Search results for "dissolved"
showing 10 items of 240 documents
Trophic upgrading via the microbial food web may link terrestrial dissolved organic matter to Daphnia
2017
Direct consumption of allochthonous resources generally yields poor growth and reproduction in zooplankton, but it is still unclear how trophic upgrading of terrestrial dissolved organic matter (tDOM) via the microbial food web may support zooplankton. We compared survival, somatic growth and reproduction of Daphnia magna fed with the heterotrophic flagellate Paraphysomonas vestita and three algal diets. Paraphysomonas was fed lake bacteria that used tDOM as a substrate to simulate an allochthonous diet that zooplankton encounter in lakes. The highest survival, growth and reproduction was achieved with a diet of Cryptomonas, while Daphnia performance was the worst when fed Microcystis. Para…
The effects of different combinations of fixed and moving bed bioreactors on rainbow trout (Oncorhynchus mykiss) growth and health, water quality and…
2019
Abstract The effect of bioreactor design on nitrification efficiency has been well studied, but less is known about the overall impacts on water quality. Besides nitrification, submerged fixed bed bioreactors (FBBR) trap fine solid particles, whereas moving bed bioreactors (MBBR) grind solids, possibly increasing solids and particle accumulation in the system. In this experiment, the effects of different combinations of fixed bed and moving bed bioreactors on water quality, solids removal, particle size distribution, fish health based on histopathological changes and nitrification efficiency were studied in laboratory scale recirculating aquaculture systems (RAS) with rainbow trout (Oncorhy…
Taxonomic identity and phytoplankton diet affect fatty acid composition of zooplankton in large lakes with differing dissolved organic carbon concent…
2015
An increase in loading of dissolved organic carbon (DOC) from terrestrial to freshwater ecosystems has recently been documented in several boreal regions. We studied how transfer of important biomolecules, fatty acids, may be connected to DOC in pelagic food webs of large boreal lakes. We collected nine zooplankton taxa during three seasons from six lakes along a gradient of DOC (5–10 mg C L−1). Taxonomic identity explained 62% of the variation in zooplankton fatty acids, while the effects of DOC and season were less pronounced. This suggests that the community composition of zooplankton is important in determining the quality of food available for higher trophic level consumers. Seasonal d…
The Impact of Climate Change on Lakes in Northern Europe
2009
In Northern Europe, most lakes are characterized by extended periods of winter ice cover, high spring inflow from snow melt and brown water produced by the transport of dissolved organic carbon (DOC) from the surrounding catchments. In this chapter, the potential impact of climate change on the dynamics of these lakes is addressed by: (i) Describing the historical responses of the lakes to changes in the weather. (ii) Summarizing the results of modelling studies that quantify the impact of future changes in the climate on the lakes and the surrounding catchments. Many existing water quality problems could well be exacerbated by the effects of climatic change. It is therefore important to as…
Selective incorporation of dissolved organic matter (DOM) during sea ice formation
2013
This study investigated the incorporation of DOM from seawater into >2 day-old sea ice in tanks filled with seawater alone or amended with DOM extracted from the microalga, Chlorella vulgaris. Optical properties, including chromophoric DOM (CDOM) absorption and fluorescence, as well as concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved carbohydrates (dCHOs) and dissolved uronic acids (dUAs) were measured. Enrichment factors (EFs), calculated from salinity-normalized concentrations of DOM in bulk ice, brine and frost flowers relative to under-ice water, were generally >1. The enrichment factors varied for different DOM fractions: EFs were the lowest fo…
Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw
2019
Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO 2 ) and methane (CH 4 ) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near-natural conditions. We monitored GHG flux dynamics via high-resolution…
Lake browning impacts community structure and essential fatty acid content of littoral invertebrates in boreal lakes
2021
AbstractMany lakes in the northern hemisphere are browning due to increasing concentrations of terrestrial dissolved organic carbon (DOC). The consequences of lake browning to littoral invertebrates, however, are not fully understood. We analyzed community structure and fatty acid (FA) profiles of littoral invertebrates in humic (DOC-rich) and clear-water lakes in Eastern Finland. We found higher abundance of chironomids (Diptera: Chironomidae) in humic compared to clear-water lakes, whereas stoneflies (Plecoptera) and mayflies (Ephemeroptera: Baetidae) were more abundant in clear-water lakes. Taxon explained 65% of the differences in the FA composition of littoral invertebrates. However, t…
Oxygen and carbon isoscapes for the Baltic Sea : Testing their applicability in fish migration studies
2017
Conventional tags applied to individuals have been used to investigate animal movement, but these methods require tagged individuals be recaptured. Maps of regional isotopic variability known as “isoscapes” offer potential for various applications in migration research without tagging wherein isotope values of tissues are compared to environmental isotope values. In this study, we present the spatial variability in oxygen (δ18OH2O) and dissolved inorganic carbon (δ13CDIC) isotope values of Baltic Sea water. We also provide an example of how these isoscapes can reveal locations of individual animal via spatial probability surface maps, using the high-resolution salmon otolith isotope data fr…
Whole-Lake Sugar Addition Demonstrates Trophic Transfer of Dissolved Organic Carbon to Top Consumers
2017
Terrestrial dissolved organic carbon (DOC) provides an external carbon source to lake ecosystems. However, there is ongoing debate about whether external DOC that enters a lake can pass up the food web to support top consumers. We show, from experimental manipulation of a whole lake, that externally loaded DOC can contribute appreciably to fish biomass. Monthly additions of cane sugar with a distinct carbon stable isotope value during 2 years rapidly enriched the 13C content of zooplankton and macroinvertebrates, with a more gradual 13C enrichment of fish. After sugar addition stopped, the 13C content of consumers reverted towards original values. A simple isotope mixing model indicated tha…
Lake zooplankton delta13C values are strongly correlated with the delta13C values of distinct phytoplankton taxa
2016
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