Advanced monitoring of South Portugal water bodies towards WFD

The challenge on implementation of the EU Water Framework Directive (WFD) fosters the development of new monitoring methods and approaches. It is now commonly accepted that the use of classical monitoring campaigns in discrete point is not sufficient to fully assess and describe a water body. Due to this the WFD promote the use of modelling techniques in surface waters to assist all phases of the process, from characterisation and establishment of reference conditions to identification of pressures and assessment of impact. The work presented in this communication is based on these principles. A classical monitoring of the water status of the main transitional water bodies of Algarve (south of Portugal) is combined with advanced in situ water profiling and hydrodynamic, water quality and ecological modelling of the systems to build a complete description of its state. This approach extends spatially and temporally the resolution of the classical point sampling. The methodology was applied during a 12 month program in Ria Formosa coastal lagoon, the Guadiana estuary and the Arade estuary. The synoptic profiling uses an YSI 6600 EDS multi-parameter system attached to a boat and a GPS receiver to produce monthly synoptic maps of the systems. This data extends the discrete point sampling with laboratory analysis performed monthly in several points of each water body. The point sampling is used to calibrate the profiling system and to include variables, such as nutrients, not measured by the sensors. A total of 1427 samplings were performed for physical and chemical parameters, chlorophyll and microbiologic contamination in the water column. This data is used to drive the hydrodynamic, transport and ecological modules of the MOHID water modelling system (www.mohid.com), enabling an integrate description of the water column.

On the solvation in lipid bilayers measured by pyrene fluorescence: thermal and molecular composition influence on equivalent polarity in lipidic mixtures

Phosphatidylcholine (PC), sphingomyelin (SM) and cholesterol (CHOL) are major constituents of mammalian cell membranes. DPPC/CHOL and DPPC/DMPC are well-known binary mixtures. POPC/CHOL, DOPC/CHOL, egg-SM/CHOL, egg-SM/POPC and egg-SM/DOPC are less studied, but also important for the comprehension of the POPC/egg-SM/CHOL mixtures. These provide complex media for which polarity is hard to access. It is mainly determined by the water penetrating the bilayer (unevenly distributed creating a polarity gradient), though the influence of the dipoles from phospholipids (e.g. –PO, –CO, –OH) and the double bond in the steroid ring of CHOL cannot be neglected. CHOL derivatives are an interesting tool to verify the influence of the double bonds in the polarization of its surroundings. Pyrene fluorescence was used to access an equivalent polarity (associated to the dielectric constant) near the lipid/water interface of lipid bilayers. POPC/CHOL and DOPC/CHOL have similar thermal behavior and variation with CHOL content, though for lower CHOL content the equivalent polarity is higher for the DOPC/CHOL mixtures. The studies with DPPC and DMPC showed that pyrene does not seem to have a marked preference for either ordered or disordered phases. For DPPC/CHOL and egg-SM/CHOL the highlight goes to the behavior of the mixtures at higher CHOL amounts, where there is a substantial change in the thermal behavior and polarity values especially for the egg-SM/CHOL mixture. Egg-SM/POPC and egg-SM/DOPC show different behavior depending on which phospholipid has a higher molar proportion. The ternary mixtures analyzed do not exhibit significant differences, though there is the indication of the existence of a more ordered environment at lower temperatures and a less ordered environment for higher temperatures. The presence of 7DHC or DCHOL in egg-SM bilayers showed a tendency for the same behavior detected upon mixing higher amounts of CHOL.