Figure 1.
MODIS satellite imagery of the Tonle Sap ecosystem during the dry (top panel) and wet (bottom panel) seasons in 2008.
Lake area estimates corresponding to the satellite image date were derived from the hydrology model presented in Kummu et al. [49]. Lake level data are in m a.s.l. relative to the Ha Tien datum. The lake bottom is approximately 0.5–0.7 m a.s.l. (right) Map of sampling sites in the Tonle Sap lake and floodplain.
Table 1.
Location and sample collection information.
Figure 2.
Continuous records of daily average dissolved oxygen concentration in the Tonle Sap lake and floodplain.
The horizontal dashed line at 2 mg L−1 indicates hypoxic conditions at the sampling depth. Also shown are lake level and modeled lake area as described in Figure 1.
Table 2.
Average GPP and ER at four locations within the Tonle Sap ecosystem.
Figure 3.
Ecosystem metabolism estimates for the Chong Khneas site (9/2007 to 4/2009).
Data points are daily estimates from the Bayesian state-space model thinned to only include days where diel changes in oxygen were sufficient to produce reliable values. Each point is the median of the posterior distribution for a given day with error bars indicating the 95% credible interval. The red lines are the monthly mean. Also shown is modeled lake area as described in Figure 1.
Figure 4.
Correlations between Tonle Sap ecosystem metabolic properties and physical drivers.
Data points are monthly averages for each site and year. Dissolved oxygen, water temperature, specific conductance, and turbidity are from concurrent measurement at each site using data sondes. Lines indicate significant Pearson’s correlations following a Student's t-distribution (α = 0.05). The dashed line indicates that only data from the Chong Khneas site were included in the correlation analysis.
Figure 5.
The amount of primary production required to support the Tonle Sap fishery (PPR) over a range of potential fisheries yields (see text for explanation).
Each line is a different scenario of carbon transfer through the food web and is a function of the average trophic level of the catch (TL) and trophic efficiency (Q). The right axis shows PPR as a percent of total aquatic net primary production (aNPP). The dashed line indicates the global weighted average for freshwater and marine fisheries (∼8%) [33].