Abstract：
During the spring and summer of 2019, an unprecedented cyanobacterial harmful algal bloom (cyanoHAB) was responsible for beach advisories on 25 beaches along the Mississippi Sound for over 3 months. Due to the preceding heavy rainfall and flooding within the Mississippi River watershed, for the first time in history, the Bonnet Carré Spillway (BCS) opened twice in one year during 2019. The coastal cyanoHAB coincided with the second BCS opening. The main objectives of this study were: (1) to investigate the potential for using the National Aeronautics and Space Administration (NASA) ocean color standard Cyanobacteria Index (CIcyano) algorithm to characterize the spatial and temporal extent of the 2019 cyanoHAB; (2) to couple the CIcyano data with river discharge, salinity, and modeled-wind data to study the conditions leading to the cyanoHAB and factors aiding the advection and persistence of the bloom within the Mississippi Sound, including a possible relationship to the BCS; (3) to further investigate the relationship with the BCS by repeating the methods using data from 2018, which was a year when the BCS was opened but no evidence of cyanoHABs was reported along the Mississippi coast. Weekly means and monthly frequency CIcyano images, river discharge, salinity, and modeled-wind data from February to September of 2018 and 2019 were analyzed, which coincide with three BCS openings. In March 2018, a cyanobacteria bloom was observed within Lake Pontchartrain coinciding with the BCS opening; however, the month-long bloom was contained to the lake. Two distinct cyanoHABs were observed in 2019 and both blooms were advected into the Mississippi Sound, and likely contributed to the 3-month-long beach water advisories of 2019 along the Mississippi coastline. From March to mid-July 2019, salinity at stations within the Mississippi Sound was consistently near zero indicating high levels of freshwater. During that time, winds were predominantly northwestward, preventing the BCS waters from flushing into the Mississippi Shelf and resulting in BCS waters remaining longer within the estuarine lakes and Mississippi Sound. Although the BCS had an undeniable impact on the presence of the coastal cyanoHAB of 2019, other variables including wind direction, water flow, mixing, and persistence of freshwater within the Sound can determine the intensity and extent of the cyanoHABs. Coupling in situ phytoplankton information from freshwater water bodies to the marine continuum along with water flow, wind data, and satellite imagery could help identify cyanoHABs at early stages and forecast their trajectory and potential impacts on coastal areas.
摘要：
在2019年春季和夏季，一场前所未有的蓝藻有害藻类水华（cyanoHAB）在密西西比河沿岸的25个海滩上进行了3个多月的海滩咨询。由于之前密西西比河流域内的暴雨和洪水，历史上第一次,2019年，BonnetCarré溢洪道（BCS）在一年内两次开放。沿海cyanoHAB与第二次BCS开放相吻合。这项研究的主要目标是：（1）研究使用美国国家航空航天局（NASA）海洋颜色标准蓝藻指数（Cycyano）算法来表征2019年cyanoHAB的时空范围的潜力；（2）将CIcyano数据与河流排放耦合，盐度,和建模风数据，以研究导致cyanoHAB的条件以及有助于在密西西比河声中平流和持续开花的因素，包括与BCS的可能关系;（3）通过使用2018年的数据重复方法来进一步调查与BCS的关系，这是BCS开放的一年，但在密西西比州海岸没有报告cyanoHAB的证据。每周平均和每月频率CI氰基图像，河流排放,盐度,并对2018年和2019年2月至9月的建模风数据进行了分析，与三个BCS开口重合。2018年3月，在庞恰特雷恩湖中观察到蓝藻水华，恰逢BCS开放；但是，长达一个月的花朵被包含在湖中。在2019年观察到两个不同的cyanoHAB，两个花朵都被平流到密西西比河中，并可能为密西西比州海岸线上的2019年为期3个月的海滩水咨询做出了贡献。从2019年3月至7月中旬，密西西比河湾内车站的盐度一直接近零，表明淡水水平很高。在此期间,风主要是西北方向，防止BCS水域冲入密西西比河架，并导致BCS水域在河口湖泊和密西西比河中保留更长的时间。尽管BCS对2019年沿海cyanoHAB的存在产生了不可否认的影响，但包括风向在内的其他变量，水流,混合,Sound中淡水的持久性可以确定cyanoHAB的强度和范围。将来自淡水水体的浮游植物信息与水流一起原位耦合到海洋连续体，风数据,卫星图像可以帮助在早期阶段识别cyanoHAB，并预测其轨迹和对沿海地区的潜在影响。
