Otters, sea stars, and glacial melt: top-down and bottom-up factors that influence kelp communities

• Main Author: Traiger, Sarah B.
• Other Authors: Konar, Brenda, Hardy, Sarah, Okkonen, Stephen, Edwards, Matthew, Litaker, Wayne
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2017
• Subjects: Kelps; Habitat; Alaska; Kelp bed ecology; Fairbanks; glaciers
• Online Access: http://hdl.handle.net/11122/7903

Dissertation (Ph.D.) University of Alaska Fairbanks, 2017 Kelp beds are important features of the Alaska coastline and provide habitat, protect coastlines, and support commercial and subsistence harvests. Kelp beds are affected by top-down and bottom-up factors, which are changing due to human and climate-related impacts. The influences of these top-down and bottom-up factors on kelp beds are investigated in three chapters. My first chapter investigated the influence of glacial discharge on recruitment and early community development in subtidal kelp communities by monitoring benthic sessile algae and invertebrates on cleared rocks across a glacial gradient along with various physical and biological parameters in the summers of 2013-2014. It has been predicted that Alaska's glaciers will lose 30-60% of their volume by 2100. The melt from glaciers increases sedimentation and lowers salinity, impacting important habitat-providing kelp. I found that sites upstream from glacial discharge had higher kelp recruitment than downstream sites, and that up to 72% of the variation in community development was related to mobile invertebrates and kelp in the surrounding community. Glacially-influenced environmental factors did not explain any variation that was not already explained by biological factors. My second chapter explored whether patterns in the recruitment of the dominant canopy kelp, Nereocystis luetkeana and the subcanopy kelp, Saccharina latissima were a result of dispersal limitation or failure to grow to macroscopic size. My goals were to determine 1) whether glacial melt conditions affect adult fecundity (spore production) of either species, 2) how sedimentation affects early gametophyte growth and survival in each species, and 3) whether competitive interaction between species at the gametophyte stage is altered by sediments. I found that glacial melt conditions did not affect the fecundity of either species, but sedimentation affected survival and competition. Saccharina latissima was the superior ...