The review’s methodology was deliberately rigorous. The team searched Web of Science and Scopus from 1970 all the way to August 2025, using predefined combinations of terms covering microplastics, marine microalgae, toxicity, and marine pollution. After removing duplicates and screening titles, abstracts, and keywords, 59 publications addressing microplastic–microalgae interactions were retained for bibliometric characterization. Of these, 43 original studies reporting direct experimental exposure of marine microalgae to plastic particles qualified for the comparative ecotoxicological synthesis. Strikingly, no eligible publications predate 2016, indicating that this research field is barely a decade old. Publication output grew from a single paper in 2016 to a peak of fourteen in 2024, a trajectory that mirrors the broader explosion of microplastic science but also reveals how young and incomplete the evidence base for marine primary producers remains compared with the meta-analyses already available for fish and aquatic invertebrates.

Geographically, the field is strikingly concentrated. China accounted for 54.24 percent of the 59 selected publications, followed by Spain and South Korea at 6.78 percent each, with Portugal, France, Italy, Belgium, and Brazil contributing smaller shares. Sixteen countries appeared in total, yet only seven publications involved international co-authorship, a mere 11.86 percent. The authors suggest this insularity may contribute to the methodological heterogeneity that pervades the literature, since research groups working in isolation tend to adopt different experimental designs, particle characteristics, and exposure conditions. The dominance of Chinese output aligns with global bibliometric trends in aquatic ecotoxicology and has been linked to expanded research funding, notably through the National Natural Science Foundation of China since 2015.

When it comes to what is being tested, one polymer dominates the experimental record. Polystyrene appeared in 25 of the 43 studies, followed by polyethylene in 10, polyvinyl chloride in 5, and polymethyl methacrylate in 3. Polyamide, polylactic acid, polybutylene succinate, polyethylene terephthalate, tire wear particles, and gear-derived microplastics each featured in a single study. The review’s authors point out an important disconnect here: polystyrene’s laboratory ubiquity likely reflects the commercial availability of standardized fluorescent spheres and microbeads rather than its environmental prevalence, since polyethylene and polypropylene are often more abundant in surface waters. This mismatch between what scientists test and what organisms actually encounter in the ocean has significant implications for extrapolating laboratory findings to real-world risk assessment.

The organisms under scrutiny show a similar taxonomic skew. Diatoms, the glass-walled phytoplankton that underpin much of coastal and oceanic productivity, were investigated in 22 studies, or 51.2 percent of the experimental dataset. Chlorophyta, the green algae, featured in 10 studies, and dinoflagellates in 8. Other groups, including haptophytes, raphidophytes, cryptophytes, cyanobacteria, and red algae, were barely represented. The authors highlight this as a critical gap, noting that coccolithophores, for example, play a central role in the marine calcium carbonate cycle yet remain almost entirely unstudied in the microplastic context. Because microplastic toxicity is increasingly recognized as species-specific, expanding taxonomic diversity is essential for predicting how entire phytoplankton communities, not just a handful of laboratory workhorses, might respond to chronic plastic exposure.

So what do the experiments actually show? The most frequently evaluated endpoints were grouped into six functional categories, and growth and population parameters led by a wide margin, assessed in 40 of the 43 studies. Growth inhibition, growth rate, cell density, and cell viability were the workhorse measurements. Cellular stress and damage indicators, particularly oxidative stress driven by overproduction of reactive oxygen species, appeared in 29 studies, with documented consequences including lipid peroxidation, membrane damage, organelle injury, and reduced esterase activity. Photosynthetic physiology, encompassing photosynthetic rate, efficiency, photochemistry, and chlorophyll fluorescence, was examined in 20 studies, while structural and interaction parameters such as aggregation appeared in 25, photosynthetic biochemistry in 14, and broader biochemical or metabolic responses in 13.

The mechanisms of toxicity emerging from this literature are multifaceted. Smaller particles appear to exert greater toxicity through enhanced surface interactions with algal cells, whereas larger particles can inhibit growth indirectly through shading, physically blocking the light that photosynthetic cells depend on. Direct physical interference has been demonstrated in the diatom Skeletonema costatum, where cell–particle contact disrupts normal function. Microplastics can also act as vectors for other contaminants: work by Prata and colleagues showed that the presence of microplastics can alter the toxicity of pharmaceuticals such as procainamide and doxycycline in the microalga Tetraselmis chuii. Meanwhile, species-specific hetero-aggregation between plastic particles and phytoplankton, first characterized by Long and colleagues, can reshape particle dynamics in the water column, modifying light availability and nutrient exchange in ways that ripple through entire microbial communities.

Perhaps the most conceptually important section of the review concerns what the authors call the dynamic nature of microplastics. Particles in the ocean are not static objects. Aging and weathering alter surface chemistry, charge, roughness, and functional groups, changing how particles aggregate, adsorb contaminants, leach additives, and interact with cells. Dissolved organic matter and algal extracellular polymeric substances can coat particles in an eco-corona; one study showed that this coating actually reduced the toxicity of polystyrene nanoplastics to marine Chlorella by decreasing particle–cell interactions and oxidative stress. Biofilms growing on plastic surfaces can modify particle density, transport, and bioavailability, while weathering may enhance the release of polymer additives that contribute chemical toxicity of their own. Yet these environmentally transformed particles remain severely underrepresented in experimental work, meaning most laboratory findings rest on pristine, commercially manufactured plastics that bear little resemblance to weathered marine debris.

The review is refreshingly candid about the limits of the evidence. Most experiments rely on short-term laboratory assays with simplified exposure scenarios, often using concentrations exceeding those typically found in nature. Indeed, studies employing environmentally relevant concentrations and particle-size distributions have reported limited or no effects on microalgal growth under the conditions tested. The authors therefore argue that current evidence supports the identification of potential toxicity mechanisms far more strongly than it supports quantitative ecological risk prediction. They also flag transient effects, in which initial physiological vulnerability gives way to adaptive recovery, as a phenomenon that complicates interpretation and underscores the need to quantify actual particle bioavailability in exposure media.

Critical endpoints remain almost entirely unexplored: aggregate formation, particle sinking dynamics, DNA damage, relative electron transfer rates, and long-term exposure under realistic conditions all fall into this category. These are not academic omissions. Because microalgae sit at the base of marine food webs, alterations in their growth, lipid composition, and photosynthetic performance could propagate upward, influencing trophic transfer of both energy and plastic particles themselves. The review proposes a practical path forward: pairing robust apical endpoints such as growth inhibition, already standardized in OECD algal testing guidelines, with complementary photosynthetic physiology measures, while deploying biochemical biomarkers for mechanistic interpretation. The authors stop short of claiming laboratory responses translate directly into ecological harm. Instead, their synthesis delivers something arguably more valuable: a clear-eyed map of what we know, what we have merely assumed, and what the next decade of microplastic ecotoxicology must urgently address if science is to keep pace with one of the planet’s most pervasive pollutants.

Subject of Research: Ecotoxicological effects of microplastic exposure on marine microalgae

Article Title: Microplastic toxicity in marine microalgae: an ecotoxicological synthesis of experimental biological responses

Article References: Santos, N. G. R., Pinho, K. F. B., Reis, I. D. C. S., Luvizotto-Santos, R., & Jorge, M. B. (2026). Microplastic toxicity in marine microalgae: an ecotoxicological synthesis of experimental biological responses. Ecotoxicology, 35(8), Article 178. https://doi.org/10.1007/s10646-026-03181-x

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03181-x

Keywords: microplastics, marine microalgae, ecotoxicology, oxidative stress, photosynthesis, phytoplankton, polystyrene, polyethylene, primary productivity, eco-corona, marine pollution, systematic review

The research team, led by Nur Aini Azizah of Brawijaya University and involving scientists from Indonesia’s National Research and Innovation Agency (BRIN), set out to test a question that has received surprisingly little attention: what happens to marine algae when they are exposed to the dissolved chemicals that seep out of degrading biodegradable plastics? While conventional plastics such as polyethylene and polystyrene have been studied extensively for their effects on aquatic life, biodegradable variants have often been assumed to be benign. The new study challenges that assumption with hard numbers.

The experiment focused on three species of marine microalgae that play important roles in coastal ecosystems and aquaculture: Chlorella sp., Tetraselmis sp., and Navicula sp. These organisms were chosen because they are widely used in toxicity testing, reproduce quickly, and respond measurably to chemical stress. Before any biological testing began, the researchers used Fourier Transform Infrared spectroscopy, or FTIR, to confirm the polymer identity of the biodegradable polypropylene material used in their experiments. This analytical step matters because the market for biodegradable plastics is crowded with materials of uncertain composition, and verifying what was actually tested is essential for reproducibility.

Toxicity assays were conducted under controlled laboratory conditions following a standard 96-hour exposure window, a protocol consistent with internationally recognized guidelines for static toxicity testing with microalgae. The researchers measured growth by tracking changes in cell density over time, and for species showing significant inhibition, they also measured chlorophyll-a content, the pigment at the heart of photosynthesis. A drop in chlorophyll-a signals more than slower division; it indicates that the cellular machinery of energy capture itself is being disrupted, which can cascade through growth, reproduction, and ultimately the productivity of entire algal communities.

The first round of testing, a preliminary range-finder phase, revealed something ecologically important: the three algal species did not respond uniformly. Navicula sp., a diatom, showed no clear concentration-dependent inhibition of growth, and the team therefore excluded it from the definitive test. That kind of species-specific variation is a recurring theme in microplastic toxicology. It suggests that the ecological consequences of plastic leachates will not be evenly distributed across marine communities, and that some groups of organisms may be quietly bearing the brunt of chemical exposure while others appear unaffected.

The definitive testing on the two remaining species produced striking results. Chlorella sp. proved to be the most sensitive organism, with a 96-hour median inhibition concentration, or IC50, of just 0.49 milligrams per liter. In practical terms, that means the leachate from biodegradable polypropylene microplastics cut Chlorella growth in half at a concentration of less than half a milligram of leachate per liter of water. Tetraselmis sp. was also affected in a concentration-dependent manner, but it required a far higher dose, with an IC50 of 37.84 milligrams per liter, roughly 77 times greater than the threshold for Chlorella.

That nearly two-order-of-magnitude difference in sensitivity between two green microalgae is one of the most technically interesting aspects of the study. It underscores why single-species toxicity tests, while useful, can be misleading when extrapolated to ecosystems. If regulators were to rely on Tetraselmis alone as a test organism, they might conclude that biodegradable polypropylene leachates pose only a modest hazard. The extreme vulnerability of Chlorella tells a different story. Species sensitivity distributions, which pool responses across many organisms, are increasingly seen as the more defensible basis for environmental risk assessment, and this study provides data points for exactly that kind of framework.

The environmental context of the work is grounded in the Indonesian archipelago, a region where plastic pollution is severe and well documented. Complementary field observations on microplastic occurrence along Indonesian coasts, cited by the authors, underscore the relevance of the laboratory findings. Previous studies have catalogued microplastics in the coastal waters of Surabaya, in mangrove sediments near Jakarta, and in fish from local markets, establishing that plastic fragments are pervasive in Indonesian marine environments. As biodegradable plastics enter those same waters, their fragmentation into microplastics and the subsequent release of leachates becomes a realistic exposure scenario rather than a theoretical one.

The new results also fit into a broader international picture. Earlier research has shown that plastic leachates can impair growth and oxygen production in Prochlorococcus, the ocean’s most abundant photosynthetic bacterium, and that leachates from weathered plastics can be more toxic than those from pristine materials. Other studies have documented leachate effects on coral fertilization, mussel larvae, and benthic invertebrates. What the Indonesian team adds is a specific demonstration that biodegradable polypropylene, a material promoted partly on the assumption that it solves the persistence problem, can generate dissolved chemicals capable of measurable sublethal harm to marine primary producers at low concentrations.

The authors are careful to frame their work as an initial toxicity assessment, and that caution is warranted. The study does not identify the specific chemical compounds responsible for the inhibition, does not examine effects beyond 96 hours, and does not test whether environmentally realistic leachate concentrations overlap with the doses that harmed Chlorella in the laboratory. Long-term, multigenerational studies, chemical characterization of the leachates, and field validation will all be needed before the ecological risk can be quantified. Nevertheless, the central message is difficult to ignore: biodegradability is not the same as harmlessness. As the world races to replace conventional plastics with alternatives, the new findings argue that every substitute material deserves the same rigorous ecotoxicological scrutiny that the originals received, before it is deployed at planetary scale.

Subject of Research: Toxicity of biodegradable polypropylene microplastic leachates to marine microalgae

Article Title: Growth and chlorophyll-a responses of marine microalgae to biodegradable polypropylene microplastic leachates: an initial toxicity assessment

Article References: Growth and chlorophyll-a responses of marine microalgae to biodegradable polypropylene microplastic leachates: an initial toxicity assessment. (n.d.). https://doi.org/10.1007/s10646-026-03157-x

Image Credits: AI Generated

DOI: 10.1007/s10646-026-03157-x

Keywords: biodegradable plastics, polypropylene, microplastics, leachates, marine microalgae, Chlorella, Tetraselmis, Navicula, chlorophyll-a, IC50, ecotoxicology, Indonesia

The economic stakes are considerable. Polysaccharides, proteins, lipids, pigments, and polyphenols harvested from marine microalgae have been shown to exhibit anti-inflammatory, antimicrobial, and antitumor activities, while pigments and unsaturated fatty acids contribute antioxidant properties and help meet human nutritional needs. Among the most commercially significant are omega-3 polyunsaturated fatty acids, a market valued at 2.3 billion US dollars in 2019 and expected to grow at an annual rate of 7.44 percent through 2027, with microalgae-derived omega-3 products growing even faster at 11.9 percent per year. High-value pigments such as lutein, beta-carotene, astaxanthin, and fucoxanthin command premium prices as natural food colorants, dietary supplements, and nutraceutical ingredients, and compounds like the polysaccharide chrysolaminarin and beta-glucan add further value to algal biomass.

There is also a pressing environmental driver behind the shift toward microalgal sources. The human body cannot synthesize the omega-3 fatty acids eicosapentaenoic acid, or EPA, and docosahexaenoic acid, or DHA, and must obtain them through diet. Traditionally these have come from fish, but overfishing has disrupted marine ecological balance, and contamination incidents have raised safety concerns about seafood products. Deep-sea fish extraction suffers from poor product stability and off-flavors, while bioaccumulation concentrates pollutants such as methylmercury, copper, polychlorinated biphenyls, and dioxins in fish bodies. Microalgae sidestep many of these problems: species such as Nannochloropsis can synthesize EPA efficiently through photosynthetic autotrophy, with the fatty acid accounting for twenty to thirty percent of total cellular lipids, and their oils are odorless, cholesterol-free, and contain squalene and phytosterols with additional health benefits.

Yet the path from algal pond to finished product is obstructed by a formidable biological barrier: the cell wall. Despite their tiny size, microalgae possess complex polysaccharide-protein composite cell walls whose high mechanical strength causes low energy efficiency and incomplete extraction with conventional disruption methods, and the variability among species means no single approach works universally. Without proper pretreatment, extraction efficiency is severely limited. The review catalogs the main pretreatment strategies in detail, dividing them into mechanical methods, including high-pressure homogenization, ultrasonication, microwave treatment, and pulsed electric fields, and chemical methods such as acid hydrolysis, surfactant treatment, and enzymatic hydrolysis. Drying itself is a pretreatment decision, with freeze-dried samples of species like Chlorella variabilis and Scenedesmus regularis typically showing higher extraction efficiency than spray-dried material, though sun drying remains the cheapest option for large volumes.

The numbers illustrate how difficult cell disruption can be. High-pressure homogenization, one of the few techniques scalable to industrial volumes, achieves only a forty percent lysis rate for Nannochloropsis even at pressures up to 900 bar. Ball milling, which uses friction and collision between microspheres to shatter cell walls, requires careful temperature control because frictional heat can inactivate delicate products; optimized conditions for the lipid-rich organism Schizochytrium sp. DT3 used beads of 0.4 to 0.6 micrometers at 4500 rpm for just four minutes. Enzymatic pretreatment offers a gentler alternative, as enzyme preparations selectively hydrolyze cell wall structures, avoid equipment corrosion, reduce energy consumption, and protect heat-sensitive compounds in a mild aqueous environment. The evidence is striking: combining the enzymes Cellulyve and Feedlyve GMA increased oil extraction from Microcystis by nearly 1.8 times, while a crude mixture of cellulase and amylase doubled protein extraction and boosted sugar extraction by 41 percent in Oocystis sp. The catch is cost, since enzyme preparations are expensive, must be matched precisely to each species’ cell wall chemistry, and demand strict control of reaction parameters.

Once cells are opened, the choice of solvent becomes the next critical decision, and this is where the green chemistry revolution is most visible. Traditional extractions rely on solvents such as chloroform, methanol, and hexane, which are volatile, flammable, explosive, or toxic. The review highlights two leading alternatives. Ionic liquids, composed entirely of cations and anions, feature low vapor pressure, high solvating power, and excellent chemical and thermal stability, and their polarity, hydrophobicity, and viscosity can be tuned by pairing different ions. Researchers evaluated fifteen cholinium and amino acid-based ionic liquids for disrupting the hydrogen-bond network of Nannochloropsis cell walls and found that cholinium arginate performed best, likely because it offers six hydrogen bonding sites. Pairing hydrophilic ionic liquids with microwave assistance increased lipid yield from Nannochloropsis oculata by 34.9 percent compared with the classic Bligh-Dyer chloroform-methanol method, and, importantly, worked on wet algae, eliminating the energy-intensive drying step.

Deep eutectic solvents, or DES, represent an even newer class of green solvents. These form when hydrogen bond acceptors such as choline chloride combine with hydrogen bond donors such as urea or lactic acid to create low-melting mixtures that are biodegradable, easy to synthesize, non-volatile, and non-flammable. Their natural variants, nDES, offer food-grade safety, meaning extracts can be used directly in food systems without solvent purification, a significant simplification of production. Responsive DES go further, allowing solvent polarity to be reversed on demand through external triggers such as pH or temperature, solving the persistent problem of separating target products from solvent. The review also covers supercritical fluid extraction, in which carbon dioxide above its critical point acts as a non-toxic solvent at near-ambient temperature, and pressurized liquid extraction, which cuts processing time by more than half while slashing solvent consumption; one PLE protocol with dimethyl sulfoxide at 103.4 bar recovered lutein, beta-carotene, fucoxanthin, and diatoxanthin from algal biomass in a single pass.

Physical intensification methods can be coupled with these solvent systems to dramatic effect. Microwave technology exploits electromagnetic energy in the 0.3 to 300 gigahertz band to rapidly heat and rupture cells, with optimized conditions of 1.47 minutes of treatment yielding efficient lutein extraction from Chlorella sorokiniana. Ultrasound generates cavitation, microfluidics, and bubble collapse that tear cell walls apart; freezing and thawing combined with ultrasonication pushed C-phycocyanin yield to 109.57 milligrams per gram, well above either technique alone and with the highest purity. A triphasic separation strategy applied to wet marine Chlorella sp. NITT 02 used ultrasonication followed by ammonium sulfate and tert-butanol to split biomass into an oil layer, a protein layer, and a sugar-containing salt layer in one operation. However, the review is candid that green extraction remains difficult: ethanol is less toxic than methanol or chloroform but delivers lower yields, and microwave and ultrasound processes are energy-intensive or limited in scale.

Economics ultimately decide which technologies survive, and here the authors turn to life cycle assessment, a four-step framework covering goal definition, inventory analysis, impact assessment, and interpretation. The figures are sobering: freeze-drying consumes about 1080 megajoules, ultrasonic disruption 108 to 324 megajoules, and solvent recovery 210 to 588 megajoules, while harvesting costs a mere 0.02 megajoules. A multi-product roadmap for marine Chlorella variabilis showed sugar extraction as the most energy-hungry step at 160.8 megajoules per kilogram, compared with just 5.9 for lipid extraction and 5.2 for harvesting. The authors argue that complete separation of every component is unnecessary; extracting only the highest-value products and converting residues through fermentation or thermal conversion achieves better economics, and integrating cultivation with wastewater treatment further improves sustainability.

Perhaps the most forward-looking section of the review concerns artificial intelligence and computational screening. Extraction obeys thermodynamic principles, but phase equilibrium data for multi-component systems containing salts, ionic liquids, and polymers remain scarce, making solvent selection largely empirical. Theoretical tools such as COSMO-RS have guided the design of solvents for extracting lutein, phycobiliproteins, EPA, fucoxanthin, and lipids, with researchers screening databases of roughly 8,000 molecules and narrowing thousands of candidate deep eutectic solvents down to 712 using constraints on boiling point, melting point, greenness, and solubility. Machine learning applied to the wealth of existing laboratory data promises to close the loop between experimental science, theoretical calculation, and AI analysis, accelerating solvent discovery. The authors identify three priorities for the field: standardized pilot-scale extraction test suites, quantified solvent life-cycle impacts, and open databases of extraction yields for machine learning training. If those pieces fall into place, the green extraction of marine microalgal compounds could finally deliver on the promise of blue biotechnology at industrial scale, turning sunlight, seawater, and carbon dioxide into medicines, supplements, and sustainable materials.

Subject of Research: Green extraction of bioactive compounds from marine microalgae

Article Title: Green extraction of active compounds in marine microalgae

Article References: Green extraction of active compounds in marine microalgae. (n.d.). https://doi.org/10.1186/s44315-025-00051-9

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00051-9

Keywords: marine microalgae, green extraction, ionic liquids, deep eutectic solvents, supercritical CO2, pressurized liquid extraction, cell disruption, omega-3 fatty acids, bioactive compounds, blue biotechnology, life cycle assessment, machine learning