Marine Biology Research

ISSN: 1745-1000 (Print) 1745-1019 (Online) Journal homepage: https://www.tandfonline.com/loi/smar20

Testing the relative effectiveness of traditional and non-traditional antifouling substrates on and macroalgae settlement

Kristopher M. Brant & Matthew R. Gilg

To cite this article: Kristopher M. Brant & Matthew R. Gilg (2014) Testing the relative effectiveness of traditional and non-traditional antifouling substrates on barnacle and macroalgae settlement, Marine Biology Research, 10:10, 1027-1032, DOI: 10.1080/17451000.2013.872800 To link to this article: https://doi.org/10.1080/17451000.2013.872800

Published online: 27 May 2014.

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SHORT REPORT

Testing the relative effectiveness of traditional and non-traditional antifouling substrates on barnacle and macroalgae settlement

KRISTOPHER M. BRANT & MATTHEW R. GILG*

Department of Biology, University of North Florida, Jacksonville, FL, USA

Abstract Due to economic impacts, there is considerable interest in determining effective methods for limiting the attachment of marine invertebrates to submerged materials. We tested the effectiveness of traditional and non-traditional coatings on materials used for boat construction to limit the settlement of and macroalgae. Substrates included fibreglass, fibreglass coated with wax, aluminium, aluminium coated with antifouling paint, aluminium coated with Vaseline®, and aluminium coated with Vaseline® mixed with cayenne pepper. Tiles of each substrate were attached to frames, placed at two sites in the Intracoastal Waterway near Jacksonville, Florida, and collected after one or two successive months in the field. Barnacles as well as macroalgae showed significantly greater settlement on fibreglass than aluminium. Each type of coating tested reduced settlement relative to controls, with the lowest overall settlement of barnacles being observed on aluminium coated with Vaseline®, both with and without the addition of cayenne pepper.

Key words: Algae, antifouling, barnacles, biofouling, macrofouling

Introduction substances, and greater fuel usage due to increased drag (Bendick et al. 2010; Schultz et al. 2011). Biofouling is the term used for undesired accumu- Because of its economic impacts, there is consider- lation of organisms; diatoms, algae, barnacles, and able interest in determining effective methods of others, accumulating on a particular substrate (Costerton et al. 1995). The initial adhesion layer limiting the attachment of marine invertebrates and comprised of bacteria and diatoms is referred to as other foulants to the hulls of ships. a biofilm and allows for the attachment of macro- The present study concentrated on biofouling by foulants (Finlay et al. 2010). Biofouling has become various of barnacles and macroalgae in the an increasing problem in coastal areas in recent waters of Northeastern Florida. Common barnacles to years due to increased development bringing more this area include the , structures and marinas to the coastline that provide eburneus (Gould, 1841) and the striped barnacle submerged, hard surfaces for the attachment of (Darwin, 1854), while com- biofouling organisms. The accumulation of organ- mon algal species include Hypnea volubilis Searles and isms has widespread effects in hard bottom com- Gloiocladia atlantica (Searles) R.E. Norris (Hay & munities and can have economical consequences, Southerland 1988;Searles1991). Another species of as it may facilitate erosion of docks, reduce fuel barnacle noted was the recently introduced titan acorn efficiency of waterborne vehicles and can negatively barnacle, Megabalanus coccopoma (Darwin, 1854). impact fisheries (Champ 1999; Bendick et al. 2010; There are many hypotheses as to what makes an Schultz et al. 2011). In a study looking at the total effective antifoulant. In order to be effective, attach- cost of fouling on a naval fleet, it was estimated that ment of all types of foulants must be limited or between $180 and $260 million is spent annually prevented all together. There have been many pro- on cleaning hulls, coating ships with antifouling ducts used to prevent biofouling through chemical

*Correspondence: Matthew R. Gilg, Department of Biology, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA. E-mail: [email protected]

Published in collaboration with the Institute of Marine Research, Norway

(Accepted 26 November 2013; Published online 26 May 2014; Printed 2 June 2014) © 2014 Taylor & Francis

Published online 27 May 2014 1028 K. M. Brant and M. R. Gilg means; these are effective to a point, but all wear off applied by hand to one side of the substrate in a thin over time (Swain & Schultz 1996). Waxes and other layer (∼2 mm thick) covering the entire surface. polishes claim to prevent fouling through their hydro- Additional fibreglass treatments could not be used phobicity. These tend to be a rather expensive due to space constraints on the collectors in order to solution, costing around $150 for a 6.5 m vessel. have sufficient replication. They are not, however, particularly effective and must Five replicates of each substrate were attached to be replaced at least twice per year to achieve max- two sheets of plastic mesh (46 cm W × 66 cm H) in a imum effectiveness (Bendick et al. 2010). Antifouling random order. Each sheet was then affixed to paints use chemical means to prevent attachment and opposite sides of a frame made of PVC and the are much more expensive. For proper coverage of a frame attached to one end of a 2.44 m PVC pipe. A similar 6.5 m vessel the cost would be at least $500, settlement collector was then attached via hose and the paint must be cleaned and replaced every two clamps to a channel marker at each of two locations or three years (Bendick et al. 2010). Additionally, it is within the Guana Tolomato Matanzas National known that there are regional differences in the Estuarine Research Reserve (GTMNERR), includ- effectiveness of antifoulants (Swain et al. 2000). ing near Fort Matanzas (FM; 29°41′59.9″N, 81°12′ Foulants in different regions show adaptations to 0″W) and San Sebastian (SS; 29°48′0″N, 81°17′ specific nutrients as well as substrate types in their 59.9″W). These sites are located approximately 15 area, so a chemical or substrate surface that deters km from each other and were chosen because biofilm formation in one region may increase affinity previous studies showed high settlement of both the in another. Therefore, testing alternatives that are introduced barnacle Megabalanus coccopoma (Gilg relatively inexpensive yet highly effective is important et al. 2010) and the introduced mussel Perna viridis to determine the most cost-effective methods of (Linnaeus, 1758) (Matthew Gilg, 2013, unpublished reducing biofouling. data) at these locations. The SS site also corresponds The present study focused on testing the relative to a permanent collection station for water quality effectiveness of various substances in reducing bio- data for the Guana Tolomato Matanzas National fouling by barnacles and macroalgae on fibreglass and Estuarine Reserve, and a second water quality aluminium, two common materials used to build station is within 2 km of the FM site. Both sites ships. Traditional antifouling products such as fibre- show similar patterns of temperature, dissolved glass boat wax and antifouling paint for aluminium oxygen and salinity throughout the year and are were compared to a non-traditional treatment of quite similar in depth and current velocity. Collec- Vaseline®, alone and mixed with cayenne pepper. tors were deployed at depths such that they The use of cayenne pepper mixed in gel coats and remained submerged through all tide cycles. boat paints is fairly popular in the Gulf States, where it Substrates were collected and replaced on a is believed the capsaicin from the pepper will discour- monthly basis at FM, from June 2012 to August age foulants. We tested whether these antifouling 2012. To estimate the effectiveness of the treatments substances significantly reduced biofouling relative to for longer duration, the substrates at SS were left in untreated controls and determined which treatments the field for one month, collected, and then replaced would be most cost-effective. For the present study, with substrates that remained in the field for two the six substrates were tested in the Intracoastal consecutive months over the same time period. After Waterway (ICW) near Jacksonville, FL. The end collecting, the frames and substrates were allowed to goal of this study was to determine which methods dry for approximately two weeks before analysis. tested were the most cost-effective way to prevent After drying, each substrate was observed under a fouling. dissection microscope and barnacles of any species and size were enumerated. A grid forming a total of 25 4 cm2 squares was placed over the tiles to ensure Materials and methods accurate counting of barnacles and to determine the Settlement plates were constructed of 10 cm × 10 percentage of algal coverage. Percentage coverage cm cut pieces of either fibreglass or aluminium. of algae was determined by dividing the number Some of each substrate were left untreated as of squares that contained algal growth by the total controls while others were treated with one of four number of squares. substances. Treated fibreglass tiles were covered After testing for normality of the data, a two-way with Collinite 925 fibreglass wax, while treated ANOVA with main effects of time and substrate were aluminium plates were either painted with Trilux conducted to determine if patterns of fouling differed 33 antifouling paint, covered with a coat of Vasel- among substrates at both sites, among months at FM ine®, or covered with a coat of Vaseline® mixed or with additional time in the environment at SS. with 0.015 g cayenne pepper per ml. Vaseline® was Because all two-way ANOVAs showed a significant Effectiveness of non-traditional antifouling methods 1029 interaction between main effects, each main effect was then tested separately using a one-way ANOVA. Significant results of ANOVA were subsequently analysed using a Tukey’s post-hoc means comparison test. All statistical analyses were performed using SPSS software with an alpha value of 0.05.

Results Mean numbers of barnacles differed significantly among substrates in all months at Fort Matanzas (Figure 1) and in both one- and two-month deploy- ments at San Sebastian (Figure 2; FM: June F = 84.7, July F = 103.9, August F = 156.2, df = 5 and Figure 2. Mean barnacle settlement on each of six substrates P < 0.001 in all cases; SS: 1 month F = 58.5, following a one-month deployment in June 2012, and a two- 2 months F = 147.6, df = 5 and P < 0.001 in all month deployment in July and August 2012 near San Sebastian, cases). In general, greater barnacle settlement was FL. Different numbers above bars denote significant differences observed on fibreglass substrates than on aluminium between treatments; see Figure 1 for abbreviation explanations. substrates and treatment groups reduced settlement relative to controls at both locations, with the excep- F = 522.7, August F = 2432.9, df = 5 and P < 0.001 in tion of aluminium treated with antifouling paint in the all cases; SS: 1 month F = 330.7, 2 months F = two-month test at SS. There was typically no signific- 1738.1, df = 5 and P < 0.001 in all cases). Again, ant difference among any of the antifouling treatments greater fouling was observed on fibreglass substrates on aluminium; however, in August at FM the alumi- than on any of the aluminium substrates. The anti- nium treated with antifouling paint had significantly fouling paint treatment showed significantly greater greater barnacle settlement than aluminium covered fouling by macroalgae than either untreated alumi- with Vaseline® mixed with cayenne pepper. This was nium or aluminium treated with Vaseline® or Vasel- the only time cayenne pepper was shown to signifi- ine® with cayenne pepper in three of the five tests cantly decrease barnacle settlement compared to (three time periods at FM plus two time periods at other treatments. In all other months the non-tradi- SS). On the other hand, Vaseline® treatments only tional treatments on aluminium were just as effective showed a significant reduction in algal coverage against barnacle fouling as the traditional treatment. relative to untreated aluminium in the month of Percentage algal coverage also differed significantly August at FM and after two months in the field at SS. among substrates at both sites and in all time periods Time did not appear to be a significant factor for examined (Figures 3, 4; FM: June F = 167.4, July either barnacle settlement or algal coverage at FM, as there were no significant differences in either among months (barnacles: F = 2.205, df = 2, P = 0.116; algae: F = 2.674, df = 2, P = 0.075). The average number of barnacles per tile increased with additional time in the field at SS (F = 8.315, df = 1, P = 0.006), but there was no significant difference in percentage algal coverage (F = 0.777, df = 1, P = 0.382).

Discussion Non-traditional methods were effective at reducing fouling by both barnacles and macroalgae. At both test sites treated aluminium had significantly less accumulation of barnacles and macroalgae than all Figure 1. Mean barnacle settlement on each of six substrates other materials; however, the Vaseline® treatments following one-month deployments near Fort Matanzas, FL in typically had the least settlement. Vaseline® treat- fi summer 2012. Different numbers above bars denote signi cant ments were as effective as the antifouling paint in differences between treatments; FG, fibreglass; FW, fibreglass with wax; AL, aluminium; AB, aluminium with Trillux 33 reducing barnacle settlement and in August the antifouling paint; AV, aluminium with Vaseline®; AC, aluminium cayenne treatment was actually more effective. Fur- with Vaseline® and cayenne pepper mixture. thermore, the Vaseline® treatments were always 1030 K. M. Brant and M. R. Gilg

of cayenne pepper would bring the cost to $107.10; however, the cayenne addition did not decrease biofouling overall as compared to plain Vaseline®. The Vaseline® coating would be most effective for boaters leaving their vessels docked for months at a time without use as movement may result in loss of the coating, although this remains untested. Results of the present study suggest Vaseline® is an effective deterrent of barnacle and macroaglae fouling for at least two months, but it is unknown how long it would be effective. Antifouling boat paints would likely have longer staying power, but still must be replaced every two or three years to maintain effectiveness (Johnson & Miller 2003). Figure 3. Percentage macroalgae coverage on each of six sub- strates following three one-month deployments near Fort Matan- The fact that Vaseline® was so effective at redu- zas, FL in summer 2012. Different numbers above bars denote cing biofouling raises the question of how it is able to significant differences between treatments; see Figure 1 for deter the settlement and growth of barnacles and abbreviation explanations. algae. Dobretsov & Thomason (2011) found that microfouling is greatly reduced on substrates with more effective than the antifouling paint in reducing low surface energy and hydrophobic qualities. With- algal coverage. Substrates in both Vaseline treat- out an adequate biofilm on the substrata, macro- ments were typically mostly covered with Vaseline fouling can also be significantly reduced, because the when collected after one month, but the amount of biofilm can provide nutrients and in some cases gives off a chemical signal that promotes settlement coverage seemed to decrease with time. Still, even and adhesion to the substrata (Zobell & Allen 1935; after two months in the field most of the substrates reviewed by Qian et al. 2007). would still have significant portions that were cov- At both test sites it was apparent that the hydro- ered with Vaseline® upon collection. phobic materials had less biofoulant build up. Vas- Vaseline® was also the most cost-effective coating, eline®, a known hydrophobe, had consistently less with a total cost of $0.04 per tile. By comparison, the accumulation of barnacles and algae than all other antifouling paint was the most expensive at $0.28 per materials. While we did not measure the size of the tile. A Vaseline® coating would provide an inex- barnacles on the plates, in general those found on pensive alternative to traditional antifouling coat- 2 plates covered with Vaseline® tended to be rather ings. A mid-size boat (6.5 m length, 18.4 m ) can small, suggesting that they had settled recently, likely cost approximately $500 to coat properly with after some of the Vaseline® had washed away. The antifouling paint, but it would cost a mere $71.40 lack of barnacle settlement may simply be the result to coat the same area with Vaseline®. The addition of reducing the biofilm, but there are also reasons to believe that Vaseline® may be having a direct effect on the attachment affinities of the macrofoulants. For example, when barnacles were removed from the untreated fibreglass the first few layers of the substrate were often removed along with the barna- cles. The same affect, however, was not observed on the wax-coated fibreglass, suggesting the cement was able to penetrate the fibreglass but not the wax. Barnacles have been shown to change their basal morphology in accordance to substrate thickness and surface characters (Berglin & Gatenholm 2003). The lack of penetration could be due to a response to the hydrophobic properties of the wax. Still, other studies have found that barnacles actu- ally showed increased attachment to surfaces with low Figure 4. Percentage macroalgae coverage on each of six sub- energy (Petrone et al. 2011) and that barnacle larvae strates following a one-month deployment in June 2012, and a two month deployment in July and August 2012 near San Sebastian, prefer hydrophobic surfaces to hydrophilic ones FL. Different numbers above bars denote significant differences (Bennett et al. 2010; Finlay et al. 2010; Magin et al. between treatments; see Figure 1 for abbreviation explanations. 2011). Furthermore, it is known that some barnacles, Effectiveness of non-traditional antifouling methods 1031 such as Amphibalanus amphitrite, can change their in aminoalkyl/fluorocarbon/hydrocarbon-modified xerogel sur- – adhesion mechanisms in response to the substrate faces in the control of marine biofouling. 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