Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin,Nevada1

Carroll, Rosemary W.H., Greg Pohll, David McGraw, Chris Garner, Anna Knust, Doug Boyle, Tim Minor, Scott Bassett, and Karl Pohlmann, 2010. Mason Valley Groundwater Model: Linking Surface Water and Groundwater in the Walker River Basin, Nevada. Journal of the American Water Resources Association (JAWRA) 46(3):554-573. DOI: 10.1111/j.1752-1688.2010.00434.x Abstract: An integrated surface water and groundwater model of Mason Valley, Nevada is constructed to replicate the movement of water throughout the different components of the demand side of water resources in the Walker River system. The Mason Valley groundwater surface water model (MVGSM) couples the river/drain network with agricultural demand areas and the groundwater system using MODFLOW, MODFLOW’s streamflow routing package, as well as a surface water linking algorithm developed for the project. The MVGSM is capable of simulating complex feedback mechanisms between the groundwater and surface water system that is not dependent on linearity among the related variables. The spatial scale captures important hydrologic components while the monthly stress periods allow for seasonal evaluation. A simulation spanning an 11-year record shows the methodology is robust under diverse climatic conditions. The basin-wide modeling approach predicts a river system generally gaining during the summer irrigation period but losing during winter months and extended periods of drought. River losses to the groundwater system approach 25% of the river’s annual budget. Reducing diversions to hydrologic response units will increase river flows exiting the model domain, but also has the potential to increase losses from the river to groundwater storage.     

Human–carnivore conflict: ecological and economical sustainability of predation on livestock by snow leopard and other carnivores in the Himalaya

Human communities in the Trans-Himalayan region depend on the dynamics of the agro-pastoral system for survival. Humans, livestock and wild predators share common resources in the region, and this leads to human–wildlife interactions that have the potential to threaten the continued viability of this fragile ecosystem and impact the local economy. This study explored the interaction between livestock and predators in the upper Mustang region of Nepal in terms of economic and ecological impacts. A total of 1,347 km² of pasture land were grazed by 30,217 livestock belonging to local people from six village development committees. It was found that the seasonal movement patterns of livestock, from higher to lower elevations (closer to villages), coincided with elevation movements of wild ungulate prey and snow leopards into this smaller land area. The number of livestock reported to have been killed by predators during the study period was 706, 75 % of which was attributed to snow leopards. An estimated US$ 44,213 was lost between October 2009 and June 2011 due to livestock predation. These losses of livestock to snow leopards and other carnivores provoked retaliatory killings by villagers, and this in turn may significantly affect the viability of predator populations in this region. We suggest four approaches to mitigate human–carnivore conflict in the region: (a) introduce a livestock insurance policy, (b) promote the use of predator-proof livestock corrals and sheds, (c) involve local people in alternative income generating activities, and (d) increase conservation education in these regions.     

Metal contamination increases the sensitivity of larvae but not gametes to ocean acidification in the polychaete Pomatoceros lamarckii (Quatrefages)

Ocean acidification is not happening in isolation but against a background of chronic low-level pollution for most coastal marine environments. The reproductive and larval stages of marine invertebrates can be highly sensitive to the impacts of both environmental pollutants and ocean acidification, but very little is currently known regarding the potential impacts of combined contaminant and high CO₂ exposures on the health of marine organisms. Ocean acidification research to date has focused heavily on the responses of calcifying marine invertebrate larvae and algae, and as such the polychaetes as a group, despite their ecological importance, remain understudied. Here, we investigate the effects of elevated seawater CO₂ (pH range 8.1–7.4, plus an extreme pH of 7.2 in the sperm motility experiments), in combination with the environmental pollutant copper (0.002 μM), on the early life history stages of the intertidal polychaete Pomatoceros lamarckii from two populations. P. lamarckii sperm appear to be robust to elevated seawater CO₂. Whilst all three of the sperm motility end points measured showed a response to elevated CO₂, these responses were small and not linear. The percentage of motile sperm and sperm curvilinear velocity were significantly reduced in the lower pH treatments of 7.4 and 7.2, whereas sperm straight-line velocity (VSL) was mostly unaffected except for an increased VSL at pH 8.0. Fertilisation success was investigated using two populations from the South West (UK), one from Torquay and one from Plymouth Sound. Fertilisation success was slightly but significantly reduced at the 7.6 and 7.4 pH treatments for both populations (a 9.0 % reduction in fertilisation success from pH 8.1 to 7.4 for Torquay), but with a greater effect observed in the population from Plymouth Sound (a 13.33 % reduction in fertilisation success). No additional impact of 0.002 μM copper exposure on fertilisation success was found. Larval survival was found to be much more sensitive to elevated CO₂ than sperm function or fertilisation, and a significant interaction with copper exposure was observed. These results demonstrate the potential for polychaete larvae to be affected by predicted ocean acidification conditions and that chronic coastal pollutants, such as copper, have the potential to alter larval susceptibility to ocean acidification conditions.     

A novel method for investigating the collective behaviour of fish: introducing ‘Robofish’

Collective animal behaviour has attracted much attention recently, but cause-and-effect within interaction sequences has often been difficult to establish. To tackle this problem, we constructed a robotic fish (‘Robofish’) with which three-spined sticklebacks (Gasterosteus aculeatus L.) interact. Robofish is a computer-controlled replica stickleback that can be programmed to move around a tank. First, we demonstrated the functioning of the method: that the sticklebacks interacted with Robofish. We examined two types of interaction: recruitment and leadership. We found that Robofish could recruit a single fish from a refuge and could initiate a turn in singletons and in groups of ten, i.e. act as a leader. We also showed that the influence of Robofish diminished after the first 30 min that fish spent in a new environment. Second, using this method, we investigated the effects of metric and topological inter-individual distance on the influence that Robofish had on the orientation of fish in a shoal of ten. We found that inter-individual interactions during this turn were predominantly mediated by topological, rather than metric, distance. Finally, we discussed the potential of this novel method and the importance of our findings for the study of collective animal behaviour.