Spotlight on the Science
Dr. Heidi Pearson outlines her research focus for summer of 2015: whales, otters and blue carbon in the coastal ecosystems of Southeast Alaska.
Marine mammals provide important ecosystem services that can help to combat climate change, including interactions with marine algae. Marine algae are important components of the carbon cycle because they capture and store atmospheric CO2. The “whale pump” and “trophic cascade” are two mechanisms through which marine mammals help to reduce atmospheric CO2 levels by promoting the growth of marine algae (phytoplankton and kelp). Our project focuses on understanding how humpback whales and sea otters stimulate the growth of marine algae in coastal marine ecosystems of Southeast Alaska.
Through the action of the whale pump, whales “fertilize” surface waters by producing buoyant faecal plumes that are rich in limiting nutrients such as nitrogen and iron. By feeding at depth and defecating at the surface, whales transfer nutrients to surface waters that are critical to phytoplankton growth. This project will compare nutrient levels between humpback whale faecal plumes and control seawater samples to determine the capacity for whales to aid in carbon sequestration in Alaskan waters. While the whale pump has been examined in the North Atlantic and the Southern Oceans, this will be the first study to investigate the whale pump in the North Pacific.
Sea otters are part of a trophic cascade that helps kelp forests to grow. Sea otters keep kelp forests healthy by feeding on organisms that graze on kelp, such as sea urchins. In Southeast Alaska, there has been a rapid increase in sea otter distribution and abundance over the past four decades. While the flourishing sea otter population has likely caused concomitant changes in kelp forests, these have not been quantified. This project will quantify historic changes in surface canopy kelp using satellite imagery. Changes in kelp forest extent will then be related to changes in sea otter distribution to assess the ability of sea otters to contribute towards carbon sequestration in Southeast Alaska.
We wish Heidi all the best with this important research, and look forward to better understanding the role of Fish Carbon as a climate action in the North Pacific.