a succinct description to allow us to discuss the issues of potential larval connectivity among these reef systems. Campeche Bank Reefs Both emergent and submerged bank reefs are found on Campeche Bank. The majority of these reefs lie in the outer reaches of the extensive shelf up to 130 km offshore (although a few nearshore reefs are also found near the town of Sisal) (Fig. 16.1). Offshore reefs rise from depths of 30–40 m, are well developed and vary in morphology and size, and are characteristically quite banks; the coral biota is dominated by species that can tolerate low-light regimes; and one of the main reef builders of the Caribbean region, Acropora palmata, is absent (Rezak et al. 1990). Other differences in these reefs are...

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