Blooms of floating macroalgae have been reported around the world, among which are recurrent blooms of Ulva prolifera and Sargassum horneri in the Yellow Sea and East China Sea. While satellite remote sensing has often been used to estimate their distributions and abundance as well as to trace their origins, because the algae mats are often much smaller than the size of an image pixel, it is unclear to what extent they can be detected and discriminated from each other in satellite imagery. Using data collected from laboratory experiments and by the Sentinel-3 OLCI (Ocean and Land Colour Instrument) and Sentinel-2 MSI (Multi Spectral Instrument) satellite instruments, we conduct simulated experiments to determine the lower detection limit and discrimination limit for these two macroalgae in different water environments and under different atmospheric conditions. For OLCI, the detection limit for both macroalgae is about 0.5% of a pixel, while the discrimination limit varies between 0.8% for clear water and 2% for turbid water. For MSI, the detection limit is about 2%, while the discrimination limit is about 6% for all water types. Below these two limits, detection and discrimination of macroalgae in these regions using the two sensors are subject to large uncertainties, thus requiring additional caution when interpreting algae areas and tracing algae origins.

全世界已经报道了漂浮的大型藻类的花朵，其中包括Ulva prolifera和Sargassum horneri的周期性花朵。在黄海和东海。尽管经常使用卫星遥感来估计其分布和丰度并追踪其起源，但由于藻垫通常比图像像素的尺寸小得多，因此尚不清楚在何种程度上可以检测和辨别它们在卫星图像中彼此分离。使用从实验室实验以及Sentinel-3 OLCI（海洋和陆地颜色仪器）和Sentinel-2 MSI（多光谱仪器）卫星仪器收集的数据，我们进行了模拟实验，以确定这两种大型藻类的下限和鉴别限在不同的水环境和不同的大气条件下。对于OLCI，两个大型藻类的检测极限约为一个像素的0.5％，而辨别极限在0之间变化。清水为8％，混浊水为2％。对于MSI，所有水类型的检出限约为2％，而鉴别极限约为6％。低于这两个限制，使用两个传感器在这些区域中对大型藻类的检测和判别存在很大的不确定性，因此在解释藻类区域和追踪藻类起源时需要格外小心。