Algal Cultures Research Articles

Enhancing Biomass Productivity by Forecast-Informed Pond Operations.

Microalgal cultivation for biofuels and proteins holds significant promise but faces challenges in achieving economically viable biomass productivity under variable environmental conditions. This study introduces a forecast-informed pond operation (FIPO) system that uses numerical weather prediction (NWP) ensemble forecasts and the biomass assessment tool (BAT) to optimize daily dilution rates for enhanced biomass production. In contrast to the current practice, where fixed dilution rates are based on operator experience, the FIPO system determines the optimal dilution rate based on future weather forecasts and biomass growth conditions. Our experiments validate the effectiveness of FIPO in both short- and long-term growth scenarios. In short-term experiments, FIPO increased biomass production by 21.3% compared to batch growth and 7.4% over fixed dilution (60% every 3 days) operations. The NWP forecast-informed operations achieved biomass production nearly identical to that using perfect weather forecasts, highlighting the accuracy of current NWP forecasts for guiding pond operations. In long-term experiments, FIPO resulted in biomass production increases of 13.3% and 17.8% compared to two fixed dilution rates (60% every 3 days and 20% daily). These findings underscore the viability of using NWP forecasts to optimize microalgal cultivation systems. By adjusting daily dilution rates in response to forecasted weather, operators can achieve higher biomass yields and mitigate risks associated with environmental variability. This study provides a foundation for future research and practical applications in commercial-scale microalgal production.

Culture Studies of Phytoplankton Isolated from Sumiling Dam and Their Bioremediation Capacity in Aquaculture Wastewater.

Sumiling Dam in Sarrat, Ilocos Norte, is home to diverse phytoplankton species. This study aims to isolate and identify phytoplankton species, optimize the cultivation of one phytoplankton under varying light, pH and temperature conditions, and assess its bioremediation capacity in aquaculture wastewater. Three stations were set up at the site, each with three sampling points spaced 3-5 meters apart. From each point, 300ml of water was collected using standard procedures and transported to the lab for phytoplankton identification. Samples were incubated in algae culture broth for 14 days, streak-plated for isolation, and cultured under light. Microscope examination was used to characterize phytoplankton species and the identification was verified by a professional. Ten phytoplankton species were identified, with Haematococcus sp. selected for wastewater bioremediation due to its optimal growth under specific conditions (81µmol m-2s-1, pH 9, 25±2°C). Experiments showed that Haematococcus sp. significantly reduced nitrogen and phosphorus in wastewater over 7-14 days, with Treatment 3 (1000mg/L) achieving the highest growth, chlorophyll, and nitrogen reduction, while Treatment 2 (750mg/L) excelled in phosphorus removal. These results underscore phytoplankton's potential for sustainable, large-scale wastewater bioremediation.

Proteinaceous corals reveal heterogeneity in shifting Southern California oceanographic regimes.

The Southern California Bight is an ecologically important region for many local and migratory fauna. We combine bulk and compound-specific amino acid stable isotope measurements in the skeletons of proteinaceous octocorals with new regional ocean modeling system model output to explore biogeochemical changes at two locations within the Bight - Santa Cruz Basin and Santa Barbara Channel. Separated by the Channel Islands, these sites display distinct oceanographic regimes. Corals from the southeastern Santa Cruz Basin display lower bulk δ13C and higher bulk δ15N values than those in the northern Santa Barbara Channel. Amino acid isotope analyses indicate that the higher δ15N values in Santa Cruz Basin reflect both higher δ15N of baseline primary production and nitrate and higher trophic positions of the sinking particles that comprise the coral's diet. These findings suggest low nitrate concentrations, more complete nitrate utilization, lower productivity, and a longer planktonic food web. A 50-year time series of coral skeleton δ15N bulk values increases with time, consistent with sediment cores that capture an increase in the δ15NNO3 advected into the central Bight. In contrast, the Santa Barbara Channel corals display decadal-scale fluctuations, likely driven by interdecadal fluctuations in upwelling and nitrate supply. These findings agree with physical-biogeochemical model simulations showing greater sensitivity of upwelled surface nitrate concentrations to ocean climate variability in the Santa Barbara Channel. The importance of nutrient availability on ecosystem structure is emphasized using compound specific amino acid analysis, in a way that may be overlooked in bulk isotope palaeoceanographic records.

Limited effects of microplastics on size-fractionated phytoplankton booming in estuarine system.

Despite the extensive presence and long-term exposure risks of marine microplastics (MPs), their impact on phytoplankton at the community level is still not very clear, especially considering the various size classes of phytoplankton. To address this issue, we investigated the spatial load of MPs in Linhong Estuary and conducted in-situ experiments of algal culture with added MPs. Our investigation showed that the abundance of MPs varied from 8 n/L to 50 n/L, with an average of 21.76±12.31 n/L. A high loading of MPs was spatially identified outside Linhong Estuary, and clear decreasing trend from land to sea was not observed. Further microscopic examination revealed fiber-shaped MPs dominated in all collections, reaching a proportion of 93%. The chlorophyll a concentrations were 2.69-25.50μg/L (9.14±6.59μg/L), 0.68-3.13μg/L (1.48±0.67μg/L) and 0.14-0.65μg/L (0.27±0.14μg/L) for microphytoplankton (20-200μm), nanophytoplankton (2-20μm) and picophytoplankton (0.2-2μm), respectively. The correlation analysis between MP abundance and chlorophyll a of phytoplankton and the in-situ experiment at an environmentally realistic level both indicated a negative relationship between MP abundance and microphytoplankton with respect to chlorophyll a content, but no adverse effects of MPs were found for nanophytoplankton and picophytoplankton with smaller sizes. Our findings indicate that exposure to realistic levels of MPs only cause a limited impact on size-specific phytoplankton communities studied, but long-term interactions between MPs and these species merit further field-based assessment in real-world scenarios beyond lab-based incubation.

Enrichment of Lipophilic Brevetoxins in Sea Spray Aerosol during Red-Tides

Red tide is caused by the accumulation of Karenia (K.) brevis, which produces brevetoxin (BTx), a neurotoxin. Excreted BTx is incorporated into sea spray aerosol (SSA), which is created from the bursting of bubbles at the ocean's surface. For the first time, this study measures the enrichment factor of BTx in K. brevis algal aerosol. During red-tide events in 2021 and 2022, aerosol and water samples were collected from Gulf Coast beaches in Southwest Florida with various levels of K. brevis growth. The concentrations of BTx in SSA were measured using an enzyme-linked immunosorbent assay kit. The concentrations of both aerosolized BTx and organic matter (OM) were normalized using that of sodium ions and were shown to be significantly higher than those observed in seawater. Lipophilic BTx is present in SSA at concentrations that are 2-4 orders of magnitude higher than seawater, and 1-2 orders of magnitude higher than concentrations of OM in SSA. Enrichment of aerosolized BTx was also simulated in the algal culture tank with two different aerosol generation methods. The estimated activity coefficient (order of 1019) of BTx in bulk seawater using the inorganic thermodynamic model indicates very poor solubility of BTx in seawater and supports its enrichment in ocean surfaces and SSA. Examining the enrichment factors of BTx and organic matter in SSA contributes to our comprehension of the potential respiratory challenges posed by inhaled algal aerosols during red tide occurrences. In addition, enriched BTx in the uppermost layer of the ocean during red tide blooms can adversely influence animals that inhabit in tide flats with neurological and respiratory impacts.

Production of Algae-Derived Biochar and Its Application in Pollutants Adsorption—A Mini Review

Developing algae cultivation for food, chemicals, and bio-energy generates a significant amount of algal waste/residue after utilization. Meanwhile, harmful algal blooms caused by abnormal proliferation of various algae produce a large amount of algal biomass, posing serious harm to human health, the environment and the economy. Converting algae body to biochar is a crucial method with which to take advantage of this resource. Biochar usually has a large specific surface area, developed pore structure, high cation exchange capacity and rich surface functional groups. With the advantage of stable physical/chemical properties and easy modification techniques, biochar posited as an ideal adsorption material. From the perspective of algal biomass utilization, this paper reviews the preparation and modification methods, structural characteristics, physicochemical properties and environmental implications of algal biochar. The adsorption effect and mechanisms of algal biochar on nutrients, heavy metals, and organic matter in water are introduced. In light of the current research status, the challenges faced in practical application of algae-derived biochar adsorption materials are pointed out, and a research direction for preparation and application is also developed, with a view to providing a reference for the further utilization of algae-derived biochar.

Importance, structure, cultivability, and resilience of the bacterial microbiota during infection of laboratory-grown Haematococcus spp. by the blastocladialean pathogen Paraphysoderma sedebokerense: evidence for a domesticated microbiota and its potential for biocontrol.

Industrial production of the unicellular green alga Haematococcus lacustris is compromised by outbreaks of the fungal pathogen Paraphysoderma sedebokerense (Blastocladiomycota). Here, using axenic algal and fungal cultures and antibiotic treatments, we show that the bacterial microbiota of H. lacustris is necessary for the infection by P. sedebokerense and that its modulation affects the outcome of the interaction. We combined metagenomics and laboratory cultivation to investigate the diversity of the bacterial microbiota associated to three Haematococcus species and monitor its change upon P. sedebokerense infection. We unveil three types of distinct, reduced bacterial communities, which likely correspond to keystone taxa in the natural Haematococcus spp. microbiota. Remarkably, the taxonomic composition and functionality of these communities remained stable during infection. The major bacterial taxa identified in this study have been cultivated by us or others, paving the way to developing synthetic communities to experimentally explore interactions within this tripartite system. We discuss our results in the light of emerging evidence concerning the structuring and domestication of plant and animal microbiota, thus providing novel experimental tools and a new conceptual framework necessary to enable the engineering of Haematococcus spp. microbiota toward the biocontrol of P. sedebokerense.

Farming of Indigenous Crayfish in Russia: A Mini-Review of Recent Studies.

Natural populations of crayfish in Europe have experienced significant declines due to the spread of crayfish plague, overfishing, competition with invasive crayfish species, and habitat degradation. Consequently, crayfish farming has gained importance in meeting the increasing demand for crayfish products. Although Russia boasts abundant water resources, the development of crayfish aquaculture remains nascent. In this review, we consolidate recent studies by Russian researchers that focus on various aspects of crayfish cultivation. Extensive cultivation in open ponds is the most suitable method, owing to its accessibility and lower costs; however, it necessitates suitable environmental conditions within the water bodies. The production cycle encompasses pond preparation, stocking, exploration, restoration, and monitoring. Controlled cultivation of egg-bearing females is essential for producing high-quality seedstock for subsequent rearing. Experimental evidence suggests that crayfish exhibit high adaptability to artificial conditions, with formulated diets comprising artificial feeds for sturgeon and powdered dried beef by-products demonstrating promising results in terms of growth performance. Plastic tangled threads and mink shelters are recommended to reduce cannibalism. Short-term grow-out of juvenile crayfish can yield a profit margin of 17%, while a complete two-year production cycle is projected to achieve financial break-even over three years. The primary challenges confronting the industry include disease management, cannibalism, the need for skilled technical personnel, and insufficient financial and policy support.

Rumen Bacterial Community Responses to Three DHA Supplements: A Comparative In Vitro Study.

The aim of this study was to investigate the loss of docosahexaenoic acid (DHA) from three supplements (two powders and one oil) after digestion (rumen and gastrointestinal) and their effects on the number and composition of rumen bacteria, using an in vitro approach. The concentration of supplements has a significant impact on the DHA loss rate and algal oil exhibited the highest rate of loss, but bioaccessibility was not significantly different from the other supplements. 16S rRNA sequencing showed that three DHA supplements altered the bacterial composition of in vitro batch cultures inoculated with rumen microorganisms from cows, and caused changes in the relative abundance of important bacterial phyla, families, and genera. DHA supplements altered the abundance of bacterial species, including Prevotella, Ruminobacter, Succiniclassicum, Succinivibrio, Lachnospiraceae, and Muribaculaceae. Importantly, these changes may be associated with the ruminal response in biohydrogenation. Algal oil has the most significant impact on rumen microbiota by reducing the richness and diversity of rumen microbiota, and significantly altering the composition of multiple important microbiota.

Indikator sirkularitas di dalam tata kelola limbah pabrik kelapa sawit studi kasus: limbah cair (pome) pabrik kelapa sawit

This research was motivated by the problem of liquid waste from palm oil mills. The research aims to find out and understand the current form of palm oil mill waste management, to find out the factors that support palm oil mill waste governance in realizing a circular economy. Determining circularity indicators is one method to see the performance of palm oil liquid waste processing (POME) management and is a benchmark for the level of circularity of palm oil mill governance. The research approach uses the MCI circularity indicator developed by the Ellen MacArthur Foundation in assessing circularity indicators for various POME waste management scenarios in palm oil mills. From various POME processing governance scenarios, namely: 1) Based on field practices in palm oil mills, 2) Based on government regulations regarding POME processing in palm oil mills, 3) Processing POME with biogas technology with an open pond system, 4) Processing POME with biogas technology with a CSTR system, and 5) Processing POME into fertilizer. Based on the assessment results of various scenarios, the MCI circularity values for PKS A, B, and C under existing conditions are as follows: 0.6009 for the current system, 0.5500 for compliance with regulations, 0.5781 for biogas processing with closed ponds, 0.6143 for biogas processing with CSTR, and 0.7065 for fertilizer production. The highest circularity value of 0.7065 is achieved through the scenario of processing POME into fertilizer. This shows that liquid waste management by palm oil mills in Indonesia is still dominated by traditional systems in the form of open ponds.

An appraisal of the competence of mathematical fuzzy logic approach via adaptive neuro-fuzzy inference system (ANFIS) in biodiesel production from algae oil

Abstract The fuel crisis and environmental problems can be resolved using biodiesel from various basic materials. This paper uses the transesterification process and segregation to produce biodiesel from algal oil. According to the four input factors (power, methanol-to-oil percentage, catalyst utilized, and process time), 29 experiments have been conducted to manufacture biodiesel. This work focuses on modeling and estimating the processes involved in producing biodiesel, specifically from algal oil, using the (ANFIS) adaptive neuro-fuzzy inference system methodology. The determination coefficient (R-square) and the mean root-mean-square error (RMSE) were employed to reconcile the ANFIS findings with the true results of the research. During training, the RMSE statistical variables were 1.209 and the R-squared was 0.9742. This instance, involves the ANFIS Framework additionally the Gaussian membership function was used and examined. This modeling approach shows promise for use in the biodiesel manufacturing process, potentially increasing the efficacy and efficiency of the generation of biodiesel from algal oil, given the high estimation accuracy shown by the ANFIS.

Effects of Monensin, Calcareous Algae, and Essential Oils on Performance, Carcass Traits, and Methane Emissions Across Different Breeds of Feedlot-Finished Beef Cattle

With the growing use of crossbred cattle in Brazilian feedlots and increasing pressure to reduce antibiotic use as growth promoters, this study examines the impact of three feed additives—monensin (MON), monensin with Lithothamnium calcareum (LCM), and a blend of essential oils (BEO)—on the performance of Nellore (NEL) and crossbred (CROSS) cattle. A total of 90 Nellore and 90 crossbred bulls were assigned to a completely randomized block design with a 2 × 3 factorial design for 112 days, and all received the same diet with varying additives. Their methane (CH4) emissions were estimated. All data were analyzed using the emmeans package of R software (version 4.4.1). Crossbred cattle outperformed Nellore in average daily gain (ADG), hot carcass weight (HCW), and dry matter intake (DMI), though feed efficiency remained unaffected. Across additives, no significant differences were observed in ADG, HCW, or dressing percentage. However, LCM had a lower DMI than the BEO, while MON showed better feed efficiency than the BEO. A breed-by-additive interaction trend was noted for DMI as a percentage of body weight (DMI%BW), with Nellore bulls on LCM diets showing the lowest DMI%BW. Crossbreeds had greater net energy (NE) requirements for maintenance (NEm) and gain (NEg), and MON-fed animals had greater NEm and NEg than the BEO. Crossbred bulls had greater daily methane (CH4) emissions than Nellore bulls. Animals on the BEO had greater daily CH4 emissions and greater g CH4/kg metabolic BW than LCM bulls. In conclusion, the addition of Lithothamnium calcareum to monensin did not enhance performance compared to monensin alone. Monensin outperformed the BEO in feed efficiency and nutrient utilization.

Patchiness of plankton ecosystem structure due to nutrient mixing along the shelf edge in the North Sea

Mid-water column turbulence has been shown to cause elevated vertical nutrient flux at the shelf edge in the northeastern North Sea. Here, we demonstrate that phytoplankton communities in this region tend to be dominated by larger cells (estimated from percentage of chlorophyll captured on a 10 μm filter) than beyond the shelf edge. Fv/Fm (PSII electron transport capacity) corrected for photoinhibition in the surface layer correlated in this study with the percentage of chlorophyll captured on a 10 µm filter (assumed to be large cells), suggesting that the phytoplankton community was responding to increased nutrients in the euphotic zone by increasing photosynthetic efficiency and altering community composition. The greatest abundances of larger copepods and the highest rates of Centropages typicus egg production were also generally found at the shelf edge. These results suggested that impact from increased nutrient fluxes cascaded up the planktonic food web. As these regions of nutrient flux were very localised, this led to sub-mesoscale heterogeneity in plankton ecosystem structure. Reports of higher abundances of fish and mammals at the shelf edge are common and we hypothesise that their distributions are a response to the impact of mid-water column nutrient upwelling on the plankton food web in the region.

The comparative effects of ω-7 fatty acid-rich sea buckthorn oil and ω-3 fatty acid-rich DHA algal oil on improving high-fat diet-induced hyperlipidemia.

This study explores the therapeutic potential of ω-3 algal oil (rich in DHA) and ω-7 sea buckthorn oil (rich in palmitoleic acid) in addressing hyperlipidemia and associated metabolic disorders. These oils regulate lipid metabolism through the PPARγ-LXRα-ABCA1/ABCG1 signaling pathway, reducing cholesterol accumulation, oxidative stress, and inflammation. In high-fat diet-induced hyperlipidemic mice, supplementation with these oils significantly improved lipid profiles, alleviated hepatic steatosis, and promoted cardiovascular health. The combination of ω-3 and ω-7 fatty acids showed synergistic effects, offering greater efficacy compared to individual treatments. These findings suggest that algal and sea buckthorn oils could serve as dietary supplements or therapeutic interventions for managing hyperlipidemia, non-alcoholic fatty liver disease (NAFLD), and cardiovascular diseases. This study highlights the potential of these oils as novel, natural solutions for metabolic health improvement.

Development of low-allergenicity algal oil microcapsules with high encapsulation efficiency using extensively hydrolyzed whey protein.

Algal oil is rich in docosahexaenoic acid, which is beneficial for infant development, but its susceptibility to oxidation necessitates microencapsulation. This study investigated the effects of incorporating varying ratios of octenyl succinic anhydride-modified starch (OSA-MS) into a base wall system comprising extensively hydrolyzed whey protein (eWPH) and maltodextrin (MD) to produce algal oil microcapsules with reduced allergenicity and high nutritional value, replacing whey protein isolate (WPI). The residual antigenicity of α-lactalbumin and β-lactoglobulin in eWPH was 3.60% and 3.88%, respectively. The addition of OSA-MS significantly enhanced emulsion stability in the eWPH/MD system for algal oil encapsulation. The highest microencapsulation efficiency (98.35%) was achieved with 21% OSA-MS, showing no significant difference from that of WPI/MD-based microcapsules. Furthermore, microcapsules prepared with eWPH/MD/OSA-MS (21%) exhibited smooth surfaces, good dispersibility, and high solubility (91.79%). These microcapsules also demonstrated superior oxidative stability after 18days of storage at 60°C compared to those with other OSA-MS ratios. Overall, incorporating OSA-MS into the eWPH/MD wall system achieved encapsulation performance comparable to WPI/MD, thereby broadening the application potential of eWPH in microencapsulation.

Odd-chain fatty acids-enriched fats improved the growth and intestinal morphology and function in milk replacers-fed piglets.

The intestinal development and nutritional needs of piglets after birth are similar to those of human infants. This study aimed to investigate the effect of odd chain fatty acids (OCFAs) with different forms on the growth and intestinal morphology and function in milk replacers-fed piglets, as a model for human infants. Forty 7-day-old piglets from 8 sows were randomly assigned into 5 groups (n = 8, each of them was from different litters) and fed sow milk or milk replacers supplemented with different kinds of fats (namely, the control fats, and the DHA algal oil-, OCFA algal oil-, and OCFA-enriched fats) for 21 days. The statistical analysis about the data from milk replacers-fed piglet groups was conducted on the one-way ANOVA. And the data between sow milk- and milk replacers-fed piglets were analyzed by unpaired t-test. Milk replacers supplemented with OCFA-enriched fats increased the average daily gain (ADG) and the ratio of villus height to crypt depth, increased the protein expression of Ki67, p-mTOR, p-p70S6k, Occludin, Claudin, and ZO-1 in selected intestines, and decreased the protein expression of p-ULK1, Parkin, and PINK1 to levels similar to the sow milk group (P < 0.05). Overall, milk replacers supplemented with OCFA-enriched fats improved the ADG and intestinal morphology and function of piglets to levels comparable to the sow milk-fed piglets.

Trophic diversity of the bloom-forming jellyfish community in the coastal waters of China assessed by stable isotope analysis

A growing realization indicates that the trophic ecology of jellyfish is more diverse than once thought, yet a holistic view reflecting the trophic structure and trophodynamics in bloom-forming jellyfish community remains rare. Based on stable isotope δ13C and δ15N analysis, we estimated the trophic characteristics of common blooms jellyfish Nemopilema nomurai, Cyanea spp., Aurelia coerulea and Aequorea spp. in the coastal waters of China (CWC). Our data indicated that most of the isotopic niche space in the overall planktonic food web was occupied by the bloom-forming jellyfish community. The large spectrum of isotopic niche highlights the diverse ecological roles and potentially broad trophic relevance of these jellyfish in the food web. The substantial trophic diversity of these jellyfish resulted from the various trophic positions occupied by different taxa, complicated niche differentiation and overlap patterns, inconsistent size-based trophic variation, and spatial and temporal variation patterns. Isotopic niche comparisons indicated the presence of niche differentiation, reflecting the difference and individual-specific characteristic in resource exploitation and feeding preference among different jellyfish. Additionally, the inconsistent size-based trophic variation among groups derived from an increase in trophic level with size for Cyanea spp., A. coerulea and Aequorea spp. medusae to no change for N. nomurai medusae, which suggests the complexity in size-related trophic shift patterns within the jellyfish group. Additional diversity also arose from variation in the spatiotemporal structuring of jellyfish trophic ecology, which might be caused by the occurrence of trophic heterogeneity at the base of the planktonic food web. In conclusion, our study characterized the trophic structures of the bloom-forming jellyfish community in the CWC, and revealed their trophic diversity resulting from interspecific, intraspecific (ontogenetic), and spatiotemporal variation. These results hold strong potential to further improve the understanding of the trophic ecology and functional roles of the jellyfish community. Furthermore, this study provides a systematic and valuable isotopic data set, spanning from the food web baseline to zooplanktonic organisms and jellyfish community, against which compare with trophic investigations in future in planktonic food web of the CWC.

Rare earth element and yttrium behaviour during metabolic transfer and biomineralisation in the marine bivalve Mytilus edulis: Evidence for a (partially) biological origin of REY anomalies in mussel shells.

Rare Earth Elements and Yttrium (REY) are widely used as proxies for environmental conditions and biogeochemical processes, but have also become (micro)contaminants of surface waters worldwide. Soft tissues and shells of mussels are increasingly used in environmental science and geology as bioarchives for REY, but REY fractionation by and in these organisms is still not well understood. We report on the distribution of REY in different compartments of marine M. edulis mussels from Norway, and in their ambient water and food (plankton). The shale-normalised REY patterns of all compartments studied decrease from light to heavy REY (LREY and HREY, respectively), while the LREY depletion occasionally reported in the literature cannot be observed. The bivalves show REY concentrations up to five orders of magnitude higher than those in ambient water (with preferential uptake of Ce and of LREY over HREY) but lower than those in their potential plankton food (with minor REY fractionation, except for preferential uptake of La and Y). While metabolic REY fractionation within the bivalves is minor, vital effects affect the REY distribution in the shells of M. edulis mussels. Rejection and decoupling of Ce during shell formation occurs due to Ce oxidation and formation of Ce(IV) solution-complexes in the extrapallial fluid (EPF). While discrimination against HREY incorporation results from strong solution-complexation of the HREY, preferential uptake of La, Gd and Y during shell formation is due to the less stable solution-complexes of these ions. These observations are compatible with the presence of siderophores in the EPF, suggesting that in contrast to freshwater mussel A. anatina, vital effects can to some extent affect the size of anomalies in the REY patterns of marine M. edulis shells. This implies that these anomalies are (partially) of biological origin, which limits their use as paleo-redox proxies.

Filter feeding in devil rays is highly sensitive to morphology.

Mobulid rays (manta and devil rays) use a highly specialized filtering apparatus to separate plankton food particles from seawater. Recent studies have indicated that captive vortices form within the microscale pores of the filter, which enhance filtration efficiency through a novel mechanism referred to as ricochet separation. The high throughput and clog resistance of this filtration process have led to the development of several bioinspired engineered filtration systems. However, it is still unclear how changes to the filter morphology influence the surrounding flow patterns and filtration efficiency. We address this question by examining the flow fields around and filtering properties of mobulid filters with systematically varied morphologies, using a combination of computational fluid dynamics and experiments on physical models. While the pore size is the principal determinant of filtration efficiency in a sieve filter, we found that the captive vortices in a mobulid filter grow or shrink to fill the pore, and changes in the pore size have modest effects. By contrast, the filtration efficiency appears to be highly sensitive to the orientation of the filter lobes (microscale plate-like structures). These results provide a foundation for interpreting the morphological differences between species and also for generating optimized bioinspired designs.

Photon statistics and unicellular algae cultivation characteristics under continuous illumination.

Despite the complexity of the photosynthetic system, a simple explanation is proposed for the photon-flux density dependence of P-I curves (biomass production rate versus flux density) and electron transfer rate curves (delivery transfer rate of excited electrons from PS II, the first stage of the photosynthetic process, to the second stage, PS I, versus flux density). It is shown that the photon-flux density dependence of these two entities is a direct consequence of the stochastic nature of photon arrival times on the chlorophyll antenna of PS II, the existence of a rate-limiting time scale of about 10 ms in the operation of the photosystem, and the magnitude of the average photon absorption cross-sectional area of the chlorophyll antennae.