Enumerating Sparse Organisms in Ships’ Ballast Water: Why Counting to 10 Is Not So Easy

Abstract

To reduce ballast water-borne aquatic invasions worldwide, the International Maritime Organization and United States Coast Guard have each proposed discharge standards specifying maximum concentrations of living biota that may be released in ships’ ballast water (BW), but these regulations still lack guidance for standardized type approval and compliance testing of treatment systems. Verifying whether BW meets a discharge standard poses significant challenges. Properly treated BW will contain extremely sparse numbers of live organisms, and robust estimates of rare events require extensive sampling efforts. A balance of analytical rigor and practicality is essential to determine the volume of BW that can be reasonably sampled and processed, yet yield accurate live counts. We applied statistical modeling to a range of sample volumes, plankton concentrations, and regulatory scenarios (i.e., levels of type I and type II errors), and calculated the statistical power of each combination to detect noncompliant discharge concentrations. The model expressly addresses the roles of sampling error, BW volume, and burden of proof on the detection of noncompliant discharges in order to establish a rigorous lower limit of sampling volume. The potential effects of recovery errors (i.e., incomplete recovery and detection of live biota) in relation to sample volume are also discussed.

Desarrollo de un protocolo de muestreo y análisis de agua de lastre en Jamaica

“…Each replicate was obtained by filtering a known volume of 15m 3 or 16m 3 of ballast water. Miller et al (2011) supports the statistical accuracy of using several trials of 7m 3 each, when testing the level of compliance of ballast water to IMO viability standards once subjected to ballast water treatment systems. Separate cod-ends and meshes were used to collect the live and to-be-preserved replicates.…”

Evaluation of approaches to quantify total residual oxidants in ballast water management systems employing chlorine for disinfection

“…Trained technicians, engineers, or other qualifies individuals would be required to collect grab samples and perform bench DPD analysis if handheld DPD was used to monitor TRO in BWMS application. Furthermore, because large volumes of water are treated or discharged over several hours, collecting appropriate and representative samples from the entire discharge would be challenging (Miller et al, 2011).…”

Optimizing methods to estimate zooplankton concentration based on generalized patterns of patchiness inside ballast tanks and ballast water discharges

“…There has been extensive research to develop equipment for collection of in‐line samples (e.g., Richard, Grant, & Lemieux, 2008; Wier et al., 2015) and to establish minimum required sample volumes (e.g., Frazier, Miller, Lee, & Reusser, 2013; Hernandez, Johansson, Xiao, Lewis, & MacIsaac, 2017; Miller et al., 2011), as well as multiple studies examining the distribution of zooplankton within sequential samples collected by in‐line sampling (e.g., Carney et al., 2013; First et al., 2013; Gollasch & David, 2013). In general, these studies report that plankton concentration can vary widely depending on the timing (sequence) of sample collection, leading to recommendations for collecting multiple 1‐m 3 volume samples.…”