Longevity of rodenticide bait pellets in a tropical environment following a rat eradication program

Invasive rodents (primarily Rattus spp.) are responsible for loss of biodiversity in island ecosystems worldwide. Large-scale rodenticide applications are typically used to eradicate rats and restore ecological communities. In tropical ecosystems, environmental conditions rapidly degrade baits and competition for baits by non-target animals can result in eradication failure. Our objective was to evaluate persistence of rodenticide baits during a rat eradication program on Palmyra Atoll; a remote tropical atoll with intense competition for resources by land crabs. Following aerial application, bait condition was monitored in four terrestrial environments and in the canopy foliage of coconut palms. Ten circular PVC hoops were fixed in place in each of Palmyra’s four primary terrestrial habitats and five rodenticide pellets were placed in each hoop. Five coconut palms were selected in three distinct regions of the atoll. One rodenticide pellet was placed on each of five palm fronds in each coconut palm. Fresh baits were placed in all monitoring locations after each broadcast bait application. Bait condition and survival was monitored for 7 days after the first bait application and 6 days after second application. Bait survival curves differed between applications at most monitoring sites, suggesting a decrease in overall rat activity as a result of rodenticide treatment. One terrestrial site showed near 100 % bait survival after both applications, likely due to low localized rat and crab densities. Median days to pellet disappearance were one and two days for the first and second application, respectively. Differences in survival curves were not detected in canopy sites between bait applications. Median days to pellet disappearance in canopy sites were 2 and 4 days for the first and second application, respectively. Frequent rainfall likely contributed to rapid degradation of bait pellets in coconut palm fronds.     

Direct evidence of trophic interactions among apex predators in the Late Triassic of western North America

Hypotheses of feeding behaviors and community structure are testable with rare direct evidence of trophic interactions in the fossil record (e.g., bite marks). We present evidence of four predation, scavenging, and/or interspecific fighting events involving two large paracrocodylomorphs (=‘rauisuchians’) from the Upper Triassic Chinle Formation (～220–210 Ma). The larger femur preserves a rare history of interactions with multiple actors prior to and after death of this ～8–9-m individual. A large embedded tooth crown and punctures, all of which display reaction tissue formed through healing, record evidence of a failed attack on this individual. The second paracrocodylomorph femur exhibits four unhealed bite marks, indicating the animal either did not survive the attack or was scavenged soon after death. The combination of character states observed (e.g., morphology of the embedded tooth, ‘D’-shaped punctures, evidence of bicarination of the marking teeth, spacing of potentially serial marks) indicates that large phytosaurs were actors in both cases. Our analysis of these specimens demonstrates phytosaurs targeted large paracrocodylomorphs in these Late Triassic ecosystems. Previous distinctions between ‘aquatic’ and ‘terrestrial’ Late Triassic trophic structures were overly simplistic and built upon mistaken paleoecological assumptions; we show they were intimately connected at the highest trophic levels. Our data also support that size cannot be the sole factor in determining trophic status. Furthermore, these marks provide an opportunity to start exploring the seemingly unbalanced terrestrial ecosystems from the Late Triassic of North America, in which large carnivores far outnumber herbivores in terms of both abundance and diversity.     

Riparian vegetation and channel morphology impact on spatial patterns of water quality in agricultural watersheds

A model based on theKLS factors of the Universal Soil Loss Equation (USLE) accurately predicted temporal dynamics and relative peak levels of suspended solids, turbidity, and phosphorus in an agricultural watershed with well-protected streambanks and cultivation to the stream edge. Fine suspended solids derived from surface runoff appeared to be a major component of the suspended solids in this stream. The model did not predict the same parameters in a watershed with unstable channel substrates, exposed streambanks, and heterogeneity in riparian vegetation and channel morphology. The rate of increase in concentration of the water quality parameters was higher than predicted in areas without riparian vegetation and with unstable substrates. Peak levels were higher than predicted where unstable channel substrates occurred, and potential energy of the stream was high because of stream alterations (removal of near-stream vegetation and creation of a uniform, straight channel). Timing of the peak levels of suspended solids, turbidity, and phosphorus in these areas seemed related to major flushes of discharge due to delayed inputs from the surface or subsurface or both or to rapid urban drainage. Higher suspended solids concentration in this stream seemed to involve larger quantities of large particles. Thus, the USLE may not adequately predict relative water quality conditions within a watershed when variation in channel morphology and riparian vegetation exists. We make the following recommendations:

1. Models to predict water quality effects of management programs should combine a terrestrial phase (which details hydrologic and erosion processes associated with surface runoff) with an aquatic phase (which details hydrologic processes of scour and sediment transport in channels). The impact of near-channel areas on these hydrologic processes should receive special attention.
2. Sampling schemes should be designed to account for the impact on water quality of both watershed land surface and inand near-channel processes. In order to help distinguish sources of suspended solids, researchers should emphasize analysis of size distribution of particles transported.
3. Best management systems for improving the broadest range of water resources in agricultural watersheds need to be based on an expanded “critical area” approach, which includes identification of critical erosive and depositional areas in both terrestrial and aquatic environments.

     

A comparison of filtration rates among pelagic tunicates using kinematic measurements

Salps have higher filtration rates than most other holoplankton, and are capable of packaging and exporting primary production from surface waters. A method of kinematic analysis was employed to accurately measure salp feeding rates. The data were then used to explain how diverse body morphologies and swimming motions among species and lifecycle stages influence salp feeding performance. We selected five species, representing a range of morphologies and swimming styles, and used digitized outlines from video frames to measure body-shape change during a pulse cycle. Time-varying body volume was then calculated from the digitized salp outlines to estimate the amount of fluid passing through the filtering mesh. This non-invasive method produced higher feeding rates than other methods and revealed that body volume, pulse frequency and degree of contraction are important factors for determining volume filtered. Each species possessed a unique combination of these three characteristics that resulted in comparable filtration (range: 0.44–15.33 ml s⁻¹) and normalized filtration rates (range: 0.21–1.27 s⁻¹) across species. The convergence of different species with diverse morphologies on similar normalized filtration suggests a tendency towards a flow optimum.     

Flow structure and turbulence characteristics downstream of a spanwise suspended linear array

Laboratory experiments are conducted to quantify the mean flow structure and turbulence properties downstream of a spanwise suspended linear array in a uniform ambient water flow using Particle Tracking Velocimetry. Eighteen experimental scenarios, with four depth ratios (array depth to water column depth) of 0.35, 0.52, 0.78, and 0.95 and bulk Reynolds number (length scale is the array depth) from 11,600 to 68,170, are investigated. Three sub-layers form downstream of the array: (1) an internal wake zone, where the time-averaged velocity decreases with increasing distance downstream, (2) a shear layer which increases in vertical extent with increasing distance downstream of the array, and the rate of the increase is independent of the bulk Reynolds number or the depth ratio, and (3) an external wake layer with enhanced velocity under the array. The location of the shear layer is dependent on the depth ratio. The spatially averaged and normalized TKE of the wake has a short production region, followed by a decay region which is comparable to grid turbulence decay and is dependent on the depth ratio. The results suggest that the shear layer increases the transfer of horizontal momentum into the internal wake zone from the fluid outside of the array and that the turbulence in the internal wake zone can be modeled similarly to that of grid turbulence.     

Characterization and Biotechnological Functional Activities of Exopolysaccharides Produced by Lysinibacillus fusiformis KMNTT-10

Journal of Polymers and the Environment - In this study, the production and physicochemical characterization of exopolysaccharide (EPS) produced by Lysinibacillus fusiformis KMNTT-10 were...