Response of kelps from different latitudes to consecutive heat shock

Pereira, Tania R.; Engelen, Aschwin H.; Pearson, Gareth; Valero, Myriam; Serrao, Ester A.

http://hdl.handle.net/10400.1/11281

Use this identifier to reference this record.

Name:	Description:	Size:	Format:
H11281.pdf		1.05 MB	Adobe PDF	Download

Send Feedback

Authors

Abstract(s)

Although extensive work has focused on kelp responses to constant temperature, little is known about their response to the consecutive temperature shocks they are often exposed to in the shallow subtidal and intertidal pools. Here we characterized the responses of the two southernmost forest-forming kelp species in the Northeast Atlantic, Laminaria ochroleuca De La Pylaie and Saccorhiza polyschides (Lightf.) Batt. to multiple cycles of thermal stress. Individuals from the upper vertical limit of the geographical distribution edges where the two species co-occur forming forests, France and Portugal, were exposed to 4 consecutive cycles of thermal shock simulating a spring tide. A 24 h cycle consisted of culture at 15 degrees C, plus 1 h heat shock at one of five levels (20, 22.5, 25, 27.5 or 30 degrees C). The maximum quantum yield (Fv/Fm) of chlorophyll fluorescence of photosystem 2 (PS2) was used to detect impaired reaction center function, as a proxy for individual fitness costs, during recovery from heat shock. Both species showed resilience to temperatures from 20 to 25 degrees C. While exposure to 27.5 degrees C caused no inhibition to Fv/Fm of S. polyschides, a threshold was met above this temperature and exposure to 30 degrees C caused the death of all individuals. In contrast, L ochroleuca from France was damaged but able to survive 30 degrees C shocks and individuals from Portugal showed complete resilience to this treatment. In both species, blade elongation decreased with increasing temperature, with necrosis surpassing growth at higher temperatures. Resilience to high temperature exposure may confer an advantage to L ochroleuca to colonize intertidal pools on the Portuguese coast, in agreement with the observation that both species recruit in tide pools but only L ochroleuca reach adulthood. Our results indicate that as summer temperatures increase with climate change, the disappearance of S. polyschides from intertidal pools and a decrease in the density of L ochroleuca can be expected. (C) 2014 Elsevier B.V. All rights reserved.

Keywords

Climate-change Laminaria-Ochroleuca Young Sporophytes Saccorhiza-Polyschides Temperature tolerance Life-histories Brown seaweeds North-sea Phaeophyta Gradient