The findings represent a careful quantitative analysis of what's been called a "jellyfish explosion" after intense fishing in the area in the last few decades. The findings are reported by Andrew Brierley, of the University of St. Andrews, and his colleagues in the July 12th issue of the journal Current Biology.
An increasing abundance of jellyfish off Namibia had been noted for some time, but an analysis of this trend's effect on the ecosystem has been hampered by a lack of hard data on jellyfish abundance. The authors note that prior to their work, less formal observations had pointed to a striking change over time--for example, jellyfish are now so numerous in the region that they significantly interfere with fishing operations and industrial water-uptake systems. In addition, large jellyfish species such as Chrysaora hysoscella and Aequorea forskalea have become more commonly reported.
In their new work, the researchers sampled waters all along the Namibian shelf, between the borders of Angola and South Africa, in an area known as the northern Benguela. In the past, this region has offered abundant fish stocks, thanks largely to its being served by cool, nutrient-rich upwellings occuring along the continental shelf. The fish stocks, including sardines and anchovies, have been heavily exploited since the 1970s and have been strongly depleted in the process. Because fish and jellyfish essentially compete for similar nutrient resources, a dramatic decline in fish populations could theoretically contribute to a substantial shift in the abundance of jellyfish.
The researchers' findings indicate that jellyfish now account for significantly more biomass in the northern Benguela waters than do fish. Based on the data they obtained--by using scientific echosounders and trawl nets to sample jellyfish and fish in an area of over 30,000 nautical miles--the researchers estimate the total biomass of jellyfish in the region to be 12.2 million metric tons (mostly contributed by the large A. forskalea species), whereas the biomass of fish accounts for only 3.6 million metric tons.
In their report, the authors point out that jellyfish biomass has risen in numerous locations worldwide, possibly as a consequence of fishing. Climactic changes could also contribute to jellyfish population shifts.
The authors also note that jellyfish have few predators and that jellyfish abundance has significant potential consequences for oceanic ecosystems--such consequences include slowed or attenuated fish-stock recovery and alterations in the nature of carbon cycling.
Heidi Hardman | EurekAlert!
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.
Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...
Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.
Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...
University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.
Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.
Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.
Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
25.04.2018 | Physics and Astronomy
25.04.2018 | Physics and Astronomy
25.04.2018 | Information Technology