[1] Measurements of velocity profiles and near-bottom temperature and pressure were used to determine turbulence properties at a point-source submarine groundwater discharge (brackish) in a tropical estuary. The turbulence properties estimated were Reynolds stress, turbulent kinetic energy production, and vertical eddy viscosity. , respectively) at low tides. Discharge of brackish water increased at low tides, relative to high tides, as indicated by vertical mean velocity and by mean velocity shear. These maxima were caused by decreasing hydrostatic pressure and likely increasing hydraulic head at the site of discharge. Increased turbulence at low tides was one order of magnitude larger than the turbulence caused elsewhere by tidal flows up to~2.5 m s À1 .
La dinámica del océano se caracteriza por procesos que ocurren en una amplia variedad de escalas temporales, entre ellas la inercial o de las oscilaciones libres, que son importantes en algunas regiones de los océanos (e.g., Knauss 2000). Las oscilaciones inerciales pueden jugar un papel crucial en el transporte de contaminantes (
Datos sobre la magnitud y dirección de las corrientes fueron obtenidos en la Bahía de Campeche, al sur del Golfo de México, de marzo a mayo de 1997, para obtener las principales componentes de marea en la región. Las elipses y fases de las diferentes componentes de marea fueron obtenidas mediante un ajuste por mínimos cuadrados acoplado con una modulación nodal a partir de las series horarias de corrientes por marea. Los constituyentes P1 y K2 se infi rieron a partir de los constituyentes K1 y S2, respectivamente. Los resultados muestran la dominancia del armónico K1 en la plataforma continental al sur de la Bahía de Campeche, una región de mareas mixtas con dominancia semidiurna en la zona del umbral de Cayo Arcas y una región de transición entre Cayo Arcas y las estaciones al oeste en la zona de estudio. Las diferencias en las amplitudes de las corrientes de marea en la vertical fueron despreciables, mientras que las diferencias en las fases muestran un retraso significativo entre la superficie y el fondo. El sentido de rotación de las elipses de marea en Cayo Arcas es negativo, mientras que en las otras estaciones fue positivo. Cayo Arcas tiene una fuerte influencia en las corrientes de marea ya que su fase y sentido de rotación varían.
The productivity of mangrove ecosystems is associated with litterfall production, which continuously contributes large quantities of organic matter, in the form of detritus, to the food web via adjacent ecosystems. However, the degree of deterioration of mangrove ecosystems worldwide has been increasing due to anthropogenic activities, leading to the loss of vegetation cover and changes in hydrological patterns, the chemical conditions of interstitial water and soil, and the litterfall degradation rate and, thus, the integration of organic matter into the ecosystem. In this study, we investigate the relationship between leaf degradation and interstitial water chemistry in two mangrove forests located in Oaxaca, Mexico, that are characterized by differences in environmental conditions, species, and anthropogenic activity. Forty-two 10 cm × 20 cm nylon mesh bags were installed in the Rhizophora mangle forest along two flood-associated lines (21 per line), and twenty-one bags were installed centrally in the Avicennia germinans forest because of the flood conditions in this area. Three bags per line were collected each month. This material was then dried and calcined for determination of the decomposition rate (k). The in situ redox potential and interstitial water salinity of mangrove forests were measured using a HACH HQ40d multiparametric probe and A&O refractometer, and the sulfate concentration was determined by ion chromatography. The results show that daily average decomposition rates were higher in the Salina lagoon (k = 0.01 g·day−1) than in the Chacahua lagoon (k = 0.004 g·day−1). The degradation model was Y = 66.054 × 10−0.010t, R2 = 0.89, p ≤ 0.05, for the Salina lagoon and Y = 67.75 × 10−0.004t, R2 = 0.76, p ≤ 0.05, for the Chacahua lagoon. Leaf decomposition rates differed between the Salina and Chacahua lagoons (F1,206 = 4.8, p < 0.03). In the Salina lagoon, dominated by A. germinans, an inverse relationship was established between the percentage of degraded biomass with respect to salinity concentration (R2 = 0.82, p < 0.013) and redox potential (R2 = 0.89, p < 0. 015), and for the Chacahua lagoon, dominated by R. mangle, the percentage of degraded litter biomass was found to be inversely correlated with redox potential (R2 = 0.94, p < 0.005) and sulfate concentration (R2 = 0.88, p < 0.017). Based on the results obtained in this study, we conclude that variations in the chemical conditions of interstitial water and hydrological patterns can affect the process of mangrove leaf degradation based on species and the integration of organic matter in the soil and in adjacent ecosystems. These findings are potentially useful for mangrove management because they advance understanding of the dynamics of organic matter in mangroves and the importance of maintaining the health of these ecosystems, which is necessary for the maintenance of coastal fishing production.
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