Exposure to a common urban pollutant affects the survival and swimming behaviour of Creek Chub
Link to the Published Paper by Christopher Bunt & Bailey Jacobson
First published: 23 January 2021 in the Journal of Fish Biology
Dog waste is a ubiquitous world-wide runoff pollutant that increases bacteria and nutrient loading within urban waters. Despite the clear theoretical link that dog waste affects water quality and water quality affects fishes, the impact of dog feces on urban fish populations has never been directly studied. This is surprising given the recent flux of studies that indicate dog waste is a significant source of environmental pollution. As such, despite the potentially direct ecological and economic repercussions, this study showed for the first time the impact dog waste has on fish survival, fish behaviour and its real-world relevance.
As the human population continues to increase and urbanize, so too does the pet population and at an even greater rate, further exacerbated by the COVID pandemic. It is thus unsurprising that often up to 30% of total measured bacteria within urban receiving waters (e.g., municipal drains, storm water ponds, streams) has been directly attributed to dog inputs. In fact, dogs are now often identified as the single greatest contributor of fecal coliform loading within urban areas, with even small amounts of fecal bacteria found to significantly reduce water quality. Of course, a dog waste input need not be direct as urban water bodies act as receiving basins for large drainage areas, and that even small upstream inputs can alter downstream water quality. For example, only 24 grams of dog feces/day (a single elimination by a small dog) into an upstream creek is enough to raise bacterial levels in both a downstream lagoon and subsequently the beach swimming zone.
Dog waste has been found to be a significant source of nutrient loading, accounting for up to 76% of total phosphorus and 28% of total nitrogen levels in some urban watersheds, which is more than is linked to agricultural practices. Nutrient loading, in turn, can lead to eutrophication and the production of algal masses that shift towards blue-green algae blooms. Such increased production can translate into an overload of organic carbon, causing reductions in dissolved oxygen (DO) and increases in pH. Changes in DO (hypoxia) resulting from nutrient loading, increased ammonia and nitrate/nitrite, and BOD influences fish behaviour, growth and mortality.
Creek Chub were selected for this study because they are one of the most widespread stream minnows in North America while able to tolerate poor water quality and thus serve as an umbrella species for this study with any measured responses likely to also extend to, and be more acute for, a wide range of less tolerant fish species.
Test results demonstrated the impacts of the global dog waste management problem can have on aquatic communities as exposure to dog feces had a significant impact on fish survival, while time-to-mortality also decreased with exposure level. Interestingly the majority of deceased individuals across all exposure levels/types were found to have developed abnormal abdominal subdermal lesions and/or skin discoloration near the area over the stomach/pyloric cecae. Not only did exposure to dog feces affect fish survival and weight, but behavioural changes were also observed. Such observed behavioural changes come at a physiological cost, and along with the observed size-dependent mortality, may have the potential to have large impacts on wild fish populations by altering population size-class structure and dynamics.
Smaller individuals remaining in populations within chronically polluted waters may not experience such immediate mortality, however the behavioural shifts observed here as a function of pollutant exposure may result in increased vulnerability to predators both due to increased visibility and decreased escape-responses (swimming activity/speed). By extension, fish may experience reduced foraging efficiency and thereby growth as well as reduced reproductive development and success, ultimately leaving surviving populations with overall reduced health and fitness
Consequences are likely to be even more severe for less pollution-tolerant fish populations and exacerbated under future scenarios that consider the dog population, the amount of urbanization, the relative prevalence of impervious surfaces and climate change all continue to increase.
SUTERA In-Ground Dog Waste Solution:
SUTERA In-Ground (SUTERA), an Ontario environmental leader solving ecological concerns has developed, implemented, and successfully proven a comprehensive containment, collection, and processing system specifically for dog waste.
SUTERA’s dog waste system temporary contains large volumes of dog waste beneath the earth’s surface inside a re-usable PVC lifting bag while securely contained within a monolithic precast concrete basin keeping contents cool, odour-free and secure from leaching into the surrounding soils.
In 2018, Canada’s 8.2 million dogs (Canadian Animal Health Institute, 2019) collectively generated over 1 million tonnes of waste. Considering only 60% of people pick up their dog waste (Swann, 1999; Waters et al., 2011), 400,000 tonnes of dog feces became direct land or marine pollution.
SUTERA believes it is the responsibility of all residents to act in ways that protects their local environment but require the proper provided infrastructure to encourage those desired behaviours. The need for infrastructure was validated by a United Kingdom study entitled Investigating Barriers to Behavioural Change in Dog Walkers. It concludes people do not pick up after their dog was because the ‘lack of availability of dedicated dog waste bins’ (mean score of 3.97) and ‘dedicated dog waste bins need to be in close proximity to one another’ (mean score 3.60).
SUTERA is an excellent example of the Government’s desire to activate the private sector to develop a clean economy by bringing new ideas and solutions protecting the air, land, and water by reducing litter and lowering greenhouse gas emissions.