Table_1_Quantifying the linkages between California sea lion (Zalophus californianus) strandings and particulate domoic acid concentrations at piers across Southern California.docx

Domoic acid-producing blooms of the diatom genus Pseudo-nitzschia are pervasive in coastal environments globally. Domoic acid, a neurotoxin, accumulates via trophic transfer into marine food webs and is often associated with mass marine mammal mortality and stranding events. In Southern California, California sea lions (Zalophus californianus) are an indicator species for food web impacts of domoic acid because they are abundant secondary consumers, sensitive to domoic acid intoxication, and are actively monitored by stranding networks. However, domoic acid exposure may occur a distance from where a sea lion ultimately strands. This spatiotemporal variation complicates coupling domoic acid observations in water to strandings. Therefore, we sought to quantify whether monitoring data from four pier sites across the region, covering nearly 700 km of coastline from 2015-2019, could be used to predict adult and subadult sea lion strandings along the 68 km Orange County coastline surveyed by the Pacific Marine Mammal Center. We found that increased sea lion strandings were often observed just prior to an increase in particulate domoic acid at the piers, confirming that clusters of subadult and adult sea lion strandings with clinical signs of domoic acid intoxication serve as indicators of bloom events. In addition, domoic acid concentrations at Stearns Wharf, nearly 200 km from stranding locations, best predicted increased total sea lion strandings, and strandings of sea lions with domoic acid intoxication symptoms. Particulate domoic acid concentrations greater than 0.05 μg/L at Stearns Wharf were linked to stranding probabilities in Orange County ranging from 2.2% to 55% per week, and concentrations of 0.25 μg/L resulted in weekly stranding probabilities ranging from 16% to 81% depending on the stranding scenario modeled.

产软骨藻酸（Domoic acid）的拟菱形藻属（Pseudo-nitzschia）硅藻水华在全球近岸海域中广泛分布。软骨藻酸作为一种神经毒素，可通过营养级传递在海洋食物网中富集，常与海洋哺乳动物大规模死亡及搁浅事件相关联。在南加州海域，加州海狮（Zalophus californianus）是反映软骨藻酸对食物网影响的指示物种：它们作为数量丰富的次级消费者，对软骨藻酸中毒敏感，且搁浅监测网络会对其开展主动监测。但海狮实际发生软骨藻酸暴露的区域，可能与其最终搁浅的地点存在一定距离。这种时空异质性使得将水体软骨藻酸监测数据与海狮搁浅事件进行关联变得复杂。因此，本研究旨在量化：2015至2019年间覆盖近700公里海岸线的该区域4个码头监测点的监测数据，能否用于预测由太平洋海洋哺乳动物中心（Pacific Marine Mammal Center）开展监测的奥兰治县68公里海岸线上的成年及亚成年加州海狮搁浅事件。研究结果显示，海狮搁浅数量上升的现象，通常会先于码头处颗粒态软骨藻酸浓度的升高出现；这证实了出现软骨藻酸中毒临床症状的亚成年与成年海狮搁浅集群事件，可作为水华发生的指示信号。此外，距离搁浅地点近200公里的斯滕斯码头（Stearns Wharf）的软骨藻酸浓度，对海狮总搁浅量上升以及出现中毒症状的海狮搁浅事件的预测效果最佳。当斯滕斯码头的颗粒态软骨藻酸浓度高于0.05 μg/L时，奥兰治县每周的海狮搁浅概率会介于2.2%至55%之间；而当浓度达到0.25 μg/L时，根据不同搁浅情景模型的预测，每周搁浅概率可升至16%至81%。