More zebra mussels found in lower Susquehanna River

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Well, where there is one, there are more. Not the official press release, but this article is running in todays Baltimore Sun. This is going to be interesting. Unlike many systems where zebra mussels have invaded, the lower Susquehanna has essentially little to no mussel community with minimal reproduction, and is extremly turbid and nutrient rich following most rain events.

Sounds like it'll probably be just like the Maumee and the other southern shore Erie drainages... Low abundances of weak metapopulations where there's pools (take out the dams, and then you don't have a zeeb "problem"). The Unionids didn't even notice. Nor has anyone else, even tho they've been throughout the lower Maumee almost as long as since the "invasion" began. I would speculate they've been in the Susq for awhile, just no one noticed, if the conditions are similar.

Todd

Yes the upper parts they've been known especially in PA, but when I mean lower I mean from the MD border to Conowingo dam, which is essentially the last dozen or so miles before it enters into the bay and becomes tidal and eventually salt. I have no clue what their salt tolerances are unfortunately. There are enough large dams that the spread may have been delayed, but boats still move between pools on trailers. Where they go from here is totally up to boats since on the Susq. flats you have a weak saltwater area with minimal connections to freshwater, except that wonderful canal that connects Ches. Bay to Delaware River Bay. "Boating capital" of the country + zeebs = ???.

I'd speculate they'll have little trouble with the salt, in fact, they might enjoy it. What'll be interesting to check out are the competitive and predatory interactions they don't currently have in the interior. I think Dave Strayer has been looking at some of this in the Hudson. I need to check his site, I haven't done that in a while.

Are the big dams letting off hypolimnetic discharges? If not, they're probably facilitating downstream dispersal, not hindering it. The dam pools can become hyperdense sources, the free-flowing rivers themselves are population sinks (the "ocean" off the "island", so to speak in biogeographic terms). Thus the problem of intake fouling, which occurrs above, not below the dam. And is perhaps why we have low detection success in the free-flowing segments.

Are they dragging you guys out there to look at this? Is it too turbid to dive in the summer? Probably wasting your time until you can get under the water, although with vegetation die back, I've had really good success finding dead specimens in floodplain cuts. Corbicula will show you the way That's one way to detect them in low abundances.

Todd

Nope, no hypolimnetic releases at least not to the extent like SE reserviors. Flows are extremely variable too; no minimums, mostly when it needs to get out dump it and when it needs to be kept in shut it off. I think most of the Hudson stuff is tidal fresh, which is pretty much this same situation with less impoundment. It also had a much better unionid community (Strayer 1994) than what persists in the lower Susq. Not sure if there is anything new, I haven't checked recently either. We had Tom Jones out with us and some diverse found very little, mostly OLD Elliptio. As to diving, I think in the dry spouts of summer you have the visibility, but when you get a good rain you should see what that plume does to the bay via the aerial imagery. With the available nutrients in the Conowingo Pool I would think an explosion is possible. The unionid population is barely there. Now the Potomac, that has a much better unionid population, especially in the tidal fresh region. A nice control or comparison since its first barrier/dam is much farther upstream than the Susq. though both essentially on the fall line. Other than one of our biologists being on the invasive species matrix team we are not involved anymore. Then again, its literally happening as we speak.

What's the calcium and magnesium levels like in those rivers? Are they as poor as it is further south? I don't have the PA bedrock map yet.

As much as I think the reputation is overblown, it's still sad to continuing getting more "replicates". We are just one big ecological experiment run awry.

Todd

There are somelong term ("Core/Trend") monitoring stations at the bottom of the river in MD but I'm not sure what they collect. Many of them are web accessible. I think they are called Eyes on the Bay or something. Not sure what PA has, or the Susq. River Commission, but I'd imagine there are similar things related to Bay monitoring. I couldn't tell you about the calcium and magnesium or geology. The ions are probably pretty low. Shells dissolve really fast after the they die around here especially on the Coastal Plain.

The official press release below.

Invasive Zebra Mussels Found in Maryland, Susquehanna River
DNR Calls on Boaters to Help Prevent Spread of Harmful Zebra Mussels
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Annapolis, Md. — The Maryland Department of Natural Resources recently confirmed the presence of zebra mussels in the lower Susquehanna River. The latest zebra mussels found in Maryland were recovered from a boat docked in Harford County. Biologists are calling for vigilance and assistance from boaters and anglers to prevent spread of harmful zebra mussels.

“Maryland’s freshwater reservoirs have a lot to lose if zebra mussels get in,” said Dr. Ron Klauda, a biologist with the Maryland Department of Natural Resources. “By taking a few simple precautionary steps now, boater and anglers can help prevent the devastating economic impact and ecological havoc caused by this invasive species.”

The zebra mussel, a small freshwater mollusk from the Caspian Sea, has already infested much of the Great Lakes region, causing economic and ecological damage. Free-swimming zebra mussel larvae will stick to any hard surface and begin to grow. As the mussels grow, they physically clog water systems, coat boat bottoms and any structures in water. Zebra mussels have encrusted boats, ruined power plant intakes, and changed the way municipal water systems must operate. Ecologically, zebra mussels are killing native mussels, including endangered species. Their presence been connected with widespread ecological impacts from increasing toxic microorganisms to declining duck populations.

Since inadvertent introduction into the Great Lakes in the mid-1980s, the zebra mussel has spread rapidly into freshwater habitats from Louisiana to New Hampshire. While the species free-swimming larvae move rapidly with natural currents, the main mechanism for its transport up rivers and to inland lakes is hitchhiking with people.

“Recreational boaters can unknowingly carry zebra mussels around in their bilge, minnow buckets or aquatic vegetation on their trailer.” explained Klauda. “In Minnesota and a number of other states, fishermen and boaters have been very effective in halting the spread of this serious pest by a little preventative maintenance. We hope that Maryland boaters will help us by washing down hulls, cleaning bilges, removing aquatic vegetation from props and trailers, and limiting movement from place to place, particularly from the Susquehanna River to other waterbodies.”

Boaters and anglers who use the Susquehanna, the only water body in MD where zebra mussels have been found, should be particularly careful to avoid spreading these invasive species to other state waters.

DNR has teamed up with the Chesapeake Bay Trust to post signs at all Maryland Boat ramps to inform Maryland boaters about the problem and how they can avoid being carriers. For the past few years, owners of recreational craft of trailer-able size received brochures from DNR by mail informing them how to prevent zebra mussels’ spread.

“The rate of spread of this species is nothing short of astounding,” said Klauda. “We’ve been watching for it and trying to prevent its arrival, but here it is. Time will tell if this species will become established in the Susquehanna, but its record elsewhere is pretty grim.”

The stakes are high for uninfected areas. The U.S. Army Corps of Engineers calculated economic losses between 1993 and 1999 at over $5 billion, even without accounting for ecological damage.


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December 9, 2008 Contact: Olivia Campbell
410-260-8016 office I 410-507-7525 cell
ocampbell@dnr.state.md.us