Seasonal changes in chlorophyll distributions in Amazon floodplain lakes derived from MODIS images

Abstract

of total primary production (summarized in Melack and Forsberg 2001). Isotopic studies (Forsberg et al. 1993), however, have shown that the amount of fish carbon derived from the different plant groups is not proportional to their relative contribution to the floodplain production and that algal productivity can be important.The main challenge to further investigation of algal production at the scale of the Amazon basin is the size and complexity of the system subjected to oscillations of river discharge related to the annual cycle and interannual changes (Richey et al. 1989). Because the surface waters transport dissolved and particulate material that supports the biological system, variations of the river control the exchange of resources between the Amazon River and floodplain lakes (Forsberg et al. 1988;Richey et al. 1997). Moreover, inundation is also influenced by other water sources whose contribution to lakes depends on floodplain geomorphology (Mertes 1997), density of floodplain channels (Mertes et al. 1995), and the ratio of local drainage basin area to lake area (Forsberg et al. 1988;Lesack and Melack 1995).To address the wide range of spatial and temporal variability, we present here results from field and satellite analyses. The synoptic view, medium resolution (250 m × 250 m), and relatively high frequency of cloud-free overpasses provided by Terra Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance images make it possible to identify water color changes related to chlorophyll concentrations (Darecki and Stramski 2004). Recent applications of MODIS data to studies of aquatic systems include measurements of water quality in lakes (Koponen et al. 2004), suspended matter in coastal waters (Miller and McKee 2004), and chlorophyll concentration (Kwiatkowska and Fargion 2003).Most inland waters are classified as Case 2 waters (Morel and Prieur 1977;Kirk 1994), in which phytoplankton concentration is not tightly coupled to the amount of total seston and optical properties are determined by a mixture of components, including phytoplankton, inorganic particles, colloids, and dissolved organic matter (Mobley 1994). Much of the research on Case 2 water has been focused on Abstract To assess seasonal changes in phytoplanktonic chlorophyll distributions in Amazon floodplain lakes, a linear mixing model was applied to Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data acquired at four river stages: rising (April), high (June), decreasing (September), and low (November). The study area is located in a floodplain reach from Parintins (Amazonas) to near Almeirim (Pará). A three-end-member mixing model designed to uncouple three fractions [high suspended inorganic matter (ip), low inorganic suspended matter (w), and high chlorophyll a (Chl)] was tested in Lake Curuaí (1.5°S 55.43°W) based on field sampling done almost concurrently with satellite overpasses. During high water, phytoplankton patches are confined to lakes closer to terra firme under the influence of clear water inflow,...

A new method to generate a high-resolution global distribution map of lake chlorophyll

“…The accuracy of these estimates is due in large part to the many pixels available for lake-wide averaging and the fact that large lakes have more ocean-like open pelagic zones and are therefore less dominated by terrestrial inputs of suspended materials other than phytoplankton that can have significant optical effects (Lesht, Barbiero, and Warren 2012;Matthews 2011). The successful use of empirical ocean colour satellite data to estimate chl in smaller lakes (between 0.5 and 100 km 2 ) is far less documented (but see Koponen et al 2004;De Moraes Novo et al 2006) and until now simulated data have been used more frequently (e.g. Gitelson et al 2009;Simis et al 2007;Kallio et al 2001).…”

Evaluation of Primary Production in the Lower Amazon River Based on a Dissolved Oxygen Stable Isotopic Mass Balance

“…These floodplain lakes have high rates of productivity and there is evidence of their legacy biomass in the Amazon mainstem (de Moraes Novo et al, 2006;Abril et al, 2014). This input of floodplain-derived oxygen is reflected in the ratio of CO 2 to O 2 measured at high and low water (Figure 3).…”

Variation of chlorophyll: a concentration before an algal bloom in Taihu Lake detected by MODIS/Terra imagery

“…Water samples were collected from 09:00 AM to16:00 PM at a depth midway between the surface and Secchi depth because this region contributes up to 90% of the upwelling radiation. Chlorophyll a concentration determined at the depth can be regarded as a proxy of the average chlorophyll a in the euphotic zone in unstratified shallow lakes [7].The water samples were filtered and the filters ware wrapped in aluminum foil and then stored frozen (-20ºC) until the analysis was competed. Chlorophyll a concentration determination was performed according to Yang Dingtian [8].…”