The unique waters of New Zealand’s fjords


South Island’s fiordland draws not only tourists in their droves but scientists from around the world. This is due to the fact that the landscape is not only majestic for holidaymakers, but offers a unique opportunity to those investigating watery worlds both above and below the surface.


Millions of years in the making


For 500 million years the land making up fiordland has been constantly, gradually sculpted and redefined by the forces of nature.


Approximately 20,000 years ago, during the Pleistocene glaciation period, glaciers of great magnitude carved trenches in towering mountains and wound their way to the Tasman Sea. The glaciers carved the 14 major basins and associated arms, creating what we know today as the fjords. Then about 18,000 years ago, the glaciers slowly melted away leaving free space and an array of rocks and debris at the entrance where land meets sea.


About 6,500 years ago the sea level rose above the barriers, which continue to restrict the flow of seawater in and out of the fjords. As a result, water circulation is confined to the top 20-40 metres and deeper waters are said to have been undisturbed for years. Flanking these ancient waters, sandstone and limestone infused with igneous rocks including granite and diorite can be found, and are said to be hundreds of millions of years old.


According to Maori legend, the unique landscape was created by giant stonemason Tute Rakiwhanoa, who took his adzes and carved away rock and stone to create safe waterways and harbours bountiful with fish and birds. In 1990, the area was listed as a United Nations World Heritage site and given the name Te Wahipounamu, also known as 'the place of greenstone', referencing the abundant and sought after mineral resource found here.

Seeing beyond the surface


In the fjordlands rainfall is especially high, with 6-8 metres of rain falling here every year. This rain creates an array of waterfalls and draws tannins from the rainforests down to the water’s surface. The freshwater, mineral dense and brown in colour, sits atop the more dense saltwater. As a result, much of the sun’s rays does not filter through to the saltwater and a wide variety of coral and sea creatures commonly found at great depths can be met as low as 10 metres from the surface. Scientists call this phenomenon ‘deep water emergence’.


In the greenlit water, limited seaweed grows on the walls of the fjords, but encrusting and sessile animals such as sponges and corals are plentiful. Black corals, sea pens and lampshells are also abundant here. In addition to what has been described as ‘highly endemic and diverse invertebrate fauna’, a number of deep water animals are brought in from the Tasman Sea to the more sheltered waters of the fjords. You will also find seals, the southernmost wild population of bottlenose dolphins, whales including humpback and southern right whales, and penguins.


Over the years many discoveries have been made, proving to advance understanding and discoveries about underwater animals and ecosystems. As recent as 2013, scientists discovered previously unknown fauna, in this instance two new specimens of sea pens.


Another study published in the same year in the New Zealand Journal of Marine and Freshwater Research highlights key findings around processes that define ecosystem structure and function. For instance, the report describes how in fjordic systems stability and systems are shaped by bottom up and top down mechanisms, and there is great cycling and flux of organic matter and nutrients through all food webs.


For example, microbial recycling of organic matter from the likes of phytoplankton, kelp and surrounding terrestrial forests can provide the majority of needs to communities at the lowest levels of water, also known as the benthic zone.


It is uncertain how changing climates and heavy tourism is impacting the fiords and their inhabitants, but researchers continue to study the unique area just as surely as explorers and curious souls are drawn to these waters and trenches.


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