Increasing amounts of plastic pollution in oceans is allowing barnacles to disperse to new areas by hitching rides on floating plastic debris. Barnacles can survive for much longer on plastic rafts compared to natural rafts like wood or plants. This plastic-assisted dispersal has already led to at least one barnacle species becoming invasive. Areas most at risk of invasion are the tropics and southern pole, where plastic pollution is introducing non-native species that could overrun endemic wildlife. Studies have found barnacles frequently colonizing plastic debris along coastlines. To reduce further dispersal, efforts should focus on reducing sources of plastic pollution entering the oceans.

1. April 8, 2016
Prof. Brian H. Lower
Editor, ScienceBites
The Ohio State University
School of Environment & Natural Resources
210 Kottman Hall
2021 Coffey Road
Columbus, Ohio 43210 (USA)
Re: Revised Manuscript Version 1
Dear Dr. Lower,
Thank you for considering my revised manuscript for publication in ScienceBites,
we are please that you have requested minor modification of our manuscript.
Below is a detailed point-by-point explanation of how we addressed ALL of the
reviewers’ comments in our revised manuscript. To address these concerns
we:
1. Modified and/or added additional text to the manuscript.
2. Added figures.
3. Added figure citations.
We have also indicated the page and line number where new text can be found
in our revised manuscript. While these modifications increased the length of our
manuscript, we attempted to make text additions as brief as possible, while still
addressing the concerns of both reviewers.
Should our revised manuscript be accepted for publication we request that our
article appear the environmental section of ScienceBites.
We appreciate the comments and suggestions of the two anonymous reviewers
and the time and effort of the editor. The input that we received from these
people has definitely improved the quality of our manuscript.
Best regards,
Sydney M. Zartman
Reviewer 1 Comments:
1. I do not see the figures provided for this article. They are listed but are not actually there. I
may be missing them.
We agree with Reviewer #1’s comment that the figures were not visible. We have
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2. added 8 figures to the end of the manuscript.
Reviewer 2 Comments:
1. The article was fairly well written although it was tough to follow at times. That would be one
suggestion I would have is to explain more in depth some of the more scientific things you talked
about.
We did as Reviewer 2 requested by adding 5 more figures to the existing 4. We
believed adding more pictures would be best in aiding the reader’s understanding
of the scientific ideas examined in the manuscript.
2. I thought that the flow of the article was a bit choppy at times
We attempted to make the article flow better by adding better transition
sentences. These are found on page 4, line 14 and page 5, lines 24-29.
3. Something I thought was missing was that you could’ve talked a little more about was the
harmful effects barnacles have on the environment as an invasive species. I think that going
more in depth with this would help get your point across better.
We attempted to clarify the effects of barnacles as an invasive species in page 4,
lines 29-33.
4. I’m not sure if it’s just my computer that I can’t see the figures or if they aren’t actually
included.
As with Reviewer 1, we agree that the figures were not visible. We have added
them at the end of the manuscript.
Author (Arial, Bold, 10
point)
Sydney M. Zartman
Author Affiliation (Arial,
Bold, 10 point) University,
Department, Building, City,
State, Country)
The Ohio State University, Department of Arts and Sciences,
Jennings Hall, Columbus, Ohio 43210 (USA)
Article Title (Arial, Bold,
10 point, 10 word limit)
Ocean plastics lead to widespread barnacle dispersal
Article Preview/“Teaser” (10-15 words, Arial, 10 point, the teaser is NOT the same as an
Abstract)
Please insert a few brief sentences that will catch a reader’s attention. These words will display in
the search results list. Try to include a question or statement that describes your article and the
most important keywords for the article.
Increasing oceanic human pollution is causing the spread of barnacles to previously
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3. uncolonized areas.
Full Article Text (1000-1250 words, Use Arial and 10 pt. font size)
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4. Human pollution: around the world our oceans are filling up with trash and debris. In the
Great Pacific Garbage Patch (Fig. 1) alone, it has been found that over the past 40 years the
plastic debris building up in the vortex has increased 100-fold.1
Now it is estimated the North
Pacific Garbage Patch is larger than the state of Texas2
(Fig. 2). This overwhelming amount of
plastic collecting in our oceans has unexpectedly become a new mode of transportation for
sessile organisms, especially the barnacle (Fig. 3, Fig. 4, Fig. 5). With floating plastic
transporting them, barnacles will be able to travel farther than they normally could. These plastic
vessels are giving barnacles the chance to become invasive species, seriously threatening
global biodiversity.3,4
For sessile organisms like the barnacle, their main source of dispersal has always been
rafting. The natural rafts normally used by barnacles are pumice, wood, and some marine plant
life. These natural rafts are not always available as they appear in patches and have limited lives
before they are degraded.5
In the past, natural rafts were the only way for barnacles to disperse
via rafting. However, the anthropogenic floating plastics (Fig. 6, Fig. 7) found in the ocean now
are persistently abundant and are more stable than natural rafts.5
When comparing the two raft
types, natural rafts have a life expectancy measured in months, while plastic rafts are expected to
survive for decades or even centuries.6
Along with longer longevity, the plastic debris is also
durable in the sense that it can travel large distances in the ocean water. In a study done in 1993,
it was estimated that a piece of plastic marine debris had managed to travel 3,000km before
becoming stranded on shore.6
The capacity to travel such long distances shows what an
important potential vector marine debris is for barnacle dispersal.
It could be argued that even if barnacles were able to travel to a new area they are not
native to, there is no guarantee they will be able to establish themselves enough to actually live
and reproduce there; in other words there is no guarantee the barnacles will actually be able to
become invasive species. However, there has already been a case of one species of barnacle
establishing itself as an invasive species. The Elminius modestus barnacle managed to establish
itself in the Shetland Islands of Scotland after drifting there on plastic marine debris.6
With one
species of barnacle previously becoming an invasive species by plastic rafting, it can be seen that
plastic rafting has the potential to cause more barnacle species to become invasive. If more
barnacle species are able to become invasive species, they will rapidly reproduce and
outcompete native organisms for their resources – such as space or food. This competition could
eventually lead to the local extinction of the native organisms that get pushed out by the
barnacles.
The spread of barnacles is concerning not only for their own potential to be invasive
species, but also for their ability to help house other potentially invasive species. Most of the
plastics found in the ocean are smooth in texture and rigid.5
This type of surface is normally
challenging for marine life to attach to, yet the goose barnacle (Lepas testudinata; Fig. 8) was
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5. found to easily recruit on these smooth surfaces.5
In this way the goose barnacle seems to create
a sort of structural protection for other species to hide in. It is not surprising the goose barnacle is
able to create a safe haven for other species, as barnacles are known to be foundation species,
especially in rocky intertidal zones. By providing other organisms with shelter on the typically
exposed plastic pieces, barnacles can help protect these species as they travel. The combination
of these traveling species poses a global threat; specifically to coastal ecosystems.5
Coastal
ecosystems need to be preserved, as they are a major fish food source for humans.7
Also,
coastal ecosystems act as a natural filtration system for marine water, store and cycle nutrients,
and protect coastal shores from degrading factors like erosion and storms.7
The question is where, explicitly, will barnacles be having the greatest impact by utilizing
their new form of dispersal. It has been estimated that the probability of barnacle dispersal in the
tropics has doubled.6
Although the tropics are an area vulnerable to change via invasive barnacle
establishment, it is somewhat surprising that the area of most concern to researchers has been
the southern pole.6
Historically, anthropogenic debris and rafting individuals have been scarce in
polar environments.6
This scarcity is most likely due to Antarctica being relatively isolated. The
geographic isolation caused endemic marine populations in the Southern Ocean.6,3
Endemic
populations are susceptible to being overrun by invasive, non-native species.3
Losing species
diversity in endemic ecosystems is a highly unfavorable outcome.6
Diversity loss in the Antarctic
is worrisome and yet it seems to be becoming a feasible result in this area of the world as global
warming becomes an ever increasing problem. Global warming has reduced the temperatures in
the Antarctic that normally keep ice frozen.8
The reduction in ice cover will ultimately lead to a
lack of a natural protective barrier against rafting barnacles.6,3
The South Pole will be left
unprotected and barnacles will overrun it, demolishing special Antarctic organisms that are not
found anywhere else in the world.
The South Pole and the tropics have been identified as being in danger of invading
barnacles traveling on plastic debris, but where is the evidence of barnacles using this new route
of dispersal? In a study done by Goldstein et al., twenty-two sites along the South African
coastline (divided into three regions: cool temperate south-west coast, warm temperate south
coast, and sub-tropical east coast) were surveyed for floating debris colonized by goose
barnacles between June and October 2009. The goose barnacles on each object were identified
and the colony size grouped into one of four abundance classes (1-10, 11- 100, 101-1000, and
1000+). Chi-squared analyses, a one-way Analysis of Variance (ANOVA), and a post-hoc Tukey
HSD test were all used to compare barnacle species, colony size, and substrata. The results
showed that substrata of natural origin comprised 58.7% of the total colonized substrata, with
anthropogenic substrata making up the remaining 41.3% (Fig. 9). The most frequently colonized
substrata were kelp at 33.1% and plastic at 29.0% of the total colonized objects. The majority of
the plastic items were bottles, containers, and fragments of plastic sheet. The analyses showed
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6. species and substratum type are related; object size and species type are related; and colony
size and species type are related. It also determined bio-geographic regions play a role in
substrata type. This data supports the claim that barnacles have come to depend on plastic as a
major mode of dispersal. The data also shows how plastic is allowing goose barnacles to travel
to tropical and sub-tropical waters, where large, natural substrata are not common.9
The importance of invasive species should not be overlooked; modern invasions have
often been underestimated in terms of scale and impact to diversity.10
To counter the effects of
barnacle invasion via plastic rafting, debris removal operations have been implemented.
However, although these efforts are effective in preventing species introduction in limited areas,
large-scale cleanups are impractical. Efforts should instead be focused on the sources of plastic
debris, such as urban coastal sources and ocean sources, like fishing debris.11,9
Search words (minimum of three, maximum of 6, use Arial and 10 pt. font size)
Barnacle
Dispersal
Pollution
Figure Legends for accompanying illustrations, tables, graphs, and photographs (Use Arial
and 10 pt. font size)
Fig. 1: A worker attempting to travel through the Great Pacific Garbage Patch.12
Fig. 2: The orange areas show where garbage has accumulated in the ocean. The Great Pacific
Garbage Patch has a drawing of Texas over it drawn to scale to demonstrate its immense size.13
Fig. 3: A drawing of a barnacle seen from the side, as if part of its shell was removed. Its legs are
sticking out of the hard, protective shell and its back is permanently attached to the surface
below.14
Fig. 4: A sketch showing how an acorn barnacle looks before and after it begins to feed.15
Fig. 5: A close-up photo of a feeding barnacle.16
Fig. 6: Plastic bottles with barnacles attached to them.17
Fig. 7: Barnacles can attach to small pieces of plastic (as shown in Fig. 6) or large plastic objects
as seen here.18
Fig. 8: Goose barnacles are slightly different looking from other barnacles because they have a
long stalk attaching them to the substrate.19
Fig. 9: Pie chart created from Goldstein et al. data showing proportions of what substrata
colonized by barnacles was natural or human-made.
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7. References (Use Arial and 10 pt. font size)
1. Barboza, T. (2012, June 8). Great pacific garbage patch a bigger worry than tsunami debris.
Las Angeles Times. Retrieved from http://latimesblogs.latimes.com/lanow/2012/06/great-pacific-
garbage-patch-tsunami-debris.html.
2. Burns, J. (2009, August 27). Voyage confirms plastic pollution. BBC News. Retrieved from
http://news.bbc.co.uk/2/hi/science/nature/8225125.stm.
3. Mayell, H. (2002, April 29). Ocean litter gives alien species an easy ride. National Geographic
News, Retrieved from
http://news.nationalgeographic.com/news/2002/04/0429_020429_marinedebris.html.
4. (2001). Coastal ecosystems profile. PBS, Retrieved from
http://www.pbs.org/earthonedge/ecosystems/coastal1.html.
5. Gil, M., & Pfaller, J. (2016) Scientific Reports, 6.
6. Barnes, D. K. A., & Milner, P. (2004) Marine Biology, 146(4): 815-825.
7. Whitehead, T., et al. (2011) Crustaceana, 84(5-6): 635-649.
8. Kaiser, J. (2002, April 24). Trash-surfing aliens invade. Science. Retrieved from
http://www.sciencemag.org/news/2002/04/trash-surfing-aliens-invade.
9. Goldstein, M., et al. (2014) Marine Biology, 161(6): 1441-1453.
10. Carlton, J. (2003) Hydrobiologia, 503: 1-8.
11. Aliani, S., & Molcard, A. (2003) Hydrobiologia, 503: 59-67.
12. Jordan, C. 2013. Traveling through the garbage patch. The Great Pacific Garbage Patch.
13. Grimwade, J. 2014. There is an island of trash the size of Texas in the Pacific thanks to a
worldwide network of gyres driven by currents and wind that trap light plastic waste. The Garbage
Eaters. Newsweek.
14. Lair, L. 2010. Barnacle shown upside down and permanently attached to their shell.
Ladybug's Lair. Blogspot.
15. Willhoft, L. 2011. Diagram of acorn barnacle feeding. Kaiwah Nature Notes.
16. Guy, S. 2012. Feeding barnacle. A cheap photo close-up option. Reefland.
17. Dickens, L. 2009. Bottles with Barnacles. California Current Ecosystem.
18. Gillam, K. 2016. Beachcombing. Goose barnacles but no crabs. Funny, I see these bits of
plastic at work used to secure banana pallets. Twitter.
19. Smith, W. 2016. Goose barnacle close-up. Goose Barnacles & Geese on the Shoreline.
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8. Glossary (Use Arial and 10 pt. font size)
Great Pacific Garbage Patch- Stretching from the North American west cost to the coast of
Japan, debris and garbage is constantly moving due to circular ocean currents (when warm and
cold currents come together).
Sessile- An organism (animals are exclusive to the sea) locked in one place, stationary.
Barnacle- Stationary shellfish that secures itself to an array of surfaces. They have light bristly
legs that help to feed through filtering the water around them for plankton.
Rafting- Sizable mob of floating vegetation in a body of water, carrying organisms from one
place to another.
Anthropogenic- Human influenced environmental change, e.g. pollution.
Foundation species- Organism that has an essential role in the formation of a community.
Rocky intertidal zones- The point where jagged shorelines and ocean waves meet.
Coastal ecosystems- Complicated and diverse area of life, seaside areas.
Endemic ecology- Organisms that are narrowed to a specific place or region.
Invasive species- Organisms that don't originate from the ecosystem that they're overrunning,
most likely causing damage to that ecosystem.
Fig. 1
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9. Fig. 2
Fig. 3
Fig. 4
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10. Fig. 5
Fig. 6
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11. Fig. 7
Fig. 8
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12. Fig. 9
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