How changing ocean conditions impact sea urchin reproduction

Jim Crocker
21st December, 2025

How changing ocean conditions impact sea urchin reproduction

Arctic Green Sea Urchin (Strongylocentrotus droebachiensis)

Photo adapted from: Frédérique / CC BY (Source)

Key Findings

  • This study, conducted in Kongsfjorden, Svalbard, examined how ocean acidification, warming, and salinity affect green sea urchin fertilization
  • Temperature had the greatest impact on fertilization success, with warming generally increasing it, while pH had a secondary effect
  • The combination of warming and pH was complex, with warming enhancing fertilization more at higher pH levels, suggesting temperature alone may not offset acidification’s negative effects
Marine ecosystems are undergoing rapid changes due to climate change, particularly the increasing levels of carbon dioxide in the atmosphere, which leads to ocean acidification (OA) and ocean warming (OW). The Arctic region is especially sensitive to these changes, making it crucial to understand how marine life there will respond.[2] highlights the broad impacts of climate change on ocean ecosystems, including decreased productivity and shifting species distributions. A recent study by researchers at the Norwegian Polar Institute[1] investigated how multiple environmental stressors – ocean acidification, warming, and changes in salinity – affect the fertilization success of the green sea urchin (Strongylocentrotus droebachiensis) in Kongsfjorden, Svalbard. The study focused on fertilization, the initial step in reproduction, as it is often sensitive to environmental conditions and can indicate the overall health of a population. Gametes, or sex cells, from the sea urchins were exposed to different combinations of pH levels (measuring acidity), temperatures, and salinity levels in a controlled laboratory setting. The researchers then measured the rate of successful fertilization under each condition. The results revealed that both temperature and pH had a significant impact on fertilization rates, but temperature was the more important factor. Salinity, however, did not significantly affect fertilization success. This is notable because while all three stressors are changing in Arctic waters, temperature appears to be the primary driver of reproductive success in this species. Importantly, the study found an interaction between temperature and pH. This means the effect of temperature on fertilization depended on the pH level. Warming enhanced fertilization, but this effect was stronger at higher pH levels. Conversely, low pH levels suppressed the positive effect of warming. These findings build on previous research that has often examined stressors in isolation. For instance, a study on Heliocidaris erythrogramma sea urchins found that while fertilization was initially resilient to changes in temperature and pH, negative effects emerged at higher warming levels[3]. The Norwegian Polar Institute study goes further by demonstrating that the combined effect of warming and acidification is more complex than simply adding the individual effects together. To determine the relative importance of each stressor, the researchers used a statistical model. This model confirmed that temperature was the dominant factor influencing fertilization, followed by pH. This suggests that while acidification is a concern, managing warming temperatures may be more critical for maintaining sea urchin populations in this region. Interestingly, earlier work on sea urchin fertilization showed that it could be robust to climate change stressors, at least in some species[4]. This contrasts with the findings of, which show a clear effect of temperature and pH, highlighting potential species-specific differences in vulnerability. The Norwegian Polar Institute's research emphasizes the need to consider the specific environmental context when assessing the impacts of climate change. The study underscores that Arctic ecosystems are experiencing accelerated environmental change, and understanding the combined effects of multiple stressors is essential for predicting the future of marine life in these sensitive regions.

EcologyOceanographyMarine Biology

References

Main Study

1) Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins

Published 18th December, 2025

https://doi.org/10.1038/s41598-025-27725-z

Related Studies

2) The impact of climate change on the world's marine ecosystems.

https://doi.org/10.1126/science.1189930

3) Temperature, but not pH, compromises sea urchin fertilization and early development under near-future climate change scenarios.

https://doi.org/10.1098/rspb.2008.1935

4) Sea urchin fertilization in a warm, acidified and high pCO2 ocean across a range of sperm densities.

https://doi.org/10.1016/j.marenvres.2009.10.014


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