Marine Bio-accumulation; Apex predators

“I don’t know how to save the world. I don’t have the answers or The Answer. I hold no secret knowledge as to how to fix the mistakes of generations past and present. I only know that without compassion and respect for all of Earth’s inhabitants, none of us will survive—nor will we deserve to.” – Leonard Peltier


Orca’s are the most toxic animals in the planet due to human interference. some found to be so toxic that proper disposal needs to take place in a TOXIC WASTE FACILITY. 


There is a direct influence of chemicals while looking at biological processes like bioaccumulation and bio magnification. Using apex predators as an example shows us this influence, and the chemical and physical properties of each chemical involved in the process. Structure and toxicity of each chemical explains in greater depth what is happening in this process, and allows us to compare it to a real world situation. Polychlorinated biphenyls (PCB) and Dichlorodiphenyltrichloroethane (DDT) have many effects on bioaccumulation and this all occurs as it transfers up the food chain. Apex predators show us all we need to know about these chemicals, because of the vast amounts found in their tissues, and the negative effects known to be correlated with this. Pollution due to PCBs and DDTs and bioaccumulation can be better described and understood by using the organic chemistry to provide solid evidence of what is happening inside these apex predators. The importance of organic chemistry will be outlined throughout and the organic chemicals will be thoroughly described in terms of what is happening once reaching the highest trophic level.


       Bioaccumulation is the accumulation of substances such as pesticides or other chemicals in an organism. Bioaccumulation is highest in apex predators due to the bio magnification up the food chain. Many organic chemicals are a part of this process and provide a better understanding to the process while looking at their chemical makeup and physical and chemical properties. Understanding the chemical makeup of toxins involved in bioaccumulation of apex predators can help provide a greater understanding of what is happening, and can be used in many other fields to help solve potential problems. Organic chemicals involved in biomagnification include Polychlorinated biphenyls (PCBs) and Dichlorodiphenyltrichloroethane (DDTs). Both chemicals have detrimental effects on the environment and species that inhabit these areas due to their chemical make up and properties. Understanding the chemistry of these chemicals allows us to better understand what is actually happening when applied to a real-world scenario.

Polychlorinated biphenyls (PCBs)

An organic chlorine compound. Once widely used as dielectric and coolant compounds. Chemical and physical properties of PCBs are pale- yellow in color and they are hydrophobic with very low water solubility’s, PCBs have very high thermal conductivity and densities vary as the degree of chlorination increases. As chlorination increases so does the melting point, and vapor pressure and water solubility will decrease.(2) Geisz (2008) A physical property that is important regarding bioaccumulation is that they do not break down easily and take a long time to degrade. Although this is the characteristic that made this compound attractive for many industries, this is also the reason behind the negative environmental impacts.  PCBS come from Biphenyls, when hydrogen atoms are replaced by chlorine you now have PCBs. There are many different individual PCB found in many commercial products due to the high amount of different chemical compounds in which the chlorine atoms can take the place of hydrogen atoms. Each different compound has a different toxic effect, the deciding factor comes from the structure and toxicity of the specific compound.  PCBs can be divided into two distinct groups. The first is the coplanar or non-ortho group which is described as having a rigid structure consisting of two phenyl rings along the same plane. The second group is known as the Noncoplanar or ortho PCBs. When chlorine atoms change positions, it determines the group which is it placed into. When placed into the Ortho group they are known as neurotoxic and immunotoxin and considered to be less toxic then the Non ortho atoms. PCBs can vary in toxicity as you will throughout bioaccumulation especially in apex predators. PCBs do not readily break down once they are in the environment or in a species, Necropsies of Cetaceans have exposed exactly this. Blubber and decomposed caucuses are tested for levels of PCB contaminants and we are seeing the highest amounts ever recorded. Orca whales have PCB levels recorded so high that they need to be properly disposed of in a toxic waste facility. PCBs accumulate in Tissues and blubber of cetaceans, fresh carcasses have recorded levels of 83.3%.(3) Hickie, (2013) This extremely high percentage has also been suggested to be the main cause of the stranding and sudden deaths of these animals. Animals with a more mature status have a higher level of toxicity according to a study conducted by (4) Jarvis (2007). Mature animals having higher levels helps to explain the breakdown of PCBs in the environment and the nature of the chemical. Over time the chemical collect and build up much faster than it can break down and leave the environment which it is present.

PCBs can be found in many different species but mostly in Apex predators. Because they are so high on the food chain biomagnification occurs and has an indirect impact on apex predators. Negative relationships have been found with PCBs such as a decline within the species (5) Lepak (2009) PCBS have been recognized as a significant contaminant, and acting as an endocrine disrupting compound in many apex predators and they highly impact the survival rate and reproductive success which indirectly leads to population levels. Although much is known about the contaminant, the direct pathway is largely unknown (6) Lepak (2012). Looking at a study conducted by (9) Ross (2016) two possible pathways are investigated. The first is through a common theory throughout my research of atmospheric disposition of PCBS. Another pathway is through Bio deposits into the ecosystem. Contaminants of PCBs In Marine ecosystems have been universally distributed, meaning they occur in almost all marine algae and animals. Due to their high stability, Low orderability, and lipid solubility they bioaccumulate and create concentrated areas of polluted ecosystems.

Bioaccumulation is the transport of these chemicals up the food chain. This is reason that apex predators are greatly impacted by these pollutants. The environmental transport of PCBs happens through water, air and the Biosphere through both anthropogenic use and disposal. Transport of these chemicals happens in water due to the low vapor pressure quality of PCBs. The Hydrosphere is the main reservoir and the pressure of the ocean waters increase with depth causing the PCBs to sink because they are heavier than the water (11) Zeng (2017). The greatest sinks are in the deepest ocean trenches for this reason of high concentration. Transport through air is much lower because the atmosphere is a primary route od transport for these chemicals. The air is how these chemicals make it from place to place and enter our marine ecosystems. The Biosphere is another means of transport of these chemicals. In the Biosphere they are presented as either bacteria or eukaryotes. This is a huge factor to biomagnification and accumulation. When a species consumes a contaminates organism it then accumulates in that organism to only be eaten by a larger species, which will obtain an even larger number of PCBs. Biological metabolism of PCBs is species dependent. This chemical can be synthesized through P450 enzymes. Each species has a slightly different kind of this enzyme that dictates how well it can metabolize the chemicals. A study conducted by (7) Licata (2012) concluded that different species of sea Lions have a higher level of hydroxylation which indicates a higher P45, and it is expressed as a protein that adds hydroxyl groups to the PCBs. This makes the chemicals more polar and water soluble and easier to break down and metabolize. Bio metabolism within species is also temperature dependent. The excretion rate increases with temperature and productivity of the species. When temperatures are lower, and energy is being used towards raising the body temperature to a comfortable level, metabolism cannot act as fast. PCBs are a detrimental input into our ecosystems due to their chemical properties and effects on apex predators through bioaccumulation. Chemistry can also be used as a method of destruction on these chemicals. Chemical means of destruction of PCBs can happen through glycols. Glycols have been known to degrade PCBs by displacing all or most of the present chlorine molecules. Although shown to be effective it would never work on a global scale, and could potentially introduce new chemicals into the environment.

Dichlorodiphenyltrichloroethane (DDTs).

Another chemical involved in the process of bioaccumulation of Ape predators are Dichlorodiphenyltrichloroethane (DDTs). This chemical is colorless, tasteless and was used in insecticides because of its favorable characteristic of high stability, such as PCBs.  DDT is another organochlorine pesticide that enters the marine world through water and air. The main cause of DDTs in the environment is because of agriculture land use. The use of this chemical has been banned since the 1970s yet we still see remnants because it is such a stable chemical with a half life of 15 years. DDTs affect the central nervous system of species and can also result in high levels of death among marine species. This chemical has a very high tenancy towards biomagnification and extremely high concentrations are found throughout the marine ecosystems, and throughout all components of the food web.  As study to test the Affects of this chemical on marine life was conducted by (10) Wolf (2017). The purpose of the study was to observe population decreases in the harbor porpoise. Although many considerations such as declining fish stocks and anthropogenic stressors were suggested, the main cause was high levels of contaminations found in species from an accidental capture. This study along with many others found for this paper suggested low concentrations of DDTs, yet very high PCB contamination. Although this is study area dependent, this could also be due to the ban on DDTs and the lowering concentrations of DDT in marine environments over the years. The mechanisms of transport into the environment are the same as discussed for PCBs, as well as the Metabolism being species and temperature dependent.

Both PCBs and DDTs enter the food web the same way. They enter in when a primary consumer eats food which has been contaminated, then a secondary consumer eats the primary and this continues on all the way up the food chain where the organism at the top, known as the Apex predator will have the highest levels due to biomagnification. The apex predators consume the most amounts and these chemicals accumulate in their bodies. All trophic levels are affected by both of these chemicals due to their chemical properties and they have a strong relationship with the higher trophic levels. The relationship shown is the higher the trophic level, the higher the concentration due to higher amounts of consumption. The concentration in dolphins is suggested to be 52,000,000 times more than the concentration of seawater due to this concept. (1) Ferkas (2017).


Polychlorinated biphenyls (PCBs)



 Dichlorodiphenyltrichloroethane (DDTs)



            Bioaccumulation can be described and better understood when using chemistry to back up the facts. Organic chemistry is important is many real-world scenarios because it is the building blocks of the situation or explanation to the problem. Knowing the chemistry behind situations such as this allows other scientists such as biologists, conservationists, and environmental scientists to solve problems. Although chemicals such as PCBs and DDTs are near impossible to remove from the atmosphere, our understanding of organic chemistry allowed us to define the problem. By defining the problem actions were taken to no longer expose our environment to these harsh chemicals.



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2.Geisz, H. N., Dickhut, R. M., Cochran, M. A., Fraser, W. R., & Ducklow, H. W. (2008). Melting glaciers: A probable source of DDT to the antarctic marine ecosystem. Environmental Science & Technology, 42(11), 3958. Retrieved from

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8.Marine biology; researchers from university of corse pascal paoli report new studies and findings in the area of marine biology trace element concentrations in the apex predator swordfish (xiphias gladius) from a mediterranean fishery and risk assessment for …]. (2017, Sep 15). Ecology, Environment & Conservation Retrieved from

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