New body-size database holds the key to saving marine life

New body-size database holds the key to saving marine life
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• A new database cataloging the maximum body size of marine animals looks set to be crucial in conservation efforts 

• The database will plug gaps in scientific knowledge around the impact of body size on  marine animal ecosystems, their evolution and their  response  to environmental threats

•  Created by a team of researchers, including a University of Sheffield academic, the tool opens the door to a deeper understanding of the ocean’s biodiversity

A new database detailing  the maximum body size of marine life  will shed light on species at risk from climate change and habitat degradation, paving the way for targeted protection.

Unlike the terrestrial animal kingdom, there are gaps in scientific understanding of how size has affected marine animal ecosystems, their evolution and how they could respond to environmental threats. 

Where information is known about the size of marine animal species, it has tended to focus on the larger marine animals.

Now, an international group of scientists, including a researcher from the University of Sheffield, has created a database holding information on 85,000 marine animal species. 

Known as the Marine Organismal Body Size Database or MOBS, it covers a range of species from microscopic zooplankton to whales. 

Dr Tom Webb, from the School of Biosciences at Sheffield and one of the researchers involved in the project, said: “Put simply, biologists have tended to focus on bigger organisms. And as a result, a lot of our understanding of how marine food webs and ecosystems work is based on knowledge of these larger species. 

“But we also know that small-bodied species are really important: they constitute the majority of biodiversity, and are likely to fulfil unique and important functions within their ecological communities. 

“Body size is such a key trait - important in determining how species interact with each other, and how they will react to a changing environment. The more species for which we are able to put a size to a name, the more accurate and representative our predictions about the fate of marine biodiversity can be.”

The scientists have announced the release of the database today (June 5) in the scientific journal Global Ecology and Biogeography. The paper, entitled - MOBS 1.0: A database of interspecific variation in marine organismal body sizes - outlines how the knowledge of the body size of most marine animals remains "conspicuously inadequate”.

This severely limits the ability to predict and deal with how environmental changes, like climate change, overfishing, and habitat destruction, affect these ocean environments.

A broader understanding of size is important as scientists recognise that marine food webs are typically very highly-size structured, with bigger organisms eating smaller organisms. This matters - for example, fishing for big fish has implications for their smaller prey and vice versa.

Studies also show larger birds are more susceptible to extinction than smaller birds.

So far, around 40 percent of marine species have been included in the database. Over the next couple of years, the researchers hope to increase coverage to 75 percent of marine animal species.

Professor Craig R. McClain, from the University of Louisiana and lead creator of the database, added: “Body size isn’t just a number—it’s a key to how life works.

 “For decades, we’ve had this enormous data gap in marine life. MOBS doesn’t just close that gap—it opens the door to a deeper understanding of the ocean’s biodiversity.”

The database is open source and can be accessed at github: https://github.com/crmcclain/MOBS_OPEN

The study is an example of the breadth of research covered in the University’s School of Biosciences, which aims to train students to solve some of the world's biggest challenges, from cancer, antimicrobial resistance and healthy ageing, to climate change and saving the planet’s biodiversity.

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Notes to editors

Study Biosciences at the University of Sheffield

The paper  - McClain, C. R., Heim, N. A., Knope, M. L., Monarrez, P. M., Payne, J. L., Santos, I. T., & Webb, T. J. (2025). MOBS 1.0: A database of interspecific variation in marine organismal body sizes. Global Ecology and Biogeography - is available online (https://onlinelibrary.wiley.com/doi/10.1111/geb.70062)

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