Search results for "TOP"

Food-web structure and mercury dynamics in a large subarctic lake following multiple species introductions

2016

Summary The rate of non-native fish introductions into freshwater ecosystems has more than doubled during the past three decades, posing a serious threat to native biodiversity. Despite potential benefits for fisheries, little is known about how introduced species interact with native communities at the food-web level, or impact energy transfer dynamics and accumulation of contaminants in lake ecosystems. Here, we explored the trophic structure of a large, oligotrophic subarctic lake and assessed the trophic niche use and potential ecosystem-wide consequences of two introduced salmonid species: piscivorous lake trout (Salvelinus namaycush) and zooplanktivorous vendace (Coregonus albula). We…

Chironomid incorporation of methane-derived carbon in plankton- and macrophyte-dominated habitats in a large shallow lake

2018

1. While 13 C-depleted carbon derived from biogenic methane can substantially contribute to the benthic secondary production in deep stratified lakes, its role in shallow lakes is less clear. We investigated the dynamics of δ13 C and δ15 N in the larvae of Chironomus plumosus throughout an annual cycle in two ecologically distinct basins (open-water plankton-dominated and sheltered macrophyte- covered) of a large (270 km2 ), shallow, polymictic and eutrophic lake (Võrtsjärv, Estonia, North Europe). The larval stable isotopic compositions were linked to the presence of methane-oxidising bacteria (MOB) in larval guts and sediments. 2. Molecular detection of MOB revealed their presence in vari…

How to reach optimal estimates of confidence intervals in microscopic counting of phytoplankton?

2021

Abstract Present practices in the microscopic counting of phytoplankton to estimate the reliability of results rely on the assumption of a random distribution of taxa in sample preparations. In contrast to that and in agreement with the literature, we show that aggregated distribution is common and can lead to over-optimistic confidence intervals, if estimated according to the shortcut procedure of Lund et al. based on the number of counted cells. We found a good linear correlation between the distribution independent confidence intervals for medians and those for parametric statistics so that 95% confidence intervals can be approximated by using a correction factor of 1.4. Instead, the rec…

Migration strategies of brown trout (Salmo trutta) in a subarctic river system as revealed by stable isotope analysis

2018

We estimated the proportions of anadromous and freshwater‐resident brown trout (Salmo trutta) in different parts of the subarctic River Näätämöjoki/Neidenelva system (Finland and Norway) using carbon, nitrogen and hydrogen stable isotope analyses of archived scales as identifiers of migration strategy. Our results showed that carbon stable isotope values were the best predictor of migration strategy. Most individuals fell into two clearly distinct groups representing anadromous (47%) or freshwater‐resident (42%) individuals, but some fish had intermediate carbon values suggesting repeated movement between freshwater and the sea. The proportion of anadromous individuals decreased steadily wi…

The cork viewed from the inside

2015

International audience; Cork is the natural material stripped from the outer bark of cork oak. It is still the most used stopper to seal wine bottles and to preserve wine during storage. Cork stoppers are sorted in different classes according to apparent defects, named lenticels, which can be related to the cork macroporosity. The more lenticels there are, the worst cork quality is. The present work aims at investigating defects analysis of cork stoppers from two classes by comparing images recorded by digital photography and neutron imaging. Surface analysis of defects obtained from photography leads to more surface defects in class 4 (6.7%) than in class 0 (4.1%). Neutron radiography and …

Phytoplasmosis of bioenergy cultures

2018

The current state of biofuel distribution in EU, USA and Ukraine and its perspectives, new alternative sources of renewable energy, advantages and disadvantages of their use have been analyzed in this review. The concept growing of energy cultures in Ukraine has been described. Prospects for the use of bioenergy cultures of the 2nd generation have been considered. Particular attention has been paid to advantages and peculiarities of growing cultures with high potential of productivity - willow and poplar. The role of phytoplasmas in plant pathology has been considered; the pathways of distribution of plant phytoplasmosis, their localization in plant-host cells, typical symptoms of plants af…

Editorial: Changing Plankton Communities: Causes, Effects and Consequences

2019

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…

Eutrophication and browning influence Daphnia nutritional ecology

2019

Climate change and land-use practices can enhance lake eutrophication and browning, which influence phytoplankton composition by decreasing the availability of food high in nutritional quality (algae) and increasing the abundance of low-quality food (terrestrial detritus, bacteria) for herbivorous zooplankton. Nutritionally valuable algae for zooplankton are rich in essential biomolecules such as amino acids, polyunsaturated fatty acids (PUFAs), sterols, and phosphorus. We performed laboratory experiments and showed a stronger positive relationship between zooplankton (Daphnia) cumulative offspring number and availability of high-quality algae (Cryptophytes: Rhodomonas/Cryptomonas; and Chry…

Lake zooplankton delta13C values are strongly correlated with the delta13C values of distinct phytoplankton taxa

2016

Article