508
to anthropogenic and environmental stressors (Vega-Retter et al. 2018). Genetics
and oil: Transcriptomics, epigenetics and genomics as tools to understand animal
responses to exposure across different time scales (see Portnoy et al. 2020) discusses what the field of transcriptomics is and what it can tell us about effects of
exposure to oil.
Several studies have linked transcriptome changes following exposure to DWH
oil with endpoints of ecological significance. Whitehead et al. (2012) showed differences in gene expression profiles of Gulf killifish in response to oil contamination
from the 2010 DWH oil spill, particularly decreased physiological functions in
osmoregulation, respiration, and excretion, which persisted for 2 months postoiling. Oil exposure affected multiple molecular pathways in developing mahimahi, including E1/E2 signaling, steroid biosynthesis, and ribosome biogenesis
pathways (Xu et al. 2016). Dubansky et al. (2013) showed that Gulf killifish collected from areas affected by DWH oil had significantly altered transcriptional patterns, including a number of genes and pathways involved in xenobiotic response or
oil detoxification. Exposure to very low levels (<5 μg/L∑PAH50) caused altered
expression of many pathways in early life stage red drum in a manner that was
dependent on both oil type and age of the embryo (Xu et al. 2017b), indicating that
results from one exposure regime or age class, even within species, may not be fully
informative of the transcriptional effects of other exposure regimes or ages.
Exposure to oil-contaminated sediment altered liver transcriptional patterns in juvenile southern flounder, including effects on a number of immune-related genes,
matching an observed oil-induced immunosuppression following bacterial challenge (Bayha et al. 2017).
29.4 Conclusions and Directions for Future Research
Although direct comparisons among species differences are scarce and further studies clearly are needed, the available literature demonstrates significant speciesspecific differences in sensitivity underscoring the importance of test organism
choice. Similarly, life stage-dependent sensitivity differences are also obvious with
early life stages generally being more susceptible. However, later life stages should
not be ignored as some endpoints, including cardiac function, immune system function, and sensory and central nervous systems, may show effects even at relatively
low exposure concentrations in later life stages.
In addition to choice of organisms and life stages to be tested, the endpoint examined will influence the impression of sensitivity. Cardiac development and cardiac
function have long been viewed as central targets for oil exposure and are sensitive
to oil exposure at low and environmentally realistic levels (<10 μg/L∑PAH50).
However, recent studies have revealed that eye development and immune system
function can be impacted at lower concentrations (<1 μg/L∑PAH50) illustrating the
importance of considering multiple endpoints. Transcriptome wide responses have
been employed successfully in recent years to shed light on additional relevant
M. Grosell et al.
to anthropogenic and environmental stressors (Vega-Retter et al. 2018). Genetics
and oil: Transcriptomics, epigenetics and genomics as tools to understand animal
responses to exposure across different time scales (see Portnoy et al. 2020) discusses what the field of transcriptomics is and what it can tell us about effects of
exposure to oil.
Several studies have linked transcriptome changes following exposure to DWH
oil with endpoints of ecological significance. Whitehead et al. (2012) showed differences in gene expression profiles of Gulf killifish in response to oil contamination
from the 2010 DWH oil spill, particularly decreased physiological functions in
osmoregulation, respiration, and excretion, which persisted for 2 months postoiling. Oil exposure affected multiple molecular pathways in developing mahimahi, including E1/E2 signaling, steroid biosynthesis, and ribosome biogenesis
pathways (Xu et al. 2016). Dubansky et al. (2013) showed that Gulf killifish collected from areas affected by DWH oil had significantly altered transcriptional patterns, including a number of genes and pathways involved in xenobiotic response or
oil detoxification. Exposure to very low levels (<5 μg/L∑PAH50) caused altered
expression of many pathways in early life stage red drum in a manner that was
dependent on both oil type and age of the embryo (Xu et al. 2017b), indicating that
results from one exposure regime or age class, even within species, may not be fully
informative of the transcriptional effects of other exposure regimes or ages.
Exposure to oil-contaminated sediment altered liver transcriptional patterns in juvenile southern flounder, including effects on a number of immune-related genes,
matching an observed oil-induced immunosuppression following bacterial challenge (Bayha et al. 2017).
29.4 Conclusions and Directions for Future Research
Although direct comparisons among species differences are scarce and further studies clearly are needed, the available literature demonstrates significant speciesspecific differences in sensitivity underscoring the importance of test organism
choice. Similarly, life stage-dependent sensitivity differences are also obvious with
early life stages generally being more susceptible. However, later life stages should
not be ignored as some endpoints, including cardiac function, immune system function, and sensory and central nervous systems, may show effects even at relatively
low exposure concentrations in later life stages.
In addition to choice of organisms and life stages to be tested, the endpoint examined will influence the impression of sensitivity. Cardiac development and cardiac
function have long been viewed as central targets for oil exposure and are sensitive
to oil exposure at low and environmentally realistic levels (<10 μg/L∑PAH50).
However, recent studies have revealed that eye development and immune system
function can be impacted at lower concentrations (<1 μg/L∑PAH50) illustrating the
importance of considering multiple endpoints. Transcriptome wide responses have
been employed successfully in recent years to shed light on additional relevant
M. Grosell et al.