Octocorals in a changing environment: Seasonal response of stress biomarkers in natural populations of Veretillum cynomorium Carolina Madeira a,b, ⁎ ,1 , Diana Madeira b, ⁎ ,1 , Catarina Vinagre a , Mário Diniz b a MARE — Marine and Environmental Sciences Centre, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal b UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal abstract article info Article history: Received 27 October 2014 Received in revised form 16 June 2015 Accepted 9 July 2015 Available online 17 July 2015 Keywords: Octocorals Seasonality Temperature HSPs Oxidative stress biomarkers Environmental monitoring Current concerns about climate change emphasize the need for an accurate monitoring of physiological condi- tions in wild populations. Therefore, the aims of this work were to a) assess the response of the octocoral Veretillum cynomorium to thermal variation in natural populations during low tide, by quantifying several bio- chemical indicators of thermal and oxidative stress and b) evaluate the effect of seasonality in the results and the adequacy of the use of biochemical indicators of stress in field monitoring studies in octocorals. Sampling took place during spring (April) and summer (June). Heat shock protein (Hsp70) and ubiquitin (Ub) content, en- zyme activities — superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), and lipid perox- idation (LPO) were assessed in rachis and peduncle tissues separately. The results showed significant seasonal fluctuations in the set of biomarkers tested. Differences were detected between spring and summer, with signif- icant decreases in biomarker levels from April to June being a major observed trend. These results suggest that V. cynomorium is thermo-tolerant during summer low tide conditions. Seasonal variation seems to reflect a met- abolic suppression strategy and/or may also be related to seasonal changes in food availability and reproductive status. Differences in activity between tissue types were also found significant for GST, LPO and Ub. Biomarker levels were correlated with total protein concentration, but not with wet body weight of the specimens. This study suggests that season influences the expression of biomarkers and must be taken into consideration in the preliminary stages of sampling design for climate change biomonitoring studies. In addition, the results suggest that this octocoral species is likely to survive in future challenging thermal conditions. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The intertidal habitat is one of the harshest zones for marine biota to inhabit (Menge and Branch, 2001) since organisms are exposed to envi- ronmental conditions with steep gradients (Tomanek and Helmuth, 2002) such as temperature, ultraviolet radiation and salinity that can lead to cellular damage or death. In particular, it is well known that temperature is a key environ- mental factor that affects organisms at all organization levels by control- ling their physiological and ecological processes (Calosi et al., 2008; Hochachka and Somero, 2002). Since organisms tend to have thermal tolerances that reflect the environment in which they are found (Madeira et al., 2012), it is not surprising that recent research has focused on analyzing the thermal responses of marine invertebrates (species and/or populations) to different temperature regimes across varying temporal and spatial scales (Helmuth et al., 2002; Somero, 2005; Oliver and Palumbi, 2011). In addition there have been in the past years extensive studies on the bioenergetic costs of environmental stress and consequent fitness changes in species of all taxonomic groups of marine life (Todgham and Stillman, 2013). Depending on the magni- tude and duration of stress, organisms can redirect their energy reserves toward cellular defense and maintenance of homeostasis at the expense of growth and reproduction (Philippart et al., 2003; Todgham and Stillman, 2013; Sanford, 2002). Among the most affected organisms are sessile invertebrate species, which play important roles in the structure and function of their habi- tats. Thermo-tolerance in these organisms is likely to be settled by the adjustment of the oxygen demand which influences the metabolic ac- tivities and energy-demanding processes in cells (Clarke, 2003; Hadas et al., 2008). Pörtner (2010) hypothesized this as OLTT (Oxygen Limited Thermal Tolerance): at both upper and lower pejus temperatures, the limiting capacity for oxygen supply causes hypoxemia resulting in per- formance decrements. Corals are one of these habitat structuring sessile invertebrate groups. Besides being important constituents of coral reef ecosystems (Sánchez et al., 2003) they also play additional roles in benthic ecosys- tems such as generating sediments (Weinbauer and Velimirov, 1995), and providing habitat for fishes and other invertebrates (Yesson et al., 2012). Octocorallia are the most diverse group of corals, with over Journal of Sea Research 103 (2015) 120–128 ⁎ Corresponding authors. E-mail addresses: scmadeira@fc.ul.pt (C. Madeira), dianabmar@gmail.com (D. Madeira). 1 Madeira C and Madeira D contributed equally to this work. http://dx.doi.org/10.1016/j.seares.2015.07.008 1385-1101/© 2015 Elsevier B.V. All rights reserved. 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