The story begins with the plastisphere, the term coined for the communities of bacteria, algae, fungi, and other microbes that rapidly form biofilms on plastic debris once it enters aquatic environments. Diatoms are consistently among the earliest and most successful colonizers of these artificial surfaces. Because plastics are buoyant, long-lived, and chemically inert compared with natural substrates, they offer diatoms a novel and stable ecological niche in the sunlit surface ocean. Field surveys from the Black Sea to intertidal habitats worldwide, along with laboratory mesocosm experiments, have repeatedly documented genera such as Chaetoceros, Thalassiosira, Skeletonema, Navicula, and Nitzschia dominating plastic-associated biofilms, sometimes outcompeting every other photosynthetic organism on the particle.

What makes this dominance ecologically significant is that many of these same diatom genera are well known as producers of oxylipins, a family of lipid-derived defensive chemicals. When diatom cells are damaged, for example when a copepod crunches them during feeding, enzymes called lipoxygenases are released and convert membrane fatty acids into a diverse array of oxylipins, including polyunsaturated aldehydes and linear oxygenated fatty acids. Decades of laboratory and field research have shown that these compounds are teratogenic to copepods: they reduce egg production, impair hatching success, and can kill nauplii outright, sometimes with devastating effects on entire cohorts. In extreme cases documented in the literature, diets rich in oxylipin-producing diatoms such as Skeletonema marinoi have led to one hundred percent naupliar mortality.

Copepods, meanwhile, occupy a pivotal position in ocean ecology. With roughly thirteen thousand described species, they can make up seventy to ninety percent of mesozooplankton abundance in many regions, forming the critical link between phytoplankton and commercially important fish, marine invertebrates, and even cetaceans. They also play a major role in the ocean carbon cycle, packing organic material into dense fecal pellets that sink rapidly and transporting carbon through their daily vertical migrations. Because copepods passively entrain particles of suitable size into their feeding currents, they readily ingest microplastics that overlap in dimensions with their natural prey such as diatoms, dinoflagellates, and ciliates.

The consequences of this ingestion are well documented. Laboratory studies have shown that exposure to microplastic concentrations as low as fifty particles per milliliter can alter copepod feeding behavior, prey selection, reproductive output, molting cycles, and lipid production. In the copepod Acartia tonsa, polystyrene beads administered during egg formation produced smaller eggs, reduced naupliar survival, and population models projecting a thirty-fold decline over twenty generations. Molecular analyses reveal that microplastic ingestion triggers oxidative stress pathways involving MAPK and Nrf2 signaling, drains cellular energy reserves, and compromises swimming performance. Fecal pellets produced by exposed copepods become smaller and sink more slowly, potentially weakening the biological pump that carries carbon to the deep ocean.

The striking observation at the heart of the new review is that these microplastic effects closely resemble those historically attributed to oxylipin-producing diatoms. Reduced egg viability, impaired hatching, naupliar mortality, and disrupted maternal investment appear in both bodies of literature. Donnarumma and Russo propose that the overlap may not be coincidental. When a copepod ingests a plastic particle densely colonized by diatoms, the mechanical crushing of those cells during digestion could liberate lipoxygenases that then react with polyunsaturated fatty acids from any of the other organisms in the gut, whether eukaryotic or prokaryotic, generating oxylipins on the spot. In effect, the plastic particle would function as a chemical weapon factory inside the grazer.

Biofouling makes this scenario more plausible rather than less. Experiments consistently show that copepods ingest aged, biofilm-coated microplastics more readily than pristine particles, apparently because microbial colonization makes the plastic smell and behave more like food. Biofilm-derived infochemicals can even act as foraging cues that attract grazers. Meanwhile, nutrient limitation, a condition that increases oxylipin production in diatoms, also drives diatoms to over-secrete adhesive extracellular polymeric substances, making their biofilms stickier and more robust on plastic surfaces. The result is a particle that is simultaneously more attractive to copepods and more chemically loaded with potential toxin producers.

The authors are careful to stress that no study has yet directly demonstrated oxylipin synthesis by epiplastic diatoms on plastic debris. Their framework remains a hypothesis, albeit one grounded in converging lines of indirect evidence. To test it, they propose a clear experimental roadmap: culture an oxylipin-producing species such as Skeletonema marinoi on plastic debris, extract and characterize the resulting metabolites using liquid chromatography with tandem mass spectrometry, and compare copepod responses to sterile versus diatom-colonized particles. Adult females would be exposed to four treatments, healthy diets, free-living diatoms, sterile microplastics, and colonized microplastics, with hatching success and gene expression serving as key endpoints. Field surveys using fine neuston nets, rather than the standard manta nets that miss the relevant size fractions, would then establish whether the mechanism operates in nature.

The stakes extend well beyond copepod physiology. If plastic-borne oxylipins compound the reproductive failures already observed in laboratory studies, population-level consequences could ripple upward through marine food webs, reducing prey availability for fish larvae and other consumers. Disruption of copepod-mediated carbon export could further alter the efficiency of the biological pump, with implications for climate-relevant biogeochemical cycles. The authors also highlight a glaring geographic bias in existing research toward the Northern Hemisphere, leaving the Southern Ocean and much of the tropics as data deserts in which the combined stress of microplastics and epiplastic chemistry remains entirely unquantified.

For now, the review reframes microplastic pollution as a dual threat: a physical and nutritional burden on grazers, and a potential vector for chemical stress generated by the living communities that plastics carry with them. Whether that second threat is real in the ocean will depend on the experimental and field campaigns the authors now call for, but the convergence of evidence they assemble makes the hypothesis one of the most intriguing new directions in marine chemical ecology.

Subject of Research: Microplastics as potential vectors of diatom-derived oxylipins affecting copepod physiology and reproduction

Article Title: Microplastics as potential vectors of diatom oxylipins and possible effects on copepods

Article References: Donnarumma, V., & Russo, E. (2026). Microplastics as potential vectors of diatom oxylipins and possible effects on copepods. Discover Ecology, 2(1), Article 11. https://doi.org/10.1007/s44396-026-00029-w

Image Credits: AI Generated

DOI: 10.1007/s44396-026-00029-w

Keywords: microplastics, plastisphere, diatoms, oxylipins, copepods, marine chemical ecology, biofilms, copepod reproduction, biological pump, marine pollution, Skeletonema marinoi, zooplankton

The work, led by Casey B. Butler of Florida International University and the Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute, together with Cheyne M. Springbett and Alastair R. Harborne, set out to test a long-standing but unverified idea. Field surveys had already shown that snail abundance tends to be lower where lobster densities are high, and protected areas with intact predator communities support fewer corallivores than fished reefs. But correlation is not mechanism: lobsters might simply suppress corallivores by eating them, or thriving lobster populations and sparse snail populations might both reflect the same high-quality reef habitat. Whether corallivores actually behave as if lobsters were dangerous — a non-consumptive, risk-induced response — had never been directly tested.

Corallivory matters because live coral tissue is a finite and increasingly scarce resource. Coralliophila galea can strip between roughly 1 and 10 square centimeters of tissue per day from key restoration species such as elkhorn coral, preferentially attacks corals that are already stressed or diseased, and can facilitate the transmission of coral diseases. The bearded fireworm is a more generalist feeder, but its grazing causes disproportionate tissue necrosis and it has been implicated as a vector of coral disease. Current management of both pests relies on divers physically removing them from restoration sites — a labor-intensive approach that works at the scale of an outplanted patch but is hopeless across an entire reef system. If predator presence alone could keep corallivores away from corals, restoration practitioners would gain a self-sustaining, ecologically grounded alternative.

To isolate the effect of chemical cues, the team ran choice experiments in custom-built clear PVC chambers, each 61 centimeters long, with lobster-conditioned seawater flowing in from one end and clean control seawater from the other. Lobsters were fed at least an hour before each trial to ensure urine production — the presumed carrier of predator odor — and then incubated in head tanks for eight hours. A central entrance port delivered the test animal into a mixing zone where the two plumes met, and the animals’ positions were recorded overnight under infrared light, since all three species are nocturnal. No coral, food, or shelter was provided inside the chambers, deliberately removing any confounding attraction and leaving only the chemical landscape of risk. Side assignments were randomized by coin flip, and preliminary trials with control water on both sides confirmed the chambers themselves carried no bias.

The results split cleanly between the two corallivores and, surprisingly, between the two lobster species. Fireworms exposed to P. argus odor showed what the authors characterize as active flight behavior: about 75 percent chose the control side, only 22 percent entered the lobster side, and video-tracking showed individuals typically made a single, rapid decision — within a median of one minute — and then held their position for the rest of the hour-long trial. Their time budgets told the same story, with a median of 98.5 percent of trial time spent in the control zone. Snails responded differently. Confronted with P. argus odor, nearly half initially selected the control side while only 7 percent moved toward the lobster cue, a statistically significant immediate avoidance. But over the course of the eleven-hour trial the initial avoidance weakened: snails increasingly congregated in the central mixing zone, which dye tests showed still carried a diluted cue, rather than holding the control side outright.

The authors interpret the snails’ behavior cautiously. For a slow-moving gastropod, staying put is not necessarily a non-response; minimizing movement is a well-documented antipredator strategy across taxa, lowering detection risk at the cost of foraging opportunity, and the pattern was consistent with sheltering in place. Yet alternative explanations remain open. The snails had been held without food for up to twelve weeks in the laboratory because they refused to feed in captivity, and prolonged starvation is known to dull chemosensory responsiveness in other gastropods. Habituation to a persistent cue, or an unmeasured drift in cue concentration as the static head tanks slowly drained over the long overnight trials, could also account for the fading response. What the data do show unambiguously is that snails spent significantly more time away from the P. argus cue than in direct contact with it.

Perhaps the most counterintuitive finding concerned the lobsters themselves. The spotted spiny lobster, Panulirus guttatus, is a reef obligate, present on the reef day and night, while P. argus migrates between reef and seagrass habitats. The team had expected the ever-present reef resident to elicit the stronger response. The opposite occurred: neither snails nor fireworms showed significant avoidance of P. guttatus cues. The authors offer several non-mutually-exclusive explanations. The two species may differ in the composition, concentration, or release frequency of the chemical cues in their urine. Predator labelling — in which a predator’s recent diet is written into its chemical signature, allowing prey to distinguish individuals that have recently eaten their own kind — could make P. argus, if it eats more molluscs and polychaetes, smell distinctly more dangerous. Alternatively, prey may have habituated to the near-constant odor of a resident species, treating it as background noise, while the episodic arrival of a migratory forager is a more reliable signal of imminent threat. Comparable patterns have been documented in mud crabs, which hide more strongly from cues of wide-ranging hunting blue crabs than from stationary ambush predators.

The broader ecological implication is that lobster presence could suppress coral tissue loss without a single act of predation. If the behavioral avoidance observed in the lab is sustained under field conditions, individual-level avoidance could scale to population- and community-level reductions in corallivory in areas of high lobster abundance. This matters against the backdrop of Caribbean-wide lobster overfishing: regional landings have fallen by roughly 20 percent, and fishing mortality in some areas has reached as high as 98 percent, raising the possibility that depleted predator populations have quietly amplified corallivory on already stressed reefs. Rebuilding lobster stocks through fisheries management and marine protected areas, the authors suggest, may help reverse corallivore-driven feedbacks that accelerate reef degradation, and restoration sites chosen for high lobster densities — or structures designed to enhance lobster habitat — could harness natural predator–prey dynamics to protect outplanted corals.

The team is careful to state the limits of the study. It measured avoidance behavior, not corallivory itself; demonstrating that lobster cues actually reduce coral tissue loss will require directly measuring feeding rates or coral survival under cue exposure, ideally in field or mesocosm settings that incorporate natural hydrodynamics and multi-predator landscapes. Cue strengths were not matched between lobster species, and lobster biomass was not a significant predictor of response in exploratory screening, but direct species-to-species comparisons of cue intensity should still be made cautiously. Identifying the specific metabolites involved, testing for context dependence, and examining how environmental stressors modulate these responses are priorities for future work. Even so, the study documents something genuinely new on coral reefs: a risk-induced pathway linking an invertebrate predator, invertebrate corallivores, and the corals caught in between. In an era when reef managers can control few of the global stressors bearing down on corals, a fear-based mechanism that could be protected, restored, or even engineered into restoration planning stands out as one of the more hopeful findings to emerge from the ecology of fear.

The study also situates itself within a broader theoretical framework known as non-consumptive predator effects, sometimes called the ecology of fear. Decades of research have shown that prey responses to perceived risk — altered foraging, shifts in habitat use, reduced movement — can propagate through food webs and indirectly benefit species at lower trophic levels. On reefs, however, most documented risk effects involve fish prey and mobile predators; evidence for chemically mediated fear responses among benthic invertebrates has remained sparse, making this experiment a notable addition.

The choice of study species reflects practical restoration concerns in the Florida Keys, where both snails and fireworms are documented pests of outplanted Acropora corals. Prior work had shown that adding the predatory rock snail Thais deltoidea to outplanting sites reduced tissue loss, but the mechanism was inferred rather than measured. The lobster study strengthens this line of inquiry by isolating chemical cues alone, demonstrating that predator odor by itself is sufficient to alter corallivore behavior.

Methodological details also matter for interpreting the findings. Trials ran overnight under infrared illumination to accommodate the nocturnal habits of all three species, and control trials with identical seawater on both sides confirmed no chamber bias. Because lobsters were incubated in static head tanks, cue concentration may have drifted over long trials — a limitation the authors acknowledge when weighing the snails’ fading response against genuine sheltering behavior.

Subject of Research: Non-consumptive effects of spiny lobster chemical cues on the avoidance behavior of Caribbean corallivorous invertebrates

Article Title: Spiny lobsters elicit avoidance behaviors in corallivorous invertebrates

Article References: Butler, C. B., Springbett, C. M., & Harborne, A. R. (2026). Spiny lobsters elicit avoidance behaviors in corallivorous invertebrates. Coral Reefs. https://doi.org/10.1007/s00338-026-02963-3

Image Credits: AI Generated

DOI: 10.1007/s00338-026-02963-3

Keywords: spiny lobster, corallivory, coral reefs, non-consumptive effects, chemical cues, predator-prey interactions, Panulirus argus, Hermodice carunculata, Coralliophila galea, coral restoration, behavioral ecology, Caribbean marine ecosystems

Organohalides, organic compounds containing halogen atoms such as chlorine, bromine, or iodine, have long been recognized for their dual nature: some are synthetic pollutants with detrimental environmental effects, while others are naturally occurring molecules integral to marine ecology. The delicate balance between their formation and degradation—a cycle mediated by microbial agents—remains one of the least understood facets of ocean chemistry. This new study unravels the mechanisms governing this microbial halogenation-dehalogenation cycle, elucidating how ocean-dwelling microbes manipulate these compounds, which subsequently influence the marine and atmospheric chemical landscapes.

At the heart of this intricate cycle are specialized halogenating and dehalogenating microorganisms, whose metabolic activities either introduce halogen atoms into organic molecules or remove them, respectively. Zhou and colleagues utilized advanced genomic and metagenomic analyses combined with in situ chemical assays to isolate and characterize microbial communities across different oceanic zones. Their approach allowed for the identification of specific genes and enzymatic pathways responsible for these transformations, offering a molecular-level understanding of how these microbes orchestrate this essential cycling.

One of the remarkable findings from this research is the identification of novel halogenase enzymes that exhibit a remarkable diversity and versatility in catalyzing halogen addition. These enzymes, which catalyze the incorporation of halogen atoms into organic substrates, are not restricted to previously known classes but encompass new families with distinct structural and functional features. Through detailed biochemical characterization, the authors revealed how these enzymes operate under variable environmental conditions, highlighting microbial adaptability in diverse marine niches.

Equally intriguing is the elucidation of microbial dehalogenation processes, responsible for the breakdown and detoxification of organohalide compounds. These processes are fundamental in mitigating the persistence of potentially harmful halogenated substances in marine environments. The study uncovered new reductive dehalogenase enzymes that drive these reactions, offering insights into the microbial strategies employed to exploit organohalides as electron acceptors in energy metabolism.

The consequences of microbial-driven halogen cycling extend beyond ocean chemistry, impacting atmospheric interactions and potentially influencing climate regulation. Organohalides released into seawater can volatilize, entering the atmosphere where they contribute to ozone depletion and greenhouse gas dynamics. By deciphering the microbial balance between organohalide synthesis and degradation, the research informs predictive models about how microbial ecology can modulate these emissions, with implications for global environmental health.

Zhou et al.’s work also uncovers the environmental factors shaping the distribution and activity of halogenating and dehalogenating microbes. Variables such as nutrient availability, oxygen gradients, and temperature were shown to influence microbial community structure and the functional expression of halogen-cycling enzymes. These findings suggest that shifts in oceanic conditions driven by climate change could alter microbial halogen chemistry, with far-reaching effects on marine ecosystems and atmospheric chemistry.

From a methodological perspective, the integration of high-throughput sequencing technologies with geochemical measurements sets a new standard for marine microbial ecology research. The use of metagenome-assembled genomes (MAGs) allowed the researchers to construct comprehensive profiles of microbial taxa and their functional repertoires, overcoming the challenges posed by the vast uncultured microbial majority in the oceans. Combined with isotopic tracing and chemical speciation analyses, this multidimensional approach provided unprecedented resolution into organohalide cycling.

Moreover, the study underscores the importance of microbially-mediated biogeochemical processes in regulating the fate of natural and anthropogenic organohalides. Given the widespread use of halogenated compounds in industrial applications and their persistence as pollutants, understanding microbial degradation pathways is crucial for bioremediation efforts. The newfound enzymatic mechanisms highlighted by the authors could inspire bioengineering strategies aimed at enhancing the breakdown of harmful organohalides in marine and terrestrial environments.

The interplay between marine microbes and organohalides also unfolds in the context of ecological interactions within microbial communities. For example, the production of halogenated compounds can serve as chemical signals or defense molecules, influencing microbial competition and cooperation. This ecological dimension adds complexity to the cycling process and points to a broader role of organohalides in structuring marine microbial ecosystems, beyond their chemical reactivity.

Importantly, the research provides a blueprint for future studies that can explore the temporal dynamics of halogen cycling across seasonal and spatial gradients. Longitudinal sampling campaigns, combined with real-time monitoring of microbial activity, could reveal how episodic events like phytoplankton blooms or oceanic deoxygenation influence organohalide transformations. Such efforts will be essential to predict how ongoing environmental change will shape these critical microbial processes.

Zhou and colleagues emphasize the need to incorporate microbial halogen chemistry explicitly into global ocean models to enhance their accuracy and predictive power. Traditional models often overlook microbial contributions or simplify halogen cycling, ignoring the nuance revealed by contemporary molecular insights. Incorporating this detailed mechanistic knowledge will provide a more holistic understanding of marine biogeochemical cycles and their feedbacks to the Earth system.

In addition to environmental implications, this research opens avenues for biotechnological exploitation of halogenating and dehalogenating enzymes. The unique catalytic properties of these enzymes could be harnessed for biocatalysis in pharmaceutical synthesis, where selective halogenation is often a challenging synthetic step. Likewise, engineered microbial consortia based on these natural processes could be developed for targeted pollutant removal or chemical production in marine biotechnology sectors.

The study also highlights the significance of interdisciplinary collaborations, blending microbiology, chemistry, oceanography, and bioinformatics to decode complex environmental phenomena. This integrated research paradigm exemplifies how converging cutting-edge techniques uncovers critical insights into Earth’s fundamental processes and offers pathways to address pressing environmental challenges.

Perhaps most strikingly, the research presents a compelling narrative about the unseen majority of life in the oceans — microbes — and their profound influence on planetary health. By mediating the cycling of compounds that intertwine with atmospheric chemistry, climate, and pollution, these microscopic actors underscore the intricate connectivity of Earth’s biosphere. Zhou et al.’s findings serve as a powerful reminder that deciphering microbial networks is essential to understanding and protecting our planet.

In sum, this pioneering study reshapes our perspective on marine organohalide chemistry, presenting a sophisticated picture of microbially-driven halogenation and dehalogenation as central to oceanic biogeochemical fluxes. Its insights bear relevance across environmental science, biotechnology, and climate research domains. As ongoing investigations build on this foundational work, a more complete understanding of microbial halogen cycling promises to unlock innovative solutions to environmental stewardship and sustainable resource utilization in the ocean.

Subject of Research: Microbial mediation of halogenation and dehalogenation of organohalides in the marine environment.

Article Title: Microbially-mediated halogenation and dehalogenation cycling of organohalides in the ocean.

Article References:
Zhou, N., Li, Q., Liang, Z. et al. Microbially-mediated halogenation and dehalogenation cycling of organohalides in the ocean. Nat Commun 16, 10670 (2025). https://doi.org/10.1038/s41467-025-65696-x

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41467-025-65696-x