Costa, A.K.R., Pereira, L.C.C., Costa, R.M., Monteiro, M.C. and Flores-Montes, M., 2013. Oceanographic processes in an Amazon estuary during an atypical rainy season. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.)

This study examined short-term and spatial fluctuations in hydrodynamic and hydrological variables in an Amazon estuary (Taperaçu). The campaign was conducted during the neap tide of an atypical rainy season (April, 2012). Three stations were established in the upper, middle and lower sectors of the estuary to obtain surface and bottom data during flood and ebb tides. Water samples were collected simultaneously in Niskin bottles to determine pH and chlorophyll a levels. In the mid-estuary sector, a mooring was mounted to the bottom with a tide data logger, a CTDO and a mini-current meter for 25 hours. Precipitation levels in April, 2012, were 31% lower in comparison with the same month of the previous year, reflecting the effects of an El Niño event. The temperature of the water was high and stable, varying from 28.5 to 30°C. Salinity was higher and turbidity was lower when compared to a typical rainy season. The higher levels of dissolved oxygen in the lower sector of the estuary appear to be related to the greater hydrodynamic energy in this sector, where wave forces increase the exchange of oxygen in the water-air interface. The lower turbidity appeared to have promoted an increase in chlorophyll a concentrations due to a higher penetration of sunlight, mainly in the upper sector. Many variables recorded in the present study appear to have deviated from the typical range of values for the time of year due to the below-average precipitation recorded during the first half of 2012 (rainy season) in the study area.