Individual and combined effects of low dissolved oxygen and low pH on survival of early stage larval blue crabs, Callinectes sapidus

Abstract

A large number of coastal ecosystems globally are subjected to concurrent hypoxic and acidified conditions that will likely intensify and expand with continued climate change. In temperate regions, the spawning of many important organisms including the Atlantic blue crab Callinectes sapidus occurs during the summer months when the severity of coastal hypoxia and acidification is the greatest. While the blue crab earliest larval stage can be exposed to co-occurring hypoxia and acidification observed in many coastal ecosystems, the effects of these concurrent stressors on larval blue crab survival is unknown. This study investigated the individual and combined consequences of low dissolved oxygen (DO) and low pH on blue crab larvae survival through a series of short-term experiments. During 14-day experiments with moderately hypoxic conditions (117–127 μM O2 or 3.74–4.06 mg L-1) and acidified conditions (pH on total scale of 7.16–7.33), low DO and low pH individually and significantly reduced larval survival by 60% and 49%, respectively, with the combination of stressors reducing survival by 87% compared to the control treatment (210–269 μM O2 or 6.72–8.61 mg L-1, 7.91–7.94 DO and pH, respectively). During 4-day experiments with lower DO levels (68–83 μM O2 or 2.18–2.62 mg L-1) and comparable pH levels of 7.29–7.39, low DO individually reduced survival by >90% compared to the control (261–267 μM O2 or 8.35–8.54 mg L-1, 7.92–7.97 DO and pH, respectively), whereas low pH had no effect and there was no interaction between stressors. Over a 4-day period, the DO threshold at which 50% of the larval blue crab population died (LC50) was 121 μM O2 (3.86 mgL-1). In 14-day experiments, the DO and pH effects were additive, yielding survival rates lower than the individual treatments, and significantly correlated with DO and pH concentrations. Collectively, these findings indicate that blue crab sensitivity to both low DO and low pH are acute within the larval stage, depend on the intensity and duration of exposure, and leads to mortality, thereby potentially contributing to the interannual variability and possible regional declines of this fishery.

Ocean acidification and hypoxia alter organic carbon fluxes in marine soft sediments

“…Under hypoxia, the oxygen required by marine organisms to support energetically costly processes, such as feeding, assimilation and digestion of food, is not met by ambient oxygen supply. This means that also animals more tolerant to OA could be negatively affected by elevated CO 2 when concurrently exposed to hypoxia (Miller, Breitburg, Burrell, & Keppel, ; Portner, Langenbuch, & Michaelidis, ; Tomasetti, Morrell, Merlo, & Gobler, ). This suggests that in well‐mixed shelf coastal systems, as simulated in our study, even short‐term hypoxic events may compromise the ability of marine invertebrates to deal with future ocean conditions.…”

“…metabolic depression; Pörtner, Langenbuch, & Reipschläger, ; Rosa & Seibel, ). This could result in reduced growth rates and altered behaviour (Galic et al, ; Gobler et al, ; Tomasetti et al, ). Thus, hypoxia and elevated CO 2 , in combination, may impair the key role of infaunal assemblages in determining carbon fluxes at the sediment–water interface and their contribution towards carbon sequestration (Queirós et al, ).…”

Timescales and Magnitude of Water Quality Change in Three Texas Estuaries Induced by Passage of Hurricane Harvey

“…Die-off's of both benthos and nekton have also been observed in response to storm-driven hypoxia/anoxia in the environment (Mallin et al 1999;Paerl et al 2001), while laboratory studies have shown that the combination of low D.O. and low pH negatively affects the health of a broad range of marine life (e.g., Gobler et al 2014;Gobler and Baumann 2016;Tomasetti et al 2018). In the case of Harvey, benthic biomass, abundance, and diversity declined and minor shifts 1.0 ± 0.8 25 1.1 ± 0.7 10 0.829 NO x (μmol L −1 )…”

Brief Episodes of Nocturnal Hypoxia and Acidification Reduce Survival of Economically Important Blue Crab (Callinectes sapidus) Larvae

“…Juvenile and adult animals both exhibit steady or increased calcification and growth under acidified conditions (Ries et al, 2009;Whiteley, 2011;Glandon and Miller, 2017) and are also considered moderately tolerant of hypoxia (deFur et al, 1990;Burnett, 1997;Mangum, 1997). Recent experiments with larvae, however, reveal sensitivities of early life stages to ocean acidification (Giltz and Taylor, 2017) and coastal hypoxia and acidification both individually and in combination (Tomasetti et al, 2018), further evidencing that crustacean tolerance to low DO-and/or low pH-stress varies throughout ontogeny often in association with changes in respiratory physiology (Whiteley, 2011;Alter et al, 2015;Leiva et al, 2018;Gravinese, 2020).…”

“…In temperate systems, the C. sapidus larval release coincides with the time of year when coastal hypoxia/acidification is the most persistent and severe (Dittel R and Epifanio, 1982;McConaugha et al, 1983;Breitburg, 1990;Wallace et al, 2014). Among crustaceans, the pelagic larval life stage is considered the most sensitive to low DO (Miller et al, 2002), particularly for C. sapidus, for which the 50% lethal DO threshold (LC 50 ) is higher than the majority of values published for other larval crustacean species (Miller et al, 2002;Tomasetti et al, 2018). Predictably, low DO effects on C. sapidus are most acute in the larval stage, as crustacean sensitivities to hypoxia depend on their respiratory anatomy and habitat characteristics (Alter et al, 2015).…”