The Doctor of Marine Sciences from the ULPGC asserts that one of the most profound changes is occurring, on an almost invisible scale, in this group of small organisms that ‘float in the water column and sustain much of marine life,’ highlighting that the Canary Islands are a great laboratory for studying these climatic alterations.
Inma Herrera, a postdoctoral researcher with the Biodiversity and Conservation (BIOCON) group at the ECOAQUA University Institute, part of the University of Las Palmas de Gran Canaria (ULPGC), points out that when ‘we think about the effects of climate change on the sea, we tend to imagine bleached corals, fish species moving to colder waters or rising sea levels’. . However, she points out, ‘one of the most profound changes is occurring on an almost invisible scale: in zooplankton, a group of small organisms that float in the water column and sustain much of marine life’.
This is one of the main statements that form the backbone of a new article by the ULPGC Doctor of Marine Sciences, recently published in the prestigious scientific journal The Conversation under the title “The tiny marine creatures that can amplify the effects of climate change in the oceans”, which can be consulted at the following link: https://theconversation.com/ las-diminutas-criaturas- marinas-que-pueden-amplificar- los-efectos-del-cambio- climatico-en-los-oceanos- 272627
Herrera asserts that, although barely visible to the naked eye, ‘these creatures react quickly to environmental changes.’ They function, he says, as particularly sensitive indicators of the state of marine ecosystems and the effects of global warming. In fact, planktonic communities are already showing detectable responses to extreme events such as marine heatwaves, with potential consequences for the entire oceanic food web.
In the article, which was also co-authored by Mélisande Payet, an ERASMUS+ student on the Master's in Marine Sciences at the Université de Toulon, the ECOAQUA researcher points out that zooplankton occupies a key position in the oceans, connecting the primary production of phytoplankton – tiny photosynthetic organisms – with higher trophic levels such as fish, birds and marine mammals. ‘Due to their abundance, small crustaceans called copepods stand out. They dominate much of the marine planktonic communities and are highly sensitive indicators of environmental conditions,’ she explains.
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Examples of zooplankton organisms. Mélisande Payet, CC BY-SA.
Indicator of climate change
In the words of the researcher, "rising ocean temperatures, acidification and changes in marine circulation are altering the composition and distribution of zooplankton on a global scale, as reported in the United Nations' third Global Assessment of the Oceans. Many species survive in narrow temperature ranges, so warming water directly affects their survival and reproductive cycles."
In regions such as the Canary Islands, she explains, ‘the changes observed in the structure of planktonic communities suggest that the most sensitive species are being progressively replaced by others that are more tolerant to heat. This also implies a possible reduction in the diversity of the ecosystem.’
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Zooplankton are organisms that float in the oceans and seas. Choksawatdikorn/Zhutterstock
According to Herrera, marine heatwaves do not only affect zooplankton, as "prolonged episodes of abnormally high temperatures can alter the behaviour, physiology and distribution of numerous marine organisms, amplifying the effects of climate change on coastal ecosystems.
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The blue crab (Callinectes sapidus), also known as the blue crab or crab, is a species native to the western Atlantic and the Gulf of Mexico. Jarek Tuszy?ski/Wikimedia Commons, CC BY-SA
This would be the case for the blue crab, which in the eastern Atlantic has been observed to be particularly sensitive to these extreme thermal events. ‘Recent studies,’ explains the researcher, ‘show that the embryonic development of this species has clear upper thermal limits, which could be exceeded under future warming scenarios.’
In the words of the ULPGC scientist, ‘these results confirm that marine heatwaves act as acute stress factors, capable of rapidly modifying crustacean populations and favouring more heat-tolerant species over less resilient ones.’
The Canary Islands, a natural laboratory
In the article, the researcher from the BIOCON group at ECOAQUA asserts that "the Canary Islands are influenced by the cold Canary Current and the processes of upwelling or emergence of deep waters that provide nutrients and sustain high biological productivity. For decades, zooplankton communities have adapted to this oceanographic balance, characterised by marked spatial and seasonal variability."
However, "rising sea temperatures and more frequent marine heatwaves are altering these patterns. Recent studies show that the composition and abundance of zooplankton can change even in protected areas, highlighting the vulnerability of these ecosystems to climate change.
In addition to climatic phenomena, recent geological events can also ‘significantly alter zooplankton dynamics’. In this regard, following the eruption of the Tagoro underwater volcano on the island of El Hierro, ‘planktonic communities experienced detectable changes in their carbon sources and trophic structure,’ he argues.
Alterations in the food chain
Herrara asserts that alterations in zooplankton produce cascading effects on the marine ecosystem. ‘A reduction in its abundance or nutritional quality directly affects fish and other organisms that depend on it, especially during their early life stages,’ he argues.
In addition to climate change, she explains, ‘zooplankton is affected by other emerging human pressures.’ In this regard, a recent study has shown that the copepod Pontella mediterranea can ingest and retain microplastics, acting as a vector for the transfer of these pollutants within marine food webs.
In this context, the researcher emphasises that the latest Global Ocean Assessment "warns that changes in plankton, including zooplankton, may amplify the effects of climate change on marine productivity and food security, especially in coastal regions and island systems. The lack of long time series in many areas, such as the eastern Atlantic, reinforces the need for continuous monitoring programmes that integrate local observations into global assessments."
In this regard, Herrera concludes, scientific initiatives such as the IMPLACOST project, which addresses the effects of climate change in Macaronesia and coastal areas of Africa, provide a key framework for linking physicochemical changes in the marine environment with biological responses, facilitating the integration of environmental data with ecological indicators such as zooplankton.