Tidepools in Dead Man’s Cove show large fluctuations in carbonate chemistry during the low tide in comparison to Haro Stait water

Abstract

During the low tide, tidepools are under different physio-chemical conditions than the coastal waters. This includes the carbonate chemistry, which is especially pertinent to study due to the threat of ocean acidification on carbonate chemistry. We examined the fluctuation in DIC, total alkalinity, pH, temperature, dissolved oxygen, and salinity in two tide pools in Dead Man’s Cove, San Juan Island, WA over the course of the low tide. To better understand the relative contributions of photosynthesizers and respirers to changes in carbonate chemistry, we added Ulva to one pool on the second day, and Mytilus trossulus on the third day. During the low tide, tidepools saw a decrease in DIC and alkalinity, and an increase in pH, temperature, and dissolved oxygen. There is evidence of a small signal of decrease in DIC due to Ulva addition and increased DIC due to Mytilus addition. Tidepools experience huge swings in carbonate chemistry that suggests an ability of the organisms that inhabit the pools to cope with large changes in pH over the course of the day.