Rosario Islands Research Articles

Assessment and management of coastal erosion in the marine protected area of the Rosario Island archipelago (Colombian Caribbean)

By utilizing historical satellite image databases, it was possible to assess the rates of coastal retreat in the Grande, Rosario, and Tesoro Islands from 2010 to 2021, due to the influence of climatic variables. It was discovered that the three islands have lost 0.4%, 1.6%, and 9.3% of their landmass, respectively. The notable increase in sea level rise, which has risen 6.2 mm/year since 2010, has emerged as the primary driving factor in the magnitude of erosion by altering the wave transformation patterns in shallow waters. This enables the wave trains to maintain more energy and intensify their height in surf zones, particularly during the dry season, where the wave height has increased by 12%. At the same time, the intensity of longitudinal currents has increased due to the new wave dynamics, leading to changes in the coastlines. Areas characterized by a coastal geomorphology of terraces and beaches, such as Tesoro Island, were found to be the most affected, unlike the cliffs of Grande and Rosario Islands. The study also revealed a lack of policies and concrete actions aimed at mitigating erosion in the coral islands of the Colombian Caribbean. Thus, a set of guidelines is proposed as a starting point to address this issue.

Mercury assessment in invasive Lionfish Pterois (Oken, 1817) from marine protected areas in the Colombian Caribbean

Lionfish (Pterois spp.) are invasive species reported since 2009 in the Corales del Rosario y San Bernardo National Natural Park in the Caribbean. Their capture and consumption are strategies to control their dispersion and limit ecological damage. The natural park is influenced by the vicinity of Cartagena's residential, industrial, and touristic activities, as well as sediments loaded with mercury from the Dique Channel. For the first time, total mercury levels in muscle from 58 lionfish were determined, with values ranging from 0.01 to 0.38 μg/g (mean = 0.11 ± 0.01 μg/g). Fish length ranged from 17.4 to 44.0 cm (mean = 28.0 ± 0.63 cm). Mercury levels did not increase proportionally to fish length for pooled data, but the relationship was significant for specimens from Rosario Island. Mercury levels comply with legislation for fish consumption, but the risk to human health may appear if it occurs daily. Therefore, precautionary approach and a permanent monitoring strategy are strongly advised.

Macroalgae associated with aerial roots of <i>Rhizophora mangle</i> in Islas del Rosario, Colombia, Southwestern Caribbean

The roots of the red mangrove, Rhizophora mangle, provide a nursery habitat for many species, due to the tridimensional structure they provide, which delimits an area difficult to access to large predators. Moreover, they provide a hard substrate for many benthonic species, which attach to the roots and contribute to the tridimensional structure of the ecosystem. Among these organisms, there are several macroalgae, which contribute to the primary productivity of the ecosystem and provide food and shelter to herbivores. In the present study we identified the macroalgae associated with the roots of Rhizophora mangle, in Cholón beach, Rosario Islands National Park, Caribbean Colombia. We report a total of 36 species of macroalgae: 21 Rhodophyta, eleven Chlorophyta, and four Phaeophyceae. Of these, 19 are new records for the islands, and six are new records for Colombia. This is the first study on the macroalgae associated with mangrove roots in the Colombian Caribbean, and it highlights both the high diversity of the marine flora of the Southwestern Caribbean, as well as the paucity of studies on the topic.

Competitiveness in insular regions: case of isla grande in the archapelago of islas del rosario, Cartagena, Colombia

This article is based on a study whose objective was focused on identifying the variables and key actors with the greatest impact on the competitiveness of a large island in the island region of the Rosario Islands in Cartagena, Colombia. The implemented methodology is exploratory, based on the qualitative paradigm, and had three phases. The first was developed through a competency diagnosis that was achieved from observations and discussions with the community. The second phase was the identification of the actors to determine how they affect the community. The final phase included the identification of probabilistic cross impacts. The main findings of the research include that the main external factor is the sociodemographic variable. In addition, the environmental variable directly influences competitiveness. The following internal variables of the large island community were identified: ecotourism, poverty and misery index, exploitation of natural resources, social innovation, tourism potential and generational change. Finally, it is necessary to perform immediate actions in favour of the development of competencies. Some of these actions include promoting the destination as ecotourism and developing campaigns to raise awareness of the importance of the island for natural resources and that these resources should be conserved.

Current status of Acropora palmata and Acropora cervicornis in the Colombian Caribbean: demography, coral cover and condition assessment

Acropora provides an example of reef degradation, as evidenced by population reductions in Caribbean reefs. However, data on the current status of Acropora populations in Colombia are lacking. In this study, reef habitats were surveyed for Acropora palmata and Acropora cervicornis throughout the Colombian Caribbean, and the size structure, coverage and colony conditions of their populations were evaluated. Acropora palmata size classes were negatively skewed, indicating low recruitment. This species exhibited a patch-type distribution around Tayrona, Isla Fuerte and Isla Arena; these localities exhibited the highest cover among the surveyed regions. The lowest coral cover was recorded for the Rosario Islands. Healthy colonies were dominant; however, disease and damselfish territories were common. The size class data of Acropora cervicornis indicated the persistence of small colonies; however, no recruits were observed. The distribution was dispersed, with important patches and the highest cover observed around the Uraba Gulf and Rosario Islands. Overall, the cover was lower than 10%. Few healthy colonies were observed, and macroalgae and sponges were common. Conservation and management efforts are required for both species; for Acropora palmata, efforts targeting the Rosario Islands are needed, whereas Acropora cervicornis is in critical condition throughout the Colombian Caribbean.

Primer registro del género Carminodoris Bergh, 1889 (Gastropoda: Opisthobranchia: Nudibranchia: Doridoidea: Discodorididae) en el Caribe colombiano

In the Atlantic Ocean, there are only two records of nudibranchs belonging to the genus Carminodoris Bergh, 1889 (Discodorididae). This work describes and illustrates the first record of a nudibranch belonging to this genus in the Colombian Caribbean, upon a sample collected in San Martin de Pajarales Island, Rosario Islands, Cartagena, Colombia. Morphological and anatomical attributes of the studied specimen were compared with those of Atlantic (Carminodoris hansrosaorum and C. madibenthos), also with those reported for the Pacific (C. nodulosa, C. grandiflora, C. bramale, C. flammea, C. bifurcata, C. armata and C. estrelyado). The studied sample differs from the other species by its size (74 mm), distinctive morphological patterns (foot, tubercles, branchial plume, mantle, jaw and radular formula). This is the first report of this genus in the Western Caribbean and it might be a new species, yet to be confirmed, with additional anatomical and molecular studies.

Environmental and cultured cyanobacteria as sources of Aedes aegypti larvicides

In tropical countries, the control of the mosquito Aedes aegypti is a public health priority due to its role as a vector of important viral diseases. Marine cyanobacteria are recognized as abundant sources of bioactive compounds, and they constitute a potential source of insecticides useful for controlling mosquito populations and preventing epidemic outbreaks. We collected 30 benthic cyanobacterial mats in Providencia and Rosario islands (in the Colombian Caribbean) belonging to the genera Phormidium, Symploca, Oscillatoria, Lyngbya, Pseudoanabaena, Leptolyngbya, Moorea, and Dapis. Fractions of organic extracts from the most abundant environmental samples were evaluated in three bioassays, assessing (i) larvicidal activity against A. aegypti, (ii) toxicity against the brine shrimp (Artemia salina) nauplii, and (iii) acetylcholinesterase inhibition. Non-polar fractions exhibited larvicidal activity. The polar fraction from one Dapis pleuosa extract showed larvicidal activity without being toxic against A. salina nauplii. Extracts from Moorea producens exhibited the greatest toxicity against A. aegypti larvae and A. salina nauplii. From 23 cultured cyanobacterial samples, only five grew under laboratory conditions and produced enough biomass to yield organic extracts. Of these, three extracts showed strong larvicidal activity, but only the extract from Phormidium tenue showed reduced toxicity against A. salina nauplii. We detected variation among the chemical profiles and larvicidal activity of cyanobacterial consortia depending on sites and dates of collection. Our findings suggest that despite variation in chemical profiles, extracts of marine benthic cyanobacteria can be further developed as effective control agents against insect vectors, in their larval stages. The culture of marine benthic cyanobacteria needs to be further explored to provide enough biomass leading to the identification of bioactive compounds with public health applications.

Mangrove responses to droughts since the little ice age in the Colombian Caribbean

Mangroves are ecosystems that are seriously threatened by climate change, particularly sea level rise and an increase of droughts. They are resilient to short droughts but their response to longer ones remains arguable. In this work, we studied the responses of R. mangle dominated forests on a carbonate island (El Rosario Island) to climate anomalies and their drivers at inter-annual, decadal and inter-decadal scales during the last centuries. Palynological analysis of a sediment core retrieved from an R. mangle dominated forest was used to reconstruct vegetation changes during the last 400 years. Time series, Multi-taper spectral, Fourier and correlation analyses of PDO, AMO and ENSO series were performed to identify the matches between these series and mangrove changes during this time. The pollen record showed the influence of coastal dynamics on mangrove vegetation changes on a local scale and the influence of climate on a regional one. Changes in coastal vegetation and mangroves were influenced by beach ridge formations and lagoon closing, which were, in turn, determined by shifts in wave and wind intensity. The simultaneous diminution of both types of vegetation were related to both natural (earthquake and extreme droughts) and anthropogenic disturbances. Our results also showed the replacement of the Rhizophora dominated forest by an Avicennia dominated forest when droughts became longer. The peaks of Rhizophora pollen percentages identified along the pollen record showed a 64 year recurrence cycle that dominated during the Little Ice Age (1610–1862) and a 32 year cycle during the Current Warm Period (1866–1954). While the first cycle was positively correlated with the warm phase of PDO and AMO time series, the second cycle showed a negative significant correlation with PDO, AMO and ENSO time series. During warm periods, mangroves were stressed by droughts, but as these cycles became shorter, mangroves could recover more rapidly. From 1954 to the present, no significant correlations were observed between vegetation changes and climate drivers, which is likely related to the increased anthropogenic disturbance beyond that period of time. Our results show the high resilience of mangroves to cyclic climate changes that involve droughts, winds and sea level rises but low recovery and species turnover with extreme and longer droughts and strong anthropogenic disturbances.

Experimental Approaches for the Evaluation of Allelopathic Interactions Between Hermatypic Corals and Marine Benthic Cyanobacteria in the Colombian Caribbean

Blooms of marine benthic cyanobacteria are recurrent in several locations at the Colombian Caribbean. In these events, cyanobacteria grow over the substrate and benthic organisms although their effect has not been fully assessed. This study evaluated interactions between cyanobacteria and hermatypic corals, in order to identify any deleterious effects that could be related to allelopathic mechanisms. Organic extracts from cyanobacteria collected in San Andres, Old Providence and Rosario islands were tested against embryos of the reef-building coral Orbicella annularis. The indirect effect of cyanobacterial extracts was also assessed by resuspending the extracts in seawater and monitoring polyp retraction and recovery of the coral Madracis mirabilis (=auretenra). Additionally, the effect of direct contact between cyanobacterial extracts and the coral Porites porites was assessed by incorporating cyanobacterial extracts into PhytagelTM gels and placed in direct contact with the coral. After 24, 48 and 72 h of exposure, chromatographic profiles of associated zooxanthellae was evaluated by HPLC. A deleterious effect on the zooxanthellae was evidenced by an increase in pheophytin, a degradation product from chlorophyll. The competitive abilities of algae and cyanobacteria should be considered as a constraint to reef restoration initiatives. Cyanobacteria have the ability to compete with corals due to their growth rates, defenses against herbivory and potentially allelopathic mechanisms.

Sedimentary records of extreme wave events in the southwestern Caribbean

High-energy events in the Caribbean Sea include hurricanes, tropical storms, cold fronts and tsunamis. El Rosario Archipelago, located on the Colombian Caribbean shelf (SW Caribbean) consists of a set of ancient and successive coralline formations, uplifted by tectonic and diapiric activity. We undertook an integrated analysis of instrumental climate records and sediment records from a beach ridge system, a reef lagoon and a mangrove lagoon in the Archipelago, to determine whether historical extreme weather events influenced the coastal geomorphology and reef sedimentation. Statistical analysis of historical extreme winds and waves was accomplished using ERA-Interim reanalysis data. Extreme sea-level events were identified with calibrated data from the nearest tide gauge. Sediments from the reef and mangrove lagoon were dated using 210Pb and 14C. Beach ridges were dated indirectly thorough their relationship with the closure of the mangrove lagoon. The eroding capacity of the historical extreme waves (i.e. maximum grain size that could be entrained by the orbital velocity of the waves) was compared with the grain sizes present in the deposits, and foraminifera species helped to determine the provenance of those deposits. Storms typically occur during the dry season associated with cold fronts. Foraminifera and coral fragments indicated that beach ridges were supplied with sediment that eroded from ancient terraces. In the reef lagoon, a 56-cm-thick unit of coarse coral and shell debris, grading to a finer sediment, represents a major high-energy event that occurred after ca. 1655 CE. This event was also recorded by the beach ridges. The probable explanation for this high energy unit is that a strong event carried coarse sediments into the lagoon, with subsequent reworking by minor events, such as those reported in the historical record. Two tsunamis occurred in the Caribbean after 1655, but the associated waves reaching the area were not strong enough to deposit the coarser clasts of the unit. Thus, coarser material was probably delivered to the lagoon as a consequence of sudden diapiric and/or tectonic activity. Our data show that major storms and other high-wind, extreme-wave events shape the beach ridges on Rosario Island, every 70 years. The findings suggest that if global climate change increases the frequency and/or magnitude of major storms and other high-wind, extreme wave events that impact the Caribbean coast of Colombia, then El Rosario Archipelago will be susceptible to future, significant landscape transformations.

Implementación de las herramientas tecnológicas como estrategia pedagógica

The objective of this research was to implement technological tools to improve the pedagogical process in the C.E.D. Rural Girls Rosario Island. The development of the study is framed in authors like Moreira, Rodríguez, under a quantitative view, from the analytical empirical paradigm and with a descriptive scope. The students participating in the study were the students and teachers of the IED Mario E Pereira. For the collection of information, a survey with closed questions was used. As conclusions, it is highlighted that the results allow to show that the students know about the technologies and that they already make art of the students 'and teachers' lives, that motivates them to carry out activities using them and that they manipulate with greater favoribility some of these tools, so Therefore, the school must base its practice on the implementation of digital portals to which the educational population has access

An environmental magnetism approach to assess impacts of land-derived sediment disturbances on coral reef ecosystems (Cartagena, Colombia)

We used environmental magnetism methods to study recently deposited marine sediments from the estuarine ecosystems on the Caribbean coast of Colombia. Cartagena region has undergone an increasing sediment load during the last decades via sediment plumes from Magdalena River and its distributary man-made channel. Concentration dependent magnetic parameters show an increasing abundance of ferrimagnetic minerals on the uppermost sediments on sites located close to the continent (remanent magnetization SIRM = 5.4–9.5 × 10−3Am2 kg−1) as well as faraway sites (SIRM = 0.5–1.7 × 10−3Am2 kg−1 near Rosario Islands coral reef complex). The magnetic grain size and mineralogy along the cores are variable, showing the dominance of the magnetite-like minerals (remanent coercivity Hcr = 34.3–45.3 mT), with a minor contribution of high-coercivity minerals (Hcr = 472–588 mT). In addition, there is a moderate enrichment of elements Cu, Mo, and Zn (enrichment factor EF = 1.5–3.8) that indicates the additional land-derived contribution on sediments. The environmental magnetism approach, which shows significant signals of magnetic minerals and trace elements, is a reliable tool to prove the presence of continental sediment supply in coral reef ecosystems.

Coral reefs chronically exposed to river sediment plumes in the southwestern Caribbean: Rosario Islands, Colombia

Politicians do not acknowledge the devastating impacts riverine sediments can have on healthy coral reef ecosystems during environmental debates in Caribbean countries. Therefore, regional and/or local decision makers do not implement the necessary measures to reduce fluvial sediment fluxes on coral reefs. The Magdalena River, the main contributor of continental fluxes into the Caribbean Sea, delivers water and sediment fluxes into the Rosario Islands National Park, an important marine protected area in the southwestern Caribbean. Until now, there is no scientific consensus on the presence of sediment fluxes from the Magdalena River in the coral reefs of the Rosario Islands. Our hypothesis is that high sediment and freshwater inputs from the Magdalena have been present at higher acute levels during the last decade than previously thought, and that these runoff pulses are not flashy. We use in-situ calibrated MODIS satellite images to capture the spatiotemporal variability of the distribution of suspended sediment over the coral reefs. Furthermore, geochemical data are analyzed to detect associated sedimentation rates and pollutant dispersion into the coastal zone. Results confirm that turbidity levels have been much higher than previous values presented by national environmental authorities on coral reefs off Colombia over the last decade. During the 2003–2013-period most of the Total Suspended Sediments (TSS) values witnessed in the sampled regions were above 10mg/l, a threshold value of turbidity for healthy coral reef waters. TSS concentrations throughout the analyzed time were up to 62.3mg/l. Plume pulses were more pronounced during wet seasons of La Niña events in 2002–2003, 2007–2008, and 2009–2010. Reconstructed time series of MODIS TSS indicates that coral reef waters were exposed to river plumes between 19.6 and 47.8% of the entire period of analysis (2000−2013). Further analyses of time series of water discharge and sediment load into the coastal zone during the last two decades show temporal increases in water discharge and sediment load of 28% and 48%, respectively. 210Pb dating results from two cores indicate sedimentation rates of ~0.75cm/y of continentally exported clastic muddy sediments that are being deposited on the carbonatic shelf. The cores contain sediments with heavy metals and their concentrations are frequently above the ecologically accepted standards. Overall, the last decade has witnessed stronger magnitudes in fluvial fluxes to the coastal region, which probably coincide with associated declines in healthy coral cover and water quality. Our results emphasize the importance of local stressors, such as runoff and dispersion of turbid plumes, as opposed to ocean warming, disease and hurricanes, which have played a larger role on other coral reefs in the Caribbean. Coral reef management across the southwestern Caribbean, a coastal region influenced by continental fluxes of numerous rivers flowing from the Andes, may only be effective when land and marine-based stressors are simultaneously mitigated.

EXPLOTACIÓN, USOS Y ESTADO ACTUAL DE LA CIGUA O BURGAO CITTARIUM PICA (MOLLUSCA: GASTROPODA: TROCHIDAE) EN LA COSTA CONTINENTAL DEL CARIBE COLOMBIANO

The West Indian topshell, Cittarium pica is a common and conspicuous gastropod that thrives in Caribbean intertidal rocky shores and has been used for food by men since pre-Columbian times. Although, the exploitation of this resource is practiced only by artisanal fishermen and mainly for self-consumption, its abundance has noticeably reduced in the last ten years, so the species has been included in the endangered animal lists of several Caribbean countries, including Colombia. The present study was carried out to assess the current status of the population of C. pica along the Colombian Caribbean mainland and to describe the overall exploitation level and uses of this resource in recent times. In order to achieve so, Colombian Caribbean coast was divided into five zones according to the established distribution range of the species: 1-Urabá chocoano, 2-Isla Fuerte, 3-Cartagena and Rosario Islands, 4-Santa Marta and Tayrona Natural National Park, 5-La Guajira. In each one of the zones opinion polls among local inhabitants were conducted. A series of samples from representative stations were obtained in order to determine the abundance, density and size structure of the C. pica population. The fishing pressure on the resource is different between the sectors, being greater in Santa Marta and Tayrona Natural National Park, Urabá chocoano, and Cartagena and Rosario Islands. The main use given to C. pica is as dietary complement of the local population, but the flesh and shells are commercialized at times. Shells are sold to artisans and used for “souvenirs” and handcraft manufactures. The mean ecological density of C. pica in the entire study area was 5.38 Ind/m2 (± 0.82), with significant differences between sectors and between the stations within a sector as well. The size structure of the population (mean size = 25.08 mm ± 4.71, mode = 11.10 mm) suggests that in general the resource is being over-exploited in the Colombian Caribbean. This result confirms that C. pica is an endangered species in Colombia and its status as “vulnerable” in the red list should be maintained.

ANNUAL SKELETAL EXTENSION OF TWO REEF-BUILDING CORALS FROM THE COLOMBIAN CARIBBEAN SEA

The skeletal growth of the scleractinian corals Diploria labyrinthiformis (Linnaeus 1758) and Montastraea annularis (Ellis and Solander 1786) from Isla Grande (north of Rosario islands), Colombian Caribbean, was determined from annual extension increments revealed by X-radiography of 4-6 mm thick slabs obtained along the axis of maximum growth. The skeletal extension average rate for the last 22 years for D. labyrinthiformis was 3.8 mm year-1 (SE 0.10; N = 87). The correlation between growth of D. labyrinthiformi s and hours of sunlight was significantly negative. The annual variances of sunlight enhanced annual statistically significant differences of growth in this species. M. annularis showed an average extension growth of 10.6 mm year-1 (SE 0.32; N = 55) during the last 14 years. The increase of M. annularis growth was coincident with the end of nearby dredging activities as well as the decrease of nutrient levels. Nevertheless, the growth rate of this species showed no statistically significant differences through the years and no correlation with variation in sunlight. Alow density annual band, wider than high density band in D. labyrinthiformis and narrower in M. annularis, seems to form approximately during April and May in both species, which is coincident with the end of dry season (increase of sea surface temperature, decrease of hours of sunlight and high influence of Dique Channel waters over Rosario islands). The annual bands forming on both species at the study site might be highly related with time of reproduction of each species. Further investigation will permit a better understanding of how some local conditions or coral physiology are related with coral growth at Rosario islands.

PRESENCIA DE LOS OCTOCORALES STYLATULA DIADEMA BAYER (PENNATULACEA) Y CARIJOA RIISEI (DUCHASSAING Y MICHELOTTT) (TELESTACEA) EN LA COSTA CARIBE COLOMBIANA.

Through SCUBA and skin diving various shallow water ecosystems (rocky shores, soft bottoms and coral reefs, 0-30 m deep) were surveyed to collect telestaceans and penatulaceans octocorals; the areas considered were Cartagena, the Rosario islands, Tierra Bomba island, Barú island, San Bernardo islands, Bushnell and Salmedina banks, Capurgana and Zapzurro harbours (8°20,-10°45, N; 75°50,-77°251 W), the Santa Marta area (11°14,50" N; 74°15, W) y and the Guajira (11 °56,58" N; 72°16'18" W), Colombian Caribbean. Stylatula diadema Bayer (Virgulariidae: Pennatulacea) is first recorded for the Caribbean sea and has been found inhabiting soft sand bottoms between 25 and 30 m, at the outer end of Cartagena Bay and the Mangles Bank in San Bernardo islands. The geographic distribution of Carijoa riisei (Duchassaing y Michelotti) (Telestidae: Telestacea) was widen from the Caribbean and Colombia, it has been found in a broad bathymetric range (0.5-30 m) in all the habitats surveyed. Few records of telestaceans and pennatulaceans in this region, as in the rest of the Caribbean, suggest that the octocorallian fauna is mostly represented by gorgonians than by other orders, and shows an inverse relationship with the Indopacific fauna, where the alcyonaceans are the dominant order.

REPORTE SOBRE ALGUNAS ESPECIES DE MAJIDAE (Crustacea: Brachyura) PARA LA COSTA ATLANTICA COLOMBIANA

Seven species of Majidae that haven,t been reported before to the Atlantic Colombian Coast, were descripted and ilustrated. These species were collected in the Rosario Islands and the region of Santa Marta, Colombia.

PECES ASOCIADOS A FORMACIONES CORALINAS DE CINCO ÁREAS DEL CARIBE COLOMBIANO: LISTADO DE ESPECIES Y PRIMEROS REGISTROS PARA LAS ÁREAS

Five coral reef areas at the Colombian Caribbean were assessed between 1998 and 2003 through the “National Coral Reef Monitoring System of Colombia” (SIMAC), recording 198 species of fishes. T h e highest species number was observed in Chengue bay (149), including four new records for the Santa Marta area. At San Andrés Island, 138 species were identified, with nine new records for the Archipelago. At the Rosario Island, 128 species were recorded with eight new records, while 114 species and 12 new records were observed at San Bernardo Islands. Of the 119 fish species recorded at the Urabá area, 48 are reported for the first time.

DISTRIBUCIÓN DE PLAYAS DE ANIDACIÓN Y ÁREAS DE ALIMENTACIÓN DE TO RTUGAS MARINAS Y SUS AMENAZAS EN EL CARIBE COLOMBIANO

Between June and October 2002, six field assistants covered the Colombian Caribbean seashore gathering morphological, biotic and socio-cultural information, by direct observations and interviews with the local communities and authorities. From 1,650 km of Caribbean seashore, 181 beaches (730 km), are visited by one or all sea turtle species to nest or feed in surrounding grounds. Species distribution varied along the different regions of the Colombian Caribbean; however, there was a tendency of some species for specific ecosystems. Green turtles (Chelonia mydas) were most often found in the central Guajira, where sea grasses are most abundant, and hawksbills (E retmochelys imbricata) were most abundant on the coral reefs areas around San Bernardo, Rosario, Fuerte and Tortuguilla islands and the San Andrés cays. Though there was no sea turtle marking or individual counting, data was good enough to establish relative abundance categories as rare, common, and abundant. These categories, along with the also categorized identified threats, allowed me to make regional level recommendations for the conservation of sea turtles in the Caribbean coast of Colombia.

CERATIUM SCHRANK (DINOFLAGELLATAE, PERIDINIALES) DE LAS ISLAS DEL ROSARIO, CARIBE COLOMBIANO

The species of Ceratium Schrank (Dinoflagellatae, Peridiniales) of Rosario Islands, Colombian Caribbean Sea, are pointed out in relation to physical parameters of sea ÿwater for three climatic periods. It is found that the species also correspond to three different populations, some of them being common for the three periods.29 species are reported, 12 are for the first time for the Colombian Caribbean Sea: Ceratium praelongum, C. kofoidii, C. incisum, C. longiroztrum, C. contrarium, C. inclinaturn, C. vultur, C. ranipes, C. reflexum, C. gibberum, C. limulus and C. schranki).Species like C. praelongum, C. ranipes, C. tenue, C. inclinatum, C. vultur and probably C. reflexum and C. lunula usually regarded as shade species, captured in surface tows may show a renewed water caused by strong winds or by small upwellings.Finally, the conservation of C. tenue and C. inclinatum as valid species and not as synonyms of C. horridum is proposed.