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Dalmiro Borzone Mas, Pablo A. Scarabotti, Patricio Alvarenga, Pablo A. Vaschetto, and Matías Arim: Read the article
How are diversity, food web structure, and ecosystem functioning related? Here Borzone Mas et al. analyze the interrelationship between these three components in predatory fishes of the Paraná River
S cientists are becoming increasingly vocal about the destructive impacts of what has been called a “silent crisis”: the subtle but ultimately devastating creep of biodiversity loss across our planet. From the smallest insects to the most awe-inspiring whales, species on every branch of the tree of life are declining in numbers or disappearing altogether, sometimes without ever being documented by humans. This catastrophe can be difficult to quantify because it has cascading effects. Not only are prey species affected by climate change, habitat loss, and pollution, but their predators are as well. What do you eat when your food source has been wiped out by a potent pesticide, or has migrated further north in search of cooler seas? This effect can be visualized with a food web, where predators and their prey are linked using arrows to show how species interact.
Biodiversity loss, on a larger scale, negatively impacts how well an ecosystem can operate as a unit. This relationship is called the biodiversity-ecosystem functioning relationship. It is measured using species richness (the number of species in an ecosystem), biomass (the weight of organisms produced by a particular ecosystem), energy flows, and ecosystem stability. It indicates that ecosystems are more stable and productive when there are more species present to fill specific niches and provide ecosystem services. When studying this relationship, biomass is considered to be one of the main aspects of ecosystem function. This article takes a new approach by investigating how fish species richness affects food web structure and biodiversity-ecosystem function in the Paraná River.
To conduct this study, scientists compared the stomach contents of fish species from water bodies located within the Paraná River’s floodplain. They created food webs that were each characterized using metrics that describe the species in the web, their linkages, and the web’s complexity. They also measured their catch’s biomass to compare it across each web. During their analysis, they found that as species richness increased, so did the number of linkages per species, the compartmentalization of the web into subgroups, and the number of species that acted as links between subgroups. The more complex the food webs were, with higher linkages per species and more subgroups, the better the ecosystem function. In other words, a greater diversity of species in a system can reshape food webs for the better, making them more complex and therefore more productive.
However, one metric was negatively impacted by increased species richness: nestedness. Nestedness is the number of interactions between species that consume many different types of prey and those that only consume a subset of that prey. In addition, scientists found that the relationship between species richness and biomass is not a straightforward relationship but instead operates indirectly through the three positive pathways and one negative pathway listed above. This result led the authors to conclude that conservation efforts in the future that combat biodiversity loss should not just focus on preserving the number of species but should emphasize preservation of food web complexity. This complexity protects ecosystems by making them more productive and resilient.
This article is a clear example of how ecosystem-based management strategies will be crucial in addressing the biodiversity crisis. Its emphasis on the importance of biodiversity in maintaining a balanced and productive ecosystem through the lens of food webs shows how a more holistic view of the world around us can lead to more effective management. Check out the article for a fresh take on how fish guts can show us a path forward to preserve our biodiverse planet!
Katherine Helmer is a lab technician in the Department of Ecology and Evolutionary Biology at the University of Connecticut, where she studies the decline of flatfish in Long Island Sound. She graduated from the University of Vermont with a B.S. in Environmental Science and shifted to working with marine fisheries in roles at the state level in Massachusetts and Connecticut. At the University of Connecticut, she uses scales and eye lenses to recreate growth and feeding patterns of decades-old fish samples and compare them to current trends. In her spare time, she enjoys bird watching, knitting, watching horror movies, and looking for treasures at thrift stores.
