Dr. Daniel Canfield | Reprioritising Pollution Reduction in Florida’s Lakes

Florida’s landscape is dotted with thousands of lakes that reflect regional geology, topography and anthropogenic activities. Phosphorus and nitrogen are critical nutrients for maintaining the wide range of biological production expressed across Florida, but excessive inputs of these nutrients due to past human activities impair many waters. There has been a long history of work aiming to address associated water quality pressures, and Dr. Daniel Canfield at the University of Florida has been at the centre of these efforts for over 40 years. Now, with the correction of point-source nutrient inputs, Dr. Canfield proposes that holistic lake management, including the integration of in-lake management strategies with a focus on organic sediment removal, should be much more prominent on the US government’s agenda to provide faster restoration of stakeholders’ lake usability.

Florida’s Lakes Under Pressure

Prior to the 1970s, many of Florida’s lakes were heavily polluted by chemicals from point-source human activities. Wastewater treatment plants, factories, and farms all discharged critically important plant nutrients, especially nitrogen and phosphorus, that influenced the biological productivity of Florida lakes. Excessive build-up of these nutrients in waterways promoted the growth of tiny photosynthetic organisms known as algae. Excessive algal growth destabilised the ecosystem and had dire effects on some aquatic animals and plants. The build-up of algae and weeds also made the lakes less attractive and enjoyable for people hoping to engage in recreational use.

In 1972, the US government passed the Clean Water Act, contributing to making it illegal to discharge pollution directly into Florida’s lakes. These regulations have been highly successful at stopping this type of pollution. More recently, government and environmental groups have shifted their focus to becoming increasingly concerned about pollution in rivers and streams that drain into the lakes – ‘nonpoint source pollution’. They fear that population growth, urban development, and increased use of agricultural chemicals in surrounding areas will increase levels of nonpoint source pollution. This fear is particularly important as agricultural pollution has contributed to a major dead zone in the Gulf of Mexico.

Water Bodies in Need of Help

Driven by these concerns, the US, Florida, and local governments worked to prioritise the lakes that were most in need of work to restore them to their former desired condition. When a lake is so polluted that it cannot be enjoyed by the public or stops being a good habitat, the US Environment Protection Agency marks it as ‘impaired’. Getting classifications like this right is important as an ‘impaired’ status triggers a huge amount of work and investment in further assessments and improvements.

Unfortunately, this process isn’t perfect. For example, one of Florida’s largest lakes, Lake Okeechobee, has been classified as impaired even though the levels of nitrogen and phosphorus are most likely caused by natural processes. Dr. Canfield has been closely monitoring the water quality across Florida’s lake for much of his career. He was concerned the government may be wasting money and effort by now only focusing work on nonpoint source pollution rather than on projects that can make a real change to the designated uses of the lakes.

Better Resource Prioritisation

Dr. Canfield’s extensive work monitoring the Florida Lakes often contradicted the government’s assessments. This led him to believe that lakes were being classified as impaired too readily. Dr. Canfield also expected that the government was overestimating the role of nonpoint source pollution in 510 lakes, which had been marked as impaired due to nutrient pollution.

This particularly concerned Dr. Canfield, as in 2008, legal action by environmental groups resulted in new laws being passed requiring the local government to assess the ‘Total Maximum Daily Load’ of nutrients that can enter a lake across its whole watershed. Dr. Canfield saw two major issues with this approach. First, there was a risk that some areas were being required to undergo a highly complex and resource-intensive process that may not be needed. Second, even where it was justified, this process alone would not be enough to change the fate of the lakes in decline.

Citizens preparing to discuss lake management options for managing desired uses. Credit: Dr. Daniel Canfield

Accurately Assessing Trends in Water Quality

Dr. Canfield set out to demonstrate which lakes were actually in decline and which of these were being driven by nonpoint source pollution. He hoped that this could help prioritise resources for areas that needed them most.

He and his team assembled a huge set of water quality and biological data across Florida, covering over 2,000 lakes. It takes a long time for rivers and lakes to react to changes and even longer for changes to show up in the data. To ensure that their analysis only focused on genuine trends, the team looked at lakes with data from 20 years or more. This narrowed the exercise down to 381 lakes.

Dr. Canfield’s team then further scrutinised the long-term trends in nutrient pollution, including nitrogen, phosphorus, and other metrics linked to algae growth and water quality. Importantly, they disregarded any data that did not show a strong trend and identified the lakes where they had a high level of confidence that monitoring was showing a real change, either positive or negative.

Their work showed that, on average, across the lakes with enough data to study, nonpoint nutrient pollution had fallen since 1987, and overall water quality looked like it was increasing. This was a big win for Florida’s Lakes – but it contradicted the views of the government and many local groups that focused on visible algal blooms, now being designated as ‘harmful algal blooms (HABs)’. Their work also showed that many of the trends seen in the lakes could not be reliably linked to a specific cause and that only a handful had notably increased nutrient levels. Most strikingly, of the 99 lakes in their study that were marked as impaired by the government, only 18 showed a significant increase in nutrients.

Making Improvements in Our Lifetime

Through this analysis, Dr. Canfield and his team developed a rigorous set of statistical tests that could be used to triage lakes for further work. Dr. Canfield proposes that the government should redevelop its approach and only require a detailed analysis of nonpoint source pollution, where there is strong evidence that this is a cause of the decline.

By prioritising this, Dr. Canfield hopes that more time and money can be spent on alternatives to improving the designated uses of lakes via well-developed and proven in-lake management strategies. Each water body functions as an individual. From his extensive work with people and organisations trying to improve lakes, their ultimate goal ‘My Lake’ and its designated uses rather than all Florida lakes, Dr. Canfield suggests that a greater focus on unbiased diagnostic studies that find the cause of a lake’s decline would be a better use of resources. These approaches may point to more direct in-lake restoration strategies, such as adding aluminium sulphate to reduce phosphorus levels when necessary for clearing the water, promoting proactive management of aquatic plants and fisheries as well as removing bottom sediments to remove legacy nutrients and organic matter to improve aquatic plant and animal habitats. Putting the land back on the land can become a circular recycling project that can benefit not only the individual lake but also other societal concerns. Working with local stakeholder groups on these kinds of projects is much more likely to make improvements that people can see and enjoy in their lifetimes.

Of course, this approach is not new – the Clean Lakes Programme run by the Federal Government was a well-proven approach to supporting locally specific projects when first envisioned before all efforts became focused only on nutrient control. Dr. Canfield’s work highlights the importance of reviving this programme and supporting local communities to take a holistic approach that readily accepts rather than ignores well-proven in-lake management strategies for the long-term management of My LAKE!