Leeches as Sensor-bioindicators of River Contamination by PCBs

The aim of the study was to evaluate the use of leeches of the genus Erpobdella as a means of assessing polychlorinated biphenyl contamination of watercourses. The River Skalice, heavily contaminated with PCBs, was selected as a model. The source of contamination was a road gravel processing factory in Rožmitál pod Třemšínem from which an estimated 1 metric ton of PCBs leaked in 1986. Levels of PCB were measured in leeches collected between 1992 to 2003 from 11 sites covering about 50 km of the river (the first sampling site upstream to the source of contamination and 10 sites downstream). The PCB indicator congeners IUPA no. 28, 52, 101, 118, 138, 153, and 180 were measured. Levels were highest at the four sampling sites nearest the source of pollution. The highest values of PCB congeners were found in 1992. PCB content decreased from 1992 to 2003 and with distance from the source. The study indicated that leeches of the genus Erpobdella are a suitable bioindicator of contamination in the surface layer of river sediments

Watching grass grow: long-term visual navigation and mission planning for autonomous biodiversity monitoring

We describe a challenging robotics deployment in a complex ecosystem to monitor a rich plant community. The study site is dominated by dynamic grassland vegetation and is thus visually ambiguous and liable to drastic appearance change over the course of a day and especially through the growing season. This dynamism and complexity in appearance seriously impact the stability of the robotics platform, as localisation is a foundational part of that control loop, and so routes must be carefully taught and retaught until autonomy is robust and repeatable. Our system is demonstrated over a 6-week period monitoring the response of grass species to experimental climate-change manipulations. We also discuss the applicability of our pipeline to monitor biodiversity in other complex natural settings

An evaluation of leeches as in situ biomonitors of chlorinated phenolic compounds discharged from bleached kraft pulp mills

Leeches were evaluated as biomonitors of chlorinated phenolic compounds discharged from bleached kraft pulp mills using integrated laboratory and field investigations. Semi-static laboratory bioassays of one week duration were carried out in order to determine how environmental factors such as contaminant concentration, water pH, water temperature and suspended sediments as well as biotic factors such as leech weight and species affect bioconcentration. In order to evaluate leeches under varying in situ conditions, three field monitoring trials during summer (July), fall (October) and winter (February) were conducted on the Fraser River, downstream of three bleached kraft pulp mills at Prince George B.C. There was a strong linear correlation (r² = 0.89 - 0.96) between water contaminant concentration (0.1 - 10 µg/L) and bioconcentration of chlorinated guaiacols, with slow depuration rates (t₁₋₂ > 28 days). Bioconcentration of chlorinated guaiacols was inversely related to pH (5.1 - 9.0), but was only weakly correlated with the concentration of the undissociated compound, indicating that the ionized compound also contributed to the bioavailable fraction. Bioconcentration increased between 4.4 and 11.8° C, but did not show a significant change from 11.8 to 20.0° C, indicating a bi-phasic model for the temperature - bioconcentration relationship. No clear relationship between suspended sediment concentration (0 0.15 g/L) and bioconcentration was observed, although the presence of 5% organic material in suspended sediments reduced bioavailability of the chlorinated phenolics. Water stirring in the suspended sediment bioassays increased bioconcentration relative to quiescent semi-static conditions. There was strong inverse relationship (r² = 0.90 - 0.94) between leech weight and bioconcentration with no clear trend between two different species of leech (Nephelopsis obscura and Percymoorensis marmorata). Field monitoring revealed chlorinated phenolics in pulp mill effluent (0.6 -17 μg/L) and water (0.002 - 0.073 μg/L) and suspended sediments (0.36 - 176 μg/kg) during the study periods. Leeches were effective biomonitors of tri- and tetrachlorinated guaiacols under diverse seasonal conditions, with bioconcentration factors ranging from 465 - 6000 and were accurate indicators of the relative proportions of these chlorinated contaminants in both pulp mill effluent and the Fraser River, 40 km downstream of pulp mill outfalls.Science, Faculty ofResources, Environment and Sustainability (IRES), Institute forGraduat

Characterization and Modeling of Rotational Responses for an Oscillating Foil Underwater Robot

Abstract- In order to better understand the behavior of the underwater robot developed at our laboratory, a simple but relatively good model of the underwater behavior of the robot had to be developed. In order to be useful for model-based control techniques onboard the robot, the model had to have low computing requirements, yet be complex enough to capture the transient response of the robot. To achieve this, a system identification approach was taken by first capturing the robot response to various inputs, and then matching them to a simple model

A Visual Servoing System for an Aquatic Swimming Robot

This paper describes a visual servoing system for an underwater legged robotic system named AQUA and initial experiments with the system performed in the open sea. A large class of significant applications can be leveraged by allowing such a robot to follow a diver or some other moving target. The robot uses a suite of sensing technologies, primarily based on computer vision, to allow it to navigate in shallow-water environments. The visual servoing system described here allows the robot to track and follow a given target underwater. The servo package is made up of two distinct parts: a tracker and a feedback controller. The system has been evaluated in the sea water and under natural lighting conditions. The servo system has been tested underwater, and with minor modifications the system can be used while the robot is walking on the ground as well

Towards a dynamic actuator model for a hexapod robot

We describe a model predicting the output torque of the battery-amplifier-actuator-gear combination used on the hexapod robot RHex, based on requested PWM (Pulse-Width-Modulation) duty cycle to the amplifier, battery voltage, and motor speed. The model is broken into independent components, each experimentally validated: power source (battery), motor amplifier, motor, and (planetary) gear. The resulting aggregate model shows <6 % Full Scale RMS error in predicting output torque in the first quadrant of operation (positive torques). Understanding the key ingredients and the attainable accuracies of torque production models in our commonly used battery-amplifier-actuator-gear combinations is critical for mobile robots, in order to minimize sensing, and thus space, size, weight, power consumption, failure rate, and cost of mobile robots

Unsupervised Learning of Terrain Appearance for Automated Coral Reef Exploration.

We describe a navigation and coverage system based on unsupervised learning driven by visual input. Our objective is to allow a robot to remain continuously moving above a terrain of interest using visual feedback to avoid leaving this region. As a particular application domain, we are interested in doing this in open water, but the approach makes few domain-specific assumptions. Specifically, our system employed an unsupervised learning technique to train a k-Nearest Neighbor classifier to distinguish between images of different terrain types through image segmentation. A simple random exploration strategy was used with this classifier to allow the robot to collect data while remaining confined above a coral reef, without the need to maintain pose estimates. We tested the technique in simulation, and a live deployment was conducted in open water. During the latter, the robot successfully navigated autonomously above a coral reef during a 20 minutes period. 1