Environment Pollution Significantly Harms The Species Of Dolphins
Dolphins are lovely and smart animals, but the species of dolphin worldwide are facing a significant threat. According to Whale and Dolphin Conservation (WDC) (n. d. ), human activities influence approximately 40 percent of marine systems and every area of the sea. In the eastern coast of the U. S. , the death of about three thousand bottlenose dolphins is observed from 1987 to 1988. We have to pay close attention to this issue so that dolphins would not die out and species diversity could be preserved. Actually, environmental pollution is an important reason why dolphin populations dramatically reduces.
Dolphins populations are significantly hurt by environmental pollution due to three major reasons. First, dolphins are easily hurtful by chemical pollution because of bioaccumulation in which damage dolphins' body systems. Second, noise pollution impairs dolphins' health and change their normal behaviors. Third, marine debris threat dolphins' life since dolphins may accidentally eat litters or be entangled by packaging. At the same time, there seems to an argument about whether environment pollutions extremely harm dolphins. Some people argue that some studies contain limitations and the data are insufficient to support the position that dolphins are significantly hurt by environmental pollutions. However, environmental pollutions have more clearly negative impacts on dolphins. One of the direct effects is that noise forces dolphins to consume more energy. Also, environmental pollution pollutes dolphins' habitats and kill smaller marine animals that could lead to the short of food for dolphins.
First of all, chemical pollutions including oils spills and polluted water have the detrimental effect on dolphins' health. With the rapid development of industry, increasing industrial accidents happen and result in many serious consequences. Pitchford et al. (2018) study the influence of the huge 2011 oil spill in the Gulf of Mexico, and they find that the large number of bottlenose dolphins' death is related to the Deepwater Horizon oil spill (p. 14). In other words, dolphins are unable to completely avoid the area of oil slick, and sometimes they indeed swim into floating oil. There is a chance that the poisonous oil will enter dolphins' spiracles and mouths if they are encompassed by floating oil. What is more, Durante et al. (2016) believe that polluted prey has an adverse impact on dolphins' health since toxins will be accumulated in dolphins' bodies (p. 358). Persistent Organic Pollutants (POPs) are perilous chemicals that released by industrial production and they are unlikely to break down in a short time. Marine animals will die if they absorb POPs at a certain level, and the amount of POPs in the ocean is rather huge. The majority of dolphins are at the top of food chains naturally, and so they are the ending point for POPs (Durante et al. , 2016, P. 353). To be more precise, plankton absorbs PCBs from the environment, and small fish eat plankton to survive. A lot of small fish are eaten by large fish in their life, and dolphins eat plenty of large fish over their lifetime to survive. Finally, POPs from lots of smaller marine organism is absorbed by dolphins. So, bioaccumulation caused by chemical pollution is really a big issue.
In fact, anthropogenic chemical pollutant have the more negative influence on dolphins than other animals. Rage et al. (2008) provide convincing evidence that the species of dolphin are not good at coping with pollutions like POPs because there are scarcely any enzymes in their bodies to decompose hazardous chemical components. (P. 472). Consequently, dolphins’ reproductive and immune systems are likely weakened due to the damage of chemical pollution such as POPs. The damage to dolphins' reproductive systems can cause serious issues. More specifically, a large ratio of POPs may be passed by female dolphins to their first babies via womb or milk, which is possibly fatal to offspring (Durante et al. , 2016, P. 354). In addition, the problems related to injured immune systems are also severe. For example, the massive death of dolphins since the 20th century could be caused by virus transmission the from animals to animals. (Rage et al. , 2008, P. 473). Thus, chemical pollutions put dolphins in especial danger because toxins and poisons from dangerous chemicals severely injure dolphins' health.
Other than chemical pollution, noise also has a seriously negative impact on dolphin populations. Dolphins live in the ocean where they use sound to communicate and look for direction. Nonetheless, human activities such as natural resources exploration, the operation of ships and military maneuvers in the sea have made a very high level of noise, which puts dolphins in risk. There are plenty of studies from scientific literature illustrating the damage of noise to dolphins. For instance, high-frequency and mid-frequency sonar from military vessels are recognized big worry for the health of marine mammals and they can lead to physical hurt or death to marine mammals like dolphins (Li et al. , 2014, P. 496). Likewise, dolphins with excessive stress levels caused by high-intensity sounds may even behave aggressively, which can result in physical injuries (Harris, 2017, p. 212). This evidence clearly show that noise pollution has an adverse effect on the species of dolphins.
Besides high-frequency and mid-frequency sonar, Harris discusses that low-frequency ocean noises also influence mammal behaviors. To be more precise, mammals will go away from their habitat or breeding place because of excessive noise, which is observed on the coast of Baja California, Mexico and increases the chance of illness and stranding ( Harris, 2017, p. 211). Similarly, Pitchford et al. (2018) claim that noise pollution will drive dolphins from important areas to them (p. 16). Basically, all noises made by humans influence extremely disrupt dolphins' life. Dolphins have to raise their voices since plenty of ships in the ocean make many noises. Dolphins change the frequency, duration or amplitude, or they simply repeat their calls several times. Yet, these actions really hurt dolphins' health (Holt, 2015, p. 1648). Furthermore, exposure to shipping noise in long periods could lead to temporary or permanent damage to dolphins' auditory system (Li et al. , 2014, P. 501). Auditory systems play an essential role in dolphins' daily life, and it is hard to imagine how should dolphins survive in the sea without a sensitive sense of hearing. Therefore, dolphins' lives are significantly impacted by noise pollution since noises alter dolphins' normal behaviors and harm their heath.
Dolphins are threatened by noise while the detrimental effects of marine debris on dolphins cannot be overlooked. Millions of tons of plastic garbage are dumped by people into the sea yearly worldwide (WDC, n. d. ) The oceans are polluted by countless man-made litters, which is quite risky to dolphins. When dolphins swim in coastal areas or along shorelines, marine litters containing plastic bags and other indecomposable substances can trap or choke them, young dolphins in particular (Pitchford et al. , 2018, p. 16). To put it another way, dolphins can suffer or die if they are entangled in plastic bags. Moreover, researchers have found that more and more dolphins eat marine debris accidentally. Bearzi et al. (2014) discuss that one of the known cause of dolphins' mortality is obstruction of the digestive system by ingesting plastic (P. 393). As a consequence, intestinal blockage, starvation, and inside damage are all possible. Similarly, Eo, Yeo, and Kwon (2013) explain that gastrointestinal foreign objects are a serious problem in cetaceans and dolphins (p. 251). For example, Eo et al. (2013) helped a male bottlenose dolphin to remove foreign objects from its forestomach, and they found that "The foreign bodies included a 10 × 3. 5 cm plastic tube, 4 ×2. 0 cm stainless steel pipe, brush, and concrete debris" (p. 251). Consequently, the species of dolphin are significant by man-made marine litters. Hence, marine debris as one of the chemical pollutions poses a real threat to dolphins' lives because serious issues such as suffocation, intestinal blockage, and internal injury are caused by ingestion of plastic litters and entanglement by packaging.
On the other hand, some individuals challenge that environmental pollutions do not have a extremely negative effect on dolphins because of two main reasons. First, lots of scientific studies about how environmental pollutions affect dolphins population are not optimal. For instance, some factors that would impact the results are not being quantified in the study of oil spills (Pitchford et al. , 2018, p. 16). Additionally, the statistics are not sufficient because such data are rather difficult to collect. Durante et al. (2016) write that there is solely a low number of samples available (P. 358 ). Follett, Genschel, and Hofmann (2014) say that reliable conclusions cannot be drawn based on inadequate data and limited knowledge although oil discharge leads to huge destruction (p. 130). Scientists have to examine the death of many animals to confirm the cases that animals died due to environmental pollutions (Follett et al. , 2014, p. 130). In other words, humans indeed do not have adequate information about how animals died is linked to environmental pollution since checking the actual cause of a large number of animals' death is quite challenging. Hence, the limitation of some scientific researches and the lack of data are the two reason why some individuals reject that dolphins are significantly harmed by environmental pollutions.
Nevertheless, there is compelling evidence demonstrating that environmental pollutions have negative impact on food chain and ecosystems. Follett et al. (2014) write that oil spills can grow bacteria and kill smaller marine animals that are the sources of food to dolphins although oil spills may not directly kill dolphin populations (p. 122). It means that environmental pollutions like oil spills obviously result in habitat destruction to dolphins as well as increase the risks that dolphins have diseases and lack food. Meanwhile, Holt et al. (2015) study a pair of bottlenose dolphins at the lab and conclude that the louder dolphins phonate, the more oxygen and energy they consume. Then Holt and her colleagues apply the uniform method to calculate how many extra calories dolphins in the wild have to get to compensating the extra consumption of energy, and they estimate dolphins need to obtain two extra calories for each two minutes (p. 1650). Though this extra metabolic cost is not large, the consumption of energy will become quite huge through accumulation over time. More importantly, not all dolphins are able to find sufficient foods, especially for juveniles and pregnant females. Thus, environmental pollutions indeed have an obviously dramatic effect on dolphins populations.
To conclude, environmental pollutions significantly harm the species of dolphins because of the three reasons. Chemical pollutions enable toxins and poisons enter dolphin's bodies and destroy their reproductive and immune systems. Through injuring dolphins' auditory system and disrupting the communication, dolphins' health is impaired by noise pollution, and dolphins' normal behaviors are changed by noise as well. Marine debris threat dolphins' life by raising the risk that dolphins ingest litters or be entangled by plastic bags, which leads to severely consequent problems such as obstruction of the digestive system and asphyxia. Each person, every organization, and all countries ought to should the responsibility to tackle environmental pollution and protect dolphins. Humans should take actions immediately before environmental pollutions result in more seriously irreversible damage to dolphins.
