The buildup of anthropogenic debris in marine environments over the past few decades has drawn a considerable amount of attention due to its negative impact on marine wildlife organisms as well as the environment. Plastics has become a critical asset for humanity however, if not disposed properly can lead to ocean pollution and toxification. About 5.25 trillion pieces of plastic debris in the ocean and due to plastics high durability and low disintegration rate, a significant amount of discarded plastics are accumulating as debris in oceans and landfills which indicates that the current use of plastics is not sustainable.
Marine debris interaction has been reported as one of the most dangerous threats for marine organism due to ingestion, entanglement, and smothering. However plastic ingestion was the main study of these experiments due to the more serious consequences such as physical damages to the digestive tract, impairment of reproduction, endocrine disruptions drowning and death.
Over one million marine mammals and seabirds die every year due to the over pollution in oceans.
It has been estimated that 14 billion pounds of garbage have been dumped into the ocean every year. Many sea creatures are victims of marine debris such as turtles, sharks as well as filter feeding zooplankton and shrimps. Degradation of sea turtle habitats due to ocean pollution is posing a serious threat to their population. Both immediate harm from direct contact as well as build up in tissues over time leads to decrease in health and ultimately death.
Microplastics are also found in surface water and tend to be more abundant than larger plastics.
Microplastics are smaller sized plastics of particles with less than 5mm which are derived from large plastic items. Many industrial cleaners and personal care products are composed of microplastics which usually end up in sea water.
There were several studies done on different marine organisms that illustrated the effects of ingestion of anthropogenic plastic debris on the digestive and the threat it has on their survival. The aim of the first study was to study the effects of anthropogenic debris ingestion by the green turtles in different life stages in the uruguayan waters through evaluating internal organ damage of turtles in a time span of eight years. There were two hypothesis that were being tested in this experiment. One was that juvenile green turtles would increase debris intake due to specific dietary shifts as they age. Other being, turtles would decrease debris intake when recruit into coastal habitats. The effects were examined based on the number of green turtle mortality in the specific location and time period. The debris found were numbered and categorized based on frequency or occurrence, relative weight, volume and number of items found. In this study microplastics were not considered. The experiment resulted in the foundation of 96 dead green turtles with 70% debris found in the guts during analyzation of internal organs. With respect to turtle size and debris ingestion, it was found that a higher frequency of occurrence of debris was in the smaller and juvenile turtles which lead to green turtle vulnerability. Direct mortality was seen due to perforation and abrasions which were produced through blockage of digestive tract.
Additional studies were done on another endangered species, blue sharks. The blue shark is a oceanic and pelagic species found in the mediterranean sea. The blue shark migrates vast distances of water for feeding and reproduction, therefore, it faces various areas with distinct species. The aim of this study was to also examine plastic ingestion in blue sharks from the north western mediterranean through analyzing the stomach contents and quantifying the litter ingested. The study was done by collecting 139 blue sharks from the year 1999 to 2015 in the offshore area of the mediterranean sea. The total length, weight and sex of the sharks were then measured and recorded. After necropsy, a microscope was used to identify the collected stomach content. The dried plastic items were then analyzed using the spectroscopy technique to find the poly composition of the plastic and grouped. The ingested plastics collected were grouped according to characteristics of total plastics items, plastic size and lastly plastic color. The experiment resulted in polyethylene and polypropylene being the most abundant. Regarding size, mesoplastics were predominant in both juvenile and adult sharks. Lastley, the plastic debris color tended to vary due to sharks opportunistic feeding strategy.
A further study was done on ingestion of polystyrene microplastics in marine life brine shrimp, artemia parthenogenica. The study demonstrated the toxic effects of microplastic ingestion specifically in filter feeders. The purpose of the study was to quantify the lowest concentration of polystyrene microsphere where ingestion could be seen at the two time periods of 24 hours and 14 days as well as examine the effects of microsphere exposure on the intestinal epithelial cells. Subsequently, when the artemia were exposed to the microspheres, regarding concentration, it was concluded that it was environmentally relevant as well as needed further research to be determined specifically. However, the pollutant lead to change in morphological appearance of digestive tract epithelial cells as wells as disordered microvilli in intestine.
The last study was conducted on the effects of microplastic exposure on growth and development of crepidula onyx. In this experiment the purpose was to expose the C. onyx larvae to different concentrations of microplastic and measure the effects it has on the development. It was shown that at high concentration, larvae that were fed micro-PS resulted in slower growth compared to the control group. All in all, the multiple studies discussed, provide enough evidence to illustrate the significant impact of plastic within our ecosystem among different trophic levels. Unfortunately, as the population grows, the demand for the use of plastic increases as well. However, there are many ways to decrease the usage of plastics by starting with reduce, reuse and recycle as well as using reusable straws, cloth bags instead of plastic and decreasing littering. As a population, it is in our hands to make a difference by making small changes within our daily lifestyle.