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).

Dai

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-0.45

-0.15

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Daily mean water level Daily mean variation rate

instabilityJ anuary 22nd

stabilityNovember 14th

September 24th

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Daily mean water level Daily mean variation rate

instabilityJ anuary 22nd

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Barbosa et al. 2008

03/02 a 12/02/04 03/06 a 19/06/0425/09 a 07/10/03

22/11 a 02/12/03

max=110 x min max= 62 x minmax= 109 x minmax= 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

Users

INPE

Lago Grande de Curuai

Juruti

Óbidos

Satarem

Juruti

Óbidos

Satarem

Curuai

100 kmTest site

Where to put the system ?

08/08/JUL/JUL/

20022002

24/24/JUL/JUL/

20022002

23/23/SEP/SEP/20012001

28/28/OCT/OCT/19991999

12/12/DEC/DEC/20012001

1- Image time series to define limit of the lake across a maximum water level amplitude

Boolean operations over Amazon plume maps derived from Landsat TMBoolean operations over Amazon plume maps derived from Landsat TMtime series at key distinct stages of the hydrologic cycletime 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?

Data base

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

Water Level -0,57 Wind -0,26

Air Temp -0,30 Air Moisture 0,26 Water Temp -0,16

Turbidity 0,66

significant at 95%

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Chlorophyll Water Level

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Rising High Receding Low

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Average Chl (mg/l)

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1-jan 1-fev 1-mar 1-abr 1-mai 1-jun 1-jul 1-ago 1-set 1-out 1-nov 1-dez

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Chlorophyll Water level (m)

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Chlorophyll (ug/l) Water Level (m) Turbidez (NTU)

August, 2003April, 2003

chlorophyll and water level

chlorophyll and turbidity

Period=10 daysNegativeLowAssimetricAfter 10 days Of rising waterChl concentraion drops

Period=1 and 10 daysPositiveLowAssimetricAfter 1 day ofIncreased chlConcentration,Turbidity increasesAfter 10 days ofIncrease chl, turbidiyAlso 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.

Data base

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1-jan 1-fev 1-mar 1-abr 1-mai 1-jun 1-jul 1-ago 1-set 1-out 1-nov 1-dez

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Chlorophyll Water level (m)