PELD - ELPA | Long-term studies to assess natural and anthropogenic impacts on the estuary of the Patos Lagoon and Adjacent Coast.

Method steps

The warm temperate shallow Patos Lagoon is the world largest choked lagoon (10,360 km2; 250 km long) with a 200,000 km2 wide watershed. About 80% of the lagoon area comprises predominantly fresh to oligohaline waters, but in the southern region the water exchanges with the Atlantic Ocean give rise to the microtidal estuary (approx. 1,000 km2). The outflow and inflow of fresh and marine waters occur through a stabilized inlet bounded by 4-km long jetties that were constructed at the beginning of the twentieth century (Seeliger et al. 1997). As typical for choked lagoons, water exchange with the coastal ocean is mainly controlled by winds and freshwater discharge, while tides are of minor importance (Möller et al. 2001). In general, northeast and southwest winds generate a pressure gradient between lagoon and nearby coastal region, forcing water outflow and inflow, respectively. During flood periods, the lagoon remains fresh for months and this condition is only altered by very strong southwest winds that generate a reverse outflow (Möller et al. 2001; Fernandes et al. 2002). Peaks of river discharge are associated with El Niño episodes (negative El Niño Southern Oscillation; ENSO Index), when rainfall significantly increases in the region, as observed during 1994/1995, 1997/1998, 2002/2003 and 2010 (see Annual anomalies). In contrast, a water deficit in summer/autumn facilitates seawater penetration northward into the lagoon. During these events, the central lagoon body becomes oligohaline with salinity gradients exceeding 150 km (Möller et al. 1996; Odebrecht et al. 2005) as observed during La Niña 1999–2000 (see Annual anomalies). The high biological productivity, large fisheries, and the presence of a maritime port and an industrial conglomerate, justify the establishment of the Patos Lagoon Estuary and adjacent coast as a SITE of the Brazilian Long Term Ecological Research (BR_LTER), funded by the Brazilian Ministry of Science and Technology (PELD_CNPQ). The long-term project aims to identify the main natural and anthropic impacts on the Estuary of Patos Lagoon and adjacent coastal area.