A recent study conducted by researchers at Oregon State University’s Marine Mammal Institute has shown that the booming population of purple sea urchins off the southern Oregon Coast has had a negative impact on the gray whale population. This population explosion of sea urchins has resulted in the destruction of kelp forests, which are critical habitats for zooplankton, the primary prey of many marine animals. As a result, gray whales are spending less time foraging in the region, affecting them negatively. The study was published in Nature Scientific Reports and highlights the cascading impacts of changes in the coastal ocean ecosystem.
The rise in sea urchin populations off the coast of Oregon was a result of the Sea Star Wasting Syndrome pandemic that began in 2013, leading to a 90% decline in sunflower sea stars, which are natural predators of sea urchins. The absence of sea otters, another predator of sea urchins that was wiped out in Oregon waters over a century ago, has contributed to the lack of redundancy in the ecosystem. Without both sea otters and sea stars, the ecosystem struggles to maintain balance, resulting in the dominance of sea urchins and the subsequent destruction of kelp forests.
The research team, led by Associate Professor Leigh Torres, has been monitoring the gray whale population and their environment off the coast of Port Orford since 2015 as part of a 10-year study on the foraging ecology of gray whales in the Pacific Coast Feeding Group. The team has been studying the impact of the sea urchin population explosion on the gray whale population, observing fewer whales and a decline in their body condition in recent years. The team hypothesizes that the decline in kelp leads to a decline in zooplankton, as the kelp provides shelter for the tiny organisms.
The researchers suspect that the decline in kelp and subsequent decline in zooplankton may be due to ocean warming caused by climate change. Marine heatwaves and warmer ocean waters likely worsened the Sea Star Wasting Syndrome pandemic, affecting the growth of young kelp that tends to thrive in colder water. However, the researchers noted signs of recovery in the region in 2023, with fewer sea urchins and more kelp, zooplankton, and whales being observed. This suggests that the ecosystem may be returning to conditions favorable for kelp growth, providing hope for the future of the habitat.
The study emphasizes the importance of understanding the interconnectedness of marine ecosystems and how changes in one species can have cascading effects on others. Monitoring the gray whale population and their habitat is crucial for ensuring the health and sustainability of the ecosystem. The researchers will continue their research to track the recovery of the ecosystem and the impacts on the gray whale population. The study was funded in part by Oregon Sea Grant and conducted at the Marine Mammal Institute at Oregon State University’s Hatfield Marine Science Center.
Overall, the study sheds light on the complex interactions within marine ecosystems and the importance of maintaining biodiversity and balance to support healthy populations of marine animals. As the researchers continue to monitor the region and the gray whale population, they hope to contribute valuable insights into how human activities and environmental changes impact marine ecosystems and the animals that rely on them. The findings of this study have implications for conservation efforts and the management of marine resources to ensure the long-term health and resilience of coastal ecosystems.