502
dilutions of <10 μg/L∑50PAH (Stieglitz et al. 2016). This study reported reduced
maximal oxygen uptake, reduced aerobic scope, and a concomitant reduction in
critical swimming speed (U crit ) with no apparent effect on gill histology after only
24 hrs of exposure in young adult mahi-mahi. Subsequent studies employing vascular blood flow probes inserted into anesthetized mahi-mahi revealed normal heart
rate but greatly reduced stroke volume and thereby reduced cardiac output when
exposed for 24 hrs to HEWAF at ~ 10 μg/L∑50PAH prior to experimentation
(Nelson et al. 2016). Similar exposures resulted in reduced U crit for cobia
(Rachycentron canadum) and a substantial reduction in stroke volume, although the
later was largely compensated for by an elevated heart rate (Nelson et al. 2017).
Further studies on cobia employing 24-h HEWAF exposures at ~ 22 μg/L∑50PAH
found reduced cardiac power output (Cox et al. 2017), although this effect could be
mitigated by β-adrenergic stimulation alluding to possible compensations in intact
animals. In addition to the cardiac impacts noted above for pelagic GoM species,
the coastal red drum show reduced aerobic scope and U crit following 24 hrs of acute
exposure to HEWAF at 12 μg/L∑50PAH. These impairments remained for 8 weeks
after the 24-hr exposure attesting to the persistence of cardiac effects induced by oil
exposure to adult GoM species (Johanson and Esbaugh 2017).
Interestingly, reduced swim performance has been observed in oil-exposed GoM
species without a concomitant reduction on maximal oxygen uptake or aerobic
scope. For red drum, a 24-h exposure to HEWAF at 4 μg/L∑50PAH resulted in both
reduced burst swimming speed (U burst ) and U crit without any apparent reductions in
aerobic scope (Johanson and Esbaugh 2017). Similarly, 48-hr HEWAF exposures to
mahi-mahi embryos at 1.2 μg/L∑50PAH followed by rearing in uncontaminated
water for 30 days resulted in reduced U crit , again without reductions in aerobic scope
or maximal oxygen uptake (Mager et al. 2014). The observed effects on swim performance in absence of notable reductions on oxygen supply points to nonrespiratory pathways for PAH impacts on swim performance. Three such possible
nonexclusive pathways include (1) impaired neuromast function leading to reduced
swimming efficiency (Johanson and Esbaugh 2017), (2) reduced efficiency of mitochondrial ATP production, and finally (3) impacted calcium cycling in skeletal muscle (Johanson and Esbaugh 2017) as seen for cardiomyocytes (Brette et al. 2014, Xu
et al. 2016, 2017a, b).
29.3.4 Impacts on Sensory Systems and Behavior
Including Prey-Predator Interactions
A recent study (Rowsey et al. 2019) on red drum determined that larvae exposed to
HEWAF at ~25 μg/L∑50PAH for 24 hrs, 21-day post fertilization (dpf), displayed
increased thigmotaxis (time spent in open areas as opposed to in shelter) leading to
an increased exploration of foraging area. Despite exploring larger foraging areas,
oil-exposed red drum larvae (24 hrs at 35 dpf) caught less prey in a time-limited
M. Grosell et al.
dilutions of <10 μg/L∑50PAH (Stieglitz et al. 2016). This study reported reduced
maximal oxygen uptake, reduced aerobic scope, and a concomitant reduction in
critical swimming speed (U crit ) with no apparent effect on gill histology after only
24 hrs of exposure in young adult mahi-mahi. Subsequent studies employing vascular blood flow probes inserted into anesthetized mahi-mahi revealed normal heart
rate but greatly reduced stroke volume and thereby reduced cardiac output when
exposed for 24 hrs to HEWAF at ~ 10 μg/L∑50PAH prior to experimentation
(Nelson et al. 2016). Similar exposures resulted in reduced U crit for cobia
(Rachycentron canadum) and a substantial reduction in stroke volume, although the
later was largely compensated for by an elevated heart rate (Nelson et al. 2017).
Further studies on cobia employing 24-h HEWAF exposures at ~ 22 μg/L∑50PAH
found reduced cardiac power output (Cox et al. 2017), although this effect could be
mitigated by β-adrenergic stimulation alluding to possible compensations in intact
animals. In addition to the cardiac impacts noted above for pelagic GoM species,
the coastal red drum show reduced aerobic scope and U crit following 24 hrs of acute
exposure to HEWAF at 12 μg/L∑50PAH. These impairments remained for 8 weeks
after the 24-hr exposure attesting to the persistence of cardiac effects induced by oil
exposure to adult GoM species (Johanson and Esbaugh 2017).
Interestingly, reduced swim performance has been observed in oil-exposed GoM
species without a concomitant reduction on maximal oxygen uptake or aerobic
scope. For red drum, a 24-h exposure to HEWAF at 4 μg/L∑50PAH resulted in both
reduced burst swimming speed (U burst ) and U crit without any apparent reductions in
aerobic scope (Johanson and Esbaugh 2017). Similarly, 48-hr HEWAF exposures to
mahi-mahi embryos at 1.2 μg/L∑50PAH followed by rearing in uncontaminated
water for 30 days resulted in reduced U crit , again without reductions in aerobic scope
or maximal oxygen uptake (Mager et al. 2014). The observed effects on swim performance in absence of notable reductions on oxygen supply points to nonrespiratory pathways for PAH impacts on swim performance. Three such possible
nonexclusive pathways include (1) impaired neuromast function leading to reduced
swimming efficiency (Johanson and Esbaugh 2017), (2) reduced efficiency of mitochondrial ATP production, and finally (3) impacted calcium cycling in skeletal muscle (Johanson and Esbaugh 2017) as seen for cardiomyocytes (Brette et al. 2014, Xu
et al. 2016, 2017a, b).
29.3.4 Impacts on Sensory Systems and Behavior
Including Prey-Predator Interactions
A recent study (Rowsey et al. 2019) on red drum determined that larvae exposed to
HEWAF at ~25 μg/L∑50PAH for 24 hrs, 21-day post fertilization (dpf), displayed
increased thigmotaxis (time spent in open areas as opposed to in shelter) leading to
an increased exploration of foraging area. Despite exploring larger foraging areas,
oil-exposed red drum larvae (24 hrs at 35 dpf) caught less prey in a time-limited
M. Grosell et al.