Meeting Abstract
Silvetia compressa, a canopy-forming alga, plays a vital role in rocky intertidal ecosystems as a primary producer and habitat for animals. Intertidal organisms are under seawater at high tide and exposed to terrestrial conditions at low tide. Stressors such as wind and heat during low tide can negatively affect algal physiology and subsequently biomass and canopy cover. We manipulated hydration level (values down to 17% wet mass) and body temperature (low mean = 22.79oC, high mean = 30.49oC) over two simulated low light low tides, and monitored the effect on biomass and maximum quantum yield (MQY: a measure of photosynthetic potential) over three days of recovery in simulated high tide conditions. At the end of the second low tide, hydration status was positively correlated with MQY in both low (r = 0.92) and high (r = 0.94) temperature treatments. Following 84 hours of recovery, biomass loss was minimal and not strongly associated with low tide temperature or desiccation and negative effects of desiccation on MQY disappeared, but on average, MQY in high temperature treatments was only 91.6% of that in low temperature treatments. Temporary MQY decreases following low tide desiccation indicate a reduced ability to produce sugar which could affect growth. Repeated exposure to warm low tides could slowly lower an individual’s maximum attainable photosynthetic potential. The combination of dry and warm days could ultimately lead to a decrease in canopy cover, exposing understory organisms to harsh low tide conditions with long term effects on community structure and function.
