OF BAR­NA­CLES AND BOT­TOM PAINT

Passage Maker - - Seamanship - BY CE­CILIA KIELY IL­LUS­TRA­TIONS BY JEAN MACKAY

BAR­NA­CLES

Boat own­ers see bar­na­cles much the same way back­yard bird­ers view squir­rels or the way gar­den­ers feel about any num­ber of small mam­mals that gnaw on fresh veg­gies: They don’t much like them.

And like feed­ing birds or grow­ing veg­eta­bles en­tails bat­tling with these re­spec­tive pests daily and of­ten to no avail, boat own­ers’ ef­forts to mit­i­gate bar­na­cles (and the other flora and fauna col­lec­tively known as “marine foul­ing”) is on­go­ing and of­ten feels fu­tile. Yet while ro­dents and lago­morphs may have a cer­tain charm in a dif­fer­ent con­text (an­i­mated films, Beatrix Pot­ter books, in­ter­net memes, etc.), bar­na­cles are al­most uni­ver­sally un­der­val­ued. (Ap­par­ently “Bar­na­cles!” is used as a stand-in ex­ple­tive on the an­i­mated TV show Sponge­Bob SquarePants.) Even in tide pools and aquar­ium touch tanks, the bar­na­cle can’t com­pete. It lacks the star power of the sea star, and even com­mon her­mit crabs (they steal other an­i­mals’ shells!), the drab green rock­weed (you can pre­tend it’s mer­maid hair!), and timid peri­win­kles (they’re not as bor­ing as bar­na­cles!) have more al­lure.

The largely in­ert bar­na­cle seems to barely qual­ify as an an­i­mal. And it likely doesn’t help that the one “amaz­ing sci­ence fact” about the bar­na­cle—the rel­a­tive size of one of its or­gans—is not well suited for kids’ books, and so the bar­na­cle is largely ig­nored in the “na­ture is cool” lit­er­a­ture that has an out­size im­pact on wildlife pop­u­lar­ity.

This is not to say that no one likes bar­na­cles. Some peo­ple love them. In fact, many of the peo­ple who know the most about bar­na­cles—bi­ol­o­gists—have been ob­sessed with these crea­tures for years. In the mid­dle of pub­lish­ing his best-known re­search on evo­lu­tion, Charles Dar­win es­sen­tially spent eight years nerd­ing out on bar­na­cles, at­tempt­ing to clas­sify these enig­matic or­gan­isms. His deep dive into the species he called Cir­ri­pedia was in­spired by his ob­ser­va­tion of a bar­na­cle on his re­search ves­sel, HMS Bea­gle, years ear­lier, a bur­row­ing bar­na­cle that Dar­win, no joke, had named “Mr. Arthrobal­anus.”

Bi­ol­o­gist Rachel Carson was also fas­ci­nated by bar­na­cles. And both Dar­win and Carson had their bar­na­cle-re­lated work over­shad­owed by the game-chang­ing na­ture of their later works. In The Rocky Coast, one of her pre– Si­lent Spring books, Carson spends much time pon­der­ing the bar­na­cle, in­tro­duc­ing the species with this po­etic de­scrip­tion: “Like drifts of old snow no longer white, bar­na­cles come into view; they blan­ket rocks and old spars wedged into rock crevices, and their sharp cones are sprin­kled over empty mus­sel shells and lob­ster-pot buoys and the hard stipes of deep-wa­ter sea­weeds, all min­gled in the flot­sam of the tide.” And they don’t just pro­vide for scenic shorescapes. Carson char­ac­ter­izes these bar­na­cles as pi­o­neers—hum­ble crea­tures that likely made way for all the other life forms to set­tle on the in­hos­pitable rocky coast­line of north­ern New Eng­land. She writes, “The first per­ma­nent in­hab­i­tants must have been such plank­ton-strain­ers as the bar­na­cles and mus­sels, who re­quire lit­tle but a firm place to which they may at­tach them­selves.”

And most boat own­ers would likely ask these bar­na­cles, of all the firm places in the ocean, why must you at­tach your­self to my hull?

BOT­TOM PAINT

As long as nat­u­ral­ists have been fas­ci­nated by bar­na­cles, boaters have been frus­trated by them. Even Dar­win, af­ter his eight-year ob­ses­sion, ul­ti­mately found him­self ex­as­per­ated by the bar­na­cle and its re­fusal to fit neatly into any tax­o­nomic sys­tem. In a let­ter to a friend in 1854 he wrote, “I hate a Bar­na­cle as no man ever did be­fore, not even a sailor in a slow-sail­ing ship.”

Through­out his­tory, sailors have tried just about ev­ery­thing to dis­cour­age growth on the bot­toms of their ships. Un­for­tu­nately, though per­haps not sur­pris­ingly, the lit­er­a­ture on this his­tory of an­tifoul­ing so­lu­tions is lim­ited. But in the mid-1940s, the U.S. Navy com­mis­sioned a study by the Woods Hole Oceano­graphic In­sti­tute. The re­sult­ing mono­graph pub­lished in 1952, Marine Foul­ing and Its Pre­ven­tion, is a very thor­ough sci­en­tific ex­am­i­na­tion of ev­ery as­pect of the topic that could well be con­sid­ered the Ori­gin of Species/Si­lent Spring of the bio­foul­ing canon. A chap­ter ti­tled “The Foul­ing Com­mu­nity” runs through the more than 2,000 species that might at­tach them­selves to a ship’s bot­tom, and in

“The Prin­ci­pal Foul­ing Or­gan­isms” bar­na­cles get a shout-out as “the most fa­mil­iar of the arthro­pods found on ship bot­toms.”

And in the re­port’s chap­ter called “The His­tory of the Pre­ven­tion of Foul­ing” there’s an­other du­bi­ous shout-out, this time to Dar­win him­self. The pre­vi­ous sci­ence on an­tifoul­ing had been scarce, the au­thors note. Up to that point only one “real” sci­en­tist, Sir Humphry Davy, had done a truly rig­or­ous study of var­i­ous com­pounds’ ef­fec­tive­ness in pre­vent­ing un­wanted marine growth. The au­thors con­tinue: “It is in­ter­est­ing to note in pass­ing that a gen­er­a­tion later an­other great English sci­en­tist, Charles Dar­win, be­came the au­thor­ity on bar­na­cles and thus con­trib­uted valu­able knowl­edge of the sub­ject with­out ap­par­ently be­com­ing con­cerned with its prac­ti­cal as­pects.” (Ap­par­ently his em­pa­thy with the “sailor in the slow-sail­ing ship” did not com­pel him to seek a so­lu­tion.)

But there were many oth­ers more di­rectly affected by these slow-sail­ing ships who were driven to find a bet­ter way to pro­tect boats from bar­na­cles, et al. The Navy’s an­tifoul­ing re­port pro­vides this succinct re­cap of the evo­lu­tion of their so­lu­tions: First, ships use metal sheath­ing to pre­vent growth, and cop­per is fi­nally iden­ti­fied as the most ef­fec­tive an­tifoul­ing agent. But then as iron ships re­place wooden boats, cop­per sheath­ing can no longer be used as it causes elec­trolytic cor­ro­sion of the metal hull. Fi­nally, the in­ven­tion of cop­per­con­tain­ing bot­tom paints al­lows cop­per to be used on top of an an­ti­cor­ro­sive hull coat­ing.

Though this his­tory spans cen­turies, these three dis­tinct eras oc­curred in some­what rapid suc­ces­sion. Var­i­ous me­tals, in­clud­ing lead and cop­per, were likely used on ships as far back as the Greeks and Ro­mans, but the first doc­u­mented use of cop­per sheath­ing on a hull was in the 18th cen­tury. Iron ships be­gan to be built in the 1830s, and the third an­tifoul­ing era, the use of cop­per-based bot­tom paint, was ush­ered in the mid-19th cen­tury. The first fac­tory to pro­duce a cop­per bot­tom paint, the Tarr and Won­son Paint Fac­tory on Rocky Neck in Glouces­ter, Mas­sachusetts, filed their patent for “Im­prove­ments in Paints for Ships’ Bot­toms” in 1863.

But the his­tory of an­tifoul­ing un­for­tu­nately did not end there. Shortly af­ter the re­port’s pub­li­ca­tion in 1952, a new bio­cide, trib­utyltin (TBT), was in­tro­duced and be­gan to be used widely in bot­tom paint in the 1960s. The marine equiv­a­lent of Carson’s main tar­get, the pes­ti­cide DDT, TBT was a harsh poi­son that caused sig­nif­i­cant prob­lems in the marine en­vi­ron­ment, in­clud­ing se­vere de­for­mi­ties in many shell­fish species. Carson passed away in 1964, and it’s hard not to wonder whether the En­vi­ron­men­tal Pro­tec­tion Agency’s 1988 ban would have been has­tened had she been alive. It seems only nat­u­ral that she would have taken up the cause on be­half of her beloved tide-pool dwellers.

With TBT off the ta­ble, most boat own­ers turned back to cop­per-based paints, which re­main com­mon to­day. Now, it can be hard to pin­point the main cul­prit of ris­ing cop­per lev­els in ocean wa­ter (in­dus­trial pol­lu­tion from fac­tory runoff and min­ing op­er­a­tions, for ex­am­ple, is a ma­jor source). But it’s hard to ar­gue that large num­bers of boats coated in paints that work by leach­ing small amounts of a sub­stance is not at least par­tially to blame for the in­crease in con­cen­tra­tion of that sub­stance, es­pe­cially in densely packed mari­nas and crowded har­bors. In 2011, Wash­ing­ton be­came the first state to en­act a ban on cop­per-con­tain­ing bot­tom paints, per­haps not sur­pris­ing given that cop­per tox­i­c­ity is par­tic­u­larly harm­ful to salmon.

BIOMIMICRY

Though the de­bate con­tin­ues about cop­per bot­tom paints, what’s clear is that con­tin­u­ing to rely on bio­cides of any type is not sus­tain­able. For­tu­nately real progress in the search for an en­vi­ron­men­tally friendly an­tifoul­ing agent is be­ing made in the study of biomimicry: look­ing to na­ture for in­spi­ra­tion in solv­ing engineering chal­lenges and en­vi­ron­men­tal prob­lems. For ex­am­ple, the fact that sharks gen­er­ally do not at­tract bar­na­cles or al­gal growth has led sci­en­tists to de­velop shark­skin-in­spired coat­ings that not only have use on ships but have also been stud­ied in med­i­cal set­tings as a way to dis­cour­age mi­cro­bial growth on work­ing sur­faces.

Tak­ing cues from an en­tirely dif­fer­ent ecosys­tem, re­searchers in Aus­tralia have de­vel­oped an­tifoul­ing coat­ings made up of

“nanowrin­kles” (truly mi­cro­scopic struc­tures) that mimic the leaves of the car­niv­o­rous pitcher plant and cre­ate a slip­pery sur­face that bar­na­cles and other mem­bers of the “foul­ing com­mu­nity” can­not at­tach to. The ad­vances in tech­nol­ogy that al­low these re­searchers to mine the nanos­truc­tures of plants and an­i­mals for in­spi­ra­tion are also al­low­ing to­day’s sci­en­tists to un­cover the se­crets of the enig­matic bar­na­cle in a way Dar­win could have only dreamed of.

BAR­NA­CLES (PART II)

Un­der­neath its crusty ex­te­rior, the bar­na­cle is ac­tu­ally a fas­ci­nat­ing crea­ture, and one that pro­duces one of the strong­est bioad­he­sives—a ce­ment that puts your 5200 to shame. (Ac­cord­ing to NOAA, the ten­sile strength of bar­na­cle glue is 5,000 psi. A tube of 3M’s strong­est marine ad­he­sive sealant has a ten­sile strength of only 700psi.)

While sci­en­tists have long known that bar­na­cle ce­ment is a two-part so­lu­tion, they had long as­sumed it worked much like a two-part epoxy: mix first to ac­ti­vate the ad­he­sive. But that didn’t ex­plain how the bar­na­cle was able to use this ad­he­sive so ef­fec­tively un­der­wa­ter. In a 2014 ar­ti­cle in Na­ture Com­mu­ni­ca­tions, a team of re­searchers shared the re­sults of a ground­break­ing study. With im­proved pho­ton tech­nol­ogy, they were able to, for the first time, ob­serve bar­na­cle lar­vae at­tach­ing to a rock in high enough res­o­lu­tion as to see that the two-part ad­he­sive was not mixed but rather used si­mul­ta­ne­ously—a lipid-based sub­stance moves the wa­ter mol­e­cules out of the way while the other, a pho­to­pro­tein, ad­heres to the sur­face.

The ben­e­fits of this re­search are two-fold. As the re­searchers put it, “Knowl­edge of the li­pidic con­tri­bu­tion will hope­fully in­spire de­vel­op­ment of novel syn­thetic bioad­he­sives and en­vi­ron­men­tally be­nign an­tifoul­ing coat­ings.” In other words, not only can the bar­na­cle teach us how to make a bombproof glue, but in learn­ing how bar­na­cles ac­tu­ally at­tach them­selves to sur­faces so stub­bornly, we might also be able to do bet­ter job of pre­vent­ing them from do­ing so—with­out pol­lut­ing our oceans.

BOT­TOM PAINT (PART II)

In a fitting sec­ond life, the pi­o­neer­ing an­tifoul­ing paint pro­duc­ers, the Tarr and Won­son Paint Fac­tory, which closed in 1980, was re­cently ren­o­vated and now serves as the home of Ocean Al­liance, a non­profit or­ga­ni­za­tion spon­sor­ing oceano­graphic re­search. The Ocean Al­liance uses drones to study whales, and per­haps there is some­thing we can learn from the whale—specif­i­cally, how to live with bar­na­cles.

Bar­na­cles have a type of sym­bi­otic re­la­tion­ship with whales—it’s called com­men­sal­ism. The re­la­tion­ship is not mu­tu­ally ben­e­fi­cial. But it’s not a par­a­sitic re­la­tion­ship ei­ther; for the most part, the whale is not harmed by the bar­na­cles that live on it. (It takes up­ward of 1,000 pounds of bar­na­cles on an av­er­age hump­back whale be­fore it ex­pe­ri­ences drag!)

Maybe this type of sym­bio­sis is what boaters can as­pire to. And maybe the bar­na­cles them­selves will show us the way to this peace­ful, if slightly lop­sided, coex­is­tence. Or maybe the re­la­tion­ship could be one of true mu­tu­al­ism, al­beit a bit in­di­rect. In ex­change for the wis­dom of the bar­na­cle—a non­toxic den­tal ce­ment, a bet­ter epoxy—the boat owner pro­vides it a home.

But for now, there’s bot­tom paint.

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