scholarly journals Decreased snow cover stimulates under ice primary producers, but impairs methanotrophic capacity

2018 ◽  
Author(s):  
Sarahi L Garcia ◽  
Anna J. Szekely ◽  
Christoffer Bergvall ◽  
Martha Schattenhofer ◽  
Sari Peura
Keyword(s):  
Primary Production ◽  
Snow Cover ◽  
Water Column ◽  
Photosynthetic Bacteria ◽  
Methane Emissions ◽  
Climate Change Scenarios ◽  
Light Penetration ◽  
Microbial Composition ◽  
Forest Lakes ◽  
Chlorophyll A And B

AbstractClimate change scenarios anticipate decrease of spring snow cover in boreal and subarctic regions. Forest lakes are abundant in these regions and substantial contributors of methane emissions. We performed an experiment on an anoxic frozen lake and observed that the removal of snow increased light penetration through the ice into the water modifying the microbial composition across depths. A shift in photosynthetic primary production was reflected by the increase of chlorophyll a and b concentrations in the upper depths of the water column, while Chlorobia, one of the key photosynthetic bacteria in anoxic lakes, shifted to lower depths. Moreover, a decrease in abundance of methanotrophs, such as Methylococcaceae, was noted concurrently to an increase in methane concentration in the water column. These results indicate that decrease of snow cover impacts both primary production and methane production/consumption, ultimately leading to increased methane emissions after spring ice off.

scholarly journals Decreased Snow Cover Stimulates Under-Ice Primary Producers but Impairs Methanotrophic Capacity

mSphere ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Sarahi L. Garcia ◽  
Anna J. Szekely ◽  
Christoffer Bergvall ◽  
Martha Schattenhofer ◽  
Sari Peura
Keyword(s):  
Climate Change ◽  
Snow Cover ◽  
Water Column ◽  
Relative Abundance ◽  
Heterotrophic Bacteria ◽  
Methane Emissions ◽  
Boreal Lakes ◽  
Climate Change Scenarios ◽  
Primary Producers ◽  
Microbial Composition

ABSTRACT Climate change scenarios anticipate decreased spring snow cover in boreal and subarctic regions. Forest lakes are abundant in these regions and substantial contributors of methane emissions. To investigate the effect of reduced snow cover, we experimentally removed snow from an anoxic frozen lake. We observed that the removal of snow increased light penetration through the ice, increasing water temperature and modifying microbial composition in the different depths. Chlorophyll a and b concentrations increased in the upper water column, suggesting activation of algal primary producers. At the same time, Chlorobiaceae, one of the key photosynthetic bacterial families in anoxic lakes, shifted to lower depths. Moreover, a decrease in the relative abundance of methanotrophs within the bacterial family Methylococcaceae was detected, concurrent with an increase in methane concentration in the water column. These results indicate that decreased snow cover impacts both primary production and methane production and/or consumption, which may ultimately lead to increased methane emissions after spring ice off. IMPORTANCE Small lakes are an important source of greenhouse gases in the boreal zone. These lakes are severely impacted by the winter season, when ice and snow cover obstruct gas exchange between the lake and the atmosphere and diminish light availability in the water column. Currently, climate change is resulting in reduced spring snow cover. A short-term removal of the snow from the ice stimulated algal primary producers and subsequently heterotrophic bacteria. Concurrently, the relative abundance of methanotrophic bacteria decreased and methane concentrations increased. Our results increase the general knowledge of microbial life under ice and, specifically, the understanding of the potential impact of climate change on boreal lakes.

Primary Productivity of Southern Indian Lake before, during, and after Impoundment and Churchill River Diversion

1984 ◽  
Vol 41 (4) ◽  
pp. 591-604 ◽  
Author(s):  
R. E. Hecky ◽  
S. J. Guildford
Keyword(s):  
Light Intensity ◽  
Primary Production ◽  
Water Column ◽  
Primary Productivity ◽  
Phosphorus Deficiency ◽  
Light Environment ◽  
Phytoplankton Production ◽  
Light Penetration ◽  
The Mean ◽  
Chlorophyll Concentrations

The primary productivity of seven regions of Southern Indian Lake and neighboring Wood Lake was measured during open-water seasons from 1974 to 1978. The lake had regional differences in chlorophyll concentrations and daily rates of integral primary production in 1974 and 1975 prior to impoundment of the lake. Regions receiving Churchill River flow tended to have higher chlorophyll concentrations and production rates than those regions marginal to the flow. Impoundment of the lake resulted in higher efficiencies of primary production in all regions, as indicated by higher light-saturated rates of carbon uptake per unit chlorophyll and by higher initial slopes of the hyperbolic light response relation of the phytoplankton. Many large basins of the lake had light penetration reduced by high concentrations of suspended sediment from eroding shorelines, while other areas had relatively unchanged light penetration. The increased efficiency of carbon fixation per unit chlorophyll resulted in higher rates of integral production in those regions where light penetration was not greatly affected. Daily rates of integral primary production in lake regions where light penetration had decreased markedly were not significantly different after impoundment because efficiencies of light utilization were higher. Comparison of the mean water column light intensities for those turbid regions with the values of Ik (light intensity at the onset of light saturation) for phytoplankton indicated that these turbid regions are now light deficient on average. Phosphorus deficiency, as indicated by alkaline phosphatase activity per unit ATP, which was present before impoundment, has been eliminated as the mean water column light intensity declined below 5 mEinsteins∙m−2∙min−1. The light environment of a new reservoir can be a significant determinant of integral production, and predicting the consequences of impoundment on phytoplankton production requires accurate prediction of the light environment.

scholarly journals Genomes of Novel Microbial Lineages Assembled from the Sub-Ice Waters of Lake Baikal

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Pedro J. Cabello-Yeves ◽  
Tamara I. Zemskaya ◽  
Riccardo Rosselli ◽  
Felipe H. Coutinho ◽  
Alexandra S. Zakharenko ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Snow Cover ◽  
Water Column ◽  
Lake Baikal ◽  
Light Penetration ◽  
Freshwater Lakes ◽  
The Baltic Sea ◽  
Content Type ◽  
Freshwater Bodies ◽  
The Baltic

ABSTRACT We present a metagenomic study of Lake Baikal (East Siberia). Two samples obtained from the water column under the ice cover (5 and 20 m deep) in March 2016 have been deep sequenced and the reads assembled to generate metagenome-assembled genomes (MAGs) that are representative of the microbes living in this special environment. Compared with freshwater bodies studied around the world, Lake Baikal had an unusually high fraction of Verrucomicrobia. Other groups, such as Actinobacteria and Proteobacteria, were in proportions similar to those found in other lakes. The genomes (and probably cells) tended to be small, presumably reflecting the extremely oligotrophic and cold prevalent conditions. Baikal microbes are novel lineages recruiting very little from other water bodies and are distantly related to other freshwater microbes. Despite their novelty, they showed the closest relationship to genomes discovered by similar approaches from other freshwater lakes and reservoirs. Some of them were particularly similar to MAGs from the Baltic Sea, which, although it is brackish, connected to the ocean, and much more eutrophic, has similar climatological conditions. Many of the microbes contained rhodopsin genes, indicating that, in spite of the decreased light penetration allowed by the thick ice/snow cover, photoheterotrophy could be widespread in the water column, either because enough light penetrates or because the microbes are already adapted to the summer ice-less conditions. We have found a freshwater SAR11 subtype I/II representative showing striking synteny with Pelagibacter ubique strains, as well as a phage infecting the widespread freshwater bacterium Polynucleobacter. IMPORTANCE Despite the increasing number of metagenomic studies on different freshwater bodies, there is still a missing component in oligotrophic cold lakes suffering from long seasonal frozen cycles. Here, we describe microbial genomes from metagenomic assemblies that appear in the upper water column of Lake Baikal, the largest and deepest freshwater body on Earth. This lake is frozen from January to May, which generates conditions that include an inverted temperature gradient (colder up), decrease in light penetration due to ice, and, especially, snow cover, and oligotrophic conditions more similar to the open-ocean and high-altitude lakes than to other freshwater or brackish systems. As could be expected, most reconstructed genomes are novel lineages distantly related to others in cold environments, like the Baltic Sea and other freshwater lakes. Among them, there was a broad set of streamlined microbes with small genomes/intergenic spacers, including a new nonmarine Pelagibacter-like (subtype I/II) genome.

Seasonal variation of water-column light utilization efficiency for primary production in Saroma-ko Lagoon

2021 ◽  
pp. 1-9
Author(s):  
Akihiro Shiomoto ◽  
Yushi Kamuro
Keyword(s):  
Seasonal Variation ◽  
Primary Production ◽  
Water Column ◽  
Fresh Water ◽  
Utilization Efficiency ◽  
Commercial Activity ◽  
The Sustainable Development ◽  
Light Utilization Efficiency ◽  
Light Utilization ◽  
Sunlight Intensity

Abstract In Saroma-ko Lagoon, where scallop aquaculture is a thriving commercial activity, monitoring primary production is essential for determining the amount of scallops that can be farmed. Using the primary production data obtained so far, we calculated Ψ, an index of water-column light utilization efficiency, and clarified its seasonal variation. Ψ tended to be lower in the spring bloom season (February–April), and higher in the late autumn to winter (October–December). Low chlorophyll-normalized production, an index of growth rate, resulted in lower values, while low daily irradiance resulted in higher values. The values of Ψ from our study had a range of 0.05–1.42 gC gChl-a−1 mol photons−1 m2 (N = 56). These values were within the previously reported range of 0.07–1.92 (gC gChl-a−1 mol photons−1 m2) for seawater and fresh water worldwide. Therefore, it is likely that Ψ varies from 0.05–2 gC gChl-a−1 mol photons−1 m2, being affected by conditions of phytoplankton growth and sunlight intensity, regardless of whether samples are collected from seawater or fresh water. Using the median Ψ value of 0.45 gC gChl-a−1 mol photons−1 m2 obtained in this study, primary production was 0.3–3.5 times the actual production at Saroma-ko Lagoon. Using this method, primary production can be easily and constantly monitored, facilitating the sustainable development of scallop aquaculture.

scholarly journals Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

2015 ◽  
Vol 12 (5) ◽  
pp. 1561-1583 ◽  
Author(s):  
M. Hagens ◽  
C. P. Slomp ◽  
F. J. R. Meysman ◽  
D. Seitaj ◽  
J. Harlay ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Primary Production ◽  
Water Column ◽  
Bottom Water ◽  
Substantial Reduction ◽  
Buffering Capacity ◽  
Total Alkalinity ◽  
Acid Base ◽  
Data Set ◽  
Ph Fluctuations

Abstract. Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light–dark incubations, in addition to sediment–water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air–sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment–water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid–base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid–base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

scholarly journals The silica-carbon biogeochemical cycle in the Bohai Sea and its responses to the changing terrestrial loadings

2016 ◽  
Author(s):  
Jun Liu ◽  
Lex Bouwman ◽  
Jiaye Zang ◽  
Chenying Zhao ◽  
Xiaochen Liu ◽  
...  
Keyword(s):  
Primary Production ◽  
Water Column ◽  
Yellow Sea ◽  
Bohai Sea ◽  
Critical Role ◽  
The Yellow Sea ◽  
Organic C ◽  
Riverine Input ◽  
The Bohai Sea ◽  
River Loads

Abstract. Silicon (Si) and carbon (C) play key roles in the river and marine biogeochemistry. The Si and C budgets for the Bohai Sea were established on the basis of measurements at a range of stations and additional data from the literature. The results show that the spatial distributions of reactive Si and organic C (OC) in the water column are largely affected by the riverine input, primary production and export to the Yellow Sea. Biogenic silica (BSi) and total OC in sediments are mainly from marine primary production. The major supply of dissolved silicate (DSi) comes from benthic diffusion, riverine input alone accounts for 17 % of reactive Si inputs to the Bohai Sea; the dominant DSi removal from the water column is diatom uptake, followed by sedimentation. Rivers contribute 47 % of exogenous OC inputs to the Bohai Sea; the dominant outputs of OC are sedimentation and export to the Yellow Sea. The net burial of BSi and OC represent 3.3 % and 1.0 % of total primary production, respectively. Primary production has increased by 10 % since 2002 as a result of increased river loads of DSi and BSi. Our findings underline the critical role of riverine Si supply in primary production in coastal marine ecosystems.

scholarly journals Snow Cover and Snow Persistence Changes in the Mocho-Choshuenco Volcano (Southern Chile) Derived From 35 Years of Landsat Satellite Images

2021 ◽  
Vol 9 ◽  
Author(s):  
Roberto O. Chávez ◽  
Verónica F. Briceño ◽  
José A. Lastra ◽  
Daniel Harris-Pascal ◽  
Sergio A. Estay
Keyword(s):  
Snow Cover ◽  
Satellite Images ◽  
Remote Sensing Data ◽  
Landsat Images ◽  
Microbial Composition ◽  
Mountain Areas ◽  
Pixel Resolution ◽  
Temperature Changes ◽  
Soil Microbial ◽  
Landsat Satellite

Mountain regions have experienced above-average warming in the 20th century and this trend is likely to continue. These accelerated temperature changes in alpine areas are causing reduced snowfall and changes in the timing of snowfall and melt. Snow is a critical component of alpine areas - it drives hibernation of animals, determines the length of the growing season for plants and the soil microbial composition. Thus, changes in snow patterns in mountain areas can have serious ecological consequences. Here we use 35 years of Landsat satellite images to study snow changes in the Mocho-Choshuenco Volcano in the Southern Andes of Chile. Landsat images have 30 m pixel resolution and a revisit period of 16 days. We calculated the total snow area in cloud-free Landsat scenes and the snow frequency per pixel, here called “snow persistence” for different periods and seasons. Permanent snow cover in summer was stable over a period of 30 years and decreased below 20 km2 from 2014 onward at middle elevations (1,530–2,000 m a.s.l.). This is confirmed by negative changes in snow persistence detected at the pixel level, concentrated in this altitudinal belt in summer and also in autumn. In winter and spring, negative changes in snow persistence are concentrated at lower elevations (1,200–1,530 m a.s.l.). Considering the snow persistence of the 1984–1990 period as a reference, the last period (2015–2019) is experiencing a −5.75 km2 reduction of permanent snow area (snow persistence > 95%) in summer, −8.75 km2 in autumn, −42.40 km2 in winter, and −18.23 km2 in spring. While permanent snow at the high elevational belt (>2,000 m a.s.l.) has not changed through the years, snow that used to be permanent in the middle elevational belt has become seasonal. In this study, we use a probabilistic snow persistence approach for identifying areas of snow reduction and potential changes in alpine vegetation. This approach permits a more efficient use of remote sensing data, increasing by three times the amount of usable scenes by including images with spatial gaps. Furthermore, we explore some ecological questions regarding alpine ecosystems that this method may help address in a global warming scenario.

scholarly journals Effects of temperature and organic pollution on nutrient cycling in marine sediments

2015 ◽  
Vol 12 (15) ◽  
pp. 4565-4575 ◽  
Author(s):  
C. Sanz-Lázaro ◽  
T. Valdemarsen ◽  
M. Holmer
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Nutrient Cycling ◽  
Water Column ◽  
Temperature Rise ◽  
Nutrient Release ◽  
Organic Pollution ◽  
Coastal Sediments ◽  
Effect Of Temperature ◽  
Climate Change Scenarios

Abstract. Increasing ocean temperature due to climate change is an important anthropogenic driver of ecological change in coastal systems. In these systems sediments play a major role in nutrient cycling. Our ability to predict ecological consequences of climate change is enhanced by simulating real scenarios. Based on predicted climate change scenarios, we tested the effect of temperature and organic pollution on nutrient release from coastal sediments to the water column in a mesocosm experiment. PO43− release rates from sediments followed the same trends as organic matter mineralization rates, increased linearly with temperature and were significantly higher under organic pollution than under nonpolluted conditions. NH4+ release only increased significantly when the temperature rise was above 6 °C, and it was significantly higher in organic polluted compared to nonpolluted sediments. Nutrient release to the water column was only a fraction from the mineralized organic matter, suggesting PO43− retention and NH4+ oxidation in the sediment. Bioturbation and bioirrigation appeared to be key processes responsible for this behavior. Considering that the primary production of most marine basins is N-limited, the excess release of NH4+ at a temperature rise > 6 °C could enhance water column primary productivity, which may lead to the deterioration of the environmental quality. Climate change effects are expected to be accelerated in areas affected by organic pollution.

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