Final answer:
The Poisson distribution can be used to model the concentration of the pathogenic bacteria in the pond.
Step-by-step explanation:
The probability distribution that can be used to model the concentration of the pathogenic bacteria in the pond is the Poisson distribution. The Poisson distribution is often used to model events that occur randomly over a fixed interval of time or space, such as the number of bacteria in a given volume of water. In this case, the average concentration of the bacteria is given as 10 organisms per liter, which can be used as the parameter for the Poisson distribution.