Veronica Farrugia Drakard1, 2, Jordan Hollarsmith3, Michael Stekoll1
1University of Alaska Fairbanks, USA - 2University of British Columbia, Canada - 3National Oceanic and Atmospheric Administration, USA
Kelp forests worldwide are threatened by climate change and anthropogenic impacts. The impacts of climate-driven glacial melt on the early life-stages of high-latitude kelp species are poorly understood. In this study, we used two separate stressor experiments to investigate the impacts of a reduction in salinity and an increase in sediment load on bull kelp (Nereocystis luetkeana) and ribbon kelp (Alaria marginata). To test the effect of salinity, spores of both species were cultured in four salinity treatments (32 ppt, 25 ppt, 20 ppt, 13 ppt) for 30 days. To test the effect of sediment load, spores of both species were cultured in four sediment treatments (0 g/L, 0.21 g/L, 0.42 g/L, 0.84 g/L). Photographs were taken at initiation, and subsequently every 5 days from spore release. These were used to quantify germination, gametophyte growth and survival, egg production, and sporophyte production. Both species grew and reproduced in salinities down to 20 ppt, although A. marginata was more resilient to hyposaline conditions in general. Below 20 ppt, we observed impacts on reproduction and progression between life-stages. N. luetkeana produced more eggs at salinities below 32 ppt by Day 25, and only began to produce eggs in 32 ppt at Day 30. This suggests that lowering salinities to between 20–25 ppt in the hatchery may induce the production of eggs up to a week earlier than culturing at full oceanic salinity, and could significantly reduce costs in commercial operations. In terms of sediment load, the germination and growth of both species were lower in sediment treatments of 0.42 g/L and above, although once again A. marginata appears to be somewhat resilient both in terms of germination and gametophyte growth. Increased sediment deposition from late fall through early spring, when kelp gametophytes are present on the benthos, may have severe implications for the persistence and survival of wild kelp populations at high latitudes. These results therefore have implications for the aquaculture industry in terms of hatchery techniques and cost-effectiveness, and also for the conservation of wild kelp forests in terms of climate resilience.
Biography
Veronica is a marine ecologist specializing in seaweeds, particularly large habitat-forming species. She has lived and worked in the Mediterranean Sea, the Irish Sea, and the Gulf of Alaska, and is excited to now be pursuing research questions in the Salish Sea. Based at UBC Vancouver within the Martone Lab, she is co-advised by Matt Lemay, Margot Hessing-Lewis, and Patrick Martone.