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首页> 美国卫生研究院文献>Ecology and Evolution >Optimizing methods to estimate zooplankton concentration based on generalized patterns of patchiness inside ballast tanks and ballast water discharges
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Optimizing methods to estimate zooplankton concentration based on generalized patterns of patchiness inside ballast tanks and ballast water discharges

机译：基于压载舱内斑驳和压载水排放的广义模式估算浮游动物浓度的优化方法

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摘要

Zooplankton populations are spatially heterogeneous in nature and inside ship ballast tanks. Sampling methods should take heterogeneity into account, particularly when estimating quantitative variables such as abundance or concentration. It is particularly important to generate unbiased estimates of zooplankton concentration in ballast water when assessing compliance with new international ballast water discharge standards. We measured spatial heterogeneity of zooplankton within ballast water using three sampling methodologies. In‐tank pump samples were collected at fixed depths within the vertical part of the ballast tank (side tank). Vertical net‐haul samples were collected from the upper portion of the tank as a depth‐integrated and historically relevant method. In‐line, time‐integrated samples were collected during ballast discharge by an isokinetic sample probe, likely representing the double bottom part of the ballast tank. The bias and precision associated with each sampling method were evaluated in reference to the estimated average abundance of the entire ballast tank, which was modeled from the data collected by all methods. In‐tank pump samples provided robust evidence for vertical stratification of zooplankton concentration in the side tank. A consistent trend was also observed for in‐line discharge samples, with zooplankton concentration decreasing through time as the ballast tank is being discharged. Sample representativeness, as compared to the tank average, varied depending on the depth or tank volume discharged. In‐line discharge samples provided the least biased and most precise estimate of average tank abundance (having lowest mean squared error) when collected during the time frame of 20%–60% of the tank volume being discharged. Results were consistent across five trips despite differences in ballast water source, season, and age.
机译：浮游动物种群在自然上和在船舶压载舱内在空间上是异质的。采样方法应考虑到异质性，尤其是在估计定量变量（例如丰度或浓度）时。在评估是否符合新的国际压载水排放标准时，产生压载水中浮游动物浓度的无偏估计尤其重要。我们使用三种采样方法测量了压载水中浮游动物的空间异质性。舱内泵样品在压载舱（侧舱）的垂直部分内的固定深度处收集。从储罐上部收集垂直的净土样品，作为深度综合和历史相关的方法。串联，时间积分的样品在压载物排放期间通过等速样品探针收集，可能代表压载舱的底部的两倍。参照整个压载舱的估计平均丰度来评估与每种采样方法相关的偏差和精度，该平均压舱度是根据所有方法收集的数据进行建模的。罐内泵样品为侧池中浮游动物浓度的垂直分层提供了有力的证据。在线排放样品也观察到一致的趋势，随着压载舱的排放，浮游动物的浓度随时间降低。与水箱平均值相比，样品的代表性随深度或水箱容积的变化而变化。当在排放的储罐容积的20％至60％的时间范围内进行收集时，在线排放样品可提供最小的偏差和最精确的平均储罐丰度估计值（均方差最低）。尽管压载水来源，季节和年龄有所不同，但五次旅行的结果是一致的。

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