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A study by IDAEA-CSIC proposes using bacteria associated with copepods as bioindicators to monitor the presence of organic pollutants in the sea
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The method makes it possible to assess the impact of diffuse marine pollution more easily and cost-effectively, even at early stages of exposure and in remote locations
The microbiome of copepods is affected by ocean pollutants. | Claudia Sanz Lanzas
A scientific team led by the Institute of Environmental Assessment and Water Research (IDAEA) of the Spanish National Research Council (CSIC) has demonstrated that the microbiome associated with copepods, small crustaceans that make up the majority of marine zooplankton, can serve as an indicator of the presence of organic pollutants in the ocean. The study, published in Water Research, proposes using the bacterial communities associated with these organisms as a new tool to monitor background marine pollution on a large scale.
Organic pollutants are present in all the world’s oceans. Most are persistent and bioaccumulative, and some are toxic, posing a risk to marine ecosystems. However, directly measuring thousands of different compounds in the marine environment is extremely complex and costly, making systematic global monitoring unfeasible. Moreover, these pollutants occur as complex mixtures and at very low individual concentrations, making it difficult to assess their actual impact on ecosystems.
“In a similar way to how the human gut microbiome can be altered by exposure to compounds such as pharmaceuticals or microplastics, the microbiome associated with marine organisms could be used to assess ecosystem health,” explains Maria Vila-Costa, IDAEA researcher and lead author of the study.
To test this, the researchers analysed copepod samples collected at 24 locations along a latitudinal gradient of more than 10,000 km in the Atlantic Ocean, from Vigo (Spain) to Punta Arenas (Chile). The results of the oceanographic campaign showed a clear correlation between certain groups of bacteria present in the copepod microbiome and the concentration of different organic pollutants in seawater, such as plasticisers and organophosphate flame retardants (OPEs), polycyclic aromatic hydrocarbons (PAHs) and some perfluorinated compounds.
The ANTOM oceanographic campaign monitored pollutants across the Atlantic. | Maria Vila-Costa
To confirm these findings, the team also conducted laboratory experiments exposing copepods to environmentally relevant concentrations of plasticisers and organophosphate flame retardants. The results showed similar changes in the organisms’ microbiome and a decrease in egg production, indicating effects on reproduction.
Detecting pollution before it becomes visible
The microbiome associated with organisms can act as an early indicator of exposure to pollutants, even when they are present in a dispersed manner and at very low concentrations, as is typically the case in the oceans.
Unlike traditional chemical analyses, this approach offers several advantages: it enables the detection of exposure to complex mixtures of pollutants, works across large geographical scales, and may be more cost-effective and easier to implement in monitoring programmes.
“Microbiomes respond very sensitively to the chemistry of their surroundings, making them a highly promising tool for detecting exposure to pollutants at early stages, not only when environmental damage has already become irreversible,” says María Paula Carrillo, IDAEA-CSIC researcher and first author of the study.
Copepods are particularly well suited to this type of research because they are the main component of marine zooplankton, are present in all the world’s oceans, play a key role in marine food webs, and are relatively easy to sample and study.
The authors propose incorporating microbiome analysis in invertebrates into marine environmental monitoring strategies in order to effectively address exposure to chemical pollution in the current context of global change.
Maria Paula Carrillo, Naiara Berrojalbiz, Claudia Sánz, et al. (2026) Copepod-associated microbiome responses to organophosphate ester plasticizers and other bioaccumulative organic pollutants in the ocean. Water Research, 296, 125640, DOI: 10.1016/j.watres.2026.125640
