Marine life in a South African bay is teeming with chemical pollutants


The adage “out of sight, out of mind” has long summed up the attitude of humans towards the dumping of personal and industrial waste. In a 1974 Scientific American article, oceanographer Willard Bascom wrote that “the ocean is the plausible place where man can dispose of some of his waste”. If done “thoughtfully”, he continued, “it will cause no harm to marine life”.

But it was not done thoughtfully. Earth’s oceans aren’t just full of plastics: they’re also clogged with drugs, antibiotics, sanitizers, household chemicals, and pesticides, among other products. This isn’t just bad news for the environment and marine life. It also harms humans. Compounds in some of these underrated products cause feminization and decrease sperm quality. They can also cause sexual abnormalities and reproductive disorders in marine animals and humans, as well as cause persistent antibiotic resistance and endocrine disruption.

In a recent study in South Africa, we tested for the presence of eight selected pharmaceutical and personal care products in the marine environment of False Bay in Cape Town. False Bay is 30 km wide, located between Cape Hangklip and the Cape Peninsula in South Africa on the perimeter of Cape Town, a city with a population of nearly 4.6 million.

Our findings were disturbing. We tested seawater itself, as well as sediments, algae and five marine invertebrates: limpets, mussels, sea urchins, sea snails and starfish. Many compounds were found in the different species. These included diclofenac, a widely prescribed anti-inflammatory drug, and the antibiotic sulfamethoxazole, which can promote antibiotic resistance in the many faecal microorganisms that contaminate seawater through improperly treated sewage effluent. . Cape Town released a report showing significant faecal contamination of the peninsula’s coastline.

When humans eat fish, mussels and other foods contaminated with antibiotics, residual antibiotics can make bacterial pathogens resistant. Resistant bacteria do not respond to standard antibiotics and can grow unchecked. This means that the most important treatment options for infections are rendered useless.

These findings, which echo findings from our previous studies in two other Cape Town marine environments, Camps Bay and Sea Point, point to major flaws in the city’s wastewater treatment plants. Urgent action is needed to address these issues and limit the many different chemicals and pollutants dumped into marine environments.

This multi-source contamination is a global concern. A recent US study, for example, found 104 commonly prescribed pharmaceuticals in a popular food fish.

Grim discoveries

In our study of False Bay, we found the presence of many pharmaceuticals and other compounds. Their concentrations varied considerably between the eight sampling sites. This could be because the different species found at the sites have different abilities to absorb and metabolize these compounds. Sites also had different contaminant profiles due to mixing of ocean currents or proximity to discharged effluents.

Read more: What whales and dolphins can tell us about the health of our oceans

Limpets, seashells of various sizes and colors that cling to rocks, were found to have the highest concentrations of these compounds compared to edible organisms such as mussels and sea urchins. Although limpets are not an edible species, this knowledge is invaluable: limpets could be used as sentinel organisms to monitor pollution in and around the ocean – a kind of “canary in the coal mine”.

In this study, as in our previous research, pharmaceuticals, pesticides, industrial chemicals, and personal care products were most often found at low concentrations in seawater samples. high were detected in the samples of marine species and algae. This can cause serious damage over time, slowly killing sea creatures and affecting the biodiversity of the area.

We also studied samples of four common fish species that are often consumed locally, such as snoek and bonito (a species of tuna). We found even higher levels of these chemicals in their flesh. This included four types of pesticides, eight different pharmaceuticals and five different perfluorinated compounds, all called “persistent organic pollutants”. They do not degrade quickly, so they stay in the environment for a long time.

Wastewater treatment plant shortcomings

The sewage that causes this widespread pollution is not simply dumped into the ocean. Cape Town has 17 sewage treatment or sewerage facilities and six smaller facilities spread across the Cape Peninsula. Wastewater treatment plants are designed to clean water enough for it to be discharged safely into rivers, canals, the ocean or other bodies of water.

But these measures, according to our findings, may not keep up with the city’s rapid population growth and the growing number of pharmaceuticals and other chemicals produced and consumed.

Ideally, wastewater should go through four stages of treatment:

  • pre-treatment to remove very large solid materials

  • primary treatment for the removal of small solids as well as fats, greases and oils

  • secondary treatment for wastewater disinfection

  • tertiary treatment for subsequent “polishing” and further removal of chemical compounds and microorganisms.

In reality, there are few such tertiary treatment stages in Cape Town’s currently inadequate sewage treatment facilities, as regulations governing the quality of effluent discharged from sewage treatment plants are not sufficiently strict. This allows poorly treated effluent to be discharged – and many microbes, as well as chemical compounds and pharmaceutical pollutants, escape and are discharged directly into the oceans via rivers.

Read more: We found traces of drugs in a dam that supplies the capital of Nigeria

There are also three “marine discharge pipes” which pump raw sewage – filtering only large items – directly from the toilets and discharge into the ocean via underwater pipes. As our studies show, microbial and chemical contamination from faeces is now widespread across the peninsula.

Discharge of untreated sewage through marine outfalls should be avoided. Wastewater treatment plants should be upgraded to include tertiary stages. Regulations governing effluent quality need to be stricter – and need to be monitored more carefully for chemical content.

The ocean is part of Cape Town’s identity. It is a lifeline for many in the fishing industry, which is a multi-billion rand industry. City officials must act urgently to ensure not only that marine life can thrive, but that human health is not compromised by what is dumped into the oceans.


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