International Journal of Marine Science, 2016, Vol.6, No.9, 1-20
9
biochemical responses are monooxygenase induction, metallothionein induction and acetylcholine esterase
inhibition.
d) Genetically based resistance: Assessing the resistance acquired by genetically different strains of species to
pollutants.
5.3 Bioindicators – bioindicators of various types of pollutants
Algae, macrophyte, zooplankton, insect, bivalve molluscs, gastropod, fish and amphibian are all considered as
bioindicators. High tolerance of pollutants without death, wide abundance, distribution, long lifecycle, importance
of the organism in food chain and easy sampling are all considered to be the characters of a perfect bioindicator.
In spite of the tremendous use of marine fauna in biomonitoring programs, photosynthetic organisms like algae
(seaweeds) have been increasingly used as biodetectors to monitor xenobiotics in marine environments (Barreiro
et al
., 2002; Conti and Cecchetti, 2003; Conti et al., 2007). Microalgae has been referred to as green liver of
oceans as they play central role in monitoring xenobiotics and pollutant cycling across the globe (Nystroan
et al
.,
2002) due to their substantial biomass and comparatively large surface-to-volume ratio (Okamoto and Colepicolo,
1998).Seaweed species were used as bioindicator for toxic trace elements (Serfor-Armah,
et al
., 2001).
5.4 Biomarkers – significance, identified biomarkers
Biomarker can be defined as the measurements of body fluids, cells, or tissues that indicate in biochemical or
cellular terms the presence of contaminants or the magnitude of the host response (Bodin
et al
., 2004). Biomarkers
offer an effective early warning system in biomonitoring of aquatic environments. Biochemical, cellular,
physiological and behavioral variations in the tissue, body fluids or of whole marine organisms could be well
defined by biomarkers (Lam and Gray, 2003; Galloway
et al
., 2002, 2004).
The effect of pollutants on the cellular biochemistry of microalgae and the biochemical mechanisms that they use
to detoxify pollutants are being well researched around the world (Conti
et al.,
2007; Barros
et al
., 2005).
Lysosomal membrane stability (LMS) is considered as a very reliable biomarker of general stress in
biomonitoring studies, as it is the main lysosomal response to a wide range of pollutants (Domouhtsidou and
Dimitriadis, 2001). LMS test of digestive glands and Neutral Red Retention Assay (NRR) of the hemocyte
lysosomes are evaluated to check the stability of lysosomal membrane, as both are influenced in marine bivalves
by a wide range of stressors including temperature fluctuations (Petrovic
et al
., 2004; Bocchetti and Regoli, 2006;
Moore
et al
., 2006; 2007). It has been reported that NRR measures the lysosomal content efflux into the cytosol
which, in stressed mussels, reflects a physiological process after membrane damage and comparatively measures
the capacity of cellular processes to adapt to stress conditions (Lowe and Pipe, 1994).
Acetylcholinesterase (AChE) activity has been measured by many researchers as exposure biochemical biomarker
in the invertebrates in coastal waters and rivers (Moulton
et al
., 1996; Stien
et al
., 1998). Thus they have potential
application in marine environment in screening the effects of pesticides and other pollutants in some vertebrate
and invertebrate species. The responses of these biomarkers in digestive glands and hemocytes of horse-bearded
mussel Modiolus barbatus during thermal stress was monitored (Vasileios
et al
, 2012). Results of several other
works have also reported the connection between responses of biomarkers in marine molluscs to thermal stress
(Domouhtsidou and Dimitriadis, 2001; Kagley
et al
., 2003; Petrovic
et al
., 2004; Bocchetti and Regoli, 2006;
Moore
et al
., 2006a, 2007).
The use of biomarkers could provide useful information about the higher critical lethal ambient temperatures
(Tcmax) initiating irreversible cellular damage in the tissues of marine bivalves during perturbation of its
ecosystem because of global warming (Vasileios
et al.
, 2012).
Another study in line with previous investigation,point outs the histochemical localization of
N-acetyl-b-hexozaminidase (Hex), acid phosphatase (AcP) and b-glucuronidase (b-Gus) in the digestive gland of
