Bight 13 Debris Harmonized

The Southern California Bight 2013 Regional Monitoring Program (Bight'13) Trash and Marine Debris assessment presents the results of the first regionalized, comprehensive assessment of trash and marine debris across southern California waterways, from wadeable streams to the nearshore marine environment. The study examined three main habitat types: (1) trash in wadeable streams, (2) epibenthic marine macro-debris on the seafloor, and (3) micro-plastic debris embedded in seafloor sediment. A probability-based stratified-random sampling design was employed across more than 795 sites to produce unbiased estimates of extent and magnitude. Trash was surveyed at 273 stream sites across approximately 9,500 km of wadeable streams in southern California coastal watersheds from 2011 to 2013, while 164 trawl samples were collected for epibenthic macro-debris and 358 sites were sampled for benthic micro-debris in the Bight from July to September 2013. Results indicate that trash and marine debris were found in more than three-quarters (78%) of southern California wadeable streams and in approximately one-third of the Bight seafloor. Plastic was the most prevalent material found across all habitats, accounting for more than 60% of stream trash and comprising the most extensive and abundant debris type on the seafloor. High-density polyethylene (HDPE) was the most common plastic polymer type identified in marine habitats. Historical Bight trawl data from 1994 to 2013 reveal that the extent of seafloor macro-debris nearly doubled and plastic increased threefold over this period. Urban land use was strongly associated with greater extent and magnitude of stream trash, and trash abundance was highest near major roadways. Areas with single-use plastic bag bans had significantly lower median plastic bag densities in streams. Multiple lines of evidence suggest that land-based sources from coastal urban watersheds are major contributors to marine debris in the Bight, with marine sediments acting as a long-term sink for plastic accumulation. The study provides recommendations for continued monitoring, improved study design, new management partnerships, and prioritization of micro-plastic research.南加州湾2013年区域监测计划（Bight'13）垃圾与海洋废弃物评估，呈现了首个覆盖南加州全水域（从可涉水溪流至近岸海洋环境）的区域化、综合性垃圾与海洋废弃物评估结果。本研究针对三类主要生境类型展开调查：(1) 可涉水溪流中的垃圾；(2) 海底表栖大型海洋废弃物；(3) 埋藏于海底沉积物中的微塑料碎屑。研究采用基于概率的分层随机抽样设计，覆盖超过795个采样点，以实现对垃圾分布范围与污染程度的无偏估计。2011年至2013年，研究人员在南加州沿海流域约9500公里的可涉水溪流中，于273个溪流采样点开展垃圾调查；2013年7月至9月，在南加州湾区域针对表栖大型海洋废弃物采集了164份拖网样本，针对底栖微塑料碎屑设置了358个采样点。调查结果显示，南加州超四分之三（78%）的可涉水溪流中存在垃圾与海洋废弃物，南加州湾约三分之一的海底区域亦检出此类污染物。塑料是所有生境中最常见的污染物类型：溪流垃圾中塑料占比超60%，同时也是海底分布最广、丰度最高的废弃物类型。高密度聚乙烯（High-Density Polyethylene, HDPE）是海洋生境中检出的最常见塑料聚合物类型。1994年至2013年的南加州湾历史拖网数据显示，该时段内海底大型废弃物的分布范围几乎翻倍，塑料废弃物丰度增长了两倍。城镇土地利用类型与溪流垃圾的分布范围及污染程度呈显著正相关，且垃圾丰度在主干道附近达到峰值。实施一次性塑料袋禁令的区域，溪流中塑料袋的密度中位数显著更低。多维度证据表明，沿海城镇流域的陆源排放是南加州湾海洋废弃物的主要来源，而海洋沉积物则是塑料累积的长期汇。本研究针对持续监测方案优化、研究设计改进、新型管理合作机制构建以及微塑料研究优先级排序提出了相关建议。