Below is the protocol of the first experiment the 1000IRP has ran in 2015-2016.
The 1000 intermittent river experiment
Intermittent rivers and ephemeral streams (IRES, these rivers which stop flowing or dry up at some point in time and space) are prevalent in all climates and dominate river networks in many regions (Larned et al. 2010, Acuña et al. 2014, Datry et al. 2014a). For example, IRES represent 30-40% of the larger rivers and 69% of the low-order streams below 60° latitude (Raymond et al. 2013). Over the next century, the number and length of IRES will further increase due to climate and land-cover change, and increasing abstraction for public water supply, irrigation and other economic uses (Gleick & Palaniappan 2010, Döll & Schmied 2012, Steward et al. 2012).
Historically, IRES have been perceived to be outside of the scope of both terrestrial and aquatic sciences and therefore, have been overlooked by most disciplines (Larned et al. 2010). As a result, the persuasive conceptual developments in river research have been generated from and for perennial rivers and are poorly applicable to IRES (Datry et al. 2014a). But after years of near-obscurity, IRES research is now blooming, driven by increasing water scarcity issues, climate change effects, and the recognition that IRES are prevalent in river networks (Leigh et al. 2015). One of the most important and recent progresses has been the recognition that IRES are bio-geochemical reactors with a pulsed dynamic (Acuña & Tockner 2010, Larned et al. 2010, Von Schiller et al. 2011; 2015, Corti & Datry 2012, Datry et al. 2014a).
During dry phases, large quantities of coarse particulate organic matter (CPOM) accumulate over dry riverbeds or in stranding pools (Acuña & Tockner 2010, Datry et al. 2014a) while CPOM processing is considerably reduced (Gurtz & Tate 1988, Boulton 1991, Corti et al. 2011, Foulquier et al. 2015). However, environmental processes ranging from photodegradation to fermentation in stagnant, anoxic pools alter leaf condition and chemistry and mediate its further decomposition under perennial, fully aquatic conditions. (Datry et al. 2011, Dieter et al. 2011, 2013). When flow resumes, often in the form of spectacular “first-pulse” events (a video here: www.irstea.fr/datry), large quantities of pre-conditioned CPOM can be transported to downstream reaches, where they undergo further decomposition (Jacobson et al. 2000, Corti & Datry 2012, Rosado et al. 2014). Solutes and entrained CPOM at the leading edge of the flowing water can exceed baseflow concentrations by several orders of magnitude (Jacobson et al. 2000, Hladyz et al. 2011, Corti & Datry 2012). Deposited and processed CPOM can be an important carbon source for heterotroph consumers (Jacobson et al. 2000, Corti & Datry 2012, Rosado et al. 2014), but it can also cause hypoxic blackwater events and subsequent organism kills (Hladyz et al. 2011).
The recognition of the pulsed dynamic of IRES is based on reach-scale observations in a few rivers and its significance at the scale of river catchments is unknown. According to the prevalence of IRES within river networks, it is very likely that most global estimates of carbon and nutrient processing (e.g., Tranvik et al. 2009, Seitzinger et al. 2010, Battin et al. 2011) are inaccurate, along with the estimates of how much rivers contribute to carbon dioxide release (Raymond et al. 2013, Von Schiller et al. 2014, Datry et al. 2014b). It is thus timely to better quantify CPOM accumulation along dry riverbeds and understand the ecological significance of first pulse events, and no meta-analysis would ever achieve this due to the small amount of data available.
The objectives of this project are to 1) quantify CPOM accumulation over dry streambeds during dry periods in multiple IRES on the globe, 2) understand the main drivers of variation in CPOM quantity and quality, including flow regime components, 3) assess the ecological consequences of CPOM mobilization to downstream receiving waters. Based on a wide, international network of stream ecologists, this project aims at conducting simultaneous, very simple experiments on as many IRES as possible in 2015/2016 to cover a wide range of climates, river types, flow regimes and vegetation.
- Project schedule and details
The general principle is simple: we create a network of interested stream ecologists, we all spend a few time and little expenses for a simple and quick experiment. Pooled together, these individual experiments will generate a unique, compelling and timely dataset to address the objective above. In 3 words: united we stand.
The requirement of this project is to gather stream ecologists interested in IRES to work on multiple IRES: ideally, ~1 000, minimally > 100. A simple, cheap and time-efficient experiment carried out almost simultaneously and across a large number of IRES will provide a unique and outstanding dataset to explore. The rough quality of each single experiment, as well as the low amount of data individually generated will be largely compensated by the large number of IRES and the high consistency of the protocols used.
The first phase of the project will consist in creating this international network of volunteered stream ecologists. The second phase will be to collect data (CPOM and environmental variables) on individual IRES in a consistent and simple procedure (see below). The third phase will be to ship a subsample of the collected material, to IRSTEA where they will be consistently processed. The fourth and last phase will be to analyze the data and write the associated paper(s), targeting a high-profile journal.
- Outputs and benefices for the participants
This experiment will lead to:
-the redaction of at least one paper targeting a high-profile journal on the significance of the pulse nature of IRES. Each participant of the project (one / lab) will be invited to be a co-author on the paper(s).
-the creation of an international network of river ecologists interested in the ecology and biogeochemistry of IRES. This network will continue to develop further common experiments and paper writing, will seek for international sources of funding and will be helpful for national/regional funding sources. Participants will also meet whenever possible at international conferences (e.g., SFS, ESA, SEFS, ASLO).
- Experimental design and protocol
The general design is to:
- before the dry period, select 1-2 IRES (of course, more if you can/want, there are no upper limits) you know or have been studied before (in case of braided rivers, please, contact us for adapting the protocol). If possible, prioritize the selection of the 1-2 IRES based on the existence of flow gauging stations nearby (within the IRES or the catchment, at a distance < 200 km) with long-term hydrological time-series available.
- select one representative reach per IRES. The reach length will be defined as 10 times the average active channel to ensure consistent sampling effort across IRES and have a representative area. The active channel is defined here as the area of inundated and exposed bed sediments between established edges of perennial, terrestrial vegetation and abrupt changes in slope.
- measure the environmental variable required (see below)
- during the dry period, collect the CPOM falling in the dry active channel in a standardized way (see below).
- back to the lab, separate the leaves from other wooden materials (e.g. branches) and weight the 2 fractions separately (to the nearest g)
- dry and mold the leaves to obtain 3 subsamples, randomly selected, of 20g each (to the nearest g)
- ship these 3 subsamples (see below)
- Environmental variables to collect
At the catchment scale:
Stream order, stream length, distance to source, distance to downstream main confluence, distance to the closest flow recorder, number of active flow recorders in the catchment, catchment areas, climate zone (Koppen system, http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification), landscape uses (forest, agricultural lands….), % of the network being intermittent (estimations).
At the reach scale:
Active channel width, substrate type (silt/sand/gravel/cobble/boulder/bedrock), riparian cover (estimated visually as a %), riparian vegetation (absent/herbs/shrubs/trees), estimates of the drying period duration and timing, type of drying (flow cessation with dried riffles and persistent disconnected pools, or complete drying), X, Y (in WSG84) and altitude (m asl).
- Collecting OM
The collection of CPOM can be done once or several times during the dry period, depending on its length. Typically, if the dry period is <2 months, one collection date will be sufficient. For longer dry periods, additional collection dates may be needed. In any cases, CPOM needs to be collected before the flow resumption, and the time during which CPOM had accumulated (collection dry period) estimated.
At each collection date, estimate the area of the selected reach (length * average active channel width). Then, calculate the surface from which you need to collect CPOM to sample ~5% of the reach surface using 4 m² quadrats. For example, for a stream with an active channel of 10 m, the reach will be 10*10= 100 m long and has a surface of 1000 m2, indicating 4-5 sampling sites of 4 m2 (2*2 m) will be required.
Then collect the CPOM from these sampling sites which you place semi-randomly across the active channel, with half of them in the center of the channel and the other half on the margins of the active channel. Leaves can be collected by hands or with a rake and stored in plastic bags. Wooden material has to be stored separately.
- Processing CPOM
Dry the leaves and the wooden material in a dry oven for 12 hours at 40°C.
Pool all leaves together and weight them (g precision).
Pool all the wooden material together and weight it (g precision).
Mold the leaves to obtain fine particles.
Prepare 3 subsamples of 20g each of dried, molded leaves.
Store the leftover and the wooden material in a dark room.
- Shipping CPOM
Ship the 3 subsamples of dried molded leaves using FEDEX or DHL (they accept non-contaminant scientific samples) to Datry T, specifying the address and contact of both the senders and the receiver:
IRSTEA, 5 rue de la Doua
CS70077 69626 VILLEURBANNE Cedex
In case of questions or comments, please contact Thibault Datry (firstname.lastname@example.org, Skype: thibault.datry, tel + 33 22.214.171.124.55
- Further analyses done at IRSTEA
1) DO declines/CO2 release to measure microbial respiration induced by CPOM (using one standard inoculum)
2) DOC leaching, measurement and characterization using SUVA 254 nm for assessing quality
3) C/N ratio measurement
4) AFDM measurement
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