A paradoxical reef from Varadero, Cartagena Bay, Colombia

Abstract

Coral reefs in the Bay of Cartagena, Colombia, have been heavily disturbed by anthropogenic perturbations since the founding of Cartagena in 1533. A prominent perturbation was the construction of Canal del Dique, a channel built by the Spaniards to shorten the access to the Magdalena River, a major waterway used by Colombian authorities for colonization and later for commercial purposes. Canal del Dique turned the clear waters of Cartagena Bay into a seasonally fluctuating, highly turbid, and eutrophied body of water with high sedimentation, and most coral reefs within the Bay disappeared (Restrepo et al. 2006). Even reefs outside the Bay, like those of Rosario Islands, were negatively affected. Only a few reefs remained, though they were also severely affected by human activities, such as the dredging of one of the natural mouths of the bay for seaport access.Recently, while looking for excavating sponges at Varadero (10°18¢10 †N, 75°34¢55 †W), an area adjacent to the dredged channel, we found what might be one of the best coral reefs on the continental shelf of Colombia in terms of coral cover (up to 80 %) and dominated by Orbicella spp. (Fig. 1). The total extension of this formation is close to 1 km 2 . A well-developed coral reef in such a highly degraded environment is contrary to expectations. With massive coral colonies >3 m in diameter and a total scleractinian richness of at least 30 species, this reef challenges traditional paradigms regarding ideal conditions for the growth and development of coral reefs (i.e., oligotrophic and clean waters with good sunlight penetration). The largest colonies found must have survived repeated human disturbances. Corals in shallow areas of this reef exhibit the flattened and encrusting growth forms typical of greater depths (>15-20 m). This coral formation is a unique resource that should be conserved and further studied considering its high species diversity, the large size of some of its coral colonies, and the atypical conditions under which it developed. ReferenceRestrepo JD, Zapata P, Díaz JM, Garzón-Ferreira J, García CB (2006)

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“…The existence of Varadero, a "paradoxical reef" (López-Victoria et al, 2015), is a call for scientists and managers to start looking in unexpected places for similar reefs. More importantly,…”

“…In order to supplement the brief, general description of Varadero Reef reported by López-Victoria et al (2015), detailed geomorphological and biological surveys were performed between 2014 (March) and 2015 (March and October). During the March 2015 field trip, Reef's geographic extent was assessed by two researchers diving along the border of the Reef with a GPS, recording in tracking mode, attached to an accompanying buoy.…”

“…In 2013, a reef was discovered under unexpected conditions below a thick layer of highly turbid water at the mouth of Cartagena Bay, Colombia (López-Victoria et al, 2015). This reef, known as Varadero, is located south of Tierra Bomba Island, at the mouth of the highly-polluted Bay.…”

“…Paradoxically, Varadero Reef has not only survived, but thrived with up to 80% coral cover dominated by large Orbicella spp. colonies, the major reef building corals in the Caribbean (López-Victoria et al 2015).…”

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“…This premise is reinforced by other studies in the Indian and Pacific Oceans (van Woesik et al, 2012;Cacciapaglia and van Woesik, 2015), which observed turbid nearshore environments as climate change refuges with turbidity mitigating high-temperature bleaching. In addition, there have been reports of healthy coral reefs (high coral cover) in the Caribbean in areas of high anthropogenic inputs (García-Sais et al, 2014;López-Victoria et al, 2015).…”