The Mussel Threat

Zebra Mussels Filtering. Image from:

Zebra Mussels Filtering.

Mussels. The word usually conjures up images like a plate of steamed shellfish swimming in melted butter and garlic, the bottom rungs of a ladder too long submerged, or a few hours of scraping work. It’s all dependent on your perspective for the most part. Unfortunately, mussels are more than that, and can be detrimental to the environment. In North America right now, we are dealing with the spread of Zebra and Quagga mussels (Dreissena polymorpha, and Dreissena bugensis respectively). They are a serious issue, and one that we as divers can have a hand in either helping or hindering.

Now, I know a lot of people think that nature can adapt, but when it comes to invasive species, that’s just not the case. Zebra and Quagga mussels are both native to Eastern Europe, and in their native environment, they are a minor nuisance but part of the ecosystem. They were first observed in North America in the Great Lakes in 1988 and 1989 respectively, and are believed to have been introduced via ballast water dumped in the lakes. Since then, they have spread via waterways and boats throughout the USA and Canada.

A severely infested boat hull. Image from:

A severely infested boat hull.

Initially, the response to the mussel invasion from divers was somewhat positive. Their mass filtering of water increased vis, and for inland divers in North America, good vis is worth its weight in gold. Soon though, they began to observe that the mussels were causing excessive biofouling on wrecks. And then the costs began to roll in as businesses had to deal with infestations of the mussels on their vessels. Homeowners that drew water from nearby lakes found their water intakes clogged. Sewage and power outlets and intakes in lakes were similarly fouled. The costs began to mount rapidly.

The next cost hit fishing. The phytoplankton that support the larger food web are consumed by the filter feeding mussels. As a direct result, fish stocks drop off. This act also has the added actions of exposing fish and other animals to higher levels of toxic materials, and increasing the acidity of the water via exposure to and the breakdown of the mussel’s pseudofaeces (waste products). The end result is a deteriorating ecosystem and, by extension, a deteriorating diving environment.

So what can we do as divers? A lot. First is equipment maintenance. While few divers are down long enough to allow for encrustation, Zebra and Quagga mussel larvae are remarkably tough and travel unreasonably well. Check and see if you’re diving in waterways that suffer from these invasive species. If so, sanitize your gear after you’re done diving before diving in the next location. Check to see what types of soap or cleaning solutions your gear is safe to be cleaned with, and give everything a good scrub. It’s an afternoon’s worth of work, but it’s well worth it if it means that you don’t inadvertently transport something nasty to an area unaffected by these invasive pests.

The reality of mussel infestation in the Great Lakes. Image from:

The reality of mussel infestation in the Great Lakes.

The other thing applies to boat divers who own their own boats or who are planning to travel with a boat to go diving. This year, my home province of British Columbia introduced an inspection regime for boats entering the province. Why? Because even that dry-ish looking lump of mussels on your boat can contain live mussels, waiting to spread into new waterways. Clean and sanitize your boat, or the boat that you’re planning to use. There are a lot of guides to doing so available online, and doing it yourself is probably cheaper than being caught at an inspection point!

Zebra and Quagga mussels are a serious invasive species in North America. As divers, if we want to continue to enjoy good diving conditions where there’s more to see than just mussel encrusted everything, we need to do our part and encourage others to do their part to halt the spread of these innocuous looking shellfish. To keep things in perspective, these mussels and their larvae can live up to 30 days after your boat or gear has been in the water in the right conditions (wet patches, bilges, clumps of encrusted mussels, wet gear bags etc…). Once in place, they are nearly impossible to remove, and can only really be managed, usually at extreme expense (millions of dollars are spent annually). I want commercial diving work, but not at the cost of the ecosystem of the lakes that are part of my life! Divers have spearheaded a number of environmental causes, and this is one that we can’t afford to let slide.

Boat Sanitation: (pdf download) (website)

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About the author

Graeme is a professional diver, qualified as a PADI and SDI Divemaster, DCBC 40m Unrestricted Commercial Scuba Diver, 30m Restricted Surface Supply diver, and CAUS Scientific Diver Lv.2. Graeme has an Associate Degree of Arts in Environmental Studies, where he focused on archaeology and physical geography, and an Advanced GIS certificate.