Adolfo Sanjuan

La información recopilada en este recurso tenía el objetivo describir los patrones alimentarios de los peces pelágicos y demersales del Caribe norte de Colombia, a partir del análisis de contenido estomacal y análisis isotópico (δ15N y δ13C) y así Identificar las variaciones en los patrones alimentarios y las relaciones tróficas de los peces pelágicos y demersales, asociadas a las épocas climáticas y relacionarlas con las condiciones ambientales de la zona.

Caribbean reefs are under a shift phase and corals like Poritids are colonizing the disturbed surfaces formerly occupied by Acroporids. Porites porites was used as a model species, a colony collected in Curacao has been cultivated at the aquaculture facilities of Wageningen University (The Netherlands), where the research was done. Coral culture in aquariums is a step for understanding coral growth, acting as a guideline to ensure successful maintenance, growth and reproduction through proper husbandry. The aim was to assess whether P. porites growth under controlled conditions has an accelerated growth and high calcification rates. Two aquariums with different alkalinities were used (2.4 and 4.8 mEq L -1 ). Each tank was held with four fragments and 10 nubbins at the same irradiance and 10 nubbins more to low irradiance (210 and 110 µEm -2 s -1 ). The optimal environmental conditions were identified and standardized. Growth, calcification, photosynthesis and respiration rates were ...

The long term survival of Acropora cervicornis is threatened. Implementing conservation and management measures to mitigate the deterioration is essential through the use of effective tools.  Mariculture of coral fragments in nurseries has been used as a key management tool in conservation. In Bonaire, Netherlands Antilles, (12° 10' N, 68° 15' W), clones from 10 donor colonies have been fragmented and successfully cultivated in nurseries. The aim of the study was to assess whether A. cervicornis growth in coral tree nurseries, may provide a way to recolonize large parts of the reef testing the effect on the survival and growth in the wild. Regeneration after fragmentation was reflected with healing of colonies with the respective fragments (n=234). Coral growth was measured as the increment of weight in fragments from three source colonies (n=180). They were randomly distributed and attached to the nurseries and to rebar structures in three transplantation sites. In those si...

Lithophaga nigra (d’Orbigny, 1853) is an uncommon boring bivalve that inhabits dead coral skeletons and occurs in the Caribbean Sea and the Indopacific region. One specimen of this species was collected within a dead head of the coral Montastraea sp. in Playa Blanca, (bahía de Gaira) near Santa Marta at 10 m of depth, and it is recorded for the first time in the Colombian Caribbean.

cover and structural attributes of mangrove forests in the Baja Guajira were estimated and identified. Forest cover was estimated from ASTER images and aerial photographs. The forest structure was evaluated along transects which were 10 m broad and as long as the width of the mangrove fringe. In each transect mangrove trees were identified and counted. The total height and the diameter at breast height (DBH) of the trees were measured and subsequently the basal area, density and Importance Value Index (IVI) calculated. The estimated mangrove cover of the Baja Guajira was 59.9 ha. The most frequent and dominant species was Laguncularia racemosa (0.54 m2.ha-1). Rhizophora mangle was present in 75 % of the stations, while Avicennia germinans was only found in the north of the study area. The highest average heights and diameters for R. mangle, L. racemosa and A. germinans were determined in Rincón Mosquito (12.9±2.3 m and 22.4±11.2 cm), Puerto Brisa (12.2±5.3 m and 20.8±9.8 cm) and La ...

De julio a diciembre de 2008 en la bahía de Cispatá, Córdoba (Colombia) el grupo de investigación sobre Dinámica y Manejo de Ecosistemas Marino-Costeros de la Universidad Jorge Tadeo Lozano, Seccional del Caribe se determinaron los aspectos biológicos y ecológicos del cangrejo azul (Cardisoma guanhumi), el chipi chipi (Anomalocardia brasiliana, Donax denticulatus y D. striatus) y los mugílidos (Mugil incilis, M. trichodon, M curema y M. liza), cuyas poblaciones son objeto de una alta explotación, por lo que es encesario adoptar alternativas encaminadas a proteger y contrarrestar el deterioro de estos recursos. Se destaca la participación activa de la comunidad en el Proyecto y se recomienda continuar con campañas educativas y estudio aplicables en el Plan de Manejo de la Bahía

Sipunculans represent a discrete component of the coral reef ecosystem, since they live inside the calcareous structure. They are an important component in terms of biomass and number of organisms. The present study describes the diversity of sipunculans living inside massive coral skeletons. A total of 43 blocks of dead coral skeletons from Montastraea cavernosa, Montastraea annularis and Diploria strigosa were collected from nearby coral reef areas off Santa Marta, on the Colombian Caribbean coast. Using hammer and chisel, blocks of approximately 1 dm3 were broken into small pieces, from which the sipunculans were extracted. A total of 381 organisms were obtained from the coral blocks comprising four families and 10 species. All the species found have been widely reported in different studies from the Caribbean region. Aspidosiphon fischeri and Phascolosoma perlucens were the two most abundant species comprising more than 60% of the total organisms with a mean density of 18.52 ± 4...

In coral reefs, competition between sessile benthic organisms for access to space and other resources is a determining factor in community structuring. Recent coral mortality has favored the development of algal turfs, which are now competing with corals, often displacing them,although slowly. To determine the frequency of interactions between coral-turf and coral-other benthic categories, and how their distribution and results (coral wins or coral loses) are modulated by environmental factors, band photo transects were evaluated for 12 stations in the ParqueNacional Natural Tayrona, Santa Marta, Colombian Caribbean. It was found that algal turfs are the most frequent competitors of massive corals, and that the frequency of coral-turf interactions depends on the particular susceptibility of a coral species to the loss of tissue, and past disturbances that have affected the reef in which it lives. Furthermore, the results of these interactions depend on the ways the colonies are orga...

The trophic ecology of the pelagic thresher shark (Alopias pelagicus) was analysed using stomach contents and carbon (d13C) and nitrogen (d15N) stable isotope analysis. The sharks were caught in Ecuadorian waters between June and December 2003. Approximately 24 prey species were found in the stomachs of 111 sharks. The most common species were Dosidicus gigas, Benthosema panamense and Sthenoteuthis oualaniensis. Mean (9SD) muscle isotope values of the pelagic thresher shark were 16.090.3for d13Cand 13.791.1for d15N; mean (9SD) vertebrae valueswere16.792.0 for d13Cand 9.491.8 for d15N. There were no significant sex-related differences in muscle d13Cand d15N; however, female vertebrae had significantly higher mean (9SD) d13Cvalues (16.492.0) than males (18.890.3). Inter-individual variation in d15Nvalues was observed in both tissues and was likely related to foraging in different ecosystems with distinct isotope values. Both stomach content and isotope data suggest that the pelagic thresher shark is a specialist predator in Ecuadorian waters. In general, little is known about the foraging ecology and movement patterns of this globally distributed but elusive top marine predator, and how these fundamental ecological traits vary among populations. By using two independent but complementary approaches, our study addresses these questions for the pelagic thresher sharks in Ecuadorian waters. Such information is critically important for the design of effective management strategies for these highly exploited but poorly understood predators.

"The present study determined the average mercury bioaccumulation in the muscle tissue of four shark species (Carcharhinus falciformis, Prionace glauca, Sphyrna zygaena and Isurus oxyrinchus) captured in the Baja California Peninsula. We also evaluated biomagnification of some prey consumed by sharks. All sharks’ species had mercury levels over the limit specified by the Mexican government for human consumption. Blue shark (P. glauca) presented highest mercury values (1.96 ± 1.48 lg/g Hg d.w.) and it was the unique specie that showed a negative correlation with mercury content (Rs =-0.035, p = 0.91).
Scomber japonicus was the prey with high content of mercury
(0.57 ± 0.02 lg/g)."

Bioecological aspects of 561 M. incilis captured by casts-net (75.4%) and gill net (24.6%) in Cispatá bay, between July and December 2007 were determined. Total length (TL) was between 17.5 to 44.5 cm TL, most of the individuals were juvenile, which is reflected in the allometric growth: W (g) = 0.01 TL (cm)2.83 (r2 = 0.92). 48% were males (n = 221) and 52% females (n = 240); there was no significant deviations of the 1:1 sex ratio (χ2 = 0.39; p = 0.53). Maturity size was estimated on 30.5 cm TL for both sexes, 30.3 cm TL for females (n = 188) and 35.6 for males (n = 231). Gonadosomatic and hepatosomatic indices increased at the end of the year, in the same way as the gonad development stages III, IV and V, suggesting a reproductive peak of M. incilis. Out of the 177 fishes examined, it was determined that 65% contained parasites, with an abundance of 3.4 ± 0.5 parasites/fish and a mean intensity of 5.4 endoparasites/infected fish. Parasitic fauna were identified as: Ergasilus sp., Caligus sp., Contracaecum sp. and Acantocephalans; although the latter group is not considered a pathogen, further research is necessary to explain its representation. From the information generated, a fisheries management improvement was suggested for M. incilis in Cispatá bay.

"Extension and structure of mangrove forests in the Baja Guajira, Colombian Caribbean. In April 2007, cover and structural attributes of mangrove forests in the Baja Guajira were estimated and identified. Forest cover was estimated from ASTER images and aerial photographs. The forest structure was evaluated along transects which were 10 m broad and as long as the width of the mangrove  fringe. In each transect mangrove trees were identified and counted. The total height and the diameter at breast height (DBH) of the trees were measured and subsequently the basal area, density and Importance Value Index (IVI) calculated. The estimated mangrove cover of the Baja Guajira was 59.9 ha. The most frequentand dominant species was Laguncularia racemosa (0.54 m2/ha). Rhizophora mangle was present in 75 % of the stations, while Avicennia germinans was only found in the north of the study area. The highest average heights and diameters for R. mangle, L. racemosa and A. germinans were determined in Rincón Mosquito (12.9±2.3 m and 22.4±11.2 cm), Puerto Brisa (12.2±5.3 m and 20.8±9.8 cm) and La Enea (13.8± 4.3 m and 23.8±14.8 cm), sectors with a constant fresh water supply. The less developed forest, a monospecific forest of Conocarpus erectus, was observed in Dibulla station, with height and
diameter averages of 2.8±0.6 m and 3.0±0.9 cm. In terms of natural regeneration, L. racemosa presented the highest proportion of seedlings in the study area, R. mangle was found in stations partly flooded and A. germinans had the highest density of seedlings and propagules at La Enea station."

"Algae are the most abundant reef organisms in most of the countries; high coral cover occurs at numerous reef locations at the Caribbean (~70%) and Pacific (~95%) coasts.
No major changes in live coral cover have been observed recently in the region; some localised decline and recovery trends are evident for each country.
Coral reefs in the region experience many natural and human threats, and predictions suggest that nearly 50% of reefs are at very low risk of decline in 5-10 years, even considering global climate change, and around 40% of reefs could be under high risk of decline in the mid-long term (>10 years).
Massive coral bleaching occurred in Southern Tropical America during 2005, but the severity varied across the región.
Reef monitoring has increased, but there is low funding for monitoring programs in all countries; socioeconomic monitoring is restricted to Brazil.
Information on reef fisheries from monitoring programs is scarce, however, the consensus is for depletion of coral reefs resources, particularly in the Caribbean.
Seagrass and mangrove communities are mainly threatened by coastal development, sedimentation, pollution, and deforestation.
"

The feeding habits of the common thresher shark (Alopias superciliosus) from the Pacific coast of Ecuador were investigated by using frequency of ocurrence, numeric and gravimetric methods. A total of 122 individuals were collected from July to December 2003 and grouped by sex and maturity state (mature vs. inmature). Stomach contents were examined and classified by components to infer trophic relations. A total of 27 prey taxa were observed as part of the diet of Alopias superciliosus. Overall, Larimus argenteus (RII=1497) was the most important in the diet, followed by Merluccius gayi (RII=333), Dosidicus gigas (RII=281) and Benthosema panamense (RII=239). The Levin’s index allowed to define A. superciliosus as an specialist predator that feeds in oceanic waters.

Lithophaga nigra (d’Orbigny, 1853) (Mollusca: Bivalvia: Mytilidae), first record for the Colombian Caribbean. Lithophaga nigra (d’Orbigny, 1853) is an uncommon boring bivalve that inhabits dead coral skeletons and occurs in the Caribbean Sea and the Indopacific region. One specimen of this species was collected within a dead head of the coral Montastraea sp. in Playa Blanca, (bahía de Gaira) near Santa Marta at 10 m of depth, and it is recorded for the first time in the Colombian Caribbean.

Cittarium pica desempeña considerables funciones ecológicas en los litorales rocosos del Caribe, por lo que su sobrexplotación y la consecuente disminución de sus poblaciones no solo puede acarrear consecuencias socio-económicas sino también ecológicas, reiterando la importancia de su conservación. El presente estudio se enfocó en las relaciones interespecíficas que C. pica exhibe con otras especies de fauna y flora marina en el medio natural. Se evaluó la comunidad asociada con C. pica en cinco sectores del Caribe colombiano: Urabá chocoano, Isla Fuerte, Cartagena e Islas del Rosario, Santa Marta y Parque Tayrona, y La Guajira, en donde se ubicaron varias estaciones. En cada estación se extendió un transecto en la zona intermareal del litoral rocoso sobre el que se colocaron sistemáticamente 30 cuadrantes. Se encontraron 25 especies de fauna y 24 de flora asociados, de las cuales 17 animales y 10 macroalgas presentaron correlación significativa con C. pica. Las de fauna que tuvieron mayor correlación con C. pica fueron Purpura patula, Acanthopleura granulata, Echinometra lucunter, Holothuria glaberrima, Bathygobius cf. soporator y Grapsus grapsus; mientras las macroalgas pertenecieron a los géneros: Laurencia, Padina, Chaetomorpha, Halymenia y  Sargassum. Se sugiere que estas correlaciones surgen como respuesta a las relaciones interespecíficas que se dan dentro de la comunidad, como competencia por espacio, alimento y depredación. Se realizó también un análisis de la epibiosis en C. pica para el sector de Santa Marta, encontrándose 16 especies de epibiontes; sugiriendo un vínculo de mutualismo. C. pica sirve de sustrato a los epibiontes y estos cubren su concha facilitando su camuflaje.