Allelopathy Effect of the Blue Diatom HasleaOstrearia (Gaillon) Simonsen: Growth Inhibition in Aquaculture Relevant Microalgae

We are well known that the marine pennate diatom Hasleaostrearia (Gaillon) Simonsen produces the blue-green pigment called marennine. Marennine was identified as a polyphenolic compound. This compound is capable to inhibit the growth of herpes simplex virus type 1 (HSV-1) and several bacteria, including pathogens as Vibrio sp. The aim of this study was to determine how strong the allelophatic effect of marennine is generated byH. ostrearia and identifying its minimal concentration that inhibits the growth of other microalgae. The experiment consisted of two phases of research activities. The first phase was biovolumecomparaison between H. ostrearia and microalgae suitable for aquaculture tested to take into account the differences in size of the microalgae tested(Tetraselmissuecica, Chaetocerosgracilis, Skeletonemacostatum, PavlovalutheriandIsochrysisgalbana (T-Iso) in term of H. ostrearia biomass and production of marennine. The second phase was the bioactivity tests, which is include growth kinetics, allelophatic effects and concentration of marennine in the culture medium, measured with spectrophotometer. The results of this study showed that H. ostrearia could inhibit several species of microalgae currently used in aquaculture (T. suecica, C. gracilis and S. costatum). The statistical analysis (One way ANOVA) showed that there are significant differences (P < 0, 05) between treatments andwhen co-cultured with H. ostrearia, these microalgae exhibited a significant growth inhibition. The highest inhibition value was 97.77% (on the treatementH. ostrearia+C. gracilis). In this treatment, the concentration of marennine in the culture was 5.35 mg L-1. According to the results, we can conclude that the supernatant of H. ostrearia with marennine acts as an allelochemical. The minimal concentration is 0.23 mg L-1 and the highest is 5.35 mg L-1. The treatments H. ostreariawithP. lutheri and T-Iso did not performed any inhibition

The application of microalgae feeding regime on whiteleg shrimp culture in each stage : a mini review

Feed management in shrimp culture aims to improve the quality of shrimp organisms. The application of the feeding regime in shrimp culture has been developed to determine the best formulation of diet in order to maximize growth rate and survival rate of shrimp by increasing feed efficiency and minimizing waste. The application of the feeding regime is closely related to the understanding of the physiological and morphological aspects of shrimp from the larval stage to the adult stage. The success of the application of feed management with the application of the feeding regime will be a solution to the problem of the high costs of feed needed in shrimp culture. The best formulation of diet in shrimp culture in the N6-P3 stage is microalgae, at the M1-PL10 stage is zooplankton, and in the juvenileadult shrimp stage is artificial feed. Microalgae can significantly increase the survival rate and growth rate of shrimp at the hatchery stage. This article aimed to examine the effect of the application of feeding regime using different diet formulations to produce the highest growth performance of shrimp in shrimp culture based on the morphological and physiological aspects of shrimp

Le phénomène du verdissement des bivalves par la marennine produite par l’Haslea ostrearia et ses conséquences sur la réponse intégrée de bivalves

This Ph.D. thesis focuses on several assessments to achieve the optimum benefit of utilization of marennine in the field of aquaculture. The study covers: (1) the assessment in feeding behavior of the Pacific oyster Crassostrea gigas on different sizes of Haslea ostrearia and its ecological consequence; (2) the characterization of the greening by marennine and its consequences on some physiological traits of on C. gigas. (3) the consequence of greening by marennine on behavioral, physiological and biochemical traits of bivalves; (4) the utilization of H. ostrearia and marennine in a combination diet with other microalgae relevant to aquaculture.Our results suggest that cell size impacts considerably the selection process of H. ostrearia by oyster. This study also demonstrates that the extracellular form of marennine contributes significantly to the greening in the mucocytes of the gills. Apart from greening the pallial organs of bivalves, marennine (2 mg L-1) affects the behavioural, physiological and biochemical performance. Nevertheless, these effects can be compensated for its biological activities such as natural antibacterial agent and use as a mixed algal diet for bivalve aquaculture.Le but de ce travail de doctorat est d’évaluer la possibilité d’utiliser Haslea ostrearia et la marennine en ostréiculture. Les objectives de ce projet sont : (1) l'évaluation du comportement alimentaire de l'huître creuse Crassostrea gigas sur des cellules d’H. ostrearia de différentes tailles et les conséquences potentielles sur les populations algales; (2) la caractérisation du verdissement par la marennine et ses conséquences sur la physiologie de C. gigas; (3) les conséquences du verdissement sur les traits comportementaux, physiologiques et biochimiques de plusieurs espèces de bivalves; (4) l'utilisation conjuguée d’H. ostrearia avec d'autres microalgues d’importance en aquaculture. Nos résultats suggèrent que la taille des cellules affecte considérablement le processus de selection d’H. ostrearia par l’huître. Cette étude démontre également que la forme extracellulaire de la marenninne contribue significativement au verdissement dans les mucocytes des branchies. Mis à part le verdissement des organes palléaux des bivalves, une concentration modérée de marennine (2 mg L-1) affecte les performances comportementales, physiologiques et biochimiques des bivalves. Néanmoins, ces effets pourraient être compensés par ses activités biologiques comme agent antibactérien naturel et source d’alimentation mixte d’algues en conchyliculture

Le phénomène du verdissement des bivalves par la marennine produite par l’Haslea ostrearia et ses conséquences sur la réponse intégrée de bivalves

This Ph.D. thesis focuses on several assessments to achieve the optimum benefit of utilization of marennine in the field of aquaculture. The study covers: (1) the assessment in feeding behavior of the Pacific oyster Crassostrea gigas on different sizes of Haslea ostrearia and its ecological consequence; (2) the characterization of the greening by marennine and its consequences on some physiological traits of on C. gigas. (3) the consequence of greening by marennine on behavioral, physiological and biochemical traits of bivalves; (4) the utilization of H. ostrearia and marennine in a combination diet with other microalgae relevant to aquaculture.Our results suggest that cell size impacts considerably the selection process of H. ostrearia by oyster. This study also demonstrates that the extracellular form of marennine contributes significantly to the greening in the mucocytes of the gills. Apart from greening the pallial organs of bivalves, marennine (2 mg L-1) affects the behavioural, physiological and biochemical performance. Nevertheless, these effects can be compensated for its biological activities such as natural antibacterial agent and use as a mixed algal diet for bivalve aquaculture.Le but de ce travail de doctorat est d’évaluer la possibilité d’utiliser Haslea ostrearia et la marennine en ostréiculture. Les objectives de ce projet sont : (1) l'évaluation du comportement alimentaire de l'huître creuse Crassostrea gigas sur des cellules d’H. ostrearia de différentes tailles et les conséquences potentielles sur les populations algales; (2) la caractérisation du verdissement par la marennine et ses conséquences sur la physiologie de C. gigas; (3) les conséquences du verdissement sur les traits comportementaux, physiologiques et biochimiques de plusieurs espèces de bivalves; (4) l'utilisation conjuguée d’H. ostrearia avec d'autres microalgues d’importance en aquaculture. Nos résultats suggèrent que la taille des cellules affecte considérablement le processus de selection d’H. ostrearia par l’huître. Cette étude démontre également que la forme extracellulaire de la marenninne contribue significativement au verdissement dans les mucocytes des branchies. Mis à part le verdissement des organes palléaux des bivalves, une concentration modérée de marennine (2 mg L-1) affecte les performances comportementales, physiologiques et biochimiques des bivalves. Néanmoins, ces effets pourraient être compensés par ses activités biologiques comme agent antibactérien naturel et source d’alimentation mixte d’algues en conchyliculture

Semi-continuous system for benthic diatom cultivation and marennine production

The feasibility of culturing different blue Haslea species and strains in different types of photobioreactors (PBRs) was studied on the long-term (until 151 days). The different strains of blue Haslea were selected for their peculiarity to produce marennine-like blue pigments as a potential industrial high-value compound. The present study aims at assessing several factors in PBRs to obtain sustained blue pigment production in semi-continuous culture. Therefore, the effect of mixing, silicate concentration in the culture medium and type of light on marennine or marennine-like pigment production were investigated in parallel to the productivity of different Haslea strains and species. It was shown that the presence of mixing in semi-continuous PBR affected marennine production, cultures without any mixing achieving significantly higher marennine concentrations and productivities. Additionally, concentrations of silica from 45 to 75 μg L−1 in the culture medium produced higher marennine concentrations than that of 30 μg L−1. There were no significant differences in marennine production between the LEDs mixing different color and fluorescent tubes in semi-continuous PBR, thus LED could be a great option from the sustainability standpoint. Marennine production in the standard conditions used for this work was largely different between species. Haslea sp. produced the lowest pigment yields comparatively to the three H. ostrearia strains showing similar marennine productivity over 14 mg L−1. Preservation, until 155 days of marennine separated from culture supernatant and concentrated (“blue water”) was increased at low temperature (4 °C) and absence of light. This study validates the efficiency of semi-continuous systems to support long-term marennine production. However, additional work is still needed to pinpoint other factors that can further reduce the costs and result in maximum yields of marennine for industrial applications. -- Keywords : Haslea ostrearia ; Marennine ; Semi-continuous culture ; Photobioreactor

Effect of culture supernatant from Haslea ostrearia on the clearance rate and survival rate of adult Pacific oyster Crassostrea gigas infected with Vibrio aestuarianus

The microalga Haslea ostrearia is known as a diatom with the peculiarity of producing a water soluble blue-green pigment called marennine. This pigment has antibacterial activities against pathogenic bacteria of bivalves produced in aquaculture. The present study evaluates the effect of culture supernatant of the diatom Haslea ostrearia containing marennine on the clearance rate (CR) and survival rate (SR) of adult Pacific oyster Crassostrea gigas infected with the bacterial pathogen Vibrio aestuarianus. The greening of oysters was conducted by exposing bivalves to 0.5 mg L-1 of marennine for three days, and the effect of marennine on the CR and SR of oysters was evaluated by comparing four groups of treatment: control, greened, control+infected and greened+infected. The SR of oysters in each treatment was monitored for 11 days. Our results showed that marennine concentration decreased with time and dropped significantly on the last day of greening, and that marennine at an initial concentration of 0.5 mg L-1 did not significantly affect the CR of oysters in all treatments. Mortality of oysters was only observed in the control+infected group, but it was not significantly different from the control. Hence, the present study showed that the greening using 0.5 mg L-1 of marennine did not affect SR of adult oyster C. gigas, but further studies are needed to determine whether H. ostrearia supernatant could be used as an antibacterial and prophylactic agent in bivalve aquacultur

Phycoremediation of mercury in the aquatic environment

Phycoremediation refers to the technology of using microalgae to reduce pollutants in the aquatic environment. The purpose of this study was to analyze the reduction of mercury heavy metal in the media by using several species of microalgae such as Spirulina maxima, Nannochloropsis oculata, Chlorella vulgaris, and Porphyridium cruentum. The algae were exposed to mercury during eight days of cultivation. A randomized design was set with three different concentrations of mercury, namely 1, 3, and 5 mg/dm3, with three replications for each concentration. The initial concentration of microalgae was set to 10 000 cells/cm3 for S. maxima and N. oculata, while the concentration for C. vulgaris and P. cruentum was set to 100 000 cells/cm3. The concentration of mercury was measured at the beginning (1st day), the middle (4th day), and the end of microalgae cultivation (8th day) by using the atomic absorption spectroscopy (AAS) tool. The result demonstrated a reduction of mercury concentration during the experiment in all experimental media, where the highest reduction was found at 1 mg/dm3 (p < 0.05). In conclusion, microalgae have their limited ability to absorb and adsorb heavy metals. Therefore, the utilization of low-concentration microalgae on reducing heavy metal such mercury is recommended and merits further investigation

Cell size-based, passive selection of the blue diatom Haslea ostrearia by the oyster Crassostrea gigas

International audiencePre-ingestive selection has been identified as a feeding mechanism of oysters that may influence their uptake of particles and microalgal cells. Oysters can feed specifically on the pennate diatom Haslea ostrearia, which produces the blue pigment marennine that is responsible for the greening of oysters. Because the size of particles or cells plays a significant role in the selection process, and given that diatoms experience a decrease in size as a consequence of vegetative reproduction, H. ostrearia consumption and marennine uptake might be influenced by pre-ingestive selection. We examined the role of H. ostrearia cell size in the selective feeding of Crassostrea gigas. Individual flow-through chambers were used to deliver mixtures of H. ostrearia of varying cell length to oysters. Inflow, outflow and pseudofaecal samples were collected from chambers during oyster feeding. Video-endoscopy was used to sample material in the dorsal and ventral particle tracts. Diatom cells counts showed that pseudofaeces contained on average larger cells than the ambient medium. However, proportions of the different populations of H. ostrearia in pseudofaeces were identical to those in the ventral tracts, indicating that no selection was performed by the labial palps. Video-endoscopy, plus imaging by scanning electron microscopy, of gills and labial palps revealed that only those larger H. ostrearia that were orientated dorsoventrally could enter the principal filaments (pfs) and then access the dorsal acceptance tract. These results show that for particles like Haslea cells with only one axis exceeding the width of the pfs, the selection on the oyster gills is passive and based on cell size

Cell size-based, passive selection of the blue diatom Haslea ostrearia by the oyster Crassostrea gigas

International audiencePre-ingestive selection has been identified as a feeding mechanism of oysters that may influence their uptake of particles and microalgal cells. Oysters can feed specifically on the pennate diatom Haslea ostrearia, which produces the blue pigment marennine that is responsible for the greening of oysters. Because the size of particles or cells plays a significant role in the selection process, and given that diatoms experience a decrease in size as a consequence of vegetative reproduction, H. ostrearia consumption and marennine uptake might be influenced by pre-ingestive selection. We examined the role of H. ostrearia cell size in the selective feeding of Crassostrea gigas. Individual flow-through chambers were used to deliver mixtures of H. ostrearia of varying cell length to oysters. Inflow, outflow and pseudofaecal samples were collected from chambers during oyster feeding. Video-endoscopy was used to sample material in the dorsal and ventral particle tracts. Diatom cells counts showed that pseudofaeces contained on average larger cells than the ambient medium. However, proportions of the different populations of H. ostrearia in pseudofaeces were identical to those in the ventral tracts, indicating that no selection was performed by the labial palps. Video-endoscopy, plus imaging by scanning electron microscopy, of gills and labial palps revealed that only those larger H. ostrearia that were orientated dorsoventrally could enter the principal filaments (pfs) and then access the dorsal acceptance tract. These results show that for particles like Haslea cells with only one axis exceeding the width of the pfs, the selection on the oyster gills is passive and based on cell size

Haslea nusantara (Bacillariophyceae), a new blue diatom from the Java Sea, Indonesia: morphology, biometry and molecular characterization

Background and aims – The present study aims to describe a new species of pennate blue diatom from the genus Haslea, H. nusantara sp. nov., collected from Semak Daun Island, the Seribu Archipelago, in Indonesian marine waters.Methods – Assessment for species identification was conducted using light microscopy, Scanning Electron Microscopy and molecular techniques. The morphological characteristics of H. nusantara have been described, illustrated and compared to other morphologically similar blue Haslea taxa, distributed worldwide. Additionally, molecular characterization was achieved by sequencing plastidial and mitochondrial genomes.Key results – This new species, named Haslea nusantara, cannot be discriminated by its morphology (stria density) but it is characterized by its gene sequences (rbcL chloroplast gene and cox1 mitochondrial gene). Moreover, it differentiates from other blue Haslea species by the presence of a thin central bar, which has been previously reported in non-blue species like H. pseudostrearia. The complete mitochondrion (36,288 basepairs, bp) and plastid (120,448 bp) genomes of H. nusantara were sequenced and the gene arrangements were compared with other diatom genomes. Phylogeny analyses established using rbcL indicated that H. nusantara is included in the blue Haslea cluster and close to a blue Haslea sp. found in Canary Islands (H. silbo sp. ined.).Conclusions – All investigations carried out in this study show that H. nusantara is a new blue-pigmented species, which belongs to the blue Haslea clade, with an exceptional geographic distribution in the Southern Hemisphere