12
Jun
Pesticide-Contaminated Algae Found to Jeopardize Ecosystems and Human Well-Being [Study]
(Beyond Pesticides, June 12, 2024) A study of pesticide contaminated algae finds that the disruption of algal communities has a devastating effect on the health of the aquatic food web. The study findings show that contact with pesticides can result in changes to “algal physiology, causing tissue injury, developmental delay, genotoxicity, procreative disruption, and tissue biomagnification†that alters the dominance of algae species in the environment. This in turn “can impact higher trophic levels and have a domino effect on the aquatic food web. It is possible for biodiversity to disappear, reducing ecosystem stability and resistance to environmental alterations,†the authors state. The study, a worldwide literature review conducted by researchers from India, South Korea, and Saudi Arabia, appears in Aquatic Toxicology.Â
The health of aquatic ecosystems is at risk with indirect effects on nontarget species from pesticides in the environment. This includes impacts on species of fish, invertebrates, microbial communities, and marine mammals. In explaining the importance of extensively studying effects of pesticides, the researchers note, “Different pesticide classes have different chemical structures, which define their modes of action and affect how they interact with both target and nontarget organisms.†Because of this, the range of effects seen from pesticide exposure is widespread. The amount and type of pesticides that contaminate waterways and the species of algae exposed to them can lead to varying consequences. Â
In referencing over 150 studies, this review consolidates relevant results and conclusions regarding the effects of pesticide exposure on algal communities. The main pesticides identified in the research include atrazine, glyphosate, bifenthrin, and imidacloprid. Studies find that atrazine, an herbicide used for grasses and weeds, inhibits the photosynthetic machinery of algae such as diatoms and green algae, while glyphosate, a similar herbicide, affects nutrient dynamics and induces shifts in algal community composition. Bifenthrin, a pyrethroid insecticide, also causes an imbalance in algal populations. While copper-based algicides to control algal blooms show impacts on nontarget algae and disrupt photosynthesis, neonicotinoid insecticides like imidacloprid lower populations of zooplankton and allow algal communities to flourish.  Â
“Because different algae species have diverse physiologies, metabolic pathways, and susceptibilities to different toxicological processes, the impact of pesticides on those species can differ significantly,†this study finds. While different pesticides alter the structure of the algal communities in different ways, they all lead to changes in the marine food web and overall ecosystem health. The use of pesticides from any class severely threatens the fragile balance of aquatic environments, as any shift in species’ populations can impact other species as well. Â
Herbicides, such as atrazine and glyphosate, are “potent inhibitors of algae photosynthetic activity,†the authors observe, with multiple studies linking herbicide exposure to the prevention of chlorophyll formation and electron transport in certain species of algae. Without being able to carry out photosynthesis, these algal communities’ biomass and production decreases.Â
Alternatively, the interaction between other pesticides and algae species can lead to an increase in the amount of algae present after exposure. The researchers report, “Changes in nitrogen cycling by pesticides may raise nutrient availability, supporting algal blooms and lowering water quality.†Algal blooms are a result of the process known as eutrophication. When there is a spike in available nutrients, it causes an increase in the amount of plant and algae growth. The excessive nutrients set off a chain reaction that results in low oxygen levels in the water that kill fish and other organisms. Impacts of algal blooms can include fish mortality, shrimp mortality, fishery collapse, human health impacts (such as poisoning) upon consumption of contaminated shellfish, and deterioration of water quality. Â
The researchers emphasize, “Algal species are essential players in cycling nutrients and energy transmission due to their diversity and ecological roles. Pesticide exposure can affect algal communities through direct contact with polluted water, indirect contact through contaminated prey, and interruption of photosynthesis, especially from herbicides. Algal growth, reproduction, and general community dynamics may be impacted by such exposure.â€Â
The persistence of pesticides in the environment leads to bioaccumulation in “algal tissues, which could result in biomagnification as the toxins climb the food chain and endanger higher trophic levels.†The direct contact with these chemicals can cause “rapid physiological stress that impairs photosynthesis growth rates and, in extreme situations, results in death,†while the indirect contact to other organisms through the food web leads to negative impacts on the biological balance of entire marine ecosystems. Â
Bioaccumulation (concentration over time of individual organisms) and biomagnification (exponential increase in concentrations throughout the levels of the food web) of pesticides cause a cascade of issues throughout all trophic levels. (See more on trophic cascades.) The pesticide-laden algae pass their contamination to organisms that consume them, and the contamination continues to increase through trophic transfer. As the National Oceanic and Atmospheric Administration (NOAA) explains, “Phytoplankton and algae form the bases of aquatic food webs. They are eaten by primary consumers like zooplankton, small fish, and crustaceans. Primary consumers are in turn eaten by fish, small sharks, corals, and baleen whales. Top ocean predators include large sharks, billfish, dolphins, toothed whales, and large seals. Humans consume aquatic life from every section of this food web.â€Â
Because these impacts affect all organisms and the environment, a holistic approach is needed to assess pesticide usage and exposure. These chemicals are “jeopardizing environmental integrity and human well-being,” the authors assert. They continue in saying, “Pesticides infiltrate water bodies through runoff, chemical spills, and leachate, adversely affecting algae, vital primary producers in marine ecosystems. The repercussions cascade through higher trophic levels, underscoring the need for a comprehensive understanding of the interplay between pesticides, algae, and the broader ecosystem. Algae, susceptible to pesticides via spillage, runoff, and drift, experience disruptions in community structure and function, with certain species metabolizing and bioaccumulating these contaminants. The toxicological mechanisms vary based on the specific pesticide and algal species involved, particularly evident in herbicides’ interference with photosynthetic activity in algae.â€Â Â
Studying the impacts on algae is vital because they are crucial primary producers in aquatic ecosystems, are vulnerable to the negative impacts of pesticides, and their deteriorated health can have a cascading adverse effect on higher trophic levels. Because of their sensitivity to chemicals in the environment, algal communities offer insights into the health of ecosystems and need to be further studied.  Â
The authors conclude, “A comprehensive comprehension of these characteristics is essential for evaluating the influence on the environment, creating efficient management plans, and advocating for environmentally friendly farming methods that reduce damage to ecosystems.†With all organisms being dependent on one another and the environment, assessing the negative impacts of pesticides currently in use and offering alternatives is imperative. Â
There is an overwhelming body of science that shows the negative implications associated with pesticide exposure on the environment including in soil, water, and air, as well as detrimental effects on human health. Alternatives, such as organic agriculture, offer a path forward that eliminates these threats. Â
Beyond Pesticides’ mission is to lead the transition to a world free of toxic pesticides. You can start by supporting and buying organic products and making The Safer Choice to avoid hazardous home, garden, community, and food use pesticides. Stay informed with the Daily News Blog, and take action to create change with Action of the Week.Â
 All unattributed positions and opinions in this piece are those of Beyond Pesticides. Â
Source:Â
Narayanan, N. et al. (2024) Assessing the ecological impact of pesticides/herbicides on algal communities: A comprehensive review, Aquatic Toxicology. Available at: https://www.sciencedirect.com/science/article/abs/pii/S0166445X24000225?via%3Dihub.
