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Oil Platforms in the North Sea, alkylphenoles and polycyclic aromatic hydrocarbons form oil drilling, and their effect on the Atlantic cod residing in the North Sea
Hansen  , Department of Biology and Wildlife, University of Alaska Fairbanks, Fairbanks, Alaska, USA
ABSTRACT: The Atlantic cod (Gadhus morhua) near oil platforms encounter problems due to exposure of spillage containing pollutants, such as alkylphenols and polycyclic aromatic hydrocarbons. They have adverse effect on the individual through being carcinogenic, or on the population through femininization, delayed maturation, and changed tissue characteristics. The oil platforms can also be useful to the Atlantic cod through becoming artificial reefs that can be used as new source of habitat and food.
KEY WORDS: alkylphenols artificial reefs, Atlantic cod, femininization, Gadhus morhua, hormone-disruption, oil, polycyclic aromatic hydrocarbons, tissue change
Oil platforms are big sources of contaminants to marine environments. Two major contaminant groups coming from oil drilling in the sea are alkylphenols (AP) and polycyclic aromatic hydrocarbons (PAH). The APs are contaminants that resemble estrogens (Newman 2010), they affect marine animals by femininization in males, and females to have a slower development of gametes or reverse the formation of female reproductory organs (Meier et al. 2007b). They also affect Atlantic cod (Gadhus morhua) in many other ways; disturb EROD activity, apoptosis and necrosis (Sturve et al. 2006), and tissue membrane structure (Meier et al. 2007a). PAHs are found in crude oil, they are contaminants that can be carcinogenic to the Atlantic cod, and comes from incomplete burning of the oil extracted from the soil (Newman 2010).
But oil platforms may also be positive for the cod. When the platforms go out of commission they can be made into artificial reefs for the Atlantic cod, thus helping increase the population. This have been tested and shown quite successful (Jørgensen et al. 2002).
Alkylphenols (AP) are mixtures of isomers made through industrial activities. They get to marine environments mainly through detergents used on oil platforms. The problem with these contaminants is that they act as estrogen, causing some male animals to produce vitellogening, which is a protein only synthesized by females. The APs from detergents have both hydrophilic and hydrophobic parts to their structures, which make them able to function in a lot of different substrates. They were widely used in the 1960s, which still causes a problem due to them being very resistant to natural breakdown in the environment, thus causing a huge problem in aquatic systems (Newman 2010).
Alkylphenols and their effect on the Atlantic cod (Gadhus morhua)
The Institute of Marine Research in Norway did an experiment on the effects of APs on Atlantic cod. They found that the APs affected the natural steroid levels in both the female and male fishes. In the females the concentration on estrogen (17Î²-estradiol) decreased in the fishes exposed to the AP mix used and the levels of testosterone in the plasma decreased, but only in the females exposed to high doses of APs. In the male fish the testosterone levels decreased significantly and at the end of the treatment the levels of estrogens in the males were on the same levels as those found in the females. Also the concentrations of plasma vitellogenin were several times as high in the AP treated females and males, as in the untreated fishes. The weight of the fishes was also affected by the treatment. Both males and females treated with the APs lost significantly more weight than unexposed fish. The most critical effect of the APs in the female fish is that it decreases or reabsorbed oocytes, hence making the fishes unable to produce eggs. In the males the amount of spermatiogonia and spermatocytes increased, but the amount of spermatozoa decreased. There were also results indicating stop of maturation of the males. All this indicates femininization of the males, and developmental disturbance in the female, which in turn makes the fishes unable to reproduce. This in turn affects the population size and might be the initial face of local extinction of the population exposed to APs. One of the APs that has been most studied is the nonylphenol (Meier et al. 2007b).
Nonylphenol (NP) is an alkylphenol that have been found as pollutant from the North Sea oil. The effects of the NPs on the Atlantic cod have been studied, and found to significantly show EROD (Ethoxyresorufin-O-deethylase) activity in these fishes. The NP affects the CYP1A (Cytochorme P4501A) and CYP3A (Cytochrome P4503A) protein expression of juvenile Atlantic cod, and in the experiment done by Sturve et al. (2006) the NP led to decrease in both CYP1A- and CYP3A-protein expression in juvenile cod. They also tested the cods reactions to oil extracted from the North Sea. The physiological reactions in the cod were increase in CYP1A levels, and increase in EROD activities mediated by CYP1A. They also mixed the oil with APs to check if APs in the oil would affect the Atlantic cod. They found that alkylphenols in the production water from the oil drilling interfered with the CYP1A and CYP3A response in the cod. Because CYP enzymes are involved in detoxification of xenobiotics, this inhibition of the CYPs might have severe effect on the cod.
Glutathione S-transferase (GST) depletion has been observed to lead to apoptosis, necrosis and DNA fragmentation (Higuchi 2004). These activities might be increased in fish because of phase II mediated conjugation of GST and nonylphenol, thus increase GST activities in Atlantic cod. Increased levels of oxidized glutathione were found in the Atlantic cod exposed to North Sea oil, indicating oxidative stress and inhibition of glutathione reductase (Sturve et al. 2006).
There has also been done a test on how the APs affect the tissue in cods. Meier et al. (2007a) found that the APs affect the lipophilicity in the brain and the liver of the cods. They found surface tension at a given molecular area due to the AP, the levels of brain-cholesterol were lowered, and the composition of the different liver-lipid compounds was altered. These changes increased with increase in exposure to APs, and also the ability of the interference with the lipid membranes increased with increase of chain length of the alkyl group in the APs. The way the APs incorporate itself into the lipophilic monolayers is by penetrating the lipid-water boundary with its lipophilic alkyl-benzene domain, and its hydrophilic OH groups placed between the hydrophilic headgroups of the lipids, thus decreasing the movability of the lipidlayer.
POLYCYCLIC AROMATIC HYDROCARBONS
Polycyclic aromatic hydrocarbons (PAHs) are produced through incomplete burning of wood and fossil fuels. They may be precursors to carcinogenic substrates, and are found as a pollutant everywhere. Those PAHs that originate in oil often end up alkylated and are formed slowly under low temperatures during petrogenesis. They can make out 0,7-7% of the crude oil pumped up from the sediments, and are also naturally formed by plants, fungi and bacteria. The PAHs with low molecular weight tend to be more toxic than the PAHs with higher molecular weight. Also the low weight molecules tend to be in air, while the heavier ones are found in soil (Newman 2010).
Liver cancer in cod due to PAHs
The heavy molecules of PAHs are lipophilic and get absorbed into organic and inorganic matter fast. Usually it binds to excrements from aquatic animals in the aquatic systems, but they are still bioavailable to fish. This might be because the fish tend to eat smaller invertebrates that eat of the sediments, or the fish feed in the sediments themselves. PAHs also tend to bioaccumulate in fish. Normally it doesn't bioaccumulate and biomagnify to degree of adverse effect in teleost fishes, but it has had an increasing carcinogenic effect in the liver of wild fish. That fish suddenly express carcinogenic response to the PAH contaminants is due to increase in release of these pollutants through increase in industry and urbanization of bigger areas. What can be seen on affected livers are lesions if several types, pigment foci, timorous nodules, and fluid filled cysts. There have been proven high liver lesions in places with high PAH concentration in the sediment (Newman 2010).
DECOMMISSIONED OIL PLATFORMS
Decommissioned oil platforms are not really to any use when they are shut down. One idea to make them usable again is to use them as artificial reefs when they are decommissioned, to try and counteract some of the decrease in habitat for the Atlantic cod. Artificial reefs have been proven really effective and helped increase biomass and better the living situation for many species. Problems one might encounter are how to design the reef, how to construct and build it, and how to fit the needs (food, shelter, environmental conditions, and no dangerous pollutants nearby) of the species supposed to live there. These projects are still much debated (Pickering 1997). The idea of making decommissioned oil platforms into artificial reefs for the Atlantic cod has been tried out in the North Sea. From 25 May to 3 July and 9 July to 13 August in 1998, and 8 May to 10 May in 1999 eight receivers were installed on and close to the Albueskjell 2/4 Fox platform. Cod were tagged and supervised by these automatic receivers. They found three different behavior patterns for the cod: fish staying at the platform, leaving for shorter or longer periods and returning, and leaving forever. It was found that of the total 31 fish tagged, 18 was found at the platform, 4 was found a bit further out, 8 fish left and came back, and 1 left and was never discovered again. Off all these fishes 8 was recaptured through fishing, and 4 was registered again in May 1999. The decommissioned oil platform was shown to create good habitat for the Atlantic cod (Jørgensen et al. 2002).
Both alkylphenols (AP) and polycyclic aromatic hydrocarbons (PAH) are found in marine environments near oil platforms due to emission and spillage. Their effect on the Atlantic cod living there is very severe, and can be very bad for the population as a whole. The males get feminizised by the APs, and the females get slowed or reversed gamete maturity. They also cause changes in ability to detoxify by CYP1A and CYP3A, and change the character of the lipophilic membranes. PAHs have adverse effect on the Arctic cod by having carcinogenic effect.
But the oil platforms can also be useful to the cod through becoming artificial reefs for them by creating new, vital habitat for the cod. Their numbers are decreasing due to the effects by the pollutants from oil platforms still being used, and due to overfishing. Decommissioned oil platforms can therefore be very useful in creating new habitats for the cod if they can provide proper living conditions for the Atlantic cod.
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Meier S., Andersen T. C., Lind-Larsen K., Svardal A., Holmsen H., 2007a, "Effects of alkylphenols on glycerohpospholipids and cholesterol in liver and brain from female Atlantic cod (Gadus morhua)", Comparative Biochemestry and Physiology, part C 145: 420-430
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