Algae growth (grey patches) in Takuvaine stream near Empire Theatre in Avarua, photographed last Friday. (PHOTO: EMMANUEL SAMOGLOU). 20111813
Fertiliser use in crop and livestock farming, animal droppings, septic tank seepage, and soil run-off into streams from land clearing activities have been cited as potential causes of excessive algae growth.
Local officials are short on answers as to what is causing the excessive growth of algae in a number of streams around Rarotonga.
growth of the bright green algae has been noticed by staff of local
non-governmental organisation Te Ipukarea Society as well as government
officials. But questions remain as to what exactly is causing its growth and
Passfield, technical director of Te Ipukarea Society, described the outgrowth
at Takuvaine stream as a “filamentous green algae”.
lot of it appears suddenly like this, it is most likely a sign of high nutrients
(pollution) entering the water, possibly further upstream,” Passfield wrote in
an email to Cook Islands News.
nutrients could come from overflowing septic systems or run-off of agricultural
fertiliser, both of which would be much worse after heavy rains.”
said another possible source of nutrients that’s fuelling the algae growth
could be pigs that are kept too close to streams and waterways.
of the Ministry of Agriculture Temarama Anguna-Kamana has also seen many
affected waterways in Rarotonga.
are many streams around the island where there is excessive algal growth, and
such growth are clearly visible from the road,” Anguna-Kamana said.
believes the presence of the algae is indicative of high levels of nutrients in
cited agriculture crop and livestock farming, droppings from wild animals such
as chickens, seepage from septic tanks, and soil run-off into streams from land
clearing activities as potential causes.
not aware of any such intensive agriculture in close proximity to the Takuvaine
stream and near the Empire Theatre,” she said.
there is any increase in planting, it would be home gardening activities and
planting of small areas with root crops such as maniota, taro, and kumara.”
said Takuvaine valley is primarily known for wetland taro production, which
occurs mainly above the water intake.
farmers cultivating taro do not use fertiliser.
2004, the Ministry of Marine Resources has been monitoring the health of
Rarotonga’s waterways and lagoon.
the ministry issued a water quality report that showed stable levels of
bacteria at Avana stream and Paringaru stream in Muri, but a number of other
sites were at extremely poor levels.
testing results over the past decade have often showed excessive amounts of
nutrients and bacteria in many of the island’s streams.