1,721,073 research outputs found
Temporal and spatial differences of the under-ice microbiome are linked to light transparency and chlorophyll-a
Full text linkUnder-ice community dynamics are barely understood. Temporal and spatial studies are needed to fully understand the consequences of a declining ice cover on microbial biodiversity. Here, bacterial communities of different years (2015, 2017–2021) and layers (upper and lower euphotic layer, euphotic layer, hypolimnion) were assessed by Illumina sequencing of the 16S rRNA gene. Alpha- and beta-diversity of summer and under-ice hypolimnetic communities were similar, and a seasonal difference was found only when excluding summer hypolimnetic communities. Similarly, in non-metric multidimensional scaling (NMDS), summer and under-ice communities were different even though hypolimnetic communities were similar. Investigating under-ice conditions, the year 2017 showed highest under-ice light and chlorophyll-a while 2021 showed no under-ice light and lowest chlorophyll-a. Under-ice communities were not linked to layer differences implying that a spatial distinction under ice was less important than in summer, especially in years with little or no under-ice light. Most under-ice bacterial classes and ASVs showed direct and indirect dependencies on light availability and primary production. Similarly in NMDS with only under-ice communities, light transparency and primary production were important. In the future, ice conditions with less snow cover might lead to bacterial communities similar to that of high-light years (2017, 2018, 2020)
The under-ice microbiome, a five-year study at Lake Tovel
Full text linkLittle is known about changes in microbial abundance and community composition during
persistent ice cover of lakes. Here, the under-ice 16S rRNA diversity was assessed for different
pelagic layers and compared between years (2015, 2017, 2018, 2019, 2020) at Lake Tovel (1177 m
above sea level; Italy). Functional profiling of amplicon sequences variants (ASVs) was also done
with Piphillin. Environmental parameters (chemistry, temperature, light climate, oxygen
concentration) were linked to the observed diversity patterns. Despite relatively uniform
temperature and chemistry profiles, the pelagic and hypolimnetic microbiome of different years
were different as assessed by a Principal Coordinates Analysis. The under-ice light climate was a
driving factor of the observed differences and related to different precipitations patterns. These
results underline how a changing climate also influences life under ice
Light transparency and chlorophyll-a influence the temporal and spatial differences of the under-ice microbiome
No full textTaxonomic and functional diversity of rotifers, what do they tell us about community assembly?
No full textCommunity assembly depends on dispersal, environmental parameters, and species interactions. Here, we compared rotifer communities from two environmentally distinct, but connected basins of Lake Tovel for five years, with biweekly (2002) and monthly (2003-2006) sampling. We applied taxonomic and functional diversity-based multivariate analyses (principal components analysis, redundancy analysis) to compare rotifer communities in both basins. For functional diversity, we focused separately on defence and feeding traits that were inferred from rotifer morphology. Taxonomic and functional diversity were generally higher in the deep compared to the shallow basin. In multivariate analyses, water residence time and surface water temperature were important environmental predictors for both taxonomic and functional diversity while the importance of competitors and predators varied according to defence or feeding traits used. The difference between basins showed a gradient from taxonomic (marked difference) to functional diversity, indicating that the processes that regulate feeding traits were similar in both basins while those regulating defence traits were different. The distinction of different aspects of rotifer life (i.e. feeding and predation) outlined different important drivers that would have been neglected by focusing solely on species abundance. Furthermore, we outlined the status quo of trait research in rotifer ecology including its challenges and difficulties
Influence of temperature on swimming performance and respiration rate of the cold-water cyclopoid copepod Cyclops vicinus
No full textLittle is known on the swimming activity and respiration rate of the cyclopoid copepod Cyclops vicinus. Here, the swimming speed and respiration rate of C. vicinus were measured at different temperatures using a high speed (up to 1200 frames per second) camera and a closed-system respirometry, respectively. For cruise and escape swimming, log-linear relationships were found between temperature (range 1–22 °C) and duration, speed, and frequency of locomotor acts, respectively. The respiration rate of immobilized and active individuals showed log-linear relationships with temperature (range of 2–20 °C) and a thermal coefficient Q10 ≈ 2 was found. The maximum respiration rate of swimming females was 7.8 and 6.4 times higher than that of immobilized individuals at 2 and 20 °C, respectively. To better understand how temperature affects the energy efficiency of copepod swimming, the mechanical energy of movement was estimated from sswimming speed and the metabolic energy was estimated from the amount of oxygen consumed during swimming. Linear relationships between swimming speed and mechanical and metabolic energy, respectively, were found at all experimental temperatures. At 20 °C, the maximum mechanical and metabolic energy costs for movement was 15.2 × 10−5 and 37.7 × 10−4 J h−1, respectively. In the range of 2–20 °C, the mechanical energy attributed to swimming represented only a small portion (4.0–8.2%) of the total metabolic energy. Cold-water specialization probably limited the increase of the swimming speed of C. vicinus at high temperatures compared to that of warm-water adapted species
CO2 evolution in surface waters of Lake Tovel
Full text linkLake Tovel, a mountain lake (1177 m a.s.l.), is regularly samples during the ice-free season from 1995 onwards. Based on chemical data and the PhreeQC software, the CO2 content in the surface is calculated and the CO2 flux to the atmosphere is assessed. Lake Tovel shows considerable variability, coinciding with changing dissolved oxygen concentrations in the hypolimnion. Possible relationships will be discussed
Influence of egg sacs on the swimming performance of freshwater cyclopoid copepods
No full textFemale cyclopoid copepods carry their embryos in egg sacs that impact swimming performance until nauplii hatch. We studied kinematic parameters and mechanical energy of small routine jumps and large escape jumps of non-egg-carrying (NEC) and egg-carrying (EC) females of Mesocyclops leuckarti and Macrocyclops albidus. The drag and body acceleration costs for EC females of M. leuckarti and M. albidus during routine jumps were 28 and 40%, respectively, higher than those for NEC females moving at the same speed. Maintaining position in the water column by small jumps was more costly for EC females, requiring 2.2–2.3 times more jumps and energy. Consequently, the persistence of EC females was limited in the open water. In M. leuckarti and M. albidus, the average speed and distances of jumps were 5–6 and 1.5–2.2 times higher, respectively, and the duration of jumps was 2.2–2.5 times shorter during escape than routine swimming. The maximum jumping speeds of NEC females, 40.6 and 50.5 cm s−1, respectively, were 12–14% higher than those of EC females, whereas their power and cost of transport were 16 and 23% lower, respectively. These results clearly indicated that egg sacs impair swimming and increase energetic costs of movemen
A 40-year perspective of an alpine lake: is everything the same?
No full textMountain lakes are the most affected by climate change; however, few of these lakes are regularly sampled because of their remoteness. We discussed limnological data (e.g. water temperature, light transparency, and plankton diversity) of Lake Campo (1944 m above sea level, Adamello Mountains, Italy) scattered over almost forty years in the light of climate change. Specifically, occasional samplings in 1980, 1988, 2016, 2017, and 2018 and more extensive surveys in 1997 and 2015 were carried out. Among the investigated years, 2015 was the warmest. Inter-year variability in water temperature was quite marked in Lake Campo. Water temperature profiles of July (1980, 1997, 2015) showed increased surface warming, while the deeper layers (> 15 m) were always isothermal at around 5 ◦C. Hypolimnetic dissolved oxygen never decreased below 50 % saturation. Secchi disk depth was not substantially different among years. Summer profiles of light transparency showed discontinuous light attenuation, which was tentatively attributed to algae located in deeper layers. In cluster analysis of phytoplankton and zooplankton data, differences between seasons but not years were found. The autumn decline of Bacillariophyta and the increase of mixotrophic Cryptophyta was linked to decreasing silica concentrations towards autumn. Apart from this general pattern, several observations (e.g. high abundance of Tovellia sanguinea, requiring warmer temperatures and thermal stratification to compete with Bacillariophyta; a spatially extended metalimnetic oxygen maximum in July 2015) showed the effects of particularly warm conditions of 2015 compared to 1997. The continuous presence of crustacean males and first generation of rotifers (Polyarthra f. aptera) hatching from sexual eggs indicated the importance of sexual reproduction in the lake. Length measurements of Daphnia gr. longispina before (1997) and after (2015) non-native fish removal and Arctic char introduction were similar and indicated no apparent change in predation pressure. Studies like this, despite scattered data, can provide valuable insights into the changes mountain lakes undergo through tim
Inter-year and inter-season variability of zooplankton of a mountain lake with a special emphasis on under-ice communities
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