Macroalgae distribution among varying glacial fjords as an indicator of light and nutrient availability

• Main Author: Reimer, Jillian
• Other Authors: Papakyriakou, Tim (Environment and Geography), Sejr, Mikael (Aarhus University), Mundy, CJ
• Language: English
• Published: 2024
• Subjects: Oceanography; Kelp; Macroalgae; Climate change; Ecology; Arctic; greenlandic; Sea ice
• Online Access: http://hdl.handle.net/1993/38182

Arctic macroalgae (kelp) are critical primary producers, contributing significantly to a wide variety of ecosystem services. Kelp extent has been predicted to increase due to decreasing sea ice cover that increases light reaching the coastal ocean. However, climate change-induced factors, such as increasing coastal turbidity and glacier melt, could also impact kelp growth in the Arctic. This thesis examines the role that light and nutrient availability play in understanding kelp cover and depth extent. This study used GoPro videos to determine kelp cover and depth extent as well as macroalgae samples to determine the nutritive state of kelp within two Greenlandic fjords. Results reveal significant turbidity and nutrient gradients throughout the fjords. Where light was limited due to glacial discharge and resuspension of sediments, kelp growth at depth was limited; and where there was increased light availability, kelp cover was greater. Additionally, kelp located nearest the marine-terminating glacier had greater nitrogen concentration than kelp located further from the marine-terminating glacier or the land-terminating glacier, revealing the influence of estuarine circulation on nutrient availability. Where light and nutrients were abundant, kelp biomass and subsequent production was greatest. Additionally, we concluded that sea urchin grazing provided an additional influence with light on kelp depth extent and distribution in both shallow and deep waters. These results are necessary and important to consider when assessing kelp distribution and change, both now and into the future. May 2024