Phycology

Cyanobacteria are promising organisms for the sustainable production of various biotechnological interesting products. Due to their energy production via photosynthesis, the cultivation of cyanobacteria expands the CO₂ cycle. Most cyanobacteria form biofilms on surfaces in their natural environment by surrounding the cells with a self-produced matrix of extracellular polymeric substances (EPS) that hold the cells together. These special growth properties need special reactors for cultivation. By immobilizing cyanobacteria on carriers, systems currently established in industry could also be used for biofilm formers. Various artificial carriers for immobilized growth of cyanobacteria and microalgae have already been described in the literature. However, the use of waste materials or natural biodegradable carriers would be more sustainable and is, therefore, the focus of this study. Dried Luffa cylindrica, zeolite, and corn stalks were investigated for their use as carriers for cyanobacteria. L. cylindrica was shown to be an excellent natural carrier for (i) Anabaena cylindrica, (ii) Nostoc muscorum 1453-12a, and (iii) Nostoc muscorum 1453-12b. Higher or at least similar growth rates were achieved when cyanobacteria were cultivated with L. cylindrica compared to submerged cultivation. Additionally, the production of EPS and C-phycocyanin was increased at least 1.4 fold in all strains by culturing on L. cylindrica. The improved growth could be explained on the one hand by the high surface area of L. cylindrica and its properties, and, on the other hand, by the release of growth-promoting nutrients from L. cylindrica to the medium. Full article

Symbiotic microalgal–bacterial biofilms can be very attractive for potato wastewater treatment. Microalgae remove nitrogen and phosphorus and simultaneously produce the oxygen that is required for the aerobic, heterotrophic degradation of organic pollutants. In this study, symbiotic microalgal–bacterial biofilms were grown in flow cells with ammonium and phosphate, and with acetate as a simulated biodegradable organic pollutant. The symbiotic biofilms removed acetate without an external oxygen or carbon dioxide supply, but ammonium and phosphate could not be completely removed. The biofilm was shown to have a considerable heterotrophic denitrification capacity. The symbiotic relationship between microalgae and aerobic heterotrophs was proven by subsequently removing light and acetate. In both cases, this resulted in the cessation of the symbiosis and in increasing effluent concentrations of both acetate and the nutrients ammonium and phosphate. Full article

Since 2011, the Caribbean and Gulf of Mexico coasts have been receiving massive influxes of holopelagic sargasso algae composed of Sargassum natans and Sargassum fluitans. This phenomenon has been causing several negative local impacts, such as ecological disturbances and socioeconomic and health concerns of communities in impacted areas. This work aimed to assess the status of scientific knowledge related to pelagic sargasso, including trends, emphases, and gaps. A literature review was conducted on publications and reports from 2011 to 2022, of which 251 articles were collected based on an inclusion–exclusion criteria. Aspects of each article were quantified, including location, description of sargasso, the type of study, and research theme. A region-wide research emphasis on ecology, remote sensing, and valorization was observed. Areas first affected by the inundations composed a higher percentage of sargasso studies than other locations, and the distribution of studies varied among subregions. Topics requiring further investigation include sargasso’s growth and mortality rates and drivers, taxonomic and physiologic differences among morphotypes, and real-time forecasting resolution at local scales both on and offshore. This research emphasized efforts from the scientific community on research and mitigation initiatives. Full article

Thrombosis is characterized by the pathological formation of fibrin clots within a blood vessel, leading to the obstruction of blood flow. Fibrinolytic enzymes from microorganisms have been shown to be more efficient and safer in dissolving clots. Then, this study aimed to evaluate the cell growth and fibrinolytic enzyme production of Tetradesmus obliquus under different cultivation conditions. T. obliquus grew under autotrophic and mixotrophic conditions using different concentrations of corn steep liquor (0.25 ≤ CSL ≤ 4.00%). The cells were concentrated and lysed via two different methods (sonication or homogenization) to trigger the release of the enzyme. It was precipitated via acetone or ammonium sulfate additions and purified using ion exchange chromatography. The highest biomass productivity (P_x = 130 ± 12.8 mg∙L⁻¹day⁻¹), specific growth rate (µ_max = 0.17 ± 0.00 day⁻¹), and fibrinolytic activity (391 ± 40.0 U∙mg⁻¹) was achieved on a mixotrophic cultivation at a 0.25% CSL concentration. The results showed that the homogenizing method had better performance in the release of enzyme, and the precipitation with acetone obtained the highest fibrinolytic activity (567 ± 49.3 U∙mg⁻¹). The purified enzyme showed a specific activity of 1221 ± 31 U∙mg⁻¹ and a molecular mass of 97 kDa. So, the fibrinolytic enzyme from T. obliquus had higher activity when compared to the other fibrinolytic enzymes, being a potential source for the development of therapeutic agents in thrombosis treatment. Additional studies are needed to investigate the biochemical properties and biological profile of this enzyme. Full article

Salinization and warming are of increasing concern for freshwater ecosystems. Interactive effects of stressors are often studied in bifactorial, two-level experimental setups. The shape of environmental reaction norms and the position of the “control” conditions along them, however, can influence the sign and magnitude of individual responses as well as interactive effects. We empirically model binary-stressor effects in the form of three-dimensional reaction norm surfaces. We monitored the growth of clonal cultures of six freshwater diatoms, Cymbella cf. incurvata, Nitzschia linearis, Cyclotella meneghiniana, Melosira varians, Ulnaria acus, and Navicula gregaria at various temperature (up to 28 °C) and salinity (until the growth ceased) shock treatments. Fitting a broad range of models and comparing them using the Akaike information criterion revealed a large heterogeneity of effects. A bell-shaped curve was often observed in the response of the diatoms to temperature changes, while their growth tended to decrease with increasing electrical conductivity. C. meneghiniana was more tolerant to temperature, whilst C. incurvata and C. meneghiniana were the most sensitive to salinity changes. Empirical modelling revealed interactive effects of temperature and salinity on the slope and the breadth of response curves. Contrasting types of interactions indicates uncertainties in the estimation by empirical modelling. Full article

Since 2011, the distribution, abundance, and composition of holopelagic Sargassum spp. (sargasso) have changed by the emergence of the Great Atlantic Sargasso Belt (GASB) in the northern tropical Atlantic. We expected that the north of the Cuban coast would receive sargasso from both the original Sargasso Sea and the GASB. We systematically monitored six beaches on the NW coast of Cuba to assess changes in sargasso composition from June 2019 to June 2021. During landing months, mean Sargasso wet biomass was at 1.54 kg/m² (SE: 0.7), which was considerably lower than the sargasso on the Atlantic coasts directly impacted by GASB. Eleven out of 13 landings occurred in the autumn-winter seasons 2019–2020 and 2020–2021, with a dominance of S. natans I (accounting for 41–63% of total biomass), followed by S. fluitans III (25–36%) and S. natans VIII (12–31%). This composition is similar to those observed on the Sargasso Sea. During this season, dominant winds (≥14 km/h) came from northern (N), eastern (E), and east-northeastern (ENE) directions. In May and August 2020 (spring-summer season), S. fluitans III dominated (52–56%), followed by S. natans VIII (33–43%) and S. natans I (5–12%). This composition is similar to those observed on GASB-impacted Atlantic coasts in the spring-summer seasons (April to September). During this season, dominant winds (≥20 km/h) came from eastern (E) and east-northeastern (ENE) directions. Thus, the NW Cuba’s morphotype composition suggests that landings have different origin sources depending on season and specific meteorological and oceanographic conditions. Full article

Mycosporine-like amino acids (MAAs) are natural UV-absorbing compounds found in microalgae and macroalgae. The content of MAAs in algae varies with the seasons and environmental factors. Red alga dulse in Usujiri (Hokkaido, Japan) is an underutilized resource. Therefore, we investigated the amount of MAAs in Usujiri dulse in 2022 to clarify the suitable months for MAA extraction. In addition, we also evaluated the extraction method focusing on the extraction volume. MAAs were prepared via the 20 volumes of 25% ethanol extraction method and detected via HPLC. The results showed that the amount of MAAs on 25 March 2022 showed the highest value (40.4 μmol/g DW) among the samples from 24 January to 13 May. The tendency of suitable samples for MAA preparation corresponded to the term from mid-February to early April, which was the same as the previous three years. Although the surveys from 2019–2021 were performed by using the successive water–methanol method, it was found that the improved method also reflected the monthly variation in MAAs. The extraction of MAAs was performed via 20 or 40 volumes of 25% ethanol at 4 °C for 24 h. The amount of MAAs with 40 volumes of 25% ethanol extraction increased 1.3-fold compared to that with 20 volumes of 25% ethanol extraction. These data are useful information for valuable compound extraction from Usujiri dulse. Full article

The harmful impacts of the ongoing Sargassum invasions in the Atlantic Ocean include fish kills, skin and eye irritation, beach fouling, and declines in fisheries and tourism in West Africa and the Americas. This study was conducted to address important gaps in the non-market valuation literature and support the design of effective adaptation policies to reduce the harmful impacts of algal blooms. Contingent valuation survey data and linear mixed-effects regression models were utilized to estimate the drivers of willingness to pay (WTP) and willingness to contribute time (WTCT) for the management of invasive Sargassum seaweeds in Ghana. The study revealed that income, education, family size, years of residence, sex, attitudes, and political affiliation are significant drivers of WTP, while distance to the beach, occupation, house ownership, attitudes, and political affiliation are also significant predictors of WTCT. Hence, only attitudes about invasive seaweeds and political affiliation influence both WTP and WTCT. The findings suggest that for developing countries to generate enough funding and adequate economic support for coastal resource conservation, they should design local resource protection programs that give residents the option to contribute both time and money. Full article

Using the fluorescent method in the modification of Krasnoyarsk State University, we studied the development (as chlorophyll content, ∑CHL) and photosynthetic activity of phytoplankton in seven large flat reservoirs of the Volga River cascade (Russia) in August 2015–2017. In the period of the maximal warming of water, average ∑CHL varied in limits of 19.4–33.7 μg L⁻¹ in the Upper Volga, 8.5–27.8 μg L⁻¹ in the Middle Volga, and 5.2–11.3 μg L⁻¹ in the Lower Volga. The photosynthetic activity coefficient (PhAC) varied mostly in limits of 0.12–0.59, with an average of 0.22–0.38 and only in 2017 decreased to minimal < 0.10 and average < 0.20. The average PhAC values show the normal physiological state of the phytoplankton of the Upper Volga during all periods of observation, with an occasional decrease in PhAC in the Middle Volga and low photosynthetic activity in the Lower Volga. A decrease in the average ∑Chl and PhAC in 2017 was under cyclonic windy weather with a large amount of precipitation, low solar radiation, and large volume of flow. A trend towards a decrease in ∑CHL, like a decrease in PhAC from the Upper Volga to the Lower Volga, is explained by an increase in the flow rate and volume of runoff downstream of the Volga River. Full article

Anthropogenic activities cause the introduction of nitrogen (N) into aquatic environments where these N inputs drive the biological synthesis of nitrous oxide (N₂O), a potent and ozone-depleting greenhouse gas. To assess the significance of N₂O emissions to climate change, the Intergovernmental Panel on Climate Change (IPCC) estimates indirect N₂O emissions from rivers, lakes, and estuaries by multiplying the amounts of N received by these ecosystems with specific emission factors. Interestingly, the IPCC recently increased the N₂O emission factor associated with wastewater discharge into “nutrient-impacted (eutrophic) aquatic receiving environments” nearly four times based on experimental evidence of high N₂O emissions from N-receiving eutrophic ecosystems. As microalgae can produce N₂O, these organisms may contribute to the N₂O emissions frequently reported in eutrophic aquatic bodies. If that is the case, estimating N₂O emissions solely based on nitrogen inputs to water bodies might lead to inaccurate N₂O budgeting as microalgae growth is often limited by phosphorus in these environments. Establishing the significance of microalgal N₂O synthesis in eutrophic environments is, therefore, critical and may lead to considerable changes on how to budget and mitigate N₂O emissions and eutrophication. Full article

The key role of benthic diatoms in coastal ecosystems highlights the relevance of studying their biodiversity and developing integrated biodiversity conservation measures. Benthic diatom richness in the northern part of the Black Sea was estimated based on both published data and our own data. The checklist of benthic diatoms includes 1100 species and intraspecific taxa, 953 species, 149 genera, 61 families, 32 orders, and 3 classes of Bacillariophyta. More than 280 species and intraspecific taxa, as well as 8 genera new to the diatom flora of the Black Sea and 7 species new to science, were revealed. An interregional analysis of the diversity of benthic Bacillariophyta along the coasts of Bulgaria, Romania, and Crimea, as well as the northwestern and northeastern parts of the Black Sea shelf, was carried out using the Taxonomic Distinctness Indices (TaxDI). The lowest TaxDI value for Crimea was closest to the average value expected for the Black Sea diatom flora, indicating a large proportion of polyspecies branches in the taxocene structure, which resulted in the maximum species richness (species/genus = 7) and led to a decrease in the vertical evenness of hierarchical tree. On the contrary, the highest TaxDI value was detected off the Romanian coast, which was caused by the significant proportion of mono- and oligospecies branches and minimal species saturation in the taxocene structure (species/genus = 4). We also identified some species with a high taxonomic exclusivity rank. If these species disappear, the entire architectonics of the Black Sea hierarchical tree of Bacillariophyta may be significantly altered. Such region-specific species are given the highest protection priority since they have great importance for gene pool conservation. Full article

Microalgae have a high growth rate, high CO₂ absorption capacity, and high content of chlorophyll, proteins, vitamins, mineral salts, carbohydrates, antioxidant substances, and fatty acids. In recent years, Chlorella vulgaris has been widely used as a feedstock for producing third-generation biofuels, such as bioethanol. Thus, this work aims to develop a strategy to increase the production scale of the microalgae Chlorella vulgaris grown in distilled reused water, supplemented with a modified BG-11 medium, to use biomass in the production of bioethanol. The total cultivation of 72 L presented a concentration of 0.415 g·L⁻¹·d⁻¹, with 61.32 g of final biomass. To improve carbohydrate extraction, the biomass was pre-treated with sulfuric acid at different concentrations (1.5% and 3% v/v). The hydrolyzed solution was supplemented with YPD (yeast extract peptone dextrose) medium and inoculated with Saccharomyces cerevisae yeast, initiating fermentation. In each sample, the Brix degree, cell concentration, reducing sugar concentration, and alcohol content were analyzed. The sample pre-treated with sulfuric acid 1.5% v/v was the one that presented the best result, with alcohol content after distillation of 68 °GL (Gay-Lussac). It appears that the cultivation of the microalgae Chlorella vulgaris in scale-up, with reused water, has high potential in the production of third-generation biofuel. Full article

The genus Amphidinium Clap. & J. Lachm. comprises a high diversity of planktonic and benthic (epiphytic and sand-dwelling) dinoflagellates from marine and freshwater ecosystems. High morphological plasticity and vaguely defined genus characteristics (e.g., a small epicone size) have complicated the clear delineation of species boundaries. Although six Amphidinium morphospecies have been reported from Mexican coastal waters, species identifications are uncertain and not generally supported by molecular phylogenetic data. In this study, seven isolates of Amphidinium from diverse benthic coastal locations on the NE Pacific, Gulf of California, and southern Gulf of Mexico were subjected to critical morphological analysis using photonic and scanning electron microscopy. The phylogenetic reconstruction was based on nuclear-encoded, partial large-subunit (LSU) rDNA and internal transcribed spacer I and II (ITS1 and ITS2) sequences. The revised phylogenetic analysis was consistent with the traditional subdivision of the genus Amphidinium into two sister groups: Herdmanii and Operculatum clades. This study provided the first confirmed records of A. theodorei and A. massartii from coastal waters of Mexico. The molecular phylogenetic evidence indicated that the morphologically described A. cf. carterae from Baja California was in fact more closely allied with A. eilatiensis sequences. A few Amphidinium species are known to form toxigenic (i.e., fish-killing) harmful algal blooms worldwide, and therefore knowledge on species diversity and biogeography is critical in developing effective strategies for evaluating the potential emerging threat in Mexican coastal waters. Full article

Streams play vital roles in surrounding communities and provide essential ecosystem services. The protection of streams is important, they are legally protected under the Clean Water Act, and they can be monitored through the continuous analyses of biological data, such as algal or other aquatic communities. The goals of this study were to analyze the long-term recovery of Tobler Creek, a recovering agricultural stream on the site of a National Historic Landmark, and yield comparisons to a local low-impact stream, Murder Creek, located within the Oconee National Forest. In 2011, Tobler Creek exceeded reference criteria values for total phosphorus (TP) but met the nitrate nitrogen criteria. With an 11-year recovery period, Tobler Creek met both nutrient reference criteria. In 2022, periphyton samples were collected according to standard protocols, confirming that diatoms are the dominant algal group in the community. With recovery, Tobler Creek showed an increase in diatom species richness (χ2 = 116.11, df = 5, p < 0.01) but this was significantly lower than the values documented in Murder Creek. The multi-metric index (MMI), calculated using diatom community analysis to estimate ecological health, indicated that Tobler Creek experienced degradation from 2011 to 2022 (χ2 = 55.97, df = 5, p < 0.05) and is below the regional 25th percentile. The percentage of sediment-tolerant taxa (surirelloid, naviculoid, and nitzschoid) was significantly higher in Tobler Creek in 2022 (χ2 = 500.96, df = 5, p < 0.01) compared to Murder Creek in 2022 (t = −4.67, df = 10, p < 0.01). Despite a reduction in nutrients given the 42-year recovery period, the diatom community in Tobler Creek was significantly different than other regional protected streams. Ecological degradation of the habitat was likely driven by sedimentation due to run-off in the recovering agriculture stream. These findings highlight the importance of protecting water quality, as the recovery of nutrients can be a decades-long process overlayed with many potentially new stressors influencing aquatic organisms. Full article

The constant production of solids in intensive shrimp and tilapia culture can affect the performance of macroalgae when cultivated in an integrated system, and little is known about culture structures that enhance the performance of macroalgae in biofloc systems. The objective of this work was to evaluate different depths of culture structure for the macroalgae Ulva lactuca in an integrated system with Litopenaeus vannamei and Oreochromis niloticus in a biofloc system. The experiment lasted 70 days, with six systems composed of: a 16 m³ shrimp tank, a 3 m³ tilapia tank, and a 3 m³ macroalgae tank, with water recirculation between tanks. Two treatments were carried out, shallow float, with a structural depth of 10 cm, and bottom float, where the depth was kept at 30 cm from the surface. The shallow float resulted in a growth rate of up to 0.95 ± 0.54% day⁻¹, with biomass loss only at the end of the culture due to the high density of macroalgae, decreasing temperature, and increasing solids concentration. The bottom float had biomass loss throughout the culture cycle. The integrated culture of shrimp, fish, and macroalgae is feasible with the use of shallow floats within 10 cm from the surface. Full article

To describe the seasonal response of the major phytoplankton groups to environmental variables along the Campeche coast, southeastern Gulf of Mexico, seven shallow-water (ca. 1 m) stations were monitored from January 2019 to January 2020. Orthophosphate, ammonium, nitrite, nitrate and silicate were measured. Several tests, including ANOVA, the Kolmogorov–Smirnov test, Tukey TSD, Bartlett’s test and canonical correspondence analysis (CCA), were applied. The physicochemical variables (temperature, salinity and pH) recorded are typical for the central coast of Campeche. Seasonal characteristics are affected by the shallowness of the study area. The variation of inorganic nutrient concentrations is likely to be related to specific polluting activities. While the abundance of phytoplankton presented a minimum value of 4.1 × 10⁴ cells L⁻¹ in March, the maximum value of 8.8 × 10⁶ cells L⁻¹ occurred in May; the general average was 5.3 × 10⁵ cells L⁻¹. Based on CCA, the correlation between major phytoplankton groups and physical–chemical variables was high (r ≈ 0.8), indicating a significant relationship. The CCA graphs separated the samples of diatoms by higher values of pH and silicate and separated the samples of cyanobacteria with high values of temperature (>30 °C) from the samples with dinoflagellates and nanoflagellates. Nanoflagellates were abundant in the samples with high values of ammonium and phosphate. Full article

We report here the effects of cadmium on the metabolome of the macroalga Gracilaria caudata. The IC₅₀ of 3 mg/L (12 µM) was obtained after 48 hrs exposure and induced lower photosynthesis efficiency. Threshold concentrations determined by the Brazilian Environmental Council (CONAMA) in marine waters (0.04 mg/L) and effluent discharge (0.2 mg/L) were also tested, and the latter changed photosynthetic efficiency similarly to IC₅₀. A total of 43 metabolites were identified, including monosaccharides, carboxylic acids, and amino acids. By an unsupervised PCA, we identified significative alterations in the metabolome by the IC₅₀. An OPLS-DA analysis showed that Cd²⁺ exposure caused the variation of 20 metabolites, mainly glyoxylate-related, ascorbate, floridoside and proline. Five metabolic pathways altered by Cd²⁺ showed an accumulation of amino acids, carbon metabolism intermediates and antioxidant responses to Cd²⁺. We recommend a review of the toxicity parameters and methods that guide environmental policies on cadmium levels in Brazilian marine waters. Full article

Benthic dinoflagellates of the Coolia genus have been associated with cytotoxicity and lethal and sublethal effects on marine species. This study aimed to assess the harmful effects of C. cf. canariensis phylogroup II (PII) and C. malayensis strains through bioassays. Experimental exposures (24, 48, and 72 h) of Artemia salina nauplii to Coolia species (330–54,531 cells mL⁻¹) were performed independently. When a concentration-dependent response was achieved, additional experiments were carried out to evaluate the cell-free medium toxicity. The two Coolia species were harmful to Artemia nauplii, inducing significant mortality and sublethal responses. Coolia cf. canariensis PII was the most toxic species, inducing significant lethality at lower concentrations and shorter exposure times, followed by C. malayensis. Only the survival curves achieved after 24 and 48 h of exposure to C. cf. canariensis PII fitted to a concentration–response curve with valid LC_50s of 18,064 and 19,968 cells mL⁻¹, respectively. Moreover, extracellular compounds (i.e., culture filtrates) of C. cf. canariensis PII induced significant mortality to nauplii after 48 and 72 h. The toxicity of C. cf. canariensis PII was demonstrated for the first time using bioassays, and it was surprisingly higher than that of the C. malayensis strain, which was previously demonstrated to induce biological activity at the cellular and subcellular levels. Our findings highlight the harmful and lethal effects induced by Coolia cells and the importance of bioassays for toxicity assessments. Full article

With the growth in the number of people searching for ways to improve personal care, the consumer finds the solution in cosmetic products. However, this demand is currently made concomitantly with the demand for products of natural origin, including seaweed. Algae, in their composition, are full of bioactive compounds with several applications. Therefore, their insertion in cosmetics is evidenced in the high number of scientific studies, which makes this natural resource potentially useful for the cosmetic industry. From this, a review was conducted with the aim of highlighting some of these active compounds and the latent applicability and versatility of others. In addition, the best way to add to the production of these substances while staying in alignment with green consumption, the design of biorefineries, and the promising production of macroalgae on a large scale using green technologies was sought. Full article