The quake left masses of seaweed and other marine life exposed to the sun and starved of water. Photo / File
The quake left masses of seaweed and other marine life exposed to the sun and starved of water. Photo / File
It was one of the most dramatic images of the monster Kaikōura Earthquake.
Thousands of paua, and thick beds of seaweed, dying in the sun after a 110km-long stretch of coastline was suddenly and violently hauled out of the ocean.
Now new research has shown there's been little recovery in the Kaikōura coast's devastated seaweed communities, which once formed crucial habitats for a multitude of tiny species.
University of Canterbury marine ecologists have been able to carry out a detailed comparison between these habitats today, and how they were over the decades leading up to the monster 7.8 quake that struck at midnight on November 14, 2016.
Dr Mads Thomsen said the region may have been studied in more detail, ecologically, than any other coastline in the country.
"It therefore came as a shock when this ecologically, culturally and educationally important coastline was virtually destroyed overnight."
Christchurch teenager Peter Anderson joined a mass effort in the days after the 2016 Kaikoura Earthquake to save sealife stranded by the raised coastline. Photo / File
Its large beds of habitat-forming seaweed provided living space and food for fast-growing and highly diverse communities of tiny animals barely visible to the naked eye.
These small animals, although difficult to see, served as a vital link in the ecological food chain between seaweeds and large predators like fish and crabs.
"In addition, the seaweeds also maintain the reef itself – without the touch basal seaweeds on the reefs, there has been accelerated erosion," Thomsen said.
"Furthermore, we know that large mega-disturbances – like seismic uplifts - have occurred throughout the world's tectonic plate-zones in the past, like in Chile, and will continue to do so in the future.
"Nevertheless, only a handful of studies have had valuable 'before earthquake' data to analyse uplift impacts with hard scientific methods.
"We now have that unique opportunity because this region remains one of our intensive study areas. In other words, we can use this disaster to learn how mega-disturbances affect marine ecosystems and how recovery processes play out."
In the new study, Thomsen, renowned Canterbury marine ecologist Distinguished Professor David Schiel, and fellow researchers Alfonso Siciliano, Isis Metcalfe, Paul South, Tommaso Alestra, and Shawn Gerrity, took hundreds of geo-tagged digital photos to compare with previous surveys.
Sally Paul from Okains Bay was one of a large volunteer group saving paua left high and dry after the quake. Photo / File
"We also collected hundreds of seaweed samples from which we extracted, counted and identified all the microscopic animals that live on them."
Incredibly, that involved cataloguing a total 163,002 tiny animals living on 466 collected seaweed fronds that had a total dried weight of 2.7kg.
"We could now compare these 'before-earthquake' data to new 'after-earthquake data' collected with the same methods and in the same areas."
'Dramatic losses'
Their results found the ecological infrastructure needed to support thriving intertidal seaweed communities had been greatly damaged by the coastal uplift.
Some areas had been permanently hoisted out of the water, by as much as 6m above their former tidal height.
"Others are experiencing very high temperatures because they are not sufficiently inundated by water at high tide," Thomsen said.
Kaikoura's quake-raised reefs - which once supported an abundance of sealife - as they appear today. Photo / Mads Thomsen
"Seaweeds that live in the intertidal zone - and that cannot move - are now out of the water for much longer time during each low tide event, exceeding their tolerance levels for drying out and recovering."
That had driven mass mortality of those large "host" seaweeds that once dominated the uplifted intertidal flat reef platforms.
"We also documented dramatic losses of small but abundant seaweed and animals that live on or around the larger host-seaweed - possibly with flow-on effects for the myriad of larger species that depend on these species for habitat or food."
In future, the researchers expected the coastline would support much smaller populations of intertidal seaweeds.
"Furthermore, because most of the original populations have died, much fewer seaweed recruits are being produced and natural recolonisation is slow because of the scarcity of reproductive adults."
Red epiphytic seaweed attached to large brown seaweed together provide living space to an enormous amount of tiny animals barely visible to the naked eye. Photo / Mads Thomsen
Thomsen noted that, internationally, only a few studies had ever documented impacts on marine organisms after seismic uplifts.
"Our results are globally important because they show not only wholesale damage to dominant seaweed but also to small invertebrates and species that serve crucial societal and ecological functions," he said.
"The results also highlight the importance of, whenever possible, to monitor recolonisation of seaweed, and if recolonisation is very slow, perhaps giving nature a helping hand through active restoration programmes."
Quake's enduring impact
• About 20 per cent of the adult blackfoot paua on the coastline was destroyed and only a small handful of offspring were found.
• Deep sea life in the Kaikoura Canyon were smothered by a quake-triggered landslide, but these ecosystems have begun to recover.
• Another study published last month found the quake affected sperm whales' ability to find food for at least a year.
