The alerting state of our environment is of major concern. As our world grapples with the consequences of pollution and ecological degradation, the significance of maintaining clean and healthy water sources is paramount. In this article, we explore the pivotal role algae play in ecotoxicology, the science dedicated to assessing the impact of toxic substances on ecosystems.
Algae, photosynthetic organisms living in all kinds of aquatic environments, have become powerful allies in our quest to ensure the quality of our waters, being vital for ensuring ecosystem maintenance and a safe water supply. We will dig into the reasons clean waters are so critical, the benefits of using algae as models for toxicity testing, the primary assays used, and the importance of international guidelines in shaping algae-based toxicity studies.
The Relevance of a Clean Environment and Waters
The importance of a clean and healthy environment and water cannot be overstated. Water is a key element for the balance and sustainability of all ecosystems as suppose 90% of the habitable space on the planet, supplies half of the oxygen we breathe, and absorbs 26% of the human-produced carbon dioxide. Therefore, the quality of our aquatic ecosystems directly impacts human health, biodiversity, and the overall well-being of our planet. Clean waters support thriving ecosystems, provide safe drinking water, and offer recreational opportunities. They also play a crucial role in agriculture, industry, and energy production. Contaminated waters, on the other hand, pose serious threats, with detrimental consequences ranging from the destruction of aquatic life to human health hazards. Therefore, safeguarding clean waters is not purely an environmental concern, but a vital necessity for survival.
Benefits of Using Algae as a Model for Toxicity
Algae, usually planktonic algae, those unicellular or colonial algae living in the water column, have emerged as invaluable models in ecotoxicology for several compelling reasons. First and foremost, they serve as reliable indicators of environmental health due to their sensitivity to changes in their surroundings. As primary food source and nutrients for many aquatic species since they form the base of many aquatic food chains, their health is critical to the entire ecosystem. Another important feature of these organisms is their fast-growing, enabling rapid assessment of the impact of toxins and being easily cultivated and taken up little space, making them a cost-effective choice for toxicity evaluation. Furthermore, algae exhibit distinct responses to different types of pollutants, aiding in the identification of the specific contaminants and their effects on ecosystems. Both, freshwater and marine algae are used to adapt the testing to the differences between freshwater and marine ecosystems.
The Main Assays Used in Algae-Based Toxicity
Toxicity testing with algae relies on various assays that provide insights into the health of these organisms and, by extension, the surrounding ecosystem. Some of the main assays include:
- Growth Inhibition Tests: These assays measure changes in algal biomass over time in the presence of pollutants. A decrease in growth rates indicates the presence of toxic substances that hamper the normal growth of these organisms. The biomass can be indirectly measured by the fluorescence produced by their photosynthetic pigments. Monitoring the reduction of growth with increased doses of toxic products in dose-response curves allows for estimating the doses at which pollutants are hazardous.
- Photosynthesis Measurements Assays: Monitoring changes in photosynthetic activity reveals how pollutants affect algal health and function by measuring energy production. Photosynthesis measurements assess the efficiency of this process by quantifying various parameters related to oxygen production, pigment content, and electron transport. Where reduced photosynthesis can signal environmental stress.
- Cell Membrane Integrity Assessments Assays: The integrity of the cell membrane is essential for the overall health and function of algae, as it regulates the exchange of substances between the cell's interior and the external environment. Assessing cell membrane integrity provides insights into how pollutants may affect the structural and functional integrity of algae. Therefore, disruption in cell membrane integrity is a clear indicator of toxic effects. These assessments often use indicators like fluorescence or cell staining to detect damage that in healthy cells products are not able to pass through the membrane as they are hydrophobic selective barriers.
Relevance of International Guidelines for Algae-Based Toxicity Assays
The standardization of toxicity assays procedures is crucial for ensuring consistent and reliable results. International Guidelines provide a framework for conducting algae-based toxicity assays, promoting transparency and comparability of data. Guidelines such as the OECD (Organization for Economic Co-operation and Development), EPA (Environmental Protection Agency), or ISO (The International Organization for Standardization) standards establish best practices, including test conditions, sample handling, and data reporting. Compliance with these guidelines not only enhances the quality of research but also helps regulatory entities make informed decisions regarding water quality standards and pollution control measurements.
Biobide Ecotoxicity Assays
Ecotoxicity Assays are one of the many services that Biobide offers, included in the pipeline of services the Contract Research Organization (CRO) offers for the evaluation of the impact of chemicals such as pesticides, herbicides, industrial chemicals, cosmetics, personal care products, or pharmaceuticals, among other.
Biobide´s assay catalog for water pollutants toxicity evaluation includes not only algae but also other aquatic models such as Daphnia and Zebrafish. Regarding alga toxicity assay, Biobide offers a miniaturized High-Content Screening Algae Growth Inhibition Assay. This assay is based on the OECD guideline Test No. 201 (Alga, Growth Inhibition Test) but adapted to a microplate format in order to deliver a more cost-efficient assay that requires less testing compound or test items quantity. Briefly, algae are seeded in the microplates and treated with several concentrations of the desired compound using a liquid-handling robot. After, the microplates are incubated under a high-intensity light for fast growth of the algae, and the biomass is monitored daily for 72 hours through fluorometric measurement.
For toxicity assessment, the percentage of growth inhibition for each compound concentration is calculated by the fluorescence decrease, directly proportional to the biomass between compound-treated algae and control algae, only treated with the compound vehicle substance.
The compound toxicity is calculated by the regression analysis of the dose-response curve generated with the growth inhibition measurement for each tested concentration and the subsequent statistical analysis.
Biobide Ecotoxicity Assays
The use of algae in ecotoxicology is a testament to the remarkable potential of these simple organisms in safeguarding our environment. Clean waters are the cornerstone of healthy ecosystems, human well-being, and the planet's future sustainability. Algae, with their sensitivity, versatility, and cost-effectiveness, have become indispensable tools in assessing the impact of toxic substances in our waters. The primary assays used, such as the growth inhibition tests and photosynthesis measurements, provide valuable data for environmental management. Furthermore, adherence to international guidelines ensures the consistency and reliability of algae-based toxicity studies. By harnessing the power of algae, we can better understand and address the threats to clean waters, ultimately securing a sustainable future for generations to come.
Sources
- http://npic.orst.edu/factsheets/ecotox.html#:~:text=1,%2C%20natural%20communities%2C%20and%20ecosystems.
- https://www.un.org/en/chronicle/article/marine-biodiversity-and-ecosystems-underpin-healthy-planet-and-social-well-being
- Christina Rudén, et al., “Assessing the relevance of ecotoxicological studies for regulatory decision making”, 2016
- https://www.un.org/depts/los/global_reporting/WOA_RegProcess.htm
- Corinne Le Quere et al., “Global carbon budget 2015,” Earth System Science Data, vol. 7, no. 2 (December 2015), pp. 349 to 396 (371).
- https://www.oecd-ilibrary.org/environment/test-no-201-alga-growth-inhibition-test_9789264069923-en
- Masakazu Katsumata, et al., “Rapid ecotoxicological bioassay using delayed fluorescence in the green alga Pseudokirchneriella subcapitata”, 2006, pp. 3393 to 3400 (40).
- Tania Tato and Ricardo Beiras. “The Use of the Marine Microalga Tisochrysis lutea (T-iso) in Standard Toxicity Tests; Comparative Sensitivity With Other Test Species”, 2019.
