356
22.1 Introduction
The Deepwater Horizon (DWH) blowout and oil spill was a significant event. It is
uncertain exactly how much oil was released from April through July 2010. One
estimate is about 4.9–6.2 million barrels (Griffiths 2012), but the estimate is 3.19
million barrels as determined by court ruling (Deepwater Horizon Natural Resource
Damage Assessment Trustees 2016). This is an immense amount of oil, more than
enough to fuel a single household through the year 500,000 or power the world for
40 minutes. It is also ≈10 times greater than the combined leakage rate of all of the
oil seeps in the Gulf of Mexico (GoM) (MacDonald et al. 2015). To contain the oil
spill, about 3 million liters of dispersants were also released during the spill
(Kujawinski et al. 2013). The dispersants are toxic as well (Montagna and
Arismendez 2019; Almeda et al. 2014) and can increase the toxicity of the oilderived compounds by making them more biologically available (Fern et al. 2015;
Gong et al. 2014).
This was the first deepwater oil release, so there was no available information to
predict impacts and consequences from this spill. Many assumed there would be no
impact to the bottom because of the buoyancy of oil. The first sign of trouble was
the report of deep-sea plumes at 1000–1300 m deep (Camilli et al. 2010; Joye et al.
2011), and the second sign was the sedimentation event that included oiled marine
snow (Passow 2016). Eventually, it was estimated that as much as 35% of the oil
was entrained in the deep-sea plumes (Ryerson et al. 2012) and that 4–31% of the
oil was trapped in the deep sea, covering an area of 3200 km
2
(Valentine et al. 2014).
This extensive coverage of a highly impacted area was a cause of concern for deepsea benthic habitats.
Much research followed to develop an understanding of the impacts to the deepsea benthos. Part of the motivation was to assess damage to the natural resources,
part was scientific curiosity, and part was concern for the extensive habitats that
support the oceanic food webs of the GoM. The two main habitats in the deep GoM
are the soft-bottom and hard-bottom benthos. The soft-bottom is the dominant habitat making up about 95% of the seafloor bottom composed primarily of muddy bottom where the main faunal component is infauna that live in the mud. There are two
dominant taxa of infauna, the small macrofauna (greater than 300 μm in size) and
the very small meiofauna (between 43 μm and 300 μm in size). Many geological
features in the GoM are hard and create outcroppings. These outcroppings have
attached benthos such as corals. These organisms are also considered epibenthos
organisms that live on the sediment surface. Here, a review is presented of the studies of the effect of the deepwater deposition of oil on the benthos, both soft-bottom
and hard-bottom.
P. A. Montagna and F. Girard
22.1 Introduction
The Deepwater Horizon (DWH) blowout and oil spill was a significant event. It is
uncertain exactly how much oil was released from April through July 2010. One
estimate is about 4.9–6.2 million barrels (Griffiths 2012), but the estimate is 3.19
million barrels as determined by court ruling (Deepwater Horizon Natural Resource
Damage Assessment Trustees 2016). This is an immense amount of oil, more than
enough to fuel a single household through the year 500,000 or power the world for
40 minutes. It is also ≈10 times greater than the combined leakage rate of all of the
oil seeps in the Gulf of Mexico (GoM) (MacDonald et al. 2015). To contain the oil
spill, about 3 million liters of dispersants were also released during the spill
(Kujawinski et al. 2013). The dispersants are toxic as well (Montagna and
Arismendez 2019; Almeda et al. 2014) and can increase the toxicity of the oilderived compounds by making them more biologically available (Fern et al. 2015;
Gong et al. 2014).
This was the first deepwater oil release, so there was no available information to
predict impacts and consequences from this spill. Many assumed there would be no
impact to the bottom because of the buoyancy of oil. The first sign of trouble was
the report of deep-sea plumes at 1000–1300 m deep (Camilli et al. 2010; Joye et al.
2011), and the second sign was the sedimentation event that included oiled marine
snow (Passow 2016). Eventually, it was estimated that as much as 35% of the oil
was entrained in the deep-sea plumes (Ryerson et al. 2012) and that 4–31% of the
oil was trapped in the deep sea, covering an area of 3200 km
2
(Valentine et al. 2014).
This extensive coverage of a highly impacted area was a cause of concern for deepsea benthic habitats.
Much research followed to develop an understanding of the impacts to the deepsea benthos. Part of the motivation was to assess damage to the natural resources,
part was scientific curiosity, and part was concern for the extensive habitats that
support the oceanic food webs of the GoM. The two main habitats in the deep GoM
are the soft-bottom and hard-bottom benthos. The soft-bottom is the dominant habitat making up about 95% of the seafloor bottom composed primarily of muddy bottom where the main faunal component is infauna that live in the mud. There are two
dominant taxa of infauna, the small macrofauna (greater than 300 μm in size) and
the very small meiofauna (between 43 μm and 300 μm in size). Many geological
features in the GoM are hard and create outcroppings. These outcroppings have
attached benthos such as corals. These organisms are also considered epibenthos
organisms that live on the sediment surface. Here, a review is presented of the studies of the effect of the deepwater deposition of oil on the benthos, both soft-bottom
and hard-bottom.
P. A. Montagna and F. Girard