Temporal patterns of plastic contamination in surface waters at the SS Yongala shipwreck, Great Barrier Reef, Australia

Marine plastic pollution is an identified contaminant of emerging concern, with expected increases in contamination levels if plastic production projections eventuate. Scientists, managers and the public are increasingly interested in understanding the status and temporal trends of plastic contamination in the marine environment and specifically the Great Barrier Reef (GBR). Presented in this study is the first temporal assessment of plastic contamination in the surface waters of the GBR, Australia. This was accomplished by conducting replicate surface seawater samples (n=66) adjacent to the SS Yongala shipwreck (central GBR), in Bindal sea country, between 2016 and 2019 using a neuston net. The processing workflow included a stringent protocol involving density flotation, filtration, visual identification and sizing of putative plastics using stereomicroscopy, and chemical characterisation using Fourier transform infrared spectroscopy (FTIR). Overall, a total of 533 plastic items were identified and confirmed as plastic, with plastics detected in every single replicate tow, bar one. Polyethylene and polypropylene were the most common polymers present, and were comprised of macro-, meso- and microplastic fragments and fibres. Concentrations of plastic fluctuated across the three years, with spikes related to wind-speed and extreme weather events. However, overall plastic trends did not significantly increase or alter throughout the study period. This study reveals the chronic presence of plastic debris in the surface waters of the central GBR and highlights the need for long-term monitoring of the marine environment for plastic contamination.

海洋塑料污染已被认定为一类新兴关注污染物，若当前塑料生产的预测趋势得以实现，污染水平预计将进一步攀升。科学家、环境管理者与社会公众愈发关注海洋环境，尤其是大堡礁（Great Barrier Reef, GBR）的塑料污染现状与时间变化趋势。本研究首次针对澳大利亚大堡礁海域的表层水体塑料污染开展时间序列评估。研究于2016至2019年间，在位于中央大堡礁区域的扬古拉号（SS Yongala）沉船附近的宾达尔部族传统海域，利用浮拖网（neuston net）采集了66份平行表层海水样本。样本处理流程采用了一套严格的实验方案，涵盖密度浮选、过滤、借助体视显微镜对疑似塑料颗粒进行目视识别与粒径分级，以及利用傅里叶变换红外光谱（FTIR）开展化学表征。整体而言，本次研究共识别并确认了533件塑料垃圾，除1份平行拖网样本外，其余所有样本均检出塑料颗粒。检出的聚合物以聚乙烯和聚丙烯为主，样本中的塑料形态涵盖大塑料、中塑料与微塑料的碎片及纤维。三年间塑料污染浓度存在波动，峰值与风速及极端天气事件相关。但在整个研究周期内，塑料污染的整体变化趋势并未出现显著上升或改变。本研究证实了中央大堡礁海域表层水体中长期存在塑料垃圾，并强调了对海洋环境开展塑料污染长期监测的必要性。