Bight 23 Bivalve Bioaccumulation Lab

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 (chlordanes, DDTs, PCBs), and perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). No clear spatial patterns were observed for arsenic and selenium, consistent with exposure to bivalves 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 other anthropogenic activities, such as harbors, bays, and ports, which also generally had increased concentrations of these contaminants in surficial sediments. No clear trends were observed between contaminant concentrations and species, season, and organism size, suggesting that many factors influenced measured chemical residues in SCB bivalves. 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 (e.g., 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.城市沿海食物网通常受到人为活动的显著影响。为量化评估此类影响的范围，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水平进行了检测。研究于2024年分冬、春、夏三个季节，在30个采样点采集了贻贝与牡蛎样本，针对三类无机元素（砷、汞、硒）、历史残留有机氯化合物（氯丹类、滴滴涕类、多氯联苯（PCBs））以及全氟辛烷磺酸（PFOS）、全氟辛酸（PFOA）开展了分析。未观察到砷与硒的浓度存在明显空间分布模式，这与双壳类主要暴露于自然来源污染物的情况相符。氯丹类、滴滴涕类、多氯联苯以及浓度相对较低的汞，在受过往及/或当前城市化与其他人为活动（如港口、海湾与码头）影响的区域浓度更高；此类区域的表层沉积物中，此类污染物的浓度通常也有所升高。未观察到污染物浓度与物种、季节及生物体尺寸间存在明确关联趋势，这表明南加州湾双壳类体内测得的化学残留水平受多种因素共同调控。其污染物浓度总体上与全球其他城市化沿海环境中双壳类的检测结果相当。当前历史残留有机氯化合物的浓度水平，低于20世纪80年代及90年代初南加州湾双壳类监测项目（如加州贝类监测计划与美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）贻贝观察计划）的既往检测结果。在南加州湾的部分分散采样点，仅有有限证据表明部分检测物自20世纪90年代以来呈现持续缓慢下降的趋势。仅多氯联苯（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）制定的咨询组织浓度限值（ATLs）：26%的样本超出了每日摄入的ATL限值，15%的样本超出了每周最多三份食用量的ATL限值。多氯联苯浓度超出OEHHA咨询组织浓度限值的双壳类样本，主要分布于洛杉矶/长滩港与圣迭戈湾区域。