Polar pedunculate barnacles piggy-back on pycnogona, penguins, pinniped seals and plastics

Abstract

There is much concern about the potential for invasive species to enter the only marine region left with no known exotics -the Southern Ocean. Attention has focused on planktonic larval travel, shipping (ballast water and hull fouling) and marine debris as transport mechanisms. There is, however, another source of transport for biota across the Polar Frontal Zone -hitchhiking on megafauna, such as seals. In this study we report the frequency and burden of barnacles Lepas australis attached to Antarctic fur seals Arctocephalus gazella coming ashore to breed at Bird Island, South Georgia. In the austral summers of 2001/2002, 2002/2003 and 2003/2004, female fur seals with barnacles attached arrived at Bird Island in late November/early December and peaked in midDecember. About 4% of female fur seals carried barnacles, with the mean burden being ~10 barnacles. Pedunculate barnacles seem, therefore, to be entering the Southern Ocean in large numbers every year in the South Georgia region and probably elsewhere. We also found adult barnacles attached to a macaroni penguin and (perhaps the furthest and fastest travelling marine larvae) young stages (cyprids) on the leg ring of a wandering albatross. Barnacle plates provide a hard substratum to which other fouling marine organisms can attach, and thus travel as secondary hitch-hikers. We found polychaete worms (Spirorbidae) and a bryozoan colony (Celleporella antarctica) encrusting a stalked barnacle attached to a pycnogonan (Collosendeis scotti). We suggest that fouling hitch-hiking barnacles (on migrating megafauna) offer a considerable natural mechanism for potential colonisers of Antarctic waters. This is of particular importance at the current time given the context of strong regional warming in the Scotia Arc-Antarctic Peninsula region.

Vagrant Antarctic fur seals at Gough Island in 2009

“…On the other hand, the lean body condition and general lethargy of the individuals reported herein, suggest that they are vagrants that might have been travelling together and made another fortuitous landfall to rest outside of their normal range ; this study). The presence of goose barnacles, probably Lepas australis, attached to the pelage of at least one of the individuals (MRI unpublished data) suggests that the animals had spent a long time at sea prior to hauling out (Barnes et al 2004;Setsaas and Bester 2006). In addition, no putative hybrids (see Anonymous 2008) were detected and no positively identiWed adult females were reported ; this study).…”

Goose barnacles on seals and a penguin at Gough Island

“…Barnes et al (2004) showed that large numbers of stalked barnacles are transported into the Southern Ocean by Antarctic fur seals and Reisinger et al (2010) demonstrated the potential transport of L. australis into the Southern Ocean by southern elephant seals. Barnacles also provide a substratum to which other marine biota may attach, and thus travel as secondary hitchhikers.…”

“…Barnacles also provide a substratum to which other marine biota may attach, and thus travel as secondary hitchhikers. For example, Barnes et al (2004) found polychaete worms and a bryozoan colony encrusting a stalked barnacle attached to a sea spider.…”

“…The establishment and spread of barnacles and any hitchhikers they may carry is currently unlikely given the comparatively low water temperatures in the Southern Ocean, yet thermal tolerances of adult and cyprid L. australis are unknown (Barnes et al 2004) and accepted predictions suggest that sea-surface temperatures in the Southern Ocean may rise by 2°C in the next century (Murphy & Mitchell 1995). Thus current global climate change trends could lower existing barriers to species establishment and spread (Barnes et al 2006).…”

Goose barnacles hitchhike on satellite-tracked southern elephant seals

“…shells and glass Wshing Xoats (Thiel and Gutow 2005) by means of a long, muscular stalk (Ray and Ciampi 1956). Stalked barnacles have also been reported on fauna such as sea spiders, penguins and seals (Barnes et al 2004;Setsaas and Bester 2006). Southern elephant seals Mirounga leonina are known to host Conchoderma auritum (South Africa;Best 1971), Lepas sp.…”