Bleaching of an intertidal coralline alga: untangling the effects of light, temperature, and desiccation

Abstract

Intertidal macroalgae must tolerate temperature, light, and desiccation stresses when the tide recedes, and differences in physiological tolerance to these environmental stresses contribute directly to zonation patterns and community structure along the shore. When low tides occur on particularly hot sunny days, seaweeds may sustain physiological damage, lose pigment, and 'bleach.' Because bleaching events often occur when temperature, light, and desiccation stresses coincide, their precise cause is not understood. We conducted fully factorial laboratory manipulations to explore the individual and interactive effects of temperature, light, and desiccation on acute pigment loss in the intertidal coralline Calliarthron tuberculosum (Postels & Ruprecht) E. Y. Dawson. Findings suggest that desiccation is the most significant contributor to bleaching; desiccating fronds even bleached in the dark at 15°C. Susceptibility to desiccation may explain why mid-intertidal C. tuberculosum fronds are rarely found outside tidepools. Light and temperature had only marginal effects on pigment loss, although stresses interacted with increasing significance through time. When combined, temperature, light, and desiccation stresses were capable of inducing, on average, 50% pigment loss in C. tuberculosum within 24 min of emersion. These physiological data could be used in conjunction with environmental datasets to generate 'ecomechanical' models to predict future bleaching events and their ecological consequences under hypothetical climate change scenarios.

Physiological performance of intertidal coralline algae during a simulated tidal cycle

“…This supports the results of Martone et al. (), who found that desiccation was the primary environmental stress that limited the habitat range of intertidal Calliarthron . It is likely that intertidal Calliarthron is relegated to tidepools to avoid desiccation.…”

“…Calliarthron , on the other hand, is abundant subtidally (Konar and Foster ) suggesting that it is well‐adapted to low light, cooler water temperatures, and is highly susceptible to desiccation (Padilla , Martone et al. ), although it can be found in some intertidal tidepools.…”

Seaweed Responses to Temperature

“…Also, freezing is an important stress for polar and cold-temperate intertidal algal communities (Pearson et al 2000). Tolerance ranges (i.e., the range between upper and lower lethal temperatures) have been found to be broader in intertidal seaweeds occupying the upper shore than in species from the subtidal (Einav et al 1995;Stengel and Dring 1997;Martone et al 2010). Short-term thermal stress on the organism level seems ecologically less relevant for seaweeds growing in the subtidal where algae are virtually always submerged.…”

Reference genes for transcript quantification in Gracilaria tenuistipitata under drought stress

“…As this species is generally found in intertidal brackish ponds (McLachlan and Bird 1986;Wang et al 2014), which is a very unstable environment susceptible to salt, temperature, and tidal oscillations (Abe et al 2001;Ji and Tanaka 2002;Shafer et al 2007;Martone et al 2010), even a mild drought tolerance is advantageous. G. tenuistipitata is more drought-tolerant than other species in the genus, such as G. corticata (Kumar et al 2011) and G. tikvahiae (Hodgson 1984), but not as tolerant compared The efficiency was measured as the quantity of good RNA extract per milligram of fresh tissue per time that each method lasted.…”