Manchar Lake is a shallow, seasonally variable freshwater lake in Sindh, Pakistan, subject to agricultural drainage, saline inflow, and domestic and industrial pressures. This study characterizes seasonal variability and evaluates evidence for a monotonic change in satellite-derived turbidity using the Copernicus Land Monitoring Service Lake Water Quality product from Sentinel-3 OLCI. The supplied time series comprised 305 nominal 10-day composites from 11 May 2016 to 21 October 2024. Trend was evaluated using the Mann-Kendall test and Sen's slope estimator at three temporal resolutions: the raw 10-daily series, monthly observations analyzed with a seasonal Mann-Kendall framework, and annual means for complete years 2017-2023. The analysis found a positive but statistically non-significant tendency in all three formulations. For annual means, the reported Sen's slope was +0.26 NTU per year (Kendall's tau = 0.43, p = 0.23), equivalent to approximately +3.0% of the study-period mean per year. The 2017 and 2023 annual means differed by 18.3%. July-September turbidity averaged 11.12 NTU compared with 7.97 NTU in October-June (39.6% higher; Mann-Whitney U test, p < 0.001). These results support a strong recurring seasonal association, but they do not by themselves establish monsoon causation or a confirmed long-term increase. Independent field validation, explicit quality-control reporting, and a longer record are needed to determine whether the indicative upward tendency represents a persistent change in lake turbidity.