Search Results (198)

Algae-based carbon dioxide removal (CDR) systems are increasingly recognized as versatile climate solutions that combine rapid biological uptake with multiple pathways for durable sequestration. Macroalgae and microalgae offer comparative efficiencies that exceed many terrestrial options, while simultaneously contributing to food security, bioeconomic innovation, and ocean stewardship. Yet significant challenges remain in ensuring permanence, developing robust remote monitoring, reporting, and verification (RMRV) frameworks, and integrating algae into carbon markets and policy regimes. Societal acceptance and ethical considerations, including equity, cultural heritage, and governance transparency, will be critical to legitimacy and scale. Future research must advance biological and technological innovation, refine sequestration pathways, and embed social sciences into deployment strategies. Taken together, algae-based systems represent a promising but complex component of the global portfolio of climate mitigation, requiring interdisciplinary collaboration to unlock their full potential and ensure that climate benefits are coupled with broader societal gains. Full article

Several shale oil intervals, including those in offshore China, were deposited in paralic lacustrine basins that experienced marine incursions. Marine incursions could be either favorable or unfavorable for the accumulation of organic matter (OM) and shale oil. However, the influence and specific mechanisms of seawater on OM accumulation require further in-depth investigation. During the deposition of the Triassic Chang 7 Member in the Ordos Basin, seawater from the Paleo-Tethys Ocean intruded into the basin. Taking this interval as a case study, this paper employs comprehensive analyses to reveal the influence of marine incursion on water column conditions and OM accumulation. Under humid climatic conditions, the water body was fresh to brackish, characterized by high productivity and oxic–dysoxic conditions. The OM is primarily derived from algae, and its accumulation was jointly controlled by primary productivity, redox conditions, and terrigenous input. OM accumulation is controlled by fluctuations in the relative water level (RWL) associated with third-order sequences. During the period of high RWL, seawater incursions enhanced water column productivity and reduced conditions by increasing nutrient supply and salinity, resulting in the highest OM content. During the early and late periods of the RWL, as seawater receded, OM production declined while consumption and dilution increased, resulting in a gradual decrease in its content. The RWL fluctuations at the fourth-order scale also significantly influence OM accumulation. These results can enhance the understanding of OM accumulation in paralic lacustrine basins with a history of seawater incursion. While promoting shale oil exploration in the Ordos Basin, they can also serve as a research analog for shale oil exploration in basins with similar geological backgrounds, such as the Bohai Bay Basin. Full article

The Mediterranean Sea is a biodiversity and climate change hotspot. The increase in seawater temperature affects marine ecosystems causing marine species to change their distribution and abundance. Such changes lead to alterations in community composition, often characterized by an increase in warm-affinity species over time, known as tropicalization of temperate seas. Monitoring programmes are useful for understanding the consequences of the ongoing transformations driven by ocean warming. In this study, underwater visual censuses (UVC) were conducted for fish and benthic communities at 24 stations of the Balearic Archipelago in 2022 and 2025. The comparison between both periods revealed an increase in the frequency of warm-affinity species, including the fishes Sparisoma cretense (Teleostea, Scaridae) and Caranx crysos (Teleostea, Carangidae); the invertebrates Telmatactis cricoides (Cnidaria, Actiniaria) and Hermodice carunculata (Annelida, Polychaeta, Amphinomidae) and the algae Penicillus capitatus (Chlorophyta, Ulvophyceae). Our findings highlight the importance of monitoring programmes to identify evidence of processes such as tropicalization and to provide timely information to respond to shifting marine ecosystems. Full article

Eukaryotic algae are key contributors to biodiversity and ecosystem functioning in aquatic environments. However, understanding their global diversity patterns and community assembly mechanisms remains limited by the lack of high-resolution, highly specific analytical methods. Here, we present the first eukaryotic algae-specific classification database, EukAlgae-T (Eukaryotic Algae Taxonomic database), constructed based on single-copy orthologous genes. The database integrates 50,581 non-redundant marker genes from 479 high-quality genomes and was applied to analyze 939 marine metagenomic samples from the Tara Oceans project. Our results reveal that the genomically represented fraction of the global algal community is dominated by a widely distributed core taxonomic group, comprising 125 of the 230 detected species. Redundancy analysis indicated that community structure is primarily regulated by latitude and iron concentration on a global scale. In contrast, Mantel tests revealed strong regional heterogeneity, with temperature, salinity, and iron concentration acting as universal local drivers, albeit with varying effect sizes and combinations across ocean basins. Co-occurrence network analysis further demonstrated predominantly cooperative interactions among taxa, forming a highly modular and stable network structure, and identified key hub taxa characterized by low abundance but high connectivity. Together, this study provides a dedicated framework for eukaryotic algae metagenomic analysis and demonstrates that algal community assembly is driven by multi-scale environmental filtering: broadly constrained by climate zones and iron limitation at the global scale and regionally reshaped by local oceanographic processes (e.g., thermohaline structure). Cooperative coexistence and niche differentiation among taxa jointly underpin the maintenance of global algal diversity. Full article

Macroalgae are essential components of marine ecosystems, supporting biodiversity, primary productivity, and the functioning of coastal habitats. In the northeast Atlantic Macaronesian archipelagos (Azores, Madeira, Selvagens, Canary Islands, Cabo Verde), they hold significant ecological and economic value and have recently emerged as key indicators of environmental change. This oceanic region faces increasing pressure from multiple stressors, including climate change, invasive species, habitat degradation, and other anthropogenic impacts, driving shifts in coastal ecosystems and the simplification of structurally complex habitats such as marine forests. To assess the current state of knowledge on Macaronesian macroalgae and identify gaps relevant to conservation and management, we conducted a systematic literature review following PRISMA guidelines. Our results show strong but uneven foundational knowledge, with the Azores and Canary Islands accounting for roughly 80% of publications. Research is dominated by fundamental studies in ecology and taxonomy, while applied research (e.g., resource exploitation, aquaculture, toxicology, and climate-change impacts) remains limited. Red algae and a few dominant orders (Ceramiales, Fucales, Dictyotales) are well represented, whereas green algae and less conspicuous taxa are understudied. Future research should expand geographic coverage, broaden taxonomic scope using molecular tools, strengthen applied research, standardize monitoring frameworks, and align scientific output with management needs. Full article

Rhodoliths (from Greek etymology meaning red + stone) are spheroidal accretions composed of various types of crustose coralline red algae that dwell in relatively shallow waters where sunlight allows for photosynthesis. Unlike most other kinds of algae that are attached to the seabed by a holdfast, rhodoliths are free to roll about by circumrotary movements stimulated mainly by gentle wave action and bottom currents, as well as by disruptions by associated fauna. Frequent movement exposes every part of the algal surface to an equitable amount of sunlight, which generally results in an evenly concentric pattern of growth over time. Individual structures may attain a diameter of 10 to 20 cm, representing 100 years of growth or more. Initiation typically involves encrustation by founder cells on a rock pebble or shell fragment. In life, the functional outer surface is red or pink in complexion, whereas the structure’s inner core amounts to dead weight. Chemically, rhodoliths are composed of high magnesium calcite [(Ca,Mg)CO₃], with examples known around many oceanic islands and virtually all continental shelves in the present world. The oldest fossil rhodoliths appeared during the early Cretaceous, 113 million years ago. Geologically, rhodoliths may occur in massive limestone beds composed of densely packed accumulations. Living rhodoliths commonly occur in waters as shallow as −2 to −10 m, as well as seaward in mesophotic waters up to −100 m under exceptional conditions of water clarity. Especially in shallower waters, rhodoliths are vulnerable to transfer by storm waves to supratidal settings, which result in bleaching under direct sunlight and death. Increasingly, marine biologists recognize that rhodolith beds represent a habitat that offers shelter to a community of other algae and diverse marine invertebrates. Full article

Citizen science approaches for monitoring, and even restoring, coral reefs have grown in popularity though tend to be restricted to those who have taken courses that expose them to the relevant methodologies. Now that cheap (~10 USD), waterproof pouches for smart phones are widely available, there is the potential for mass acquisition of coral reef images by non-scientists. Furthermore, with the emergence of better machine-learning-based image classification approaches, high-quality data can be extracted from low-resolution images (provided that key benthic organisms, namely corals, other invertebrates, & algae, can be distinguished). To determine whether informally captured images could yield comparable ecological data to point-intercept + photo-quadrat surveys conducted by highly proficient research divers, we trained an artificial intelligence (AI), CoralNet, with images taken before and during a bleaching event in 2015 in Chagos (Indian Ocean). The overall percent coral covers of the formal, “gold standard” method and the informal, “tourist diver” approach of 38.7 and 35.1%, respectively, were within ~10% of one another; coral bleaching percentages of 30.5 and 31.8%, respectively, were statistically comparable. Although the AI was prone to classifying bleached corals as healthy in ~one-third of cases, the fact that these data could be collected by someone with no knowledge of coral reef ecology might justify this approach in areas where divers or snorkelers have access to waterproof cameras and are keen to document coral reef condition. Full article

Hydrogen energy, with its high calorific value and zero carbon emissions, serves as a crucial solution for addressing global energy and environmental challenges while achieving carbon neutrality. The ocean offers abundant renewable energy resources including offshore wind, solar, and marine energy, along with vast seawater reserves, making it an ideal platform for green hydrogen production. This review systematically examines recent research progress in several key marine hydrogen production approaches: seawater electrolysis through both desalination-coupled and direct methods, photocatalytic seawater splitting, biological hydrogen production via algae and bacteria, and hybrid renewable energy systems, each demonstrating varying levels of technological development and industrial readiness. Despite significant advancements, challenges remain, such as reduced electrolysis efficiency caused by seawater impurities, high costs of catalysts and corrosion-resistant materials, and the intermittent nature of renewable energy sources. Future improvements require innovations in catalyst design, membrane technology, and system integration to enhance efficiency, durability, and economic feasibility. The review concludes by outlining the technological development directions for marine hydrogen energy, highlighting how hydrogen production from marine renewable energy can facilitate a sustainable blue economy through large-scale renewable energy storage and utilization. Full article

Chlorophyll fluorescence provides direct insights into the physiological status of algae, contributing to the understanding of the marine carbon cycle. However, in situ measurements of phytoplankton photosynthetic physiology remain relatively scarce in the Yangtze River Estuary (YRE), an ecosystem under intense anthropogenic pressure. Consequently, quantifying composition and physiological status variations of phytoplankton in this region is critical for understanding their ecological functions and responses. Spring cruise revealed that the warm and high-salinity oceanic region exhibited a greater abundance of dinoflagellates and chrysophytes, while the lower-salinity plume region was characterized by higher abundances of chlorophytes and cryptophytes. Diatoms dominated across all regions. The highest chlorophyll a concentration (6.3 μg/L) was observed in the oceanic region. Chlorophyll fluorescence indicated that the warm offshore community was more active, suggesting favorable phytoplankton growth. As temperature decreased and seawater mixed, the maximum relative electron transport rate (rETRmax) and the minimal saturated light intensity (I_k) decreased, yet the overall community remained healthy. Despite the plume delivering abundant nutrients, phytoplankton activity was relatively low due to the cold spring water temperature. This study will provide a foundation for understanding phytoplankton dynamics under anthropogenic influences in the YRE and the adjacent East China Sea, supporting algal bloom monitoring and early warning efforts. Full article

Human-sourced emissions of carbon dioxide (CO₂) into the Earth’s atmosphere have been implicated in contemporary global warming, based mainly on computer modeling. Growing empirical evidence reviewed here supports the alternative hypothesis that global climate change is governed primarily by a natural climate cycle, the Antarctic Oscillation. This powerful pressure-wind-temperature cycle is energized in the Southern Ocean and teleconnects worldwide to cause global multidecadal warm periods like the present, each followed historically by a multidecadal cold period, which now appears imminent. The Antarctic Oscillation is modulated on a thousand-year schedule to create longer climate cycles, including the Medieval Warm Period and Little Ice Age, which are coupled with the rise and fall, respectively, of human civilizations. Future projection of these ancient climate rhythms enables long-term empirical climate forecasting. Although human-sourced CO₂ emissions play little role in climate change, they pose an existential threat to global biodiversity. Past mass extinctions were caused by natural CO₂ surges that acidified the ocean, killed oxygen-producing plankton, and induced global suffocation. Current human-sourced CO₂ emissions are comparable in volume but hundreds of thousands of times faster. Diverse evidence suggests that the consequent ocean acidification is destroying contemporary marine phytoplankton, corals, and calcifying algae. The resulting global oxygen deprivation could smother higher life forms, including people, by 2100 unless net human-induced CO₂ emissions into the atmosphere are ended urgently. Full article

We adapt previous conceptual and numerical models of ciguateric food chains for the bioaccumulation of Pacific-ciguatoxin-1 (P-CTX-1) to a general model for bioaccumulation of P-CTX3C by parrotfish (Scarus frenatus, S. niger, and S. psittacus) that feed by scraping turf algae, and surgeonfish (Naso unicornis) that mostly feed on macroalgae. We also include the Indian Ocean parrotfish Chlorurus sordidus as a model for an excavator feeding parrotfish and include comparisons with the detritivorous surgeonfish Ctenochaetus striatus that brush-feeds on turf algae. Our food chain model suggests that, of the Gambierdiscus and Fukuyoa species so far analysed for ciguatoxin (CTX) production from the Pacific, only G. polynesiensis produces sufficient P-CTX3C to consistently produce parrotfish or N. unicornis with poisonous flesh. Our model suggests that insufficient CTX would accumulate into the flesh of parrotfish or N. unicornis to become poisonous from ingesting benthic dinoflagellates producing ≤0.03 pg P-CTX3C eq./cell, except from extended feeding times on high-density blooms and in the absence of significant depuration of CTX. Apart from G. polynesiensis, only G. belizeanus and possibly G. silvae and G. australes are thought to produce >0.03 pg P-CTX3C eq./cell in the Pacific. However, with relatively low maximum concentrations of ≤0.1 pg P-CTX3C eq./cell it is likely that their contribution is minimal. Our model also suggests that the differences between the area of turf algae grazed by parrotfish and similar sized C. striatus results in greater accumulation of CTX by this surgeonfish. This makes C. striatus a higher ciguatera risk than similar sized parrotfish, either directly for human consumption or as prey for higher trophic level fishes, consistent with poisoning data from Polynesia. It also suggests the possibility that C. striatus could bioaccumulate sufficient CTX to become mildly poisonous from feeding on lower toxicity Gambierdiscus or Fukuyoa species known to produce ≥0.02 P-CTX3C eq./cell. This indicates the potential for at least two food chain pathways to produce ciguateric herbivorous fishes, depending on the CTX concentrations produced by resident Gambierdiscus or Fukuyoa on a reef and the grazing capacity of herbivorous fish. However, only G. polynesiensis appears to produce sufficient P-CTX3C to consistently accumulate in food chains to produce higher trophic level fishes that cause ciguatera in the Pacific. We incorporate CTX depuration into our model to explore scenarios where mildly poisonous parrotfish or N. unicornis ingest CTX at a rate that is balanced by depuration to estimate the Gambierdiscus/Fukuyoa densities and CTX concentrations required for these fish to remain poisonous on a reef. Full article

Rhodoliths are calcareous red algae considered indicators of ocean acidification and key biodiversity hotspots due to their ability to host a variety of species within their three-dimensional structures. This work aims to review the available scientific literature on rhodolith-forming species: reports from literature, the Symbiota digital taxonomic inventory, field observations, and nucleotide databases. A total of 21 species is reported, predominantly from the Corallinaceae family and the Lithophylloideae subfamily. Rhodoliths have been reported in Bocas del Toro, the Gulf of Chiriqui, Coiba National Park (PNC), the Gulf of Panama, and at the Las Perlas Archipelago. This review represents the first step in raising awareness about the presence of these organisms along Panama’s coast and advocating for their inclusion in the management plans of protected areas, such as PNC, a UNESCO World Heritage Site, where rhodoliths are not yet part of the recorded algae species list or the park’s conservation targets, despite their ecological relevance. Knowledge remains limited, and their conservation status is uncertain, but the increasing sampling efforts and integration of morphological and molecular studies will open new opportunities to improve the estimation of rhodolith diversity in Panama. Full article

Earth hosts a remarkable diversity of life, with oceans covering over 70% of its surface and supporting the greatest abundance and variety of species, including a vast range of seaweeds. Among these, red seaweeds (Rhodophyta) represent the most diverse group and are particularly rich in bioactive compounds. Grateloupia turuturu Yamada and Porphyra umbilicalis Kütz. are two species with significant biotechnological and functional food potential. They contain high levels of phycobiliproteins, sulfated polysaccharides (e.g., carrageenan, agar, porphyran), mycosporine-like amino acids (MAAs), phenols, minerals, and vitamins, including vitamin B12 (rare among non-animal sources). Several analytical methods, such as spectrophotometry, chromatography, and mass spectrometry, have been used to characterize their chemical composition. In vitro and in vivo studies have demonstrated their antioxidant, anti-inflammatory, neuroprotective, immunostimulatory, anti-proliferative, and photoprotective effects. These bioactive properties support its application in the food, pharmaceutical, and cosmetic sectors. Given the growing demand for sustainable resources, these algae species stand out as promising candidates for aquaculture and the development of functional ingredients. Their incorporation into novel food products, such as snacks and fortified dairy and meat products, underscores their potential to support health-promoting diets. This review highlights G. turuturu and P. umbilicalis chemical richness, bioactivities, and applications, reinforcing their value as sustainable marine resources. Full article

Alginate, a major polysaccharide in brown algae, is vital for the carbon cycling of the ocean ecosystem and holds promise for biotechnological applications. Marine Bacteroidetes, known for the ability to degrade complex polysaccharides, play an important role in the ocean carbon cycle; however, the detailed alginate degradation pattern remains to be further explored. In this study, an alginate utilization locus was identified in the genome of a new marine Bacteroidetes, Roseihalotalea indica gen. nov. sp. nov. TK19036^T, and encodes two new alginate lyases, RiAlyPL6 and RiAlyPL17, which play potential roles in the degradation and utilization of alginate. RiAlyPL6 and RiAlyPL17 have distinct degradation products and substrate preferences, revealing the adaptation of the strain to utilize alginate with different M/G ratios. Based on the results in this paper, we have proposed a model for the degradation and utilization mechanism of alginate in Roseihalotalea indica gen. nov. sp. nov. TK19036^T. All in all, our research provides a new insight into the alginate mechanisms within marine Roseihalotalea, and the two novel alginate lyases are excellent candidates for preparation and application. Full article

Coral reefs are among the most important marine habitats but face significant threats from anthropogenic sources, including climate change. This paper reviews and compares the modern Great Barrier Reef Province and the 360-million-year-old Devonian Great Barrier Reef of western Australia. Despite occurring at times with different climates, biota (both marine and terrestrial), weathering processes and marine chemistry, similar reefs were constructed under certain circumstances. Major differences in global temperature, marine carbonate saturation, sea level behavior and reef community constituents were evaluated. The comparison highlights the integration of, and interdependencies within, reef communities and the need for both carbonate producers and significant binders, whether skeletal or microbial, to construct a reef in a high-energy setting. Devonian communities with abundant corals and skeletal sponges were incapable of making modern reef types without competent binders to unify framework into rigid substrate. The current strong focus on corals and bleaching in modern reef conservation may be obscuring the equally significant issue of ocean acidification, which impacts on equally crucial framework unification, i.e., hard binding by coralline algae and microbialites and early cementation. The comparison also supports the idea that ‘empty bucket’ carbonate platform morphologies require increased accommodation from high-amplitude icehouse sea level oscillations. Full article