Bight 2023 Chemistry Bivalves

Urban coastal food webs are commonly impacted by anthropogenic activity. To assess the extent of these impacts, bioaccumulation of chemical contaminants was measured in bivalve tissues along the coast of the Southern California Bight (SCB). Mussels and oysters were collected from 30 sites across three seasons in 2024 (winter, spring, and summer) and analyzed for three inorganic elements (arsenic, mercury, and selenium); legacy organochlorine compounds including chlordanes, DDTs, and PCBs; and perfluoroalkyl substances (PFOS and PFOA). A total of 107 composite samples (74 mussel, 33 oyster) were collected, plus 16 field duplicates, for 123 total composited bivalve samples. No clear spatial patterns were observed for arsenic and selenium, consistent with exposure predominantly from natural sources. Chlordanes, DDTs, PCBs, and to a lesser extent mercury had greater concentrations at locations impacted by past and/or present urbanization and anthropogenic activities, such as harbors, bays, and ports. No clear trends were observed between contaminant concentrations and species, season, or organism size, suggesting many factors influenced measured chemical residues. Concentrations were generally comparable to those observed in bivalves in other urbanized environments worldwide. Current levels of legacy organochlorine compounds were lower than those observed in the 1980s and early 1990s by previous bivalve monitoring efforts in the SCB, including the California and NOAA Mussel Watch Programs. There was limited evidence of continued, gradual decreases since the 1990s for some analytes at scattered locales within the SCB. Only PCBs exceeded the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (OEHHA) Advisory Tissue Levels (ATLs), with 26% of samples above the daily consumption ATL and 15% above the ATL for no more than three weekly servings. Bivalves with PCB concentrations exceeding OEHHA ATLs were generally found in Los Angeles/Long Beach Harbor and San Diego Bay. PFOS was not detected, and PFOA was detected in only one sample at a very low concentration (0.19 ng/g), well below advisory levels from other jurisdictions. Planning Documents: Bight23SedQualityQAPlan (Chapter VI) Bight23FieldManual_v3_Appx_A-L Bight23SedQualityIMPlan Assessment Reports: Contaminants in Coastal Bivalves of the Southern California Bight城市沿岸食物网通常受到人类活动的影响。为评估此类影响的程度，本研究对南加州湾（Southern California Bight, SCB）沿岸双壳类（bivalve）组织内化学污染物的生物富集情况进行了测定。 研究团队于2024年的三个季节（冬季、春季与夏季），从30个采样点采集贻贝与牡蛎样本，并针对三类目标分析物开展检测：三种无机元素（砷、汞、硒）、包括氯丹类、滴滴涕类（DDTs）与多氯联苯（PCBs）在内的持久性有机氯化合物，以及全氟辛烷磺酸（PFOS）、全氟辛酸（PFOA）等全氟烷基物质。 本次共采集107份混合样品（其中贻贝74份、牡蛎33份），外加16份现场平行样，总计123份双壳类混合样品。 砷与硒未呈现明确的空间分布特征，这与其暴露途径主要源自自然来源的结论相符。氯丹类、DDTs、PCBs，以及浓度相对较低的汞，在受过往及/或当前城市化与人类活动影响的区域（如海港、海湾与港口）中浓度显著更高。 污染物浓度与物种、季节或生物体尺寸之间未观察到明确的关联趋势，表明实测化学残留水平受多种因素共同影响。本次测得的污染物浓度总体上与全球其他城市化沿岸环境中双壳类的污染物浓度水平相当。 与南加州湾过往双壳类监测项目（包括加州贻贝监测计划与美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）贻贝监测计划）在1980年代至1990年代初的监测数据相比，本次测得的持久性有机氯化合物当前浓度水平更低。针对南加州湾部分分散采样点的部分检测物，仅有有限证据表明其自1990年代以来呈现持续缓慢下降的趋势。 仅PCBs的浓度超过了加州环境保护局环境健康危害评估办公室（Office of Environmental Health Hazard Assessment, OEHHA）制定的咨询性组织浓度限值（Advisory Tissue Levels, ATLs）：其中26%的样品超过了每日食用的ATL限值，15%的样品超过了每周食用不超过3次的ATL限值。PCB浓度超出OEHHA ATLs的双壳类样本主要分布于洛杉矶/长滩港与圣迭戈湾区域。 PFOS未被检出，仅1份样品中检出极低浓度的PFOA（0.19 ng/g），远低于其他地区制定的咨询性限值。 规划文件：Bight23SedQualityQAPlan（第六章）、Bight23FieldManual_v3_Appx_A-L、Bight23SedQualityIMPlan 评估报告：《南加州湾沿岸双壳类中的污染物》