Input of Terrestrial Material into Coastal Patagonian Waters and Its Effects on Phytoplankton Communities from the Chubut River Estuary (Argentina)

Abstract

Riverine and eolian-dust inputs to coastal waters are influenced by both rainfall and land-use (i.e., deforestation, agriculture, urbanization). Transport of sediments and nutrients from rivers to the oceans are well- documented worldwide, and it is of major management concern because coastal ecosystems provide a great variety of products and services to humankind. Episodic, but extreme rainfall or dust-storm events can generate abrupt pulsed riverine/eolian discharge events, thus increasing nutrients and sediments in surface waters. It is expected that they will be intensified in the upcoming decades by global change, but we scarcely know how they could impact on coastal planktonic communities. In this chapter we address the main terrestrial material transported via rivers and winds in Patagonian coastal waters of the South West Atlantic Ocean (SWAO) and their impact on the structure and functioning of phytoplankton communities. The rivers in Patagonia carry not only sewage from the cities that lie on their margins, but also heavy loads of nutrients, due to agricultural and cattle raising activities upstream from their mouths; extreme rainfall events increase these inputs manyfold. Eolic inputs are also important over Patagonia because this area has a strong prevalence of winds from the west, carrying a wide variety of particles that are blown far into the ocean, especially after volcanic eruptions. We used the Chubut river estuary (Patagonia) as a reference coastal ecosystem in the SWAO to assess how riverine and eolic inputs impact on phytoplankton which are the base of one of the most productive fisheries areas of the SWAO. Overall, nutrient inputs of terrestrial origin, improved phytoplankton growth, photosynthesis performance and changed the community structure towards a dominance of mostly nanoplanktonic diatom species . These responses, however, might vary due to the interaction of terrestrial material inputs with other global change drivers such as warming, acidification, vertical mixing or solar ultraviolet radiation.