International Journal of Marine Science, 2016, Vol.6, No.9, 1-20
7
routine releases of oil from tankers. It penetrates the plumage of seabirds or fur of marine mammals, affecting heat
insulation and buoyancy (Dalton
et al
., 2010).
The deposition of oil in the shells or by ingestion of emulsified oil during feeding can be caused for tainting of
shellfish. It also do harm to other marine organisms by long term exposure to the persistent and bioaccumulative
components of oil via several indirect ecosystem processes (Velnado
et al.,
2010).
3.7 Radioactive materials
The world's oceans have been a sink for radioactive waste from the production of nuclear weapons and electric
power (Wallberg and Moberg, 2002; Hirose, 2012). In recent years more studies have been carried out on the
movement, distribution and possible concentration of radionuclides in the ocean environment (Fowler, 2011).
Seawater and sediment are the most important sources of radionuclides to marine organisms (Khan and Wesley,
2012). The concentrations of radionuclide in marine biota can be determined by monitoring fishes since the levels
increase in the marine food chain by bio concentration process. The two major consequences of radioactivity at
the organism level are (a) toxic effect on living tissues due to the production of strong oxidizing agents by the
ionization of atoms and molecules of living materials, (b) the mutation activity.
3.8 Upcoming pollutants
The new antifouling agents such as Irgarol and diuron used in small vessels instead of tributyl tin have showed
some persistence in the marine environment (Konstantinou and Albanis, 2004). Other pollutants are brominated
flame retardants, Nano particles, surfactants, perflourinated compounds and endocrine disrupters.
4 Degradation of Toxic Pollutants by Marine Microbes
Microbial communities are the essential but vulnerable part of all the ecosystems, including the deep oceans.
Marine bacteria are often under extreme conditions. There are enormous studies on the ability of marine microbes
to degrade hydrocarbons (Nikolopoulou and Kalogerakis, 2009, Yakimov
et al
., 2007, Pelletier
et al.
, 2004). Many
studies have been conducted to isolate and characterize polycyclic aromatic hydrocarbon (PAH) degrading
bacteria in marine and estuarine ecosystems (Daane
et al
., 2001). Most of the earlier studies were concentrated on
isolating maximum amount of pollutant degrading bacteria. In a study carried out by Bachoon
et al.
(2001), after
one month of exposure, the bacterial community profile of the oil-impacted sediments significantly increased
compared to the control sediment. However the findings of another research showed something different from the
general belief that higher amounts of pollutants may enrich more degrading bacteria. Here the exposure time and
PAH concentration caused a reduction of microbial diversity (Hong
et al
., 2009).
Two divergent views cited in the literature are that: (i) Micro organisms can use organic pollutants as their carbon
source and thus increase their diversity (Feris
et al.
, 2004) (ii) Organic pollutants pose serious threat to
microorganisms and cause serious reduction in their abundance (Bachoon
et al
., 2001).
Hydrocarbon seepage into the benthos affects bacterial community structure as well as diversity (LaMontagne
et
al.,
2004). The study overlooks the long term effects of oil from naturally occurring seeps on sediment bacteria
(LaMontagne
et al.
, 2004). A study conducted in Nigeria (Nwanyanwu, and Abu, 2010) revealed the effects of
petroleum refinery waste water on marine bacteria. In all the bacterial strains tested, the dehydrogenase activity
was progressively inhibited at petroleum concentrations greater than 12.5% (v/v). Discharging of improperly
treated effluents would pose serious threat to metabolism of the bacterial strains in natural environments. The
mangrove sediment microbial structures are susceptible to PAH contamination, and complex microbial
community interactions occur in mangrove sediment (Zhou
et al.
, 2009).
Xenobiotic pollutants act as important agents in the induction of lysogenic bacteria in the marine environment
(Jiang and Paul, 1996). Sewage associated micro organisms grow and compete with indigenous marine microbial
flora (Baross
et al.
, 1975). In the above said study, sewage associated bacteria had shown the capacity to grow
under the oceanic conditions equivalent to depth of 2500 m.
