Twenty years ago, scientist Dr. Jamie Bacon began seeing the first deformities in Bermuda’s toads. The toads she observed may have had a limb missing, or an extra limb, or even only one eye. These deformities were numerous and impractical for the toad, causing them to be slower and more vulnerable to predation. While the deformities of the introduced marine toad may feel inconsequential and far away from us, the dark future they foreshadow cannot be ignored.
Toads are bio-indicators – their biology causes them to be indicative of the ecosystem’s wider health. Toads have permeable skin, which they must keep moist in order to breathe, but in polluted environments, toads are also forced to soak up large numbers of toxins. Their deformities, which are a direct result of polluted water, paint a worrying picture of pollution levels on island. While the effects of pollution on other vertebrates are great, they may not always be visible in the same way, or with the same immediacy, as toad deformities. The toad is effectively a clean sponge, which, after spending time in a polluted pond, emerges caked in tar and sludge. They can show us, in radioactive-superhero-esque ways, just how much damage our environment is sustaining.
Dr. Bacon’s research began as an investigation into the health of the wetlands in Bermuda, but as the scientists discovered the extent of the damage, it quickly became a full time job. At first, they hypothesized that perhaps parasites were the culprit, causing alarming deformities in toads. The parasites, which had affected amphibians in some parts of the U.S., could infect the tissues of toads and disrupt the formation of a limb. Despite sending off dozens of toadlets to be tested, Dr. Bacon did not find a single parasite.
Soon, they discovered that the problem was much more worrying, and much more difficult to eradicate. The researchers quickly found high levels of polycyclic aromatic hydrocarbons (PAHs) present in the ponds, which are harmful pollutants resulting from the combustion of fossil fuels. PAHs can be produced naturally by forest fires or volcanoes, but the reason for their now-toxic levels in the environment is due to human activity.
The toxins are released by burning coal, oil, and gasoline, and pollute the air with fumes, or bind with liquids to pollute waterways. The researchers also found a high concentration of heavy metals in pond water, and began conducting experiments to see what conditions gave the frogs the most deformities.
The toad’s life cycle is intertwined with water, with the eggs laid in ponds, to the rearing of aquatic tadpoles, and the adult toad’s need to keep its skin wet. As a result, there were multiple opportunities for PAHs in water to infect the toad’s tissues. “The tadpoles are getting it from their ponds, but mom can offload some of the contaminants by putting them in her eggs,” Dr. Bacon notes.
When the researchers began doing necropsies in adults, they found even more alarming internal deformities, including segmented ovaries and testes, and liver pathologies. Dr. Bacon recounted that red eared slider terrapins began to show secondary sex characteristics – she would identify what she thought was a male terrapin, only for the lab to find that it had immature ovaries inside. “This pointed to endocrine disruption,” Dr. Bacon said, that the PAH levels in the water were actually affecting hormone levels. The fact that hormone abnormalities were found in killifish and red-eared sliders as well as toads, was alarming for Dr. Bacon. “You had three classes of vertebrates all showing similar effects,” indicating a problem much more widespread and serious than first anticipated. “We haven’t even looked at birds,” she said, gravely.
The scientists conducted a sediment spiking study, where they reared tadpoles in a variety of conditions, in order to determine how each factor affected the toads. These studies revealed that it was the heavy metals that produced more of the facial deformities and suppressed the immune system, while it was the PAHs that cause the limb deformities, and the endocrine disruption, which was the most worrying effect of all.
They showed that metals and PAHs combined in pond ecosystems in Bermuda to cause these adverse effects by rearing tadpoles in polluted ponds in predator exclusion cages. “Dragonfly larvae chomp off piece of the tadpoles,” Dr. Bacon said, and this variable had to be eliminated so that the absence of a limb could be attributed definitely to water quality.
Dr. Bacon also conducted studies on fish reproduction to see how it was affected by polluted sediment and water. Lab reared, healthy fish were put into two conditions – Bermudian pond sediment, or clean sand, and observed for how many eggs they would lay over 21 days. “They laid 9000 eggs over safe sand, and 2000 in our pond sediment,” Dr. Bacon said disappointedly.
Dr. Bacon speaks about her findings gravely, but as if she has been over them a million times before. Though the findings were alarming, and widespread, little was done by the government to eliminate pollutants at the source. “You get to the point after eleven years – it’s not going away,” she explains, “We focused on what we could do about it.”
Bacteria are hugely important for ponds, as they act to break down the dead and unused organic material at the bottom of ponds into something that primary producers, like plants and plankton, can use. Recently, scientists have discovered that a naphthalene-eating bacterium has developed to degrade PAH molecules, thus reducing their toxicity. “Ours were starving for oxygen,” Dr. Bacon recalls, and remediation tactics focused on reintroducing oxygen to pond habitats in Bermuda.
Ponds are used to anoxic conditions because their lack of wave action ensures the water will become stagnant. However, humans can also intensify these conditions by eutrification – the overloading of nutrients in ponds, usually via agriculture run-off, or by dumping sewage. These nutrients cause staggering algal blooms, followed by massive algal die-off, and their decomposition deprives the water of oxygen.
When oxygen becomes depleted, bacteria are forced to metabolise first nitrate, and then sulfate. This results in the production of hydrogen sulfide during the bacteria’s chemical reactions, which is toxic to most biota and is the cause of the classic “rotten egg” smell surrounding ponds.
When oxygen is reintroduced, the ecosystem has the chance to right itself. Dr. Bacon explains that there was a tenuous balance to be reached in interfering with the populations of PAH-degrading bacteria in our ponds. Interfering by adding more bacteria, or more food for the bacteria, was risky because it had the chance to disrupt the ecosystem in unforeseeable ways. “We could get enough effect with oxygen that let them reproduce more,” she said, meaning the scientists would have to alter as little as possible.
The remediation methods were not as simple as ‘cleaning up the ponds’ – they had to work within the context of pond ecosystems and manage to overcome any adverse affects. To test out their remediation efforts, the team installed air stones in Cloverdale pond, a private nature reserve near Collector’s Hill. “It had terrible effects, but no protected species like killifish or diamondbacks, so if we did anything toxic, it wouldn’t harm a protected species.” The remediation effects were tremendous, and after only a year of the air stones being present, hydrocarbons went down to undetectable levels.
“We did the same fish laying experiment, and the fish laid more in the Cloverdale sediment than in the clean sand,” Dr. Bacon said. It was amazing how quickly the pond environment could turn around, and the harmful effects of PAHs could be reversed. It was undoubtedly a triumphant time for the project, but repairing the wetlands did not target pollution at its source. While the researchers could work to restore the pond habitats that were becoming so altered as to affect three classes of vertebrates with toxins, the ponds were simply a microcosm to show pollution’s effects on the island as a whole.
“Cloverdale will probably get recontaminated,” Dr. Bacon warned. Road run-off is a constant problem, and it increases every day. The most efficient way to measure the effects of road run off is to look in soakaways, the large basins beside Bermuda’s roads with long, thin cement planks on top of them, or any drain with a grate on top of it. Dr. Bacon found that 10-15% of the contaminant load in soakaways leeches into ponds. “Some of those soakaways, it’s been ten years since they’ve been cleaned,” she says, and the accumulation of road run off in them is astonishing.
Next, the project focused on Evan’s Pond, which is home to a genetically unique species of killifish, and they are currently focusing on South Pond in Mid-Ocean Golf Course, which is an important feeding ground for the threatened diamondback terrapin. “We need to stop burning fossil fuels. This is a temporary measure,” Dr. Bacon said of the remediation efforts. Though it is necessary to restore the health of some ponds immediately for the sake of the unique species that may be lost, remediation efforts are ultimately fighting a losing battle against industries that continue to produce contaminants.
PAHs affect every facet of our atmosphere and environment, and it was no surprise that the project eventually focused on their ramifications for humans. In water tank studies, similar levels of metals and hydrocarbons were found, which could cause adverse health effects for humans. Furthermore, PAHs are a known carcinogen to humans.
“Pollution now is not some esoteric thing, ‘yeah at some point it can cause effects,’ no,” Dr. Bacon said. The effects of pollution are severe, and can be seen in our ponds as much as in our own water supplies. “We have a dubious distinction, we are the worst site in the world for deformities and endocrine disruptions,” Dr. Bacon reports, after discussing the results of her research at various international conferences. “It’s a fragile environment, we have already affected it tremendously. We need to look at what we’re doing because potentially we’re not immune to the effects.”
Drastic infrastructure overhaul is necessary to stop pollutants at their source. In particular, Dr. Bacon noted that we don’t have tight enough restrictions on car emissions, and that “if we could switch to electric cars, we’d be a lot better off. We’d be the perfect island to do it.” She envisions a sustainable island, and recalls that a study on wave power found that it would be a viable option for powering the entire island, but that the technology was not available yet. She wishes for the government to provide financial incentives for people who are willing to switch to solar or wind power, or to electric vehicles, because the cost to import them is incredibly high.
Dr. Bacon also recommended various practices at the individual level that people could employ in their daily lives to help the environment. She recommended reducing one’s environmental impact by living sustainably, and cutting down on toxins like pesticides that are used in the garden.
In order to help toads in particular, Dr. Bacon emphasized that many ponds have become too salty, or to polluted for them to breed. She recommended that people build toad habitats in their own gardens and maintain them.
Though toads are an introduced species, Dr. Bacon believes they are a successful environmental control and absolutely worth saving. “I have people come in begging me to get toads in their yard,” Dr. Bacon said, because they are so successful at keeping cockroaches and centipedes at bay. Furthermore, they are the only amphibian on island, so there’s nothing for them to outcompete.
Dr. Bacon noted that there are many environmental allies that will do anything to create habitats for toads in their own gardens, but that many other people in Bermuda are simply terrified of them. “I’ve heard the stories where a woman comes home, and if there’s a toad between where she parks her car and the front door, they go stay at somebody else’s house.” Dr. Bacon has dedicated much of her time to education about toads in order to change people’s view of the amphibians. In addition, she hopes to see the use of pesticides and insecticide sprays decrease as attitudes towards toads become more positive.