469
hydrocarbons also rise to the surface or are deposited on the ocean floor (Reddy
et al. 2011; French-McCay et al. 2018) (Fig. 27.2).
Deep ocean oil spills can impact a diversity of habitats in the subsea, including
deepwater coral, bottom sediment, and chemosynthetic vent communities (Fisher
et al. 2014). These habitats are home to a diversity of organisms including zooplankton, tube worms, shellfish, jellyfish, squid, and cartilaginous and teleost fish
(Carney 1994; MMS 2000; Fisher et al. 2014; Beyer et al. 2016). Four types of
chemosynthetic communities have been described in the Gulf of Mexico based on
predominant taxa: (1) vestimentiferan tube worms, (2) mytilid mussels, (3) vesicomyid clams, and (4) infaunal clams (MMS 2000). Chemosynthetic vent and deepwater coral habitats are relatively rare in the deep ocean and can be several hundred
years old (MMS 2000; Gerard et al. 2018; Gerard and Fisher 2018). Other benthic
seafloor communities are composed of microbes (e.g., bacteria, protists), foraminifera and metazoa (e.g., harpacticoid copepods, nematodes), macrofauna (e.g., nematodes, polychaetes), and megafauna (e.g., sea stars, sea fans, anemones, isopods,
demersal fishes; Rowe 2017). Invertebrate communities in bottom sediments have
generally low abundance but high species diversity (Gallaway et al. 2001). Deep
ocean communities have unknown sensitivities to hydrocarbons. Additionally,
deepwater coral and chemosynthetic vent communities have unique habitat requirements, and many species are projected to have slow recoveries from a subsea oil
spill because of low recruitment and growth rates in many deep ocean species
(Gallaway et al. 2001; Gerard et al. 2018; Gerard and Fisher 2018).
27.2.2 Offshore
As observed during the DWH oil spill, oil released in the deep ocean will either be
entrained as a subsurface plume of 10–50 μm droplets or move toward the surface
as droplets greater than 50 μm (North et al. 2011; French-McCay et al. 2018b;
Robinson et al. 2018). The offshore euphotic or epipelagic zone is characterized by
depths to 200 meters with sufficient incident sunlight for photosynthesis (Fig. 27.1).
Oil in the euphotic zone and at the sea surface will expose pelagic organisms including plankton, Sargassum communities, jellyfish, fish, sea turtles, marine mammals,
and sea birds.
Surface oiling will substantially impact neuston and near-surface assemblages
which contain early life stages of invertebrates and fish. As seen following the DWH
oil spill, oil exposure of embryonic life stages of pelagic fish and other species to
polycyclic aromatic hydrocarbon concentrations in the low μg/L range can lead to
malformations and long-term consequences on swimming performance (Incardona
et al. 2014; Beyer et al. 2016). Additionally, the limited attenuation of light can lead
to both near-surface generation of photooxidation products of oil and photoenhanced toxicity of bioaccumulated oil residues at depths to 20 meters (Barron 2017).
Sargassum mats are a unique pelagic habitat, with estimated masses in the Gulf
of Mexico greater than one million tons (Gower and King 2011). Sargassum mats
27 Ecotoxicology of Deep Ocean Spills
hydrocarbons also rise to the surface or are deposited on the ocean floor (Reddy
et al. 2011; French-McCay et al. 2018) (Fig. 27.2).
Deep ocean oil spills can impact a diversity of habitats in the subsea, including
deepwater coral, bottom sediment, and chemosynthetic vent communities (Fisher
et al. 2014). These habitats are home to a diversity of organisms including zooplankton, tube worms, shellfish, jellyfish, squid, and cartilaginous and teleost fish
(Carney 1994; MMS 2000; Fisher et al. 2014; Beyer et al. 2016). Four types of
chemosynthetic communities have been described in the Gulf of Mexico based on
predominant taxa: (1) vestimentiferan tube worms, (2) mytilid mussels, (3) vesicomyid clams, and (4) infaunal clams (MMS 2000). Chemosynthetic vent and deepwater coral habitats are relatively rare in the deep ocean and can be several hundred
years old (MMS 2000; Gerard et al. 2018; Gerard and Fisher 2018). Other benthic
seafloor communities are composed of microbes (e.g., bacteria, protists), foraminifera and metazoa (e.g., harpacticoid copepods, nematodes), macrofauna (e.g., nematodes, polychaetes), and megafauna (e.g., sea stars, sea fans, anemones, isopods,
demersal fishes; Rowe 2017). Invertebrate communities in bottom sediments have
generally low abundance but high species diversity (Gallaway et al. 2001). Deep
ocean communities have unknown sensitivities to hydrocarbons. Additionally,
deepwater coral and chemosynthetic vent communities have unique habitat requirements, and many species are projected to have slow recoveries from a subsea oil
spill because of low recruitment and growth rates in many deep ocean species
(Gallaway et al. 2001; Gerard et al. 2018; Gerard and Fisher 2018).
27.2.2 Offshore
As observed during the DWH oil spill, oil released in the deep ocean will either be
entrained as a subsurface plume of 10–50 μm droplets or move toward the surface
as droplets greater than 50 μm (North et al. 2011; French-McCay et al. 2018b;
Robinson et al. 2018). The offshore euphotic or epipelagic zone is characterized by
depths to 200 meters with sufficient incident sunlight for photosynthesis (Fig. 27.1).
Oil in the euphotic zone and at the sea surface will expose pelagic organisms including plankton, Sargassum communities, jellyfish, fish, sea turtles, marine mammals,
and sea birds.
Surface oiling will substantially impact neuston and near-surface assemblages
which contain early life stages of invertebrates and fish. As seen following the DWH
oil spill, oil exposure of embryonic life stages of pelagic fish and other species to
polycyclic aromatic hydrocarbon concentrations in the low μg/L range can lead to
malformations and long-term consequences on swimming performance (Incardona
et al. 2014; Beyer et al. 2016). Additionally, the limited attenuation of light can lead
to both near-surface generation of photooxidation products of oil and photoenhanced toxicity of bioaccumulated oil residues at depths to 20 meters (Barron 2017).
Sargassum mats are a unique pelagic habitat, with estimated masses in the Gulf
of Mexico greater than one million tons (Gower and King 2011). Sargassum mats
27 Ecotoxicology of Deep Ocean Spills