scholarly journals Under-ice mesocosms reveal the primacy of light but the importance of zooplankton in winter phytoplankton dynamics

2019 ◽  
Author(s):  
Allison R. Hrycik ◽  
Jason D. Stockwell
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Food Webs ◽  
Soluble Reactive Phosphorus ◽  
Open Water ◽  
Light Environment ◽  
Zooplankton Grazing ◽  
Ice Dynamics ◽  
Reactive Phosphorus

AbstractFactors that regulate planktonic communities under lake ice may be vastly different than the open-water season. However, under-ice food webs in temperate lakes are poorly understood, despite expected changes in light availability, ice cover, and snowfall associated with climate change. We hypothesized that light limitation (bottom-up control) outweighs zooplankton grazing (top-down control) on phytoplankton biovolume and community structure under ice in a north temperate lake. Using in situ under-ice mesocosms, we found that light had stronger effects on phytoplankton abundance than zooplankton, as expected. Specifically, low light limited growth of diatoms, cryptophytes, chrysophytes, and chlorophytes. Zooplankton, however, also significantly affected phytoplankton by decreasing diatoms and cryptophytes, in contrast to the common assumption that zooplankton grazing has negligible effects under ice. Ammonia and soluble reactive phosphorus decreased in high light treatments presumably through uptake by phytoplankton, whereas ammonia and soluble reactive phosphorus increased in high zooplankton treatments, likely through excretion. In situ experimental studies are commonly applied to understand food web dynamics in open-water conditions, but are extremely rare under ice. Our results suggest that changes in the light environment under ice have significant, rapid effects on phytoplankton growth and community structure and that zooplankton may play a more active role in winter food webs than previously thought. Changes in snow and ice dynamics associated with climate change may alter the light environment in ice-covered systems and significantly influence community structure.

Hypolimnetic Aeration: An Overview

1986 ◽  
Vol 21 (2) ◽  
pp. 205-217 ◽  
Author(s):  
D.J. McQueen ◽  
D.R.S. Lean
Keyword(s):  
Ammonia Volatilization ◽  
Cold Water ◽  
Soluble Reactive Phosphorus ◽  
Eutrophic Lakes ◽  
Hypolimnetic Oxygen ◽  
Dissolved Hydrogen ◽  
Phosphorus Sedimentation ◽  
Reactive Phosphorus ◽  
Maximum Removal

Abstract Hypolimnetic aerators are now being widely used throughout Europe and are beginning to appear in small and medium sized eutrophic lakes in temperate North America. This activity has produced approximately 42 published reports dealing with experiments conducted at 16 lakes. Taken together, the evidence from these experiments suggests that well designed aerators do not cause significant destratification or warming of hypolimnetic water, but do result in measurable Increases in hypolimnetic oxygen concentration and decreases in dissolved hydrogen sulfide, methane and ammonia. Early experiments suggested that phosphorus sedimentation was unpredictable, but recent work has demonstrated that when the ratio of total iron to soluble reactive phosphorus exceeds 10:1 and pH is < 7.5, phosphorus sedimentation is assured and internal loading greatly reduced. Early experiments also showed that ammonia volatilization was unpredictable, but at pH > 8.0, ammonia volatilization will occur. Because both phosphorus sedimentation and nitrogen reduction are pH dependent, both cannot be optimally removed during the same period of time and so the experimenter is advised to select for the maximum removal of one or the other through pH manipulation. Hypolimnetic aeration induces oxygen consumption and this must be considered when choosing an appropriate compressor size. Most studies show little impact on phytoplankton blomass, but one recent experiment showed that aeration during spring turnover resulted in reduced concentrations of chlorophyll a and TP. Zooplankton populations are, for the most part, unaffected and a number of American studies have shown that hypolimnetically aerated lakes can support cold water fish populations. The aggregate practical and experimental experience suggests that well designed hypolimnetic aeration systems yield measurable improvements in water quality and will almost certainly prove to be one of the major methods used for future in situ lake restoration.

Assessment of sediment and porewater after one year of subaqueous capping of contaminated sediments in Hamilton Harbour, Canada

1998 ◽  
Vol 37 (6-7) ◽  
pp. 323-329 ◽  
Author(s):  
José M. Azcue ◽  
Alex J. Zeman ◽  
Alena Mudroch ◽  
Fernando Rosa ◽  
Tim Patterson
Keyword(s):  
Soluble Reactive Phosphorus ◽  
Coarse Sand ◽  
Contaminated Sediments ◽  
Overlying Water ◽  
Hamilton Harbour ◽  
Vertical Fluxes ◽  
Reactive Phosphorus ◽  
One Year ◽  
In Situ Capping

In this manuscript, we present data from a demonstration in situ capping site (100 m × 100 m) in Hamilton Harbour, Lake Ontario, Canada. A layer of clean medium to coarse sand with the average thickness of 35 cm was placed at the site in the summer of 1995. Concentration of Zn, Cr, and Cd in the original sediments reached values over 6000, 300 and 15 μg/g, respectively. The predicted consolidation of the uppermost one meter of sediment was about 14 cm, which was in good agreement with values obtained from comparisons of moisture content values of pre-capping and post-capping cores. A thin layer of fresh moderately contaminated sediments has started to develop on the top of the cap. In general, the concentrations of elements were greater in porewater than in the overlying water, e.g., the concentration of Fe and soluble reactive phosphorus were 1000 times, and those of Mn 100 times greater. There was a significant reduction in the vertical fluxes of all the trace elements after the capping of the contaminated sediments.

scholarly journals Environmental drivers of plankton protist communities along latitudinal and vertical gradients in the oldest and deepest freshwater lake

2020 ◽  
Author(s):  
Gwendoline M. David ◽  
David Moreira ◽  
Guillaume Reboul ◽  
Nataliia V. Annenkova ◽  
Luis J. Galindo ◽  
...  
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Microbial Community ◽  
Lake Baikal ◽  
Latitudinal Gradient ◽  
Biotic Interactions ◽  
Open Water ◽  
Freshwater Lake ◽  
Significant Difference ◽  
Vertical Gradients

SummaryIdentifying which abiotic and biotic factors determine microbial community assembly is crucial to understand ecological processes and predict how communities will respond to environmental change. While global surveys aim at addressing this question in the world’s oceans, equivalent studies in large freshwater systems are virtually lacking. Being the oldest, deepest and most voluminous freshwater lake on Earth, Lake Baikal offers a unique opportunity to test the effect of horizontal versus vertical gradients in community structure. Here, we characterized the structure of planktonic microbial eukaryotic communities (0.2-30 µm cell size) along a North-South latitudinal gradient (∼600 km) from samples collected in coastal and pelagic waters and from surface to the deepest zones (5-1400 m) using an 18S rRNA gene metabarcoding approach. Our results show complex and diverse protist communities dominated by alveolates (ciliates and dinoflagellates), ochrophytes and holomycotan lineages, with cryptophytes, haptophytes, katablepharids and telonemids in moderate abundance and many low-frequency lineages, including several typical marine members, such as diplonemids, syndinians and radiolarians. Depth had a strong significant effect on protist community stratification. By contrast, the effect of the latitudinal gradient was marginal and no significant difference was observed between coastal and surface open water communities. Co-occurrence network analyses showed that epipelagic communities are much more interconnected than meso- and bathypelagic communities and suggest specific biotic interactions between autotrophic, heterotrophic and parasitic lineages that influence protist community structure. Since climate change is rapidly affecting Siberia and Lake Baikal, our comprehensive protist survey constitutes a useful reference to monitor ongoing community shifts.Originality and Significance StatementLake Baikal is the oldest, deepest and most voluminous freshwater lake on Earth, offering a unique opportunity to test the effects of horizontal versus vertical gradients on microbial community structure. Using a metabarcoding approach, we studied planktonic microbial eukaryotes from Baikal water columns (5 up to 1,400 m depth) across a North-South latitudinal gradient (∼600 km), including coastal and pelagic areas. Our results show that depth has a strong effect on protist community assemblage, but not latitude (minor effect) or coastal vs. open water sites (no effect). Co-occurrence analyses also point to specific biotic interactions as drivers of community structure. This comprehensive survey constitutes a useful reference for monitoring active climate change effects in this ancient lake.

Assessing the contributions to the phosphorus load delivered to lake Iseo.  

2021 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Michael Hupfer ◽  
Daniele Nizzoli
Keyword(s):  
Climate Change ◽  
Pore Water ◽  
Climate Change Scenario ◽  
Soluble Reactive Phosphorus ◽  
Change Scenario ◽  
High Temporal Resolution ◽  
Combined Sewer Overflows ◽  
Deep Basin ◽  
Nutrient Sources ◽  
Reactive Phosphorus

<p>Lake Iseo is a 256-m deep basin which underwent a dramatic deterioration of water quality since the 80ies, to the point that it now shows the most worrying environmental conditions of all the deep lake in northern Italy, with anoxia and 160 μg/l of total phosphorus (TP) below 100 m. In this lake, a permanent chemical stratification has established, preventing deep mixing and trapping the larger part of the incoming TP in the monimolimnion. The increase in air temperature foreseen for the Iseo watershed will further enhance the stability of the water column and further reduce the efficiency of the outflow in the removal of TP.  In order to rationally guide future choices of remediation strategies, a quantification of the main sources of external and internal TP load to the lake is thus essential.</p><p>At this purpose, in the period 2016-2019 the research project ISEO (Improving the lake Status from Eutrophy towards Oligotrophy) was developed, comprising field monitoring, laboratory and experimental activities. The contribution of the main watershed (covering about 80% of the whole drained area) was quantified as 111 tonns TP/year, by measuring the TP concentration at high temporal resolution in main tributary through a bank-side auto-analyser. These measurements revealed that about 50% of this load is generated by acute, storm-dependent events, in which high TP concentrations in particulate form are delivered to the lake over short periods. The contribution of the combined sewer overflows (CSO) was quantified as 7 tonns TP/year, by coupling an hydraulic model of the sewer system along the shore of the lake with the measurements of the nutrients discharged in wet periods through the sewer spillways of 3 representative CSOs. This load was foreseen to increase by 10% in a climate change scenario with amplified intense storms. With regard to the internal load, soluble reactive phosphorus (SRP) fluxes were determined across the sediment–water interface from centimetre-scale pore water SRP concentration profiles using passive pore water samplers in 3 different lake locations. The average monimolimnion-wide flux was thus established 28.7 tonns SRP/year. Interestingly, the size and speciation of the phosphorus-bearing sediment fractions at each station revealed that the available mobile TP in the sediment under the monimolimnion was only 45 tonns, so able to sustain the actual release for only ~ 1.6 years without constant renewal. These data allowed to address the current contribution of the different nutrient sources to the TP budget in lake Iseo, and to argue about their possible temporal evolution and distribution in the lake in a climate change scenario.</p>

Dissolved oxygen and temperature best predict deep-sea fish community structure in the Gulf of California with climate change implications

2020 ◽  
Vol 637 ◽  
pp. 159-180
Author(s):  
ND Gallo ◽  
M Beckwith ◽  
CL Wei ◽  
LA Levin ◽  
L Kuhnz ◽  
...  
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Community Composition ◽  
Environmental Conditions ◽  
Deep Sea ◽  
Gulf Of California ◽  
Fish Community ◽  
Demersal Fish ◽  
Fish Community Structure ◽  
Explained Variance

Natural gradient systems can be used to examine the vulnerability of deep-sea communities to climate change. The Gulf of California presents an ideal system for examining relationships between faunal patterns and environmental conditions of deep-sea communities because deep-sea conditions change from warm and oxygen-rich in the north to cold and severely hypoxic in the south. The Monterey Bay Aquarium Research Institute (MBARI) remotely operated vehicle (ROV) ‘Doc Ricketts’ was used to conduct seafloor video transects at depths of ~200-1400 m in the northern, central, and southern Gulf. The community composition, density, and diversity of demersal fish assemblages were compared to environmental conditions. We tested the hypothesis that climate-relevant variables (temperature, oxygen, and primary production) have more explanatory power than static variables (latitude, depth, and benthic substrate) in explaining variation in fish community structure. Temperature best explained variance in density, while oxygen best explained variance in diversity and community composition. Both density and diversity declined with decreasing oxygen, but diversity declined at a higher oxygen threshold (~7 µmol kg-1). Remarkably, high-density fish communities were observed living under suboxic conditions (<5 µmol kg-1). Using an Earth systems global climate model forced under an RCP8.5 scenario, we found that by 2081-2100, the entire Gulf of California seafloor is expected to experience a mean temperature increase of 1.08 ± 1.07°C and modest deoxygenation. The projected changes in temperature and oxygen are expected to be accompanied by reduced diversity and related changes in deep-sea demersal fish communities.

USING FOOD WEBS TO UNDERSTAND THE EFFECTS OF BIOTIC INVASION ON LATE ORDOVICIAN MARINE COMMUNITY STRUCTURE

2017 ◽  
Author(s):  
Hannah L. Kempf ◽  
◽  
Ian O. Castro ◽  
Carrie L. Tyler ◽  
Ashley A. Dineen ◽  
...  
Keyword(s):  
Community Structure ◽  
Food Webs ◽  
Late Ordovician ◽  
Biotic Invasion ◽  
Marine Community

scholarly journals Elevated temperature and browning increase dietary methylmercury, but decrease essential fatty acids at the base of lake food webs

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pianpian Wu ◽  
Martin J. Kainz ◽  
Fernando Valdés ◽  
Siwen Zheng ◽  
Katharina Winter ◽  
...  
Keyword(s):  
Climate Change ◽  
Fatty Acids ◽  
Organic Matter ◽  
Food Webs ◽  
Essential Fatty Acids ◽  
Trophic Levels ◽  
Climate Change Scenarios ◽  
Essential Nutrients ◽  
Aquatic Food Webs ◽  
Aquatic Food

AbstractClimate change scenarios predict increases in temperature and organic matter supply from land to water, which affect trophic transfer of nutrients and contaminants in aquatic food webs. How essential nutrients, such as polyunsaturated fatty acids (PUFA), and potentially toxic contaminants, such as methylmercury (MeHg), at the base of aquatic food webs will be affected under climate change scenarios, remains unclear. The objective of this outdoor mesocosm study was to examine how increased water temperature and terrestrially-derived dissolved organic matter supply (tDOM; i.e., lake browning), and the interaction of both, will influence MeHg and PUFA in organisms at the base of food webs (i.e. seston; the most edible plankton size for zooplankton) in subalpine lake ecosystems. The interaction of higher temperature and tDOM increased the burden of MeHg in seston (< 40 μm) and larger sized plankton (microplankton; 40–200 μm), while the MeHg content per unit biomass remained stable. However, PUFA decreased in seston, but increased in microplankton, consisting mainly of filamentous algae, which are less readily bioavailable to zooplankton. We revealed elevated dietary exposure to MeHg, yet decreased supply of dietary PUFA to aquatic consumers with increasing temperature and tDOM supply. This experimental study provides evidence that the overall food quality at the base of aquatic food webs deteriorates during ongoing climate change scenarios by increasing the supply of toxic MeHg and lowering the dietary access to essential nutrients of consumers at higher trophic levels.

scholarly journals Metagenome-assembled genomes infer potential microbial metabolism in alkaline sulphidic tailings

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Wenjun Li ◽  
Xiaofang Li
Keyword(s):  
Community Structure ◽  
Mine Tailings ◽  
Fluorescent In Situ Hybridization ◽  
High Throughput Sequencing ◽  
Microbial Consortia ◽  
Metabolic Reconstruction ◽  
Metal Release ◽  
Community Members ◽  
Oxidative Stresses

Abstract Background Mine tailings are hostile environment. It has been well documented that several microbes can inhabit such environment, and metagenomic reconstruction has successfully pinpointed their activities and community structure in acidic tailings environments. We still know little about the microbial metabolic capacities of alkaline sulphidic environment where microbial processes are critically important for the revegetation. Microbial communities therein may not only provide soil functions, but also ameliorate the environment stresses for plants’ survival. Results In this study, we detected a considerable amount of viable bacterial and archaeal cells using fluorescent in situ hybridization in alkaline sulphidic tailings from Mt Isa, Queensland. By taking advantage of high-throughput sequencing and up-to-date metagenomic binning technology, we reconstructed the microbial community structure and potential coupled iron and nitrogen metabolism pathways in the tailings. Assembly of 10 metagenome-assembled genomes (MAGs), with 5 nearly complete, was achieved. From this, detailed insights into the community metabolic capabilities was derived. Dominant microbial species were seen to possess powerful resistance systems for osmotic, metal and oxidative stresses. Additionally, these community members had metabolic capabilities for sulphide oxidation, for causing increased salinity and metal release, and for leading to N depletion. Conclusions Here our results show that a considerable amount of microbial cells inhabit the mine tailings, who possess a variety of genes for stress response. Metabolic reconstruction infers that the microbial consortia may actively accelerate the sulphide weathering and N depletion therein.

scholarly journals Application of an improved surface energy balance model to two large valley glaciers in the St. Elias Mountains, Yukon

2020 ◽  
pp. 1-16
Author(s):  
Tim Hill ◽  
Christine F. Dow ◽  
Eleanor A. Bash ◽  
Luke Copland
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Energy Balance ◽  
Shortwave Radiation ◽  
Balance Model ◽  
Landsat 8 ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Surface Melt

Abstract Glacier surficial melt rates are commonly modelled using surface energy balance (SEB) models, with outputs applied to extend point-based mass-balance measurements to regional scales, assess water resource availability, examine supraglacial hydrology and to investigate the relationship between surface melt and ice dynamics. We present an improved SEB model that addresses the primary limitations of existing models by: (1) deriving high-resolution (30 m) surface albedo from Landsat 8 imagery, (2) calculating shadows cast onto the glacier surface by high-relief topography to model incident shortwave radiation, (3) developing an algorithm to map debris sufficiently thick to insulate the glacier surface and (4) presenting a formulation of the SEB model coupled to a subsurface heat conduction model. We drive the model with 6 years of in situ meteorological data from Kaskawulsh Glacier and Nàłùdäy (Lowell) Glacier in the St. Elias Mountains, Yukon, Canada, and validate outputs against in situ measurements. Modelled seasonal melt agrees with observations within 9% across a range of elevations on both glaciers in years with high-quality in situ observations. We recommend applying the model to investigate the impacts of surface melt for individual glaciers when sufficient input data are available.

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