Massive Algae Blooms Choking Waterways, Synthetic Fertilizers in Chemical-Intensive Land Management a Major Cause
(Beyond Pesticides, July 20, 2018) Algae are elemental to life on Earth as generators of most of the planet’s oxygen and as food for myriad organisms. In the food chain, as in all systems, balance is key; but in Florida, erupting algal blooms are evidence of a system wildly out of balance. Blue-green algae species are coating the surfaces of many of the state’s lakes. In the past month, algae on the state’s most-well-known water body — Lake Okeechobee — grew from a crescent in one corner of the lake to 90% coverage of its 370 square miles. Algae have grown out of control in part because of nitrogen and phosphorus pollution, which arises from runoff from conventionally managed lands and from leaky septic systems. Beyond coating the lake surface, the slimy stuff is now found not only in the Caloosahatchee River, but also, along its entire canal system from Lake Okeechobee into downtown Fort Myers, and moving toward the river’s mouth on the southwest coast. Indeed, in early July, after touring the Caloosahatchee River estuary, Florida’s governor issued an emergency order to help state agencies in multiple counties better manage these harmful algal blooms in lakes, rivers, and coastal estuaries.
Such algae overgrowth arises from a concurrence of basic ingredients: ample warm water (think summer), sunlight, and pollution. Given that it is nigh impossible to control sunlight or water temperature — and water temperatures and extreme spring and summer rain events will likely worsen, given climate disruption — humans can have the greatest impact via their own contributing activities. The U.S. Environmental Protection Agency (EPA) indicates that, “The most effective preventative measures are those that seek to control anthropogenic influences that promote blooms such as the leaching and runoff of excess nutrients. Management practices for nutrients, specifically nitrogen and phosphorus, should have the goal of reducing loadings from both point and nonpoint sources, including water treatment discharges, agricultural runoff, and stormwater runoff.”
Put simply: nitrogen and phosphorous, characteristic of agricultural runoff from the use of synthetic fertilizers, boost algal growth. The extremely common use of such fertilizers in chemical-intensive (conventional) agriculture and turf care is a huge contributor to the problem.
A primary fix for the epidemic of algal blooms is curbing nutrient pollution by avoiding use of synthetic fertilizers in agriculture, and in turf and landscape management (of golf courses, sports fields, lawns and gardens, etc.). The optimal way to do that is to adopt organic agricultural and land management practices. A Beyond Pesticides Pesticides and You journal article from 2014 notes, “Organic standards stipulate that soil fertility and crop nutrients can be managed through tillage and other cultivation practices, such as crop rotation [and use of compost as fertilizer], which preserve and maintain the fertility of the soil so that synthetic inputs become unnecessary. Organic, therefore, eliminates the need and use of synthetic nitrogen- and phosphorus-based fertilizers, thereby significantly reducing the threats that nitrogen and phosphorus runoff have on aquatic ecosystems and the prevalence of algal blooms and eutrophication [overgrowth of plant life and death of animal life from subsequent lack of oxygen].”
Synthetic fertilizers contain water-soluble nutrients, some of which are not absorbed by plants, but settle in the soil and then migrate toward groundwater and ultimately, water bodies. Organic agricultural and turf management practices, such as the use of compost to boost soil fertility — rather than dumping synthetic fertilizers into the soil — are effective solutions to the problem.
Organic methods feed the soil, rather than feeding plants directly. Organic fertility and soil amendments (such as compost) are not water soluble; they feed the microorganisms in the soil and the breakdown products of that process release nutrients that then feed plants. This slower process does not result in the runoff associated with water-soluble synthetic materials. The 1990 Organic Foods Production Act established regulations that permit only those soil inputs that do not adversely affect the “biological and chemical interactions in the agroecosystem, including the physiological effects of the substance on soil organisms.” Synthetic fertilizers are prohibited in certified organic systems. As Beyond Pesticides noted in the Fall 2017 issue of Pesticides and You, “While chemical-intensive land management relies on synthetic fertilizers that are soluble chemicals taken up by the plant and prone to run-off into waterways, organic systems rely on feeding the soil microbes, which in turn produce solubilized nutrients that are absorbed by the plant.”
Researchers on the issue of algal blooms and “dead zones” in Lake Erie (and other Great Lakes) were able to pinpoint the two major factors that explain their observation of marked increases in dissolved reactive phosphorus, which is nearly 100% bioavailable to algae. Those factors, they concluded, were “a combination of agricultural practices that have been put in place since the late 1980s and into the 2000s, combined with increased storms, particularly higher intensity spring rain events [attributable to climate change].” The agricultural practices the researchers' reference include a shift toward more fall fertilizer applications instead of spring applications, the use of broadcast fertilizer that does not integrate into the soil, and an increase in no-till field management that leads to a build-up of phosphorus in the top layers of soil. No-till methods concentrate fertilizers near the soil surface where they are more likely to wash away during strong storms.
People, of course, don’t like to see their favorite lakes or rivers covered in green slime. But the problems with algae overgrowth are not only aesthetic: the blooms choke off sunlight to underwater organisms that require it for photosynthesis, deplete oxygen in the water and deprive other organisms of it, and can spread to ancillary water bodies. These conditions can cause the above-mentioned “dead zones” — hypoxic (low-oxygen) areas in large water bodies that cannot support most marine life in lower-level water. Sometimes, toxic subspecies of algae appear and present health risks (including liver and brain diseases).
In addition, the fertilizers that spur this growth can contaminate groundwater, including those aquifers used as sources of drinking water. A 2013 study found that synthetic nitrogen from fertilizers (as nitrates) leaches from soil toward groundwater over the course of decades, meaning that the agricultural and land management activities of as long as 50 years ago may still be affecting water bodies. Nitrate is a common contaminant of drinking water in agricultural areas where nitrogen fertilizers are used. Another “bonus” is that intensive use of synthetic fertilizers may increase the nitrate levels found in certain vegetables, such as lettuce and root crops. Research has indicated that long-term dietary exposure to nitrates may increase risk of thyroid disease (because nitrate competes with the uptake of iodide by the thyroid gland, potentially affecting thyroid function).
To combat algal blooms and their harmful impacts, Beyond Pesticides recommends advocating for organic agriculture, purchasing organics to leverage demand in the marketplace (and thus, protect human and environmental health), and encouraging organic land management at the local level (city, town, and/or county). For assistance with such advocacy in your community, contact Beyond Pesticides at info@beyondpesticides.org or 1.202.543.5450.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: https://www.miamiherald.com/news/local/environment/article214620390.html