Problem : Mussels: Loss of native species and the invasion of zebra mussels
Mussels provide a number of valuable ecosystem services in rivers and wetlands. Most significantly, mussels are a food source to a number of small animals and provide water filtration, clearing suspended particles and pollutants from the water column. In addition, mussels are good bioindicators. Due to their permanent anchoring on the riverbed and requirement for high quality water, large populations of mussels are indicative of waterway health.
The Allegheny River was once considered the richest stream in Pennsylvania for freshwater mussels, with over 50 species identified. The loss of suitable substrate and streamflow from the lock and dam system, as well as general habitat degradation has disrupted this natural habitat and the number of species has declined to 30. The Allegheny is home to two federally endangered species, the clubshell, Pleurobema clava, and the northern riffleshell, Epioblasma torulosa rangiana.
The zebra mussel, a species native to Russia, began appearing throughout the US in the late 80’s and was first identified in the Lower Allegheny in the early 1990’s. The infiltration of the zebra mussel in the Great Lakes region was a watershed moment for invasive species legislation, leading to the passage of the National Aquatic Nuisance Prevention and Control Act of 1990 (Patnaik in Wakefield and Faulds 2003). They have colonized major parts of the Great Lakes, Arkansas, Cumberland, Mississippi, Ohio, Tennessee and and Hudson Rivers (USFWS 2011). Since their arrival, the species has proliferated to become one of the major freshwater invasive species, due in part to their ability to attach to boats and survive out of the water for up to five days, which allows overland dispersal (PSU Seagrant). Zebra mussels are also spread in the larval stage through ballast water, and may be spread by recreational users on boats and in buckets (USFWS 2011).
Source: USGS http://fl.biology.usgs.gov/Nonindigenous_Species/Zebra_mussel_FAQs/zebra_quagga_map/zebra_quagga_map.html
Though the mussels prefer to anchor to hard, calcareous materials, including limestone, concrete, and the shells of other mussels, they may attach to a range of surfaces including intake valves and pipes, or the surfaces of the lock and dams of the Allegheny (USFWS 2011). In addition to problems caused by water pipe clogging, Zebra mussels filter plankton from the water column, making this food sources unavailable to native species (PSU Seagrant). Zebra mussels, like many filter feeders, are bioaccumulators, and concentrate contaminants which is transferred up the food chain as they are consumed (PSU Seagrant)
They out compete native species, threatening their survival. Ongoing measures in the upper Allegheny and Allegheny reservoir to protect endangered mussel species downstream are expected to be instituted this year (CITE)
Recommendation 1:
Monitoring Regime for Early Identification and Management
For invasive species introductions, swift identification can prove vital to the success or failure of a management regime (CITE). Though the zebra mussel has been present in the Lower Allegheny for over 15 years, there has not been significant spread upstream. In part, this may be due to a proactive monitoring regime. In the late 1980’s, Pennsylvania was able to establish a grant-supported volunteer monitoring program for zebra mussles (Shaw in Wakefield and Faulk 2003). Due to detection design challenges in planktonic samplers and relatively few sightings, the monitoring regime has declined in scale, but was still active as of 2003. The species richness of the Lower Despite the lack of sightings in the Lower Allegheny, maintaining an effective monitoring team will help control the spread of the zebra mussel in the Lower Allegheny. Due to the mussel species richness in the Lower Allegheny, there should be a natural constituency and state support to support monitoring activities.
Recommendation 2: Public Education Campaign
In part, the extent of zebra mussel invasion across the country is due to its ease of dispersal. In it its various life stages, mussels can be spread through water, on vegetation, and on boats and equipment (PSU Seagrant). Due to the small nature of the organism, recreational users may contribute to the dispersal of zebra mussels unintentionally. As a waterway with high recreational use, public education is particularly important. The public education campaign should focus on species identification and safe cleaning practices for all boating equipment.
