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En comparación con otros grupos de invertebrados, la taxonomía de esponjas (Porífera) ha sido poco desarrollada en el Pacífico Oriental Tropical (POT), en general, y en el Pacífico colombiano, en particular. Este trabajo busca incrementar el conocimiento de la biodiversidad del grupo en los arrecifes rocosos del norte del Chocó. Se recolectaron muestras de esponjas mediante buceo autónomo, las cuales fueron procesadas e identificadas en laboratorio por métodos estándar. Se confirmó la baja riqueza de especies y la predominancia de morfologías incrustantes y hábitos crípticos, que ha sido encontrada en otros estudios en la región. Se identificaron 24 morfotipos pertenecientes a 13 órdenes, 17 familias y 21 géneros. Doce (12) morfotipos se reconocieron a nivel de género o con identidad específica tentativa y los otros 12 fueron confirmados a nivel de especie. Seis (6) especies son morfológicamente similares a las del Caribe, lo que indica que las poblaciones posiblemente no han divergido lo suficiente desde el cierre del istmo de Panamá o, alternativamente, pueden haber cruzado recientemente el canal de Panamá.

Las lagunas costeras son foco de producción primaria y refugio de biodiversidad por su relativo confinamiento y baja profundidad. La Escollera es una laguna costera artificial situada en El Rodadero, Santa Marta (Caribe colombiano), excavada al inicio de la década de 1980 para albergar una marina y sus bordes sembrados con mangles. Para generar una línea base de variables físicas que contribuyan al entendimiento de la circulación del agua y de su influencia sobre los atributos del ecosistema, se obtienen de manera rutinaria datos de salinidad, temperatura, nivel del mar y penetración de la luz mediante registradores electrónicos y sensores de mano. Los datos de salinidad y temperatura entre enero de 2017 y febrero de 2018 siguieron el esquema estacional del mar abierto del área de Santa Marta alternando entre menor temperatura (mínima 24,6 °C) y mayor salinidad (máxima 38,9) en época seca y de afloramiento costero (diciembre a abril) y entre mayor temperatura (máxima 34,7 °C) y menor salinidad (< 35) en época de lluvia (mayo a noviembre), con los más bajos valores de salinidad luego de aguaceros persistentes (mínimo 15,1). La columna de agua está generalmente bien mezclada y se estratifica después de aguaceros en época de lluvia (mezclándose rápidamente en horas o en días). Esto parece deberse principalmente al intercambio con el mar gracias a la marea, que oscila de +0,37 a –0,31 m (rango máximo de 0,68 m [datos de un año]), y sigue el patrón astronómico regular de mareas mixtas del Caribe. Las aguas de la laguna son regularmente verdes y de variada transparencia excepto durante fuertes lluvias, tras lo cual se tornan pardas. La extinción de luz en la vertical es en general alta y no muy variable (2-6,5 % cm-1), pero la luz, con frecuencia, alcanza el fondo, lo que permite la existencia de macroalgas bentónicas en algunas porciones de la laguna.

Algal turfs are currently the most abundant benthic component on most coral reefs. Their wide distribution, functional role and positive responseto factors that stress corals confirm their importance in the functioning of reef ecosystem. It has been shown that species composition, structuraldevelopment and sediment retention influence their capacity to kill and displace adjacent live coral tissue. In this study in two reefs of the Tayrona National Natural Park (Colombian Caribbean), the variation in structure of turfs growing on and in direct interaction with massive live corals was determined,and its structural complexity was related with its sediment retention capacity. For that, the taxonomical composition was determined, and canopy height, cover and density of filaments and algal biomass were quantified for turfs growing on live colonies of four species of corals. The results showed that there are important structural differences between reefs and substratum type. In Granate reef (10-16 m), turfs form discontinuous carpets over crustose algae, and are constituted by articulated calcareous and little corticated algae, and juveniles of frondose algae, mostly of the genus Dictyota. During coastal upwelling, this genus grows profusely forming transient dense algal beds that later detach. In contrast, in Nenguange reef (4-6 m), turfs are perennial, form low, thick and dense carpets, with few crustose algae, and are dominated by filamentous and small corticated algae. It´s suggested that the presence of territories ofdamselfishes (Stegastes spp.) aid controlling the structural complexity of the turfs, and that vegetative propagation is the most frequent growth mechanism. In addition, it was found that the most morphologically complex turfs can retain greater amounts of sediments (silt-clay). This particulate material supports them; they can advance laterally and smother adjacent live coral tissue. This investigation provides the first quantitative data on the structure and amount of retained sediments by algal turfs growing on Colombian reef corals.

Las ramas muertas de Acropora palmata colonizadas por la esponja excavadora Cliona tenuis son propensas al desplazamiento, la rotura y la translocación durante fuerte oleaje o mar de fondo de tormentas o huracanes, lo que favorece la dispersión de esta esponja. En las islas del Rosario (Colombia, Caribe), los adultos de C. tenuis transportados por fragmentos de A. palmata que cayeron sobre corales masivos vivos colonizaron el nuevo coral y mataron posteriormente el tejido vivo del coral recién invadido. Los corales que reclutaron sobre las ramas caídas de A. palmata cubiertas de C. tenuis también fueron invadidos una vez que la esponja llegó a su base. Para determinar si la incidencia de este fenómeno aumentó desde 2002, cuando se documentó por primera vez, la prevalencia y el modo de colonización de corales por C. tenuis se cuantificó nuevamente en 2014, en el mismo arrecife. Aunque es difícil inferir una tendencia a partir de dos muestreos puntuales, el número de colonias de coral colonizadas por C. tenuis se duplicó en 2014 y se encontraron nuevos casos de colonización desde ramas de A. palmata portadoras de esponjas. Sin embargo, la frecuencia de colonización por esponjas adultas desde las ramas de A. palmata en 2014 fue entre la mitad y un quinto menor que en 2002, lo que sugiere que otras formas de colonización en corales masivos pueden estar aumentando o que las tormentas borran la evidencia de adultos colonizadores por la translocación de las ramas de coral que han servido de vectores, como se observó en un caso monitoreado. A medida que pasa el tiempo y aumenta la fragmentación y la erosión del arrecife, la evidencia de colonización de corales pétreos por C. tenuis a través de las ramas de A. palmata se desvanece.

Five demosponges belonging to the order Axinellida: Axinella corrugata, Dragmacidon alvarezae, Dragmacidon reticulatum, Ptilocaulis walpersi, Myrmekioderma rea and one sponge belonging to the order Scopalinida: Scopalina ruetzleri were analyzed to assess their fatty acid composition in the phospholipid fraction. Additionally, the seasonal and intraspecific variation in fatty acids composition was assessed in M. rea and D. alvarezae. Fatty acid identification was conducted using an HRGC-MS with an ECL value of methyl ester derivatives, and analyzing their mass spectra. To confirm double bound location, N-acylpyrrolidide derivatives were used studying their mass spectra. In total, 83 fatty acids were identified with chain lengths ranging from C14 to C32. Interestingly, brominated fatty acids were identified, previously suggested for sponges. Polybranched fatty acids such as 4,8,12-trimethyltridecanoic acid (4,8,12-TMTD) and 3,7,11,15-tetramethylhexadecanoic (phytanic acid) were found, without a clear distribution pattern. A predominance of iso-acids (i-15:0 and i-17:0) on anteiso acids were observed. Some seasonal variations in fatty acid (FA) compositions for M. rea and D. alvarezae were observed. The hierarchical Clusters Analysis (HCA) showed that the FA composition was species-specific but not informative at the family or order level.

El incremento en la frecuencia e intensidad de eventos oceanicos extremos limita la capacidad de recuperacion de los ecosistemas, amenazando su subsistencia. Con el fin de entender la relacion entre la estructura y salud arrecifal y los eventos extremos ambientales, se analizaron series de datos ambientales de las islas del Rosario ( e.g ., temperatura del mar, caudal y/o salinidad, turbidez), en comparacion con cobertura coralina y signos de deterioro ( e.g ., blanqueamiento, enfermedades). En las series de tiempo de las variables ambientales se calcularon los eventos oceanicos que excedieron un umbral estadistico, estableciendo su intensidad, duracion y frecuencia. Para los atributos de la comunidad, se evaluaron dos estaciones del Sistema Nacional de Monitoreo de Arrecifes Coralinos en Colombia (SIMAC), en dos ventanas temporales (largo plazo, 1998–2013 y corto plazo, 2013 - 2014). Los eventos extremos de temperatura superficial del mar, el caudal de descarga continental y la turbidez asociada fueron las principales variables relacionadas con la reduccion de la cobertura coralina. El blanqueamiento masivo de 2005 y otros eventos posteriores dieron como resultado una reduccion de la cobertura coralina entre 2004 y 2010. En el corto plazo no se registraron fuertes eventos extremos ni cambios en las formaciones coralinas, si bien el estres termico y las reducciones de salinidad en la epoca de lluvias estuvieron asociados con un ligero blanqueamiento en noviembre de 2014. Aunque los signos de deterioro sean bajos, es importante considerarlos, ya que la sinergia entre perturbaciones continuas puede conllevar a una perdida de cobertura del coral. Effect of extreme oceanic events in the coral formations of Islas del Rosario, Colombian Caribbean The increase in frequency and intensity of extreme oceanic events limits the capacity of recovery of ecosystems, threatening their subsistence. Thus, in order to understand the relationship between coral health and extreme environmental events, data on sea temperature, runoff and / or salinity, turbidity were analyzed in the Islas del Rosario in comparison with coral cover, and coral signs of deterioration ( e.g ., bleaching, coral diseases). In the time series of environmental variables, oceanic events that exceeded a statistical threshold were calculated, establishing their intensity, duration and frequency. The attributes of the community were studied through observations in two stations of the National Coral Reef Monitoring System in Colombia (SIMAC), assessed in two time windows (long term, 1998-2013 and short term, 2013-2014). The extreme events of sea surface temperature, river discharge and associated turbidity, were the main variables related to the reduction of coral cover. The massive coral bleaching of 2005 and other subsequent events resulted in a reduction in coral coverage between 2004 and 2010. During the short-term observations there were no strong extreme events or changes in coral formations, although thermal stress and reductions in salinity in the rainy season were associated with a slight bleaching in November 2014. Although the signs of deterioration are low, it is important to consider them, since the synergy between continuous disturbances can lead to a loss of coral cover.

Sponges (Porifera) are important constituents of littoral habitats in the Caribbean Sea.The knowledge of their biodiversity is fundamental to carry out ecological, managerial and utilitarianresearch. Their taxonomy is complex, but in the Caribbean in general, and in Colombia in particular, thereare important advances. With this work, some sponge species of the genera Petrosia and Xestospongiaare recorded and described for the first time from the Colombian Caribbean. Petrosia (Strongylophora)davilai, Xestospongia arenosa, Xestospongia deweerdtae and Xestospongia purpurea are described andillustrated. The number of records of Petrosia and Xestospongia for the Colombian Caribbean are nowthree and four species, respectively. In all species, the specimens from continental localities had largerspicule sizes than those from insular localities, apparently owing to a greater availability of dissolvedsilicon in the former. The existence in Xestospongia deweerdtae of free-living and Plakortis-associatedlifestyles was documented for new areas of the Caribbean.

RESUMEN En los arrecifes de coral, la competencia entre organismos bentónicos sésiles por acceso a espacio y otros recursos es determinante en la estructuración de las comunidades. La mortalidad coralina reciente ha favorecido el desarrollo de céspedes algales que pasan a competir con los corales, a menudo desplazándolos, aunque lentamente. Para determinar qué tan frecuentes son las interacciones coral-césped y coral-otras categorías bentónicas, y cómo su distribución y resultado (coral gana o coral pierde) son modulados por factores ambientales, se evaluaron fototransectos de banda en 12 estaciones del Parque Nacional Natural Tayrona en Santa Marta, Caribe colombiano. Se encontró que los céspedes algales son el competidor más frecuente de corales masivos así como que la frecuencia de interacciones coral-césped depende de la susceptibilidad particular de una especie de coral a perder tejido y de las perturbaciones que en conjunto afectaron el arrecife donde habita. Además, el resultado de estas interacciones dependió del tipo de organización colonial, siendo las colonias de tipo meandroide y cerioide los competidores más exitosos contra los céspedes, debido al mecanismo de evasión por crecimiento en altura, mientras que las colonias de tipo plocoide fueron más propensas a perder. En general, los factores biológicos (especie de coral y tipo de organización colonial) fueron determinantes en la frecuencia y resultado aparente de las interacciones coral-césped, en tanto que los factores ambientales (gradiente de perturbación, profundidad y grado de exposición al oleaje) parecen no desempeñar un papel preponderante. Por lo tanto, los cambios históricos y futuros en cobertura de cada especie coralina y el tipo de organización colonial en el área de Santa Marta deben reflejar una combinación entre su susceptibilidad a agentes deletéreos y su capacidad de contrarrestar o evadir la competencia, especialmente con céspedes algales. ABSTRACT 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 Parque Nacional 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 organized, meandroid and cerioid colonies being the most successful in competition against turfs, as their vertical growth constitutes an effective avoidance mechanism. By contrast, plocoid colonies are more prone to lose. In general, biological factors (the coral species in question and type of colonial organization) were determinants in the frequency and apparent result of coral-turf interactions, while environmental factors (disturbance gradient, depth, and degree of wave exposure) appear not to play a predominant role. As a consequence, historical and future changes in coral species cover, and the nature of colony organization in the Santa Marta area, should reflect a combination of their susceptibility to deleterious agents and their capacity to counteract or evade competition, especially with algal turfs.

RESUMEN La formación de biopelículas es un proceso importante para las comunidades bacterianas marinas debido a que este mecanismo favorece la adaptación a variaciones en las condiciones ambientales. El objetivo de este estudio fue evaluar la formación de biopelículas de las bacterias aisladas de sedimentos marinos en condiciones in vitro. Para esto se realizaron ensayos de cuantificación de biopelículas usando dos métodos, cristal violeta y reducción del colorante XTT; además se evaluó la viabilidad de las bacterias mediante la tinción Live/Dead. Posteriormente las cepas evaluadas fueron identificadas usando el marcador 16S ARN. Los resultados mostraron que los aislados pertenecen al género Bacillus todos en diferentes rangos fueron capaces de formar películas y se seleccionaron las cepas B. safensis 64181 y Bacillus sp 64186 las cuales indicaron mayor producción de esta. Los ensayos a diferentes temperaturas demostraron que para las cepas seleccionadas la mejor temperatura fue de 28°C. Además se realizó un cultivo mixto con estos aislados obteniendo como resultado diferencias en la densidad de la biopelícula y menos cambios en la actividad metabólica de la misma en los experimentos de variación de temperatura. A partir de los resultados podemos inferir que los consorcios bacterianos pueden favorecer la resistencia a variaciones ambientales en las biopelículas formadas por bacterias del género Bacillus. ABSTRACT Biofilm formation is an important process for marine bacterial communities because this mechanism favors adaptation to variations in environmental conditions. The objective of this study was to evaluate the biofilm formation of bacteria isolated from marine sediments under in vitro conditions. For this, biofilm quantification assays were performed using two methods, violet crystal and reduction of the XTT dye; In addition, the viability of the bacteria was evaluated by Live / Dead staining. Subsequently, the strains evaluated were identified using the 16S RNA marker. The results showed that the isolates belong to the genus Bacillus, all in different ranges were able to form films and strains B. safensis 64181 and Bacillus sp 64186 were selected which indicated greater production of this. Tests at different temperatures showed that for the strains selected the best temperature was 28 ° C. In addition, a mixed culture was carried out with these isolates, resulting in differences in the density of the biofilm and less changes in its metabolic activity in temperature variation experiments. From the results we can infer that bacterial consortiums can favor resistance to environmental variations in biofilms formed by bacteria of the genus Bacillus.

RESUMEN En los mares tropicales hay fondos duros sumergidos que albergan corales pero que no son de origen coralino. Este es el caso del sector del Banco de las Ánimas, en la plataforma continental del golfo de Salamanca, mar Caribe colombiano. En su parte superior (14-16 m de profundidad) hay montículos bajos de bloques y lajas de arenisca, a manera de arrecifes, colonizados por biota coralina y corales dispersos. Para confirmar su fitología, se realizó un primer análisis petrográfico, que mostró que las rocas están conformadas por arenas de grano muy fino, maduras en textura, cementadas por dolomita. Se propone que estos arrecifes fueron formados en un sistema playa-duna-laguna de un antiguo nivel del mar, similar a la actual barra costera de Salamanca. En estos ambientes supramareales salinos de alta evaporación, se pudieron formar como rocas de playa o como eolianitas, por cementación de aragonita, que fue convertida posteriormente en dolomita. Falta determinar si el basamento de las formaciones coralinas de mayor profundidad del Banco también es de arenisca, o es efectivamente coralino. ABSTRACT In tropical seas there are submerged hard bottoms that harbor corals but that are not coralline in origin. This is the case for the "Banco de las Ánimas" sector in the continental shelf of the Gulf of Salamanca, Colombian Caribbean. In its upper portion (14-16 m in depth), there are low mounds of sandstone blocks and slabs, conforming reefs, colonized by coralline biota and sparse corals. To confirm their lithology an initial petrographic analysis was carried out, which showed the rocks are made up of fine-grained sands, mature in texture, cemented by dolomite. It is proposed that these reefs were formed in a beach-dune-lagoon system during an ancient sea level, similar to the recent coastal bar of Salamanca. In these high-evaporation, supratidal saline environments, they could have been formed as beach rocks or as eolianites, by aragonite cementation, modified later into dolomite. Whether the foundation of the deeper coral formations of the bank is also sandstone or in fact coralline, remains to be determined.

The macrolide (+)-discodermolide produced by the marine sponge Discodermia dissoluta shows promising antitumor, antimitotic, and immunosuppressive activity. However, the sustainable supply of any molecule requires much in situ and in vitro research to optimize and later obtain the molecule of interest. In this study, two culture systems—fixed and suspended—were evaluated at 15-m depth in two sites, Punta de Betín and Nenguange, in Santa Marta (Colombian Caribbean). Survival, growth, and production of (+)-discodermolide were recorded, with the suspended system resulting in better growth and survival, depending on the culture site. The influence of the different environmental factors on survival was also studied, and a negative correlation with temperature was observed. Salinity, solar radiation, organic matter, and water flow were not correlated. Finally, no significant differences in the production of (+)-discodermolide existed between the culture systems and study sites. Production ranged from 20 to 270 μg per gram of dry sponge.

Exploration of continental shelves may produce unexpected faunal records. In shelf waters of La Guajira peninsula, Colombia, in the northern tip of South America, southern Caribbean Sea, we found a new species of Rhaphidhistia (Demospongiae, Hadromerida, Trachycladidae) a genus previously thought to be restricted to the Indo-Pacific Ocean. Rhaphidhistia guajiraensis sp. nov. is thickly encrusting, agglutinating bottom debris; it possesses asymmetric oxea as megascleres (465–757 μm by 6.3–17.5 μm) and spiraster-like spinispirae (15–37 μm by 2–5 μm). It is closely similar to the type species of the genus, R. spectabilis Carter, 1879, both standing apart from a third species, R. mirabilis (Dendy, 1924), thus conforming a natural group whose taxonomic placement needs to be reassessed. There are numerous cases of sponge genera with sister species in the Indo-Pacific and the Atlantic Oceans, possibly split since the Tethys Sea breakup; owing to their restricted or deep distribution, they are just starting to be discovered.

Changes in coral-sponge interactions can alter reef accretion/erosion balance and are important to predict trends on current algal-dominated Caribbean reefs. Although sponge abundance is increasing on some coral reefs, we lack information on how shifts from corals to bioeroding sponges occur, and how environmental factors such as anomalous seawater temperatures and consequent coral bleaching and mortality influence these shifts. A state transition model (Markov chain) was developed to evaluate the response of coral excavating sponges (Cliona delitrix Pang 1973) after coral bleaching events. To understand possible outcomes of the sponge-coral interaction and build the descriptive model, sponge-corals were monitored in San Andres Island, Colombia (2004-2011) and Fort Lauderdale, Florida (2012-2013). To run the model and determine possible shifts from corals to excavating sponges, 217 coral colonies were monitored over 10 years (2000-2010) in Fort Lauderdale, Florida, and validated with data from 2011 to 2015. To compare and test its scalability, the model was also run with 271 coral colonies monitored in St. Croix, U.S. Virgin Islands over 11 years (2004-2011), and validated with data from 2012-2015. Projections and sensitivity analyses confirmed coral recruitment to be key for coral persistence. Excavating sponge abundance increased in both Fort Lauderdale and St. Croix reefs after a regional mass bleaching event in 2005. The increase was more drastic in St. Croix than in Fort Lauderdale, where 25% of the healthy corals that deteriorated were overtaken by excavating sponges. Projections over 100 years suggested successive events of moderate coral mortality could shift algae-coral dominated reefs into algae-sponge dominated. The success of excavating sponges depended of the intensity of coral bleaching and consequent coral mortality. Thus, the proportion of Cliona delitrix excavating sponges is a sensitive indicator for the intensity and frequency of recent disturbance on Caribbean coral reefs. This article is protected by copyright. All rights reserved.

This study evaluates the biological activity and possible deterrance played by organic crude extracts from six Phaeophyta and two Rhodophyta algae from Southern Caribbean. Bioessays were carried out using concentrations equivalent to those present in algae tissue. Species in general did not show high citotoxic activity. However Dictyota pulchella, showed a delay in the mitotic process for cells stage XVI. Extracts from Dictyota bartayresiana, D. pulchella, Sargassum cymosum and Cladophyllum schnetteri, inhibited S. partitus feeding under laboratory conditions. Nontheless, only extracts from D. bartayresiana and C. schnetteri showed this activity in the field.

The icthyotoxic, cytotoxic and antimicrobial activities of aqueous, ethanol and chloroform extracts of 11 sponges from the Santa Marta region, Colombian Caribbean, were assayed. All studied sponges showed antimicrobial activity; 6 were ichthyotoxic and 7 were cytotoxic. Ircinia campana, Verongula rígida, Agelas conifera and Didiscus oxeata, were found to have activity in all three kinds of tests.

Temperaturas del agua de mar por encima del promedio durante 2005 en el Archipiélago de las Islas del Rosario (Caribe Colombiano) causaron un blanqueamiento coralino masivo en aguas someras (hasta 2-3 m de profundidad). Para confirmar resultados previos en los que el estrés inducido por calentamiento del agua en los corales puede acelerar la velocidad a la que esponjas excavadoras incrustantes le ganan espacio a los corales vivos, se contrastaron las tasas de propagación lateral en individuos de la esponja Cliona tenuis previamente marcados, que estaban colonizando los corales Diploria strigosa y Siderastrea siderea a profundidades de 5 - 6 m. Se hicieron comparaciones pareadas del avance de cada individuo de esponja entre dos intervalos de medida aproximadamente semestrales para dos períodos: junio 2001-julio 2002, que no tuvo un calentamiento inusual, y agosto 2004-septiembre 2005, con el calentamiento significativo sobre el umbral de blanqueamiento de corales, iniciado en junio 2005. Contrario a lo esperado, los datos no mostraron una influencia consistente del incremento de temperatura en la interacción esponja-coral durante el episodio de calentamiento. Las tasas de avance de C. tenuis contra S. siderea permanecieron bastante constantes, y fueron algo variables contra D. strigosa. La ocurrencia o no de cambios en el color de las colonias de coral (palidez, blanqueamiento) tampoco estuvo asociada con tasas de avance de C. tenuis consistentemente mayores o menores. Aunque es posible que un efecto generalizado de este fuerte calentamiento se rezagara hasta después de nuestro último intervalo de medida, los datos sugieren además que existe una susceptibilidad diferencial al calentamiento excesivo entre las especies y las colonias de coral y quizás entre los individuos de esponja.

From available data from four sampling stations at Ciénaga Grande de Santa Marta coastal lagoon (Colombian Caribbean), contemporary and time-lagged cross-correlations between biweekly series of "biological" variables (chrolophyll a, primary productivity) and "physical-chemical" variables (salinity, transparency, inorganic nutrientes, total nitrogen and phosphorous, phaeopigments, seston proteins) were explored. In contrast with the original analyses, turning series stationary (constant mean and variance) eliminated variations in trend and magnitude associated with climate, and emphasized variation at the scale of weeks. As a result, changes in primary production were not related either with contemporary changes in phytoplankton biomass (measured as chlorophyll a) or with previous or contemporary changes in physical chemical variables. This apparent lack of effect of the inorganic nutrients regime on the primary production may occur because nutrient availability is the dinamyc result of uptake and recycling. Only, increases in total nitrogen were associated with rises in primary production 4 weeks later, possibly from lagged used of reserves by phytoplankton. Variations in phytoplankton biomass were positively correlated with contemporary changes in dissolved phosphorous, and negatively with changes in transparency. The first relation could be caused by phosphorous liberation from the benthos in nocturnal anoxic conditions during massive blooms. The second may occur because the main agent conditioning water transparency is phytoplankton. In contrast, increases in primary production were followed by decreases in dissolved nitrogen and phosphorous two weeks later, again possibly in relation to phytoplankton generation times and the dynamics of uptake and recycling.

The Caribbean encrusting and excavating sponges Cliona aprica, C. caribbaea, C. delitrix and C. tenuis (Porifera, Hadromerida, Clionaidae), aggresively undermine and displace live coral tissue. At San Andrés island and Islas del Rosario (Colombian Caribbean), in all 145 observed cases of direct contact of the sponges C. aprica, C. caribbaea and C. tenuis with 17 coral species, corals showed unhealthy signs in their tissue. It was also noticed that the surface of these sponges is colonized by few organisms and that they are rarely preyed upon. To establish the possible use of chemical substances by these sponges in competition for space with corals (allelopathy), as inhibitors of larval settlement (antifouling), and as feeding deterrents against generalist fish (antipredatory), the activity of crude organic extracts was experimentally evaluated. Extracts were prepared in methanol and 1:2 metanol:dichloromethane and incorporated in experimental media at the natural concentration within the sponges. Using an unpublished method being developed by J. Pawlik (University of North Caroline at Wilmington) and M. Ilan (Tel Aviv University), PhytagelTM disks with crude extracts of each of the four sponge species, placed on the coral Montastrea cavernosa, produced a greater degree of polyp mortality than control gels without extract. Gels with extracts of the sponges C. aprica and C. caribbaea + C. tenuis, served in Petri dishes and used as substratum in the field, inhibited significantly the settlement of fouling organisms, in comparison to control gels. In laboratory trials, wheat flour pellets with extracts C. delitrix and C. caribbaea + C. tenuis were significantly rejected by the omnivore reef damselfish, Stegastes partitus, whereas pellets with extract of C. aprica did not deter feeding. These results suggest that substances present in the crude organic extracts of these sponges may be responsible in part for their ability to compete for reef substrata and to defend themselves from potential aggressors.

Variation in the taxonomlc and trophic structure of the zooplankton community, associated to fertilizations alternating between continental runoff and coastal upwelhng. were studied in the nenttc province of the Santa Maria area. Colombian Caribbean Sea. Sampling was carried out In November 1991 during the major rainy season, and in April 1992 during the dry season. Organisms were Identified, counted and trophically placed, and the biomass por trophic levo! was dotorminod. Eighty-two spocies-taxa were discriminated, most ot them oceaniccoastal and predominantly omnrvores. Community composition varied temporally and spatially with predominant oceanographic conditions, evidoncmg succossional procossos rotatod to fertilization pulses. During continental runoff conditions, typical of the rainy season, community composition and total biomass and abundance were spatially more heterogeneous, with species more coastal and neritic, large omnivores and detritivores and small carnívoros. Dunng upwellmg conditions, which occur as localizod pulses during the rainy season, and generalize throughout the study area during the dry season, the community was spatially more homogeneous, with spocies more ocoanic and doop-dwolhng and. in its maximum development, with higher biomasses. omnivores and detritivores small, and greater representation and size of macrofiltering herbivores and carnivores.

Ophiuroids are conspicuous dwellers of exposed and cryptic microhabitats available in coral reefs. This investigation pretended to discern ophiuroid community composition at microhabitats available in sponges and other reef components of different character (biotic v s. abiotic) or position over the substrate (elevated v s. non-elevated), at shallow reefs within the Montastraea spp. zone at San Bernardo Archipelago (Colombian Caribbean). Evaluating the abundance of organisms related to availability of different microhabitats, schemes of exclusive or preferential occupation of a particular elevated component were determined. These schemes, are discussed as initial cues that suggest the existence of benefic ecological relations. Samplings were performed at three stations. Four 20 meter transects were surveyed on each station, three during daytime and one during night. Presence and abundance of ophiuroids and microhabitat availability (area or volume) were quantified v i s u a l l y. Eleven types of microhabitats were identified. Vertical microhabitats and specially sponges and octocorals, were the most common substrate components at the study area. The ophiuroid community was composed by 22 morphotypes. Only Ophiopsila sp. 1 (with excavating habits) was restricted to one particular kind of substrate. Many other species did not use restrictedly any particular type of microhabitat, but used exclusively structures of particular characteristics (elevation, character or cripticity). T h e occupation of inferior surfaces of non-elevated components was determined by ophiuroid’s necessity of reaching cryptic conditions, and this necessity was linked to photosensitive species, or those especially vulnerable to predators, and to its consequent seek of protection. Elevated components and particularly 13 sponge species were characteristically occupied by Ophiothrix angulata - O. orstedii complex and by O . s u e n s o n i i. Sponges with different morphologies are discussed to bring differential advantages to dwelling ophiuroid species. It is suggested that a probable benefic ecologic relationship (not obligated) exists between these brittle-star species and some of the most frequently occupied sponge species. Nevertheless this must be appropriately tested by experimental work.

During the exploration of the soft calcareous bottoms of the continental shelf of La Guajira Department, 47 different species of sponges were identified in the classes Demospongiae and Calcarea. From bottom trawling carried out throughout the continental shelf on the bathymetric fringes of 10 and 50 m, it was found that the number of species is larger at 50 m depth, mainly in areas to the north and south where sand and mud sediments prevail. However, the patterns are not consistent in all the cases, owing to the low similarities between stations, based on the presence-absence of sponges, indicating a rather heterogeneous faunal composition. The soft bottoms allow the growth of non-sessile and sessile sponges; collected species show massive, incrusting ramified and spherical growth, all loosely attached but agglutinating large substratum fragments to which they hold.

The marine sponge Discodermia dissoluta is a source of the polyketide discodermolide, a potent antitumoral agent that has reached clinical trials in humans. In Santa Marta, where this species occurs at shallower depths than in other Caribbean areas, for the first time it was possible to study by SCUBA its ecological characteristics, distribution and abundance. By searching the base of the reefs (12-25 m in depth) it was found that this species is restricted to sites or bays with relatively low wave-exposure, dwelling predominantly in hard, horizontal to inclined substrata, generally exposed to light. Censuses carried out in 4 m-radius circles in sectors where this sponge occurs showed moderate densities (about 2-5 ind/50 m2) that, although not very low, do not support its commercial exploitation to obtain discodermolide. By locating individuals in the sampling space and using the point pattern distribution functions F, G and K, it was determined that individuals of D. dissoluta are aggregated in patches at scales from decimeters to a few meters. This pattern possibly arises from short-distance larval dispersal or fragmentation, both common in sponges. Size of censused individuals was estimated as projected area from digital photos, and expressed in volume by a regression calculated from the real volume of 30 collected individuals. In the population, small individuals (

The determination of antimitotic activity of organic extracts from marine organisms generates expectations on the isolation of substances with potential anticancer activity. The antimitotic activity of crude organic extracts from 15 marine sponges from the Colombian Caribbean coast were tested in vitro against embryos of the sea urchin Lytechinus variegatus. 80% of the species evaluated (Spirastrella coccinea, Myrmekioderma rea, Iotrochota imminuta, Halichondria sp., Petromica ciocalyptoides, Cinachyrella kuekenthali, Biemna cribaria, Oceanapia peltata, Xestospongia proxima, Oceanapia bartschi, Polymastia tenax y Dragmacidon reticulata) showed significant levels of inhibiting activity on the mitotic divisions at the first cellular phase of fertilized eggs. The extracts from Halichondria sp., P. ciocalyptoides and Xestospongia proxima disintegrate the cellular nuclei instantly. Extracts from Cribrochalina infundibulum showed an intermediate level of activity, while extracts from Desmapsamma anchorata and Myrmekioderma gyroderma showed no activity.

En ambientes litorales tropicales, el material organico en suspension favorece la presencia de organismos sesiles filtradores, como las esponjas, sobre los predominantemente fototroficos como las algas y los corales. En el area de Santa Marta, Caribe colombiano, la productividad se incrementa por pulsos alternantes de afloramiento costero y descarga continental, resultando en una importante diversidad y abundancia de esponjas. Las especies del genero Ircinia (I. campana, I. felix e I. strobilina) son conspicuas y abundantes en los biotopos rocoso-coralinos del area. Para establecer la influencia de las condiciones ambientales predominantes sobre la distribucion de las tres especies, sus densidades, tallas, preferencia de microhabitat, forma, color, y presencia de signos de depredacion, epibiontes e interacciones agresivas con los vecinos, se compararon en profundidad (5-20 m) entre dos localidades contrastantes por sus regimenes de turbidez y turbulencia. Al igual que en otras areas del Caribe, el orden de abundancia general fue Ircinia felix>I. strobilina>I. campana, lo cual indica diferencias intrinsecas en sus estrategias e historias de vida. En relacion aparente con la cantidad de materia organica en suspension, fuente principal de alimento de estas especies, se encontro que la densidad y el tamano de los individuos de Ircinia fueron significativamente mayores en la localidad de aguas turbias y relativamente calmadas, en comparacion con la localidad de aguas mas claras y mayor turbulencia; la densidad fue tambien mayor en aguas someras y medias en la localidad de mayor turbidez. En relacion con el efecto que ejercen las fuerzas hidrodinamicas sobre la forma de los organismos sesiles, las formas bajas preponderaron a todas las profundidades en la localidad mas turbulenta, y fueron proporcionalmente mas frecuentes en aguas someras que en aguas profundas en la localidad mas calmada, lo cual quizas se debe a la ocurrencia esporadica de fuertes mares de leva en el area. En estas especies la intensidad del color decrecio con la disminucion de la luz (con la profundidad y comparando microhabitats expuestos y cripticos). La menor penetracion de luz en la localidad con la mayor turbidez tambien implico una ligeramente mayor proporcion de individuos de colores claros en aguas someras. En las dos localidades, estas especies se encuentran preferentemente en posicion expuesta a la luz y sobre sustrato duro, aunque I. strobilina puede encontrarse frecuentemente anclada en cascajo. Los signos de depredacion y la epibiosis fueron raros, en correlacion con las defensas quimicas ya conocidas. Aunque en el muestreo no se detectaron casos claros de competencia por espacio, en el area de estudio estas especies pueden recubrir parcialmente tejido coralino.

The North-West of Urabá Gulf in the Southern Caribbean supports a variety of coral reef zones in conditions of high turbulence and fluctuating turbidity and salinity. Sponge composition and density were surveyed and their relationship with physical and structural features of the reef zones were analyzed. In total, 65 demosponges and 1 calcareous sponge species were encountered along belt transects (20 m2) on 11 stations between 1 and 17 m in depth. Sponge density in Urabá tended to be higher than in other areas with water conditions optimal for coral reef development (i.e. Roncador, Serrana and Quitasueño remote oceanic atolls in the SW Caribbean, Colombia) due possibly to higher concentrations of organic suspended materials discharged from rivers. Nevertheless, this effect was not reflected in the Urabá‘s species richness as just a limited number of species (Niphates erecta, Iotrochota birotulata and Mycale laevis) had high densities. Multivariate analyses showed that sponge community composition varies along a depth gradient and across habitats (coral and geomorphological zones), similar to the patterns observed in other Caribbean areas. However, marked taxonomic differences between shallow (6 m) zones and the great increase of the sponge density below just 6 m, seem to be a unique feature of Urabá. The absence of many species and the low abundance of sponges in shallow zones (< 6 m) may be due, not only to the variables associated to low depth, like turbulence, which is periodically very strong, but also to great fluctuations in surface salinity due to discharges of the Atrato and other local rivers. The shallow and deep stations that had low sponge richness and density, showed the greatest urchin densities (especially Echinometra viridis); therefore, it is possible that these urchins may be playing an additional controlling role on sponge populations.

First steps towards cellular localization of (+)-discodermolide, a potent antitumoral poliketide biosynthesized by the Caribbean marine sponge Discodermia dissoluta. Identification of bioactive metabolite cell producers allow driving cell culture experiments for in vitro production, just as elucidation of the possible physiologic function of metabolites. The Caribbean marine sponge Discodermia Discodermia dissoluta, (+)-Discodermolide, Cell dissociation, Anticancer agent.dissoluta produces the polyketide (+)-discodermolide, a potent antitumoral that has reached clinic trials in humans. In this research, progress was made in identifying the producing cells by cell dissociation, separation into fractions by centrifugation on Percoll® density gradients, and detection of (+)-discodermolide presence by thin layer chromatography. The fractions recovered showed cells of different morphological characteristics, including cyanobacteria, filamentous bacteria, choanocytes, archaeocytes, among others. It was possible to identify an irregular but consistent pattern of (+)-dicordemolide production in the fractions that contained one or more kind of sponge granular cells, indicating that metabolite production seems to be related to the sponge and not with the associated microorganisms., Identificar la célula productora de un metabolito bioactivo permite enfocar los esfuerzos de cultivo celular para su producción in-vitro, así como elucidar la posible función fisiológica del metabolito. La esponja marina del Caribe Discodermia dissoluta produce el policétido (+)-discodermólido, un potente antitumoral que ha llegado a fase clínica de investigación en humanos. En este trabajo se avanzó en la identificación de las células productoras mediante disociación celular, separación en fracciones por centrifugación en gradientes de densidad de Percoll ® y detección de la presencia de (+)-discodermólido mediante cromatografía de capa delgada. Las fracciones mostraron células de diferentes características morfológicas, entre las que se encuentran cianobacterias, bacterias filamentosas, coanocitos, arqueocitos, entre otras. Se pudo identificar un patrón irregular pero consistente de producción de (+)-discodermólido en las fracciones que contenían uno o más tipos de células granulares de la esponja, indicando que la producción del metabolito parece estar asociada con la esponja y no con los microorganismos asociados.

Las superficies sumergidas en el mar son densamente colonizadas por bacterias y sus interacciones, tales como la inhibicion del crecimiento, son importantes para determinar el desarrollo de comunidades bacterianas, como tambien de posteriores etapas de la macroepibiosis. Para determinar el potencial de interaccion entre bacterias de las biopeliculas de esponjas, se realizaron ensayos de actividad de inhibicion in vitro de crecimiento entre cepas bacterianas aisladas de superficies con diferente grado de macroepibiosis, de las esponjas Aplysina insularis (limpia), Aplysina lacunosa (con macroepibiosis) y de la superficie calcarea de la concha del molusco bivalvo Donax sp. El porcentaje total de interaccion antagonica entre estas cepas bacterianas fue del 64 %; las cepas bacterianas aisladas de superficies limpias inhibieron el crecimiento de cepas provenientes de superficies muy colonizadas en proporciones cercanas a 1:1. Cepas de superficies no colonizadas tuvieron mayor frecuencia de interacciones antagonicas. Se propone la interaccion bacteriana antagonica como posible mecanismo de regulacion del crecimiento poblacional y de esta forma del desarrollo de etapas subsecuentes de la macroepibiosis

Sessile organisms can use physical, chemical, and biological mecanisms to control, avoid or induce epibiosis. The antifouling capacity of crude organic extracts from the marine sponges Cribrochalina infundibulum (=C. vasculum) and Biemna cribaria, was evaluated. Natural concentrations of sponges extracts were added to agar based gels and deployed in the field during 28 days, to offer substrate to natural epibiotic community. Colonization extent was then compared with control gels without extracts. Extracts from both sponges significatively inhibited the colonization of most of epifaunal organisms. B. cribaria was found to be more effective than C. infundibulum; moreover its extract lixivation was lower with a longer inhibitory action.

Encrusting and excavating Caribbean sponges Cliona aprica, C. caribbaea and C. tenuis (Hadromerida: Clionaidae) aggressively undermine and displace live coral tissue. To estab- lish 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. Mas- sive 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.

Para evaluar el papel del sedimento sobre la alta produccion primaria de una laguna costera tropical, Cienaga Grande de Santa Marta (Caribe, Colombia), se midio el flujo de nitrogeno y fosforo (inorganico disuelto, particulado) en la interfase agua-sedimento. Entre 1996 y 1997 se incubaron nucleos de sedimento en el laboratorio y se ubicaron trampas de particulas en campo, en dos estaciones contrastadas por la influencia de aguas dulces y marinas. Los flujos tuvieron una alta variabilidad espacial y temporal pero no mostraron esquemas claros en su direccion e intensidad en relacion con las caracteristicas de los sedimentos o de la columna de agua de las dos estaciones. Esto evidencia una alta heterogeneidad en la naturaleza y actividad de los organismos responsables de los procesos biogeoquimicos. Los sedimentos liberaron en promedio al agua 1643 μmolNm -2 d -1 de amonio y 1.3 μmolNm -2 d -1 de nitrito, aportando a la columna el 1.90-3.41 % de lo requerido en la produccion. En condiciones oxicas normales, el sedimento actuo como sifon del fosforo, absorbiendo en promedio 178 μmolPm -2 d -1 disueltos y recibiendo 36277 μmolPm -2 d -1 particulados. Pero el fosforo se mantiene en exceso en la columna, en parte, por liberacion desde el sedimento en condiciones anoxicas durante florecimientos microalgales masivos. Flux of nitrogen and phosphorus at the water-sediment boundary in a tropical coastal lagoon (Cienaga Grande de Santa Marta, Colombian Caribbean) To evaluate the role of the sediment in the high primary production of a tropical coastal lagoon, "Cienaga Grande de Santa Marta" (Caribbean, Colombia), the flux of nitrogen and phosphorous (dissolved, inorganic, particulate) in the water-sediment boundary was measured. From 1996 to 1997 sediment cores were incubated in the laboratory and sediment traps were deployed in the field, in two sites contrasted by the influence of fresh and marine waters. The fluxes were spatially and temporally highly variable but did not show clear patterns in their direction and intensity in relation to the sediment or water column characteristics at the two sites. This evidences a high heterogeneity in the nature and activity of the organisms responsible of the biogeochemical processes. The sediments liberated to the water on average 1643 μmolNm -2 d -1 of ammonium and 1.3 μmolNm -2 d -1 of nitrite, offering 1.90-3.41 % of the amount required in production. In normal oxic conditions, the sediment acted as a phosphorous sink, absorbing on average 178 μmolPm -2 d -1 dissolved and receiving 36277 μmolPm-2d-1 particulate. But the phosphorous is maintained in excess in the column, in part, due to its liberation from the sediment in anoxic conditions during massive algal blooms.

During a study of the spatial and temporal patterns of desmosponge (Porifera, Demospongiae) recruitment on rocky and coral reef habitats of Santa Marta, Colombian Caribbean Sea, preliminary attempts were made to estimate actual settlement rates from short-term (1 to a few days) recruitment censuses. Short-term recruitment rates on black, acrylic plastic plates attached to open, non-cryptic substratum by anchor screws were low and variable (0–5 recruits/plate in 1–2 days, sets of n=5–10 plates), but reflected the depth and seasonal trends found using mid-term (1 to a few months) censusing intervals. Moreover, mortality of recruits during 1–2 day intervals was low (0–12%). Thus, short-term censusing intervals can be used to estimate actual settlement rates. To be able to make statistical comparisons, however, it is necessary to increase the number of recruits per census by pooling data of n plates per set, and to have more than one set per site or treatment.

Aunque la temperatura superficial del mar se ha considerado como la variable ambiental con mayor incidencia en el blanqueamiento coralino, se ha encontrado que otras variables también intervienen en este fenómeno, modificando la susceptibilidad de los arrecifes y generando diferencias espaciales. En el Caribe colombiano se estudiaron las variables de temperatura superficial del mar, clorofila, turbidez, caudal de ríos, vientos y nubosidad durante los blanqueamientos coralinos en cuatro localidades. Mediante análisis multivariados y de valores extremos, se encontró que los blanqueamientos han ocurrido principalmente en el segundo semestre del año a nivel de cuenca, de costa continental y local. En los arrecifes costeros, la turbidez del agua por la entrada de agua dulce ha sido determinante en el blanqueamiento, mientras que en los oceánicos lo ha sido el aumento de temperatura. Así, fenómenos macroclimáticos como La Niña influyen en la ocurrencia de los blanqueamientos cerca de la costa. Los datos muestran que es necesario monitorizar de forma más continua el blanqueamiento y que las zonas más expuestas son las Islas del Rosario y San Bernardo. While sea surface temperature has been considered the environmental variable with the greatest impact on coral bleaching, other variables also modify the susceptibility of reefs and generate spatial differences of this phenomenon.In four locations in the Colombian Caribbean, sea surface temperature, chlorophyll, turbidity, flow of rivers, winds and clouds were studied during coral bleaching. Using a principal components and maximum values analysis, we found that bleaching occurred mainly in the second half of the year, at three spatial levels: basin, coastal zone andlocal. In the coastal reefs, water turbidity by freshwater input was determinant in bleaching, while in the open ocean, temperature was the determinant variable. Thus, macroclimatic phenomena like La Niña influence the occurrence of bleaching near the coast. The data backed the need to increase the frequency of bleaching monitoring and showed that the most exposed areas are El Rosario and San Bernardo islands. © 2014. Acad. Colomb. Cienc. Ex. Fis. Nat. All rights reserved.

Se realizó una clasificación numérica de 21 estaciones de monitoreo del sistema laguno-estuarino comprendido por la Ciénaga Grande de Santa Marta y el Complejo Pajarales, de acuerdo a su similaridad en el comportamiento de la salinidad del agua. Se utilizó información quincenal comprendida entre enero de 1987 y octubre de 1991. Debido a la estructura de autocorrelación de los datos fue necesario emplear los modelos ARIMA de series de tiempo en primer lugar, y posteriormente aplicar una técnica de clasificación normal con los coeficientes de la representación infinita AR calculados para cada estación. Los resultados del análisis fueron coherentes con las hipótesis planteadas acerca de la distribución de la variable en el sistema. A numerical classification of 21 monitoring stations of the lagoonal-estuarine system comprised by the Ciénaga Grande de Santa Marta and Pajarales complex was carried out according to their similarity in water salinity behavior. Biweekly data from January 1987 to Octuber 1991 was used. Due to the autocorrelation structure of the data, it was necessary to use first time series ARIM A models followed by normal cluster analysis of the AR coefficients of infinite representation calculated for each station. The results were coherent with hypotheses concerning the distribution of the variable in the system.

Se analizaron las variaciones día-noche y entre días en la composición del zooplancton superficial y se relacionaron con parámetros ambientales en la bahía de Santa Marta, Caribe colombiano, mediante análisis de componentes principales. Los muestreos se realizaron cada cuatro horas en tres días diferentes entre agosto y octubre de 1989. La mayor variación en abundancia (primer componente principal) se manifestó en un aumento sobre el promedio en casi todos los grupos en el atardecer y las horas de la noche. Esta variación resultó significativamente correlacionada en forma inversa con la intensidad de la luz incidente y se interpretó como un reflejo en superficie del fenómeno de migración vertical. De otro lado, en el segundo y tercer componente principal se evidenciaron las diferencias entre días para los grupos y dentro de los grupos; las que ocurrieron entre el primer día de muestreo y los otros dos fueron resaltadas por el segundo componente, y resultaron correlacionadas negativamente con la temperatura y positivamente con los nitratos disueltos. Estas se interpretaron como resultado de movimientos de masas de agua de características fisicoquímicas y composición zooplanctónica diferente sobre el sitio de muestreo. Sin embargo, no se pudo descartar que hubiera una asociación estrecha entre estos parámetros y cambios en los movimientos migratorios. Day-night and between-day variation in surficial zooplankton composition and its relationship to environmental parameters were analyzed in the Santa Marta Bay, Colombian Caribbean, by Principal Components Analysis. Sampling was carried out every four hours in three different days between August and October 1989. The greatest variation in abundance (first principal component) was due to an increase over the mean in most groups at nightfall and during night hours. This variation was inversely and significantly correlated with incident light intensity, and was interpreted as consequence of the vertical migration out of the surface zone. On the other hand, the second and third principal components showed differences amog days for groups and within groups; those that existed in the first sampling day with respect to the other two were highlighted by the second component, and were negatively correlated with temperature and positively correlated with disolved nitrates. These results were interpreted as a consequence of movements of water masses with different physical-chemical characteristics and zoo-plankton composition over the sampling site. However, a case of close association between these parameters and the changes in migrating movements could not be ruled out.

It is known that the encrusting and excavating Caribbean sponge Cliona delitrix may increase its abundance near sources of sewage. To ascertain whether its current conspicuousness in leeward reefs of San Andrés Island (SW Caribbean, Colombia) is related to organic pollution from local raw sewage discharges, quantitative data on density and cover of this sponge and other benthic components was obtained from belt and line transects at seven stations along the shallow (5-10 m deep) terrace. Coral mucus was sampled to quantify Escherichia coli bacteria, as an approximate indicator of sewage plume influence on benthic biota. A negative multiplicative regression between amount of E. coli in coral mucus and distance from the main raw sewage outlet demonstrated the domestic-wastes origin of the bacteria. Whereas significant E. coli counts occurred only up to 1-2 km from sewage sources, overall sewage influence may extend further as moderate C. delitrix abundances occurred throughout the West shallow terrace of San Andrés, apparently associated to the overall nutrient enrichment from sewage. C. delitrix abundances were lower in the Southwest, farthest from sewage influence, and generally increased towards sewage sources, but decreased near the main sewage outlet. Close to sewage sources, any positive effect on the sponge brought about by the increase in suspended organic matter is probably outweighed by the negative effect that excessive sedimentation has on the sponge itself, and on the quantity and quality of substratum available for settlement.