To check the impact untreated water had on small marine creatures, researchers have found that shrimp-like creatures living in the the south coast of England having 70 per cent less sperm than any other lesser polluted location in the world. In fact, the creatures who lived in the survey area were six times less fertile, in comparison to those living in cleaner waters.
The study, which was recently published in Aquatic Toxicology, reiterates the findings from studies on other creatures and humans. The researchers also believe the study will feed into wider studies on male fertility.
"We normally study the effect of chemicals on species after the water has been treated. The shrimp that we have tested are often in untreated water. The study site suffers from storm water surges, which are likely to become more common with climate change," says Professor Alex Ford, professor of Biology at University of Portsmouth, who lead the research work.
"This means that the creatures could be exposed to lots of different contaminants via sewage, historical landfills, and legacy chemicals such as those in antifoulting paints. There is a direct relationship between the incidence of high rainfall events and in the levels of untreated sewage," he added
Professor Ford describes the shrimp as "the canary in the mine" - concerned that the plight of the shrimp is only just the tip of the iceberg in terms of fertility problems in male creatures, both great and small. "It is thought that some male fertility problems are related to pollution," said Professor Ford.
Most male fertility research has historically focused on vertebrate species, and little is known about the effects of pollution on invertebrate fertility, especially the amphipods at the bottom of the food chain.
In fact, researchers at University of Portsmouth started observing little shrimp with very low sperm counts in nearby Langstone Harbour, a decade ago. Surprised by such a result they decided to monitor the animals over a decade's time. When the pandemic struck and researchers couldn't do lab-based research, one of the University's PhD student Marina Tenorio Botelho was given the task of data mining the decade's worth of statistics. Her routine study uncovered a worrying reality that these animals have been having consistently low sperm similar to those in areas that are industrially contaminated.
Professor Ford explains that other marine creatures are also suffering. "We know that pollutants are affecting male fertility levels of all species. Killer whales around our coasts are contaminated with so many pollutants that some can't reproduce. Recent studies have also suggested that harbour porpoises contaminated with highly toxic industrial compounds, known as polychlorinated biphenyls (PCBs), have smaller testes."
This impact can be seen in humans as well. Researchers have been looking at worldwide declines in sperm counts of humans over the past 50 years, said Professor Ford. "Research has shown that in some countries, a boy born today will have half the sperm count of his grandfather, and there are fears boys are getting critically close to being infertile," he added.
Meanwhile, female shrimp are producing fewer numbers of eggs, and appear in low densities in the same waters, reveals Botelho's research. "It suggests that because male shrimps' capacity to fertilize females is compromised, the females in turn have fewer eggs," she said.