CO₂-induced ocean acidification increases anxiety in Rockfish via alteration of GABA_Areceptor functioning

Abstract

The average surface pH of the ocean is dropping at a rapid rate due to the dissolution of anthropogenic CO 2 , raising concerns for marine life. Additionally, some coastal areas periodically experience upwelling of CO 2 -enriched water with reduced pH. Previous research has demonstrated ocean acidification (OA)-induced changes in behavioural and sensory systems including olfaction, which is due to altered function of neural gamma-aminobutyric acid type A (GABA A ) receptors. Here, we used a camera-based tracking software system to examine whether OA-dependent changes in GABA A receptors affect anxiety in juvenile Californian rockfish (Sebastes diploproa). Anxiety was estimated using behavioural tests that measure light/dark preference (scototaxis) and proximity to an object. After one week in OA conditions projected for the next century in the California shore (1125 + 100 matm, pH 7.75), anxiety was significantly increased relative to controls (483 + 40 matm CO 2 , pH 8.1). The GABA A -receptor agonist muscimol, but not the antagonist gabazine, caused a significant increase in anxiety consistent with altered Cl 2 flux in OA-exposed fish. OA-exposed fish remained more anxious even after 7 days back in control seawater; however, they resumed their normal behaviour by day 12. These results show that OA could severely alter rockfish behaviour; however, this effect is reversible.

Ocean acidification alters the response of intertidal snails to a key sea star predator

“…These combined results suggest that behavioural impairment under OA may be at least somewhat general across taxa [8,12]. The physiological mechanisms underlying OA-induced behavioural shifts in fish appear to revolve around degraded function of ion channels that involve the neurotransmitter gamma-aminobutyric acid (GABA; [7][8][9]), and it may be relevant that GABA receptor molecules are conserved across vertebrates and invertebrates [8].…”

“…Multiple species of fish, for example, fail to properly process waterborne cue information when confronted with the scent of predators [5,6]. Such impaired behaviours appear to originate from altered neurotransmitter and ion channel function under conditions of reduced seawater pH [7][8][9]. Fewer studies have explored the potential for analogous effects in invertebrates, although limited evidence suggests that perturbed neuronal function under OA may arise quite generally [10][11][12][13][14].…”

Effects of ocean acidification on the larvae of a high-value pelagic fisheries species, mahi-mahi Coryphaena hippurus

“…The range of effects include reduced growth and survival (Baumann et al 2011), skeletal deformation (Pimentel et al 2014a), altered neurological function (Nilsson et al 2012), and disrupted behavior (Munday et al 2010, Ferrari et al 2012, Hamilton et al 2014. Some species have experienced more discrete effects, such as altered otolith (ear stone) development (Checkley et al 2009, Munday et al 2011a, Hurst et al 2012, Bignami et al 2013a) and impaired tissue health (Frommel et al 2011).…”

Environmental pH, O2 and Capsular Effects on the Geochemical Composition of Statoliths of Embryonic Squid Doryteuthis opalescens

“…Average pH and [O 2 ] conditions can be further decreased in southern California during La Niña years as the thermocline shoals [1]. Early life stages of non-calcifying metazoans exposed to high levels of pCO 2 and associated low pH (e.g., acidification; [9][10][11]) are affected in several ways, including altered developmental, physiological and behavioral processes [12][13][14][15]. For cuttlefish and squid embryos, acidified environmental conditions generate additive effects, increasing an already acidified perivitelline fluid that baths embryos within the egg (cuttlefish) [16,17] and chorion (squid) [18,19].…”