Encrusting and excavating Caribbean sponges Cliona aprica, C. caribbaea and C. tenuis (Hadromerida: Clionaidae) aggressively undermine and displace live coral tissue. To establish modes and rates of lateral advance into neighboring organisms, 171 sponge individuals were studied for 13 mo. Sponge advancement into live coral, via excavation underneath boundary polyps, occurred only when the 2 confronted at an angle of ≥180°. Sponges stopped or retreated when coral upward and inward growth at the boundary closed the angle between the coral and sponge, placing polyps out of reach of excavating tissue. At a straight angle of confrontation, C. tenuis advanced into coral at higher rates than the other 2 sponge species. Its advance was more pronounced into Diploria strigosa than into Siderastrea siderea. Sponge undermining continuously opened space for transient settlement of turf algae and for accumulation of sediments. Corallivory at the sponge-coral boundary did not imply greater rates of sponge advance, but probably did contribute to coral bioerosion. Massive corals escaped sponge undermining by upward growth, their ability to do so depended partly on defensive mechanisms. Foliose and platy corals escaped by overtopping. Rates of sponge advance into substrata incrusted and overgrown by algae were in general lower than into live coral, while sponges lost space to some encrusting invertebrates.

Some sponges of the genus Cliona (Porifera, Hadromerida, Clionidae) simultaneously excavate and encrust calcareous substratum, competing aggressively for illuminated space with corals and other organisms. To interpret current trends of reef space occupation, the patterns of distribution and size of three Caribbean species were examined at San Andrés Island and Islas del Rosario in Colombia. While Cliona aprica was ubiquitous, C. caribbaea (= C. langae) preferred deep and protected reef zones, and C. tenuis shallow and wave‐exposed settings. In contrast to the effect on other excavating sponges, chronic exposure to raw sewage did not significantly increase the abundance of the studied sponges. Substratum occupation/availability ratios showed a positive tendency of the sponges toward certain coral skeletons, and a negative or neutral tendency toward calcareous rock, indicating that establishment may be easier on clean, recently dead coral than on older, heavily incrusted substratum. High relief generally limits sponge size to that of the illuminated portions of the substratum. A generally lower proportion of small individuals than of larger ones indicates currently low recruitment rates and low subsequent mortality. Successful events of higher recruitment seem to have occurred for C. tenuis. These are related to the massive acroporid coral die‐off in the early 1980s and to asexual dispersion during storms, resulting in a current 10% substratum cover. Reefs with high coral mortality were and/or are thus more susceptible to colonization and subsequent space occupation by these sponges, although relief may prevent space monopolization.

Coral reefs are commonly associated with oligotrophic, well-illuminated waters. In 2013, a healthy coral reef was discovered in one of the least expected places within the Colombian Caribbean: at the entrance of Cartagena Bay, a highly-polluted system that receives industrial and sewage waste, as well as high sediment and freshwater loads from an outlet of the Magdalena River (the longest and most populated river basin in Colombia). Here we provide the first characterization of Varadero Reef’s geomorphology and biological diversity. We also compare these characteristics with those of a nearby reference reef, Barú Reef, located in an area much less influenced by the described polluted system. Below the murky waters, we found high coral cover of 45.1% (±3.9; up to 80% in some sectors), high species diversity, including 42 species of scleractinian coral, 38 of sponge, three of lobster, and eight of sea urchin; a fish community composed of 61 species belonging to 24 families, and the typical zonation of a Caribbean fringing reef. All attributes found correspond to a reef that, according to current standards should be considered in “good condition”. Current plans to dredge part of Varadero threaten the survival of this reef. There is, therefore, an urgent need to describe the location and characteristics of Varadero as a first step towards gaining acknowledgement of its existence and garnering inherent legal and environmental protections.

The broken, dead stands of the Caribbean elkhorn coral Acropora palmata, which suffered massive mortalities from disease and bleaching during the early 1980s, are now widely covered by Cliona tenuis, an encrusting and excavating brown sponge (Hadromerida, Clionaidae). This sponge displaces live coral tissue by undermining the polypal skeletal support. On the windward fringing reef of Islas del Rosario (Colombian Caribbean), 26% of C. tenuis individuals currently dwelling on live corals had colonized their host from sponge-carrying branches of A. palmata thrown against the corals during storms. Times of initial colonization were traced back from sponge growth rates in a few marked massive coral colonies and found to coincide approximately with hurricanes that had affected the area. Transplantation experiments confirmed that C. tenuis is able to spread to new coral hosts from attached fragments. The extent of C. tenuis dispersion via branching coral fragments and further massive coral colonization is now evident and, given that C. tenuis-encrusted A. palmata fragments are becoming progressively smaller, the phenomenon is likely to increase. C. tenuis was also found undermining encrusting and foliose corals settled on dead A. palmata branches, thus also retarding the process of reef recovery to an unknown degree.

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)

Due to the worldwide degradation of coral reefs, the active restoration of these ecosystems has received considerable attention in recent decades. This study investigated (1) the feasibility of using coral nurseries for restoration projects, (2) the minimum size required for a Pocillopora damicornis (Pocilloporidae) coral fragment to survive and grow in a nursery, and (3) the optimal transplant size of a fragment when transplanted to a degraded reef at Gorgona Island (Colombian Pacific). For this investigation, 230 fragments were transplanted directly to El Remanso reef, and another 150 fragments were maintained in in situ nurseries. Every 2 months, the length, weight, and survival of the fragments were recorded. After growing for 134 days in the nurseries, the 52 surviving fragments were transplanted to El Remanso reef, and after 5 months, the same variables were measured. Among the nursery-reared fragments, the largest (4 to <8 cm) had the highest survival and growth rates, whereas among the directly transplanted fragments, the smallest fragments (<2 cm) had the highest survival and growth rates. However, the nursery-reared fragments acquired greater structural complexity (arborescent morphology), and they were all alive 156 days after transplantation and presented a maximum linear growth rate of over 2 cm, which was higher than that of the directly transplanted fragments. Apparently, the arborescent morphology acquired during the nursery period provides advantages to the colonies that favor greater success when transplanted. Therefore, nursery-reared fragments of P. damicornis between 2 and 4 cm are the most appropriate for use in restoration projects.

Johngarthia malpilensis (Faxon, 1893) is the least studied of the eight American species of Gecarcinidae. This land crab is considered endemic to Malpelo, an oceanic island of the Colombian Pacific. Several aspects of its ecology were investigated between 2003 and 2006. We estimated its population density, distribution, daily activity, reproduction, interactions, and diet by marking and monitoring 909 individuals. During our visits we recorded crabs of sizes from 5 to 82 mm carapace width. Johngarthia malpilensis shelters mainly in fissures and hollows between rocks. It is distributed all over the main island except in very steep sectors. An average density of 0.41 adults m À2 and 0.55 juveniles m À2 produced an estimated total population of 833,000. Johngarthia malpilensis showed high mobility, with crabs covering distances over 450 m in a few days on highly irregular surfaces. Activity was higher from dusk till dawn and lowest around noon. Release of larvae took place during the high tides associated with the new moon, at least during the rainy season. It is omnivorous and opportunistic, consuming practically every available resource. The crab is occasionally preyed upon by an endemic lizard and migratory birds. Its general ecology is very similar to that of J. planatus, a closely related species. As a voracious omnivore J. malpilensis is one of the most important components of Malpelo's food web.

Coral reefs are undergoing degradation due to overexploitation, pollution, and climate change. Management and restoration efforts require that we gain a better understanding of the complex interactions between corals, their microbiomes, and their environment. For this purpose, Varadero Reef near Cartagena, Colombia, serves as an informative study system located at the entrance of the Bay of Cartagena adjacent to the Canal del Dique, which carries turbid and polluted water into the bay. Varadero’s survival under poor environmental conditions makes it a great study site for investigating the relationship between the microbiome and coral resistance to environmental stressors. To determine whether the microbiomes of Varadero corals differ from those in less impacted sites, we conducted a reciprocal transplant experiment by relocating coral fragments from Varadero as well as a geographically proximate reef that is less affected by plume dynamics (Rosario) across a gradient of turbidity (low, medium, and high). After 6 months of acclimatization, transplanted corals developed site-specific microbiomes that differed significantly from pre-transplant microbiomes, and corals transplanted to the highly impacted site from both Varadero and Rosario site saw higher mortality and an increase in overall microbial diversity. In combination with physiology and survivorship outcomes pointing to a limit in the corals’ photoacclimative capacity, our results indicate that, rather than surviving, Varadero Reef is experiencing a slow decline, and its corals are likely on the brink of dysbiosis. With continued anthropogenic interference in marine environments, sites such as Varadero will become increasingly common, and it is imperative that we understand how corals and their microbial symbionts are changing in response to these new environmental conditions.