Hill's pondweed (Potamogeton hillii) COSEWIC assessment and status report: chapter 8

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Limiting Factors and Threats

Potential threats to Hill’s pondweed would come from destruction of habitat such as draining of ponds and wetlands, or loss in water quality including chemical and thermal pollution. Since little is known about the biology of Hill’s pondweed, other limiting factors can only be speculated on. One site appeared to be degraded from cattle access. None of the other sites appeared to have any imminent threats.

Exotic plants may have had an impact on some populations. Curly pondweed (Potamogeton crispus), a widespread exotic species, was abundant at site 08 where Hill’s pondweed was not found and may have been instrumental, in part, in replacing it. Reed canary grass (Phalaris arundinacea), present in Ontario as both native and introduced variants, was dominant in the marshes at sites 02, 17 and 20 where it may have been introduced and modified the characteristics of the marshes.