Junda Lin

Effects of nitrogen source and concentration on biomass and oil production of a Scenedesmus rubescens like microalga

This investigation examined the effects of nitrogen source and concentration on the ash free dry biomass (AFDB) and oil accumulation and productivity of a Scenedesmusrubescens like alga cultivated in indoor photo-bioreactors and outdoor raceway ponds. Among the nitrogen sources ((NH4)2CO3, urea, NaNO3, urea and NaNO3 mixture), the algae fed with the mixture of urea-N and NaNO3-N had the highest AFDB productivity of 0.539±0.040 g/L/d and the content of fatty acid methyl esters (FAME) (%) fed with (NH4)2CO3-N increased continuously for 17 days and reached 42.94±2.05% in the indoor photo-bioreactors. The content of C18 series (as % of total FAME) was high in all the treatments of nitrogen sources. The algae fed with (NH4)2CO3-N had the highest FAME productivity of 0.133 g/L/d (P<0.001). The effect of ammonia concentration on the AFDB and FAME productivity was also studied during the 20-day cultivation in the outdoor raceway cultivation system. The mean FAME of the algae cultivated in the ammonia concentration of 1.0-1.5 mg/L were the highest (0.556±0.112 g/m2/d) (P<0.001). The total Kjeldahl nitrogen (TKN) in the algae and cultivation water decreased but the FAME content (%) of the algae increased during the nitrogen starvation phase.

Effects of inorganic carbon concentration on carbon formation, nitrate utilization, biomass and oil accumulation of Nannochloropsis oculata CS 179.

This investigation examined the effects of the inorganic carbon concentration (4, 0.8 and 0 g/L NaHCO(3)) on the carbon formation, nitrate utilization, growth and fatty acids compositions of Nannochloropsis oculata. The dissolved inorganic carbon (DIC) concentration in the three treatments decreased sharply during the first 6 days, and the percentage of dissolved organic carbon (DOC) (% of total organic carbon (TOC)) decreased with the depletion of the DIC. The NO(3)(-) assimilation of the algae was correlated with the DIC concentration. The algae in the highest DIC treatment had the highest specific grow rate (0.0843 d(-1)) (P<0.0001), and their biomass and fatty acid methyl esters (FAME) productivity were 84.00 and 9.69 mg/L/d, respectively (P<0.0001). Contents of C16 and C18 series (% of FAME) were high and the C16:0 increased with the decrease of C18:1 during the cultivation. The iodine value (IV) of the algae was low at the low DIC media.

Biomass production and fatty acid profile of a Scenedesmus rubescens-like microalga.

This investigation examined the effects of nitrogen-phosphate combined deficiency on the biomass yield, fatty acid methyl esters (FAME) production and composition from Scenedesmus rubescens-like microalga. A 15-day indoor culture was performed as a 3 × 3 factorial design (NaNO(3) levels: 3, 10 and 20mM; KH(2)PO(4) levels: 20, 50 and 150 μM). The algae grown under medium nitrogen concentration (10mM) and high phosphate concentration (150 μM) reached the highest biomass (1223.5 ± 152.5mg/L). Both nitrogen and phosphate had a significant influence on the FAME yield (P<0.05 and P<0.0001, respectively). The FAME yield from algae grown under low nitrogen (3mM) and phosphate concentration (20 μM) increased throughout the experiment and the highest FAME yield (42.2 ± 2.5% of AFDW) as well as C16 and C18 content (95.8 ± 1.6% of AFDW) was achieved under these conditions. Algae grown under medium nitrogen concentration (10mM) and low phosphate concentration (20 μM) had the highest FAME productivity (426.0mg/L ± 135.0mg/L). Thus, the lower nitrogen concentration (3mM-10mM) and low phosphate concentration (20 μM) would be an optimal combination tested to produce the most FAME from S. rubescens-like algae.

Effect of ferric ion on nitrogen consumption, biomass and oil accumulation of a Scenedesmus rubescens-like microalga.

This investigation examined the effects of ferric ion source and concentration on the biomass yield, fatty acid methyl esters (FAME) productivity and composition from Scenedesmus rubescens-like microalga. The algae cultivated with Fe(2+)-SO(4)(2-)/EDTA had higher ash free dry biomass (AFDB) production and in vivo chlorophyll a concentration than those with Fe(2+)-SO(4)(2-) and Fe(3+)-Cl(-) (P<0.001). The high or low Fe(2+) concentration can partly restrict the ammonia consumption, the AFDB and FAME accumulation. The algae at 1mg/L Fe(2+) concentration had the highest AFDB and FAME productivity (341.1 ± 25.8 and 107.8 ± 19.3mg/L/d) (P<0.001). The mean content of C16 and C18 series at all Fe(2+) concentrations was 88.6% ± 2.9% of total FAME, and it decreased with the increase of Fe(2+) concentrations. Among the fatty acids profiles, the contents of C18: 0, C18: 1n-7 and C18: 1n-9 are significantly changed under the different Fe(2+) concentrations, but not the contents of C16 series.

The dynamics of reproductive rate, offspring survivorship and growth in the lined seahorse, Hippocampus erectus Perry, 1810

Summary Seahorses are the vertebrate group with the embryonic development occurring within a special pouch in males. To understand the reproductive efficiency of the lined seahorse, Hippocampus erectus Perry, 1810 under controlled breeding experiments, we investigated the dynamics of reproductive rate, offspring survivorship and growth over births by the same male seahorses. The mean brood size of the 1-year old pairs in the 1st birth was 85.4±56.9 per brood, which was significantly smaller than that in the 6th birth (465.9±136.4 per brood) (P<0.001). The offspring survivorship and growth rate increased with the births. The fecundity was positively correlated with the length of brood pouches of males and trunk of females. The fecundity of 1-year old male and 2-year old female pairs was significantly higher than that from 1-year old couples (P<0.001). The brood size (552.7±150.4) of the males who mated with females that were isolated for the gamete-preparation, was larger than those (467.8±141.2) from the long-term pairs (P<0.05). Moreover, the offspring from the isolated females had higher survival and growth rates. Our results showed that the potential reproductive rate of seahorses H. erectus increased with the brood pouch development.

Genetic variations in two seahorse species (Hippocampus mohnikei and Hippocampus trimaculatus): evidence for middle Pleistocene population expansion.

Population genetic of seahorses is confidently influenced by their species-specific ecological requirements and life-history traits. In the present study, partial sequences of mitochondrial cytochrome b (cytb) and control region (CR) were obtained from 50 Hippocampus mohnikei and 92 H. trimaculatus from four zoogeographical zones. A total of 780 base pairs of cytb gene were sequenced to characterize mitochondrial DNA (mtDNA) diversity. The mtDNA marker revealed high haplotype diversity, low nucleotide diversity, and a lack of population structure across both populations of H. mohnikei and H. trimaculatus. A neighbour-joining (NJ) tree of cytb gene sequences showed that H. mohnikei haplotypes formed one cluster. A maximum likelihood (ML) tree of cytb gene sequences showed that H. trimaculatus belonged to one lineage. The star-like pattern median-joining network of cytb and CR markers indicated a previous demographic expansion of H. mohnikei and H. trimaculatus. The cytb and CR data sets exhibited a unimodal mismatch distribution, which may have resulted from population expansion. Mismatch analysis suggested that the expansion was initiated about 276,000 years ago for H. mohnikei and about 230,000 years ago for H. trimaculatus during the middle Pleistocene period. This study indicates a possible signature of genetic variation and population expansion in two seahorses under complex marine environments.

Higher efficiency of CO2 injection into seawater by a venturi than a conventional diffuser system.

Mass production of microalgae generally requires the injection of CO(2) into open ponds or photo-bioreactors. The present study compares the CO(2) injection efficiency into seawater of a porous stone air diffuser and a venturi. CO(2) was injected at flow rates of 400, 700 and 1000 standard mL/min and 4, 7 and 10 standard L/min into a small and a large pond, respectively until the pH decreased from 7.8 to 6.8. No significant differences in CO(2) injection efficiency between the three CO(2) flow rates (p>0.05) were observed; however, CO(2) injection efficiency with venturi was about 100% (p<0.05) higher than that of the air diffuser. Therefore, it is possible to both reduce the cost and increase the effectiveness of CO(2) dissolution in seawater by using venturi operated at a lower flow rate, i.e. 400 standard mL/min in a small pond and 4 standard L/min in a large pond.

Phylogeny and biogeography of Poecilia (Cyprinodontiformes: Poeciliinae) across Central and South America based on mitochondrial and nuclear DNA markers.

Poeciliids are a diverse group of small Neotropical fishes, and despite considerable research attention as models in ecology and evolutionary biology, our understanding of their biogeographic and phylogenetic relationships is still limited. We investigated the phylogenetic relationships of South and Central American Poecilia, by examining 2395 base pairs of mitochondrial DNA (ATPase 8/6, COI) and nuclear DNA (S7) for 18 species across six subgenera. Fifty-eight novel sequences were acquired from newly collected specimens and 20 sequences were obtained from previously published material. Analyses of concatenated and partitioned mitochondrial DNA and nuclear DNA sets resulted in a well-supported phylogeny that resolved several monophyletic groups corresponding to previously hypothesized subgenera and species complexes. A divergence-dating analysis supported the hypothesis of the genus Poecilia dispersing into Central America in the early Pliocene (ancestors of Psychropoecilia+Allopoecilia+Mollienesia: 7.3-2.0Mya) from predominantly South America. Subsequently, one lineage (subgenus Allopoecilia: 5.1-1.3Mya) expanded deeper into South America from Lower-Central America, and one lineage expanded from Nuclear-Central America into South America (subgenus Mollienesia: 0.71-0.14Mya). The subgenus Mollienesia diverged into three monophyletic groups that can be identified by nuptial male dorsal fin morphology and inner jaw dentition. A subclade of the unicuspid short-fins (subgenus Mollienesia) was the lineage that expanded into South America during the middle Pleistocene. Species in this subclade are now distributed across northern South America, where they are partially sympatric with Allopoecilia. However the P. (A.) caucana complex was not monophyletic, with P. (A.) wandae clustering in the Mollienesia subclade that expanded into South America. It is apparent that characters (body size, scale count, pigmentation, and gonopodium morphology) used to define the P. (A.) caucana complex are homoplastic and suggestive of rapid convergence in northern South America. Our improved taxon sampling and divergence-time calibration allowed for insights into the timing and direction of dispersals, and provides an improved understanding of the biogeographic history of an enigmatic group of fishes. Furthermore, we provided strong evidence for the monophyly of the subgenus Mollienesia and further substantiated its species complexes; therefore, we advise a taxonomic re-evaluation for the P. (A.) caucana complex to maintain monophyly of both Mollienesia and Allopoecilia.

Reproductive behavior, embryonic and early larval development of the red head goby, Elacatinus puncticulatus

The goals of this study are to provide a technical foundation for the production of the red head goby Elacatinus puncticulatus by evaluating its reproductive behavior and its embryonic and early larval development. Five pairs were kept under controlled conditions for thirty days. Courtship behavior, spawning period and the number of eggs produced were recorded. For the evaluation of embryo development, eggs were sampled at 12, 18, 24, 48, 72, 96, 120, 144 and 168h post-fertilization(HPF). To test the influence of the incubation period on larval total length and height, eggs with six days (6D) of incubation and with seven days of incubation (7D) were subjected to flashlight illumination for 30min to induce larval hatching. Another experiment evaluated the difference in larval survival with three different diets: Euplotes sp. (EU); rotifers Brachionus rotundiformis and Brachionus plicatilis and Paramecium sp. (BP); plankton collected from the wild (WP). The males displayed a gray head and pale yellow and black body coloration. Females exhibited strong red and black colors until three days before spawning, which occurred at intervals of 7 to 10 days. The hatching rate was 98-99%. The larvae total mean lengths and heights were 3.05 and 2.95mm (p>0.05) and 0.37 and 0.48mm (p<0.05) for treatments 6D and 7D, respectively. However, both groups exhibited high mortality at 5 days post-hatch (DPH). No larvae from the EU group survived after 5 DPH. At 8 DPH, 4% survivorship was found in treatment BP and 2% in treatment WP.

Effect of ultraviolet radiation on photosynthesis, biomass, and fatty acid content and profile of a Scenedesmus rubescens-like microalga

The effects of ultraviolet radiation (UVR) and nitrogen (NaNO(3)) concentration on photosynthesis, biomass, and fatty acid content and profile of a Scenedesmus rubescens-like microalga were measured in an outdoor 8-day culture study. UV-induced photoinhibition decreased from 42.6% to 3.5%, in the presence of 75 mg/L NaNO(3) (HN) and from 52.9% to 22.6% in the presence of 7.5mg/L NaNO(3) (LN) nitrogen concentration, respectively. The concentrations of UV-absorbing compounds increased 4.3 and 4.9 times under HN and LN, respectively. Biomass accumulation was suppressed (10.7%) by UVR under HN, but not under LN conditions. Carotenoid content decreased from 1.05 ± 0.06 to 0.96 ± 0.15 (with UV radiation) and to 0.91 ± 0.07 (without UV radiation), respectively, under HN, while it decreased to 0.05 ± 0.04 (with UV radiation) and to 0.11 ± 0.08 (without UV radiation), respectively, under LN. The content of C18:1n9 fatty acids increased by about 430%, whereas that of C18:3n3 decreased by about 65% in both radiation treatments during nitrogen starvation. The results showed that the absence of UVR screening does not change the fatty acid content and profile of S. rubescens-like algae cultivated outdoors under HN and LN conditions.