AquaEcology GmbH & Co. KG, Marie-Curie-Str. 1, 26129, Oldenburg, Germany.
Wageningen Environmental Research, Wageningen University & Research, Droevendaalsesteeg 3, 6708PB, Wageningen, the Netherlands.
Environ Pollut. 2019 May;248:555-564. doi: 10.1016/j.envpol.2019.02.030. Epub 2019 Feb 14.
Marine litter pollution is a global environmental problem. Beach litter is a part of this problem, and is widely monitored in Europe. The European Marine Strategy Framework Directive (MSFD) requires a reduction of beach litter. A reduction of 30% has been proposed in the European Plastics Strategy. The aims of this study are to develop (a) a method to calculate sufficiently stable and precise baseline values for beach litter, and (b) to derive a method of power analysis to estimate the number of beach litter surveys, necessary to detect a given reduction, using these baseline values. Beach litter data from the OSPAR (Oslo Paris Convention) region were used, and tailor-made statistical methods were implemented in open source software, litteR. Descriptive statistics and Theil-Sen and Mann-Kendall trend analyses were calculated for the most abundant beach litter types, for 14 survey sites. The length of a baseline period necessary to obtain a specified precision of the mean baseline value, expressed as Coefficient of Variation (CV), was calculated. Power analyses were performed using Monte Carlo simulations combined with Wilcoxon tests to determine significant deviations of the simulated datasets from the baseline mean values. For most survey sites, the mean length of monitoring periods necessary to achieve a CV < 10% amounts to four to five years with four surveys a year. The mean number of surveys necessary to detect a statistically significant reduction of 30% with 80% power ranges from 14 to 20. Power analyses show that a reduction of 10% is difficult to detect, because more than 24 surveys are needed. In contrary, a reduction of 40-50% can be detected easily with a small (<12) number of surveys. The new methods could also be applied to other areas where similar beach litter surveys are performed.
海洋垃圾污染是一个全球性的环境问题。海滩垃圾是这个问题的一部分，在欧洲被广泛监测。欧洲海洋战略框架指令（MSFD）要求减少海滩垃圾。欧洲塑料战略提出减少 30%的目标。本研究的目的是开发（a）一种计算海滩垃圾足够稳定和精确基线值的方法，以及（b）一种使用这些基线值来估计检测给定减少所需的海滩垃圾调查次数的功效分析方法。使用了 OSPAR（奥斯陆-巴黎公约）区域的海滩垃圾数据，并在开源软件 litteR 中实施了定制的统计方法。为 14 个调查点的最丰富的海滩垃圾类型计算了描述性统计数据和 Theil-Sen 和 Mann-Kendall 趋势分析。计算了获得指定的平均值基线值精度（表示为变异系数 (CV)）所需的基线期长度。使用蒙特卡罗模拟和 Wilcoxon 检验进行了功效分析，以确定模拟数据集与基线平均值的显著偏差。对于大多数调查点，每年进行四次调查，监测期的平均长度需要达到四到五年，才能达到 CV < 10%。要以 80%的功效检测到 30%的统计学显著减少，需要进行的平均调查次数从 14 到 20 不等。功效分析表明，减少 10%很难检测到，因为需要进行超过 24 次调查。相反，减少 40-50%可以很容易地通过少量 (<12) 的调查来检测到。新方法也可以应用于其他进行类似海滩垃圾调查的地区。
