33 research outputs found
Streambed migration frequency drives ecology and biogeochemistry across spatial scales
The bed of fluvial ecosystems plays a major role in global biogeochemical cycles.
All fluvial sediments migrate and although responses of aquatic organisms to
such movements have been recorded there is no theoretical framework on how
the frequency of sediment movement affects streambed ecology and biogeochemistry.
We here developed a theoretical framework describing how the
moving-resting frequencies of fine-grained sediments constrain streambed communities
across spatial scales. Specifically, we suggest that the most drastic
impact on benthic and hyporheic communities will exist when ecological and
biogeochemical processes are at the same temporal scale as the sediment
moving-resting frequency. Moreover, we propose that the simultaneous occurrence
of streambed patches differing in morphodynamics should be considered
as an important driver of metacommunity dynamics. We surmise that the frequency
of patch transition will add new dimensions to the understanding of biogeochemical
cycling and metacommunities from micro-habitat to segment
scales. This theoretical framework is important for fluvial ecosystems with frequent
sediment movement, yet it could be applied to any other dynamic habitat.German Research Foundation joint funding
grant RI 2093/2-1 and MU 1464/7-1Carl Zeiss Foundation, P2021-00-004Israel Science
Foundation, grant 682/17),NSF-BSF joint funding grant EAR-1734300UK-Israel Science Fellowship Scheme 2018–2019Israeli Science Foundation, grant 944\2
Depth and vertical hydrodynamics constrain the size structure of a lowland streambed community
Abundance-body mass (N–M) relationships are prominent macroecological patterns and provide an integrated measurement of the structure and energy flow through natural communities. However, little is known about how N-M relationships are constrained by local environmental conditions. Here we quantify how sediment depth and direction of surface–groundwater exchange (vertical hydrodynamics), two major drivers of the streambed ecology, determine N-M scaling in a sandy lowland, European stream. Streambed assemblages included flagellates, ciliates, meiofauna and macroinvertebrates, and spanned five orders of magnitude in body mass. We detected a significant interaction of body mass with depth and vertical hydrodynamics with a sharp reduction in N–M slopes in the hyporheic zone and under upwelling conditions. These results revealed that streambed assemblages become more size–structured as environmental constraints increase with direct implications for the metabolic capacity and functioning of the system
Long-term forecast of thermal mortality with climate warming in riverine amphipods
Forecasting long-term
consequences of global warming requires knowledge on thermal
mortality and how heat stress interacts with other environmental stressors on
different timescales. Here, we describe a flexible analytical framework to forecast
mortality risks by combining laboratory measurements on tolerance and field temperature
records. Our framework incorporates physiological acclimation effects,
temporal scale differences and the ecological reality of fluctuations in temperature,
and other factors such as oxygen. As a proof of concept, we investigated the heat
tolerance of amphipods Dikerogammarus villosus and Echinogammarus trichiatus in the
river Waal, the Netherlands. These organisms were acclimated to different temperatures
and oxygen levels. By integrating experimental data with high-resolution
field
data, we derived the daily heat mortality probabilities for each species under different
oxygen levels, considering current temperatures as well as 1 and 2°C warming
scenarios. By expressing heat stress as a mortality probability rather than a upper
critical temperature, these can be used to calculate cumulative annual mortality, allowing
the scaling up from individuals to populations. Our findings indicate a substantial
increase in annual mortality over the coming decades, driven by projected
increases in summer temperatures. Thermal acclimation and adequate oxygenation
improved heat tolerance and their effects were magnified on longer timescales.
Consequently, acclimation effects appear to be more effective than previously recognized
and crucial for persistence under current temperatures. However, even in
the best-case
scenario, mortality of D. villosus is expected to approach 100% by
2100, while E. trichiatus appears to be less vulnerable with mortality increasing to
60%. Similarly, mortality risks vary spatially: In southern, warmer rivers, riverine animals
will need to shift from the main channel toward the cooler head waters to avoid
thermal mortality. Overall, this framework generates high-resolution
forecasts on
how rising temperatures, in combination with other environmental stressors such as
hypoxia, impact ecological communities.ANID PIA/BASAL FB0002Fondo
Nacional de Desarrollo Científico y
Tecnológico, Grant/Award Number:
1211113Ministerio de Ciencia e
Inovación, Grant/Award Number: Juan
de la Cierva-formación
FellowshipNederlandse Organisatie voor
Wetenschappelijk Onderzoek, Grant/
Award Number: 016.161.32
Environmental filtering and community delineation in the streambed ecotone
Abstract A current controversy in ecology is whether biological communities are discrete biological entities or simply study units created for convenience; a debate that becomes even more heated when delimiting communities along ecotones. Here, we report an interdisciplinary study designed to address the interplay between environmental drivers and community ecology in a typical ecotone ecosystem: the streambed. Environmental filtering at a micro-scale determined how diversity, productivity and composition of the whole streambed assemblage varied with depth and with the direction of vertical water exchange. Biomass and production decreased with increasing depth, and were lower under upwelling than downwelling conditions. However, the rate at which biomass and production decreased with increasing depth differed significantly for different taxonomic groups. Using quantitative biocenosis analysis, we also showed that benthic and hyporheic zone assemblages (assemblages in close juxtaposition) could be clearly distinguished as discrete communities with individual integrity. Vertical hydrodynamic conditions also influenced the demarcation between both communities; the benthic community reached greater depths in downwelling than in upwelling zones
Drought conditions disrupt atmospheric carbon uptake in a Mediterranean saline lake
Inland saline lakes play a key role in the global carbon cycle, acting as dynamic zones for atmospheric carbon exchange and storage. Given the global decline of saline lakes and the expected increase of periods of drought in a climate change scenario, changes in their potential capacity to uptake or emit atmospheric carbon are expected. Here, we conducted continuous measurements of CO2 and CH4 fluxes at the ecosystem scale in an endorheic saline lake of the Mediterranean region over nearly 2 years. Our focus was on determining net CO2 and CH4 exchanges with the atmosphere under both dry and flooded conditions, using the eddy covariance (EC) method. We coupled greenhouse gas flux measurements with water storage and analysed meteorological variables like air temperature and radiation, known to influence carbon fluxes in lakes. This extensive data integration enabled the projection of the net carbon flux over time, accounting for both dry and wet conditions on an interannual scale. We found that the system acts as a substantial carbon sink by absorbing atmospheric CO2 under wet conditions. In years with prolonged water storage, it is predicted that the lake's CO2 assimilation capacity can surpass 0.7 kg C m2 annually. Conversely, during extended drought years, a reduction in CO2 uptake capacity of more than 80 % is expected. Regarding CH4, we measured uptake rates that exceeded those of well-aerated soils such as forest soils or grasslands, reaching values of 0.2 µmol m−2 s−1. Additionally, we observed that CH4 uptake during dry conditions was nearly double that of wet conditions. However, the absence of continuous data prevented us from correlating CH4 uptake processes with potential environmental predictors. Our study challenges the widespread notion that wetlands are universally greenhouse gas emitters, highlighting the significant role that endorheic saline lakes can play as a natural sink of atmospheric carbon. However, our work also underscores the vulnerability of these ecosystem services in the current climate change scenario, where drought episodes are expected to become more frequent and intense in the coming years.</p
Winter is coming: food web structure and seasonality in a subtropical freshwater coastal-lake
Indexación: Web of Science; Scopus.Food web studies provide a useful tool to assess the organization and complexity of natural communities. Nevertheless, the seasonal dynamics of food web properties, their environmental correlates, and potential association with community diversity and stability remain poorly studied. Here, we condensed an incomplete 6-year community dataset of a subtropical coastal lake to examine how monthly variation in diversity impacts food web structure over an idealized time series for an averaged year. Phytoplankton, zooplankton, macroinvertebrates, and fish were mostly resolved to species level (n = 120 trophospecies). Our results showed that the seasonal organization of the food web could be aggregated into two clusters of months grouped here as ‘summer’ and ‘winter’. During ‘winter’, the food web decreases in size and complexity, with the number of trophospecies dropping from 106 to 82 (a 22.6% decrease in the number of nodes) and the trophic interactions from 1,049 to 637 between month extremes (a 39.3% drop in the number of links). The observed simplification in food web structure during ‘winter’ suggests that community stability is more vulnerable to the impact of any change during this period.http://onlinelibrary.wiley.com/doi/10.1002/ece3.3031/epd
Export and turnover of transparent exopolymer particles into the deep ocean
2nd Meeting of the Iberian Ecological Society (SIBECOL), XXI conference of the Iberian Association of Limnology (AIL) and 21st National Congress of the Portuguese Ecological Society (SPECO), 3-8 July 2022, AveiroAcidic polysaccharides released by phytoplankton and prokaryotic heterotrophs promote the formation of gel-like transparent exopolymer particles (TEPs). TEPs play a key role in the biological carbon pump due to their carbon-rich composition and their ability to coagulate and sink towards the deep ocean. Yet, very little is known about TEP distribution, export, and turnover at a global scale, particularly at deep ocean depths. We provide the first inventory of TEP from the surface up to 4000 m depth in the Atlantic, Indian, and Pacific Oceans and have assessed their contribution to carbon export into the deep ocean. Primary production determines TEP concentration above the deep chlorophyll maximum, and prokaryotic biomass also contributes in deeper waters. In the deep ocean waters, TEP concentrations are lower and mirror the concentrations in the surface, evidencing the importance of TEP sinking both at the export depth (200 m) with a global value of 2.9 Pg C year-1 and at the sequestration depth (1000 m) of 0.9 Pg C year-1 of particulate carbon. However, incubation experiments across ocean basins depicted rapid TEP turnover rates of 71 and 333 days (on average) within the export and sequestration depths, respectively. These findings reveal that the export of carbon by TEP sinking towards deep oceans escapes from long-term paths of the global carbon cycleN