The research team, led by Vitória G. Navarrete of São Paulo State University and Ana T. Lombardi of the Federal University of São Carlos, set out to answer three questions: Can microalgae be cultivated in 100 percent vinasse? How does algal growth change vinasse’s organic composition? And can vinasse-grown cultures serve as inoculum for successive cultivation cycles? The answers carry real weight for the circular bioeconomy, because microalgae can simultaneously remediate wastewater and produce biomass for biofuels, pigments, and animal feed.

The vinasse came from Usina Santa Lucia in Araras, São Paulo, and was treated using a patented method (INPI BR 102015024100-3) that percolates the effluent sequentially through coarse sand, smectite clay, and activated carbon. This low-cost filtration retained particulate material, reduced turbidity, and adjusted the pH from 4.0 to about 7.0—converting the dark, opaque waste into a light, translucent liquid that allows light to penetrate, a prerequisite for photosynthetic growth. Crucially, the treatment preserved both inorganic and organic nutrients, and no sterilization was performed, so bacteria and yeasts remained in the effluent, forming a microbial consortium with the algae.

Nine microalgal species were first screened in 96-well microplates across vinasse concentrations from 50 to 100 percent. Three species—Chlorolobion braunii, Tetradesmus sp., and Haematococcus pluvialis—were selected for detailed testing in 6-well plates containing 12 milliliters of full-strength treated vinasse. The researchers compared three treatments: control cultures in BG11 synthetic medium, vinasse cultures inoculated from BG11-grown cells (V1), and vinasse cultures inoculated from cells already growing in vinasse (V2). Growth was monitored daily by cell counts under an optical microscope and by absorbance measurements.

The standout performer was C. braunii. In the V1 treatment it achieved a specific growth rate of 1.3 per day—nearly twice the 0.7 per day measured in its BG11 control, and roughly double the rates of Tetradesmus sp. (0.66 per day) and H. pluvialis (0.68 per day). Because C. braunii was the only species that grew faster in vinasse than in synthetic medium, the authors concluded it was performing mixotrophic growth, using dissolved organic carbon in the effluent as a supplementary energy source alongside photosynthesis. Mixotrophy makes irradiance less restrictive and enables algal growth in darker media, which matters industrially because organic substrates reduce dependence on light penetration.

Cell morphology told a more nuanced story. Using mixed-effects modeling on measurements of 30 cells per replicate, the team found that cell volume increased 1.6-fold in vinasse-grown C. braunii (208 cubic micrometers) and 6.3-fold in Tetradesmus sp. (250 cubic micrometers) compared with controls. H. pluvialis maintained its volume (5,575 cubic micrometers). The researchers interpret the enlarged cells as a stress response: increasing cell volume decreases the surface-area-to-volume ratio, reducing the uptake of nutrients and toxicants. Consistent with this, larger cells divided more slowly, reflected in lower growth rates—a pattern previously documented for microalgae exposed to toxic compounds such as copper and glyphosate.

The inoculum origin experiment revealed striking species-specific differences. When the inoculum came from vinasse-grown cells (V2), C. braunii’s growth rate dropped 3.2-fold to 0.4 per day and its cells became larger, reaching 1,073 cubic micrometers. Tetradesmus sp., by contrast, showed no variation in growth response—0.67 per day in V2 versus 0.66 per day in V1—though its cell volume ballooned 13.2-fold compared with the control. H. pluvialis responded to V2 by forming small cysts, a characteristic stress response of this species, and its maximum cell density fell about 60 percent below that of the control and V1 treatments.

Nuclear magnetic resonance (NMR) spectroscopy provided the chemical detective work. The ¹H NMR spectrum of raw vinasse showed signals of butyrate, isobutyrate, ethanol, acetate, succinate, isocitric acid, methanol, and 1,2-propanediol. After algal growth, acetate and butyrate signals dropped dramatically—acetate fell from 0.6754 to about 0.01 arbitrary units across all three species—indicating consumption by the microbial consortium. Acetate is a well-known inducer of mixotrophic metabolism in microalgae, while butyrate tolerance is species-dependent; previous screening of ten strains found nine experienced stress on butyrate. The vinasse’s indigenous bacteria, dominated by genera such as Lactobacillus, Megasphaera, and Bifidobacterium, can both produce and consume these volatile fatty acids, so the consortium’s metabolism likely shaped the effluent’s chemistry alongside the algae.

The most intriguing NMR finding was exclusive to H. pluvialis cultures: the appearance of cis-aconitate, a tricarboxylic acid cycle intermediate never detected in raw or treated vinasse, nor in the media of the other two species. Aconitic acid is naturally present in sugarcane vinasse but was removed during treatment. Literature shows that high light intensity, high salinity, or nitrogen starvation can drive H. pluvialis to excrete cis-aconitate to prevent mitochondrial imbalance and balance the cell’s redox state. Combined with its 60 percent growth reduction, the cis-aconitate release confirms that H. pluvialis cells were under physiological stress in vinasse. Meanwhile, citric acid present in treated vinasse was depleted after C. braunii and Tetradesmus sp. cultivation but persisted in the H. pluvialis medium, suggesting the former two assimilated it while the latter struggled at the aconitase step of the citric acid cycle.

The study’s conclusion is pragmatic: full-strength treated vinasse can serve as a viable culture medium for microalgae, but success hinges on species selection. C. braunii ranks as the most successful organism in the effluent, followed by Tetradesmus sp. and then H. pluvialis. Tetradesmus sp.’s indifference to inoculum origin makes it a robust candidate for industrial applications, since vinasse-grown cultures could seed successive cycles without synthetic medium, simplifying inoculum production and reducing operational costs. The authors caution that the microplate-scale systems used here still need verification at larger volumes, where dead zones and light variation differ from controlled laboratory conditions. Future work should focus on scaling up culture volumes to evaluate biomass and biomolecule productivity. If those hurdles are cleared, the ethanol industry could close a remarkable loop: turning its most troublesome waste stream into algae, and algae into fuel, feed, and pigment.

Subject of Research: Growing microalgae in treated vinasse: effects on cell morphology and growth rate

Article Title: Growing microalgae in treated vinasse: effects on cell morphology and growth rate

Article References: Navarrete, V. G., Ferreira, V. S., Venâncio, T., Pulgrossi, R. C., Branco, L. H. Z., & Lombardi, A. T. (2026). Growing microalgae in treated vinasse: effects on cell morphology and growth rate. Frontiers in Industrial Microbiology, 4, Article 1917607. https://doi.org/10.3389/finmi.2026.1917607

Image Credits: AI Generated

DOI: 10.3389/finmi.2026.1917607

Keywords: microalgae, vinasse, circular economy, bioremediation, mixotrophy, ethanol industry, Growing, treated, effects, cell, morphology, growth

The team worked with three ecologically important single-celled predators: Oxyrrhis marina, a purely heterotrophic dinoflagellate; Karlodinium armiger, a mixotrophic dinoflagellate that can both eat prey and photosynthesize; and Strombidium arenicola, a heterotrophic ciliate. Each was exposed to two thermal scenarios, both three degrees Celsius above control conditions: a chronic warming treatment and an acute heat stress designed to mimic a marine heatwave. In parallel, the protists were fed prey with either balanced, nutrient-replete cellular stoichiometry or imbalanced, nutrient-limited stoichiometry, produced under nitrogen or phosphorus limitation. This factorial design allowed the researchers to disentangle how temperature and food quality interact, rather than merely add up.

The baseline result was deceptively straightforward. When prey were nutrient-replete, physiological rates increased under both warming treatments in all three species, consistent with the expectation that higher temperatures accelerate metabolic processes within thermal tolerance limits. Yet a subtler signal emerged in gross-growth efficiency, the fraction of ingested food converted into new biomass. In the two heterotrophs, this efficiency remained insensitive to temperature, but in the mixotrophic K. armiger it declined under warming. That distinction matters because gross-growth efficiency is a key currency in food-web models: if mixotrophs convert less of what they consume into growth as seas warm, energy transfer through microbial loops could shift in ways models have not anticipated.

Nitrogen limitation produced one of the study’s most counterintuitive findings. Under N-limited diets, both warming treatments generally increased growth rates in all protists while reducing ingestion rates relative to nutrient-replete conditions. In other words, the organisms ate less but grew proportionally better, and gross-growth efficiencies remained similar to or even higher than those measured with balanced diets. The authors interpret this as evidence that protists can partially compensate for poor food quality, extracting what they need from nutritionally diluted prey when temperatures push their metabolism along. For a warming ocean increasingly characterized by altered nutrient regimes, this suggests nitrogen stress alone may not cripple these predators as sharply as feared.

Phosphorus told a harsher story. P limitation reduced growth rates in the heterotrophs under both warming scenarios, with the ciliate S. arenicola suffering the most pronounced declines. The mixotroph K. armiger, by contrast, showed overall performance under phosphorus scarcity that was similar to its performance on nutrient-balanced food. This resilience likely reflects two factors highlighted by the authors: the weaker elemental regulation of dinoflagellates, which allows them to tolerate drift in their own carbon-to-nutrient ratios, and, in the case of K. armiger, its capacity to supplement its diet through photosynthesis when prey fall short. Mixotrophy, often treated as an ecological curiosity, here looks like a functional insurance policy against the worst-case combination of heat and phosphorus-poor food.

Cell size, a trait that cascades through food webs because it governs who can eat whom and how fast materials sink, responded in patterned ways. Under nutrient-replete conditions, cell volume decreased in all species under both warming treatments, echoing the well-documented tendency of plankton to shrink as temperatures rise. Under phosphorus limitation, however, cells were largest in all three protists, although the temperature responses varied among species. Larger, phosphorus-stressed cells may reflect slower division rates that allow biomass to accumulate, or dilution of cellular phosphorus across a bigger volume, a known strategy of weak elemental regulators stretching scarce nutrients.

The stoichiometric measurements sharpened the picture. Under phosphorus limitation, carbon-to-phosphorus and nitrogen-to-phosphorus ratios increased significantly in all species, confirming that P-starved protists become proportionally richer in carbon and nitrogen relative to phosphorus. Crucially, however, the combined effects of temperature and nutrient stress on these ratios differed among the three protists, meaning no single rule can describe how microbial body chemistry will shift as oceans warm and nutrients redistribute. This interspecific variability complicates biogeochemical modeling, because the elemental composition of microzooplankton influences the quality of organic matter recycled back into the water column and ultimately the efficiency of the biological carbon pump.

Synthesizing these threads, the authors conclude that among the species examined, the two dinoflagellates may be more tolerant of combined thermal and nutrient stress than the ciliate S. arenicola. Their greater tolerance may stem from weaker elemental homeostasis, letting them flex their internal chemistry as conditions change, and, for K. armiger specifically, from its mixotrophic capacity, particularly under phosphorus limitation and acute heat stress. The ciliate, apparently a stricter regulator of its own composition, had less slack to absorb the double insult. If such differences hold across broader communities, warming and nutrient stress could quietly reshuffle the dominance hierarchy of the microbial plankton, favoring dinoflagellates over ciliates in future oceans.

The broader implications reach well beyond three laboratory cultures. Protists in the microzooplankton are the principal grazers of phytoplankton in much of the ocean, channeling primary production into higher trophic levels and recycling nutrients in surface waters. Their growth efficiencies, body sizes, and elemental ratios collectively determine how much carbon is respired back to CO2, how much is packaged into sinking particles, and how nutritious the microbial food web is for fish larvae and other consumers. A study like this one shows that those quantities cannot be predicted from temperature alone or food quality alone; the interaction terms are large, species-specific, and sometimes opposite in sign depending on which nutrient is limiting.

There are also methodological lessons for the field. By combining chronic warming with an acute heatwave treatment, the design mirrors the reality of a climate that brings both gradual baseline warming and increasingly frequent extreme events. By manipulating prey stoichiometry independently of temperature, it isolates a variable that most thermal-performance experiments ignore. The work, conducted within the Marine Zooplankton Ecology Laboratory at ICM-CSIC and funded through Spanish national research programs including grants PID2020-118645RB-I00 and PID2023-150548NB-I00, was supported in part by the Severo Ochoa Centre of Excellence accreditation. As marine heatwaves lengthen and stratification tightens nutrient supply in many regions, experiments of this kind offer an early warning of how the ocean’s smallest predators, and the food webs they anchor, may reorganize in the decades ahead.

Subject of Research: Combined effects of temperature and prey nutrient limitation on the physiology of marine heterotrophic and mixotrophic protists

Article Title: Combined Effects of Thermal and Diet-Induced Stressors on the Physiology of Marine Heterotrophic and Mixotrophic Protists

Article References: García-Martínez, M., Saiz, E., & Calbet, A. (2026). Combined Effects of Thermal and Diet-Induced Stressors on the Physiology of Marine Heterotrophic and Mixotrophic Protists. Microbial Ecology. https://doi.org/10.1007/s00248-026-02912-1

Image Credits: AI Generated

DOI: 10.1007/s00248-026-02912-1

Keywords: marine protists, dinoflagellates, ciliates, ocean warming, marine heatwaves, nutrient limitation, stoichiometry, mixotrophy, microzooplankton, gross-growth efficiency, biogeochemical cycles, plankton ecology

The discovery comes from a team led by microbiologists Bettina Glasl and Katharina Kitzinger at the Centre for Microbiology and Environmental Systems Science at the University of Vienna, working in collaboration with partners at the Australian Institute of Marine Science. Their findings, published in the journal Science Advances, describe how archaea living in partnership with the elephant ear sponge Ianthella basta supplement their ammonia-based diet with branched-chain amino acids, including valine, leucine, and isoleucine. In doing so, the microbes behave less like rigid specialists and more like what the researchers playfully call flexitarians, organisms that prefer one food source but readily incorporate others when the opportunity arises. The result reshapes how scientists think about one of the oldest animal-microbe partnerships on Earth.

Marine sponges are among the most ancient animals still swimming in the oceans, and their bodies are anything but simple. A single sponge can host billions of microorganisms packed into its internal channels, forming a symbiotic community that is essential to the animal’s survival. Among these residents, ammonia-oxidizing archaea hold a place of particular importance. Sponges constantly produce ammonia as a metabolic waste product, and in the confined chemistry of a reef organism this compound would quickly become toxic. The archaea act as a microscopic sanitation crew, oxidizing ammonia and keeping the sponge’s internal environment habitable. This service has long been considered their defining role, and their nutritional identity seemed equally settled.

Until now, the textbook view held that ammonia-oxidizing archaea were strict chemolithoautotrophs. The term describes a demanding lifestyle: the organism must generate all of its energy from inorganic chemical reactions, in this case the oxidation of ammonia to nitrite, while simultaneously fixing carbon dioxide into the organic molecules of life. Free-living ammonia oxidizers studied in soils and oceans have occasionally shown modest flexibility, using simple nitrogenous compounds such as cyanate and urea as additional nitrogen sources, but their carbon metabolism remained firmly anchored to carbon dioxide. The sponge symbionts, the new work demonstrates, have gone considerably further down the path of dietary liberation.

The first hints of this flexibility came not from experiments but from genomes. When researchers sequenced the DNA of symbiotic ammonia-oxidizing archaea from sponges, they noticed something odd: unlike many of their free-living relatives, these symbionts carried genes encoding transporters for branched-chain amino acids. Transporters are membrane proteins that import specific molecules from the environment, and their presence suggested the archaea might be equipped to take up valine, leucine, and isoleucine from their surroundings. Genome predictions, however, are only hypotheses. A transporter gene does not prove that the protein works, that the amino acids are actually available inside the sponge, or that the symbionts use them for growth. Direct experimental evidence was needed.

Providing that evidence required the researchers to watch individual microbial cells at work inside a living animal, a formidable technical challenge. The team studied the bright yellow elephant ear sponge, a species found across coral reefs of the Indo-Pacific, including the Great Barrier Reef, and its archaeal symbiont Nitrosospongia ianthellae. They combined advanced chemical and microscopic imaging techniques, including nanoscale secondary ion mass spectrometry, or NanoSIMS, a method capable of detecting isotopically labeled compounds incorporated into single cells. By offering the symbionts amino acids tagged with heavy isotopes, the researchers could trace exactly which cells absorbed the molecules and incorporated them into their biomass.

The imaging delivered an unambiguous answer. As Kitzinger explained, the labeled amino acids could be seen being incorporated into individual symbiont cells, allowing the team to link a cell’s identity directly to its function rather than relying on genome predictions alone. This single-cell approach matters because sponge tissue is a crowded, mixed community of bacteria, archaea, and host cells. Bulk measurements of labeled material in sponge tissue cannot reveal who ate what. By resolving activity at the level of individual archaeal cells, the study provided the first direct experimental demonstration that symbiotic ammonia oxidizers are genuine mixotrophs, organisms capable of using both carbon dioxide and organic amino acids as carbon sources.

The implications extend well beyond a revised dinner menu. Because the symbionts can both consume and produce branched-chain amino acids, they may actively shape the availability of these essential molecules within their host. Branched-chain amino acids are not merely building blocks for proteins; in animals they also act as signaling compounds. The researchers propose that archaeal metabolism could even influence the mTOR signaling pathway, a conserved regulator of cell growth and metabolism that responds to branched-chain amino acid availability in organisms across the tree of life. If the archaea modulate the supply of these molecules, they could, in principle, participate in chemical conversations with the sponge itself, a possibility that transforms them from passive waste processors into active metabolic partners.

Glasl captured the shift in perspective by noting that these symbionts were previously viewed primarily as a waste disposal service for the sponge. By producing and consuming amino acids that may serve as signaling molecules, she observed, the symbionts could potentially modulate important signals for their host, suggesting a form of communication between microbes and animals with deep evolutionary roots. Sponges and their microbial communities have coexisted for hundreds of millions of years, and the new findings hint that this partnership may involve far richer chemical exchange than the simple removal of toxic waste. Michael Wagner, head of the FWF Cluster of Excellence that supported the work and last author of the study, emphasized that the research depended on tight collaboration between teams in Austria and Australia.

Beyond the sponges, the study raises broader questions about archaeal ecology in the ocean. If symbiotic ammonia oxidizers can tap organic compounds, other members of this ancient lineage may harbor similar capacities that have gone undetected because researchers assumed a purely inorganic diet. The work also underscores how symbiosis can drive metabolic innovation: an organism’s lifestyle inside a host can differ dramatically from that of its free-living cousins. For a group of microbes once considered the strictest of specialists, the sponge archaea offer a reminder that microbial nutrition, like the animals these organisms inhabit, is often stranger, older, and more interconnected than it first appears.

Subject of Research: Mixotrophic amino acid assimilation by ammonia-oxidizing archaeal symbionts of marine sponges

Article Title: Archaea as "flexitarians": ammonia-oxidizing microbes also feed on amino acids

Article References: Archaea as "flexitarians": ammonia-oxidizing microbes also feed on amino acids. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: archaea, marine sponges, symbiosis, ammonia oxidation, amino acids, mixotrophy, NanoSIMS, microbiome, coral reefs, mTOR signaling, Nitrosospongia, Science Advances

The review, led by Ramón Damián Morejón-Arrojo of the Institute of Marine Science in Havana together with colleagues in the United States and Spain, synthesizes decades of scattered research into a single framework for understanding the genus. Cassiopea comprises roughly twelve confirmed species distributed across the tropical and subtropical waters of the Atlantic, Indian and Pacific Oceans, inhabiting coral reefs, mangroves, seagrass meadows and coastal lagoons. Yet the authors found that field-based studies make up only about fourteen percent of the roughly 195 papers published on the genus between 1774 and 2023, and most of that fieldwork has been concentrated in the Western Atlantic, leaving the global ecology of these animals poorly understood.

The key to Cassiopea’s success lies in its biology. Unlike most jellyfish, which drift through the water column, Cassiopea medusae rest bell-down on the substrate with their frilly oral arms pointing upward, maximizing the sunlight that reaches the millions of dinoflagellate algae living inside their tissues. These symbionts, members of the family Symbiodiniaceae, supply up to seventy percent of the jellyfish’s basal energy requirements through photosynthesis. The partnership is so essential that the algae are required for strobilation, the process by which a sessile polyp transforms into a free-swimming juvenile medusa. Without the symbionts, the life cycle simply cannot complete in nature.

That dependence shapes every stage of development. Cassiopea medusae are usually gonochoric, meaning they have separate sexes, and fertilization occurs inside the female’s gastrovascular system. Embryos develop on the oral disc, become ciliated within about forty-eight hours, and by ninety-six hours form swimming planula larvae that eventually settle and metamorphose into polyps. Polyps reproduce asexually by releasing planuloid buds at a rate of two to three per day, and they acquire their algal symbionts only after settling. Larval settlement itself is triggered by specific bacteria such as Pseudoalteromonas and Vibrio and by compounds released from degrading red mangrove leaves, including a peptide of roughly 5.8 kilodaltons. Strobilation typically begins about three weeks after settlement and infection, generally at temperatures above twenty-eight degrees Celsius, and does not occur at twenty degrees or below even when food is abundant.

As adults, the jellyfish are mixotrophs, combining photosynthetic nutrition with active predation. Their bell pulses up to fifty times per minute, drawing water and prey into the space between the subumbrella and the oral arms, where finger-like structures called digitata armed with nematocysts intercept small animals. Gut-content analyses across Panama, Florida, Cuba, the Philippines, Italy and Australia show a remarkably consistent diet dominated by epibenthic crustaceans, especially harpacticoid copepods, along with ostracods, tanaids, mysids, nematodes and other small invertebrates. Larger medusae consume more prey, and the same pulsing that captures food also serves respiration, waste removal, gamete dispersal and the mobilization of nutrients from sediment pore waters, which in turn may boost the productivity of the algal symbionts.

It is this relentless pumping that gives Cassiopea its reputation as an ecosystem engineer. In habitats with little water movement, such as mangrove systems, the jellyfish act as living pumps that mix the water column and draw nutrient-rich interstitial water out of the sediment. They function as hotspots of nutrient excretion and oxygen consumption in the dark, and as oxygen producers and nutrient assimilators in the light, with effects on ammonium regeneration and oxygen concentrations that follow the daily rhythm of their symbionts’ photosynthesis. Their pulsations also release copious mucus loaded with dissolved organic matter, including proteins, lipids and carbohydrates, which fuels microbial growth and shapes biogeochemical cycling in the surrounding water.

The same sensitivity to its environment that makes Cassiopea an engineer also makes it a sentinel. The jellyfish respond rapidly to elevated metals and nutrients, and their tissues can accumulate trace metals such as lithium, copper, manganese and zinc at concentrations up to two hundred times those found in seawater. They have been used as models in ecotoxicological studies of herbicides such as atrazine and hexazinone, and microplastics have been detected in specimens from Florida estuaries, apparently trapped in their oral arms rather than ingested. Remarkably, in polluted habitats the jellyfish appear to tolerate contamination by shifting toward anaerobic metabolism, with elevated activity of glycolytic enzymes such as pyruvate kinase and lactate dehydrogenase allowing energy production even under low-oxygen stress, an adaptation that lets them thrive where many other invertebrates decline.

That tolerance helps explain a troubling pattern: Cassiopea blooms are increasingly associated with human-impacted coasts. Nutrient enrichment from agricultural runoff and coastal development correlates with high densities, with the highest reported abundance reaching about 106 individuals per square meter in Codrington, Barbuda, compared with as little as 0.06 per square meter in Lake Macquarie, Australia. Densities this high can alter benthic invertebrate communities, reduce seagrass cover, and compete with vegetation for light, since the jellyfish often rest directly on top of seagrass shoots. The review also documents an inverse relationship between population density and average bell diameter, likely reflecting competition for prey and nutrients at high densities, although nutrient loading can partially offset this constraint by boosting individual growth.

The genus is also expanding its range, and human activity appears to be a major driver. Invasions have been recorded in Australia, India, Vietnam, the Cape Verde and Canary Islands, the Mediterranean, Hawaii, Brazil and the Caribbean, and one hypothesis links the Indo-Pacific spread to the movement of United States naval vessels during the Second World War. Modified coastal habitats such as marinas and shrimp farms act as springboards for establishment, offering stable food supplies and the higher lipid reserves that support survival during unfavorable conditions. The jellyfish’s environmental tolerance is impressive: they survive temperatures up to thirty-six degrees Celsius, salinities near forty-seven practical salinity units, and pH as low as seven, and they can shrink under starvation or low light and regrow when conditions improve.

Climate change, however, tests even this resilience. Because Cassiopea depends on dinoflagellate symbionts, it is vulnerable to the same thermal bleaching that devastates coral reefs. Bleached individuals have been recorded in Singapore, in a Saudi Arabian lagoon during a historical temperature record of forty-four degrees Celsius, and on the north coast of Havana in 2023, when an asymmetric bleaching event affected 0.44 percent of jellyfish during a heatwave. Recent physiological work shows that bleaching compromises the expression of glucose and glycerol transporters, limiting energy availability during recovery, while symbiont genotype matters: jellyfish hosting Durusdinium species tolerate heat better but receive less carbon than those hosting Symbiodinium, a trade-off between survival and growth. Even pigmentation appears to matter, as specimens with blue appendages showed higher survival under acute heat stress.

The Western Atlantic remains the best-studied region, encompassing both native and invasive populations across the Bahamas, Barbuda, Cuba, Mexico, the Florida Keys and Puerto Rico, and the review’s authors argue that this region offers the richest dataset for understanding the genus’s ecological roles. But they emphasize that the field’s future lies elsewhere. Only by extending research beyond the Western Atlantic, integrating ecological, physiological and molecular approaches, and monitoring the growing frequency of blooms can scientists predict how these inverted jellyfish will reshape tropical and subtropical ecosystems in a rapidly changing ocean. For now, the animal lying quietly on the lagoon floor, pumping water, feeding microbes and accumulating pollutants in its tissues, is revealing itself as one of the most multifaceted small players in the coastal sea.

Subject of Research: Ecological roles of the upside-down jellyfish genus Cassiopea in tropical marine ecosystems

Article Title: Life upside-down: review of ecological roles of Cassiopea (Cnidaria: Scyphozoa) in marine ecosystems—a look at the Western Atlantic

Article References: Morejón-Arrojo, R. D., Mammone, M., López-Figueroa, N. B., Stoner, E. W., & Rodríguez-Viera, L. (2025). Life upside-down: review of ecological roles of Cassiopea (Cnidaria: Scyphozoa) in marine ecosystems—a look at the Western Atlantic. Discover Ecology, 1(1), Article 7. https://doi.org/10.1007/s44396-025-00006-9

Image Credits: AI Generated

DOI: 10.1007/s44396-025-00006-9

Keywords: Cassiopea, upside-down jellyfish, Scyphozoa, Symbiodiniaceae, mixotrophy, symbiosis, ecosystem engineer, bioindicator, jellyfish blooms, Western Atlantic, climate change, marine ecosystems