The effect of ocean warming on black sea bass (Centropristis striata) aerobic scope and hypoxia tolerance

Abstract

46Over the last decade, ocean temperature in the U.S. Northeast Continental Shelf (U.S. NES) has 47 warmed faster than the global average and is associated with observed distribution changes of the 48 northern stock of black sea bass (Centropristis striata). Mechanistic models based on 49 physiological responses to environmental conditions can improve future habitat suitability 50 projections. We measured maximum, resting metabolic rate, and hypoxia tolerance (S crit ) of the 51 northern adult black sea bass stock to assess performance across the known temperature range of 52 the species. A subset of individuals was held at 30˚C for one month (30 chronic°C ) prior to 53 experiments to test acclimation potential. Absolute aerobic scope (maximum -resting metabolic 54 rate) reached a maximum of 367.21 mgO 2 kg -1 hr -1 at 24.4°C while S crit continued to increase in 55 proportion to resting metabolic rate up to 30°C. The 30 chronic°C group had a significant decrease 56 in maximum metabolic rate and absolute aerobic scope but resting metabolic rate or S crit were not 57 affected. This suggests a decline in performance of oxygen demand processes (e.g. muscle 58 contraction) beyond 24°C despite maintenance of oxygen supply. The Metabolic Index, 59 calculated from S crit as an estimate of potential aerobic scope, closely matched the measured 60 factorial aerobic scope (maximum / resting metabolic rate) and declined with increasing 61 temperature to a minimum below 3. This may represent a critical value for the species. 62Temperature in the U.S. NES is projected to increase above 24°C in the southern portion of the 63 northern stock's range. Therefore, these black sea bass will likely continue to shift north as the 64 ocean continues to warm. 65 66 67 likely continue to expand northward as the U.S. NES continues to warm. 132 133 Materials and Methods 134 135

Breathing new life into the critical oxygen partial pressure (Pcrit): a new definition, interpretation and method of determination

“…For Atlantic Spiny Dogfish and Black Seabass, Pcrit-a matched Pcrit determined using the LLO method(Reemeyer and Rees, 2019) across a range of temperatures and a increased with temperature in proportion toMMR (Fig. 6;Slesinger et al, 2019; Andres et al, in prep).…”

“…To assess intraspecific variability and to ensure that our analysis was not biased by the use of idealized representative curves from the literature, we also analyzed several existing respirometry datasets-Euphausia mucronata, a midwater krill from the Eastern Tropical Pacific oxygen minimum zone (OMZ; Welsh and Seibel, unpublished), Farfantepenaeus duorarum, an estuarine pink shrimp (Burns et al, unpublished), the Atlantic Spiny Dogfish, Squalus acanthias (Andres et al, submitted), two oceanic squids, Illex illecebrosus and Sthenoteuthis oualaniensis (Birk, unpublished), and the Black Seabass, Centripristis striata (Slesinger et al, 2019), a coastal fish species. The mean values of a and Pcrit-a and Pcrit (LLO or breakpoint method) for these species are shown in Table 2.…”

“…), squids (Birk and Seibel, unpubl. ) and fishes (Slesinger et al, 2019;Andres et al, submitted). We tested inter-individual and temperature-related variances in a as well as the effect of duration bin size when calculating MO2.…”

“…No significant differences were found among values obtained using 10 to 20 min bin sizes. Trials were ~12 h duration and oxygen was recorded every 30 s. D) Black Seabass (Centropristis striata, Slesinger et al, 2019): Oxygen supply capacity (a) increases with temperature in proportion to maximum (MMR), rather than standard (SMR) metabolic rate. B)…”

Measuring maximum oxygen uptake with an incremental swimming test and by chasing rainbow trout to exhaustion inside a respirometry chamber yields the same results

“…In addition, by comparing the novel data for Ṁ O 2chase with a previously published estimate of Ṁ O 2max (peak Ṁ O 2active ) for the same fish swum to fatigue in a swim tunnel (Zhang et al ., 2019), this study also tested the hypothesis that estimates of Ṁ O 2max can be independent of the testing protocol provided a reliable analytical approach for determining peak Ṁ O 2 was used. Thus, beyond advancing the best practices for reliably estimating Ṁ O 2max by accounting for Ṁ O 2 dynamics, this study contributes to the 24‐year deliberation (Reidy et al ., 1995) that is still ongoing (Hvas & Oppedal, 2019; Killen et al ., 2017; Roche et al ., 2013; Rummer et al ., 2016; Slesinger et al ., 2019; Sylvestre et al ., 2007) about the best approach to estimate Ṁ O 2max in fish.…”