Phycology

Conservation units (CUs) play a fundamental role in maintaining and conserving biodiversity, and are important in preserving streams, reducing impacts from human activities and increasing water availability beyond the boundaries of the reserves. However, knowledge about the phytoplankton biodiversity of ecosystems in CUs is scarce. This study evaluated how environmental integrity alters microphytoplankton communities in extractive CUs and their surroundings in the southwestern Brazilian Amazon. Our results demonstrated that the streams exhibited distinct physicochemical and hydrological characteristics, representing spatially heterogeneous environments. Differences in habitat integrity values altered species composition in streams within and outside conservation units. Local beta diversity (LCBD) was negatively influenced by habitat integrity, indicating that sites with greater habitat integrity did not always present a greater number of unique species. The species Trachelomonas hispida, Gyrosigma scalproides and Spirogyra sp. were the ones that contributed the most to beta diversity. However, the phytoplankton species that contributed most to beta diversity were not always associated with streams with greater integrity, indicating that even environments that are less intact play a relevant role in maintaining species richness and beta diversity of microphytoplankton. Factors such as habitat integrity, pH, temperature and dissolved oxygen were the main influencers of microphytoplankton in the streams. Thus, the streams of both CUs and their surroundings, despite their physical–chemical and hydrological differences, effectively contribute to the high richness and beta diversity of regional microphytoplankton. Full article

The nutrient-rich composition of seaweeds and lichens makes them well-suited for agricultural applications. Their use as alternatives to synthetic fertilizers contributes to sustainable agricultural production, enabling farmers to adopt ecological practices while maintaining or increasing crop productivity. This review aims to highlight the status and trends of research, along with a literature analysis on the application of these biomasses in sustainable agriculture. A bibliometric analysis was performed based on two databases (Scopus and Web of Science) to overview the main research topics regarding the use of biomasses studied in agriculture, thus providing useful information for future research. The biochemical composition and agricultural applications of these biomasses have been highlighted. The analysis shows that these biomasses are rich of nutrient compounds, revealing their roles and mechanisms of action on the chemical, nutritional properties, and soil microbial activities and their effect on plant growth, using various extraction and application methods. It also highlighted the potential of seaweeds for protection against biotic and abiotic stresses. In light of all the data presented in this review, it is possible to stimulate farmers’ interest in using seaweeds and lichens as natural fertilizers, with a focus on sustainable and ecological agriculture mainly in developing countries. Full article

Bangiales are photosynthetic organisms that grow in the intertidal zone, a region characterized by fluctuating environmental conditions. The order comprises genera exhibiting two different morphological variations, filamentous and foliose. It was recently demonstrated that the filamentous alga ‘Bangia’ sp. ESS1 possesses the intrinsic ability to “memorize” an experience of prior heat stress to enhance its survival under subsequent, normally lethal, high-temperature conditions via the acquisition of heat stress tolerance. Here, we investigated whether foliose red algae can similarly memorize heat stress to acquire thermotolerance. When Pyropia yezoensis thalli were primed with non-lethal, high-temperature treatments (22 and 25 °C) for 7 days, vegetative cells subsequently triggered with a normally lethal temperature of 30 °C showed dramatically increased survival rates, indicating that P. yezoensis can acquire heat stress tolerance via exposure to non-lethal high temperatures. In addition, when 22 °C-primed thalli were incubated at 15 °C for recovery, vegetative cells survived subsequent incubation at 30 °C; their survival rates varied depending on the duration of recovery. These findings indicate that, like filamentous red algae, the foliose species P. yezoensis memorizes heat stress to acquire tolerance to recurrent thermostress. The identification of heat stress memory in foliose Bangiales lays a foundation for improving the heat stress tolerance of these important algae, supporting the sustainability of the nori mariculture industry. Full article

The Portuguese coast forms a key biogeographic transition zone where co-occurring kelp species show limited vertical overlap. This study aimed to understand whether temperature and light responses help explain the vertical niche differentiation of Laminaria ochroleuca, Saccorhiza polyschides, and Phyllariopsis brevipes. Results revealed that P. brevipes, despite occupying the southernmost range, showed a low thermal tolerance: 27 °C significantly increased respiration rates, indicating metabolic stress, and exposition at 30 °C caused physiological stress. In contrast, L. ochroleuca and S. polyschides exhibited a greater thermal resilience but displayed high light requirements, with evident stress at 30 °C. These results suggest that light availability may play a key role in shaping vertical zonation in a climate warming scenario, with species adapted to low light occupying deeper subtidal zones. S. polyschides, a high light-requiring species, dominates the shallow subtidal region, while L. ochroleuca, also high light-requiring and temperature-tolerant, is abundant in both intertidal pools and shallow subtidal habitats. These findings raise new hypotheses regarding future distribution patterns under climate change: while L. ochroleuca may continue expanding polewards and potentially replace other Laminaria spp. at shallow depths, low-light-adapted, cold-water species may retain a competitive advantage in deeper zones. Full article

Microcystis aeruginosa is a cyanobacterium frequently associated with toxic blooms in eutrophic freshwater systems. Certain strains produce microcystins (MCs), a group of hepatotoxins with significant ecological and public health implications. In this study, we examined the quantitative response of a temperate native M. aeruginosa strain to combinations of temperature (26, 30, and 36 °C), light intensity (30, 50, and 70 µmol photons·m⁻²·s⁻¹), and N:P ratio (10, 100, 150), using a full-factorial experimental design. Growth parameters (µ, lag phase duration, and maximum cell density), chlorophyll-a production, and MC-LR synthesis were modeled using Gompertz, linear, and dynamic approaches. High temperature and irradiance increased the specific growth rate but decreased final biomass, while elevated N:P ratios shortened the lag phase. MC-LR production peaked under low temperature, low irradiance, and low N:P ratio. Although MC-LR synthesis did not correlate positively with growth rate, and the environmental conditions maximizing growth differed from those enhancing toxin production, a population-level coupling between both processes was observed using the Long model. These findings suggest that MC-LR synthesis in M. aeruginosa is not merely a metabolic by-product of growth, but a context-dependent trait with potential adaptive significance. Full article

Seaweeds represent a vital yet often understudied component of the diet and cultural heritage of many coastal communities globally. This study investigated seaweed consumption practices in coastal communities of Tawi-Tawi, Philippines, through one-to-one interviews (n = 280) and focus group discussions (n = 7). The study revealed that nearly all (99%) of the population consumes seaweeds, with women comprising the majority of consumers who have done so since childhood (68% female vs. 32% male). These consumers were predominantly married (79%), within the 21–40 age group (53%), with families of 5–7 members (43%), practicing Islam (97%), and belonging to the Sama tribe (71%). A significant portion (48%) had resided in the area for 21–30 years, attained elementary to high school education (66%), and had a monthly income ranging from 1000 to 10,000 Philippine pesos (72%). Seaweed consumption was a family-wide practice (88%), including children, who typically started around 4–8 years old (61%), driven by perceived nutritional benefits (43%), preferred flavor (80%), affordability (19%), ease of preparation (33%), and cultural integration (23%). The primary edible seaweeds identified were Kappaphycus alvarezii (63%), K. striatus (58%), Kappaphycus spp. (47%), Eucheuma denticulatum (57%), Caulerpa lentillifera (64%), Caulerpa spp. (51%), C. cf. macrodisca ecad corynephora (45%), C. racemosa (30%), and Solieria robusta (49%), with less frequent consumption of K. malesianus (8%), Chaetomorpha crassa (3%), Gracilaria spp. (0.72%), and Hydroclathrus clathratus (0.36%). Specific plant parts were preferred for certain species, and preparation predominantly involved raw (75%) or cooked (77%) salads with spices, primarily prepared by mothers (72%). Consumers generally avoided seaweeds showing signs of ice-ice disease (95%), pale coloration (91%), or epiphyte infestation (84%). Consumption frequency was typically 1–3 times per week (45%), with knowledge largely passed down through generations (95%). Seaweed salads were primarily consumed as a viand (92%) at home (97%), with locals perceiving seaweed consumption as contributing to a healthy diet (40%) and overall well-being [e.g., aiding hunger (76%), improving digestion (20%), preventing obesity (14%), and aiding brain development (3%)]. The study’s findings emphasize the significant yet often overlooked role of seaweeds in the food systems and cultural heritage of Tawi-Tawi’s coastal communities. Future efforts should prioritize the sustainable management of wild resources, explore the cultivation of diverse edible species, and enhance nutritional awareness. Further research into traditional seaweed knowledge holds broader value. Full article

The microalgal defense strategies for different white light intensities (70–700 μmol m⁻² s⁻¹) were investigated in isolates from unexplored habitats, focusing on photosynthetic performance. Chlorella sorokiniana strain F4 from a Mediterranean inland swamp and two strains related to Pectinodesmus pectinatus (PEC) and Ettlia pseudoalveolaris (ETI) from an Ecuadorian highland lake were exposed to light over 18 h. The results showed that PSII photochemical efficiency was affected with increasing light due to photoinhibition or photodamage. F4 showed a low threshold of saturation light intensity, after which NPQ was compromised and total antioxidant levels were increased, leading to a reduction in its PSII photochemistry performance. F4 exhibited limited capacity for antennae reorganization in response to light stress. ETI and PEC differed in their photophysiological responses, although they came from the same habitat. ETI maintained high Chlb to Chla (i.e., large antennae), exhibited sustained energy dissipation, and preserved a high antioxidant pool (i.e., mycosporine-like amino acids) in all lights. Differently, in PEC, NPQ, antennae rearrangement, and reactive oxygen species scavenger pool were induced in a light-dependent manner. This study revealed the complex relationship between light parameters and microalgal physiology affected by environmental constraint adaptation and phylogenetic diversity. Full article

This study examines the influence of light wavelengths on the growth dynamics of five algal genera (Chlorella sp., Volvox sp., Gloeocapsa sp., Microspora sp., and Mougeotia sp.) in freshwater systems, using machine learning to optimize growth models. Natural light yielded the highest algal proliferation, increasing the total count from 90 to 1390 cells/mL in 30 days. Filtered wavelengths showed that blue light most effective (840 cells/mL), followed by red (490 cells/mL) and yellow (200 cells/mL), while green light minimally impacted growth (160 cells/mL). Genera-specific responses revealed that Gloeocapsa sp. and Mougeotia sp. thrived the most under blue light (240 and 750 cells/mL, respectively), with red and blue wavelengths generally enhancing growth across genera. Machine learning models achieved high accuracy (R² > 0.96 for total growth and R² > 0.8 for genera-specific and wavelength-based models), refining growth kinetics. These results suggest that spectral manipulation limiting blue/red wavelengths in water treatment to curb blooms while leveraging natural light for biofuel cultivation could optimize algal management. The integration of empirical data with machine learning offers a robust framework for predictive modeling in algal research and industrial applications. Full article

Macroalgal extracts are widely recognised as biostimulants that enhance crop productivity and plant growth under both optimal and stressful conditions. They offer a sustainable approach to mitigating the adverse effects of abiotic stress on crop development. This study investigates the efficacy of macroalgal-based fertilisers in enhancing tomato (Solanum lycopersicum L.) growth, yield, and fruit quality, as sustainable alternatives to chemical fertilisers. Different seaweed species (Sargassum muticum, Ulva ohnoi, Furcellaria lumbricalis, Ascophyllum nodosum, and a commercial A. nodosum extract) were evaluated as foliar treatments. The results showed that while the leaf fresh weight and chlorophyll content were not significantly affected, the fruit morphology and biochemical composition exhibited notable variations. Sargassum muticum-treated fruits displayed the highest °Brix (6.57), indicating superior sugar accumulation, while Ulva ohnoi maintained near-neutral pH levels (avg. 3.94), suggesting balanced acidity. Ascophyllum nodosum extracts induced the highest proline concentrations (peak: 63.77 µmol/g), but also caused extreme acidity (pH 1.39–2.58). Furcellaria lumbricalis enhanced the fruit size (axial length up to 41.4 mm), but reduced the pH sharply (1.69–2.13). The commercial product underperformed in regard to sugar content and flavour complexity. The integrative analysis revealed species-specific flavour profiles: Sargassum yielded sweet, mildly acidic fruits; Ascophyllum produced intensely aromatic, acidic tomatoes; and Ulva resulted in bland flavours. These findings underscore the importance of algal species and extraction methods in tailoring biofertilisers for target fruit qualities. This study advocates for the use of macroalgal fertilisers in sustainable agriculture, but highlights the need for optimised formulations to balance crop yield, taste, and stress adaptation. Full article

Microalgae are photosynthetic organisms with rapid growth and high biochemical diversity, capable of thriving in a variety of environments. Among them, dinoflagellates, particularly symbiotic species like Durusdinium glynnii, have gained attention due to their potential for biotechnological applications, especially in the production of valuable fatty acids. However, the delicate cultivation of dinoflagellates remains a challenge due to their sensitivity to shear stress and complex morphology. In this study, we evaluated the influence of inoculum percentage (10%, 25%, and 50%) on the growth performance and fatty acid profile of D. glynnii during a scale-up process from test tubes to a pilot-scale photobioreactor. Higher inoculum concentrations (50%) promoted faster acclimatization, higher specific growth rates (µ_max), and greater final biomass densities, optimizing the cultivation process. Meanwhile, lower inoculum concentrations (10%) favored the accumulation of polyunsaturated fatty acids, particularly DHA (C22:6n3), indicating a trade-off between biomass productivity and fatty acid biosynthesis. Overall, D. glynnii demonstrated robust adaptability, reinforcing its potential as a sustainable source of bioactive compounds. Further studies focusing on cellular and metabolic pathways are needed to better elucidate the mechanisms underlying lipid production and growth in this promising species. Full article

In most cases, the sizes of the daughter cells of diatoms follow the MacDonald–Pfitzer rule, whereby in many species all diatoms divide once in each generation. In contrast, there are division schemes in which the smaller or larger daughter cell is delayed in its division by one generation and therefore leads to Fibonacci growth. Several properties of diatoms, especially in chain-like colonies, that exhibit such delayed division can be modeled by Lindenmayer systems. These include, above all, the size and orientation of the diatoms. Certain sequences of properties, such as the differences in size indices of neighboring diatoms, are aperiodic and represent self-similar fractal structures. For the division schemes studied, explicit solutions can be found for the number of diatoms of a certain size in each generation. For the experimental differentiation of the division schemes in a diatom chain, in addition to the observation of the division processes over several generations, methods are available that only require the analysis of the structure of a sufficiently large sample. This includes the investigation of the differences in the sizes of neighboring diatoms, the orientations of the diatoms and the frequencies of size indices in a culture. These methods provide a toolbox for investigating diatom properties, applicable to the division models described. Additionally, a mathematical framework is presented that has the potential to be transferable to other properties and other division schemes. Full article

The growing demand for the sustainable production of high-value compounds, such as biofuels, lipids, and pigments like carotenoids and phycobilin, has become the subject of numerous investigations. Furthermore, this has led to the exploration of renewable methods utilizing microalgae as feedstock to mitigate the challenges associated with producing these valuable compounds. Nevertheless, despite the numerous advantages of microalgae, the development of a microalgal biorefinery that employs sustainable, environmentally friendly, and economically efficient technologies remains a necessity. To address this challenge, the bio-flocculation process, and more specifically self-flocculation, is presented as a cost-effective and energy-efficient solution. This method is as easy and effective as chemical flocculation, which is applied at an industrial scale; however, in contrast, it is sustainable and cost-effective as no costs are involved in the pre-treatment of the biomass for oil extraction or in the pre-treatment of the medium before it can be re-used. In addition, microalgae possess molecular tools that would allow the efficiency of these processes to be increased. In the present review, we summarize the microalgal harvesting technologies used, with a particular focus on bio- and self-flocculation processes, and identify the improvements that could be made to enhance the production of high-added-value compounds while simultaneously reducing costs in microalgae biorefineries. Full article

The separation of microalgae from a culture medium is a major cost and energy hurdle for the efficient production of algal biomass. Crossflow microfiltration has been found to be promising for the algal cell concentration process. Three algal strains with different cell sizes and morphology, namely Chlorella vulgaris, Nannochloris sp., and Scenedesmus sp., were studied. Analysis of the culture suspensions showed very different particle size distributions for the selected strains due to cell clustering. For a given membrane under the same operational conditions to achieve an equal volumetric reduction factor, Nannochloris sp., with the biggest particles and smallest cells, demonstrated the highest permeation flux, and in the same order of the particle sizes, it was followed by Chlorella vu. and Scenedesmus sp. For all the selected algal species, the highest dewatering rate (176–303 L/m²·h) was obtained by means of the membrane with the smallest pore size of 0.05 µm. Full article

Since 2011, pelagic sargassum blooms (S. fluitans and S. natans) have impacted coastal communities, aquaculture, tourism, and biodiversity across the Tropical Atlantic region. Whilst the initial event is generally attributed to an anomalous North Atlantic Oscillation (2009–2010), the drivers of sargassum movement and proliferation remain unclear. This research gap is particularly evident in West Africa, where annual and seasonal sargassum variability is under-researched, and a lack of consensus exists on seasonal and annual trends. This paper addresses these gaps by (1) providing a first attempt at characterising the seasonal and annual trends of sargassum biomass in the Eastern Tropical Atlantic, through using satellite imagery to create a time-series for 2011–2022; and (2) exploring the hypothetical drivers of movement and proliferation of sargassum for this area, through assessing its co-variation with potential drivers including atmospheric, oceanic, and policy, establishing a historical timeline of events. The time-series analysis reveals an annual biomass peak in September and a second peak between March and May. The exploration of potential drivers reveals that alongside sea surface temperature there are multiple factors that could be influencing sargassum biomass, and that further research is necessary to clarify primary and secondary drivers. The results contribute to understanding drivers, impacts, and predictions of sargassum blooms in the Eastern Tropical Atlantic. We anticipate that our findings will enable sargassum-affected areas to better anticipate the size and timing of sargassum events in West Africa and offer researchers a new perspective on possible drivers of proliferation within the wider Tropical Atlantic region. Full article

Reservoirs and downstream rivers draining Oregon’s Cascade Range provide critical water supplies for over 1.5 million residents in dozens of communities. These waters also support planktonic and benthic cyanobacteria that produce cyanotoxins that may degrade water quality for drinking, recreation, aquatic life, and other beneficial uses. This 2016–2020 survey examined the sources and transport of four cyanotoxins—microcystins, cylindrospermopsins, anatoxins, and saxitoxins—in six river systems feeding 18 drinking water treatment plants (DWTPs) in northwestern Oregon. Benthic cyanobacteria, plankton net tows, and (or) Solid-Phase Adsorption Toxin Tracking (SPATT) samples were collected from 65 sites, including tributaries, reservoirs, main stems, and sites at or upstream from DWTPs. Concentrated extracts (320 samples) were analyzed with enzyme-linked immuno-sorbent assays (ELISA), resulting in >90% detection. Benthic cyanobacteria (n = 80) mostly Nostoc, Phormidium, Microcoleus, and Oscillatoria, yielded microcystins (76% detection), cylindrospermopsins (41%), anatoxins (45%), and saxitoxins (39%). Plankton net tow samples from tributaries and main stems (n = 94) contained saxitoxins (84%), microcystins (77%), anatoxins (25%), and cylindrospermopsins (22%), revealing their transport in seston. SPATT sampler extracts (n = 146) yielded anatoxins (81%), microcystins (66%), saxitoxins (37%), and cylindrospermopsins (32%), indicating their presence dissolved in the water. Reservoir plankton net tow samples (n = 15), most often containing Dolichospermum, yielded microcystins (87%), cylindrospermopsins (73%), and anatoxins (47%), but no saxitoxins. The high detection frequencies of cyanotoxins at sites upstream from DWTP intakes, and at sites popular for recreation, where salmon and steelhead continue to exist, highlight the need for additional study on these cyanobacteria and the factors that promote production of cyanotoxins to minimize effects on humans, aquatic ecosystems, and economies. Full article

Due to the adverse effects associated with synthetic cosmetic ingredients, global demand is increasingly shifting toward natural formulations that offer diverse benefits for enhancing skin health and overall beauty. Researchers around the world are extensively exploring a variety of unique natural secondary metabolites for cosmeceutical applications. Among the potential candidates, phlorotannins derived from brown seaweeds have shown significant potential as an active ingredient in cosmeceutical applications. The notable properties associated with phlorotannins include antioxidant, anti-aging, whitening, anti-wrinkling, anti-inflammatory, and hair health and growth-promoting effects, making them valuable in cosmeceutical formulations. However, to date, only a limited number of studies have critically reviewed the cosmeceutical applications of phlorotannins, and most are outdated. Thus, in the present review, primary attention is given to the collected scientific data published after 2020 about the bioactive properties of brown seaweed phlorotannins related to cosmeceutical applications. Full article

Functional genomics is a powerful approach for uncovering molecular mechanisms underlying complex biological processes by linking genetic changes to observable phenotypes. In the context of algal symbiosis, this framework offers significant potential for advancing our understanding of the molecular interactions between marine dinoflagellates and their cnidarian hosts, such as corals—organisms that are foundational to marine ecosystems and biodiversity. As coral bleaching and reef degradation intensify due to environmental stressors, novel strategies are urgently needed to enhance the resilience of these symbiotic partnerships. This opinion piece explores emerging directions in functional genomics as applied to coral–algal symbiosis, with a focus on uncovering the molecular pathways that govern photosynthesis and stress tolerance. We discuss the challenges and opportunities in applying functional genomics to support coral health, improve ecosystem resilience, and inform biotechnological applications in agriculture and medicine. Together, these insights posit the potential for engineered symbioses as a needed focus in mitigating biodiversity loss and supporting sustainable ecosystem management in the face of accelerating environmental change. Full article

Achnanthidium minutissimum is a widely distributed benthic freshwater diatom. The alga can produce stalks that stick the cell to the surface and subsequently extracellular capsules developing into biofilms. Extracts of the diatom-associated bacterium Dyadobacter sp. 32 have been shown previously to induce stalk and capsule formation by the diatom. Here, we studied the impact of macronutrients on the generation of stalks induced by bacterial extracts with respect to the frequency of stalk generation and stalk lengths, using axenic cultures to avoid any additional impact of bacteria on the nutrient availability. We found that nitrate deprivation inhibited cell division of A. minutissimum within four days, but it did not initially affect stalk production or elongation. Silica limitation instead inhibited both stalk production and elongation. Similarly, sulfate was required for stalk formation, which was supported by the energy-dispersive X-ray spectroscopy of A. minutissimum cells showing that sulfur was abundant in the stalks. Full article

Light characteristics, including spectrum and intensity, significantly impact cyanobacterial biomass production, pigment biosynthesis, and cellular metabolism, influencing the composition of various biochemical compounds. This study aimed to investigate the effects of light-emitting diode (LED) illumination on biomass, pigment, and lipid production in the unicellular halotolerant cyanobacterium Aphanothece halophytica, cultivated in a suitable natural seawater (SNSW) medium. The results revealed that LED light outperformed fluorescent light, with blue LED light, particularly at an intensity of 60 μmol photons m⁻² s⁻¹, significantly enhancing growth, pigment synthesis, and lipid accumulation. This resulted in a maximum cell density of 68.96 ± 1.52 × 10⁶ cells mL⁻¹, a specific growth rate of 0.302 ± 0.002 day⁻¹, and a lipid productivity of 56.81 ± 0.75 mg L⁻¹ day⁻¹. White LED light produced lipids suitable for biodiesel, whereas blue, green, and red LEDs promoted the accumulation of polyunsaturated fatty acids (PUFAs), beneficial for food supplements. These findings highlight the potential of LED-based cultivation strategies for optimizing biomass and biochemical compound production in A. halophytica. Full article