[Show abstract][Hide abstract] ABSTRACT: Environmental response in the Pacific to aseismic Cocos Ridge subduction (Panama and Costa Rica). The evolution of the marine communities along the Pacific coast of Central America, may have changed in response to the formation of the Isthmus of Panama. To evaluate the effect of the Aseismic Cocos Ridge (DAC) subduction on the marine benthic communities, we reconstructed benthic assemblages from Neogene fossiliferous formations in Burica and Nicoya peninsulas of Panama and Costa Rica. Paleoecological and paleoenvironmental conditions were reconstructed by comparing community structure from bulk fossil samples with dredge collections from modern Tropical American seas, using principal component analysis. Our results indicate that during the early Pliocene, before the closing of the Isthmus, some oceanic islands existed with moderate upwelling in the Burica region. After the closure, during the late Pliocene and early Pleistocene the collision of the DAC caused an uplift of the seafloor, where water depth of 2 300m became shallow waters of less than 40m depth. Meanwhile, upwelling intensified in the open ocean the uplift that had formed small islands in coastal areas of Burica, creating protected areas and limiting the upwelling effect that was given in open ocean. The subduction of the DAC continued until the islands were joined to the mainland and gradually disappeared, allowing the return of the upwelling. During the middle Pleistocene a second process of accelerated uplift with speeds of 8m/1 000 years provoked again the elevation of the seafloor and later the elevation of the Talamanca Range. The new range formed a barrier that blocked the passage of the Trade winds, created new ecological con-ditions and optimized and allowed the growth of the best coral reefs in the coasts of the tropical Eastern Pacific (POT) between Panama and Costa Rica.
Full-text · Article · Jun 2012 · Revista de biologia tropical
[Show abstract][Hide abstract] ABSTRACT: Strong wind jets from the Caribbean and the Gulf of Mexico cross Cen- tral America through topographic depressions in the cordillera during the boreal winter, pushing Pacific coastal waters offshore, lowering sea levels at the coast, and causing coastal upwelling. Where high mountains impede the winds, this phenomenon does not occur. The Panamanian Pacific shelf is an excellent example of this variability. The coast is divided into two large areas, the Gulf of Panama and the Gulf of Chiriquí. To investi- gate hydrological conditions between the two gulfs, we sampled the water column during upwelling and non-upwelling seasons in each region. In both gulfs during non-upwelling conditions, surface-level nutrients are poor, and the chlorophyll maximum occurs around 30 m where the thermocline intersects the euphotic zone. Oxygen-poor waters (2 ppm) commonly occurred below the thermocline. During the dry season, wind strength in- creased and strong upwelling was observed in the Gulf of Panama. The thermocline rose and surface waters became nutrient enriched and chlorophyll a levels increased. Well- oxygenated waters were compressed to shallow depths. In the Gulf of Chiriquí, wind strength was weaker, surface waters did not become enriched with nutrients, and surface chlorophyll a remained low. We did observe a shallowing of the thermocline in the Gulf of Chiriquí, but in contrast to the Gulf of Panama, wind mixing was not strong enough to result in sea-surface cooling and nutrient enrichment. We postulate that the conver- gence of a shallow thermocline and internal waves in the Gulf of Chiriquí is the likely mechanism that causes pockets of deep water to occasionally migrate into surface waters, leading to restricted and ephemeral upwelling-like conditions. Although its effects upon shallow-water communities remain to be studied, we propose that the process may be more likely to occur during the boreal winter when the thermocline is shallower.
[Show abstract][Hide abstract] ABSTRACT: Water clarity and productivity are fundamentally important for the dis-tribution of tropical marine organisms. In the Caribbean, changes in nutrient loading that result from rapid development are thought to have caused increased planktonic pro-ductivity, reduced water clarity, and reduced reef and seagrass health. Here we analyze chlorophyll a concentration and water clarity from eight years of environmental moni-toring in Bocas del Toro, Panama. Chlorophyll a concentrations did not vary signifi cantly among the six sampled sites and showed no signifi cant temporal changes, despite the recent rapid development in the region, accompanied by scant wastewater treatment. In contrast, water clarity increased signifi cantly during the study period. Because chloro-phyll a does not vary closely with water clarity, Secchi depths are likely to refl ect changes in suspended particulate matter rather than in phytoplankton biomass. Secchi depths decreased with rainfall and wind speed but increased with solar radiation, supporting the idea that clarity was not tightly linked to phytoplankton biomass. The decrease in annual rainfall, but not wind speed, over the past eight years suggests that the long-term trend in Secchi readings is the result of changes in rainfall patterns.
[Show abstract][Hide abstract] ABSTRACT: A grand geological experiment with a global reach to its biological impact, the formation of the isthmus of Panama between 15 and 3 million years ago split the tropical Interamerican Seaway into two and substantially changed the physical oceanog-raphy of each part. That event subjected the now-divided halves of the neotropical ma-rine biota to new environmental conditions that forced each along a different evolution-ary trajectory. For the past 45 years the Smithsonian Tropical Research Institute (STRI) marine sciences program has taken full advantage of this event by sponsoring research on a great diversity of topics relating to the evolutionary effects of the formation of the isth-mus. That research, which has been supported by multiple laboratories on each coast and a series of research vessels, has produced more than 1,800 publications. Here we provide an overview of the environmental setting for marine research in Panama and an historical perspective to research by STRI's scientifi c staff at the different marine facilities.
[Show abstract][Hide abstract] ABSTRACT: RESUMEN Aunque es bien conocida la variación estacional del patrón termohalino en el Golfo de Panamá, la distribución espacial de éstas características es prácticamente desconocida. En vista de ello, hemos utilizado la Base de Datos Oceanográficos del Océano Mundial (WOD01) para describir la variabilidad de la estructura termohalina en el Golfo de Panamá durante la temporada lluviosa y en la temporada seca cuando ocurre el fenómeno de afloramiento. Se seleccionaron los datos correspondientes a dos cruceros oceanográficos que presentan la mayor densidad en sitios de recolecta de muestras durante noviembre de 1967 (temporada lluviosa) y marzo de 1933 (temporada seca). Se utilizó el paquete de programas Ocean Data View para leer la información en WOD01, formar una colección datos y efectuar el análisis de los perfiles oceanográficos. Los resultados indican que la distribución de la temperatura superficial del mar en el Golfo de Panamá es significativamente diferente entre la temporada lluviosa y la temporada seca (Prueba-z = 24, p < 0.01). Durante la temporada lluviosa, las condiciones superficiales son bastantes homogéneas con temperaturas cálidas (> 27.5° C) y salinidad diluida (< 31 psu), por efecto de las lluvias. Durante la temporada seca el agua superficial es más fría (< 21° C) y más salina (> 34 psu). En la sección transversal promedio del golfo, la termoclina (definida como la isoterma de 20° C), se hunde hacia el lado Oeste y por el contrario, prácticamente rompe en la superficie en el lado Este del golfo, donde el afloramiento es más intenso.
[Show abstract][Hide abstract] ABSTRACT: Side-chain-oxidized C-28-sterol 1 and one new pregnane metabolite 2 were isolated from eastern Pacific Muricea spp. The C-24(28)-epoxide functionality is a key intermediate in the C-24-dealkylation mechanism of the conversion of phytosterol to cholesterol by phytophagous insects. Certain marine invertebrates share this dealkylation pathway; however, such a key epoxide feature has not yet been found in a naturally occurring sterol from marine invertebrates. The unusual oxidation pattern of the side chain of I encourages speculation about its biogenesis and converts this non-zooxanthellate gorgonia into an interesting candidate organism for biosynthetic studies on C-24-dealkylation of phytosterols in octocorals. The (22S)-22-hydroxy group, after 24-dealkylation of 1, may be an advantageous functionalization in the side-chain cleavage to C-21-pregnane steroids in Muricea spp.
Full-text · Article · Feb 2006 · European Journal of Organic Chemistry
[Show abstract][Hide abstract] ABSTRACT: The authors investigated the response to experimentally elevated water temperature in genotypes of Pocillopora damicornis from three coral reefs in the upwelling Gulf of Panama and four coral reefs in the non-upwelling Gulf of Chiriqu, Panamanian Pacific. Sea-surface temperature in the Gulf of Panama declines below 20C during seasonal upwelling, while in the thermally stable Gulf of Chiriqu, the temperature ranges from 27 to 29C. Genotypes of P. damicornis from the seven locations were determined by allozyme electrophoresis. The most abundant genotype at each location was selected for a thermal tolerance experiment where corals were exposed to water temperature of 30C (1C above ambient) for 43days. Four site coral genotypes can be uniquely differentiated by the GPI locus, two by the LGG-2 locus, and two by a combination of the MDH-1, LGG-2, and LTY-3 loci. A visual assessment of the coral condition after exposure to an elevated temperature showed that corals from localities in the non-upwelling environment retained a normal to slightly pale appearance, while corals from the upwelling environment bleached and their polyps were mostly retracted. A two-way ANOVA confirmed that corals were significantly affected by water temperature and locality. The zooxanthellae were also significantly affected by the interaction of elevated temperature and locality of the corals. Mean zooxanthellae density decreased by 25 and 55%, respectively, in experimentally heated corals from the non-upwelling and upwelling environments. Low concentrations of photosynthetic pigments per live area of the corals were the norm in corals under elevated temperature. The mean concentration of chlorophyll a per live area of the corals was reduced by 17 and 49%, respectively, in heated corals from the non-upwelling and upwelling sites. Coral genotypes from the upwelling Gulf of Panama demonstrated higher vulnerability to thermal stress than coral genotypes from the non-upwelling Gulf of Chiriqu. However, the latter showed greater differences in their responses. Thus, even at small geographic scales, corals can display different levels of tolerance to thermal stress. The difference in thermal tolerance between corals from upwelling and non-upwelling environments is concomitant with greater genetic differences in experimental corals from the thermally stable Gulf of Chiriqu compared with corals from the upwelling Gulf of Panama.
[Show abstract][Hide abstract] ABSTRACT: A biogenetically interesting halogen-devoid metabolite chamigrenelactone 1, with a high oxygen-content, has been isolated from Laurencia obtusa from Isla Grande (Caribbean Panama). Its structure and stereochemistry were determined on the basis of spectral studies.
[Show abstract][Hide abstract] ABSTRACT: Two unique chloro-pregnane steroids have been isolated from the eastern Pacific octocoral Carijoa multiflora and their structures and stereochemistries were determined on the basis of spectral studies and molecular mechanics calculations.