by marine oil well blowouts or shipping disaster (Jewett et al. 1999; Valentine et al.
2014), dramatically impact on the marine environment. However, also frequent
micro spills due to urban/industrial runoff and shipping may generate chronic and
long-term effects (Camphuysen 2007; Silva et al. 2009; Lindgren et al. 2012; Troisi
et al. 2016; Frometa et al. 2017; Klotz et al. 2018; Xie et al. 2018; Szczybelski et al.
2018; Liu et al. 2019). Lindgren et al. (2012) investigated the effect of polycyclic
aromatic hydrocarbons on benthos and found evident impacts on meiofauna and
microbial communities even at low concentrations of polycyclic aromatic hydrocarbons. The contamination by oil fractions may be observed for many years after an
oil-spill (Tansel 2014). A fairly quick natural recovery (within 2–10 years) may
occur in areas such as mangrove swamps or salt marshes (Kingston 2002) but the
contamination can persist for more than 25 years where the physical removal of oil is
not performed (Kingston 2002).
7.1.2 Oil Composition
Crude oil is a mixture that includes hydrocarbons as the most abundant fraction,
varying in a range of 50–98% of the total composition (Clark and Brown 1977), and
the majority of oils include higher relative percentage of aliphatic hydrocarbons.
Moreover, consistent elements are also oxygen, nitrogen, and sulfur, both as elemental or heterocyclic constituents (e.g., dibenzothiophene) and functional groups.
Hydrocarbons generally consist of alkanes (also called paraffins, on average 30%),
naphtenes (or cycloalkanes) (on average 49%), aromatic (on average 15%),
asphaltenes (porphyrins, esters, phenols, fatty acids, ketones), and resins (amides,
pyridines, carbazoles, quinolines, sulfoxides) ranging from 0 to 40%. Alkanes and
naphtenes (also called saturates) linear or branched, lack double bonds.
Cycloalkanes (mainly cyclopentanes and cyclohexanes) have one or more rings of
carbon atoms and frequently show alkyl substituent(s). Aromatics exhibit one or
more aromatic rings (Matar and Hatch 1994). Asphaltene and resins contain
non-hydrocarbon polar compounds. Oil also contains trace constituents, comprising
less than 1% (v/v), including phosphorus and heavy metals such as vanadium and
nickel. Petroleomics analyses have allowed the identification of more than 17,000
distinct chemical components, revealing the complexity of such organic mixtures.
Furthermore, chemical and physical properties can vary between different type of
crude oils and accordingly their susceptibility to biodegradation and fate in aquatic
environment.
7.1.3 Fate of Oil in Marine Environment
Oil in seawater medium is affected by several processes that change its distribution
and composition. Oil physical and chemical changes may occur in different
7 Biodegradation of Hydrocarbons in Marine Environment
197
2014), dramatically impact on the marine environment. However, also frequent
micro spills due to urban/industrial runoff and shipping may generate chronic and
long-term effects (Camphuysen 2007; Silva et al. 2009; Lindgren et al. 2012; Troisi
et al. 2016; Frometa et al. 2017; Klotz et al. 2018; Xie et al. 2018; Szczybelski et al.
2018; Liu et al. 2019). Lindgren et al. (2012) investigated the effect of polycyclic
aromatic hydrocarbons on benthos and found evident impacts on meiofauna and
microbial communities even at low concentrations of polycyclic aromatic hydrocarbons. The contamination by oil fractions may be observed for many years after an
oil-spill (Tansel 2014). A fairly quick natural recovery (within 2–10 years) may
occur in areas such as mangrove swamps or salt marshes (Kingston 2002) but the
contamination can persist for more than 25 years where the physical removal of oil is
not performed (Kingston 2002).
7.1.2 Oil Composition
Crude oil is a mixture that includes hydrocarbons as the most abundant fraction,
varying in a range of 50–98% of the total composition (Clark and Brown 1977), and
the majority of oils include higher relative percentage of aliphatic hydrocarbons.
Moreover, consistent elements are also oxygen, nitrogen, and sulfur, both as elemental or heterocyclic constituents (e.g., dibenzothiophene) and functional groups.
Hydrocarbons generally consist of alkanes (also called paraffins, on average 30%),
naphtenes (or cycloalkanes) (on average 49%), aromatic (on average 15%),
asphaltenes (porphyrins, esters, phenols, fatty acids, ketones), and resins (amides,
pyridines, carbazoles, quinolines, sulfoxides) ranging from 0 to 40%. Alkanes and
naphtenes (also called saturates) linear or branched, lack double bonds.
Cycloalkanes (mainly cyclopentanes and cyclohexanes) have one or more rings of
carbon atoms and frequently show alkyl substituent(s). Aromatics exhibit one or
more aromatic rings (Matar and Hatch 1994). Asphaltene and resins contain
non-hydrocarbon polar compounds. Oil also contains trace constituents, comprising
less than 1% (v/v), including phosphorus and heavy metals such as vanadium and
nickel. Petroleomics analyses have allowed the identification of more than 17,000
distinct chemical components, revealing the complexity of such organic mixtures.
Furthermore, chemical and physical properties can vary between different type of
crude oils and accordingly their susceptibility to biodegradation and fate in aquatic
environment.
7.1.3 Fate of Oil in Marine Environment
Oil in seawater medium is affected by several processes that change its distribution
and composition. Oil physical and chemical changes may occur in different
7 Biodegradation of Hydrocarbons in Marine Environment
197