OPINION: Editorial: A slow, insidious process is suffocating the life out of our estuaries and if we can't or won't find a way to stop it the future is grim for our coastal marine life. That was the message from Environment Southland last week and we need to take it very seriously.
Sludge - nutrient-enriched silt - is clogging up the estuaries, coating everything under the water and ever-more-rapidly strangling the habitat of much of our inshore marine life, from shellfish beds to the sheltered feeding grounds of juvenile fish such as flounder, red cod and trout.
It is also affecting the feeding habits of bird life like godwits and stilts that rely on marine worms to sustain them. Marine worms also can't survive in an oxygen-starved ecosystem under the thickening carpet of sludge.
Environment Southland coastal scientist Nick Ward says the worst affected areas in the south are the Waihopai arm of the New River estuary, the Jacobs River estuary, Waiau Lagoon, Bushy Point and Daffodil Bay, and that unless something is done some fisheries could collapse.
Although Mr Ward did not mention it, Bluff Harbour can be added to the list. Run-off sediment has been coating the harbour bed for years, as several fishing companies have found to their cost. Mussel farming in the sheltered waters of the harbour seemed at first glance to be ideal, but after years of trying almost all have been abandoned. The mussels grew, but never to a size viable for a commercial venture.
The companies, Sanford among them, eventually concluded that the silt washing down the harbour after every fresh was not only clogging up the mussel farms but also killing off the microscopic marine life that sustains mussels - there simply was not enough food.
The silt is coming from a wide range of sources and is not a new phenomenon, it has been building up for decades. And it is not caused exclusively by run-off from farmland, even though increasingly intensive cultivation and cropping is adding to the problem.
Townies too are adding their share as more land is sub-divided.
Even shellfish that continue to cling to survival are becoming dangerous to eat. The pipi beds in the New River estuary - those beds have suffered a "fairly big decline" according to Mr Ward - are probably not safe to eat because of the toxicity of the water and mud.
Maori resource management of Te Ao Marama Dean Whaanga says there are concerns the pipis may not be edible because of pollution from run-off, and that people should also be wary of taking other food such as cockles and flounder for the same reason.
Two important reports on the extent of silt and nutrient pollution in the estuaries are expected to be made public in the next few months and they need to be carefully studied.
A report on the New River and Jacobs River estuaries, prepared by coastal specialists Wriggle Coastal Management, is to be released next month and an even more significant analysis of the widespread sediment problem, a joint effort from Environment Southland, the National Institute of Water and Atmospheric Research, and GNS Science, New Zealand's leading geoscience research institute, is expected to be released in the next few months.
When two of this country's leading scientific agencies see the need to focus on causes for the decline of our inshore fisheries we need to sit up and take notice. And then implement a plan to try to fix what is clearly a critical problem.
- © Fairfax NZ News
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