Naturespeak A naturalist's view of the world

October 18, 2007

Mussel Power

Filed under: Uncategorized — wykes @ 9:05 pm

  Not recalling the last time I was contacted by a Japanese Television station, I eagerly answered the call from a station representative.  “We are to do a documentary on the Zebra Mussel,” the polite female voice at the other end of the line stated,” and we wish to know if we can find them at Lake Erie Metropark.”  The film crew was flying in from Japan the following week and they were setting up location shoots.  I answered that the recent low water and other factors had greatly reduced the availability of near shore zebra mussels, but I’d scope out the situation.

  A dutiful trip out to the Erie shore yielded only four live mussels and one pitiful colony cluster left high and dry by a wind tide.  I found myself getting a bit distressed due to the lack of alien species, so I carefully collected some of the live ones as if they were rare biological treasures.  This was for the edification of millions of Japanese citizens, after all, and I didn’t want to be the one to let them down. I did send them pictures of some fresh specimens (see here in profile) to prove they existed.

  A call to the production company a few days later found me revealing that there were no giant colonies to show off, but that I could provide some specimens for live photography.  Igume, that was the phone voice’s name, politely said “forget it” and informed me that they found someplace else that had “bunches of them.”  My big opportunity to break into the foreign media market was immediately crushed. I almost asked for a second chance, but took it like a man.

  In retrospect, the odd thing about this whole affair was that I was actually saddened by the lack of zebra mussels. It was, in fact, very strange that I even had to search for them in the first place. Zebra Mussels came into the Great Lakes in the 1980’s via the ballast water dumped by ocean going vessels originating from the Caspian and Black Seas of Europe.  The introduced zebra mussels thrived in our warm near shore waters and began to show up in the Detroit River and Lake Erie by 1988. Within a few years they exploded to the point were they covered every solid surface under the water and clogged city water intakes.  We, of the lower lakes, were at the epicenter of this explosion. The horrible threat of an ecological calamity reared its ugly head and the critters were daily headline material.

  Now, many decades later, they are no longer front-page news.  Lake visitors don’t notice them, power companies make it a regular thing to scour their water intakes, and our local piers are not encrusted at the water line like they once were.  The problem has not gone away, but the perceptions of it have changed.  So, what gives after twenty years of occupation? According to most reports, the regional population has stabilized and is actually going down in some areas (although they are still spreading like wildfire into western waters).

  While in the process of collecting for the “Mussels for Media” campaign, a fellow walked over to me and asked what I was doing.  His response, once told, was “Oh, I hear that they have cleaned up the lakes.”  I explained that this phenomenon wasn’t necessarily a good thing and the Zebra mussel negatives still far outweigh the positives. 

  Now, it is true that there are a few slightly positive effects of this alien invasion. Some studies indicate that mussel eating ducks like bluebills and goldeneyes eat the zebra fare like there’s no tomorrow.  Some bluebills stomachs were 99% full of zebra mussels.  The mussel-clarified water has allowed deeper penetration of sunlight to increase plant growth – providing more food for the likes of the Canvasback ducks that come here to feast on water celery. The price paid by hosting two decades of zebra mussels is a steep one, however.

  First of all, the perception that clean water is good water isn’t really true.  Zebra mussels are filter feeders, which means they constantly strain organics out of the water (look here at a live mussel, embedded in sediment, and notice the two openings called siphons which suck in and expel water).  The action of millions of these tiny aquarium filters clarifies the water by removing the tiny suspended algae particles which normally clouded it. This clouded water contains the nutritious soup that native animals like microscopic zooplankton depend on.

  To make things worse, zebra mussels are finicky eaters and they literally spit out a type of potentially toxic blue green algae called Microcystis.  By doing so, this population of this bad alga is enhanced well above normal levels.  Another type of stringy algae, called Cladophora, also benefits from the immense pile of droppings given off by beds of mussels.  These plants then wash up as huge mats onto our beaches.

  Perhaps the largest ecological effect to date is the most subtle. There are over 40 species of native mussels that call our waters home and these poor fellows have taken a devastating hit.  Not only do both the native and non-native creatures feed on the same material, but the pesky foreigners colonize the larger native shells and choke off their food supply. Many species of North American mussels (or clams, if you wish) are becoming rare because of this.

  In short, even though the excitement of the original invasion has died down, the daily pressure from Zebra Mussels has completely re-shaped the waterscape. They are here to stay. We can only hold our collective breath and see what becomes “normal” over the next few decades.

1 Comment »

  1. Great Post, I’ve been looking for an article on the subject for awhile now.

    Comment by gambling — January 21, 2011 @ 11:13 pm

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