New study finds marine animals save energy by swimming in a depth ‘sweet spot’
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Like many air-breathing marine megafauna, green turtles optimise their swim depth during migration to minimise the cost of transport, travelling at around three body-depths beneath the surface in order to avoid creating waves whilst maximising horizontal distance travelled.
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Credit: Credit: R. D. and B. S. Kirkby.
R,esearchers from Swansea and Deakin Universities have found that marine animals across mammals, birds and reptiles swim at similar relative depths when travelling and not feeding to save energy.
Dr Kimberley Stokes, Professor Graeme Hays and Dr Nicole Esteban from Swansea and Deakin Universities, led research across six institutes in five countries comparing the swim depths of several sea turtle, penguin and whale species. All travelled at around three body depths from the surface in order to swim in the 'sweet spot' that minimises wave formation at the surface and vertical distance travelled.
Some semi-aquatic animals, such as mink, swim at the surface where wave generation is a major source of wasted energy. However for marine birds, mammals and reptiles travelling great distances over their lifetimes, adaptation to minimise the energetic cost of transport is expected, particularly on long journeys.
It has long been known that additional drag from wave creation minimises once a travelling object is at depths greater than three times its diameter, but it was hard to compare with travel depths of wild animals due to tracking limitations.
In this new study published in Proceedings of the National Academy of Sciences (PNAS) near surface swim depths were recorded to within 1.5 centimetres in little penguin and loggerhead turtles, along with motion data and video footage from animal borne cameras. This was compared with satellite tracking data for long-distance migrations in green turtles and data from other studies on penguins and whales. It was found that these animal swim at optimal depths predicted from physics when either 'commuting' to a foraging patch in the wild or migrating over longer distances while not feeding.
Swansea University’s Dr Kimberley Stokes, lead author of the study said:
“There are of course examples where animal swim depth is driven by other factors, such as searching for prey, but it was exciting to find that all published examples of non-foraging air-breathing marine animals followed the predicted pattern. This has rarely been recorded because of the difficulty in retrieving depth data from animals that migrate over large distances, so it was great to find enough examples to show a common relationship between swim depth and body size from animals across the size spectrum from 30 cm to about 20 m in length.”
Little penguins travel beneath the zone of highest wave drag close to the surface. Many air-breathing marine vertebrates optimise their swim depth when transiting and not feeding, travelling just deep enough to avoid wave creation on the surface.
Credit
Phillip Island Nature Parks.
Journal
Proceedings of the National Academy of Sciences
Subject of Research
Animals
Article Title
Optimization of swim depth across diverse taxa during horizontal travel
Article Publication Date
16-Dec-2024
Corals depend on near neighbours to reproduce
University of Queensland
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Coral spawning in Palau.
view moreCredit: Peter Mumby
A new study reveals corals must be within only a few metres of each other to successfully reproduce, leaving them vulnerable in a warming world.
The international research, led by The University of Queensland’s Professor Peter Mumby, measured the success of a natural spawning event in March this year.
“In what came as a surprise, we saw that corals needed to be within 10 metres of one another, and preferably closer than that for fertilisation to take place,” Professor Mumby said.
“We knew corals couldn’t be too far apart, but we found they need to be closer than we’d expected.
“Climate change impacts like bleaching are killing and reducing the density of corals, so we’re concerned that individuals may end up too far apart to reproduce successfully.”
To quantify reproduction success, the team placed containers above 26 coral colonies on a reef in Palau, Micronesia during a time when the mostly hermaphroditic corals released eggs and sperm.
“The containers captured some of each corals’ eggs and drifted to the surface where they followed the tide,” Professor Mumby said.
“Although the eggs could not escape, sperm could enter the container and fertilise the eggs.
“After an hour of drifting, the proportion of fertilised eggs was noted for each type of coral along with the distance to similar established corals.”
Fertilisation averaged 30% when corals were very close, but it declined to less than 10% at a separation of 10 metres and was virtually zero by 20 metres.
Co-author Dr Christopher Doropoulos of the CSIRO, Australia’s national science agency, said coral reproduction was fundamental to population resilience and evolution.
“In the future we may need to help corals continue this key part of their lives,” Dr Doropoulos said.
“Understanding the importance of local neighbourhoods provides tangible targets for interventions like coral restoration.
“Ideally, the density of corals would be monitored at important locations and restoration carried out to return the density back to the levels required for successful reproduction.”
Professor Mumby has been working on efforts to repair damaged coral reefs.
“Our work over the past 5 years on the Great Barrier Reef through the Reef Restoration and Adaptation Program is also helping to define these critical thresholds to help restoration practitioners set targets for density to help maintain coral populations,” he said.
The study was funded by the McCusker Foundation and the Australian Government’s Reef Restoration & Adaptation Program.
The research is published in the Proceedings of the National Academy of Sciences USA (PNAS).
Images and video available via Dropbox.
Reef research site in Palau.
Credit
Peter Mumby
Journal
Proceedings of the National Academy of Sciences
DOI
Landmark study using 21 years of New England Aquarium’s Marine Conservation Action Fund (MCAF) data finds small grants advance ocean conservation and equity
Perspective piece in the journal Biological Conservation examines how small grants to local projects worldwide yield success in advancing global ocean conservation and equity
A recently-published study in the journal Biological Conservation highlights how small grants can address ocean conservation challenges in a manner that promotes social equity.
Low- and middle-income countries (LMICs) are disproportionately impacted by threats to ocean health, such as overfishing and climate change, which are often caused by the world’s high-income countries (HICs). These inequities and resultant challenges affecting both marine biodiversity and livelihoods in LMICs have been driven by a long history of resource extraction and colonialism by HICs. The study authors point to characteristics of grant programs that make them accessible for local leaders, who are best positioned to design conservation action in their communities.
This perspective piece was authored by marine conservationists working with the New England Aquarium’s Marine Conservation Action Fund (MCAF), which is celebrating 25 years of supporting locally based conservation projects and leaders worldwide. Among the paper’s authors are MCAF Director Elizabeth Stephenson and Program Manager Emily Duwan, as well as MCAF fellows and collaborators who have helped shape the program. As a case study for small grants, Stephenson and her colleagues analyzed project characteristics and outcomes from MCAF’s grantmaking over two decades, from 1999-2020. Projects supported by MCAF had immediate impacts, like filling knowledge gaps, protecting individual animals, and strengthening marine protected areas (MPAs). They also contributed to lasting conservation impacts, including new species protections, creating new MPAs, and sustained research and monitoring efforts.
“Historical inequities and current threats to ocean health make flexible grant-making a priority. It is more critical than ever to promote local leadership and ensure that conservationists on the frontlines have funding to develop the solutions they know are needed,” says Stephenson.
In its second decade, MCAF shifted to funding more projects led by individuals working in their own LMICs. This shift helps to combat the problem of “parachute science”—a practice whereby scientists from HICs work in LMICs without meaningful collaboration with local experts. This practice perpetuates inequities in LMICs and is a barrier to creating lasting, locally informed solutions. The authors highlight how grants programs can promote equity in conversation by providing accessible and flexible funding and leaving project design in the hands of local LMIC leaders.
“This analysis, which showcases the evolution of the MCAF program, highlights how supporting locally led conservation efforts can shift the needle on driving change for our oceans,” said co-author and longtime MCAF Fellow Dr. Asha de Vos of Oceanswell in Sri Lanka and The Oceans Institute in Australia. “Funding local leaders ensures that those on the ground, at the forefront of these conservation issues who often work with shoestring budgets year after year, are recognized, supported, and given a seat at the table. It creates a sense of custodianship and inspires future leaders to emerge from these communities. In the end, to save the world's largest ecosystem, we need to build the world's largest team.”
Among the authors’ recommended strategies for grant programs to amplify their impact and promote equitable practices are to:
• Support established and emerging leaders from LMICs,
• Make long-term investments in project leaders and organizations by offering multi-year, unrestricted funding and grants,
• Provide multi-faceted support for project leaders so they can elevate the visibility of their projects,
• And regularly seek feedback and guidance from project leaders on program strategy and funding decisions.
Joining current MCAF staff as co-authors are former MCAF Coordinator Bess-Lyn Edwards; MCAF fellows Dr. Asha de Vos of Oceanswell in Sri Lanka and The Oceans Institute in Australia, Kerstin Forsberg of Planeta Océano in Peru and Migramar of California, and Dr. Nelly Isigi Kadagi of World Wildlife Fund; Benny Berger and Dr. Michael Tlusty of University of Massachusetts Boston; and Dr. Jessica V. Redfern, Associate Vice President in the Aquarium’s Anderson Cabot Center for Ocean Life’s Ocean Conservation Science.
Journal
Biological Conservation
Method of Research
Case study
Subject of Research
People
Article Title
Small grants advance global ocean conservation and management equity
Article Publication Date
14-Nov-2024
COI Statement
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Elizabeth H. Stephenson, Emily Duwan, Bess-Lynn Edwards, and Benny Berger report a relationship with the New England Aquarium's Marine Conservation Action Fund that includes: employment. Nelly Isigi Kadagi, Asha de Vos, and Kerstin Forsberg report a relationship with the New England Aquarium's Marine Conservation Action Fund that includes: funding grants. Nelly Isigi Kadagi, Kerstin Forsberg, and Michael F. Tlusty serve on the New England Aquarium's Marine Conservation Action Fund advisory committee.
New findings on the North Atlantic Oscillation displacement
Why does the NAO move longitudinally?
University of Barcelona
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A study led by a team from the University of Barcelona is helping to resolve some enigmas about the causes of the displacements in the North Atlantic Oscillation (NAO), one of the most influential patterns of variability in the climate of the Northern Hemisphere.
view moreCredit: Npj Climate and Atmospheric Science
There are still many unknowns about the causes leading to the North Atlantic Oscillation (NAO) shift — a critical climate phenomenon in the Northern Hemisphere — to the east and west of Iceland. To date, some hypotheses suggested that this process known to the international scientific community might be related to the impact of greenhouse gases on the planet.
Now, a study published in the journal Npj Climate and Atmospheric Science reveals that the NAO shift may be a consequence of natural variability in the atmospheric system rather than anthropogenic effects altering global climatology. The new study is led by experts María Santolaria-Otín and Javier García-Serrano, from the Faculty of Physics and the Group of Meteorology at the University of Barcelona.
Why does the NAO move longitudinally?
The North Atlantic Oscillation was first identified in the early 20th century, although its consequences were known to the people of northern Europe much earlier. The NAO is one of the most studied climate variability phenomena in the scientific community. However, many aspects of the dynamics and processes controlling its variability, both temporally and spatially, are still unknown, and the evidence for its past and expected future trends is still being debated.
Javier García-Serrano, professor at the UB’s Department of Applied Physics, says that “the atmosphere is a fluid system and shows a very chaotic and unpredictable behaviour. The study reveals that we can rule out some factors that explain this NAO pattern, namely anthropogenic forcing — i.e. the impact of greenhouse gases — or ocean coupling. Factors that could help to understand these shifts in the NAO are, for example, the interaction of winds with orography or the land-sea contrast. However, we need more research studies to confirm these hypotheses”.
On a global scale, the effects of this NAO shift are likely to be small, although they could affect Arctic Sea ice variability and, consequently, other remote areas of the planet. According to the findings, this process would not alter anthropogenic global warming trends.
Regional scale effects would be more important, since the NAO explains about half of the climate variability in the area of the European continent and the Mediterranean. “However, its impact on future predictions and projections would mainly be to modulate climate change trends in certain periods”, says García-Serrano.
In this context, the UB team has carried out and analysed simulations over a period of 500 years with a global climate model. María Santolaria-Otín, postdoctoral researcher and first author of the study, notes that “by applying this innovative methodology, it has been possible to isolate the effects of radiative forcing and ocean coupling and thus obtain conclusions that are impossible to reach with observational data alone”.
The NAO is considered one of the most influential patterns of low-frequency variability (teleconnections) in the climate of the Northern Hemisphere. In this challenging scenario, the UB team continues to expand their studies to understand what factors control NAO shifts and their remote effects in the context of global
Journal
npj Climate and Atmospheric Science
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Internal variability of the winter North Atlantic Oscillation longitudinal displacements
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