interreg 
Baltic Sea Region 
JROPEAN 
EGIOMAL 
EVELOPMENT 
IHD 
- COMPLETE PLUS 
ill. Introduction 
Biofouling describes the accumulation of organisms such as algae, bryozoa, hydrozoa, tunicata, 
crustacea, and many others as well as microorganisms on ship hulls and niches. If the organisms 
survive, non-indigenous species (NIS) can be introduced beyond their natural range, spread and 
cause harm to native species, the environment, economy, human health or social/cultural values 
(Galil et al. 2019, and references therein). In these cases, introduced NIS become invasive aquatic 
species (IAS). Besides ballast water, biofouling is the major pathway for the translocation of marine 
species by ships (Galil et al. 2019). 
The problem of NIS introduced by ship’s biofouling has worsened over the past few decades due 
to the increased volume of trade and traffic. In addition, slow steaming practices and long lay-up 
periods increased the accumulation of biofouling. As this trend is likely to increase even more in 
the future “at an alarming rate” (IMO 2020), the risk of spread of NIS does not seem to be at its 
zenith, going along with harmful effects in many regions of the world (IMO 2020). 
Furthermore, adherent organisms and their associated increase in hull roughness increase the 
flow resistance, which consequently raises the drag. Deterioration of the hull surface can also be 
caused by corrosion or paint roughness with age, resulting in a poorer hydrodynamic performance 
(Anderson 2004) which leads to an increased fuel consumption. It is necessary to either raise 
power to maintain speed or to prolong voyage time when power is kept constant resulting in slower 
speed (Watermann et al. 2021). Since fuel costs are a major financial factor for a ship’s operator, 
IWC is not only ecologically reasonable but also economically. Furthermore, the Energy Efficiency 
Design Index (EEDI) was made mandatory for new ships and the Ship Energy Efficiency 
Management Plan (SEEMP) for all ships at MEPC 62 (July 2011) with the adoption of amendments 
to MARPOL Annex VI (resolution MEPC.203(62)), by Parties to MARPOL Annex VI. 
Organisms can also attack and corrode the coating of the ships, which may lead to water pollution, 
especially if the paints contain harmful substances, pigments and particles/polymers like 
microplastic (Gaylarde et al. 2020). 
In order to prevent or mitigate biofouling, biofouling management is conducted. The International 
Maritime Organization (IMO) Resolution MEPC.207(62), 2011 Guidelines for the Control and 
Management of Ship’s Biofouling to minimize the Transfer of Invasive Aquatic Species, hereinafter 
referred to as “IMO Biofouling Guidelines”, and the IMO Biofouling Guidance for leisure boats 
(Guidance for Minimizing the Transfer of Invasive Aquatic Species as Biofouling (Hull Fouling) for 
Recreational Craft, MEPC.1/Circ.792) have been adopted in 2011 and 2012 respectively, in order 
to minimize the risk of biofouling species introduction by providing information on all aspects and 
measures to minimize biofouling. The IMO Biofouling Guidelines are currently under revision by 
IMO’s Sub-committee on Pollution Prevention and Response (PPR) to increase its applicability 
and provide more details with regard to its Implementation. Efficient biofouling management 
ancompasses a Biofouling Management Plan and Record Book of each ship as well as the ship- 
specific choice and maintenance of an antifouling-system (AFS) and marine growth prevention