Tidal and subtidal waves are analyzed with sea-level data and numerical modeling in a short and micro-tidal embayment, Alfacs Bay (NW Mediterranean Sea). Data analysis exhibits tidal wave amplification and seiching (characteristic period of 3.5h) along the bay. Numerical results show an eight-fold increase in quarter-wave resonant wave amplitudes from the mouth to the head of the bay. This amplification follows the classical description of a standing wave. Moreover, resonant wave velocities measured and computed at the bay mouth (node location) are about one order of magnitude higher than tidal currents. Analysis of astronomic tidal propagation in the bay reveals similar behavior for diurnal and semidiurnal constituents. Tidal waves amplify along the bay by 3% for diurnal and 10% for semidiurnal constituents. Numerical simulations conducted with different domains indicate that geometric effects dominate over frictional influences in causing the wave behavior. This behavior is consistent with the existence of a quasi-steady standing wave within the bay.
Lopez, R.; Quintana, X.; Romani, A.; Baneras, L.; Ruiz, O.; Compte, J.; Green, A.; Egozcue, J. J. Estuarine coastal and shelf science Vol. 136, p. 72-81 DOI: 10.1016/j.ecss.2013.11.015 Data de publicació: 2014-01-01 Article en revista
Mediterranean wetland communities are strongly constrained by hydrological perturbations and the water flow regime. Salinity and nutrient availability have often been considered the most important variables determining changes in the phytoplankton community of coastal wetlands. Ratios between the main environmental variables often have more relevance than the absolute values of each variable; however, in most cases ratios are not suitable for use in multivariate models commonly used by limnologists. The main objective of the present work was to identify the main variables or variable ratios that are the driving forces of the major phytoplankton taxonomic groups in Mediterranean coastal wetlands, using compositional data analysis techniques (CoDa). With this aim, eleven shallow wetlands (6 in Emporda, 5 in Donana, NE and SW of Spain respectively) were sampled in winter and spring 2007. Two approaches were used: the first one using raw data and the second one using CoDa techniques to transform data. Our results show that differences in hydrological patterns led to three main community assemblages, ranging from communities dominated by typical marine taxa (diatoms and dinoflagellates) when the marine influence was high, to communities dominated by cyanobacteria during confinement and when inorganic nitrogen was scarce. In freshwaters with a high turnover rate, the community was dominated by opportunistic chlorophytes and cryptophytes that need inorganic nitrogen availability. When the raw data and CoDa approaches were compared, the CoDa approach permitted a better ecological interpretation of the phytoplankton community and the main ecological processes. Salinity was the main environmental determinant with both approaches, while the second CoDa RDA axis was related with the balance between the peptidase and phosphatase enzyme activities, confirming the relevance of nutrient retrieval processes in determining phytoplankton composition. We recommend the use of CoDa techniques for analyses of planktonic communities, such as the one presented here, in order to improve the interpretation of both existing and future datasets. (C) 2013 Elsevier Ltd. All rights reserved.
Falcó, S.; Niencheski, L.; Rodilla, M.; Romero, I.; González-del Rio, J.; Sierra, J.P.; Mösso, C. Estuarine coastal and shelf science Vol. 87, num. 1, p. 92-102 DOI: 10.1016/j.ecss.2009.12.020 Data de publicació: 2010-03 Article en revista