Termed the "lungs of the sea," seagrasses are vital to maintaining healthy underwater ecosystems.
Seagrass meadows convert carbon dioxide into oxygen through photosynthesis, absorbing nutrients,
improving overall water and air quality1. Seagrasses capture and store such large quantities of atmospheric carbon dioxide that they assist in mitigating global warming2. Seagrasses increase biodiversity, provide habitats, stabilize sediments, and are ideal nurseries3. Seagrass's high primary production (photosynthesis) rate increases species’ abundance, enhances regional fishing, and provides human food security4. Seagrass meadows are coastal protection elements diminishing wave energy and preventing erosion5. Despite their  cological and economic importance, seagrass meadows suffer a rapid global decline, primarily from anthropogenic operations6.

Coastal fish farming is one of the most significant local stressors to seagrass ecosystems7. To maximize
yield, fish in farms are fed with dry fodder, and chemicals are applied to prevent disease and biofouling8. These inputs, coupled with outputs including fish faeces, contaminate the surrounding natural
environment9. Fish farming has contributed to significant environmental degradation, including increasing sedimentation, altering nutrient flow, and spreading disease10. Since Seagrasses have one of the highest light requirements of aquatic photoautotrophs, they are particularly impacted by factors contributing to water turbidity11. Thus, the rapid accumulation of organic matter and sediment from aquaculture hinders seagrass’s growth and increases mortality. 

Unfortunately, ideal seagrass habitat conditions are also optimal for fish farming activity and often coincide12. Various studies have reported significant effects from fish farming on seagrass meadows across biochemical, physiological, morphological, and ecological metrics. A 2025 Oxford research paper demonstrates aquaculture's considerable impact on seagrass health. This study, around the Greek island of Poros, provides clear evidence of the adverse effects of fish farming on seagrass at individual, population, and community levels. Three key seagrass health indicators were measured: leaf length, meadow cover, and epiphyte cover. The data showed that fish farming activity is associated with long-term reduced seagrass health. Seagrass meadow cover declined by 46 percent near active farms and remained depressed 14 years after fish farm removal. Although adverse fish farming effects diminished with distance, significant health reductions were maintained at distances up to 900m from farms. These results demonstrate that fish farming impacts are most severe near farms but still impact populations over large distances beyond the farm boundaries. The images below, taken during the research period, illustrate the drastic seagrass meadow health differences between sites near fish farms and those not.

 

Images: obtained from 2025 Oxford Jones field survey footage stills at a control site and a site within 500m of an aquaculture.  

 

References:

1. Terrados, J., & Borum, J. (2004). Why are seagrasses important?-Goods and services provided by seagrass meadows. European seagrasses: an introduction to monitoring and management, 8-10.

2. Hejnowicz, A. P., Kennedy, H., Rudd, M. A., & Huxham, M. R. (2015). Harnessing the climate mitigation, conservation, and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programs. Frontiers in Marine Science, 2, 32.

3. Terrados, J., & Borum, J. (2004). Why are seagrasses important?-Goods and services provided by seagrass meadows. European seagrasses: an introduction to monitoring and management, 8-10.

4. Strachan, Laura L., Richard J. Lilley, and Sebastian J. Hennige. "A regional and international framework for evaluating seagrass management and conservation." Marine Policy 146 (2022): 105306.

5.  Terrados, J., & Borum, J. (2004). Why are seagrasses important?-Goods and services provided by seagrass meadows. European seagrasses: an introduction to monitoring and management, 8-10.

6. Hejnowicz, A. P., Kennedy, H., Rudd, M. A., & Huxham, M. R. (2015). Harnessing the climate mitigation, conservation, and poverty alleviation potential of seagrasses: prospects for developing blue carbon initiatives and payment for ecosystem service programs. Frontiers in Marine Science, 2, 32.

7. Jones, Emily (2025). Investigating the Impacts of Fish Farming on Posidonia oceanica Seagrass Meadow Health in Poros, Greece. University of Oxford.

8. Jones, Emily (2025). Investigating the Impacts of Fish Farming on Posidonia oceanica Seagrass Meadow Health in Poros, Greece. University of Oxford.

9. Jones, Emily (2025). Investigating the Impacts of Fish Farming on Posidonia oceanica Seagrass Meadow Health in Poros, Greece. University of Oxford.

10. Jones, Emily (2025). Investigating the Impacts of Fish Farming on Posidonia oceanica Seagrass Meadow Health in Poros, Greece. University of Oxford.

11. Capistrant-Fossa, K. A., & Dunton, K. H. (2024). Rapid sea level rise causes the loss of seagrass meadows. Communications Earth & Environment, 5(1), 87.

12. Jones, Emily (2025). Investigating the Impacts of Fish Farming on Posidonia oceanica Seagrass Meadow Health in Poros, Greece. University of Oxford.