Water Pollution

The pristine requirement in the Singapore freshwater crab’s habitat of near-neutral pH value means that it is vulnerable to the introduction of pollutants. The presence of pollutants potentially results in habitat loss, population decline and the eventual wiping out of its population. There are many causes of water pollution. In Singapore, potential pollutants include construction runoff, trash and chemicals.

Construction projects in the vicinity can increase the possibility of toxic pollutants being released into the water. Poor trash disposal by park visitors, especially to unprotected areas, will also negatively affect the water quality.

Dengue concern of still water may lead to the use of widespread fogging at nearby residential areas. While this aims to prevent mosquito breeding, the chemicals released into streams can pollute and deteriorate the water quality suitable for the Singapore freshwater crab.

Stream acidification can also lead to water pollution. A study in Singapore speculated stream acidification as a leading cause of the disappearance of the Singapore freshwater crabs at a protected area in the Bukit Timah Nature Reserve. While the exact cause of the stream acidification continues to be investigated, research proposed possible acid precipitation to be chiefly influenced by human activities.

Stream acidification may occur due to acid precipitation entering the streams, creating an increase in the acidity level of the water. As these freshwater hill streams are originally neutral in acidity, the deposition of acid rain does not allow the streams to be neutralised but acidified. This results in an unsuitable environment for the Singapore freshwater crab. Stream acidification of the tropical freshwater system does not only affect the biodiversity of the freshwater crabs, but also results in ecological imbalance of the aquatic ecosystem. For instance, while the diversity of some species declines to disappearance, others may increase uncontrollably if not carefully managed.

The survival of freshwater crabs essentially relies on a habitat with good freshwater quality. Therefore, water pollution which reduces freshwater quality, is a potential threat to the habitat degradation for Singapore freshwater crabs.