Chemical contamination and energy
What are the potential sources of chemical contamination from energy generation activities?
Increased levels of chemicals are very likely in geothermal-influenced lakes and rivers. Most geothermal waste fluids from power stations are injected back into the geothermal field to help replenish it and to avoid contaminating surface waters with dissolved chemicals. However, bioaccumulation (the accumulation of substances in an organism) of mercury, arsenic, and boron in the tissues of mahinga kai residing near geothermal areas can make them unsuitable for consumption.
Potential impacts of chemical contaminants on water quality and mahinga kai
- Local loss of fish species - fish may be harmed by contaminated water. Discharges and runoff into waterways can be lethal to aquatic life, causing fish kills from contaminants such as PAHs and pesticides.
- Local loss of invertebrate species - contaminants can be particularly lethal to invertebrates, e.g. crayfish. Invertebrates are also food for fish and persistent discharges that kill invertebrates could cause fish to travel farther in search of food, exposing them to greater risks and stress.
- Decrease in dissolved oxygen (DO) levels - waste compounds released into waterways initiate biochemical reactions that use up oxygen as the naturally present bacteria break down the organic matter (Biogeochemical Oxygen Demand, BOD). Excess nutrients can also lead to algal blooms and oxygen is used up when the algae die and decompose. Fish ‘breath’ oxygen through their gills; a decrease in available oxygen (anoxia) in the water column threatens their ability to respire, which may lead to death. Fish that tolerate low levels of dissolved oxygen (such as the introduced species gambusia) may replace native populations that are less tolerant.
- Increase turbidity and decrease in water clarity - water becomes cloudy and coloured green and brown, which reduces the ability of fish to see prey and detect predators.
- Damage to species - repeated exposure to sub-lethal doses of some contaminants can cause physiological and behavioural changes in fish that have long term effects on the population, such as reduced reproductive success, abandonment of nests and broods, a decreased immunity to disease, tumours and lesions, impairment of the central nervous system, and increased failure to avoid predators.