pinecone/core-2020-05-10-deduplication huggingface dataset:
The effect of periphyton on the light environment and production of Potamogeton perfoliatus L. in the mesotrophic basin of Lake Balaton

Light within the littoral zone affects the productivity and interaction between periphyton and its\ud
macrophyte substrate. The effect of periphyton on macrophyte photosynthesis, seasonal variation\ud
and vertical distribution of periphyton on artificial substrates (plastic strips), and the effect of\ud
periphyton on the light environment was studied in Lake Balaton.\ud
Data showed that an average of 4.1±0.4 mg (dry weight) cm-2 of periphyton had accumulated on\ud
the plastic strips after 8.8±0.4 days. This biomass corresponded to 294±30 μg m-2 chl-a of\ud
epiphytic algae and blocked 92.3±0.8 % of the depth specific radiation.\ud
Seasonal variation and specific vertical distribution of periphyton were observed. The most active\ud
time of periphyton accumulation corresponded to spring up until mid-June. Later in the year, the\ud
amount of periphyton significantly decreased. The optimal conditions for periphyton accumulation\ud
were at 30-40 cm depth.\ud
Most of the light reaching the adaxial leaf surface was attenuated by periphyton, decreasing the\ud
production of Potamogeton perfoliatus by 60-80%. This increased the importance of backscattered\ud
light that corresponded to 10-15% of the macrophyte production.\ud
A smaller part of the periphyton consisted of precipitated inorganic material, while epiphytic\ud
algae, making up the majority of the periphyton, were connected to both benthic (dominantly benthic penales) and pelagic (very close seasonal dynamics of pelagic and epiphytic biomass)\ud
algae. Periphyton affects macrophyte production especially in spring and in the upper water layers\ud
even in a mesotrophic water body. This increases the importance of the light absorbed through the\ud
abaxial side of the leaf and confirm the role of periphyton in transition from clear to turbid water\ud
states
Effect of experimental and seasonal warming on litter decomposition in a temperate stream

Litter decomposition, a fundamental ecosystem
process in woodland streams, is potentially affected by the
predicted increase in water temperature. Here, we assessed
the effects of experimental and seasonal warming on oak
litter decomposition and on the relative contributions of
microbes and invertebrates to this process. Experimental
warming (*3  C) stimulated litter decomposition in the
coldest, but not in the warmest, months. This may be
attributed to (1) higher temperature sensitivity of decomposition
at lower ambient temperature due to temperature
limitation of enzymatic activity, (2) higher relative temperature
increase in winter than in warmer months, (3) existence
of a previous warming period in winter, and (4) stronger
stimulation of the activity of detritivores by warming in
winter due to the prevalence of earlier (smaller) instars than
in warmer months. The low response of litter decomposition
to warming may have been due to the low nutrient availability
in the study stream. The 30-day litter decomposition
was stimulated over the seasonal gradient (monthly mean
temperature: 6–16  C), which may be attributed to a stimulation
of metabolic activities by warming and to changes in
detritivore life history over the seasons. The stimulation of
litter decomposition with temperature suggests that the rate
of CO2 release from freshwaters will increase under global
warming. However, invertebrate-driven litter decomposition
was more responsive to warming than microbial-driven litter
decomposition, suggesting that a larger fraction of litter
carbon may be converted into secondary production and
stored in the system for longer periods.This study was partially financed by the Institute
of Marine Research (IMAR), the European Fund for Economic and
Regional Development (FEDER) through the Program Operational
Factors of Competitiveness (COMPETE), and National Funds
through the Portuguese Foundation of Science and Technology (FCT)
under the project ‘‘Predicting the effect of global warming on stream
ecosystems’’ (PTDC/CLI/67180/2006; FCOMP-01-0124-FEDER-
007112). Financial support granted by the FCT to VF (SFRH/BPD/
34368/2006 and SFRH/BPD/76482/2011, program POPH/FSE) is
gratefully acknowledged
Photosynthetic pigment changes and adaptations in biofilms in response to flow intermittency

14 páginas, 5 figuras, 2 tablas.Among the environmental factors affecting\ud
benthic algae and cyanobacteria in streams, the one often\ud
producing the largest effects is flow intermittency. This\ud
study aimed to characterize the responses of algal assemblages\ud
to flow intermittency in a Mediterranean\ud
intermittent stream during the drying, non-flow (112 days),\ud
and rewetting phases. Algae growing in the epilithic,\ud
epipsammic and hyporheic streambed compartments were\ud
analyzed for pigment composition, and for the existence of\ud
structural changes in cells. Chlorophyll-a concentrations\ud
decreased between 60 to 90 % during the non-flow phase,\ud
indicating low resistance of algal assemblages to desiccation.\ud
In contrast, fast recoveries of Chlorophyll-a when\ud
flow resumed indicated high resilience. Pigment composition\ud
revealed that the epilithic algal assemblage was\ud
considerably different than the epipsammic and hyporheic\ud
ones. These differences were mainly attributed to the\ud
physical conditions prevailing on each streambed compartment\ud
that allowed the growth of different algal\ud
assemblages. During the non-flow phase, the synthesis of\ud
protective carotenoids (i.e. echinenone and scytonemin)\ud
and the occurrence of cell resistance structures (i.e.\ud
enlarged membrane thickness and resistant spores)\ud
enhanced resistance of the epilithic biofilm. The resistance\ud
observed in the epilithic biofilm might also be related to the\ud
tightly adhered growth-form of algae on this substratum.\ud
Main results suggest that algal assemblages in the epilithic\ud
compartment, which were the most exposed to desiccation,\ud
were structurally and functionally better adapted to flow\ud
interruption than those colonizing other streambed compartments,\ud
and that this compartment plays a crucial role in\ud
maintaining ecosystem functions under varying flow\ud
periods.Xisca Timoner was recipient of a PhD\ud
fellowship from the Spanish Ministry of science and technology (AP-\ud
2007-01945), and Teresa Buchaca was partially supported by the\ud
Spanish Government project Invasive fish (427/2011). This research\ud
was funded by the projects SCARCE (CONSOLIDER-INGENIO\ud
CSD2009-00065), and CARBONET (CGL2011-30474-C02-01) of\ud
the Spanish Ministry of Science and Innovation.Peer reviewe
Angling baits and invasive crayfish as important trophic subsidies for a large cyprinid fish

Invasive species and anthropogenic sources of allochthonous trophic subsidies can have substantial eco-logical
consequences for freshwater ecosystems, including modifying the diet of consumers and altering food web structure. Here,
the diet of an omnivorous cyprinid fish, European barbel Barbus barbus, was assessed in relation to the presence of
invasive signal crayfish Pacifastacus le-niusculus and pelletized fish-meal in four rivers in England. Pellets are often used
in large quantities by river anglers and thus could provide an important trophic subsidy, not only to the fish but also
indirectly via P. leniusculus. Carbon and nitrogen stable isotopes were used to estimate the proportion of diet assimilated
from natural sources and from P. leniusculus and pellets by B. barbus of lengths between 420 and 800 mm. Pellets
generally made a large contribution to the overall biomass of B. barbus (up to 59 % of population diet) and in the two rivers
where they were present, P. leniusculus were also an important resource (up to 30 % of population diet). The proportion
derived from macro-invertebrates (excluding P. leniuscu-lus) was substantially lower. Stable isotope mixing models further
demonstrated considerable intraspecific variability in B. barbus diet within the rivers, with pellets comprising up to 79 % of
the biomass of individual B. barbus in rivers where P. leniusculus was absent. Where present, P. le-niusculus effectively
replaced and thus reduced the contribution of pellets to individual fish diet. Thus, isotopic evidence from three of the four
rivers indicates that B. barbus populations are heavily reliant ([50 %) upon angler-introduced baits that act as an important
allochtho-nous subsidy and will also prey upon invasive P. leniusculus where they are present.http://link.springer.com/journal/272016-01-31hb201
The use of remote sensing to characterise hydromorphological properties of European rivers

Remote sensing (RS) technology offers unparalleled opportunities to explore river systems using RADAR, multispectral, hyperspectral, and LIDAR data. The accuracy reached by these technologies recently has started to satisfy the spatial and spectral resolutions required to properly analyse the hydromorphological character of river systems at multiple scales. Using the River Hierarchical Framework (RHF) as a reference we describe the state-ofthe- art RS technologies that can be implemented to quantify hydromorphological characteristics at each of the spatial scales incorporated in the RHF (i.e. catchment, landscape unit, river segment, river reach, sub-reach - geomorphic and hydraulic units). We also report the results of a survey on RS data availability in EU member states that provides the basis for a discussion on the current potential to derive RHF hydromorphological indicators from high-resolution multispectral images and topographic LiDAR at the national scale across Europe. This paper shows that many of the assessment indicators proposed by the RHF can be already derived by different RS sources and existing methodologies, and that EU countries have sufficient RS data at present to already begin their incorporation into hydromorphology assessment and monitoring, as mandated by WFD, which so far have been insufficiently addressed by the member states due to the demanding efforts it would require. With cooperation and planning, RS data can form a fundamental component of hydromorphological assessment and monitoring in the future to help support the effective and sustainable management of rivers, and this would be done most effectively through the establishment of multi-purpose RS acquisition campaigns and the development of shared and standardized hydromorphological RS databases updated regularly through planned resurveyed campaigns.JRC.H.1-Water Resource
The role of waterborne carbon in the greenhouse gas balance of drained and re-wetted peatlands

Accounting for greenhouse gas (GHG) emissions and removals in managed ecosystems has generally focused on direct land-atmosphere fluxes, but in peatlands a significant proportion of total carbon loss occurs via fluvial transport. This study considers the composition of this ‘waterborne carbon’ flux, its potential contribution to GHG emissions, and the extent to which it may change in response to land-management. The work describes, and builds on, a methodology to account for major components of these emissions developed for the 2013 Wetland Supplement of the Intergovernmental Panel on Climate Change. We identify two major components of GHG emissions from waterbodies draining organic soil: i) ‘on site’ emissions of methane (and to a lesser extent CO2) from drainage ditches located within the peatland; and ii) ‘off site’ emissions of CO2 resulting from downstream oxidation of dissolved and particulate organic carbon (DOC and POC) within the aquatic system. Methane emissions from ditches were found to be large in many cases (mean 60 g CH4 m-2 yr-1 based on all reported values), countering the view that methane emissions cease following wetland drainage. Emissions were greatest from ditches in intensive agricultural peatlands, but data were sparse and showed high variability. For DOC, the magnitude of the natural flux varied strongly with latitude, from 5 g C m-2 yr-1 in northern boreal peatlands to 60 g C m-2 yr-1 in  tropical peatlands. Available data suggest that DOC fluxes increase by around 60% following drainage, and that this increase may be reversed in the longer-term through re-wetting, although variability between studies was high, especially in relation to re-wetting response. Evidence regarding the fate of DOC is complex and inconclusive, but overall suggests that the majority of DOC exported from peatlands is converted to CO2 through photo- and/or bio-degradation in rivers, standing waters and oceans. The contribution of POC export to GHG emissions is even more uncertain, but we estimate that over half of exported POC may eventually be converted to CO2. Although POC fluxes are normally small, they can become very large when bare peat surfaces are exposed to fluvial erosion. Overall, we estimate that waterborne carbon emissions may contribute about 1 to 4 t CO2-eq ha-1 yr-1 of additional GHG emissions from drained peatlands. For a number of worked examples this represented around 15 to 50% of total GHG emissions
Sub-daily rates of degradation of fluvial carbon from a peat headwater stream.

In-stream processing of allochthonous dissolved organic carbon (DOC) and particulate organic carbon (POC) in peat-sourced headwaters has been shown to be a significant part of the terrestrial carbon cycle, through photo- and bio-degradation, with both DOC and POC converted to carbon dioxide (CO2). This study reports a series of 70-h, in situ experiments investigating rates of degradation in unfiltered surface water from a headwater stream in the River Tees, North Pennines, UK. Half the samples were exposed to the normal day/night cycle (ambient); half were continuously dark. The study found that the DOC concentration of samples in the ambient treatment declined by 64 % over the 70 h, compared with 6 % decline for the samples kept in the dark. For POC, the loss in the ambient treatment was 13 %. The average initial rate of loss of DOC in the ambient treatment during the first day of the experiment was 3.36 mg C/l/h, and the average rate of photo-induced loss over the whole 70 h was 1.25 mg C/l/h. Scaling up these losses, the estimate of total organic carbon loss from UK rivers to the atmosphere is 9.4 Tg CO2/year which would be 0.94 % of the global estimate of CO2 emissions from streams and rivers from the 2013 IPCC report. Initial rate kinetics in the light were as high as 3rd order, but the study showed that no single rate law could describe the whole diurnal degradation cycle and that separate rate laws were required for night and day processes. The comparison of dark and ambient treatment processes showed no evidence of photo-stimulated bacterial degradation
The greenhouse gas (GHG) emissions associated with aquatic carbon removal during drinking water treatment

Peatlands and other terrestrial ecosystems export large amounts of dissolved organic carbon (DOC) to freshwater ecosystems. In catchments used for supplying drinking water, water treatment works (WTWs) can remove large quantities of this organic matter, and can therefore play a unique modifying role in DOC processing and associated greenhouse gas (GHG) emissions within the fluvial system. During this study we quantified the GHG emissions due to processes associated with carbon (C) removal during water treatment at four contrasting WTWs in the UK. Our results demonstrate that the removal of DOC from raw water supplies via coagulation, leading to the formation of sludge, usually makes it less susceptible to short-term oxidation when compared to DOC remaining in the fluvial system. Although this could be considered a means of reducing CO2 emissions from waterborne carbon, the current practise of land spreading of sludge is unlikely to represent a long-term C sink and therefore water treatment probably only delays the rate at which fluvial C re-enters the  atmosphere. Furthermore, we estimate that indirect CO2  missions resulting from electricity use during water treatment, together with the use of chemicals and CO2 degassing from the water during treatment, far outweigh any potential CO2 reductions associated with DOC removal. Thus, the post-treatment handling of sludge has the potential to mitigate, but not to negate, GHG emissions associated with water treatment processes
Transformations in DOC along a source to sea continuum; impacts of photo-degradation, biological processes and mixing

Peatlands export significant amounts of dissolved organic carbon (DOC) to freshwaters, but the quantity of DOC reaching marine environments is typically less than the input to the fluvial system due to processing within the water column. Key removal processes include photo-chemical degradation, and heterotrophic bacterial respiration. In this study we examined these processes using 14C-labelled DOC to quantify the extent of DOC breakdown and to determine its fate following irradiation under controlled laboratory conditions. We examined the influence of microbial processes occurring within the water column, the potential role of stream-bed biofilms, and the possible modifying effects of downstream mixing, as DOC in water from the peatland encounters runoff from upland mineral soils (“Mountain”), nutrient-rich runoff from agricultural soils, and seawater in an estuary. Our results demonstrated conservative mixing of DOC from Peatland and Mountain waters but interactive effects when Peatland water was mixed with Agricultural and Estuary waters and exposed to solar radiation. The mixing of Peatland and Agricultural waters led to net DOC production, suggesting that DOC was only partially degraded by solar radiation and that the products of this might have fuelled autotrophic microbial growth in the samples. The mixing of Peatland water with saline estuary water resulted in net DOC loss following irradiation, suggesting a role for sunlight in enhancing the flocculation of DOC to particulate organic carbon (POC) in saline environments
Controls on the processing and fate of terrestrially-derived organic carbon in aquatic ecosystems: synthesis of special issue

This special issue brought together a complementary set of\ud
studies describing the range of processes affecting the\ud
cycling and fate of terrigenous organic matter within\ud
aquatic systems. It focuses in particular on headwater\ud
streams, and on peat catchments as major global sources of\ud
freshwater dissolved organic matter and of particulate organic matter in areas of peat erosion. This work is placed within the wider context of processes\ud
occurring in forested and agricultural headwaters, larger\ud
river systems and estuaries, and in a policy context in\ud
relation to national-scale carbon fluxes, the treatment of\ud
organic matter in drinking water supplies and the inclusion\ud
of aquatic carbon in international greenhouse gas\ud
accounting
Nitrous oxide and methane seasonal variability in the epilimnion of a large tropical meromictic lake (Lake Kivu, East-Africa)

We report a data-set of monthly vertical profiles obtained from January 2012 to October 2013, from the surface to 70 m depth of nitrous oxide (N2O) and dissolved methane (CH4) in Lake Kivu, a large and deep meromictic tropical lake (East Africa). Vertical variations of N2O were modest, with ranges of 6--9 and 0--16 nmol L−1 in surface and bottom waters, respectively, and occasionally peaks of N2O (up to 58 nmol L−1) were observed at the oxic-anoxic interface. On the contrary, steep vertical gradients of CH4 were observed with values changing several orders of magnitude from surface (19--103 nmol L−1) to 70 m (113,000--520,000 nmol L−1). Seasonal variations of CH4 were caused by annual cycles of mixing and stratification, during the dry and rainy seasons, respectively. This mixing allowed the establishment of a thick oxic layer (maximum 65 m deep), leading to decreased CH4 concentrations (minimum of 8 nmol L−1), presumably due to bacterial CH4 oxidation. During the stratification period, the oxic mixed layer was thinner (minimum 25 m deep), and an increase of CH4 concentrations in surface waters was observed (maximum of 103 nmol L−1), probably due to a lower integrated CH4 oxidation on the water column. Lake Kivu seasonally alternated between a source and a sink for atmospheric N2O, but on an annual scale was a small source of N2O to the atmosphere (on average 0.43 \textmumol m−2 day−1), while it was a small source of CH4 to the atmosphere throughout the year (on average 86 \textmumol m−2 day−1). Vertical and seasonal variations of N2O are discussed in terms of nitrification and denitrification, although from the present data-set it is not possible to unambiguously identify the main drivers of N2O production.Peer reviewe
Longitudinal connectivity loss in a riverine network: accounting for the likelihood of upstream and downstream movement across dams

Disruption of longitudinal connectivity is a major concern in most of the world¿s rivers. Approaches based on graph theory have proven to be a suitable tool for analysing functional connectivity. However, previous applications of graph-based connectivity methods to river systems have been oversimplified in that they have treated potential barriers as binary features and rivers as symmetric networks. We here apply a network analytical approach in which (a) upstream and downstream connectivity are considered so that fish passability values across dams are asymmetrical, and (b) it is possible to consider a continuous range of passability values for every dam. We build on previous and widely used connectivity metrics (Probability of Connectivity, PC), which here are generalised and adapted toward that end. We compare the results of our approach with those that would be obtained under the more simplified assumptions of symmetric movement and of barriers as binary features. We want to prove if there are substantial differences between considering or not the asymmetry in river networks. The application of symmetrical and asymmetrical PC highlights major differences between the upstream connectivity versus the downstream connectivity. We provide our methods in a free software package so that they can be used in any other application to riverscapes. We expect to provide a better graph-based approach for the prioritisation of the removal or permeabilization of artificial obstacles as well as for the preservation of target river segments for connectivity conservation and restoration