Bacterioplankton production, abundance, and nutrient limitation among lakes of the Mackenzie Delta (western Canadian arctic)

2006 ◽  
Vol 63 (4) ◽  
pp. 845-857 ◽  
Author(s):  
Bryan M Spears ◽  
Lance FW Lesack
Keyword(s):  
Nutrient Limitation ◽  
Bacterial Production ◽  
Light Attenuation ◽  
Open Water ◽  
Flood Frequency ◽  
Inorganic Nutrient ◽  
Mackenzie Delta ◽  
Bacterial Productivity ◽  
River Flooding ◽  
Bacterioplankton Production

The effects of nutrient availability and quality of dissolved organic carbon (DOC) on bacterioplankton production were assessed in six lakes with differing frequencies of river flooding. Bacterial productivity, dissolved nutrients, and DOC were tracked weekly throughout the open-water period of 2001. Inorganic nutrient (N and P) enrichment microcosm experiments were conducted to directly assess the effects of DOC quality (i.e., mixtures of colored and noncolored DOC) and inorganic nutrient limitation on bacterial productivity among the lakes. Averaged over the open-water season, both abundance and production of bacterioplankton increased with decreasing flood frequency (R2 = 0.61 and R2 = 0.78, respectively). Reduced bacterial production occurred in frequently flooded lakes, where colored DOC, light attenuation, and phosphate were high but ammonium was low. Bacterial production was greatest in infrequently flooded lakes, where noncolored DOC and ammonium were high but phosphate was low. Bacterial production was enhanced by amendments of inorganic nutrients in duplicate experiments (two-factor analyses of variance). Production was also enhanced in response to higher concentrations of either colored or noncolored DOC following release from inorganic nutrient limitation. Size fractionated (<1 µm versus >1 µm) N-debt and P-debt bioassays typically showed demand for P and release of N by bacteria in all study lakes.

scholarly journals Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

2018 ◽  
Vol 4 (4) ◽  
pp. 557-583 ◽  
Author(s):  
Jolie A.L. Gareis ◽  
Lance F.W. Lesack
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Bacterial Production ◽  
River Discharge ◽  
Bacterial Community Composition ◽  
Open Water ◽  
Growth Efficiency ◽  
Mackenzie Delta ◽  
River Deltas ◽  
Solar Exposure

Lake-rich Arctic river deltas are recharged with terrigenous dissolved organic matter (DOM) during the yearly peak water period corresponding with the solstice (24 h day−1 solar irradiance). Bacteria-free DOM collected during peak Mackenzie River discharge was exposed to sunlight for up to 14 days in June 2010. As solar exposure increased, carbon and lignin concentrations declined (10% and 42%, respectively, after 14 days), as did DOM absorptivity (62% after 14 days), aromaticity, and molecular weight. Photochemical changes were on par with those normally observed in Mackenzie Delta lakes over the entire open-water season. When irradiated freshet DOM was provided as a substrate, no significant differences were observed in community-level metabolism among five bacterial communities from representative delta habitats. However, bacterial abundance was significantly greater when nonirradiated (0 day) rather than irradiated DOM (7 or 14 days) was provided, while cell-specific metabolic measures revealed that per-cell bacterial production and growth efficiency were significantly greater when communities were provided irradiated substrate. This complex response to rapid DOM photodegradation may result from the production of inhibitory reactive oxygen species (ROS), along with shifts in bacterial community composition to species that are better able to tolerate ROS, or metabolize the labile photodegraded DOM.

Water transparency and nutrients as controls on phytoplankton along a flood-frequency gradient among lakes of the Mackenzie Delta, western Canadian Arctic

2002 ◽  
Vol 59 (8) ◽  
pp. 1339-1349 ◽  
Author(s):  
Margaret M Squires ◽  
Lance F.W Lesack
Keyword(s):  
Nutrient Limitation ◽  
River Water ◽  
Flood Frequency ◽  
Light Limitation ◽  
Phytoplankton Production ◽  
Mackenzie Delta ◽  
Photosynthetic Rates ◽  
Nutrient Additions ◽  
P Limitation ◽  
Nutrient Conditions

Relatively low phytoplankton production among lakes of the Mackenzie Delta has been attributed to light limitation in frequently flooded lakes and to nutrient limitation among infrequently flooded lakes; productivity peaks have been attributed to optimal light–nutrient conditions at intermediate flood frequency. We found that the distribution and abundance of phytoplankton among a large number of lakes was explained by optimal light–nutrient conditions but not by nutrient or light limitation. For a subset of lakes, seasonal dynamics of biomass were consistent with light limitation and optimal light–nutrient conditions but not nutrient limitation; photosynthetic rates were consistent with optimal light–nutrient conditions and nutrient limitation but not light limitation. Results of dilution–deletion experiments across a light–nutrient gradient indicated transition from light limitation to optimal light–nutrient conditions to nutrient limitation. Surprisingly, adding river water to lake water did not increase photosynthetic rates; this result and experimental incubations in situ during river inflow and lake outflow suggested that continuous supply of river water may be necessary to increase phytoplankton growth rates. Among infrequently flooded lakes, phytoplankton response to nutrient additions showed that phosphorus (P) limitation was no more likely than nitrogen (N) limitation, co-limitation, or no limitation by N or P.

scholarly journals Oceanographic, ecological, and socio-economic impacts of an unusual summer storm in the Mackenzie Estuary

2020 ◽  
Vol 6 (2) ◽  
pp. 62-76 ◽  
Author(s):  
Kevin C. Scharffenberg ◽  
Dustin Whalen ◽  
Shannon A. MacPhee ◽  
Marianne Marcoux ◽  
John Iacozza ◽  
...  
Keyword(s):  
Habitat Use ◽  
Marine Mammals ◽  
Storm Surges ◽  
Open Water ◽  
Water Levels ◽  
Environmental Drivers ◽  
Mackenzie Delta ◽  
Arctic Ecosystems ◽  
Significant Drop ◽  
The Impact

With increased warming and open water due to climate change, the frequency and intensity of storm surges is expected to increase. Although studies have shown that strong storms can negatively impact Arctic ecosystems, the impact of storms on Arctic marine mammals is relatively unknown. In July 2016, an unusually large storm occurred in the Mackenzie Delta while instrumented seabed moorings equipped with hydrophones and oceanographic sensors were in place to study environmental drivers of beluga habitat use during their summer aggregation. The storm lasted up to 88 h, with maximum wind speeds reaching 60 km/h; historical wind data from Tuktoyaktuk revealed a storm of similar duration has not occurred in July in at least the past 28 years. This provided a unique opportunity to study the impacts of large storms on oceanographic conditions, beluga habitat use, and the traditional subsistence hunt that occurs annually in the delta. The storm resulted in increased water levels and localized flooding as well as a significant drop in water temperature (∼10 °C) and caused belugas to leave the area for 5 days. Although belugas returned after the storm ended, the subsistence hunt was halted resulting in the lowest beluga harvest between 1978 and 2017.

scholarly journals Distinct bacterial-production–DOC–primary-production relationships and implications for biogenic C cycling in the South China Sea shelf

2014 ◽  
Vol 11 (1) ◽  
pp. 147-156 ◽  
Author(s):  
C.-C. Lai ◽  
Y.-W. Fu ◽  
H.-B. Liu ◽  
H.-Y. Kuo ◽  
K.-W. Wang ◽  
...  
Keyword(s):  
South China Sea ◽  
Primary Production ◽  
South China ◽  
Bacterial Production ◽  
Northern South China Sea ◽  
Outer Shelf ◽  
Inorganic Nutrient ◽  
Shelf Area ◽  
China Sea ◽  
Spatio Temporal

Abstract. Based on two summer spatio-temporal data sets obtained from the northern South China Sea shelf and basin, this study reveals contrasting relationships among bacterial production (BP), dissolved organic (DOC) and primary production (PP) in the transition zone from the neritic to the oceanic regions. Inside the mid-shelf (bottom depth <100 m), where inorganic nutrient supplies from river discharge and internal waves were potentially abundant, BP, DOC and PP were positively intercorrelated, whereas these three measurements became uncorrelated in the oligotrophic outer shelf and slope. We suggest that the availability of limiting minerals could affect the couplings/decouplings between the source (i.e. phytoplankton) and sink (i.e. bacteria) of organic carbon, and thus DOC dynamics. DOC turnover times were homogeneously low (37–60 days) inside the mid-shelf area and then increased significantly to values >100 days in the outer shelf, indicating that riverine (Pearl River) DOC might be more labile. The actual mechanism for this is unknown, but might relate to higher inorganic nutrient supply from river/terrestrial sources. The positive correlation of the BP / PP ratios vs. phosphate (and nitrate) concentrations in the inner shelf implies that if anthropogenic mineral loading keeps increasing in the foreseeable future, the near-shore zone may become more heterotrophic, rendering the system a stronger source of CO2.

scholarly journals Flood frequency mapping of the middle Mahakam lowland area using satellite radar

2011 ◽  
Vol 8 (6) ◽  
pp. 11519-11552
Author(s):  
H. Hidayat ◽  
D. H. Hoekman ◽  
M. A. M. Vissers ◽  
A. J. F. Hoitink
Keyword(s):  
Water Level ◽  
Forest Canopy ◽  
Open Water ◽  
Flood Frequency ◽  
Data Availability ◽  
Flood Inundation ◽  
Radar Backscatter ◽  
Radar Images ◽  
Lowland Area ◽  
Water Level Measurements

Abstract. Floodplain lakes and peatlands in the middle Mahakam lowland area are considered as an ecologically important wetland in East Kalimantan, Indonesia. However, due to a lack of data, the hydrological functioning of the region is still poorly understood. Among remote sensing techniques that can increase data availability, radar is well-suitable for the identification, mapping, and measurement of tropical wetlands, for its cloud unimpeded sensing and night and day operation. Here we aim to extract flood extent and flood frequency information from a series of radar images of the middle Mahakam lowland area. We explore the use of Phased Array L-band Synthetic Aperture Radar (PALSAR) imagery for observing flood inundation dynamics by incorporating field water level measurements. Water level measurements were carried out along the river, in lakes and in peatlands, using pressure transducers. For validation of the open water flood frequency map, bathymetry measurements were carried out in the main lakes. A series of PALSAR images covering the middle and lower Mahakam area in the years 2007 through 2010 was collected. A fully inundated region can be easily recognized on radar images from a dark signature. Open water flood frequency was mapped using a threshold value taken from radar backscatter of the permanently inundated river and lakes area. Radar backscatter intensity analysis of the vegetated floodplain area revealed consistently high backscatter values, indicating flood inundation under forest canopy. We used those values as the threshold for flood frequency mapping in the vegetated area.

scholarly journals Development of primary and bacterial productivity in upwelling waters of Arraial do Cabo region, RJ (Brazil)

2004 ◽  
Vol 52 (1) ◽  
pp. 35-45 ◽  
Author(s):  
Wanderson Fernandes de Carvalho ◽  
Eliane Gonzalez Rodriguez
Keyword(s):  
Organic Matter ◽  
Bacterial Production ◽  
Bacterial Productivity ◽  
Phytoplankton Blooms ◽  
Bacterial Development ◽  
Development Stages ◽  
Stages Of Growth ◽  
Close Relationship ◽  
Stage Development ◽  
Stage Analysis

A relationship between phytoplankton and bacterioplankton has been observed in a laboratory experiment, simulating partial and complete upwelling conditions. Primary and bacterial productivity presented a similar pattern, with a three-stage development (growth, peak and decline in production). However, bacterial development stages did not occur simultaneously with the phytoplanktonic development, that is, the highest bacterial production rates occurred in the stages of growth and decline of the primary production, whilst the lowest values of bacterial productivity were simultaneous to the highest phytoplanktonic production stage. Analysis of data obtained in this experiment shows a close relationship between phytoplankton and bacteria, in which these organisms might be competing for inorganic nutrients in some moments, and bacteria might have, as an important source of carbon, the particulate or dissolved organic matter coming from the phytoplankton. Besides that, bacteria might play an important role in the initial stages of phytoplankton blooms, when they might be one of the main conditioning agents of the waters that have just upwelled, allowing the plain phytoplanktonic development.

scholarly journals Bacterial production in Guanabara Bay (Rio de Janeiro, Brazil) evaluated by ³H-leucine incorporation

2000 ◽  
Vol 43 (5) ◽  
pp. 493-500 ◽  
Author(s):  
Alessandra M. Gonzalez ◽  
Rodolfo Paranhos ◽  
Luciana Andrade ◽  
Jean L. Valentin
Keyword(s):  
Bacterial Production ◽  
Bacterial Biomass ◽  
Biogeochemical Cycles ◽  
Leucine Incorporation ◽  
Guanabara Bay ◽  
Bacterial Productivity ◽  
Isotope Concentration ◽  
Main Circulation ◽  
The Relationship ◽  
The Ideal

The aim of this work was to evaluate the necessary ³H-leucine concentration to estimate bacterial production in Guanabara Bay through saturation curves. A second aim was to collect preliminary data of bacterial production in two distinct sites corresponding to different water qualities: Urca inlet and Governador Island. Saturation curves were made with water samples taken at the main circulation channel of the bay, Paquetá Island, and the two sites mentioned before. The ³H-leucine curves showed similar pattern for all studied areas, indicating the ideal isotope concentration to be 10 nM. Bacterial biomass production ranged from 0.40 to 4.53 µgC L-1 h-1 in Urca and from 3.86 to 73.72 µgC L-1 h-1 in Governador Island indicating the relationship between nutrients and organic matter supply and bacterial productivity. This work is an important reference for studies on trophodynamics, biogeochemical cycles and modelling in Guanabara Bay.

Effects of Snow and Ice on the Annual Cycles of Heat and Light in Saqvaqjuac Lakes

1987 ◽  
Vol 44 (8) ◽  
pp. 1451-1461 ◽  
Author(s):  
Harold E. Welch ◽  
John A. Legault ◽  
Martin A. Bergmann
Keyword(s):  
Snow Cover ◽  
Light Attenuation ◽  
Open Water ◽  
Nutrient Status ◽  
Heat Of Fusion ◽  
Unfrozen Water ◽  
Total Heat Flow ◽  
Annual Cycles ◽  
Winter Snow ◽  
Heat Budgets

The annual cycles of temperature, ice and snow cover, and light are described for small Saqvaqjuac lakes (63°30′N). Summer thermal stratification occurred but was not persistent. Annual heat budgets were slightly higher than for temperate lakes and increased with increasing mean depth; latent heat of fusion constituted one half to one third of the total heat flow. Ice thickness reached a maximum of 1.6–2.2 m, depending upon winter snow cover, and a thin layer (≈5 cm) of white ice occurred in some years. Ice-out was a partial function of mean June temperature. The open-water season lasted 2–3 ms. Light attenuation through white and candled ice, snow, and water was measured. About 28% of the annual surface irradiance penetrated the unfrozen water, about half that which would have been absorbed under ice-free conditions. Extinction coefficients were inversely correlated with mean depth and positively correlated with nutrient status.

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