Water chemistry and nutrients of the Bahía Blanca Estuary

Abstract

Different characteristics of the estuarine environments (i.e. geo-morphological, hydrographi- cal, climatic or chemical ones) strongly condition the biodiversity within those systems (Harri- son 2004). So, the range of values of the different parameters involved (temperature, salinity, pH, dissolved oxygen, inorganic nutrients, organic matter, etc) as well as their corresponding seasonality or anomalies would directly determine the scenario where the whole biological processes will occur also including populations movement along different spatial gradients due to physiological problems (Laprise and Dodson 1994). In addition, the distribution and availability of non-conservative constituents such as oxygen, nutrients or organic carbon de- termine the potential primary production of the system, and consequently the potential transfer of energy to higher trophic levels (Cantoni et al. 2003, Rydberg et al. 2006). Bah´ıa Blanca estuary has been the object of a large number of environmental studies over the last 30 years. From these studies, a large time-series database on physicochemical parame- ters has been assembled for the inner part of the estuary (Pto.Cuatreros and Pto.Ing.White; Figure 1). This database is a very useful tool to diagnose the environmental condition of the system considering that the inner part of the estuary includes not only the entry points of the main rivers from the region but also the largest human activities such as cities, industries and harbours, with their consequent impacts on the estuary. In addition, information has also been recorded through cruises along the Main Navigation Channel, as well as from many coastal studies on the tidal flats at Villa del Mar, Puerto Galv ´an and Puerto Cuatreros (Fig. 1). The main goal of the present chapter is to summarize the available information on the physico- chemical condition of Bah´ıa Blanca estuary, including the corresponding range of values of the considered parameters (temperature, salinity, turbidity, dissolved oxygen, inorganic nutrients (DIN, Dissolved Inorganic Nitrogen; DIP, Dissolved Inorganic Phosphorous and DSi, Dissolved Silicates), particulate organic matter and photosynthetic pigments (Chl-a and phaeopigments), and to identify seasonal variations, as well as the influence of external sources.