Marion Lake (IBP) — from Bacteria to Fish

1974 ◽  
Vol 31 (5) ◽  
pp. 893-911 ◽  
Author(s):  
Ken J. Hall ◽  
Kim D. Hyatt
Keyword(s):  
Organic Matter ◽  
Simulation Models ◽  
Benthic Algae ◽  
Salmo Gairdneri ◽  
Sediment Particle Size ◽  
Solute Uptake ◽  
Important Pathway ◽  
Benthic Food ◽  
Average Size ◽  
Small Average Size

The microbial–detritus food chain in the sediment of Marion Lake, British Columbia, is an important pathway for the cycling of organic matter derived from both allochthonous (leaf litter) and autochthonous (phytoplankton, aquatic macrophytes, and benthic algae) sources. The activity of the sediment microbial community (approximately 109–1010 cells/g dry wt) as estimated by oxygen consumption and solute uptake is greatest during the summer months, when water temperatures are higher than 10 C. Solute uptake is also influenced by sediment depth, nutrient enrichment, sediment particle size, and oxygen concentration. Organic matter from natural sources such as algal excretion, interstitial water, and leaf detritus is complex and is not assimilated as rapidly as the simpler organic compounds.Rainbow trout (Salmo gairdneri) and kokanee (Oncorhynchus nerka) in Marion Lake are characterized by small average size and slow growth rates. Fish production, although highly variable, is at the low end of the range compared to other salmonid producing systems. These characteristics are related to the inefficiency of trout and kokanee in cropping the benthic food supply. Experiments with individual predators and their prey have identified the nature of many of the interactions controlling the availability of benthic prey to the predators. Construction of simulation models shows promise as a means to quantify the importance of such interactions.

scholarly journals Structures of spontaneous deletions in Caenorhabditis elegans.

1988 ◽  
Vol 8 (9) ◽  
pp. 3748-3754 ◽  
Author(s):  
R A Pulak ◽  
P Anderson
Keyword(s):  
Caenorhabditis Elegans ◽  
Structural Features ◽  
Chain Gene ◽  
Wild Type ◽  
Heavy Chain Gene ◽  
Myosin Heavy Chain Gene ◽  
Base Pairs ◽  
Average Size ◽  
Distinguishing Features ◽  
Small Average Size

We have investigated the structural features of spontaneous deletions in Caenorhabditis elegans. We cloned and sequenced the junctions of 16 spontaneous deletions affecting the unc-54 myosin heavy-chain gene and compared their sequences with those of the wild type. We analyzed these sequences in an attempt to identify structural features of the gene that are consistently involved in the spontaneous deletion process. Most deletions (15 of 16) removed a single contiguous region of DNA, with no nucleotides inserted or rearranged at the deletion junctions; one deletion was more complex. unc-54 deletions were small, averaging 600 base pairs in length, and were randomly distributed throughout the gene. Unlike deletions that occur in Escherichia coli, spontaneous unc-54 deletions did not contain statistically significant direct or inverted repeats at or near their termini. Except for their small average size, we have not identified any distinguishing features of their sequence or structure. We discuss these results with regard to the mechanisms for spontaneous deletion in eucaryotic and procaryotic cells.

scholarly journals Effect of Trace Yttrium Addition and Heat Treatment on the Microstructure and Mechanical Properties of As-Cast ADC12 Aluminum Alloy

2018 ◽  
Vol 9 (1) ◽  
pp. 53 ◽  
Author(s):  
Jianlong Liu ◽  
Qingjie Wu ◽  
Hong Yan ◽  
Songgen Zhong ◽  
Zhixiang Huang
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aluminum Alloy ◽  
Primary Si ◽  
Microstructure And Mechanical Properties ◽  
Yttrium Addition ◽  
The Matrix ◽  
The Mean ◽  
Average Size ◽  
Small Average Size

The effects of rare earth yttrium (Y) additions and the heat treatment process on the microstructure and mechanical properties of as-cast ADC12 aluminum alloy have been investigated. The results showed that the primary Si crystals were significantly refined from long axis to fibrous or granular when the Y content was 0.2 wt%. Compared to the matrix, the mean area and aspect ratio were decreased by 92% and 75%, respectively. Moreover, the Si and Fe-rich phases were spheroidized and refined with a small average size during the solid solution. It was also noted that the copper-rich phases were dissolved into the matrix. Correspondingly, it was found that after metamorphic and heat treatment the ultimate tensile strength (UTS), elongation, and, hardness increased by 81.9%, 69.7%, and 74.8%, respectively, compared to the matrix. The improved mechanical properties can primarily be attributed to the optimization of the microstructure and the refinement of various phases.

Lake Wabamun, Alta.: a paleoenvironmental study

1984 ◽  
Vol 62 (7) ◽  
pp. 1438-1465 ◽  
Author(s):  
M. Hickman ◽  
C. E. Schweger ◽  
T. Habgood
Keyword(s):  
Organic Matter ◽  
Catchment Area ◽  
Benthic Algae ◽  
Climatic Changes ◽  
Water Levels ◽  
Sedimentary Organic Matter ◽  
Tephra Layer ◽  
The Holocene ◽  
Fossil Pigments ◽  
The Core

Results from paleoenvironmental investigations of Lake Wabamun, Alta. (longitudes 114°26′ and 114°44′ W; latitudes 50°30′ and 53°35′ N), show that the sedimentary record spans the Holocene period in the case of the core taken from the deepest portion of the lake (the Seba core), while the record from the shallow Moonlight Bay spans a somewhat shorter interval. Basically, the lake has changed little during the last 4000 years except for increases in submersed hydrophytes in Moonlight Bay and undoubtedly other shallow regions of the lake. Production, too, has changed little during this interval except in Moonlight Bay, where hydrophytes and benthic algae contributed more to the sedimentary organic matter and fossil pigments. The deposition of the Mt. Mazama tephra in the catchment area and lake at 6600 years BP may have had a profound effect upon the lake. Increased turbidity occurred. This together with climatic changes including increased precipitation and catchment-area instability caused rapid infilling of the lake and low production. Moreover, prior to deposition of the tephra layer, water levels were lower and the water was more saline with Ruppia present, a feature found in other lakes in Alberta during the Hypsithermal period. Finally, prior to this period the lake was similar to its present day condition except during its very beginning when more turbid conditions prevailed.

N-loss stoichiometry in a Peru ODZ eddy

2019 ◽  
Vol 77 (2) ◽  
pp. 169-189
Author(s):  
Mark A. Altabet ◽  
Annie Bourbonnais
Keyword(s):  
Organic Matter ◽  
Nitrogen Loss ◽  
Mesoscale Eddy ◽  
Additional Constraint ◽  
N Loss ◽  
Important Pathway ◽  
Theory Result ◽  
Natural Laboratory ◽  
Heterotrophic Denitrification ◽  
Microbial N

Assuming heterotrophic denitrification as the dominant microbial process, Richards (1965) formulated a stoichiometry governing nitrogen loss in open-ocean oxygen deficient zones (ODZs). It prescribes the quantitative coupling between the oxidation of organic matter by NO–3 in the absence of O2 and the corresponding production of CO2, N2, and PO–34. Applied globally, this relationship defines key linkages between the C, N, and P cycles. However, the validity of Richards's stoichiometry is challenged by recognition of complex microbial N processing in ODZs including anammox as an important pathway and nitrite reoxidation. Whereas Richards's stoichiometry would result in N2-N production to NO–3 removal rates of 1.17, dominance by anammox with respect to biogenic N2 production could in theory result in a ratio as high as 2. Ratios with PO–34 production provide an additional constraint on the quantity and composition of respired organic matter. Here we use a mesoscale eddy with extreme N-loss in the Peru ODZ as a "natural laboratory" to examine N-loss stoichiometry. Its intense biogeochemical signatures, relatively well-defined timescales, and simplified hydrography allowed for the development of strong co-occurring gradients in NO–3, NO–2, biogenic N2, and PO–34. The production of biogenic N2 as compared with the removal of NO–3 (analyzed either directly or as N deficits) was slightly less than predicted by Richards's stoichiometry and did not at all support any "excess" biogenic N2. PO–34 production, however, was twice the expectation from Richards's stoichiometry suggesting that respired organic matter was P-rich as compared with C:N:P Redfield composition. These results suggest major gaps remain between current understanding of microbial N pathways in ODZs and their net biogeochemical output.

Morphological Response of Bolivina Lowmani to Sediment Composition and Organic Matter: Applying Geometric Morphometrics for Potential Bio-Monitoring

2020 ◽  
Vol 50 (3) ◽  
pp. 249-265
Author(s):  
Margarette Bayrón-Arcelay ◽  
Kyara Rodríguez-Camacho ◽  
Dimaris Acosta-Mercado
Keyword(s):  
Organic Matter ◽  
Geometric Morphometrics ◽  
Benthic Foraminifera ◽  
Organic Matter Content ◽  
Matter Content ◽  
Anthropogenic Pressure ◽  
Sediment Composition ◽  
Morphological Response ◽  
Size And Shape ◽  
Average Size

ABSTRACT It is well established that sediment composition plays an important role in shaping the community of benthic foraminifera (e.g., species richness). To our knowledge, there is little information about morphometric variations in benthic foraminifera in relation to sediment composition and organic matter content. However, given their sensitivity to these environmental variables, variations in size (width and height of the test) and shape (form of the test) of the foraminifera could provide information about potential disturbances, serving as an index of anthropogenic pressure for coastal ecosystems. In this study, we used geometric morphometrics to compare the average size and shape of a common species, Bolivina lowmani, among islets in La Parguera, Puerto Rico. We hypothesized that the average size and shape of B. lowmani will be different among islets. We further hypothesize that there will be a concomitant morphometric gradient of B. lowmani with sediment particle size and organic matter content. After a random sampling approach, we found that size regressed as a function of mud content and shape variations regressed as a function of organic matter content. Therefore, sediment composition could be a factor affecting foraminiferal growth rates highlighting that the morphometrics of benthic foraminifera could be added to the list of potential indexes that could be used to track current environmental degradation in coastal habitats. Furthermore, our data validate the sensitivity of foraminifera and their usefulness as indicators of environmental hazards.

Projecting the effects of climate-driven changes in organic matter supply on benthic food webs in the northern Bering Sea

2016 ◽  
Vol 548 ◽  
pp. 11-30 ◽  
Author(s):  
JR Lovvorn ◽  
CA North ◽  
JM Kolts ◽  
JM Grebmeier ◽  
LW Cooper ◽  
...  
Keyword(s):  
Organic Matter ◽  
Food Webs ◽  
Bering Sea ◽  
Northern Bering Sea ◽  
Benthic Food ◽  
Benthic Food Webs
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