Patterns of dreissenid mussel invasions in western US lakes within an integrated gravity model framework.

Freshwater invasive species, such as the quagga mussel (Dreissena rostriformis bugensis), are causing over $1 billion USD annually in damages to water infrastructure, recreation, and the environment. Once established, quagga and other dreissenid mussels are extremely difficult to eradicate. Preventing the spread of these invasives is critical and of high management concern. Invasive dreissenid establishment is predicated upon both successful dispersal from a source and suitable habitat in the uninfested waterbody to which they are transported. Recreational boaters have become predominant dispersal vectors making it possible to forecast the risk of invasion of waterbodies for more targeted management and prevention. We developed an integrated mussel dispersal model that couples a constrained gravity model and habitat suitability model to forecast future invasions. The model simulates boater movement between lakes, the likelihood of boats transporting mussels, and the likelihood that those mussels survive in the environmental conditions of the new lake. Model output was most sensitive to changes in boater threshold, then buffer zones, while not as sensitive to changes in habitat suitability. From an initial infested source pool of 11 among 402 Western inland US lakes, we forecast additional lakes infested in several possible simulation scenarios. Constraining movement reduced connectivity between waterbodies with amplifying effects at different distance levels. This model can be used to determine waterbodies most at risk for dreissenid mussel invasion and to highlight the importance of multifactor integrated models in environmental management.

What we know and what we think we know: Revealing misconceptions about coastal management for sandy beaches along the U.S. Atlantic Seaboard.

Management of coastal areas is necessary to maintain and protect existing permanent structures. Coastal erosion management falls into soft and hard shoreline stabilization options with the United States tending to favor hard. However, post-Hurricane Sandy 2012, soft dune and beach replenishment have become more favorable in the U.S. with support being necessarily contingent upon an understanding of the pros, cons, and concepts surrounding each management strategy. Misconceptions could thus lead to a halt in progress and poor decisions with implications for community safety. We sought to gain a better understanding of current knowledge surrounding best practices in coastal management communities. Our assumption was that misconceptions in one coastal area, New Jersey, are likely echoed in other coastal areas in the U.S. and internationally. We employed a two-phase research design with an exploratory phase using semi-structured interview guidelines to collect data from a quota sample of 53 local residents and then tested the distribution of knowledge about coastal management facts by asking a convenience sample of 300 residents a structured set of 15 questions. Study participants identify differences in how beaches are managed and how protected they conversely consider an area to be. Dunes are generally preferred over hard engineering and replenishment. However, many key concepts regarding how dunes function naturally, with regards to the role of vegetation and fencing, are poorly understood suggesting a need for greater education surrounding these topics. Participants support continued tax investment in coastal areas to avoid retreat but recognize a tragedy of the commons in such actions for future generations. Learning who knows what, may contribute to more fruitful dialogues among stakeholders to pave the way for the adoption of suitable and sustainable management practices for better protected shorelines.

Above vs. belowground plant biomass along a barrier island: Implications for dune stabilization.

Coastal regions are inherently and increasingly vulnerable and geomorphologically unstable, yet are invaluable economic and residential hubs. Dunes are dynamic buffers to erosion and the most natural, economical, and effective defense for coastal communities. Vegetation is integral to dune structure as it facilitates accretion and stabilization. Differences in the vegetation and root density likely translate to variability in coastal erosion prevention, but this notion has been largely unconsidered. We directly compared stabilizing factors, depth and density, of the root systems of two dominant mid-Atlantic dune plant species, native American beach grass (Ammophila breviligulata) and invasive Asiatic sand sedge (Carex kobomugi). Despite high plant density, C. kobomugi is targeted for removal in restoration efforts as its roots are assumed to provide less effective stabilization than A. breviligulata. We collected 30 cores and hand dug 14 A. breviligulata ramets at Island Beach State Park, New Jersey to examine biomass, root:shoot ratios, and root density. C. kobomugi had a more extensive root system with a root:shoot ratio of 11.36:1 compared to 1.62:1 for A. breviligulata. Similarly, cores 60 cm deep and 7.6 cm wide were sufficient to attain fully intact A. breviligulata roots, which did not extend deeper than 40 cm, but insufficient for C. kobomugi roots which extended beyond the sampling system vertically and horizontally. Scaling these findings to m(-2), aboveground biomass is relatively equal, but C. kobomugi had over 700% more root mass m(-2) than A. breviligulata. These results have strong implications for dune management. The root system of C. kobomugi may be better adapted to stabilize dunes and thus protect coastal areas during small and large-scale perturbations than previously supposed. This is a unique situation whereby the creation of monocultures will hyperstabilize dunes and make them more resistant to erosion at the cost of reduced biodiversity within the framework of resiliency.