390
lived groupers) are still alive from that spill 40 years ago, but post- spill data collected
in the past 5 years allow interpretation of chronic contamination either from current
hydrocarbon inputs or from previous spills sequestered in GoM sediments.
24.2 Larval Abundance and Growth Indices
The GoM is inhabited by over 1500 fish species (Murawski et al. 2016) including
those that are reef-dwelling, demersal, pelagic, highly migratory, and estuarinedependent, exhibiting a wide diversity of life-history strategies. Most marine fishes
spawn pelagic, buoyant eggs that are fertilized externally and float in the water
column near the sea surface (Kendall Jr. et al. 1983). These critical pelagic egg and
larval phases, including species of commercial and recreational importance in the
GoM, coincided with both the DWH and Ixtoc 1 spills (Chancellor 2015; Chancellor
et al. 2020). Murawski et al. (2016) outlined three conditions that have to be met for
oil spills to have significant population-level effects on fishes. Firstly, adverse
effects include increased mortality and reduced fitness of animals as the result of oil
exposure. Secondly, the observed environmental concentrations are sufficient to
cause increased mortality and/or sub-lethal impairment. Lastly, a substantial fraction of the population must be exposed to critical levels of oil in the environment
resulting in adverse effects (mortality and sub-lethal impairment). For the DWH and
the Ixtoc 1 spills, all three conditions seem to have been met. For example, using
broad-scale SEAMAP ichthyoplankton sampling data, Chancellor (2015) computed
the overlap between the surface expression of the DWH spill and total fish larvae in
the northern GoM (e.g., US waters). She estimated that ~27% of the total fish larvae,
representing 110 taxa in the northern GoM, were at locations where they were
potentially to be exposed to DWH oil (Chancellor 2015). The prolonged and widespread surface expression of the Ixtoc 1 spill also likely overlapped with shallowand deepwater species over a broad stretch of the southwestern GoM (Sun et al.
2015). Planktonic early life-history stages are highly sensitive to fluctuations in
many environmental conditions, such as light, temperature, salinity, oxygen, and
anthropogenic pollution. Thus, adverse effects including decreased survival and
recruitment from a large pollution event, such as an oil spill, would be highly plausible and anticipated.
Larval abundance and condition were evaluated pre- and post-DWH using fieldcaught larvae to assess the potential impacts of oil exposures. Ichthyoplankton surveys conducted before, during, and after DWH along the coast of Alabama
investigated potential larval impacts on red snapper (Lutjanus campechanus) and
Spanish mackerel (Scomberomorus maculatus) by evaluating abundance, condition
indices (morphometrics and dry weight), environmental parameters (e.g., wind
speed, water temperature, etc.), and changes in stable isotopes (Hernandez Jr et al.
2016; Ransom et al. 2016). There were no significant differences in their larval
abundances in either the Spanish mackerel or the red snapper across years postDWH. However, examining a wider spatial domain in the north central GoM,
E. L. Pulster et al.
lived groupers) are still alive from that spill 40 years ago, but post- spill data collected
in the past 5 years allow interpretation of chronic contamination either from current
hydrocarbon inputs or from previous spills sequestered in GoM sediments.
24.2 Larval Abundance and Growth Indices
The GoM is inhabited by over 1500 fish species (Murawski et al. 2016) including
those that are reef-dwelling, demersal, pelagic, highly migratory, and estuarinedependent, exhibiting a wide diversity of life-history strategies. Most marine fishes
spawn pelagic, buoyant eggs that are fertilized externally and float in the water
column near the sea surface (Kendall Jr. et al. 1983). These critical pelagic egg and
larval phases, including species of commercial and recreational importance in the
GoM, coincided with both the DWH and Ixtoc 1 spills (Chancellor 2015; Chancellor
et al. 2020). Murawski et al. (2016) outlined three conditions that have to be met for
oil spills to have significant population-level effects on fishes. Firstly, adverse
effects include increased mortality and reduced fitness of animals as the result of oil
exposure. Secondly, the observed environmental concentrations are sufficient to
cause increased mortality and/or sub-lethal impairment. Lastly, a substantial fraction of the population must be exposed to critical levels of oil in the environment
resulting in adverse effects (mortality and sub-lethal impairment). For the DWH and
the Ixtoc 1 spills, all three conditions seem to have been met. For example, using
broad-scale SEAMAP ichthyoplankton sampling data, Chancellor (2015) computed
the overlap between the surface expression of the DWH spill and total fish larvae in
the northern GoM (e.g., US waters). She estimated that ~27% of the total fish larvae,
representing 110 taxa in the northern GoM, were at locations where they were
potentially to be exposed to DWH oil (Chancellor 2015). The prolonged and widespread surface expression of the Ixtoc 1 spill also likely overlapped with shallowand deepwater species over a broad stretch of the southwestern GoM (Sun et al.
2015). Planktonic early life-history stages are highly sensitive to fluctuations in
many environmental conditions, such as light, temperature, salinity, oxygen, and
anthropogenic pollution. Thus, adverse effects including decreased survival and
recruitment from a large pollution event, such as an oil spill, would be highly plausible and anticipated.
Larval abundance and condition were evaluated pre- and post-DWH using fieldcaught larvae to assess the potential impacts of oil exposures. Ichthyoplankton surveys conducted before, during, and after DWH along the coast of Alabama
investigated potential larval impacts on red snapper (Lutjanus campechanus) and
Spanish mackerel (Scomberomorus maculatus) by evaluating abundance, condition
indices (morphometrics and dry weight), environmental parameters (e.g., wind
speed, water temperature, etc.), and changes in stable isotopes (Hernandez Jr et al.
2016; Ransom et al. 2016). There were no significant differences in their larval
abundances in either the Spanish mackerel or the red snapper across years postDWH. However, examining a wider spatial domain in the north central GoM,
E. L. Pulster et al.