In Fall 2017 a large bloom of the toxic dinoflagellate Karenia brevis developed in the Gulf of Mexico. After persisting for months, in Fall 2018 wind and water circulation patterns drove K. brevis towards the east coast of Florida. On September 29, 2018 Palm Beach County, FL beaches were closed due to respiratory and gastrointestinal issues associated with brevotoxins, and effects of brevotoxins were reported from within estuarine segments of the Loxahatchee River Estuary (LRE). This was the first apparent report of a K. brevis bloom impacting inshore portions of the LRE prompting us to question the longevity of K. brevis within a relatively shallow, well-flushed coastal-estuarine system. Within 3 days (October 1, 2018) of the first reported effects of toxins, K. brevis reached over one million cells/L and chlorophyll-a concentrations peaked at 13 µg L⁻¹. Within 11 days (October 9, 2018) both K. brevis and chlorophyll pigment concentrations significantly (p-perm ≤ 0.05) dropped to an average of ≤ 30,000 cells L⁻¹ and < 4 µg L⁻¹ chlorophyll-a, indicating that the bloom had diminished. Using distance-based linear modeling (DistLM) K. brevis abundance alone explained 66% of the variation in a multivariate measure of chlorophylls (driven by carotenoids and chlorophyll-c pigment concentrations), supporting a K. brevis dominated bloom. Following the K. brevis bloom, additional HAB species K. mikimotoi and Pseudo-nitzschia spp singularly explained 6% of the variations in the multivariate measure of chlorophylls. The low explanatory power of individual HAB species, including K. brevis (≤ 0%), signifies the recovery of the phytoplankton population, where non-HAB species likely contributed to the variability in the multivariate measure of chlorophylls and overall chlorophyll-a concentrations (average of 2 µg L⁻¹ during non-bloom conditions). Finally, we evaluated ambient and historical water quality data to assess how these parameters changed before, during, and after the 2018 K. brevis bloom. Temperature, salinity, and nutrients in the LRE were comparable to reports of other K. brevis bloom events along the west coast of Florida. Reduced ammonia-nitrogen (NH₃-N) concentrations and increased tidal amplitude coincided with the end of the bloom in 2018. More work is needed to understand the specific mechanisms constraining K. brevis blooms in tidal estuaries. We suggest that future research focus on water residence times along with nutrient availability in controlling allochthonous HABs in lotic and tidally flushed estuaries. Also, we anticipate this work may stimulate additional efforts to characterize HABs using in situ observations coupled with multivariate measures of chlorophylls, though we recognize much work remains to fully define the value of this approach.

在2017年秋季，墨西哥湾出现了有毒的鞭毛鞭毛小孢粉Karenia brevis。在坚持了几个月之后，2018年秋季，风和水的循环模式驱使brevis K.走向佛罗里达东海岸。由于与短毒素有关的呼吸道和胃肠道问题，佛罗里达州棕榈滩县于2018年9月29日关闭海滩，据报道，洛萨哈奇河河口（LRE）的河口段内有短毒素的影响。这是关于K. brevis的花朵影响LRE近海部分的第一份明显报告，这促使我们质疑K. brevis的寿命在一个相对浅薄，井喷的沿海河口系统中。在首次报告的毒素影响后的三天内（2018年10月1日），短杆菌K.达到了超过一百万个细胞/ L，叶绿素a的浓度达到了13 µg L ^-1的峰值。在短短11天内（2018年10月9日），短光K.和叶绿素色素浓度均显着（p-perm≤0.05）下降至平均≤30,000个细胞L ^-1和<4 µg L ^-1叶绿素-a，表明绽放减少了。使用基于距离的线性建模（DistLM）K. brevis叶绿素（由类胡萝卜素和叶绿素-c色素浓度驱动）的多变量测量值中，仅靠丰度就可以解释66％的变化，从而支持了以短螺旋藻为主的开花。短暂的K. brevis开花后，其他HAB物种K. mikimotoi和Pseudo- Nitzschia spp单独解释了多变量叶绿素测量值的6％。单个HAB物种（包括短小K.（≤0％））的解释力很低，表明浮游植物种群正在恢复，其中非HAB物种可能导致叶绿素和总叶绿素a浓度的多变量测量值的变化（平均2 µg L ^-1在无花的情况下）。最后，我们评估了环境和历史水质数据，以评估这些参数如何在2018年短K.blovis盛开之前，之中和之后发生变化。LRE中的温度，盐度和养分与佛罗里达西海岸其他短K. brevis开花事件的报告相当。降低氨氮（NH ₃ -N）浓度和增加潮汐幅度与2018年盛放期结束同时发生。需要更多的工作来了解限制短毛K.K的具体机制在潮汐河口绽放。我们建议，未来的研究应集中在控制滞留河口和潮汐河口中异源HAB的水停留时间和养分利用率。同样，我们预计这项工作可能会激发更多的努力，以使用原位观察结合叶绿素的多变量测量来表征HAB ，尽管我们认识到仍有很多工作可以完全确定这种方法的价值。