Sea urchins in a high-CO ₂ world: the influence of acclimation on the immune response to ocean warming and acidification

Abstract

Climate-induced ocean warming and acidification may render marine organisms more vulnerable to infectious diseases. We investigated the effects of warming and acidification on the immune response of the sea urchin Heliocidaris erythrogramma Sea urchins were gradually introduced to four combinations of temperature and pHNIST (17°C/pH 8.15, 17°C/pH 7.6, 23°C/pH 8.15 and 23°C/pH 7.6) and then held in temperature-pH treatments for 1, 15 or 30 days to determine if the immune response would adjust to stressors over time. Coelomocyte concentration and type, phagocytic capacity and bactericidal activity were measured on day 1, 15 and 30 with different sea urchins used each time. At each time point, the coelomic fluid of individuals exposed to increased temperature and acidification had the lowest coelomocyte concentrations, exhibited lower phagocytic capacities and was least effective at inhibiting bacterial growth of the pathogen Vibrio anguillarum Over time, increased temperature alleviated the negative effects of acidification on phagocytic activity. Our results demonstrate the importance of incorporating acclimation time to multiple stressors when assessing potential responses to future ocean conditions and indicate that the immune response of H. erythrogramma may be compromised under near-future ocean warming and acidification.

Effects of long-term elevated temperature on covering, sheltering and righting behaviors of the sea urchinStrongylocentrotus intermedius

“…Consistent with theoretical predictions (Poloczanska et al, 2007), empirical studies indicate that elevated water temperature negatively affects physiology (Uthicke et al, 2014), immunity (Brothers et al, 2016), growth (Wolfe, Dworjanyn & Byrne, 2013; Zhao et al, 2015), gonad development (Uthicke et al, 2014), larval development (Kamya et al, 2014; Garcia, Clemente & Hernandez, 2015) and behaviors (Zhao et al, 2014; Brothers & McClintock, 2015; Sherman, 2015) of echinoderms in intertidal and shallow waters. However, most of these reports were based on short-term perturbation experiments and do not provide enough time to bring about potential acclimation to a new environment (Dupont et al, 2013).…”

Ocean warming alters predicted microbiome functionality in a common sea urchin

“…As sea urchins experience stress associated with ocean warming host immunity may also become compromised. In the sea urchin Heliocidaris erythrogramma, elevated seawater temperatures (þ68C) decreased coelomocyte concentrations and significantly affected the types of coelomocytes comprising the coelomic fluid [38].…”

Marine Host-Pathogen Dynamics: Influences of Global Climate Change

“…Infection rates for bald sea urchin disease in both tank experiments and multiple real-world mass mortality events are strongly correlated with increases in temperature (Scheibling and Stephenson, 1984;Ward and Lafferty, 2004;Girard et al, 2012;Brothers et al, 2016;Sweet et al, 2016). At higher temperatures, urchins experience thermal stress, which initially triggers a heightened immune response (Brothers et al, 2016). Despite these immunological responses, increased infection rates often occur when elevated temperatures persist or are more extreme.…”

“…Furthermore, urchins often exhibit decreased activity and feeding during extreme heat events, as well as decreased fecundity, which can restrict recovery of individuals and populations (Farmanfarmaian and Giese, 1963;Lester et al, 2007). While negatively impacting the urchins, these extreme heat events appear to favor the pathogens, increasing growth and transmission rates, as well as improving bacterial survivorship (Brothers et al, 2016;Sweet et al, 2016). The longer the urchins remain in a state of stress, the higher their susceptibility to disease (Brothers et al, 2016;Sweet et al, 2016).…”

“…While negatively impacting the urchins, these extreme heat events appear to favor the pathogens, increasing growth and transmission rates, as well as improving bacterial survivorship (Brothers et al, 2016;Sweet et al, 2016). The longer the urchins remain in a state of stress, the higher their susceptibility to disease (Brothers et al, 2016;Sweet et al, 2016). Though recovery is possible, urchin species impacted by a bald sea urchin disease event tend to exhibit increased mortality in persistently elevated seawater temperatures (Lester et al, 2007;Girard et al, 2012;Brothers et al, 2016).…”