Vast mounds of sponges stretching for tons of of metres have been found 600 metres down close to the Channel Islands off California
3 March 2022
Vast mounds product of the skeletons of glass sponges have been found 600 metres down on the seabed of the Channel Islands National Marine Sanctuary off California. The mounds are not like something discovered earlier than within the space and may very well be examples of a really uncommon sort of habitat often called a sponge reef.
The reef-like mounds had been first noticed by researchers in 2020, throughout a dive by a remotely operated car (ROV) from the analysis ship EV Nautilus.
“We started seeing patches of dead sponges,” mentioned Abigail Powell, a contractor for the US National Oceanic and Atmospheric Administration, throughout a digital discuss at the Ocean Sciences Meeting 2022. “It just got denser and denser, and soon we were climbing over great mounds of it.”
The space is comparatively properly explored, so the invention was a shock. “There have been many dives here over the years, but never over this particular track,” mentioned Powell.
The mounds consist primarily of the silica skeletons of lifeless glass sponges, turned brownish by a coating of sediment. However, there are lots of different species dwelling on and within the mounds, together with fish, clams and sponges of each the reef-building and non-reef-building sorts.
In 2021, the ship returned to the sponge mound web site and an ROV zigzagged over two of the mounds. This revealed that the biggest mound was greater than a kilometre lengthy, 500 metres large and no less than a number of metres thick in some locations.
“The continuous extent of the patches over hundreds of metres is unlike anything we have encountered before,” Powell mentioned.
Sponge reefs had been frequent in the course of the time of the dinosaurs, however had been thought to have vanished fully from trendy oceans. Then within the Eighties, dwelling sponge reefs had been discovered off the coast of British Columbia in Canada, and a number of others have been discovered elsewhere.
“Glass sponge reefs are spectacular, but fragile, ecosystems,” mentioned Powell.
However, she is hesitant about calling the mounds off California sponge reefs till acoustic scans reveal their deeper construction.
“We need to find out whether the mounds are composed of sponge skeletons or whether we are looking at a relatively thin layer of sponge growing on rocky ridges,” Powell informed New Scientist.
“I think ‘reef-like’ would be a good way to describe what we found until we know more.”
What is obvious is that the proportion of dwelling reef-building sponges on the floor of the mounds is far decrease than on the reefs off Canada.
It isn’t identified whether or not it is a pure phenomenon defined by native environmental variations between the 2 websites, or whether or not one thing has killed numerous the reef-building sponges within the Channel Islands National Marine Sanctuary.
“There are still many unanswered questions,” mentioned Powell.
While trawling is allowed in components of the sanctuary, the sponge mounds are in a no-take zone and so needs to be protected against all varieties of fishing.
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