Abstract The nesting characteristics (number of nests and eggs, time of year, nesting initiation, and nesting length) of leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata) sea turtles of the southern Caribbean Sea (specifically in the Gulf of Paria in Venezuela), were examined in association with weekly precipitation averages and number of rainy days per week during the period between 2009 and 2018. We hypothesized about the influence of rainfall intensity and patterns as the main abiotic factor for sea turtle nesting. On average, leatherbacks preferred nesting during the drier season of each year (March, April, and May), while hawksbills nested during the rainy season (June to September). For both species, we found few significant correlations between the number of nests or clutch size (number of eggs per nest) and weekly averages of seasonal precipitation rates in the region. Average hawksbill clutch sizes were not correlated with average precipitation rates but were positively correlated with the number of rainy days per week (r=0.66, P≤0.05). Average hawksbill clutch sizes decreased each year on average (-3.3 eggs/year, r=-0.88, P≤0.001), which coincided with a negative long-term trend in the number of rainy days (-0.11 rainy days/week, r=-0.69, P≤0.05). During the study period, nesting activities for both leatherback and hawksbills started progressively later (0.9 and 0.6 weeks/year, respectively p≤0.05) and were shorter (-0.9 and -0.8 weeks /year, P≤0.1 and P≤0.05, respectively).

Resumo A regeneração de carbono na coluna de água da Bacia de Cariaco (Venezuela) foi investigada utilizando um modelo de regressão de alcalinidade total (TA) e a concentração de carbono inorgânico total (TCO2). Produtividade primária (PP) foi determinada a partir da fracção de carbono inorgânico assimilável pelo fitoplâncton e a variação da isotérmica de 22 e 23ºC foi utilizada como um indicador de ressurgência costeira. Os resultados indicam que os níveis de CO2 eram os mais baixos (1962 µmol/kg) na superfície e aumentado para 2451 µmol/kg redox abaixo da interface ico-anóxica. A distribuição vertical de regeneração de carbono foi dominada (82%) por carbono orgânico originário do tecido mole de organismos fotossintéticos, enquanto 18% foram originados da dissolução de calcite biogênica. A regeneração do carbono orgânico foi maior na camada superficial de acordo com os valores de produtividade primária. No entanto, na interface ico-anóxica foi detectado um segundo máximo mais intenso (70-80%), gerado pela respiração quimiotrófica de material orgânico por microrganismos. As percentagens nas camadas anóxicas foram menores porque a decomposição aeróbica ocorre mais rapidamente do que a respiração anaeróbica de matérias orgânicas, pois as fracções mais lábeis de carbono orgânico já foram mineralizadas nas camadas superiores.

Abstract The carbon regeneration in the water column of the Cariaco Basin (Venezuela) was investigated using a regression model of total alkalinity (TA) and the concentration of total inorganic carbon (TCO2). Primary productivity (PP) was determined from the inorganic carbon fraction assimilated by phytoplankton and the variation of the 22 and 23ºC isotherm was used as an indicator of coastal upwelling. The results indicate that CO2 levels were lowest (1962 µmol/kg) at the surface and increased to 2451 µmol/kg below the oxic-anoxic redox interface. The vertical regeneration distribution of carbon was dominated (82%) by organic carbon originating from the soft tissue of photosynthetic organisms, whereas 18% originated from the dissolution of biogenic calcite. The regeneration of organic carbon was highest in the surface layer in agreement with the primary productivity values. However, at the oxic-anoxic interface a second more intense maximum was detected (70-80%), generated by chemotrophic respiration of organic material by microorganisms. The percentages in the anoxic layers were lower than in the oxic zone because aerobic decomposition occurs more rapidly than anaerobic respiration of organic material because more labile fractions of organic carbon have already been mineralized in the upper layers.

For more than ten years, the CARIACO Time-Series Program has studied seasonal patterns and interannual variability at the Cariaco Basin. Monthly core physical and biogeochemical observations have been collected since November 1995 at the CARIACO Time-Series station (10º 30' N, 64º 40' W). A region with suboxic conditions (oxygen and sulfide concentrations <1 µM) is found at intermediate waters at the station. The characteristics of this region show time and space variability, depending on the dynamics of the water. In general, ammonium, nitrate and nitrite disappeared within the suboxic region, although there is a steep ammonium concentration increase with depth after the oxic-anoxic interface suggesting its consumption at this boundary. Our data shows that intrusions are a major factor in affecting the chemical characteristics of the water column.

Por más de diez años, el Programa Serie de Tiempo CARIACO ha estudiado los patrones estacionales y la variabilidad interanual en la Fosa de Cariaco. Observaciones de los principales parámetros físicos y biogeoquímicos se han obtenido mensualmente desde noviembre de 1995 en la estación Serie de Tiempo CARIACO ubicada a 10º 30' N, 64º 40' W. Una región con condiciones subóxicas (concentraciones de oxígeno y sulfuro <1 µM) se encuentran presentes en las aguas intermedias de la fosa. Las características de esta región muestran una variabilidad temporal y espacial que depende de la dinámica de las aguas. En general, los niveles de amonio, nitrito y nitrato son prácticamente indetectables en esta región, aunque se observa un incremento marcado del amonio después de la interfaz lo que sugiere que está siendo consumido en esta zona. Nuestros datos muestran que las intrusiones son un factor importante en alterar las condiciones químicas de la columna de agua.