Impact of near-future ocean acidification on echinoderms

Abstract

As a consequence of increasing atmospheric CO(2), the world's oceans are warming and slowly becoming more acidic (ocean acidification, OA) and profound changes in marine ecosystems are certain. Calcification is one of the primary targets for studies of the impact of CO(2)-driven climate change in the oceans and one of the key marine groups most likely to be impacted by predicted climate change events are the echinoderms. Echinoderms are a vital component of the marine environment with representatives in virtually every ecosystem, where they are often keystone ecosystem engineers. This paper reviews and analyses what is known about the impact of near-future ocean acidification on echinoderms. A global analysis of the literature reveals that echinoderms are surprisingly robust to OA and that important differences in sensitivity to OA are observed between populations and species. However, this is modulated by parameters such as (1) exposure time with rare longer term experiments revealing negative impacts that are hidden in short or midterm ones; (2) bottlenecks in physiological processes and life-cycle such as stage-specific developmental phenomena that may drive the whole species responses; (3) ecological feedback transforming small scale sub lethal effects into important negative effects on fitness. We hypothesize that populations/species naturally exposed to variable environmental pH conditions may be pre-adapted to future OA highlighting the importance to understand and monitor environmental variations in order to be able to to predict sensitivity to future climate changes. More stress ecology research is needed at the frontier between ecotoxicology and ecology, going beyond standardized tests using model species in order to address multiple water quality factors (e.g. pH, temperature, toxicants) and organism health. However, available data allow us to conclude that near-future OA will have negative impact on echinoderm taxa with likely significant consequences at the ecosystem level.

Effects of ocean acidification on immune responses of the Pacific oyster Crassostrea gigas

“…Moreover, OA stress has also been found to affect many physiological processes, such as calcification [13], energy metabolism [14] and behavior [15,16] of calcifying organisms. However, there is a lack of studies on the effects of OA on other vital processes of marine organisms such as immune and stress responses [17]. To date, only few studies have investigated the impacts of OA stress on immune systems in bivalve, echinoderm and crustacean [18e21], which have highlighted the potential negative effect of reduced seawater pH on the host defense responses of marine invertebrates.…”

Recent advances in understanding trans-epithelial acid-base regulation and excretion mechanisms in cephalopods

“…46 The increased hydration of CO 2 changes seawater chemistry, causing a drop in ocean pH. While some marine species have been identified as rather sensitive (e.g., less active calcifying species such as corals or echinoderms) 30,47,48 others, mostly active species such as adult fish, crustaceans and cephalopods can tolerate high CO 2 concentrations over long exposure times. 49,50 A major hypothesis that had to be tested was, if the ability to compensate for a hypercapnia -induced acidosis by actively accumulating bicarbonate and eliminating protons from their body fluids is a general, unifying feature of tolerant organisms.…”

Temperature modulates the response of the thermophilous sea urchin Arbacia lixula early life stages to CO2-driven acidification

“…In the majority of tested species (9 out of 13), ocean acidification had no effect on larval survival (see Dupont and Thorndyke, 2013 for review). In the other 4 species, the impact was an increased mortality (Arachnoides placenta, Gonzalez-Bernat et al, 2012; Odontaster validus, Gonzalez-Bernat et al, 2013; Patiriella regularis, Byrne et al, 2013) with a 100% mortality within 7 days observed in the brittlestar Ophiothrix fragilis (Dupont et al, 2008).…”

“…Dupont et al, 2010a;Byrne, 2011;Dupont and Thorndyke, 2013). Temperature impacts metabolisms and modulates performance (Byrne, 2011).…”

“…Direct impacts of ocean acidification on sea urchins are mostly negative but sub-lethal. These include slower somatic and gonadal growth and reflect a shift in energy budgets linked to additional costs for extracellular pH (pHe) and intracellular pH (pHi) regulations rather than direct impact on calcification (Dupont and Thorndyke, 2013). However, interaction between temperature and ocean acidification was only considered in a limited number of studies (Sheppard Brennand et al, 2010;Byrne et al, 2009Byrne et al, , 2010a2011;Caldwell et al, 2011;Catarino et al, 2012a;Ericson et al, 2012;Foo et al, 2012).…”