Low salinity shock as a tool to reduce the likelihood of ship-mediated invasions

Abstract

Most common practices to manage ships’ biofouling consist of using Anti-Fouling Systems, which comprises Anti-Fouling Coatings, devices such as Marine Growth Prevention System, and proactive and reactive cleaning. Many of the substances and techniques utilized have the potential to pollute the surrounding environment. The present study tested the use of low salinity water as a simple, low cost and non-polluting biosecurity tool to reduce the likelihood of ship-mediated invasions in Guanabara Bay, Rio de Janeiro, Brazil. Twenty biofouled panels (3.5 months of immersion) were submitted to 4 salinity treatments – 00, 07, 15 and 35 PSU (control) (n = 5 per treatment) for 2-h, and species abundance monitored 1, 7 and 30 days after treatment. One month after treatment, two distinct groups were identified: panels treated with salinities (1) 00 and 07 PSU; and (2) 15 and 35 PSU. Similarity percentage analysis indicated low salinities (00 and 07 PSU) presented more dead organisms, bare spaces, biofilm and recruits when compared to higher salinities (15 and 35 PSU). Biofouling thickness was also significantly lower on the first group. Since treatments with 00 and 07 PSU presented similar and effective results at killing macrofouling and reducing their thickness, we recommend the use of salinities ≤ 7 PSU for controlling vessel and recreational crafts’ biofouling. This treatment proved to be promising as a biosecurity tool and for hull drag management, which can decrease fuel consumption and Greenhouse Gas emissions. Low salinity exposure facilities could enable an environmentally and logistically interesting solution for biofouling management.