Temporal variability of Chlorophyll-a concentration in floodplain lakes in response to seasonality of Amazon River discharge Evlyn Moraes Novo, INPE Claudio Clemente Barbosa, INPE José Luiz Stech, INPE Enner Herenio Alcântara, INPE Conrado Moraes Rudorff, INPE Arcilan T Assireu, INPE

Background Optical remote sensing and over 70 in situ samples acquired at Lago Grande de Curuai, near Santarém (Barbosa, 2005) during rising, high, receding and low Amazon River level indicated chlorophyll concentration higher than that reported by Carvalho et al. (2001) e Melack e Forsberg (2001).

Barbosa et al /02 a 12/02/0403/06 a 19/06/04 25/09 a 07/10/03 22/11 a 02/12/03 max=110 x minmax= 62 x minmax= 109 x min max= 125 x min

There are thousands of lakes in the Amazonas/Solimões floodplain (Melack, 1984) but very few of them has been subjected to sistematic study (Melack e Forsberg, 2001). Aspects such as lake shape, size, depth, batimetry, connectivity to main river, origin and geomophological evolution (Latrubesse et al. 2005; Almeida Filho and Miranda, 2008) are frequently overlooked; Degree of preservation of original vegetation cover is also not informed.

Questions raised How chlorophyll patterns are related to fluctuations in the Amazon River level (sediment + water discharge)? Are those patterns recurrent? What are other factors affecting phytoplankton abundance?

How to answer those questions?

Proposed solution Integration of ground sampling, remote sensing and autonomous moored systems –acquire a minimum set of aquatic and atmospheric variables at high time frequency, –transmit the data to a processing center, – make the information available immediately to the user

Proposed Solution : SIMA downlink BRAZILIAN SATELLITES; NOAA/ARGOS uplink Users INPE

Lago Grande de Curuai Juruti Óbidos Satarem Juruti Óbidos Satarem Curuai 100 km Test site

Where to put the system ? 08/JUL / /JUL / /SEP / /OCT / /DEC / Image time series to define limit of the lake across a maximum water level amplitude Boolean operations over Amazon plume maps derived from Landsat TM time series at key distinct stages of the hydrologic cycle

Meteorological variables: Wind (Direction and velocity), Atmospheric Pressure, Air Temperature, Moisture, Radiation (incident and reflected) Limnological variables: Water temperature at 4 levels pH, Conductivity, Turbidity, Chlorophyll a Dissolved Oxigen What to measure?

How to organize the data?

Data Analyses Missing data “correction” Export data according to previous definition –Data above or bellow a given threshold –Daily average –Montly average and so on.

Data Analyses Correlation analyses –What are the variables explaining changes in chlrophyll concentration

Results Correlation analyses significant at 95%

Feb/04 Jun/04 Oct/03 Dec/03

August, 2003 April, 2003

chlorophyll and water level chlorophyll and turbidity Period=10 days Negative Low Assimetric After 10 days Of rising water Chl concentraion drops Period=1 and 10 days Positive Low Assimetric After 1 day of Increased chl Concentration, Turbidity increases After 10 days of Increase chl, turbidiy Also increases.

Conclusions cross-correlation analysis between daily chlorophyll and water level shows with 95 percent confidence that the highest value (r= - 0,59) corresponded to a negative lag of 10 days. for lags larger and smaller than 50 days the correlation drops and loses statistical significance at this lake region seasonal changes in Amazon river discharge explains only about 38 % of daily average of chlorophyll concentration. Cross-correlation between chlorophyll and turbidity shows with 95 % confidence level that the highest value (r= 0.