|
southwest Iberian Peninsula Associated Investigators: Related Time Series: The Guadiana estuary (GE) is located in southwestern Iberia and is a 22 km2 mesotidal ecosystem (average depth: 6.5 m), ranging from partially stratified to well-mixed. GE is located in a Mediterranean climate area, classified as highly sensitive to climate change, and is currently considered one of the best preserved and most vulnerable estuaries of the Iberian Peninsula. The Guadiana River watershed is the fourth largest river basin in the Iberian Peninsula, and demonstrates a torrential hydrographic regime, with concentrated rainy periods and a prolonged dry season, usually from May to September. Managing water availability under such demanding conditions led to the construction of hundreds of dams, almost 90 of which have a volume capacity over 1 hm3. Recent construction of the large Alqueva dam, built in the upper estuary in 1999 and completed in 2002, further increased freshwater flow regulation up to 81% (see Barbosa et al., 2010, and references therein). Phytoplankton monitoring in GE began in 1996 and was motivated by an anticipated increase in cyanobacterial blooms caused by the construction of the Alqueva dam. Physical-chemical variables (e.g. temperature, salinity, intensity of photosynthetic available radiation, light extinction coefficient, dissolved oxygen, concentration of dissolved inorganic macronutrients, particulate suspended matter) and phytoplankton abundance, composition, and biomass were routinely monitored at different stations in the upper, middle, and lower estuary in the framework of projects funded by the Portuguěse Foundation of Science and Technology (FCT) and the European Union. Abundance of heterotrophic bacterioplankton and phytoplankton and bacterial production were less frequently determined. Water quality and phytoplankton are also regularly monitored by the Portuguěse Water Institute (INAG). Since 2008, water quality and hydrodynamics have been measured by an autonomous instrumented platform positioned at the estuary entrance (Garel et al., 2009). Data displayed in this site are average monthly values (1996-2010) collected at station "Alcoutim" (37A 28'N 7A 28'W) at subsurface levels (ca. 0.5 m). The station is located ca. 38 km from the Guadiana river mouth within the upper Guadiana estuarine region and has a mean depth of 9 m. Details on sampling and analytical methods are given in Barbosa et al. (2010). Samples were usually collected from the Alcoutim pier using a sampling bottle, and sampling frequency was usually monthly during autumn-winter and biweekly during the spring-summer productive period. Physical-chemical variables were analysed using standard methods. Chlorophyll a concentration, used as a proxy for phytoplankton biomass, was analysed using a spectrophotometric method, after GF/F sample filtration and acetone extraction. Abundance of picoplankton (< 2 Aum) and nanophytoplankton (2-20 µm) was estimated using epifluorescence microscopy, after gluteraldehyde preservation and proflavin staining. Abundance of microphytoplankton (>20 µm) was analysed using inverted microscopy, after Lugol preservation (see Barbosa et al., 2010 for details). References: Barbosa, A.B., Domingues, R.B., and Galvao, H.M. 2010. Environmental forcing of phytoplankton in a Mediterranean estuary (Guadiana Estuary,southwestern Iberia): a decadal of anthropogenic and climatic influences. Estuaries and Coasts, 33:324-341. Garel, E. , Nunes, S., Neto, J.M., Fernandes, R., Neves, R., Marques, J.C., and Ferreira, . 2009. The autonomous Simpatico system for real-time continuous water-quality and current velocity monitoring: examples of application in three Portuguese estuaries. Geo-Marine Letters, 29(5):331-341. |