Lets Talk About Invasive Seaweeds!

Seaweed. Yuck. The stuff that gets wrapped up in your legs when you swim, the foreign being that touches your foot and makes you scream like a little girl (because it's DEFINITELY a sea monster), those gross crunchy pieces that stick to you when you lie in the sand... this is what most people think of when I say seaweed!

However, they are also extremely important to marine (and freshwater!) ecosystems. Seaweeds are a major element in many under water food chains; they are eaten by everything from small invertebrates to larger marine animals. Seaweeds (and especially larger kelps) are also used as nursery grounds for marine creatures as well as year-round habitats for benthic and pelagic animals.

This is all fine and true for native seaweed species.

But lately, more and more places around the globe are being negatively impacted by introduced/invasive seaweeds. Lets use Codium fragile spp. (aka "The Oyster Thief") on the east coast of North America as an example.

Looks pretty harmless right? 

What about now?

This beach in Massachusetts is COVERED with invasive Codium fragile spp. Doesn't look so harmless now, if you catch my "drift" [haha :)]

So why is it so awful? Messy maybe... but how is it affecting the marine ecosystem in these places? Let's take a closer look...

Codium fragile spp. was originally isolated to the Western Pacific ocean, specifically in Japan. But several different vectors have allowed C. fragile spp. to travel far from their native habitat, including Europe, South Africa, South America, New Zealand, and the East and West Coast of North America. So what vectors allowed this species to be introduced?

Sometimes C. fragile spp. hitchhikes on oysters from Japan, and is also used as a packing material:

[Fun Fact! Codium fragile spp. is called an "Oyster Thief" because it attaches to oysters and then unintentionally floats them to the surface (and kills them!)]

Codium fragile spp. may also travel as a fouling organism on ships hulls or in drag nets:

These vectors are common to many invasive species, and allow easy transmission from one area to another.

So does it affect the marine ecosystem? Codium fragile spp. has a severe impact on Aquaculture - especially to the oyster industry. For example, PEI has an average annual loss of $150, 000 (!!!) from their oyster industry which is caused only by Codium fragile spp. Drift seaweed also forms matts on the beach which may rot and smell, which may impact daily life of near beach residents as well as tourism industry of the area. Finally, invasive species often out-compete native species, disrupting ecosystems and even causing extinction of native species... YIKES!

So how can we stop the spread of invasive species? Unfortunately, once a species is introduced and established it is VERY hard to get ride of... so prevention is a much better tool than control. So lets look at some prevention techniques...

1. Stop introducing them! If species like Codium spp. are used as packing material, it takes only one package tossed overboard to start an invasion. The same goes for aquarium dumping... for example, the invasive species Caulpera taxifolia is actually banned from California because of its invasive nature [read more here!). Once a harmless aquaria plant, it has now disrupted ecosystems all over the world and caused extinctions of native taxa.
2. Inform, Inform, Inform! The public needs to know that invasive species are not always (and usually not!) a good thing. The more easily available the knowledge is, the more preventable invasions may be.
3. Think Ahead! Invasions are (usually) preventable. Hull fouling and ballast water dumping are two of the major ways that invasive species are introduced. Anti-hull fouling paint was once very popular (see here) but many ingredients used were found to be toxic to marine ecosystems. Silicon based paints have been found to reduce species adherence, and regular scraping (and proper discarding) of fouled hulls has been found to reduce invasions. As for ballast water, many countries now require incoming ships to dump ballast water in inter nation waters where organisms are unlikely to thrive and invade; the problem is this practice is often not heavily regulated... which comes back to education :)

So hope you learned a little bit about seaweed invasion today... tell you friends! Tell you family! We can all help prevent invasive species from inhabiting our waters!

P.S. A happy ecosystem is an invasion-free ecosystem :) 

[I know their dead... but it's cute right?!]