Our polluted sea and disappearing marine life

by Emeritus Professor Upali Samarajeewa

(smrjee@gmail.com)

Many lists, figures and numbers could be seen in the public media on the toxic materials supposed to be in the containers of the wrecked ship. Some materials have been discharged to sea. More may be in containers. Experts seem to assume that all the oil in the ship got burned in the fire. Unfortunately, the numbers, volumes and interpretations keep on changing, creating more questions in the public mind than answers. Basically, there had been many chemicals, bulk of which would have got diluted and carried away by the currents reducing the potential threats. It accounts only for whatever that came out of the containers due to fire or other damages. What is intact, trapped and locked in the containers but soaked or washed away by the waves continuously would not be known or understood. We leave it to the ocean to decide the fate of its fauna and flora.

Simple calculations of the initially released figures of the quantity of micro-plastics, (which are less than 5 mm in size), and the number of bags containing them calculated with simple arithmetic do not tally mathematically. New concerns are arising on increasing numbers of turtle bodies and dead whales appearing in our shores. It may even beat the COVID 19 trend.

Leaving aside the soluble chemicals momentarily, the threat from micro-plastics appears to be on the increase, though what appeared on the beaches were removed efficiently – thanks to the armed forces, the public and others. Research on micro-plastics recognizes that they behave differently from the normal plastic waste that goes into the sea through flowing rivers and other pathways. In general, the micro-plastics are said to be passing through the gut of marine fish, provided the constrictions in the passage of the gut are bigger than the pieces of plastics. However, it is not logical to expect the passage through the gut as an empty tube with no constrictions and valves allowing free flow. Available research suggests only those plastics smaller than 486 micro-meters could be absorbed through the epithelium of the gut in fish. Thus, there is an element of safety in considering human exposure through edible components of fish, if adequate care is taken to remove the fish guts prior to cooking. It is also known that a certain amount of micro-plastic can get trapped in the gills of fish, obstructing flow of sea water and hence the availability of oxygen.

Small fish such as sprats, and crustaceans like prawns and crabs are part of our diet. Sprats may or may not swallow microplastics, but the risk of transferring microplastics to human food remains high through small fish as gut contents remain intact at cooking. The feeding habits of crustaceans allow intake of much more plastics and retain more than 95% of what they ingest in their soft tissues, without digestion.

The unusual numbers of turtle bodies appearing in shore require increased attention, as the bodies may serve as indicators of what is happening in the sea and what is to be expected. It is scientifically shown that the turtles tend to misidentify plastics as food, due to a specific sensory reason. Plastics smells like foods to turtles. This results in turtles chasing behind the micro-plastics to satisfy their hunger, till the guts get packed up with micro-plastics. The ship also had carried crude synthetic rubber. The actual physical form of this rubber is not known. Rubber is heavily toxic to turtles. All the dead turtle bodies have been sent for analysis by the Government Analysts or for postmortem by the Veterinarians adhering strictly to legal requirements. Those reports may appear in files. Why not somebody with authority, split open the guts of the turtles and examine the contents of rubber, new micro-plastic beads from the ship and old plastics of different shapes to understand the actual cause of deaths. There are enough degree holders with zoology knowledge in various institutions. They possess experience in dissecting rats, cockroaches, and even small sharks. It is time for them to come out and help the more advanced scientists providing basic clues. The responsibility lies in the institutions, authorities and agencies serving public good. It is established that consumption of 14 pieces of plastics accounts for LD50 for turtles (The 50% lethal dose for a turtle to die). Counting beyond 14 is no daunting task for a population with high literacy rate. Rapid results and appropriate approaches could generate information fast to avoid more assumptions and guesses.

The microplastics released from the ship are of tiny size with a high absorptive surface area. The micro-plastics increase their absorptive capacity over months, as tiny pores appear on the surface during decay. These new plastic pieces possess high ability to adsorb organic molecules and concentrate them on the surface. Marine environment is full of toxic organic pollutants discharged from the rivers and through other human activities. The ship itself may have added loads of non-fuel oils as indicated in the information available to the public. These oils and some other spillovers from the decks would have been adsorbed by the micro-plastics. It is shown scientifically that the substances adsorbed by the microplastics get desorbed in guts of marine animals, due to acidity and enzymatic digestive actions, leaving the plastics free for another round of absorption once they are discharged back to the sea. It provides a mechanism for continuous intoxication of marine fauna.

It appears there are adequate stocks of common salt for consumption for one year. As the load of micro-plastics increase in the sea, and as they break down slowly into smaller particles there arise a possibility of increased numbers of plastic particles passing through the current sea water filtering mechanisms. The microplastics may serve as nuclei around which the salt could crystallize. In the long run it may be appropriate to establish more effective filtering of sea and examine sea water at least microscopically as a safety mechanism.

It is also reported that there was lead, copper and aluminium in recognizable quantities in the ship. They may continue to dissolve slowly into the sea water. Old plastics pollutants already in the sea could attract the charged metallic components effectively creating a new pathway for transmitting them into marine bodies, plant, or animal.

The shelf life of a plastic shopping bags in our marine environment with plenty of sunlight, is around 2 years; the equivalent for the micro-plastic beads that appeared in our shores is 800 – 1200 years. This brings in a durable mechanism to circulate potential toxic materials into guts of marine fish for many years.

There is no direct research to recognize threats to human life, due to accumulation of plastics in the body. Experiments carried out with tissue cells from the human body cultivated under laboratory conditions, have not demonstrated any toxicities to cells by micro-plastics. The threat of micro-plastics serving as carriers of harmful ingredients to human body cannot be ruled out.

The public has concerns about the safety of fish consumption. With a reasonable degree of responsibility, it could be said that the food safety threat from consumption of big fish is low provided they have not died before being caught. The consumption of small fish with the guts poses a risk. The risk tends to be higher with marine fauna having outer shells, prawns, crabs etc. – the crustaceans. At this moment, clear scientific information based on post-mortem findings of turtles can throw a lot of light on the threats we may be facing though marine food. If the flesh of turtles shows high levels of heavy metals, there is a need to be cautious. If the flesh is free of unusual chemical constituents, but the guts are packed with micro-plastics the threat to human food chain lies more with plastics and not the chemicals released from the ship. It is up to the scientific authorities to discover the reality.