The variability in abundance of eugregarines living in the Antarctic krill

The variability in abundance of eugregarines associated with the Antarctic krill Euphausia superba was studied using samples collected from the vicinity of the Antarctic Peninsula. Body length, maturity stage and moult stage with respect to variation in eugregarines infection in krill were examined. Body length was significantly correlated with abundance of eugregarines. The interaction between moult stage and maturity stage was statistically analyzed by ANCOVA with body length as the covariate. The analysis of moult stage did not show a significant effect on abundance of eugregarines while the interaction between maturity stage and body length showed significance. Larger krill have more eugregarines than smaller krill at the same maturity stage. Body length appears to be the most important factor determining the abundance of eugregarines

Lumostatic operation controlled by the optimum light intensity per dry weight for the effective production of Chlorella zofingiensis in the high cell density continuous culture

To maximize the production rate of Chlorella zofingiensis, a lumostatic continuous culture was operated under light intensities of 250–1510 μE m− 2 s− 1. The cell density and volumetric biomass production rate were increased without photo inhibition and reached 13.5 g-dry weight (dw) L− 1 on day 21.5 and 2.41 g-dw L− 1 day− 1 on day 10.5, respectively. These maximum values were higher than any previous photoautotrophic culture study with C. zofingiensis. The specific growth rate was maintained at a high level > 0.5 day− 1 until the light intensity per dry weight decreased below 28 μE g-dw− 1 s− 1, which coincided with the value estimated in our previous study, verifying the reliability of this estimated value. There was a strong relationship between the photosynthetic efficiency and light intensity per dry weight for C. zofingiensis. This relationship may be useful for evaluating species-specific productivity to select productive species

Zooplankton distribution patterns in relation to the Antarctic Polar Front Zones Recorded by Continuous Plankton Recorder (CPR) during 1999/2000 Kaiyo Maru cruise

During the 8th Antarctic Expedition of the R/V Kaiyo Maru of the Japan Fisheries Agency, October 1999 to March 2000,a Continuous Plankton Recorder (CPR) was used to investigate zooplankton composition and abundance in the surface of the Indian sector of Southern Ocean between South Africa and Antarctica. Total zooplankton abundance ranged from 0 to 432 individuals/segment (a 5 nautical miles of the surface towing) (Mean±SD=69.7±83.5). Zooplankton abundance tended to be higher in the high latitudes than the Sub-Antarctic Front (SAF). Opposite correlations were observed between zooplankton and seawater temperature (negative), salinity (positive) and in vivo fluorescence value (positive) reflecting the higher abundance of zooplankton found in the cooler waters south of the SAF, which also have higher salinities and phytoplankton. Among twenty-nine species/taxa identified, cyclopoid copepod Oithona spp. were found throughout the transect, and accounted for 53.3% of total zooplankton abundance. Cluster analysis based on seventeen dominant zooplankton species/taxa revealed two groups and three ungrouped individual species/taxa at the 84% dissimilarity level. On the other hand, the cluster analysis based on the samples obtained in a 5 nautical miles indicated two major distinctive zooplankton community groups at 89% dissimilarity level. The main group included most segments in the Polar Frontal Zone (PFZ : region between SAF and the Polar Front) and Antarctic Zone (AZ : south of the Polar Front) with high zooplankton abundance while the second mainly group comprised lower latitude segment with low abundance (<100 individuals/segment)

Reproductive strategy of Acartia steueri in Sagami Bay, Japan

Reproduction, hatching success and population dynamics of the dominant copepod Acartia steueri were studied in Sagami Bay, Japan from February 2002 to December 2003. A. steueri occurred through the year in the water column, and it produced physiologically different eggs, subitaneous and diapausing. Subitaneous eggs were produced through the experimental period, whereas diapausing ones were restricted from February to August in both years. Population egg production rate (EPR) increased with the abundance of adult males and females from February and reached maximum in June. However, planktonic population of A. steueri did not increase during summer to winter because diapausing eggs occupied a great part of their reproduction (～98%). Recruitment rates in October to December 2002 and September 2003 were higher than population EPR, implying that diapausing eggs of A. steueri had a key role to support the recruitment into water column when the reproductive ability of the population diminished rather than to contribute to an increase of the planktonic population rapidly in their favorable seasons

Effect of temperature on thermophilic composting of aquaculture sludge: NH3 recovery, nitrogen mass balance, and microbial community dynamics

Development of thermophilic composting for maximizing NH3 gas recovery would enable the production of a nitrogen source which is free from pathogen/heavy metal, for the cultivation of high-value microalgae. The present study examined the effect of NH3 recovery, nitrogen mass balance, and microbial community dynamics on thermophilic composting of shrimp aquaculture sludge. The emission of NH3 gas at 60 and 70 °C was 14.7% and 15.6%, respectively, which was higher than that at 50 °C (9.0%). The nitrogen mass balance analysis revealed that higher temperatures enhanced the solubilization of non-dissolved nitrogen and liberation of NH3 gas from the produced NH4+-N. High-throughput microbial community analysis revealed the shift of the dominant bacterial group from Bacillus to Geobacillus with the rise of composting temperature. In conclusion, thermophilic composting of shrimp aquaculture sludge at 60–70 °C was the most favorable condition for enhancing NH3 gas recovery

Seasonal variation of zooplankton community in the coastal waters of the Straits of Malacca

The seasonal and annual variation of zooplankton community was investigated at a fixed station in the coastal waters of the Straits of Malacca. Sampling was carried out monthly by vertical hauls of a 140μm plankton net from June 2002 to May 2004. Zooplankton were identified and grouped into respective taxonomic groups and 23 genera of copepods were identified. Copepods dominated the zooplankton community and among them, the genera Acartia, Acrocalanus, Paracalanus, Euterpina, Corycaeus and Oithona were dominant. They accounted for approximately 90% of the total copepod population throughout the year, emphasizing the importance of small species in tropical zooplankton communities. Zooplankton biomass generally peaked at the beginning of each monsoon and gradually decreased toward the intermonsoon periods. Biomass seemed to increase with increasing ambient chlorophyll-a concentration. Cluster analysis of zooplankton abundance showed two distinct groups relative to the SW and NE monsoons. The population of Acartia pacifica and A. spinicauda, the two most abundant species in the genus Acartia (>90%), showed alternating peaks throughout the year, with A. pacifica appearing primarily during the NE monsoon and A. spinicauda, during the SW monsoon. The presence of the effect of monsoon on zooplankton community in tropical waters is suggested

Estimation of optimum specific light intensity per cell on a high-cell-density continuous culture of Chlorella zofingiensis not limited by nutrients or CO2

To determine the optimum light intensity per cell required for rapid growth regardless of cell density, continuous cultures of the microalga Chlorella zofingiensis were grown with a sufficient supply of nutrients and CO2 and were subjected to different light intensities in the range of 75–1000 μE m−2 s−1. The cell density of culture increased over time for all light conditions except for the early stage of the high light condition of 1000 μE m−2 s−1. The light intensity per cell required for the high specific growth rate of 0.5 day−1 was determined to be 28–45 μE g-ds−1 s−1. The specific growth rate was significantly correlated to light intensity (y = 0.721 × x/(66.98 + x), r2 = 0.85, p < 0.05). A high specific growth rate was maintained over a range of light intensities (250–1000 μE m−2 s−1). This range of light intensities suggested that effective production of C. zofingiensis can be maintained outdoors under strong light by using the optimum specific light intensity

Seasonal changes in abundance of four Acartia species (Copepoda, Calanoida) in the coastal waters of Peninsular Malaysia; relationship with monsoon transition

The seasonal variation of Acartia copepods from the waters of Peninsular Malaysia was studied via monthly observations at 2 fixed stations on the west coast (Pulau Pinang and Port Dickson) and 2 fixed stations on the east coast (Kijal and Penyabong) from October 2012 to March 2014. In situ temperatures recorded during this period were relatively constant (mean 29.6±0.7°C) at all stations. Salinitymeasurements were also fairly constant (mean 30.3 ± 1.1 PSU) for all stations during this study except at Penyabong where the salinity during the northeast (NE) monsoon season was significantly lower (p<0.05) (mean 23.2 ± 7.9 PSU) than during the southwest (SW) monsoon season. Concentration of chlorophyll a at Pulau Pinang during the SW monsoon period was significantly higher (p<0.05) (mean 14.6±5.4μg/L) than during the NE monsoon period. Four species of Acartia were identified at all stations: A. amboinensis, A. erythraea, A. pacifica and A. spinicauda. At Kijal, Acartia erythraeapopulation was significantly higher (p<0.05) (mean 695.7 ± 618.4 inds/m3) compared with the other stations. Acartia species composition at Port Dickson was similar to Penyabong, while Kijal was similar to Pulau Pinang. Small-sized species, Acartia pacifica and A. spinicauda were dominant at Port Dickson and Penyabong, while the larger-sized species, Acartia amboinensis and A. erythraea were dominant at Kijal. Generalized additive mixed models (GAMMs) were applied to abundance data to describe the environmental preference associated with population recruitment of these species, and the results identified a relative contrast in environmental envelopes occupied by the larger and smaller-sized species. The large-sized species preferred colder and more saline water while the small-sized species preferred warmer and lower salinity water. The succession and co-occurrence of similar sized species is suggested to be a result of the combined effect of species-specific preference to varying temperature–salinity regimes

Antioxidant capacity of five microalgae species and their effect on heat shock protein 70 expression in the brine shrimp Artemia

Oxidative stress caused by chemicals brings about mass mortalities in aquatic organisms and in this context, antioxidants and heat shock protein 70 (Hsp70) stimulating compounds represent potential alternatives to alleviate this problem during aquaculture. The antioxidant capacity and efficacies of five Malaysian indigenous microalgae, namely Auxenochlorella pyrenoidosa, Chlorella vulgaris, Messastrum gracile, Desmodesmus subspicatus and Parachlorella kessleri to regulate Hsp70 expression in the brine shrimp Artemia, an important live food species, were examined. A. pyrenoidosa contained the highest total phenol and flavonoid content (48.3 mg GAE/g extract and 34.7 mg QE/g) across all the microalgae examined in this study, whereas the lowest occurred with C. vulgaris (24.4 mg GAE/g extract and 14.0 mg QE/g). The ferric reducing antioxidant power of A. pyrenoidosa, C. vulgaris, M. gracile, D. subspicatus and P. kessleri respectively stood at 0.78, 0.62, 1.01, 0.77 and 0.68 ferrous equivalents (mM), with trolox equivalent antioxidant capacity assay revealed that A. pyrenoidosa possessed the highest scavenging activity at 1 mg/mL concentration. Interestingly, application of 1.0-2.0 x 10(6) cells/mL C. vulgaris, M. gracile, D. subspicatus, and P. kessleri as feed enhanced Hsp70 accumulation in Artemia, indicating that these microalgae consist stimulating compound(s) which potentially promote the synthesis of the 70-kDa stress protein in this crustacean species. Taken together, results from this study revealed that microalgae possess various antioxidant properties and coupled with their abilities to induce Hsp70, they are potential oxidative stress control alternatives in Artemia and perhaps other aquatic organisms used in aquaculture

Treatment of synthetic poultry slaughterhouse wastewater using a consortium of anaerobic digestion microorganisms and purple phototrophic bacteria

As global population increases and living standards improve in developing countries, the demand for meat is increasing, resulting in the rise of highly concentrated organic waste water generated from poultry processing. An effective method for treating this wastewater is through anaerobic digestion, which converts it into biogas as an energy source using anaerobic microorganisms. However, while this process effectively removes organic carbon, nutrients suchas nitrogen and phosphorus remain in high concentrations in the effluent, necessitating second ary treatment facilities such as separate nitrification and denitrification tanks. Purple phototro phic bacteria are microorganisms that can uptake organic matter and nutrient-rich pollutants in wastewater, accumulating protein and carbohydrate in their cells. Since both anaerobic digestion and purple phototrophic bacterial processes occur under anaerobic conditions and have similar suitable environments such as pH and temperature, they can potentially be integrated into a single reactor. This study proposes a new process using a consortium of anaerobic digestion microorganisms and purple phototrophic bacteria for simultaneous treatment of organic carbon and nutrients from poultry slaughterhouse wastewater. The performance of the proposed simul taneous process was compared with that of the only-anaerobic digestion process and only-purple phototrophic bacterial process in a 19-day batch e periment at 33 ± 2oC under anaerobic conditions. Synthetic poultry slaughterhouse wastewater was used as the substrate, and anaerobic digestion sludge collected from a mesophilic anaerobic digestion plant and Rhodopseudomonas capsulata were used as the inoculums.In the simultaneous process, biogas production and organic carbon (chemical o ygen demand) removal progressed first with and without infrared light irradiation, followed by an increase in bacteriochlorophyll a concentration, an indicator of the biomass of purple phototrophic bacte ria. These results indicate that the anaerobic digestion process and purple phototrophic bacterial process functioned in a single reactor, although there was a time gap between the two processes. Despite uniform substrate input, the simultaneous process produced higher biogas (276-337 mL) than the only-anaerobic digestion process (138 mL), possibly due to degradation of some purple phototrophic bacteria biomass as feedstock for anaerobic digestion. In the simultaneous process, organic carbon removal efficiencies ranged from 40 to 81%, similar to or lower than the removal efficiency of the only-anaerobic digestion process (81%). In purple phototrophic bacteria added conditions, nitrogen removal was not confirmed, indicating low nutrient removal capability. The treatment performance of the simultaneous process can be enhanced by improving light permea bility using flat-panel reactors or granular anaerobic sludge and acclimation of purple phototro phic bacteria with highly concentrated organic wastewater before using it as an inoculum.departmental bulletin pape