Mechanical Properties of Protective Coatings against Marine Fouling: A Review

The accumulation of marine organisms on ship hulls, such as microorganisms, barnacles, and seaweeds, represents a global problem for maritime industries, with both economic and environmental costs. The use of biocide-containing paints poses a serious threat to marine ecosystems, affecting both target and non-target organisms driving science and technology towards non-biocidal solutions based on physico-chemical and materials properties of coatings. The review reports recent development of hydrophobic protective coatings in terms of mechanical properties, correlated with the wet ability features. The attention is focused mainly on coatings based on siloxane and epoxy resin due to the wide application fields of such systems in the marine industry. Polyurethane and other systems have been considered as well. These coatings for anti-fouling applications needs to be both long-term mechanically stable, perfectly adherent with the metallic/composite substrate, and capable to detach/destroy the fouling organism. Prospects should focus on developing even “greener” antifouling coatings solutions. These coatings should also be readily addressable to industrial scale-up for large-scale product distribution, possibly at a reasonable cost.

A new biomimetic antifouling method based on water jet for marine structures

Marine biofouling is a serious environmental problem, while traditional chemical antifouling is less environmentally friendly. Biomimetic antifouling is able to overcome this issue by restraining the growth of biofouling at the very beginning, while the current research interest in this field focuses on the dynamic antifouling layers. In order to construct a flowing layer on the surfaces of marine structures such as a ship hull, this study proposes a new biomimetic antifouling method based on the water jet. This new method is inspired by the antifouling mechanism of the kelp and attempts to generate a flowing jet layer on the surface of the marine structure by spraying the water outward. The fouling organism cannot find enough attachment points on the surface of the marine structure because the flow force is greater than adhesion. In order to optimize the design of the water jet, attachment point theory was used to analyze the effect of jet velocity on the flow force, and numerical simulation was conducted to investigate the distribution of the water jet. Based on the theoretical analysis results, experimental tests were carried out to evaluate the performance of the proposed antifouling method. The results demonstrated that the adhesion amount of Phaeodactylum tricornutum can be effectively reduced. The proposed method is able to prevent the attachment of unicellular fouling organisms, thereby hindering the entire fouling process.

Composition and Density of Fouling Organism on the Wood Harbour at Karang-Karangan, Bua District, Luwu Regency

The Research on Composition and Abundance of Biofouling Biota at Woodenpier at Karang-Karangan Beach Bua Sub-district of Luwu Regency was conducted from December 2016-June 2017. The purpose of this research is to know the types of macrobiofouling, and the abundance of macrobiofouling on the wooden pier on the Beach Coral-Karangan, Bua Sub-district, Luwu Regency. Sampling method using a quadrant plot and performed two data retrieves on the poles of wooden pier which were either exposed or unexpressed by water with 12 point stations. The results showed there were 8 species of 6 families: Saccostrea sp (ostreidae), Saccostrea cucullata (Ostreidae), Littoraria scabra (Littorinidae), Thais rufotincta (Muricidae), Septifer sp (Mytilidea), Cladophora glomerata (Cladophoraceae), Balanus sp (Balanidae), and Haemocinus sp (Planopilumnidae). Saccostrea sp has the highest average abundance ofmacrobiofouling on exposed wooden pier (223 ind/m 2). The lowest abundance of Thais rufotincta and Haemocinus sp (1 ind/m2), respectively.

Industrial Seawater Cooling Systems under Threat from the Invasive Green Mussel Perna viridis

The green mussel Perna viridis, native to the Asia-Pacific region, has been introduced to other regions such as the Caribbean, Japan and North and South America. It is a large, commercially important species, widely cultivated and harvested in Southeast Asia, but is also considered an invasive species elsewhere, capable of replacing native species. As a fouling organism in intake systems of coastal power plants, it causes flow blockage and loss of cooling efficiency. Mussel colonization during peak settlement season can exceed 35,000 individuals/m2 and biomass can exceed 100 kg/m2. They can withstand wide fluctuations in temperature and salinity. Previous work has shown that a conventional biofouling control measure such as chlorination is not very effective against these bivalves, unless applied continuously for extended periods of time. We require more efficient, environmentally compatible methods of biofouling control. The paper discusses these issues in the context of the perceived invasion potential of P. viridis.

Biofouling Community Structure in a Tropical Estuary of Goa on the West Coast of India

Biofouling community structure was studied in a tropical monsoon-influenced Mandovi estuary in Goa, west coast of India. Monthly, seasonal and yearly observations on biofouling on polyvinyl chloride (PVC) panels immersed at subsurface water level were recorded and photographed from May 2012 to September 2013. The barnacle Balanus amphitrite was the dominant fouling organism followed by calcareous polychaetes. The settlement and recruitment of barnacles took place year-round, with the exception of July 2012 and June 2013 (monsoon months). However, their peak abundance was observed during the later months of monsoon (August and September). Polychaetes were dominant during late post-monsoon and pre-monsoon months (December 2012 to April 2013). Silt and slime were observed throughout the observation period. Comparing the fouling pressure of barnacles in the two monsoon seasons (2012 and 2013), fouling was more intense during the monsoon of 2013, indicating an inter-annual variation in the fouling community.

Low salinity as a biosecurity tool for minimizing biofouling on ship sea chests

Biofouling is a major vector in the transfer of non-native species around the world. Species can be transported on virtually all submerged areas of ships (e.g. hulls, sea chests, propellers) and so antifouling systems are used to reduce fouling. However, with increased regulation of biocides used in antifoulants (e.g. the International Maritime Organization tributyltin ban in 2008), there is a need to find efficient and sustainable alternatives. Here, we tested the hypothesis that short doses of low salinity water could be used to kill fouling species in sea chests. Settlement panels were suspended at 1.5 m depth in a Plymouth marina for 24 months by which time they had developed mature biofouling assemblages. We exposed these panels to three different salinities (7, 20 and 33) for 2 hours using a model sea chest placed in the marina and flushed with freshwater. Fouling organism diversity and abundance were assessed before panels were treated, immediately after treatment, and then 1 week and 1 month later. Some native ascidian Dendrodoa grossularia survived, but all other macrobenthos were killed by the salinity 7 treatment after 1 week. The salinity 20 treatment was not effective at killing the majority of fouling organisms. On the basis of these results, we propose that sea chests be flushed with freshwater for at least 2 hours before ships leave port. This would not cause unnecessary delays or costs and could be a major step forward in improving biosecurity.

Low salinity as a biosecurity tool for minimizing biofouling in ships sea-chests

Biofouling is a major vector in the transfer of non-native species around the world. Species can be transported on virtually all submerged areas on ships (e.g. hulls, sea-chests, propellers) and so antifouling systems are used to reduce fouling. However, with increased regulation of biocides used in antifoulants (e.g. the International Maritime Organization tributyltin ban in 2008), there is a need to find efficient and sustainable alternatives. Here, we tested the hypothesis that short doses of low salinity water could be used to kill fouling species in sea-chests. Settlement panels were suspended at 1.5 m depth in a Plymouth marina for 24 months by which time they had developed mature biofouling assemblages. We exposed these panels to three different salinities (7 psu, 20 psu and 33 psu) for two hours using a model sea chest placed in the marina and flushed with freshwater. Fouling organism diversity and abundance was assessed before panels were treated, immediately after treatment, and then one week and one month later. Some native ascidian Dendrodoa grossularia survived, but all other macrobenthos were killed by the 7 PSU treatment after one week. The 20 PSU treatment was not effective at killing the majority of fouling organisms. On the basis of these results we propose that sea-chests be flushed with freshwater for at least two hours before ships leave port. This would not cause unnecessary delays or costs and could be a major step forwards in improving biosecurity.

Range expansion of a fouling species indirectly impacts local species interactions

We investigated how recent changes in the distribution and abundance of a fouling organism affected the strength of interactions between a commercially important foundation species and a common predator. Increases in the abundance of boring sponges that bioerode the calcified shells of oysters and other shelled organisms have been attributed to increased salinization of estuarine ecosystems. We tested the hypothesis that fouling by boring sponges will change the interaction strength between oysters and a common predator (stone crabs). We generated five oyster density treatments crossed with two sponge treatments (sponge and no sponge). We contrasted the interaction strength between stone crabs and fouled and non-fouled oysters by comparing the parameters of fitted functional response curves based on Rogers random predation model. We found that fouled oysters suffered higher predation from stone crabs, and that the increased predation risk stemmed from a reduction in the handling time needed to consume the fouled oysters. These findings highlight the importance of understanding the effects of abiotic changes on both the composition of ecological communities, and on the strengths of direct and indirect interactions among species. Global climate change is altering local ecosystems in complex ways, and the success of restoration, management, and mitigation strategies for important species requires a better appreciation for how these effects cascade through ecosystems.

Transitioning to nontoxic antifouling paints

Purpose – The purpose of this paper is to reduce the amount of copper in antifouling paints by using eugenol as an additive. Biofouling leads to deterioration of any submerged material. The most widespread method for control is the application of cuprous oxide antifouling paints which are toxic. First of all, the paper describes the effect of eugenol on larvae of Balanus amphitrite (fouling organism) under laboratory conditions and then the preparation, application and performance of different types of antifouling paints in field trials. Design/methodology/approach – Three types of soluble matrix antifouling paints were prepared with different pigments. The first one containing 16 per cent v/v copper, the second with 1.6 per cent copper and the third with 1.6 per cent copper + 2 per cent eugenol. Findings – After 12 months of immersion in Mar del Plata harbour paints containing 1.6 per cent copper + eugenol and 16 per cent copper were the most effective. Although these formulations showed a similar performance, copper + eugenol-based paint contains 90 per cent lesser copper than a traditional copper-based formulation. Originality/value – The use of antifouling paints with copper + eugenol combination as pigment is a promising alternative due to its performance, low cost and reduction in copper leaching to environment.

Bioadhesion in ascidians: a developmental and functional genomics perspective

The development of bioadhesives inspired from marine animals is a promising approach to generate new tissue-compatible medical components. A number of marine species, through their adhesive properties, also represent significant foulers that become increasingly problematic to aquaculture, shipping or local biodiversity. In order to develop more sophisticated man-made glues and/or efficient fouling resistant surfaces, it is important to understand the mechanical, structural and molecular properties of adhesive organs in selected species. Ascidians are marine invertebrates with larvae that opportunistically attach to almost any type of submerged surface to undergo metamorphosis into permanently sessile adults. Not only do they represent a globally important fouling organism, but they are becoming increasingly popular as model organisms for developmental biology. The latter is due to their phylogenetic position as the sister group to the vertebrates and their cellular and molecular accessibility for experimentation. In this paper, we review the mechanisms of larval adhesion in ascidians and draw conclusions from comparative analyses of selected species. We further discuss how knowledge from a developmental and functional genomics point of view can advance our understanding of cellular and molecular signatures and their hierarchical usage in animal adhesive organs.