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William T. Peterson - One of the best experts on this subject based on the ideXlab platform.
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Comparison of condition metrics and lipid content between Euphausia Pacifica and Thysanoessa spinifera in the northern California Current, USA
Progress in Oceanography, 2020Co-Authors: Jennifer L. Fisher, Leah R. Feinberg, C. Tracy Shaw, Jennifer Menkel, Louise A. Copeman, William T. PetersonAbstract:Abstract Krill are a key component of pelagic food webs where they are vital to the transfer of energy from phytoplankton to higher trophic levels. Krill have a high lipid content compared to other zooplankton and form dense aggregations, making them an important prey source for higher trophic level fish, seabirds, and marine mammals. The two dominant euphausiid species in the northern California Current (NCC) are Euphausia Pacifica and Thysanoessa spinifera. E. Pacifica is the most abundant species of euphausiid in the NCC, but T. spinifera has a higher potential energetic content due to its larger body size and higher lipid density. Most studies have inferred differences in lipid content and body condition between the two species, but few studies have quantified these differences in the NCC. Here, we report on the body condition, carbon and nitrogen content, as well as lipid and fatty acid composition of these two krill species, and the extent to which these metrics vary across season, year, and reproductive status. Body condition, elemental composition, and total lipids strongly differed between the species. T. spinifera had higher length-weight, Fulton’s K, hepato-somatic index, carbon to nitrogen ratio, total lipid per wet weight, and storage lipid compared to E. Pacifica, indicating that T. spinifera has a higher energetic value for predators. However, there were strong seasonal differences in the energetics of T. spinifera. Carbon and lipids were highest in non-reproductive T. spinifera from August through October. Although there were strong ontogenetic and inter-specific differences, the lipid and fatty acid compositions of both species followed a seasonal progression characterized by low lipids during the pre-upwelling period, an increase in lipids, triacylglycerols, and diatom markers during upwelling, and increased proportions of dinoflagellate and bacterial diet markers during the fall post-upwelling period.
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feeding rates and selectivity of adult Euphausia Pacifica on natural particle assemblages in the coastal upwelling zone off oregon usa 2010
Journal of Plankton Research, 2014Co-Authors: Xiuning Du, William T. PetersonAbstract:Filtration by adult Euphausia Pacifica was measured before and during the upwelling season, using both “disappearance of chlorophyll” and “disappearance of cells” techniques. Results show that feeding rates and selectivity varied with food assemblages. Filtration rate (F) was best modeled by the Ivlev function: the average F on total Chl-a was 92 mL euphausiid h, and 119 mL euphausiid h on microscopy cell counts. F averaged 36 for the ,5 mm size fraction of Chl-a, 94 for the 5–20 mm fraction and 107 mL euphausiid h for the .20 mm fraction. The average F values were 155 and 163 mL euphausiid h for chain-diatoms and single diatoms, respectively, and115 and 137 mL euphausiid h for the ,40 mm and .40 mm ciliates, respectively. Ingestion rates based on total Chl-a and size fractions, total cell counts and ciliates were significantly correlated using Hollings’ models (P , 0.01). Maximum daily ration was 23% body C day when a high food concentration (700 mC L) was available, but over the carbon range of 50–200 mg C L, daily ration averaged 4% body C day. Diatoms were consumed almost exclusively during blooms associated with summer upwelling events; larger types of ciliates and dinoflagellates were fed upon preferentially compared with their smaller counterparts.
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Euphausia Pacifica brood sizes: a North Pacific synthesis
Journal of Plankton Research, 2013Co-Authors: Leah R. Feinberg, William T. Peterson, C. T. Shaw, Moira Décima, Y. Okazaki, S.-j. JuAbstract:Euphausia Pacifica occupy a remarkably wide range of ecosystems. We examined the differences in brood sizes from eight regions of the North Pacific to explore how variation in the brood size might contribute to their success over such a range. We show a compilation and analysis of short-term E. Pacifica brood size incubations from around the North Pacific rim, ranging from the Yellow Sea (YS) (Korea) to southern California (SC), USA. Brood sizes for E. Pacifica are highly variable in all regions and range from 5 to 697 eggs overall. Median brood sizes were largest in the YS and off Newport, Oregon and the maximum brood sizes were greatest in the regions off the coasts of Oregon and Washington, USA followed by the YS. Quantile regression analysis revealed that there was a significant relationship between the female length and the maximum brood size (95% quantile) for broods from SC, Oregon, and Washington, USA as well as Toyama Bay, Japan, indicating that the maximum brood size is limited by the female length in these regions. This suggests that other factors, hydrographic conditions, food quantity/quality or physiological condition of females, may limit maximum brood sizes in the other regions examined here.
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The mitochondrial genomes of Euphausia Pacifica and Thysanoessa raschii sequenced using 454 next-generation sequencing, with a phylogenetic analysis of their position in the Malacostracan family tree
Molecular Biology Reports, 2012Co-Authors: Mattias L. Johansson, Leah R. Feinberg, Angela L. Sremba, Michael A. Banks, William T. PetersonAbstract:Euphausiid krill play a critical role in coastal and oceanic food webs, linking primary producers to upper trophic levels. In addition, some species support commercial fisheries worldwide. Despite their ecological importance, the genetics of these important species remain poorly described. To improve our understanding of the genetics of these ecological links, we sequenced the mitochondrial genomes of two species of North Pacific krill, Euphausia Pacifica and Thysanoessa raschii, using long-range PCR and 454 GS Junior next-generation sequencing technology. The E. Pacifica mitogenome (14,692 + base pairs (bp)) encodes 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and at least 22 transfer RNA (tRNA) genes. The T. raschii mitogenome (14,240 + bp) encodes 13 PCGs, two rRNA genes, and at least 19 tRNA genes. The gene order in both species is similar to that of E. superba. Comparisons between Bering Sea and Yellow Sea E. Pacifica revealed a total of 644 variable sites. The most variable protein-coding gene were atp8 (7.55 %, 12 of 159 sites variable), nad4 (6.35 %, 85 variable sites) and nad6 (6.32 %, 33 variable sites). Phylogenetic analyses to assess the phylogenetic position of the Euphausiacea, using the concatenated nucleic acid sequences of E. Pacifica and T. raschii along with 46 previously published malacostracan mitogenomes, support the monophyly of the order Decapoda and indicate that the Euphausiacea share a common ancestor with the Decapoda. Future research should utilize this sequence data to explore the population genetics and molecular ecology of these species.
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Growth of Euphausia Pacifica in the upwelling zone off the Oregon coast
Deep-sea Research Part Ii-topical Studies in Oceanography, 2009Co-Authors: C. Tracy Shaw, William T. Peterson, Leah R. FeinbergAbstract:Abstract Growth rates and intermolt periods for Euphausia Pacifica were determined from individual growth rate (IGR) experiments carried out over a 7-year period (2000–2006) on euphausiids collected off the Oregon Coast. Adult growth rates averaged 0.020 mm total length (TL) day−1 during the summer upwelling season and 0.011 mm TL day−1during the winter downwelling season. Average intermolt period (IMP) was 8 d during upwelling and 11 d during downwelling. Growth rates and IMPs were highly variable, and were not related to surface chl-a concentration or length of the euphausiid. Negative growth occurred at all times of year. Negative growth rates during winter downwelling were most likely related to poor feeding conditions, while negative growth rates during the summer upwelling season were likely a result of the euphausiids investing ingested energy towards reproduction rather than somatic growth. Growth rates from this study using the IGR method were generally lower than E. Pacifica growth rates from other studies that used the cohort analysis method. Since negative growth rates are difficult to capture using cohort analysis, we calculated a seasonal growth rate using only the positive values from our experiments to compare with cohort analysis growth rates. These seasonal positive growth rates were 0.08 mm TL d−1 (2.4 mm month−1) for the upwelling season and 0.04 mm TL d−1 (1.2 mm month−1) for the downwelling season, equivalent to weight-specific growth rates of 0.0135 d−1 (upwelling) and 0.0089 d−1 (downwelling), and are comparable to rates obtained in other studies using cohort analysis. Highest annual growth rates during upwelling were measured in 2004 (warm) and 2006 (cold), suggesting that E. Pacifica is less affected by warm and cool periods than other types of zooplankton, such as copepods.
Huilian Liu - One of the best experts on this subject based on the ideXlab platform.
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spatial distribution and population structure of Euphausia Pacifica in the yellow sea 2006 2007
Journal of Plankton Research, 2011Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
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Spatial distribution and population structure of Euphausia Pacifica in the Yellow Sea (2006–2007)
Journal of Plankton Research, 2010Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
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Diel vertical distribution and migration of a euphausiid Euphausia Pacifica in the Southern Yellow Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2009Co-Authors: Huilian Liu, Song SunAbstract:Stage-specific differences in the diel vertical distribution and migration of a euphausiid, Euphausia Pacifica, were studied at a single station (E2,70 m water depth) in the South Yellow Sea, by sampling with a conical closing net from five discrete strata, every 3 h, for 24 h, on 2-3 May 2001. Environmental data were collected simultaneously with the net sampling. Results showed that eggs contributed a large proportion of the numerical abundance of the Euphausia Pacifica population throughout the investigation. They were mainly distributed below 20 m depth, and concentrated in the 30-50 m strata throughout the day and night. Nauplius stage I (NI) was distributed below 10 m, and seldom occurred in the upper 10 m. Nauplius stage II (NII) and Metanauplius stage (MN) extended their distribution to nearly the whole water column; however, the MN resided somewhat shallower than NIL The majority of calyptopis stages I to III (CI to CIII) and early furcilia stages I to III (FI to FIII) were restricted to the upper 30 m throughout the day. The weighted mean depth tended to increase as the stage progressed from stage FI onward. Calyptopis stages showed a weak or moderate diel vertical migration behavior, and the onset of an obvious diel vertical migration took place in FII stage. The amplitude of the diel vertical migration varied with developmental stages. Stages after FIV were often absent from samples during the investigation, but from the limited available data, DVM occurred from stages FIV-VI and female adults. However, the male adults showed a somewhat different migration behavior. In summary, an ontogenetic migration pattern is obvious from this high-frequency sampling: spawning took place at 20-50 m depth, hatched nauplii sank a little, metanauplius began moving toward the surface, and calyptopis larvae reached the uppermost layer. Furcilia larvae began DVM and deepened their daytime residence depth with age. The vertical distribution of Euphausia Pacifica seemed to relate to temperature and chlorophyll a. (C) 2009 Elsevier Ltd. All rights reserved.
Song Sun - One of the best experts on this subject based on the ideXlab platform.
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Grazing and metabolism of Euphausia Pacifica in the Yellow Sea.
PLOS ONE, 2015Co-Authors: Zhencheng Tao, Song SunAbstract:Grazing and metabolism of Euphausia Pacifica in the Yellow Sea were studied from September 2006 to August 2007. Euphausia Pacifica is a selective-feeding omnivore and grazing rates among different months were monitored using a Coulter Counter and batch culture feeding experiments. Euphausia Pacifica mainly grazed microzooplankton in August and September, which resulted in an increase in chlorophyll a concentration. Oxygen consumption rate of E. Pacifica was 38.7–42.5 μmol O2 g-1 DW h-1 in March, which was four times higher than the oxygen consumption rates in September and December. The vigorous metabolism of E. Pacifica in March consumed 3.1% of body carbon daily, which is likely related to its high reproduction and grazing rate. Respiration and metabolism of E. Pacifica in September and December were similar and were lower. O:N ratio of E. Pacifica was the highest (17.3–23.8) in March when spawning activity occurred and when food was abundant. The energetic source of E. Pacifica during September and December was mostly protein from eating a carnivorous diet, including such items as microzooplankton. Euphausia Pacifica was found in cold water at the bottom of the Yellow Sea in summer and autumn and maintained a low consumption status. O:N ratios of E. Pacifica in March, September, and December were negatively correlated with SSTs and no significant correlation was found between O:N ratios and chlorophyll a concentration. Seawater temperature is clearly the most important parameter influencing the metabolism of E. Pacifica.
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spatial distribution and population structure of Euphausia Pacifica in the yellow sea 2006 2007
Journal of Plankton Research, 2011Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
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Spatial distribution and population structure of Euphausia Pacifica in the Yellow Sea (2006–2007)
Journal of Plankton Research, 2010Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
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Diel vertical distribution and migration of a euphausiid Euphausia Pacifica in the Southern Yellow Sea
Deep-sea Research Part Ii-topical Studies in Oceanography, 2009Co-Authors: Huilian Liu, Song SunAbstract:Stage-specific differences in the diel vertical distribution and migration of a euphausiid, Euphausia Pacifica, were studied at a single station (E2,70 m water depth) in the South Yellow Sea, by sampling with a conical closing net from five discrete strata, every 3 h, for 24 h, on 2-3 May 2001. Environmental data were collected simultaneously with the net sampling. Results showed that eggs contributed a large proportion of the numerical abundance of the Euphausia Pacifica population throughout the investigation. They were mainly distributed below 20 m depth, and concentrated in the 30-50 m strata throughout the day and night. Nauplius stage I (NI) was distributed below 10 m, and seldom occurred in the upper 10 m. Nauplius stage II (NII) and Metanauplius stage (MN) extended their distribution to nearly the whole water column; however, the MN resided somewhat shallower than NIL The majority of calyptopis stages I to III (CI to CIII) and early furcilia stages I to III (FI to FIII) were restricted to the upper 30 m throughout the day. The weighted mean depth tended to increase as the stage progressed from stage FI onward. Calyptopis stages showed a weak or moderate diel vertical migration behavior, and the onset of an obvious diel vertical migration took place in FII stage. The amplitude of the diel vertical migration varied with developmental stages. Stages after FIV were often absent from samples during the investigation, but from the limited available data, DVM occurred from stages FIV-VI and female adults. However, the male adults showed a somewhat different migration behavior. In summary, an ontogenetic migration pattern is obvious from this high-frequency sampling: spawning took place at 20-50 m depth, hatched nauplii sank a little, metanauplius began moving toward the surface, and calyptopis larvae reached the uppermost layer. Furcilia larvae began DVM and deepened their daytime residence depth with age. The vertical distribution of Euphausia Pacifica seemed to relate to temperature and chlorophyll a. (C) 2009 Elsevier Ltd. All rights reserved.
Tsutomu Ikeda - One of the best experts on this subject based on the ideXlab platform.
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Population dynamics of the euphausiids Euphausia Pacifica and Thysanoessa inspinata in the Oyashio region during the 2007 spring phytoplankton bloom
Deep-sea Research Part Ii-topical Studies in Oceanography, 2010Co-Authors: Hye Seon Kim, Atsushi Yamaguchi, Tsutomu IkedaAbstract:The abundance and population structure of Euphausia Pacifica and Thysanoessa inspinata were investigated during the period 9 March–29 April 2007 at a single station in the Oyashio region. Water temperature and chlorophyll a concentration varied from 1.1 to 6.1 1C and from 0.02 to 6.3 mg m � 3 , respectively, primarily reflecting the effects of varying mixtures of the water masses prevailing in this region. The abundance of euphausiids, collected by oblique hauls with Bongo nets (0–200 m) at night, fluctuated from 41 to 1040 individuals m � 2 for E. Pacifica and from 50 to 186 individuals m � 2 for T. inspinata. Correlation analyses revealed that the variations in the abundance of E. Pacifica were related to water temperature and chlorophyll a, while abundance of T. inspinata only varied with temperature. Adult males and females (with and without spermatophores) were the major components of both euphausiid stocks (4 90% of the total). Modal size (¼total length or TL) analysis revealed that one group with large sizes (14–18 mm TL for E. Pacifica, 16–18 mm TL for T. inspinata) occurred throughout the study period, often accompanied by one discrete group of smaller individuals (o 11 mm TL for both euphausiids), suggesting the distribution of the same euphausiid populations across the heterogeneous water masses. Adult males were significantly smaller than adult females in T. inspinata, but this was not the case in E. Pacifica. Tracing the progressive increase in the mean sizes of the larger size groups, growth rates were estimated to be 0.082 mm day � 1 for E. Pacifica and 0.022 mm day � 1 for T. inspinata. The difference in the growth rates of the two euphausiids is discussed in light of species-specific differences in the allocation of energy to reproduction and somatic growth during the present study period.
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Metabolism and elemental composition of the euphausiids Euphausia Pacifica and Thysanoessa inspinata during the phytoplankton bloom season in the Oyashio region, western subarctic Pacific Ocean
Deep-sea Research Part Ii-topical Studies in Oceanography, 2010Co-Authors: Hye Seon Kim, Atsushi Yamaguchi, Tsutomu IkedaAbstract:Rates of oxygen consumption (R: m lO 2 [individual] � 1 h � 1 ), and ammonia excretion (E: m gN H 4-N [individual] � 1 h � 1 ), O:N ratios (by atoms) and body water contents (% of wet mass [WM], as an index of lipid accumulation) of Euphausia Pacifica and Thysanoessa inspinata were monitored during 9–14 March and 6–30 April 2007, including the onset of the spring phytoplankton bloom in the Oyashio region. Regression analyses revealed that variations in R and E were generally correlated with dry body mass (DM) for both euphausiids. When R and E were standardized to a body size of 10 mg DM, Rstd, Estd, O:N ratios and water contents fluctuated from 6.3 to 10.1, 0.07 to 0.34, 31 to 232 and 73.8 to 78.1, respectively, for E. Pacifica, and from 8.7 to 11.3, 0.06 to 0.71, 24 to 295 and 75.1 to 82.2, respectively, for T. inspinata. None of these variables were significantly correlated with temporal variations in SST (1.7 to 5.7 1C) or chlorophyll a standing stock (29.4 to 252.6 mg m � 2 , 0–100 m) at the study site. However, April E and O:N ratio data pooled for both euphausiids were significantly less and greater, respectively, than the pooled values in March, suggesting preferential utilization of dietary protein for body growth or reproduction under conditions of abundant food supply as found in April. No substantial differences were observed in water content, ash, C, N or C:N ratios (by mass) of the two euphausiids collected in either March or April. Water content, C, N, C:N ratio and ash data averaged for E. Pacifica and T. inspinata over the March and April cruises were similar: 76.3 and 78.1% of WM, 36.1 and 37.5% of DW, 9.4 and 10.1% of DW, 3.82 and 3.71 by mass, and 10.6 and 10.8% of DM, respectively. Combining the R-DM and E-DM relationships established with the population structure data of Kim et al. (2010), we estimate that daily ingestion and ammonia-N regeneration by the combined populations of the two euphausiids were 1.5–24.1% (integrated mean: 4.9%) and 0.18–1.32% (0.41%), respectively, of primary production and associated N demand during the bloom.
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Abundance, biomass and life cycle patterns of euphausiids (Euphausia Pacifica, Thysanoessa inspinata and T. longipes) in the Oyashio region, western subarctic Pacific
Plankton and Benthos Research, 2009Co-Authors: Hye Seon Kim, Atsushi Yamaguchi, Tsutomu IkedaAbstract:A series of oblique hauls with Bongo nets (0-1000 m) was made during the period of August 2002 through August 2004 in the Oyashio region, western subarctic Pacific, to investigate abundance, biomass and life cycle patterns of the three predominant euphausiids (Euphausia Pacifica, Thysanoessa inspinata and T. longipes). While the three euphausiids occurred throughout the entire study period, E. Pacifica was the most abundant (1,120 indiv. m � 2 , or 832 mg C m � 2 ), followed by T. inspinata (163 indiv. m � 2 , or 144 mg C m � 2 ) and T. longipes (73 indiv. m � 2 , or 75 m gCm � 2 ). Judging from the occurrence of females with spermatophores and furcilia larvae, the spawning was consid- ered to take place twice a year (April-May and August) for E. Pacifica, year-round (peak season: March-May) for T. inspinata and in spring (March-May) for T. longipes. The population structure in terms of size (� total length) fre- quency distributions of the three euphausiids was characterized by the frequent co-occurrence of 2-3 cohorts in the same samples. The maximum size of males and females found were 21 mm and 24 mm, respectively, for E. Pacifica, 18 mm and 23 mm, respectively, for T. inspinata, 27 mm and 31 mm, respectively, for T. longipes. Tracing the sequence of cohorts, the life spans of E. Pacifica, T. inspinata and T. longipes were estimated to be 17-26 months, 17-19 months and 29-31 months, respectively. These results are compared with reports of the same species in other habitats in the light of regional variations.
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of lowered pH to some oceanic zooplankton
1999Co-Authors: Yuichiro Yamada, Tsutomu IkedaAbstract:Acute toxicity of lowered pH (s4) was tested on 10 oceanic zooplankton species, including Conchoecia sp., Calanus pacificus, Neocalanus cristatus, Eucalanus bungii bungii, Pseudocalanus minutus, Metridia Pacifica, Paraeuchaeta elongata, Themisto japonica, Euphausia Pacifica (nauplii and juveniles) and Sagitta elegans. As indices of pH sensitivity in the zooplankton, the pH levels caus ing 50% mortality (LC50) and zero mortality (LC0) were estimated from the mortality-log10( pH) rela
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Growth, metabolism and growth efficiency of a euphausiid crustacean Euphausia Pacifica in the southern Japan Sea, as influenced by temperature
Journal of Plankton Research, 1995Co-Authors: Naoki Iguchi, Tsutomu IkedaAbstract:Growth (assessed from intermolt period and molt increment) and metabolism (oxygen con- sumption) of the post-larva of Euphausia Pacifica from the southern Japan Sea were determined at seven graded temperatures ranging from 1 to 25°C. The intermolt period shortened progressively as temperature increased from 1 to 20°C, but an effect of temperature on molt-to-molt growth increment was not seen. Oxygen consumption rates were accelerated by the increase in temperature up to 20°C. Beyond 20°C, E.Pacifica exhibited reduced oxygen consumption and died within 1 day without molting. After removing the effect of body size, the relationships between growth rate and temperature, and between oxygen consumption rate and temperature, were established. The carbon budget was calcu- lated as a function of temperature. Because of differential effects of temperature on growth and metab- olism, the net growth efficiency (K{. growth x 100/(growth + metabolism)) changed with temperature. The optimum temperature at which E.Pacifica attained the maximum K2 was 11.4°C, which was derived from calculation of cumulative carbon invested in growth and metabolism in this animal. In an alterna- tive method, the optimum temperature was obtained mathematically by solving a set of differential equations. The biological and ecological significance of the optimum temperature which leads to the
Zhencheng Tao - One of the best experts on this subject based on the ideXlab platform.
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Grazing and metabolism of Euphausia Pacifica in the Yellow Sea.
PLOS ONE, 2015Co-Authors: Zhencheng Tao, Song SunAbstract:Grazing and metabolism of Euphausia Pacifica in the Yellow Sea were studied from September 2006 to August 2007. Euphausia Pacifica is a selective-feeding omnivore and grazing rates among different months were monitored using a Coulter Counter and batch culture feeding experiments. Euphausia Pacifica mainly grazed microzooplankton in August and September, which resulted in an increase in chlorophyll a concentration. Oxygen consumption rate of E. Pacifica was 38.7–42.5 μmol O2 g-1 DW h-1 in March, which was four times higher than the oxygen consumption rates in September and December. The vigorous metabolism of E. Pacifica in March consumed 3.1% of body carbon daily, which is likely related to its high reproduction and grazing rate. Respiration and metabolism of E. Pacifica in September and December were similar and were lower. O:N ratio of E. Pacifica was the highest (17.3–23.8) in March when spawning activity occurred and when food was abundant. The energetic source of E. Pacifica during September and December was mostly protein from eating a carnivorous diet, including such items as microzooplankton. Euphausia Pacifica was found in cold water at the bottom of the Yellow Sea in summer and autumn and maintained a low consumption status. O:N ratios of E. Pacifica in March, September, and December were negatively correlated with SSTs and no significant correlation was found between O:N ratios and chlorophyll a concentration. Seawater temperature is clearly the most important parameter influencing the metabolism of E. Pacifica.
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spatial distribution and population structure of Euphausia Pacifica in the yellow sea 2006 2007
Journal of Plankton Research, 2011Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
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Spatial distribution and population structure of Euphausia Pacifica in the Yellow Sea (2006–2007)
Journal of Plankton Research, 2010Co-Authors: Song Sun, Zhencheng Tao, Huilian LiuAbstract:We studied spatial distribution patterns, population structure and egg production rates of Euphausia Pacifica in the Yellow Sea from April 2006 to August 2007 during eight cruises. We investigated the distribution of the developmental stages in relation to environmental factors (temperature, salinity and chlorophyll a). We used principal components analysis and Pearson's correlation to analyze the covariation and correlation between E. Pacifica abundances and environmental factors. The spatial distribution of E. Pacifica was controlled primarily by seawater temperature and the adults preferentially inhabited cold water. Euphausia Pacifica occurred nearly throughout the entire study area in spring and winter. When surface seawater temperature was over 20 degrees C in summer and autumn, E. Pacifica was mainly located in the Yellow Sea Bottom Cold Water (YSBCW) area where the temperature below the thermocline was 8-10 degrees C. On-board incubation experiments showed that the brood size of E. Pacifica was highest in spring. We conclude that E. Pacifica can undergo its whole life history and maintain high abundance in the Yellow Sea. Recruitment is mainly in spring, after which it is very low. In summer and autumn, the population is mainly distributed in the YSBCW, which offers animals a refuge from warm surface waters.
