Problem Statement and Background Figure 1. USGS Nonindigenous Aquatic Species Map highlighting the zebra mussel spread across the US.
The zebra mussel (Dreissena polymorpha) is an invasive species that was introduced to North America in the late 1980s/early 1990s (Bossenbroek et al. 2007). Zebra mussels are native to Eastern Europe (Gelembiuk et al. 2006) and are assumed to have traveled across the Atlantic Ocean in the ballast water of ships (Keevin et al. 1992). The zebra mussel is mainly a freshwater bivalve, however it has been found in brackish areas with low salinity (Gelembiuk et al. 2006). They have been spotted in the Susquehanna River and in the northern neck of the Chesapeake Bay according to the USGS Nonindigenous Aquatic Species Map (Figure 1). The zebra mussel is known to feed on phytoplankton and severely depletes phytoplankton abundance when zebra mussels have become established (Higgins and Vander Zanden 2010). The zebra mussel has been found in large numbers as far west as Kansas and as far south as Louisiana since its introduction to the Great Lakes in the 1980s (Figure 1).
An adult zebra mussel lives approximately 2-3 years and a female can produce approximately 40,000 eggs per reproductive cycle, which allows the spread of this invasive species to occur rapidly (VDGIF 2016). One of the main dispersal factors of the zebra mussel is the release of ballast water containing zebra mussel larvae in lakes, rivers, and streams (Keevin et al. 1992). The release of ballast water in rivers and lakes not only contributes to the spread of zebra mussels upstream, but also provides expansion routes downstream (Horvath and Lamberti 1997). After being established upstream, the spread of veligers (larva stage of mussel) downstream is inevitable (Kraft et al. 2002; Bobeldyk et al. 2005). The veligers and zebra mussel eggs can be dispersed in multiple ways which in overland transport of recreational boats (Nalepa and Schlosser 1993), streams connected to infested lakes (Johnson et al. 2006), and the release of ballast water in streams and lakes (Keevin et al. 1992).
While each of the dispersal methods are significant in the spread of the zebra mussel, stream connectivity accounts for an estimated one-third of all distribution (Johnson et al. 2006). Eggs and zebra mussel larvae can be found as far as 18 kilometers downstream from an infested lake (Horvath and Lamberti, 1999). Bossenbroek and Bodamer (2008) determined that in wetland streams with vegetation, the downstream dispersal of veligers was decreased when compared to streams with little or no vegetation. Wetland streams limit the dispersal of veligers downstream because of the macrophyte’s ability to hold suspended particles on their leaves and by the reduced water velocity from vegetation (Miller and Haynes 1997; Horvath 2004). Other possible explanations for the decreased veliger abundance can be attributed to unsuitable water characteristics, limited substrate availability, and increased predation (Bossenbroek and Bodamer 2008).
Overland transport of these recreational boats is believed to be the largest contributor to infestation of zebra mussels in inland lakes (Nalepa and Schlosser 1993; Johnson and Carlton 1996; Johnson and Padilla 1996; Schneider et al. 1998; Buchan and Padilla 1999). Zebra mussels can be transported over land and become introduced to uninfected lakes because of their ability to survive out of water for several days (Ricciardi et al. 1995).
Zebra mussels are responsible for multiple problems in the ecosystems of which they are introduced to, including reduced dissolved oxygen (Canale and Chapra 2002), increased water clarity (Higgins and Vander Zanden 2010), and alterations to the concentrations of dissolved nutrients including soluble reactive phosphorus, nitrate, and ammonia (Makarewicz et al. 2000; Bykova et al. 2006; Miller and Watzin 2007; Strayer 2009). Zebra mussels are changing the physical and chemical conditions of the ecosystems they inhabit (Kirsch and Dzialowski 2012) and are responsible for the depletion of phytoplankton abundance in inhabited bodies of water (Higgins and Vander Zanden 2010). Zebra mussels severely impact hydroelectric plants across the United States (Bossenbroek et al. 2007), as observed in multiple sites in Asia (Bobat et al. 2004). The impacts not only affect humans, but the benthic predators of the ecosystems as well (Beekey et al. 2004). Beekey et al. (2004) observed that zebra mussel establishment inhibited foraging success of sculpins, bullheads, and crayfish when foraging for isopods. It was observed that in general, when zebra mussel coverage increased, the foraging success of predators decreased (Beekey et al. 2004).
Once the zebra mussel becomes established, it is difficult to eradicate because of the use of their byssal thread and reproductive capabilities (VDGIF 2016). Unlike other mussels, the zebra mussel can latch on to various surfaces forming beds resembling dense oyster beds (VDGIF 2016). The Chesapeake Bay Foundation (CBF) and the Maryland Department of Natural Resources (MDNR) will work together to prevent the spread and further establishment of the zebra mussel in the Susquehanna River and northern neck of the Chesapeake Bay. Studies have shown that increased vegetation in waterways (Bossenbroek and Bodamer 2008), the inspection of boats before and after entering a body of water (Bossenbroek et al. 2007), and the release of ballast water before entering separated bodies of water (Keevin et al. 1992) all can prevent the spread of the zebra mussel. A visual inspection for vegetation and a spray down of the boat hull to remove sediments and any gritty organic matter has also been known to reduce the spread of zebra mussel larvae (VDIGF 2016). The CBF and MDNR aim to limit the amount of zebra mussels introduced and thus slow the process of their establishment in uninfected lakes, streams, and rivers.
The objective of this management plan is to first identify infected bodies of water in the Chesapeake Bay watershed and then implement techniques to prevent and slow the spread of the zebra mussel in at least 50 percent of the identified infected bodies of water. This will be accomplished within eight years of recognizing the infestation of the body of water. This can be quantified by determining how many of the identified bodies of water we can implement these prevention techniques in as well as whether or not they can sustain the techniques introduced. We will monitor the infested bodies of water every six months to assess success. We will focus on the Susquehanna River and the Chesapeake Bay due to increased zebra mussel sightings over the past few years.
To identify infested bodies of water in the Chesapeake Bay watershed, we will enlist the help of citizens who are regular boaters and fishers. The posting of information will help let the citizens know that this management plan is occurring and who they can contact for information or to report a sighting. After a citizen reports zebra mussels are in a body of water, professional identification will follow. The use of only professional identification on such a large scale would be too expensive. By enlisting the help of citizens traveling to lakes, streams, and rivers we will be able to save money and time. When someone informs the agency of the location of an apparently infested lake, an agency member will travel to confirm or deny a sighting. The identification of a zebra mussel by an agent will be accomplished by obtaining a picture of the zebra mussel(s) and if possible, removing the mussel from the body of water.
Decrease Spread and Transport
To prevent the spread of the zebra mussel, we will use a studied technique to increase macrophyte abundance in streams and rivers as demonstrated successfully by Bossenbroek and Bodamer (2008). Bossenbroek and Bodamer (2008) found that in streams with a higher abundance of vegetation, zebra mussel eggs and veligers could only travel a certain distance. To successfully implement this technique, we will have to research what native plants can be introduced efficiently. This, however, cannot be done until areas have been designated as infested. To quantify this technique we will have to track how much plant matter is added to each body of water and take water velocities of different areas to determine if the macrophytes are slowing down the water. Bossenbroek and Bodamer (2008) found that the decrease of water velocity is important in slowing down the spread of the zebra mussel. Increasing macrophyte density is a way to decrease water velocity without drastically altering the ecosystem.
Boat checks are going to be used to prevent the overland transport of zebra mussels. Overland transport is a large component of the spread of the zebra mussel across long distances (Nalepa and Schlosser 1993; Johnson and Carlton 1996; Johnson and Padilla 1996; Schneider et al. 1998; Buchan and Padilla 1999). There is no way to enforce boat checks on recreational vehicles without the introduction of a new law, so instead education will be pursued. Signs and posters will be created and posted outside of lakes and boat docks that include information about the zebra mussel. These educational posters and signs will include information about how easily the zebra mussel is spread, how the boater can prevent their spread, who to contact if they positively identify a zebra mussel in the body of water, and how to positively identify a zebra mussel.
Justifications for Budget Personnel The Project Coordinator will be responsible for the management of the team by directing the Technician Leader and the six technicians in their overall duties for the course of the eight-year management plan. The Project Coordinator is also responsible for communications between the Chesapeake Bay foundation and the Maryland Department of Natural Resources to ensure cooperation and efficiency. The Project Coordinator will also be responsible for determining the priority of sites to be visited.
The technician leader is responsible for the everyday management of the six technicians including hiring and monthly performance reviews as well as reporting on overall project progress to the project coordinator. The technician leader is responsible for the timeline being met and addressed efficiently as well as periodically doing fieldwork.
The technicians are responsible for preforming the everyday tasks such as map and poster construction, visits to reported sightings, assessing sites visited, and maintenance of equipment.
The project coordinator and technician leader will receive a yearly benefit of 34% of salary to account for increased cost of living as well as dental and medical benefits. The technicians will receive a yearly benefit of 15% of salary. Inflation is included in all pricing as a 1.021% increase for each year.
Many of the supplies listed in the budget only need to be purchased once due to their quality. The supplies that fall under this category include all of the scuba gear, waders, GPS’s, waterproof cameras, and boat trailer. With proper maintenance these items can all be bought once which will be cheaper than renting materials frequently. The scuba gear and waders are very important in identifying an infested body of water. To properly identify a zebra mussel the technician will have to get into the water and locate zebra mussels to consider the body of water as infested. The waterproof camera will be used to document the zebra mussel while it is in the body of water and the plastic bags will be used to store mussels if they can be removed with the scuba knife or in another way. Educational materials will be used to spread information and will be posted around frequently used recreational bodies of water.
Equipment The F-350XL Diesel is necessary for travel needs, diesel engines have higher mpg rates and will be important in saving money over the course of the management plan. The truck is also necessary for towing the boat to locations where the technicians will check for zebra mussels and plant subaquatic vegetation (SAV). The planting of SAV is the most important part of the management plan as it is the main technique that will be slowing the spread of the zebra mussel. The Tahiti Daycruiser is a used boat that is necessary for checking for zebra mussels and planting SAV. It will also be used to provide an example for boat checks that can be done when exiting water to prevent the spread of the zebra mussel.
The maintenance of scuba gear, the truck, and the boat are necessary to keep these items in good shape so that new materials will not need to be purchased. Scuba certification is necessary for the technicians so that all can preform the identification of zebra mussels in the water. Boat licensing is necessary for all of the staff so that everyone is qualified to operate the boat.
Travel will be done mostly in the truck and boat; flights will not be necessary due to the close proximity of the sites that will be identified. The estimated mileage is 2,000 miles at $0.55 per mile for the truck and 300 miles at $0.75 per mile for the boat. Hotel stays may be necessary for long drives but will not be frequent; the per diem rate in Maryland is an average of $91 per person.
Indirect Costs This is the overhead costs that are required to keep the agency running, the rate of 26% was applied to the total sum of each year to account for lighting, heat, computer use, servers, etc.
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