“After the incredible discovery of the numerous fish nests, we believed about a technique on board to find out how large the breeding area was– there was actually no end in sight. We covered an area of 45,600 square meters and counted an extraordinary 16,160 fish nests on the picture and video footage,” states the AWI specialist.
Based on the images, the group was able to clearly recognize the round fish nests, about 15 centimeters deep and 75 centimeters in diameter, which were made unique from the otherwise muddy seabed by a round central location of small stones. Several types of fish nests were differentiated: “Active” nests, containing between 1,500 and 2,500 eggs and protected in three-quarters of the cases by an adult icefish of the types Neopagetopsis ionah, or nests which consisted of only eggs; there were also unused nests, in the vicinity of which either only a fish without eggs might be seen, or a dead fish. The scientists mapped the distribution and density of the nests utilizing OFOBSs lower-resolution but longer-range side scan finders, which taped over 100,000 nests.
Nests of icefish. Credit: AWI OFOBS Team
Researchers spot around 60 million nests of Antarctic icefish over a 240 square kilometers location in the Weddell Sea.
A towed video camera system photographed and filmed thousands of nests of icefish of the types Neopagetopsis ionah on the seabed. The density of the nests and the size of the whole breeding area recommend an overall number of about 60 million icefish reproducing at the time of observation.
The joy was excellent when, in February 2021, scientists viewed numerous fish nests on the displays aboard the German research vessel Polarstern, which their pulled camera system transmitted live to the vessel from the seabed, 535 to 420 meters listed below the ship, from the seafloor of the Antarctic Weddell Sea. The longer the objective lasted, the more the enjoyment grew, lastly ending in shock: nest followed nest, with later exact assessment revealing that there were on typical one breeding site per 3 square meters, with the group even finding a maximum of one to 2 active nests per square meter.
Eastern break-off edge of the iceberg. Credit: Alfred-Wegener-Institut/ Ralph Timmermann
Extrapolated to this area size, the overall number of fish nests was approximated to be about 60 million. Far, just individual Neopagetopsis ionah or little clusters of nests have actually been spotted here.
The distinct observations are made with a so-called OFOBS, the Ocean Floor Observation, and Bathymetry System. It is a cam sledge built to survey the seafloor of extreme environments, like ice-covered seas. It is towed on an unique fiber-optic and power cable normally at a speed of about one half to one knot, about one and half meters above the seafloor. “After the spectacular discovery of the numerous fish nests, we thought about a method on board to find out how large the breeding area was– there was literally no end in sight. The nests are 3 quarters of a meter in diameter– so they are much larger than the structures and creatures, some of which are only centimeters in size, that we usually find with the OFOBS system,” Autun Purser reports. “So, we had the ability to increase the height above ground to about three meters and the pulling speed to an optimum of three knots, therefore multiplying the area examined. We covered a location of 45,600 square meters and counted an extraordinary 16,160 fish nests on the picture and video footage,” says the AWI specialist.
Fish nests in Weddell Sea. Credit: PS124, AWI OFOBS group
Based on the images, the team had the ability to plainly identify the round fish nests, about 15 centimeters deep and 75 centimeters in size, which were made distinct from the otherwise muddy seabed by a round main area of little stones. A number of kinds of fish nests were differentiated: “Active” nests, containing in between 1,500 and 2,500 eggs and secured in three-quarters of the cases by an adult icefish of the species Neopagetopsis ionah, or nests which included only eggs; there were likewise unused nests, in the vicinity of which either just a fish without eggs could be seen, or a dead fish. The researchers mapped the distribution and density of the nests using OFOBSs longer-range but lower-resolution side scan sonars, which recorded over 100,000 nests.
The researchers integrated their outcomes with biological and oceanographic information. The result: the breeding location corresponds spatially with the inflow of warmer deep water from the Weddell Sea onto the greater shelf. With the help of transmitter geared up seals, the multidisciplinary team was likewise able to prove that the area is also a popular destination for Weddell seals. 90 percent of the seals diving activities took place within the region of active fish nests, where they presumably go in search of food. Not surprising that, the scientists compute the biomass of the ice fish colony there at 60 thousand tonnes.
Icefish Nest in Weddell Sea. Credit: PS124, AWI OFOBS group
With its biomass, this big breeding location is an extremely crucial ecosystem for the Weddell Sea and, according to present research study, likely to be the most spatially extensive contiguous fish reproducing nest discovered worldwide to date, the experts report in the publication in Current Biology.
German Federal Research Minister Bettina Stark-Watzinger stated: “My congratulations to the scientists included on their remarkable discovery. Once more reaffirmed its exceptional position, after the MOSAiC exploration, German marine and polar research has. German research vessels are drifting environmental lab. They continue to cruise the polar seas and our oceans practically non-stop, serving as platforms for science focused on generating important findings to support climate and environmental management. Funding by the Federal Ministry of Education and Research (BMBF) offers German marine and polar research study with one of the most cutting edge research study vessel fleets worldwide. This discovery can make a crucial contribution towards protecting the Antarctic environment. The BMBF will continue to work towards this goal under the umbrella of the United Nations Decade of Ocean Science for Sustainable Development that runs till 2030.”
For AWI Director and deep-sea biologist Prof. Antje Boetius, the existing research study is a sign of how urgent it is to establish marine safeguarded locations in Antarctica. Considering how little known the Antarctic Weddell Sea is, this highlights all the more the requirement of global efforts to establish a Marine Protected Area (MPA),” Antje Boetius categorizes the results of the research study, in which she was not directly involved.
Antje Boetius includes: “Unfortunately, the Weddell Sea MPA has still not yet been adopted unanimously by CCAMLR. Now that the place of this remarkable breeding colony is known, Germany and other CCAMLR members should guarantee that no fishing and only non-invasive research study takes location there in future. So far, the remoteness and difficult sea ice conditions of this southernmost location of the Weddell Sea have actually protected the location, however with the increasing pressures on the ocean and polar areas, we ought to be far more enthusiastic with marine conservation.”
Reference: “A vast icefish reproducing nest discovered in the Antarctic” by Autun Purser, Laura Hehemann, Lilian Boehringer, Sandra Tippenhauer, Mia Wege, Horst Bornemann, Santiago E.A. Pineda-Metz, Clara M. Flintrop, Florian Koch, Hartmut H. Hellmer, Patricia Burkhardt-Holm, Markus Janout, Ellen Werner, Barbara Glemser, Jenna Balaguer, Andreas Rogge, Moritz Holtappels and Frank Wenzhoefer, 13 January 2022, Current Biology.DOI: 10.1016/ j.cub.2021.12.022.
