Seasonal Cycle of Zooplankton off Southwestern British Columbia: 1979–89

1992 ◽  
Vol 49 (5) ◽  
pp. 903-921 ◽  
Author(s):  
David L. Mackas
Keyword(s):  
British Columbia ◽  
Species Composition ◽  
Continental Shelf ◽  
Late Summer ◽  
Dry Weight ◽  
Zooplankton Biomass ◽  
Late Spring ◽  
Washout Rate ◽  
Upwelled Water ◽  
Population Turnover

Average seasonal cycles of zooplankton biomass, species composition, and environmental conditions are estimated from 1979–89 samples collected off the southwest coast of British Columbia. Average total dry weight biomass ranges from a winter minimum <1.5 g/m2 to a late spring maximum >8 g/m2. Three subregions within the study area can be distinguished based on bathymetry and current pattern: the inner shelf banks, the shelf break and slope, and a gyre off the mouth of Juan de Fuca Strait. Total zooplankton biomass, species composition, and seasonality differ sharply between subregions, as do temperature, salinity, and nutrient and phytoplankton distributions. From spring through autumn, there are large inputs of upwelled water (and nutrients) to the continental shelf. Phytoplankton biomass is high, especially in mid- to late summer, and is ample to support growth of herbivorous zooplankton. Despite high food availability and relatively low predation pressure, surface layer zooplankton populations decline on the continental shelf from late spring through autumn, while offshore zooplankton populations increase slowly. A high washout rate due to upwelling and subsequent seaward and alongshore transport is the most plausible explanation. For the continental shelf in summer, the advective component of population turnover is probably larger than local predation mortality.

Periphyton biomass and species composition in 21 British Columbia lakes: seasonal abundance and response to whole-lake nutrient additions

1984 ◽  
Vol 62 (5) ◽  
pp. 1022-1031 ◽  
Author(s):  
K. S. Shortreed ◽  
A. C. Costella ◽  
J. G. Stockner
Keyword(s):  
British Columbia ◽  
Species Composition ◽  
Dry Weight ◽  
Artificial Substrates ◽  
Seasonal Abundance ◽  
Dominant Group ◽  
Nitrogen And Phosphorus ◽  
Biomass Ash ◽  
Annual Carbon ◽  
Periphyton Biomass

Periphyton communities on artificial substrates in 21 oligotrophic British Columbia lakes were sampled from 1978 to 1980. Periphyton biomass (ash-free dry weight (AFDW) and total chlorophyll (Chl)) and accumulation rates (milligrams AFDW per square metre per day) were among the lowest recorded from temperate oligotrophic lakes, averaging from 0.01 to 5.69 mg Chl∙m−2, 0.04 to 2.86 g AFDW∙m−2, and 1 to 47 mg AFDW∙m−2∙day−1. Diatoms were the dominant group in most lakes at most times, comprising over 70% of total periphyton biomass. Achnanthes minutissima and Tabellaria flocculosa were the most ubiquitous species in the study, and Eunotia spp. were common only in acidic humic-stained lakes. Of the physical and chemical factors measured in this study, pH appeared to be most important in regulating diatom species composition. In those lakes fertilized with nitrogen and phosphorus, periphyton biomass showed marked increases over untreated years, but the community species composition in most lakes remained similar between treated and untreated years. Comparisons between artificial and natural substrates showed that the same species were common on both substrates, although relative abundances varied. The littoral zone of most study lakes is small relative to the pelagic, and it is estimated that periphyton comprised < 1% of average total algal biomass (as chlorophyll) and also represented < 1% of estimated total annual carbon metabolism.

scholarly journals Forage and grain yield of common buckwheat in Mediterranean conditions: response to sowing time and irrigation

2016 ◽  
Vol 67 (9) ◽  
pp. 1000 ◽  
Author(s):  
Marco Mariotti ◽  
Alessandro Masoni ◽  
Iduna Arduini
Keyword(s):  
Grain Yield ◽  
Late Summer ◽  
Dry Weight ◽  
Early Spring ◽  
Late Spring ◽  
Forage Yield ◽  
Forage Production ◽  
Degree Days ◽  
Sowing Time ◽  
Ripening Stages

With the view to extending the cultivation of common buckwheat to Mediterranean environments, we investigated the responses of two varieties to three sowing times, early spring, late spring and late summer, in rainfed and irrigated conditions. Plants were harvested at two ripening stages for forage production and at maturity for grain yield. The crop cycle lasted 82–88 days independent of sowing time, whereas the thermal time was ~1000 degree-days in early spring and late summer sowings, and 1200 degree-days when sown in late spring. Forage yield increased up to 75% between ripening stages. Early spring was the best sowing time for forage (4 t ha–1 dry weight) and grain yield (2 t ha–1 dry weight) in rainfed conditions. Late spring sowings give the highest forage yield when irrigated (6 t ha–1 dry weight), but were not suitable for producing grain, for the adverse effect of high summer temperatures on seed set and seed filling. Late summer sowings produced acceptable grain yield (1.5 t ha–1 dry weight), whereas short days and low temperatures limited forage production. Thus, in Mediterranean environments, buckwheat could be profitably introduced as a minor summer crop, sown in early spring for grain production and in late spring for forage production.

Autumnal nutrient transfers by retranslocation, leaching, and litter fall in a chestnut oak forest in southern Illinois

1982 ◽  
Vol 12 (1) ◽  
pp. 40-51 ◽  
Author(s):  
Nancy L. Ostman ◽  
George T. Weaver
Keyword(s):  
Late Summer ◽  
Dry Weight ◽  
Litter Fall ◽  
Leaf Color ◽  
Southern Illinois ◽  
Foliar Concentrations ◽  
Important Means ◽  
Study Sites ◽  
Free Falling ◽  
Leaf Dry Weight

Retranslocation from leaves was investigated as a means of retaining nutrients in stands of Quercusprinus L. on two sites in southern Illinois, where wind rapidly moves litter downslope. Foliage samples were collected from late summer until leaf fall to describe the trends of leaf dry weight and nutrient concentration (N, K, P, Ca) changes. Free-falling rain and throughfall were collected to estimate foliar leaching. Foliar concentrations of N, K, and P decreased markedly during senescence while Ca concentrations increased. The pattern of concentration change was unique for each element, and the change in N concentration was closely correlated with change in leaf color. For the study sites as a whole, leaf dry weight decreased to 70% of the original value. Of 84.2 kg N/ha in green foliage, only 22.6% was returned to the site as litter. The canopy gained 0.3 kg N/ha (0.4%) from rainfall. The 78.5% N unaccounted for is attributed to retranslocation. Similarly, from 51.4 kg K/ha; 8.2, P; and 47.8, Ca in green foliage, 9.8, 1.3, and 3.3%, respectively, were removed by leaching; 27.4, 43.7, and 85.1% were returned to the site in litter. The remaining 63.0% K, 55.0% P, and 11.5% Ca unaccounted for is attributed to retranslocation. Retranslocation and leaching of nutrients was greater on the site of higher quality. But on both sites it appears that retranslocation is an important means of retaining and conserving N, K, and P countering the effect of annual litter removal.

A mammoth (Mammuthus primigenius) tooth from late Wisconsin deposits near Embden, North Dakota, and comments on the distribution of woolly mammoths south of the Wisconsin ice sheets

1986 ◽  
Vol 23 (7) ◽  
pp. 909-918 ◽  
Author(s):  
C. R. Harington ◽  
Allan C. Ashworth
Keyword(s):  
British Columbia ◽  
Continental Shelf ◽  
North Dakota ◽  
Third Molar ◽  
Ice Sheets ◽  
Lake Agassiz ◽  
Mammuthus Primigenius ◽  
Sand And Gravel ◽  
Woolly Mammoth ◽  
Cass County

A well-preserved third molar of a woolly mammoth (Mammuthus primigenius) was recovered from sand and gravel forming the highest (Herman) prominent strandline of Lake Agassiz near Embden in western Cass County, North Dakota. The Herman strandline is estimated to have formed about 11 500 years BP, and presumably the tooth is of similar age. Perhaps the animal lived in a tundra-like area near the Lake Agassiz shoreline.Additional evidence suggests that woolly mammoths occupied a tundra-like range south of the Wisconsin ice sheets extending from southern British Columbia to the Atlantic continental shelf off Virginia.

scholarly journals Influence of net-cage fish farming on zooplankton biomass in the Itá reservoir, SC, Brazil

2012 ◽  
Vol 23 (4) ◽  
pp. 357-367 ◽  
Author(s):  
Bruna Roque Loureiro ◽  
Christina Wyss Castelo Branco ◽  
Evoy Zaniboni Filho
Keyword(s):  
Fish Farming ◽  
Dry Weight ◽  
Control Area ◽  
Zooplankton Biomass ◽  
Total Density ◽  
Total Zooplankton ◽  
Net Cage ◽  
Uruguay River ◽  
Cage Fish ◽  
Total Zooplankton Biomass

OBJECTIVES: This study aimed to verify the influence of net-cage fish farming on zooplankton biomass in the Itá reservoir (Uruguay River, Brazil). METHODS: Samples were collected monthly from October/2009 to May/2010 at the surface and at the bottom in two sampling stations, the net-cage area and in a control area using a Van Dorn bottle and a plankton net (68 µm). RESULTS: The Cladocera and Copepoda biomass was estimated by dry weight using a micro-analytical balance, and the Rotifera biomass by Biovolume. Total zooplankton biomass varied between 6.47 and 131.56 mgDW.m-3 Calanoida copepod presented the highest value of biomass (127.56 mgDW.m-3) and rotifers, despite having an important contribution to total density, showed a maximum biomass of 2.01 mgDW.m-3. Zooplankton biomass at the net-cage area surface was higher when compared with the control area during the months of October to January. However, the zooplankton biomass was similar at the bottom of the two areas throughout the studied period. From February until May, zooplankton biomass decreased in both sampling stations, a fact probably associated with the flushing of the reservoir, followed by an increase in water transparency and a decrease in chlorophyll-a concentration in the following months (February to May). CONCLUSIONS: The influence of fish farming on zooplankton biomass was detected at the surface of the net-cage area only from October to January. From February to May this influence was not found, probably by the influence of the flushing of the reservoir.

Boron Deficiency in a Southern Pine Nursery

1982 ◽  
Vol 6 (2) ◽  
pp. 108-112 ◽  
Author(s):  
E. L. Stone ◽  
C. A. Hollis ◽  
E. L. Barnard
Keyword(s):  
Pinus Taeda ◽  
Soil Management ◽  
Late Summer ◽  
Dry Weight ◽  
Height Growth ◽  
Boron Deficiency ◽  
First Year ◽  
Normal Height ◽  
High Calcium ◽  
Pinus Taeda L

Abstract Boron deficiency in seedling loblolly (Pinus taeda L.) and slash pine (Pinus elliotti Engelm.) in a northern Florida nursery was diagnosed by: (1) characteristic damage to shoot tips and buds, including necrosis of only part of the terminal; and (2) boron concentrations as low as only 1.9 ppm (dry weight) in affected tissues. Soil and soil-management features associated with deficiency include extremely low silt and clay contents, organic matter levels of 1 percent or less, lack of boron addition, and high calcium irrigation water leading to soil reactions above pH 6 by late summer. Consequences of deficiency were not limited to the nursery. Damaged seedlings that survived outplanting developed into bushy plants incapable of normal height growth in the first year or two.

scholarly journals Variation in ω-3 and ω-6 Polyunsaturated Fatty Acids Produced by Different Phytoplankton Taxa at Early and Late Growth Phase

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 559 ◽  
Author(s):  
Sami Taipale ◽  
Elina Peltomaa ◽  
Pauliina Salmi
Keyword(s):  
Fatty Acids ◽  
Polyunsaturated Fatty Acids ◽  
Growth Phase ◽  
Essential Fatty Acids ◽  
Late Summer ◽  
Dry Weight ◽  
Stationary Growth Phase ◽  
Epa And Dha ◽  
Average Proportion ◽  
Aquatic Food

Phytoplankton synthesizes essential ω-3 and ω-6 polyunsaturated fatty acids (PUFA) for consumers in the aquatic food webs. Only certain phytoplankton taxa can synthesize eicosapentaenoic (EPA; 20:5ω3) and docosahexaenoic acid (DHA; 22:6ω3), whereas all phytoplankton taxa can synthesize shorter-chain ω-3 and ω-6 PUFA. Here, we experimentally studied how the proportion, concentration (per DW and cell-specific), and production (µg FA L−1 day−1) of ω-3 and ω-6 PUFA varied among six different phytoplankton main groups (16 freshwater strains) and between exponential and stationary growth phase. EPA and DHA concentrations, as dry weight, were similar among cryptophytes and diatoms. However, Cryptomonas erosa had two–27 times higher EPA and DHA content per cell than the other tested cryptophytes, diatoms, or golden algae. The growth was fastest with diatoms, green algae, and cyanobacteria, resulting in high production of medium chain ω-3 and ω-6 PUFA. Even though the dinoflagellate Peridinium cinctum grew slowly, the content of EPA and DHA per cell was high, resulting in a three- and 40-times higher production rate of EPA and DHA than in cryptophytes or diatoms. However, the production of EPA and DHA was 40 and three times higher in cryptophytes and diatoms than in golden algae (chrysophytes and synyrophytes), respectively. Our results show that phytoplankton taxon explains 56–84% and growth phase explains ~1% of variation in the cell-specific concentration and production of ω-3 and ω-6 PUFA, supporting understanding that certain phytoplankton taxa play major roles in the synthesis of essential fatty acids. Based on the average proportion of PUFA of dry weight during growth, we extrapolated the seasonal availability of PUFA during phytoplankton succession in a clear water lake. This extrapolation demonstrated notable seasonal and interannual variation, the availability of EPA and DHA being prominent in early and late summer, when dinoflagellates or diatoms increased.

Solar Ultraviolet Radiation Exposure among Outdoor Workers in Three Canadian Provinces

2019 ◽  
Vol 63 (6) ◽  
pp. 679-688 ◽  
Author(s):  
Cheryl E Peters ◽  
Elena Pasko ◽  
Peter Strahlendorf ◽  
Dorothy Linn Holness ◽  
Thomas Tenkate
Keyword(s):  
British Columbia ◽  
Ultraviolet Radiation ◽  
Linear Models ◽  
Late Summer ◽  
Solar Ultraviolet Radiation ◽  
Sun Safety ◽  
Outdoor Workers ◽  
Exposure Limit ◽  
Canadian Provinces ◽  
Solar Ultraviolet

AbstractIntroductionSolar ultraviolet radiation (UVR) exposure places outdoor workers at risk of skin cancer and exposure is difficult to control. In response, the Sun Safety at Work Canada (SSAWC) project was undertaken (2014–2016). The purpose of this substudy was to characterize the UVR exposure levels of outdoor workers in the SSAWC project.MethodsThirteen workplaces in the provinces of British Columbia, Ontario, and Nova Scotia participated in an exposure monitoring campaign (late summer/early fall 2016). Study participants were workers from power utilities and municipalities. Participants wore a UVR measurement badge (light-sensitive polysulfone plastic) on their wrist, shoulder, or hardhat. Badge calibration and absorbance measurements were performed in the AusSun Research Lab. Personal UVR doses are presented as standard erythemal doses (SED) and compared with the internationally recommended exposure limit (1.3 SED), as well as to the total available UVR by date. Generalized linear models were used to examine determinants of solar UVR for personal UVR dose (for both SED and percent of ambient UVR). Models considered badge placement, date, province, industry, main job task, and the hours spent outdoors.ResultsMean personal UVR dose of participating workers was 6.1 SED (nearly 5× the recommended limit). Just 14% of workers experienced ‘acceptable’ levels of solar radiation; 10% were exposed at >10 times the limit. In univariate analyses, workers in Ontario had the highest levels (mean 7.3 SED), but even in the lowest exposed province (British Columbia), the mean personal UVR dose was 4.5 SED. Utility workers had double the exposure of municipal workers (10.4 and 5.5 SED, respectively). In the determinants of exposure models, the differences by province were muted, but utility line workers and those in general maintenance had higher predicted exposures. Those who wore their badge on their hardhat also had higher values of SED in the fully adjusted determinants models.ConclusionsSolar ultraviolet overexposure among outdoor workers is a concern, even in a country like Canada with relatively low ambient UVR. Implementation of sun safety programs should be supported in an effort to reduce exposure in this vulnerable group of workers.

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