How Kelp Forests Bounce Back in Quickly Warming Seas

Jenn Hoskins
11th March, 2024

How Kelp Forests Bounce Back in Quickly Warming Seas

Image Source: Natural Science News, 2024

Key Findings

  • In Nova Scotia, cold-tolerant kelp species declined, replaced by warm-tolerant types since 1982
  • Kelp abundance slightly increased since 2000, thriving in cooler, wave-exposed areas
  • Sea urchin loss, not warming, is a key change driver in these kelp forests
Kelp forests are underwater ecosystems formed by large seaweeds and are crucial for marine biodiversity, providing habitat and food for a variety of marine life. However, these forests are under threat from climate change, which is causing ocean temperatures to rise and altering marine habitats. In recent decades, scientists have observed significant variability in the response of kelp forests to these changes, with some areas showing resilience while others suffer losses. A recent study by Fisheries and Oceans Canada[1] has shed light on the dynamics of kelp forests along the Atlantic coast of Nova Scotia over the past 40 years. The research aimed to understand the variability in kelp persistence and resilience to environmental changes, particularly in the face of climate change. The study involved a comprehensive survey of macrophyte abundance at 251 sites from 2019 to 2022. The researchers compared current kelp species occurrences to those recorded in a similar survey conducted in 1982. They also evaluated changes in kelp abundance over the past 22 years and related these patterns to environmental metrics such as temperature and wave exposure. The findings revealed a shift in the kelp community composition in Nova Scotia. Since 1982, there has been a decline in cold-tolerant kelp species, such as Alaria esculenta, Saccorhiza dermatodea, and Agarum clathratum. In their place, more warm-tolerant kelps like Saccharina latissima and Laminaria digitata have become widely abundant. Interestingly, kelp abundances have generally increased slightly since 2000, with the highest cover found on wave-exposed shores and at sites where temperatures have remained below the thresholds for growth (21 °C) and mortality (23 °C). The study also observed that kelp has managed to recover from turf dominance after significant losses during a warm period from 2010 to 2012. This finding contrasts with global trends[2] that have shown a widespread replacement of marine forests by turf algae, leading to habitat homogenization and the loss of complex underwater structures. Importantly, the loss of sea urchins, which are known to feed on kelp, was identified as a significant change in the ecosystem. The decline in urchin populations has altered the dynamics of the kelp forests, as urchins play a crucial role in shaping these habitats[3]. The study suggests that the loss of urchin herbivory has been a dominant driver of change, rather than the anticipated broad-scale shift to turf dominance. The findings from Nova Scotia are consistent with observations from other regions, where fine-scale temperature variations and biotic interactions have been critical in determining kelp forest persistence during marine heatwaves[3]. In addition, the loss of unique genetic diversity in kelp populations at the edges of their range due to climate-mediated warming, as observed in the Sultanate of Oman[4], underscores the importance of understanding local and regional drivers of kelp forest dynamics. The Arctic, as one of the fastest-warming areas, has also seen changes in its marine forest distributions, with predictions of habitat losses for cold-loving species and shifts towards more temperate regimes[5]. Although the Nova Scotia kelp forests are not in the Arctic, the principles of species' responses to warming waters and the loss of colder habitat can be paralleled. In conclusion, the study by Fisheries and Oceans Canada provides valuable insights into the resilience and persistence of kelp forests in Nova Scotia amidst rapid climate warming. It highlights the importance of local environmental conditions and species adaptations in the face of global climate change. The research contributes to a growing body of evidence that while kelp forests are vulnerable, they also display remarkable variability in their response to changing oceans, with some areas showing an encouraging capacity for recovery and adaptation.

EnvironmentEcologyMarine Biology

References

Main Study

1) Loss, resilience and recovery of kelp forests in a region of rapid ocean warming.

Published 8th March, 2024

https://doi.org/10.1093/aob/mcad170

Related Studies

2) Homogenization and miniaturization of habitat structure in temperate marine forests.

https://doi.org/10.1111/gcb.15759

3) Microclimate predicts kelp forest extinction in the face of direct and indirect marine heatwave effects.

https://doi.org/10.1002/eap.2673

4) Loss of a globally unique kelp forest from Oman.

https://doi.org/10.1038/s41598-022-08264-3

5) Arctic marine forest distribution models showcase potentially severe habitat losses for cryophilic species under climate change.

https://doi.org/10.1111/gcb.16142


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