Physical and chemical characteristics of seawater in two natural
tide pools on Rosario Beach, Fidalgo Island, Washington, were compared
during midday low tides in July 1991. One pool contained a mixed assemblage
of macroalgae (40% cover) and invertebrates (50% cover). The second pool was
dominated (75% cover) by the sea anemone Anthopleura elegantissima (Brandt,
1835), which contains symbiotic algae (zooxanthellae). Temperature, salinity,
dissolved oxygen, and pH levels increased in both pools with irradiance and
length of emersion. The resident organisms caused changes in the inorganic
nutrient levels of the tide-pool seawater. Anthopleura elegantissima released
substantial amounts of ammonium; NH4 + in the anemone-dominated pool
increased by 33% whereas NH4 + declined in the mixed assemblage pool by an
average of 28%. Nitrate and nitrite declined in both pools, whereas phosphate
remained constant during the 6-hr sampling periods. NH4 + release by A.
elegantissima was confirmed in studies of artificial tide pools, where NH4 + levels
increased by an average of 71% over an 8-hr period. Release of ammonium by
A. elegantissima under natural conditions in the field provides a contrast to
nutrient fluxes observed for tropical symbiotic associations
