scholarly journals Impacts of meltwater discharge from marine-terminating glaciers on the protist community in Inglefield Bredning, northwestern Greenland

2020 ◽  
Vol 642 ◽  
pp. 55-65 ◽  
Author(s):  
K Matsuno ◽  
N Kanna ◽  
S Sugiyama ◽  
A Yamaguchi ◽  
EJ Yang
Keyword(s):  
Surface Layer ◽  
Standing Stock ◽  
Nutrient Inputs ◽  
Heterotrophic Dinoflagellate ◽  
Study Region ◽  
High Nutrient ◽  
Subsurface Layers ◽  
Food Conditions ◽  
High Turbidity ◽  
Subglacial Meltwater

To evaluate the effects of meltwater discharge from marine-terminating glaciers on a fjord protist community in northwestern Greenland during summer, we investigated the distribution, abundance and biomass of the protist community and their relationships with hydrographic parameters. In the standing stock of protists, dinoflagellates (46.4%) and oligotrich ciliates (39.5%) were dominant throughout the study region. With respect to vertical distribution, oligotrich ciliates were abundant in the surface layer, mainly due to suitable food conditions (abundance of diatom and nanoflagellates). Near glaciers, relatively high chlorophyll a (chl a) concentrations were found in the subsurface layers associated with the low-temperature, high-turbidity and slightly high nutrient levels, indicating that the nutrient inputs from the upwelling glacial meltwater plume increased primary production. Large-sized Protoperidium spp. were found only at stations near glaciers where nutrients were abundant, and heterotrophic dinoflagellates showed strong relationships with nanoflagellates. These findings suggest that the upwelling associated with subglacial meltwater discharge can stimulate nanoflagellate production, resulting in increases in ciliate and heterotrophic dinoflagellate production.

Historical analysis of changes in land use and carbon stock of vegetation in south and southeast Asia

1991 ◽  
Vol 21 (1) ◽  
pp. 91-110 ◽  
Author(s):  
Elizabeth P. Flint ◽  
John F. Richards
Keyword(s):  
Land Use ◽  
Carbon Content ◽  
Carbon Stock ◽  
Demographic Data ◽  
Standing Stock ◽  
Carbon Equivalent ◽  
Vegetation Types ◽  
Study Region ◽  
Entire Study ◽  
Ecological Zones

A time series (1880, 1920, 1950, 1980) of estimates of land use and carbon content of vegetation is presented for a contiguous area of 1.7 × 106 km2 in northern India, Bangladesh, and Burma. This was developed using sequential bookkeeping models, which systematically incorporate official agricultural and forest statistics with ecological, botanical, historical, geographical, and demographic data. For 149 administrative units, aggregated into 39 ecological zones, we estimated area and carbon content for each of the following land-use categories: net cultivated area, settled–built-up area, forest–woodland, interrupted woods, grass–shrub complexes, barren – sparsely vegetated areas, wetlands, and surface water. Dominant patterns of land-use change were deforestation, agricultural expansion, and wetland clearance, but significant regional and temporal disparities were observed. For the entire study region, the estimated standing stock of carbon in biomass declined by 2.62 Gt over the century. Release by periods was 911 Mt for 1880–1920, 750 Mt for 1920–1950, and 964 Mt for 1950–1980. Forest–woodland and interrupted woods vegetation released carbon equivalent to over 90% of the total release. Both conversion of forest to other vegetation types and reduction over time of biomass within vegetation types contributed significantly to decreases in total standing carbon stock during the period.

Analysis of Surface and Subsurface Layers after Shot Peening of Various Aluminium Alloys

2010 ◽  
Vol 89-91 ◽  
pp. 53-58
Author(s):  
Sebastjan Žagar ◽  
Janez Grum
Keyword(s):  
Surface Layer ◽  
Crack Initiation ◽  
Residual Stresses ◽  
Surface Integrity ◽  
Shot Peening ◽  
Aluminium Alloys ◽  
Surface Hardening ◽  
Hardened Layer ◽  
Operating Pressure ◽  
Subsurface Layers

In the paper two aluminium alloys, i.e. 6082 and 7075, which were cold hardened by shot peening under different conditions, are treated. Surface hardening was carried out with S170 steel shot of the same diameter, particle hardness being 56 HRC. Other conditions were the operating pressure, mass flow, which provide different Almen intensities. The hardened layer was described by surface integrity. Macroscopic and microscopic analyses consisted in analyses of hardened profiles of hardness, and residual stresses in the thin surface layer. Research results indicated that there were significant differences among the characteristics chosen to describe surface integrity and that they had an important influence on the final condition of the surface layer. With too severe settings of the peening parameters, the surface properties got worse because of damages, which resulted in crack initiation and growth of the existing cracks.

scholarly journals Hydrophysical characteristics of selected soils from arctic and temperate zones

2015 ◽  
Vol 29 (4) ◽  
pp. 525-531
Author(s):  
Barbara Witkowska-Walczak ◽  
Piotr Bartmiński ◽  
Cezary Sławiński
Keyword(s):  
Surface Layer ◽  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Temperate Zone ◽  
The Arctic ◽  
Arctic Zone ◽  
Water Conductivity ◽  
Water Potentials ◽  
Subsurface Layers

Abstract Hydrophysical characteristics of arctic and temperate zones soils were determined. The soils from the temperate zone showed a greater capability of water retention than those from the arctic zone. In both investigated depths (surface and subsurface layers), the highest water content was observed for the Sądecki Regosol, and the lowest one for Turbic Cryosol formed in the cell forms from Spitsbergen at all soil water potentials. The differences between water content for these soils at the same soil water potentials varied between 20 and 25% vol. in the surface layer, and from 19 to 22% vol. in the subsurface, respectively. The lowest differences (2.7-5.0% vol.) in water content were noticed between the Wyspowy Regosol and Turbic Cryosol (Skeletic) derived in the sorted circles. In both depths, higher values of water conductivity were observed for Regosols than for Cryosols at high soil water potentials, from -0.1 till -7 kJ m-3. These differences were especially high at -0.1 kJ m-3 and they were three or four times higher for soils from the temperate zone than from the arctic ones. For lower water potentials, the differences in water conductivity do not exceed one order in the surface layer and two orders in the subsurface.

Microphytoplankton and ciliate communities’ structure and distribution in a stressed area of the south coast of Sfax, Tunisia (eastern Mediterranean Sea)

2016 ◽  
Vol 67 (10) ◽  
pp. 1445 ◽  
Author(s):  
Amira Rekik ◽  
Jannet Elloumi ◽  
Dorra Chaari ◽  
Habib Ayadi
Keyword(s):  
Surface Layer ◽  
Coastal Waters ◽  
Eastern Mediterranean ◽  
Environmental Parameters ◽  
Numerical Density ◽  
Eastern Mediterranean Sea ◽  
Ciliate Abundance ◽  
Ciliate Species ◽  
High Nutrient ◽  
Sediment Interface

The environmental parameters, microphytoplankton and ciliate communities in the area were studied in spring and autumn at 20 stations along the coast south of Sfax over two seasons during 2011. The results showed that the environmental parameters indicated high nutrient levels and their concentrations ranges reported as criteria of eutrophication in coastal waters. A total of 78 microphytoplankton species were identified, belonging to Diatoms, Dinoflagellates, Cyanobacteriae, Euglenophyceae, Dictyochophyceae and Chlorophyceae. The numerical density of phytoplankton was high over the whole area, with season averages between 44.10×102 ±41.93×102 and 103.55×102 ± 107.33×102 cells L–1. A total of 58 ciliate species were identified at all of the stations. Tintinnids abundance was generally higher than naked ciliate abundance reported for autumn and spring seasons, both at the surface layer and water–sediment interface. One striking point was that ciliate abundance was unchanged in autumn (4×102 cells L–1) but was still higher in spring (6×102 cells L–1). Some species reported in this study are commonly found in the stressed coastal waters.

scholarly journals Rates of Species Accumulation and Taxonomic Diversification during Phototrophic Biofilm Development Are Controlled by both Nutrient Supply and Current Velocity

2013 ◽  
Vol 79 (6) ◽  
pp. 2054-2060 ◽  
Author(s):  
Chad A. Larson ◽  
Sophia I. Passy
Keyword(s):  
Species Richness ◽  
Current Velocity ◽  
Beta Diversity ◽  
Taxon Richness ◽  
Temporal Heterogeneity ◽  
Nutrient Inputs ◽  
Species Accumulation ◽  
High Nutrient ◽  
Temporal Beta Diversity ◽  
Biofilm Development

ABSTRACTThe accumulation of new and taxonomically diverse species is a marked feature of community development, but the role of the environment in this process is not well understood. To address this problem, we subjected periphyton in laboratory streams to low (10-cm · s−1), high (30-cm · s−1), and variable (9- to 32-cm · s−1) current velocity and low- versus high-nutrient inputs. We examined how current velocity and resource supply constrained (i) the rates of species accumulation, a measure of temporal beta-diversity, and (ii) the rates of diversification of higher taxonomic categories, defined here as the rate of higher taxon richness increase with the increase of species richness. Temporal biofilm dynamics were controlled by a strong nutrient-current interaction. Nutrients accelerated the rates of accumulation of new species, when flow velocity was not too stressful. Species were more taxonomically diverse under variable than under low-flow conditions, indicating that flow heterogeneity increased the niche diversity in the high-nutrient treatments. Conversely, the lower diversification rates under high- than under low-nutrient conditions at low velocity are explained with finer resource partitioning among species, belonging to a limited number of related genera. The overall low rates of diversification in high-current treatments suggest that the ability to withstand current stress was conserved within closely related species. Temporal heterogeneity of disturbance has been shown to promote species richness, but here we further demonstrate that it also affects two other components of biodiversity, i.e., temporal beta-diversity and diversification rate. Therefore, management efforts for preserving the inherent temporal heterogeneity of natural ecosystems will have detectable positive effects on biodiversity.

scholarly journals Growth and photosynthesis responses of two co-occurring marsh grasses to inundation and varied nutrients

Botany ◽  
2015 ◽  
Vol 93 (10) ◽  
pp. 671-683 ◽  
Author(s):  
Elizabeth Burke Watson ◽  
Holly M. Andrews ◽  
Amy Fischer ◽  
Morgan Cencer ◽  
Laura Coiro ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Nutrient Availability ◽  
Tidal Marshes ◽  
Nutrient Loads ◽  
Nutrient Inputs ◽  
Nutrient Additions ◽  
High Nutrient ◽  
Us Northeast ◽  
Tiller Density

For tidal marshes of the US Northeast, the late twentieth century decline of Spartina patens (Aiton) Muhl. has been attributed to increased flooding associated with accelerated sea level rise and nitrogen over-enrichment from cultural eutrophication. The objective of this study was to examine the impacts of inundation and nutrient availability on growth, photosynthesis, and interactions of S. patens and Distichlis spicata (L.) Greene, which co-occur and are common marsh species. Plants were grown in a factorial greenhouse experiment, where flow-through seawater was used to simulate semidiurnal tides. Field surveys were additionally conducted to relate plant distributions to environmental conditions. For S. patens grown in monoculture, nutrient additions did not enhance growth for the high inundation treatment. In addition, the combination of high nutrient availability and high inundation adversely affected S. patens tiller density, photosynthetic efficiency, and leaf CO2 uptake. For D. spicata, nutrient additions enhanced growth for both inundation treatments with respect to aboveground biomass and tiller density. For species pairings, S. patens expanded relative to D. spicata under low inundation, low nutrient availability conditions, but declined relative to D. spicata under daily inundation in combination with nutrient amendments. These findings were additionally supported by field data, which indicated that D. spicata was more common than S. patens where nutrient availability was high. These results suggest that S. patens persistence is favored by low nutrient inputs and well-drained conditions, and supports the interpretation that this species is vulnerable to loss where high nutrient loads coincide with accelerated sea level rise.

scholarly journals High-resolution fisheries data reveal effects of bivalve dredging on benthic communities in stressed coastal systems

2020 ◽  
Vol 642 ◽  
pp. 21-38 ◽  
Author(s):  
C McLaverty ◽  
OR Eigaard ◽  
GE Dinesen ◽  
H Gislason ◽  
A Kokkalis ◽  
...  
Keyword(s):  
High Resolution ◽  
Species Composition ◽  
Nutrient Loading ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Natura 2000 ◽  
Environmental Drivers ◽  
Nutrient Inputs ◽  
High Nutrient ◽  
Suitable Reference

Commercial dredging for blue mussels (Mytilus edulis) and oysters (Ostrea edulis, Crassostrea gigas) constitute the main bivalve fisheries in Denmark. These activities predominantly take place in Limfjorden, a large microtidal sound, and in the Inner Danish waters. Both areas are shallow, estuarine, receive high nutrient inputs from agriculture, and are of nature conservation interest (Natura 2000 sites), thus presenting challenges for an ecosystem approach to fisheries management. Using high-resolution fisheries data (~10 m), we investigated the effects of bivalve dredging on benthic communities at both local (Natura 2000 site) and regional (fishery-wide) scales. Regionally, our results showed that dredging intensity correlated with shifts in species composition and reduced community biomass. We were, however, unable to detect an effect of dredging on community density, trait richness, and trait composition. These metrics were significantly related to other environmental drivers, such as sediment organic content (negative) and mussel bed biomass (positive). At the local scale, the observed relationships between dredging, biomass, and species composition varied significantly. This occurred as dredging impacts were greater in areas that contained suitable reference conditions and experienced relatively low levels of disturbance. By contrast, communities which experienced high nutrient loading, regular anoxic events, and high natural variability were relatively unaffected by dredging. Our results therefore highlight the importance of spatial scales in fishing impact estimations. Furthermore, we demonstrate how targeted sampling, high-resolution fisheries data, and suitable reference areas can be used to detect fishery effects in coastal areas that are highly stressed by eutrophication.

scholarly journals Estimates of micro-, nano-, and picoplankton contributions to particle export in the northeast Pacific

2014 ◽  
Vol 11 (8) ◽  
pp. 12631-12671
Author(s):  
B. L. Mackinson ◽  
S. B. Moran ◽  
M. W. Lomas ◽  
G. M. Stewart ◽  
R. P. Kelly
Keyword(s):  
Organic Carbon ◽  
Standing Stock ◽  
Northeast Pacific ◽  
Total Pigment ◽  
High Nutrient ◽  
Small Phytoplankton ◽  
Important Pathway ◽  
Particle Export ◽  
Ocean Station Papa ◽  
Line P

Abstract. The contributions of micro-, nano-, and picoplankton to particle export were estimated from measurements of size-fractionated particulate 234Th, organic carbon, and phytoplankton indicator pigments obtained during five cruises between 2010 and 2012 along Line P in the subarctic northeast Pacific Ocean. Sinking fluxes of particulate organic carbon (POC) and indicator pigments were calculated from 234Th–238U disequilibria and, during two cruises, measured by sediment trap at Ocean Station Papa. POC fluxes at 100 m ranged from 0.65–7.95 mmol m−2 d−1, similar in magnitude to previous results at Line P. Microplankton pigments dominate indicator pigment fluxes (averaging 69 ± 19% of total pigment flux), while nanoplankton pigments comprised the majority of pigment standing stocks (averaging 64 ± 23% of total pigment standing stock). Indicator pigment loss rates (the ratio of pigment export flux to pigment standing stock) point to preferential export of larger microplankton relative to smaller nano- and picoplankton. However, indicator pigments do not quantitatively trace particle export resulting from zooplankton grazing, which may be an important pathway for the export of small phytoplankton. These results have important implications for understanding the magnitude and mechanisms controlling the biological pump at Line P in particular, and more generally in oligotrophic gyres and high-nutrient, low-chlorophyll regions where small phytoplankton represent a major component of the autotrophic community.

Growth of microorganisms in Martian-like shallow subsurface conditions: laboratory modelling

2009 ◽  
Vol 9 (1) ◽  
pp. 51-58 ◽  
Author(s):  
A.K. Pavlov ◽  
V.N. Shelegedin ◽  
M.A. Vdovina ◽  
A.A. Pavlov
Keyword(s):  
Surface Layer ◽  
Water Vapour ◽  
Diffusion Layer ◽  
Liquid Water ◽  
Limiting Factors ◽  
Active Growth ◽  
Shallow Subsurface ◽  
Vapour Diffusion ◽  
Subsurface Layers ◽  
Laboratory Modelling

AbstractLow atmospheric pressures on Mars and the lack of substantial amounts of liquid water were suggested to be among the major limiting factors for the potential Martian biosphere. However, large amounts of ice were detected in the relatively shallow subsurface layers of Mars by the Odyssey Mission and when ice sublimates the water vapour can diffuse through the porous surface layer of the soil. Here we studied the possibility for the active growth of microorganisms in such a vapour diffusion layer. Our results showed the possibility of metabolism and the reproduction of non-extremophile terrestrial microorganisms (Vibrio sp.) under very low (0.01–0.1 mbar) atmospheric pressures in a Martian-like shallow subsurface regolith.

Eutrophication in the High Arctic — Meretta Lake, Cornwallis Island (75° N Lat.)

1974 ◽  
Vol 31 (5) ◽  
pp. 647-662 ◽  
Author(s):  
D. W. Schindler ◽  
J. Kalff ◽  
H. E. Welch ◽  
G. J. Brunskill ◽  
H. Kling ◽  
...  
Keyword(s):  
Algal Species ◽  
Oxygen Depletion ◽  
High Arctic ◽  
Arctic Lakes ◽  
Nutrient Inputs ◽  
Lake Surface ◽  
Annual Cycles ◽  
High Nutrient ◽  
Resolute Bay ◽  
Cornwallis Island

Sewage from the Department of Transport Airport Base at Resolute Bay has caused increases in phytoplankton standing crop, changes in algal species composition, oxygen depletion, and disappearance of Limnocalanus in Meretta Lake. The annual cycles of chemical and physical events associated with these changes are described. Minimum annual input of phosphorus to Meretta Lake was 0.24–0.29 g/m2 of lake surface per year in 1971, with 66–80% supplied by sewage. Nitrogen input was 0.55–0.78 g/m2 during the same year, with 41 to 58% from sewage. Results show that severe eutrophication problems may be expected to develop in response to high nutrient inputs, even at arctic latitudes. Arctic lakes, which are sealed under ice for several months of the year, appear to be particularly vulnerable to increased oxygen depletion which accompanies eutrophication.

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