Simard, Nathalie, Weise, Andrea M., Rochon, André, Briski, Elizabeta , MacIsaac, Hugh J. and McKindsey, Christopher W. (2024) Discharge of ballast residual sediments during de-ballasting procedures: A more realistic estimate of propagule pressure. Marine Pollution Bulletin, 207 . Art.Nr. 116716. DOI 10.1016/j.marpolbul.2024.116716.

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Abstract

Highlights

• Detailed residual sediment accumulation was mapped in ship ballast tanks.
• High residual sediment accumulation (up to 20 cm and 11-year-old) was found.
• Residual sediments and associated fauna (<1 %) are released during de-ballasting operations.
• High quantity of viable dinoflagellate cysts and invertebrate resting stages are released.
• Better propagule pressure estimates are relevant for ship ballast sediment and NIS management.

Ship ballast residual sediments are an important vector of introduction for non-indigenous species. We evaluated the proportion of residual sediments and associated organisms released during de-ballasting operations of a commercial bulk carrier and estimated a total residual sediment accumulation of ∼13 t, with accumulations of up to 20 cm in some tank areas that had accumulated over 11 years. We observed interior hull-fouling (anemones, hydrozoans, and bryozoans) and high abundances of viable invertebrate resting stages and dinoflagellate cysts in sediments. Although we determined that <1 % of residual sediments and associated resting stages were resuspended and released into the environment during individual de-ballasting events, this represents a substantial inoculum of 21 × 107 viable dinoflagellate cysts and 7.5 × 105 invertebrate resting stages with many taxa being nonindigenous, cryptogenic, or toxic/harmful species. The methods used and results will help estimate propagule pressure associated with this pathway and will be relevant for residual sediments and nonindigenous species management.

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