Phytoplankton in the Gulf of Maine have become 65% less productive. The Gulf of Maine is home to the North Atlantic right whale, a critically endangered species with less than 350 left alive. Right whales feed on zooplankton, krill, and other small crustaceans. These animals are fed by phytoplankton, organisms at the base of the food chain. Phytoplankton require sunlight for photosynthesis to survive and thrive. They also need inorganic nutrients, including nitrates, phosphorus, and sulfur. These nutrients are then transformed into proteins, fats, and carbohydrates. With 65% less productivity, these processes are less successful. Since 1970, population size has decreased by over 50%. This has likely contributed to the loss of productivity, in addition to other harms. With this dilemma, the entire oceanic food chain is at risk. 

But what is harming the phytoplankton? Conditions such as warm waters and excessive nutrients seem conducive to population growth. The answer is simple: pollution. Even when conditions point to a species’ success, contamination deters both reproduction and productivity. Pollutants hurt ecosystems, deteriorate animal health, and exacerbate climate change. 

One frequently overlooked pollutant is herbicides. The most prevalent is glyphosate. First discovered in 1970, glyphosate is used in widely available commercial formulations such as Roundup. Glyphosate is an enzyme inhibitor, specifically for EPSP synthase, which is critical for synthesizing amino acids. It causes cell death, damages cellular structures, and disrupts biochemical processes, including respiration and photosynthesis. Glyphosate only targets organelles in plant cells, such as the cell wall and chloroplasts, and is meant to be benign to animal cells. As a result, it is one of the most widespread and effective herbicides to date. 

Due to its predominant availability, glyphosate is utilized in most facets of life. It has a wide variety of agricultural applications, including both food and non-food crops. Used for a number of row crops, orchards, farms, and vineyards, this herbicide is spread on a multitude of popular produce, including corn, soybean, alfalfa, apples, cranberries, and more. It is also spread on inedible crops such as Christmas trees and other household plants. Commercial and residential uses are widespread, with aesthetic uses for landscaping, lawn care, gardens, parks, and turf grasses. More practical uses include paved areas such as driveways, sidewalks, roads, powerline rights of ways, transportation routes, and industrial yards. Some environmental uses are meant to help manage certain habitats. Glyphosate has been used to manage conservation land, forests, aquatic areas, and habitat care. This has typically resulted in removing invasive species and preserving natural ecosystems. 

A variety of environmental impacts have been studied and debated. Dissenting opinions between the scientific community and the United States Environmental Protection Agency (EPA) present a dilemma with conclusive data. The EPA has determined that glyphosate has minimal effects on birds, fish, mammals, and invertebrates, contributing to this herbicide’s popularity. However, it has the potential to contaminate surface waters and is not broken down by sunlight like other pollutants. Phytoplankton are found at the upper levels of waters to receive sunlight to undergo photosynthesis. The EPA determined that glyphosate can harm nontarget aquatic plants, which could hurt the phytoplankton. It has even been found to be toxic to particular biota, including algae, fungi, and bacteria. Studies have shown that commercial formulations like Roundup may be more harmful than glyphosate. 

Other harms relate to bioaccumulation and biomagnification of glyphosate in the food chain. Bioaccumulation is the buildup of absorbed chemicals in an organism over time, whereas biomagnification is the increased concentration of absorbed chemicals in organisms up the food chain. Glyphosate accumulates in coastal oceans, presenting a problem in the Gulf of Maine, where the right whales feed. As it accumulates in the oceans, it impacts the bottom of the food chain. Phytoplankton, bees, and mosquitos are all harmed by this herbicide, with biological processes affected and mortality increased. Additional studies have found developmental problems occur when pregnant mothers ingest glyphosate. Lower body weights and problems with bone and organ growth have been found in animals after birth. Furthermore, aquatic animals have been seen to have impacts on metabolism, development, and reproduction. Any adverse impacts on these marine ecosystems can cause issues for the North Atlantic right whales, who are highly at risk as a critically endangered species. 

Over the last 30 years, total use of glyphosate has dramatically increased. Since 1996, when Roundup’s founding father, Monsanto, created genetically engineered seeds that can withstand higher amounts of herbicides, the use of glyphosate has increased by tenfold. At the same time, phytoplankton productivity has drastically decreased. Phytoplankton have chloroplasts to conduct photosynthesis to survive, but these are directly targeted by glyphosate. Now, correlation does not mean causation. Although glyphosate was introduced in 1970, the same year the phytoplankton population began its decline, many different factors are at play. Glyphosate is not being directly sprayed into the Gulf of Maine. Nor is it the only thing harming the phytoplankton. However, the prevalent human and environmental health impacts make a strong case for why this herbicide should be banned. 

Bans of varying degrees have been established in cities and countries worldwide. No state in the United States has passed a total ban, but a number of cities nationwide have banned it for certain uses. A federal ban is unlikely, but citywide bans have only increased, with Maine leading the way. Over 30 cities and towns have placed restrictions to various extents. In March of 2021, Maine legislators passed a ban on aerial spraying of glyphosate in forests. Unfortunately, the governor vetoed it in June to prevent more manual labor that would raise costs for landowners. She feared that it would require more applications at higher concentrations to have the same level of effectiveness. As a result, a statewide ban in Maine is unlikely to occur any time soon.

Glyphosate is the most heavily used herbicide in history. Evidence has found that the scale at which glyphosate is used presents the largest problem of all. With its impact on phytoplankton photosynthesis processes, the increase in use directly correlates with decreased population and productivity. Monsanto has faced over 9,000 lawsuits regarding cancer diagnoses related to glyphosate. An increasing number of recent studies have found harm to animals caused by glyphosate despite being at levels considered safe by the EPA. Opposing conclusions between the EPA and the World Health Organization (WHO) make passing restrictions difficult. The greatest solution to save the phytoplankton, and in turn, the North Atlantic right whales, is to consciously stop using glyphosate-based herbicides. Doing so will prevent any further harm caused by glyphosate to phytoplankton and restore feeding grounds for right whales to their proper productivity levels. 

Where Have All the Phytoplankton Gone was written by Cara Wong, ORI Summer Intern.