I remember my mother refusing to get me a turtle as a pet after hearing that they could transmit salmonella. (She probably had no idea at the time that they can also transmit Hepatitis B.)
She also told me not to touch the ducks in the neighborhood lake. She probably had heard that they can host the alpha herpesvirus, which caused high mortality rates in ducks, geese and swans after European flocks introduced it to Long Island, New York, and throughout the Northeast U.S. in the late 1960s.
Over the past 50 years, these health threats have spread worldwide and become normalized in the public mind. There is emerging evidence now that turtles, ducks and geese have adapted to these diseases that they carry and now spread antibiotic-resistant bacteria. As an aquatic expert, this keeps me up at night — especially considering the possibility that these bacterial strains could transfer their resistance to water algae.
From the Ground up
Ducks and turtles are as ubiquitous to water environments as shells are to a beach. These water species excrete waste with bacteria, which settle into soil that is already laced with antibiotic runoff from human activity.
This long-term buildup can become a habitat for new generations of bacteria. In a 2017 study of a China duck meat farm, the deeper the excrement layers became (and the longer these layers went without removal), the more numerous the antibiotic-resistant bacterial species became. These bacteria also developed resistance to zinc, copper and cadmium. As copper is the primary element used to control algae and cyanobacteria in bodies of water, these conditions led to an outbreak of harmful algae blooms (HABs) and cyanobacteria growth.
It is well known that HABs can be toxic and quite common when heat and nutrient loading are abundant and ecosystem diversity is low. This begs the question — could algae learn antibiotic and copper resistance from bacteria?
Algae are in every environment on earth, having emerged as a simpler species about 1.7 billion years ago. Bacteria existed a couple of billion years before that, and cyanobacteria — the first known life on the planet — preceded bacteria by about a billion years. Clearly, these species learned (or stole) abilities from each other over time, continuing to evolve to present day.
Considering its track record, it would seem very unlikely that this adaptive behavior has suddenly come to a stop. More likely, these microorganisms have been reacting to human activity, feeding on modern waste and adapting to our chemicals, all while competing with and learning from each another. After all, microorganisms have always comprised the vast majority of biomass; humans, in contrast, are a more recent experiment.
Many aquatic companies that treat algae will promise to eradicate the problem. In reality, algae colonies cannot be completely eliminated — only limited in size and reproduction by using proper tools and procedures. Not only are there immense varieties of algae and bacteria that have adapted to every environment, but each cell of a species also has the capability to create a daughter with new characteristics. If you thought human teenage girls were tough, they’ve got nothing on microorganisms! There are about 1 trillion species of microbes on Earth, and 99.99% of them have yet to be classified. Clearly, microorganisms have no problem evolving through adaptation, with newer species learning to consume the most abundant form of nutrients and resist many of the threats that otherwise limited their mother cells.
Once we accept the possibility of an interspecies exchange of resistance, what is the probability that a new algae strain would move out of its home pond? Consider that the same bird groups that excrete large amounts of waste also move from lake to lake. Birds tend to visit all the water features in their territory, even if they have a favorite spot. Turtles have the capacity to travel as well. The wind can also play a large role in transporting bacteria and other microorganisms over long distances. Empirically, the entire earth is covered by microorganisms that are well suited to each set of conditions. Survival of the fittest is the rule, so there is every reason to believe that once a species can resist local defenses, it can and will find a way to spread to every nutrient source available to it.
Aquatic experts rely on a limited number of products to control algae. When subtler treatments fail, they ultimately turn to copper as the active control ingredient. Although antibiotic resistance is a problem all its own, it is algae’s resistance to copper that presents global concerns.
What Can Be Done?
Is this an inevitable response of Mother Nature to human activity? Perhaps, but there are certain steps we can take to curb this growing problem. The most obvious step is to reduce human runoff into streams and lakes, but this task is beyond the scope of most aquatic managers.
One effective thing we can do is clean out the muck layers from our lakes and ponds; however, it isn’t cheap, and it can commonly get delayed for years and even decades for budgetary and permitting reasons.
One could consider trying to control bird and turtle populations, but this can also be difficult, both socially and politically. First of all, reducing bird and turtle populations runs into regulatory issues that have nothing to do with the Endangered Species Act of 1973. Rather, they stem from public opinion. Add to it a costly, complicated permitting process and a potential public relations nightmare, and it easily becomes the bane of property managers and municipalities. In many cases, this very issue becomes the final straw that defeats an otherwise permitted plan. For example, there is a property in San Francisco that requires humane fish euthanizing, beginning with a gentle capture, then freezing, and finally a chemical soft wash. After many years, they are still out looking for a contractor.
Most water features in the United States are also decades beyond their lifespan for muck removal. This delay in cleaning exacerbates and encourages the biological risks, while also limiting overall water health.
Being an alarmist in no way benefits a professional discussion or any form of governance. Water management experts rely on their decades of experience and knowledge of each property to make recommendations. However, recent events have demonstrated how quickly the status quo can change. Specifically, our assumptions about safety can quickly become obsolete.
In 1967, Avian Infectious Bronchitis Virus was studied as a crossover vector for human bronchitis. (Interestingly enough, this was the same year that the flocks of ducks were found dead in Long Island.) Today, we may be ignoring signs of a larger problem, where algae could incorporate antibiotic and copper resistance from bacteria and vector it through the birds and turtles that densely populate neighborhood water features.
Even if we do recognize the signs, our hands likely and effectively remain tied by our sentiment for these adorable creatures, many of which we continue to encourage to live in and around our underserved bodies of water.