It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Wednesday, February 14, 2024
OCEANOGRAPHY
Tiny crustaceans discovered preying on live jellyfish during harsh Arctic night
First observation of marine invertebrates eating live and dead jellyfish during Arctic winter
In the dark and cold of the months-long polar night, food resources are limited. Some groups of marine organisms in the polar regions overcome this challenge by going into a metabolic resting state in winter, surviving on reserves accumulated during the short growth season. But others, such as several species of marine zooplankton, have evolved a different strategy: they shift from a specialized to an omnivorous diet during the polar night, profiting from a wide range of potentially less rewarding foods that are available throughout the year.
Now, scientists have shown that one key source of food for such seasonal Arctic omnivores has been overlooked until now: dead and living jellyfish. The results are published in Frontiers in Marine Science.
“Here we show for the first time that jellyfish – thought to be typically poor in nutrients – are nevertheless an important food source for amphipods during the Arctic polar night,” said Annkathrin Dischereit, a doctoral student at the Alfred Wegener Institute in Germany, and the article’s first author.
“For example, we found evidence that some amphipods feast on ‘jelly-falls’, naturally sunken jellyfish carcasses. Other species may also prey on living jellyfish.”
In January and February 2022, Dischereit and others from the Helmholtz Young Investigator Group ARJEL at the Alfred Wegener Institute took part in an expedition to the German-French AWIPEV research station on Svalbard.
Venturing out in a small boat from Kongsfjorden, Svalbard, the researchers found its waters to be teeming with jellyfish: not just ‘true jellyfish’ like the lion's mane jellyfish, but also hydrozoans like the thimble-shaped pink helmet jellyfish, colonial siphonophores, and unrelated comb jellies or ctenophores.
The researchers sampled the local amphipods – crustaceans between five and 20 millimeters long – with nets and baited traps. They had chosen to focus on amphipods because they are locally abundant and important components of the fjord systems. The catch mainly consisted of four species: Orchomenella minuta and Anonyx sarsi, scavenging amphipods in the superfamily Lysianassoidea, and two distantly related Gammarus species.
DNA metabarcoding of ingested prey
The researchers dissected the guts out of each amphipod, and then used DNA metabarcoding to identify the remains of prey within.
Jellyfish DNA from multiple species predominated in the guts of both Gammarus species, together with traces from algae and crustaceans. Jellyfish DNA was likewise found, but less abundant, in A. sarsi and O. minuta, proving that all four species studied routinely consume jellyfish tissue. The authors conclude that A. sarsi and O. minuta seem to opportunistically feed on jelly-falls, while both Gammarus may in addition prey on live comb jellies.
Fish – living or dead – were likewise important food for both A. sarsi and O. minuta, together with polychaete worms, crustaceans, and mollusks.
Dischereit et al. also found that between 27% and 60% of the sampled amphipods had empty guts. This confirms that food scarcity and starvation are a challenge to marine invertebrates during the polar night, even for species that can shift to a more omnivorous diet.
Paradigm shift on jellyfish
“There has been a recent paradigm shift in the marine biology literature that recognizes that far from being a ‘trophic dead-end’, jellyfish are in fact eaten by a wide range of organisms. Our observations corroborate this major change in how scientists view the role of jellyfish in the food web,” said Dr Charlotte Havermans, the leader of the 2022 expedition and the study’s last author.
“Because jellyfish tissue is quickly digested, they may have been overlooked as a prey item in previous studies, which unlike our study relied on visual identification of food items to determine the diet of Arctic invertebrates.”
‘Atlantification’ and the new Arctic
Today, the Arctic is warming at a record rate compared to the rest of the world, and jellyfish species from the Atlantic Ocean have been observed to spread northward. This ‘Atlantification’ may make jellyfish even more important as a resource within Arctic food webs.
“To get a better idea of the role of jellyfish in the Arctic marine food web, and how this may change when their populations increase in the ‘new Arctic’, we plan to further investigate the diet of other invertebrates and fish that potentially feed on jellyfish. Questions remain, for example, whether jellyfish are a regular part of the diet of amphipods or whether they are simply a survival food during the polar night”, concluded Dischereit.
Pink helmet jellyfish, a hydrozoan
Ctenophore or comb jelly
CREDIT
C. Havermans
The French-German AWIPEV research station on Svalbard, where the research was done
Sampling marine organisms with handnets on Svalbard
CREDIT
E Horvath (AWI)
The scientists at the AWIPEV research station on Svalbard
University of Queensland-led research has shown there is more coral reef area across the globe than previously thought, with detailed satellite mapping helping to conserve these vital ecosystems.
“This revises up our previous estimate of shallow reefs in the world’s oceans,” Dr Lyons said.
“Importantly, the high-resolution, up-to-date mapping satellite technology also allows us to see what these habitats are made from.
“We’ve found 80,000 square kilometres of reef have a hard bottom, where coral tends to grow, as opposed to soft bottom like sand, rubble or seagrass.
“This data will allow scientists, conservationists, and policymakers to better understand and manage reef systems.”
More than 1.5 million samples and 100 trillion pixels from the Sentinel-2 and Planet Dove CubeSat satellites were used to capture fine scale detail on a high-resolution global map.
“This is the first accurate depiction of the distribution and composition of the world’s coral reefs, with clear and consistent terminology,” Dr Lyons said.
“It’s more than just a map – it’s a tool for positive change for reefs and coastal and marine environments at large.”
UQ’s Associate Professor Chris Roelfsema said the reef mapping project, a collaboration with more than 480 contributors, is already being used in coral reef conservation around the world.
“The maps and associated data are publicly accessible through the Allen Coral Atlas and Google Earth Engine, reaching a global audience,” Dr Roelfsema said.
“They’re being used to inform projects in Australia, Indonesia, the Timor and Arafura Seas, Fiji, Solomon Islands, Tonga, Vanuatu, Panama, Belize, Bangladesh, India, Maldives, Sri Lanka, Kenya and western Micronesia.
“The details provided by these maps empowers scientists, policymakers and local communities to make informed decisions for the preservation of our coral reefs.”
The Allen Coral Atlas was conceived and funded by the late Paul Allen’s Vulcan Inc. and managed by Arizona State University along with partners from Planet, the Coral Reef Alliance and The University of Queensland.
The research paper is published in Cell Reports Sustainability.
On healthy reefs around the world, corals, algae, fishes and microbes live interconnected and in balance—exchanging nutrients, resources, and chemical signals. New research led by the University of Hawai‘i (UH) at Mānoa and and the Royal Netherlands Institute for Sea Research (NIOZ) revealed that when coral bleaching occurs, corals release unique organic compounds into the surrounding water that not only promote bacterial growth overall, but select for opportunistic bacteria that may further stress reefs.
“Our results demonstrate how the impacts of both short-term thermal stress and long-term bleaching may extend beyond coral and into the water column,” said Wesley Sparagon, co-lead author, postdoctoral researcher in the UH Mānoa College of Tropical Agriculture and Human Resources and previous doctoral student with the UH Mānoa School of Ocean and Earth Science and Technology (SOEST).
The research team, which included scientists from UH Mānoa, NIOZ, Scripps Institution of Oceanography and University of California, Santa Barbara, conducted experiments on bleached and unbleached corals gathered during a bleaching event in Moorea, French Polynesia in 2019.
“Although coral bleaching is a well-documented and increasingly widespread phenomenon in reefs across the globe, there has been relatively little research on the implications for reef water column microbiology and biogeochemistry,” said Craig Nelson, senior author on the study and professor in SOEST.
In a heating experiment, the team determined that both thermally stressed and bleached coral exude a different composition of organic matter in response to thermal stress as compared to unbleached coral. These unique compounds fed microbial communities in the surrounding water, causing an increase in their abundance.
“Interestingly, the microbes responding to bleaching coral exudates were distinct from those grown on healthy coral exudates,” said Sparagon. “And, there were higher abundances of fast-growing opportunists and potential pathogens. The growth of these microbial communities around stressed corals may harm corals, either through suffocation or by introducing disease.”
The biggest surprise was that this shift in the compounds coral release occurred in coral that experienced any stress in the study: corals that had been warmed but not bleached yet, corals that were both heated and bleached, and corals that had bleached previously in the field.
“This suggests that this process occurs throughout the period of coral bleaching, from onset of thermal stress all the way through recovery,” said Milou Arts, co-lead author of NIOZ. “Importantly, it is most pronounced in healthy corals under thermal stress, suggesting that it is most influential at the onset of thermal stress and may push corals towards more severe bleaching and ultimately, mortality.”
The researchers are now actively working on identifying compounds and microbes in the water column that serve as an early-warning system for coral reefs under stress. This could enhance or complement other coral reef conservation efforts, especially in terms of identifying coral reef stress before catastrophic damage has occurred.
Authors Dr. Irina Koester (left) and Jessica Bullington (right) and co-lead author Dr. Wesley Sparagon (center) using a peristaltic pump to sample microbial communities at Gump Station in Mo'orea.
CREDIT
Craig Nelson, UH Manoa/ SOEST
AUTHOR DR. ZACH QUINLAN (LEFT) AND CO-LEAD AUTHOR MILOU ARTS (RIGHT) COLLECT DISSOLVED ORGANIC CARBON SAMPLES USING A PERISTALTIC PUMP.
Woods Hole, Mass. (February 12, 2024) – Studying a rock is like reading a book. The rock has a story to tell, says Frieder Klein, an associate scientist in the Marine Chemistry & Geochemistry Department at the Woods Hole Oceanographic Institution (WHOI).
The rocks that Klein and his colleagues analyzed from the submerged flanks of the St. Peter and St. Paul Archipelago in the St. Paul’s oceanic transform fault, about 500 km off the coast of Brazil, tells a fascinating and previously unknown story about parts of the geological carbon cycle.
Transform faults, where tectonic plates move past each other, are one of three main plate boundaries on Earth and about 48,000 km in length globally, with the others being the global mid-ocean ridge system (about 65,000 km) and subduction zones (about 55,000 km).
Carbon cycling at mid-ocean ridges and subduction zones has been studied for decades. In contrast, scientists have paid relatively scant attention to CO2 in oceanic transform faults. The transform faults were considered “somewhat boring” places for quite some time because of the low magmatic activity there, says Klein. “What we have now pieced together is that the mantle rocks that are exposed along these ocean transform faults represent a potentially vast sink for CO.,” he says. Partial melting of the mantle releases CO2 that becomes entrained in hydrothermal fluid, reacts with the mantle closer to the seafloor, and is captured there. This is a part of the geological carbon cycle that was not known before,” says Klein, lead author of a new journal study “Mineral Carbonation of Peridotite Fueled by Magmatic Degassing and Melt Impregnation in an Oceanic Transform Fault,” published inthe Proceedings of the National Academy of Sciences (PNAS).Because transform faults have not been accounted for in previous estimates of global geological CO2 fluxes, the mass transfer of magmatic CO2 to the altered oceanic mantle and seawater may be larger than previously thought.”
”The amount of CO2 emitted at the transform faults is negligible compared to the amount of anthropogenic - or human driven - CO2,” says Klein. “However, on geological timescales and before humans emitted so much CO2, geological emissions from Earth’s mantle – including from transform faults – were a major driving force of Earth’s climate.”
As the paper states, “global anthropogenic CO2 emissions are estimated to be on the order of 36 gigatons (Gt) per year, dwarfing estimates of average geological emissions (0.26 Gt per year) to the atmosphere and hydrosphere. Yet, over geological timescales, emissions of CO2 sourced from Earth’s mantle have been pivotal in regulating Earth’s climate and habitability, as well as the C [carbon]-concentration in surface reservoirs, including the oceans, atmosphere, and lithosphere.” Klein adds that “this is before anthropogenic combustion of fossil fuels, of course.”
“In order to fully understand modern human-caused climate change, we need to understand natural climate fluctuations in Earth’s deep past, which are tied to perturbations in Earth’s natural carbon cycle. Our work provides insights into long-timescale fluxes of carbon between Earth’s mantle and the ocean/atmosphere system,” says co-author Tim Schroeder, member of the faculty at Bennington College, Vermont. “Large changes in such carbon fluxes over millions of years have caused Earth’s climate to be much warmer or colder than it is today.”
To better understand carbon cycling between Earth’s mantle and the ocean, Klein, Schroeder, and colleagues studied the formation of soapstone “and other magnesite-bearing assemblages during mineral carbonation of mantle peridotite” in the St. Paul’s transform fault, the paper notes. “Fueled by magmatism in or below the root zone of the transform fault and subsequent degassing, the fault constitutes a conduit for CO2-rich hydrothermal fluids, while carbonation of peridotite represents a potentially vast sink for the emitted CO2.”
The researchers argue in the paper that “the combination of low extents of melting, which generates melts enriched in incompatible elements, volatiles and particularly CO2, and the presence of peridotite at oceanic transform faults creates conditions conducive to extensive mineral carbonation.”
The rocks were collected using human-occupied vehicles during a 2017 cruise to the area.
Finding and analyzing these rocks “was a dream come true. We had predicted the presence of carbonate-altered oceanic mantle rocks 12 years ago, but we couldn’t find them anywhere,” says Klein. “We went to the archipelago to explore for low-temperature hydrothermal activity, and we failed miserably in finding any such activity there. It was unbelievable that we were able to find these rocks in a transform fault, because we found them by chance while looking for something else.”
Funding for this research was provided by the Dalio Ocean Initiative, the Independent Research & Development Program at WHOI, and the National Science Foundation.
A cut slice of altered mantle rock.
CREDIT
(Photo by: Solvin Zankl)
Authors:
Frieder Klein1*, Timothy Schroeder2, Cédric M. John3, Simon Davis3, Susan E. Humphris1, Jeffrey S. Seewald1, Susanna Sichel4, Wolfgang Bach5, and Daniele Brunelli6,1
Affiliations:
1Woods Hole Oceanographic Institution, Woods Hole, MA, USA
2Natural Sciences Division, Bennington College, Bennington, VT, USA
3Department of Earth Science and Engineering, Imperial College London, London, UK
4Universidade Federal Fluminense, 24.210-340 Niteroi, Brazil
5Fachbereich Geowissenschaften, Universität Bremen, Bremen, Germany
6Dipartimento di Scienze della Terra, University of Modena, St. Eufemia 19, 41100, Modena, Italy
*Corresponding author
About Woods Hole Oceanographic Institution
The Woods Hole Oceanographic Institution (WHOI) is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. WHOI’s pioneering discoveries stem from an ideal combination of science and engineering—one that has made it one of the most trusted and technically advanced leaders in basic and applied ocean research and exploration anywhere. WHOI is known for its multidisciplinary approach, superior ship operations, and unparalleled deep-sea robotics capabilities. We play a leading role in ocean observation and operate the most extensive suite of data-gathering platforms in the world. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility. For more information, please visit www.whoi.edu
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