, 2011). Reduced protein synthesis ( Langenbuch et al., 2006), inferred muscle wastage ( Wood et al., 2008), reduced growth rates ( Berge et al., 2006) and immunosuppression ( Hernroth selleck inhibitor et al., 2011) have all been documented as responses to seawater acidification for marine invertebrates. Hypercapnia is known to suppress metabolism in several species (e.g. Widdicombe and Spicer, 2008) and causes lethargy in the ophiuroid Ophinoereis schayeri at pH 7.8 ( Christensen et al., 2011), which may lead to reductions in activity levels and impair the performance of routine behaviour. At lower pH levels (pH 7.6–7.4), however, compensatory mechanisms

appear to be activated in O. schayeri as oxygen uptake increases

coinciding with copious secretion of mucous, a known stress response. Oxygen consumption is also up-regulated under acidified BKM120 in vitro conditions in A. filiformis ( Wood et al., 2008) and in the arctic ophiuroid Ophiocten sericeum ( Wood et al., 2011), suggesting that individuals attempt to maintain normal levels of activity. Whilst the observed onset of emergent behaviour most likely reflects a response to hypercapnic conditions rather than other known causes of stress, such as hypoxia (Rosenberg et al., 1991), behavioural changes in response to the onset of acidification do occur rapidly and evidence is emerging that altered behaviour may modify organism-sediment and community interactions (Briffa et al., 2012). In the present study, it is clear that individuals of A. filiformis moved to shallower depths within the sediment profile under acidified conditions and that the variability in the depth of occupancy reduced relative to ambient conditions, yet these changes in behaviour were insufficient to cause demonstrable effects on functioning. Whilst it is possible that we may not have detected a strong affect because

the response behaviour of A. filiformis forms an extension of normal behaviour ( Solan and Kennedy, 2002 and O’Reilly et al., 2006), we interpret our findings to be a reflection of the short duration of our experiment. Edoxaban If this is the case, the observed changes to species behaviour could be extremely important over longer timescales because they are likely to lead to secondary effects, such as increased ( Bibby et al., 2007) or decreased ( Dixson et al., 2010) predator evasion, reduced responses to olfactory cues ( Cripps et al., 2011) and decreased locomotion ( de la Haye et al., 2011), all of which affect post-acidification survival and/or the contribution that individual species make to ecosystem functioning over the longer term ( Bulling et al., 2010). Where sub-lethal predation of A.