利用卫星遥感技术在多个空间尺度上评估美国各地蓝藻水华的发生频率。
Satellite remote sensing to assess cyanobacterial bloom frequency across the United States at multiple spatial scales.
作者信息
Coffer Megan M, Schaeffer Blake A, Salls Wilson B, Urquhart Erin, Loftin Keith A, Stumpf Richard P, Werdell P Jeremy, Darling John A
机构信息
ORISE Fellow, U.S. EPA, Office of Research and Development, Durham, NC, USA.
Center for Geospatial Analytics, North Carolina State University, Raleigh, NC, USA.
出版信息
Ecol Indic. 2021 Sep 1;128:1-107822. doi: 10.1016/j.ecolind.2021.107822.
Cyanobacterial blooms can have negative effects on human health and local ecosystems. Field monitoring of cyanobacterial blooms can be costly, but satellite remote sensing has shown utility for more efficient spatial and temporal monitoring across the United States. Here, satellite imagery was used to assess the annual frequency of surface cyanobacterial blooms, defined for each satellite pixel as the percentage of images for that pixel throughout the year exhibiting detectable cyanobacteria. Cyanobacterial frequency was assessed across 2,196 large lakes in 46 states across the continental United States (CONUS) using imagery from the European Space Agency's Ocean and Land Colour Instrument for the years 2017 through 2019. In 2019, across all satellite pixels considered, annual bloom frequency had a median value of 4% and a maximum value of 100%, the latter indicating that for those satellite pixels, a cyanobacterial bloom was detected by the satellite sensor for every satellite image considered. In addition to annual pixel-scale cyanobacterial frequency, results were summarized at the lake- and state-scales by averaging annual pixel-scale results across each lake and state. For 2019, average annual lake-scale frequencies also had a maximum value of 100%, and Oregon and Ohio had the highest average annual state-scale frequencies at 65% and 52%. Pixel-scale frequency results can assist in identifying portions of a lake that are more prone to cyanobacterial blooms, while lake- and state-scale frequency results can assist in the prioritization of sampling resources and mitigation efforts. Satellite imagery is limited by the presence of snow and ice, as imagery collected in these conditions are quality flagged and discarded. Thus, annual bloom frequencies within nine climate regions were investigated to determine whether missing data biased results in climate regions more prone to snow and ice, given that their annual summaries would be weighted toward the summer months when cyanobacterial blooms tend to occur. Results were unbiased by the time period selected in most climate regions, but a large bias was observed for the Northwest Rockies and Plains climate region. Moderate biases were observed for the Ohio Valley and the Southeast climate regions. Finally, a clustering analysis was used to identify areas of high and low cyanobacterial frequency across CONUS based on average annual lake-scale cyanobacterial frequencies for 2019. Several clusters were identified that transcended state, watershed, and eco-regional boundaries. Combined with additional data, results from the clustering analysis may offer insight regarding large-scale drivers of cyanobacterial blooms.
蓝藻水华会对人类健康和当地生态系统产生负面影响。对蓝藻水华进行实地监测成本高昂,但卫星遥感已显示出在美国进行更高效的时空监测的效用。在此,利用卫星图像评估地表蓝藻水华的年发生频率,对于每个卫星像素,将其定义为该像素全年显示可检测到蓝藻的图像所占百分比。利用欧洲航天局海洋和陆地彩色仪器在2017年至2019年期间获取的图像,对美国大陆46个州的2196个大湖进行了蓝藻发生频率评估。2019年,在所有考虑的卫星像素中,年水华频率的中位数为4%,最大值为100%,后者表明对于那些卫星像素,在考虑的每一幅卫星图像中卫星传感器都检测到了蓝藻水华。除了年像素尺度的蓝藻发生频率外,还通过对每个湖泊和州的年像素尺度结果进行平均,在湖泊和州尺度上汇总了结果。2019年,年湖泊尺度平均频率的最大值也为100%,俄勒冈州和俄亥俄州的年州尺度平均频率最高,分别为65%和52%。像素尺度的频率结果有助于识别湖泊中更容易发生蓝藻水华的区域,而湖泊和州尺度的频率结果有助于确定采样资源的优先级和缓解措施。卫星图像受冰雪存在的限制,因为在这些条件下收集的图像会被标记质量并丢弃。因此,对九个气候区域内的年水华频率进行了调查,以确定缺失数据是否会使更易出现冰雪的气候区域的结果产生偏差,因为这些区域的年度总结将倾向于蓝藻水华往往发生的夏季月份。在大多数气候区域,结果不受所选时间段的影响,但在落基山脉西北部和平原气候区域观察到了较大偏差。在俄亥俄河谷和东南部气候区域观察到了中等偏差。最后,基于2019年年湖泊尺度蓝藻发生频率,利用聚类分析确定了美国大陆蓝藻发生频率高和低的区域。识别出了几个跨越州、流域和生态区域边界的聚类。结合其他数据,聚类分析的结果可能会提供有关蓝藻水华大规模驱动因素的见解。