Gulf of Mexico hydrocarbon seep communities

Sediment and water samples were collected by submersible in September 1986 at 16 locations on the carbonate cap overlying a conical diapir, which was formed by the upward migration of oil and gas through a subsurface fault on the continental slope off Louisiana, USA (27°47N; 91°30.4W). The biological community at the site was photographed quantitatively with still and video cameras. Rigorous spatial sampling indices were maintained so that variation in chemical parameters and in the abundance of photographed organisms could be estimated within the bounds of the study site. Concentrations of extractable organic material (EOM) ranged from 0.24 to 119.26 in the sediment samples, while methane concentrations in the water samples were from 0.037 to 66.474 M. The visible biological community was predominantly composed of the chemosynthetic tube worms (Vestimentifera) Lamellibrachia sp. and Escarpia sp., and an undescribed, methane-oxidizing mussel (Mytilidae: Bathymodiolus-like), as well as diverse non-chemosynthetic organisms. The ranked abundance of tube worms was significantly correlated (p<0.05) with the concentration of EOM in the sediment samples, while the abundance of mussels was significantly correlated (p<0.05) with the concentration of methane in the water samples. Tube worms and mussels both occurred in dense clusters; however, the clusters of mussels had a more restricted distribution within the study site than did clusters of tube worms. Both organisms were most abundant in the vicinity of the subsurface fault.     

Simulation modeling to understand how selective foraging by beaver can drive the structure and function of a willow community

Beaver–willow (Castor-Salix) communities are a unique and vital component of healthy wetlands throughout the Holarctic region. Beaver selectively forage willow to provide fresh food, stored winter food, and construction material. The effects of this complex foraging behavior on the structure and function of willow communities is poorly understood. Simulation modeling may help ecologists understand these complex interactions. In this study, a modified version of the SAVANNA ecosystem model was developed to better understand how beaver foraging affects the structure and function of a willow community in a simulated riparian ecosystem in Rocky Mountain National Park, Colorado (RMNP). The model represents willow in terms of plant and stem dynamics and beaver foraging in terms of the quantity and quality of stems cut to meet the energetic and life history requirements of beaver. Given a site where all stems were equally available, the model suggested a simulated beaver family of 2 adults, 2 yearlings, and 2 kits required a minimum of 4 ha of willow (containing about10 stems m⁻²) to persist in a steady-state condition. Beaver created a willow community where the annual net primary productivity (ANPP) was 2 times higher and plant architecture was more diverse than the willow community without beaver. Beaver foraging created a plant architecture dominated by medium size willow plants, which likely explains how beaver can increase ANPP. Long-term simulations suggested that woody biomass stabilized at similar values even though availability differed greatly at initial condition. Simulations also suggested that willow ANPP increased across a range of beaver densities until beaver became food limited. Thus, selective foraging by beaver increased productivity, decreased biomass, and increased structural heterogeneity in a simulated willow community.     

Habitat-mediated variation in predation risk by the American marten

The probability of prey encounter, attack, capture, and kill are often hypothesized to depend on habitat structure, but field evidence in terrestrial systems is rare. We tested whether predation efficiency by the American marten (Martes americana) and fear of predation by their primary prey, the red-backed vole (Clethrionomys gapperi), differed between 20- to 50-year-old regenerating forest stands and older uncut stands. Our results showed that the frequency of prey encounter, prey attack, and prey kill were higher in old uncut forests, despite the fact that small-mammal density was similar to that in younger logged forests. These differences in predation efficiency were linked to higher abundance of coarse woody debris, which seems to offer sensory cues to martens, thereby increasing the odds of hunting success. Red-backed voles in regenerating forest stands exhibited increased wariness compared to voles living in old uncut forest, suggestive of a behavioral response to habitat-mediated variation in predation risk.     

Climate change risk management: a Mental Modeling application

The potential impacts of climate change are varied and highly uncertain, and pose a significant challenge to agencies charged with managing environmental risks. This paper presents a comprehensive and structured Mental Modeling approach to elicit, organize and present relevant information from experts and stakeholders about the factors influencing environmental risk management in the face of climate change. We present and review an initiative undertaken by the United States Army Corps of Engineers (USACE) to characterize climate change challenges to USACE environmental risk management activities, and to identify gaps with respect to science, engineering, and organizational processes for addressing these challenges. By employing Mental Modeling, the research has characterized the influences of climate change on USACE environmental risk management, and aggregating recommendations from 28 experts. In addition, the study identifies the most important opportunities to improve organizational response to climate change, ranging from focused research and development of technical capabilities to broad paradigm shifts and systemic organizational improvements within the USACE environmental risk management programs. This study demonstrates that Mental Modeling is a useful tool for understanding complex problems, identifying gaps, and formulating strategies, and can be used by a multitude of organizations and agencies.