An experimental test of stationary lay-up periods and simulated transit on biofouling accumulation and transfer on ships.

Biofouling accumulation on ships' submerged surfaces typically occurs during stationary periods that render surfaces more susceptible to colonization than when underway. As a result, stationary periods longer than typical port residence times (hours to days), often referred to as lay-ups, can have deleterious effects on hull maintenance strategies, which aim to minimize biofouling impacts on ship operations and the likelihood of invasive species transfers. This experimental study tested the effects of different lay-up durations on the magnitude of biofouling, before and after exposure to flow, using fouling panels with three coating treatments (antifouling, foul-release, and controls), at two sites, and a portable field flume to simulate voyage sheer forces. Control panels subjected to extended stationary durations (28-, 45- and 60-days) had significantly higher biofouling cover and there was a 13- to 25-fold difference in biofouling accumulation between 10-days and 28-days of static immersion. Prior to flume exposure, the antifouling coating prevented biofouling accumulation almost entirely at one site and kept it below 20% at the other. Foul-release coatings also proved effective, especially after flume exposure, which reduced biofouling at one site from >52% to <6% cover (on average). The experimental approach was beneficial for co-locating panel deployments and flume processing using a consistent (standardized) flow regime on large panels across sites of differing conditions and biofouling assemblages. While lay-ups of commercial vessels are relatively common, inevitable, and unavoidable, it is important to develop a better understanding of the magnitude of their effects on biofouling of ships' submerged surfaces and to develop workable post-lay-up approaches to manage and respond to elevated biofouling accumulation that may result.

Mini-review: Assessing the drivers of ship biofouling management--aligning industry and biosecurity goals.

Biofouling exerts a frictional and cost penalty on ships and is a direct cause of invasion by marine species. These negative consequences provide a unifying purpose for the maritime industry and biosecurity managers to prevent biofouling accumulation and transfer, but important gaps exist between these sectors. This mini-review examines the approach to assessments of ship biofouling among sectors (industry, biosecurity and marine science) and the implications for existing and emerging management of biofouling. The primary distinctions between industry and biosecurity in assessment of vessels biofouling revolve around the resolution of biological information collected and the specific wetted surface areas of primary concern to each sector. The morphological characteristics of biofouling and their effects on propulsion dynamics are of primary concern to industry, with an almost exclusive focus on the vertical sides and flat bottom of hulls and an emphasis on antifouling and operational performance. In contrast, the identity, biogeography, and ecology of translocated organisms is of highest concern to invasion researchers and biosecurity managers and policymakers, especially as it relates to species with known histories of invasion elsewhere. Current management practices often provide adequate, although not complete, provision for hull surfaces, but niche areas are well known to enhance biosecurity risk. As regulations to prevent invasions emerge in this arena, there is a growing opportunity for industry, biosecurity and academic stakeholders to collaborate and harmonize efforts to assess and manage biofouling of ships that should lead to more comprehensive biofouling solutions that promote industry goals while reducing biosecurity risk and greenhouse gas emissions.