Water on the rise: Bull Kelp Gametophyte survival in rising temperatures

Abstract

As anthropogenic climate change progresses, increasing seawater temperatures play a large role in shaping changes in the range of benthic species. Predominate cold temperate kelp species are such an impacted organism; they grow at temperature below 18°C and are now seeing a decrease in available habit as they are threatened by increasing water temperature. Nereocystis luetkeana, a kelp with a floating canopy in the sporophyte phase is found in the eastern Pacific Ocean from central California to the Aleutian Islands (Druehl 1969). As in all kelp species, it has a heteromorphic life history, which leaves two phases susceptible to increasing water temperatures. In this study N. luetkeana zoospores were grown in culture to determine how the young gametophyte phase reacted to elevated temperatures. To determine the upper temperature range of gametophytes, three temperature treatments were used to cultivate N. luetkeana zoospores found in the San Juan Islands, WA. A significant decrease in the number of gametophytes and their length were observed at temperatures exceeding 15°C. These findings indicate that the decrease in bull kelp beds could be highly correlated to the increase in temperature of the intertidal.