et al., 2005 ; Navel et al., 2011 ; Van de Bund et al., 1994 ) and oxygen consumption (Lagauzère
et al., 2009 ; Mermillod-Blondin et al., 2005 ).
Overall, bioturbation of bottom sediments at the sediment–water interface is currently gain- ing more attention in studies dealing with the functioning of aquatic ecosystems (Adámek and Maršálek, 2013). However, in the context of fish farming, the number of studies dealing with the contribution of tuficids to nutrients dynamics (especially phosphorus) is still scarce. Therefore, the objective of the present work was to determine (under laboratory conditions) the influence of natural assemblages of tubificid worms on nutrients translocation across the water-sediment interface of fish farm settling ponds. The potential contribution of bioturbation on minimizing the phosphorus discharged by fish farms settling ponds is also discussed.
To cite this version: Gilbert, Franck and Souchu, Philippe and Bianchi, Micheline and Bonin, Patricia Influence of shellfish farming activities on
nitrification, nitrate reduction to ammonium and denitrification at the water-sediment interface of the Thau lagoon, France. (1997) Marine
The current work investigated, for the first time, the degrada- tion of cyflumetofen in four soils and three water/sediment systems in China under aerobic and anaerobic conditions. The degradation dynamic of cyflumetofen followed first- order kinetics. The half-lives of cyflumetofen were <30 days in the four soils and three water/sediments under aerobic and anaerobic conditions. And under the different conditions for the same samples, in the black soil, krasnozem, fluvo-aquic soil, and Beijng Shangzhuang reservoir, there were significant differences (p < 0.05). For the metabolites, in soils, cyflumetofen degraded B-1 and B-3, from the first day 0.24 % B-1 was generated, while, only very low levels of B-3 generated at the same time. As time increased, B-3 grad- ually increased, cyflumetofen reduced gradually. Until 100 days, there were about 3.5 % B-1 and B-3 in the soils. In the water/sediment systems, from the first day, it degraded into B-1 in the sediment, and in the water mainly degraded into B-3. In the soil the B-1 and B-3 were generated faster than in water/sediment. Comprehensive soil and watersediment degradation behavior research has practical significance when evaluating its security according to the amount of cyflumetofen and its metabolites, B-1 and B-3. This research did not do studies of its metabolites about degradation, and further research is needed to clear the metabolites metabolic mechanism in the environmental. To provide the reference for related research.
CHAPTER 4 : Conclusion
From the established profiles, diffusional fluxes of copper, lead, zinc, nickel, cadmium, arsenic and thallium ions at the water-sediment interface were calculated. Comparison of duplicate peepers revealed an important spatial variability within each cell; these results emphasize the importance of obtaining an adequate number of replicates if cell-wide estimates of water-sediment fluxes are required. Observed fluxes are mostly negative, indicating a release of metals from the sediments to the water column, most are however quite low but contribute significantly (for Pb, Zn, Cd and Tl) to the global dissolved metal load incoming from the upstream cells. Sediment fluxes would be expected to reverse in direction if more reducing conditions appear in the sediments as the tailings age. Subsequent sampling in the years to come would be required to confirm such a scenario analytically.
Repeated field campaigns allowed to sample the water-sediment interface of the Thau Lagoon at sites C4 (8 m depth) and C5 (9 m water depth): in December 2001, April, July and August 2002, January and May 2003. Scuba divers recovered sediment cores, less to 20 cm in length, by using hand-driven tubes. Immediately after core retrieval, cores were carefully sliced each ½ cm by upward extrusion. Back to the lab, sediment samples were sieved at 63 µm and dried at 60°C. Then the uppermost sediment layers were measured for 234 Th and 7 Be determinations using a low background-high efficiency well type γ-detector . These measurements had to be completed within one month after sampling, due to the rapid decay of 234 Th. In fact, measurements of 234 Th are not available for few cores. Sediment layers were investigated downcore until the disappearance of 7 Be and a rather constant 234 Th activity was reached, which was considered as the supported activity. 238 U activities were determined by α counting after sediment digestion by a mixture of HF-HNO 3 -HClO 4 in presence of 232 U.
Clogging and Bacterial Compartment Developed on Sediments
The influence of clogging on bacteria developed on sediments was predominantly observed on the top sediment layer (0–2 cm) due to differences in sediment character- istics (particle size and OM content). The difference in colonisable area between fine and coarse sands (1,465.00± 33.17 and 59.37±0.34 cm 2 g −1 , respectively) may explain the higher bacterial abundances measured in the top layer of the clogged system in comparison with the unclogged one [ 34 , 55 , 56 ]. However, Nogaro et al. [ 47 ] did not detect any positive relationship between the proportion of fine sediments and the abundance of bacteria attached to sediments in French rivers (Usses, Drôme and Isère) impacted by fine sediment deposition. These authors suggested that fine sediment deposition did not affect bacterial abundances because it did not always increase the OM content of the sediment. Indeed, several studies [ 14 , 15 , 59 ] demonstrated that bacterial communities (biomass, production) developed on sediment depended on the quantity and lability of the OM. In the present study, bacterial abundances and potential aerobic respira- tion in the top layer of sediments (0–2 cm) were higher in the clogged than in unclogged systems because of a higher colonisable area for bacteria (×24.7) and a higher OM content (×17.1 for total organic carbon, ×7.8 for total nitrogen and ×1.9 for phosphorus) in fine than in coarse sand.
Roupsard, O., Gómez-Delgado, F., Moussa, R., Rapidel, B., Perez, A., Barquero, A., Rivera Wilson, C., Benegas, L., Kinoshita, R., Taugourdeau, S., Navarro, M.N.V., Jourdan, C., Le Maire, G., Harmand, J.- M., Bonnefond, J.M., Vaast, P., 2010. The CAFNET/Coffee-Flux project: evaluating water, sediment and carbon ecosystem services in an agroforestry coffee watershed (Costa Rica). 21st Century Watershed Technology: Improving Water Quality and Environment. American Society of Agronomical and Biological Engineers (ASABE), University La Earth Costa Rica, Poster presentation.
In contrast, with these previous works (Mesnage & Picot, 1995; Metzger et al. Accepted 2005), the most relevant fact in the present study, is the shape of nutrient porewater profiles measured in summer 2003. Indeed, these profiles have a very uncommun shape exhibiting a transient consequence of this shellfish impacted ecosystem. The concentration gradient is not limited to the 10 first cm below the water-sediment interface, instead, it extends above the sediment-water interface, at the base of the water column. This kind of profile (Figures 2a, 3a and 4a) is very close to the theorical one, described by Enell & Löfgren (1988), for shallow eutrophic lagoons exposed to high organic matter inputs (fish farming, phytoplankton or macro-algae sedimentation following the spring bloom). Thus, geochemical porewater results at C5, indicate a great seasonal variation evidenced by important increase of nutrients concentrations from Winter to Summer and provide a useful tool to evaluate the aquatic ecosytems trophic level, the difference between Summer and Winter nutrients concentrations being more pronounced in eutrophic ecosystems.
Photo 1: Arabica coffee agroforestry watershed in the Aquiares
farm (Costa Rica), below Erythrina poeppigiana shade tree
1. Aims of the CAFNET/Coffee-Flux Project
“Coffee-Flux” is a sub-project of CAFNET (EuropAid/121998/C/G): “Connecting, enhancing and sustaining environmental services and market values of coffee agroforestry in Central America, East Africa and India”. It was launched in December 2008 in Costa Rica by Cirad, CATIE, PCP and the Aquiares farm. The aim of Coffee-Flux is to assess the water, sediment and carbon E nvironmental S ervices ( ES ) at the scale of a coffee agroforestry coffee watershed. Experimentation, modelling and remote- sensing are combined. Coffee-Flux is a contributor to FLUXNET ( http://daac.ornl.gov/FLUXNET/ ). The platform is wide open to new projects, scientists and of course to students.
Coastal environments are subjected to anthropogenic threats, of which pollution by trace elements (TEs). They remain chemicals of concern because of their toxicity, their ability to be concentrated in biota and their persistence in sediment. Aware of these threats, monitoring agencies perform large environmental surveys. However, the databases generated often remain underexploited, even though they represent an important source of information for scientists. As a case study, we focused on the highly industrialized and developed coastal area of the Solent, south coast of the UK, which is also a European Marine site with protected habitats and species. To date, no scientific-based spatiotemporal trend has been published regarding its pollution in TEs. But mining of existing databases requested from the
CH 4 ) and the seasonal fluxes of iron and manganese
associated to the process of benthic microbial degra- dation of organic matter are quantified. The inorganic nutrients release at the sedimentwater interface, the role of sediment resuspension on this release and the impact of benthic remineralization in sustaining the water column primary production are investigated emphasizing the role of eutrophication on these last processes. Section 4 contains two papers on the sedi- ments geochemistry. One discusses the role of the salt- marshes vegetation in the sediment chemistry (in the Tagus estuary, Portugal) and, in particular, it inves- tigates the influence of the release of oxidants by the plant roots on the benthic remineralization process and on the immobilization of metals such as zinc and lead. The other paper analyses the composition of histor- ically deposits with the aim of reconstructing the paleoenvironmental events in the eastern Yellow Sea. The last section contains six papers on sea level rise, land reclamation and resource management from Cameroon, China and the Waden Sea. Time series data, satellite observations and a few modelling results are analyzed in view of assessing the impact of sea level rise and human activities (e.g. urbanization, industrial development, land reclamation) on the func- tioning of the aquatic ecosystem (e.g. biodiversity, sediment composition) and on the evolution and hydrography of river deltas, tidal flats and salt marshes as well as to compare this impact to this normally associated with natural geological processes.
Fig. 8. Conceptual scheme of exchange processes for dissolved and particulate matter during a tidal cycle in the tidal creeks. Letters A, B, C,
and D refer to high tide, ebb, low tide, and flood, respectively. Fluxes (E. Kristensen, unpublished) are presented in mmol m − 2 d − 1 , positive fluxes are towards the water column, negative fluxes indicate net uptake by sediments.
markers (e.g. Bouillon et al., 2004), yet such data only re- ferred to the upper layers of the sediments, where inputs of non-mangrove sources are likely to be most important (i.e. microphytobenthic production and deposition of sus- pended matter from the water column). Since mineraliza- tion in deeper sediment layers – where the organic matter is often to a larger extent mangrove-derived, e.g. Marchand et al. (2003) – can also reach high levels (Alongi et al., 2004), previous evidence from bacterial markers did not necessar- ily demonstrate the importance of allochtonous (i.e. non- mangrove) sources at the entire ecosystem level, whereas the approach used here does confirm that marine-derived organic matter contributes substantially to the integrated mineraliza- tion within the mangrove system boundaries.
convection (OOC) (Béthoux et al., 2002 ; Durrieu de Ma- dron et al., 2013) (Fig. 1).
DSWC shows a strong interannual variability and is an essential mechanism for sediment-transport and re- suspension on the shelf-slope. River inputs of particulate organic matter and metals, initially sequestered in shelf sediments, are eventually remobilized and exported to- ward the slope and the basin during these events (Durrieu de Madron et al., 2008 and references therein). While plumes of dense and turbid coastal water generally reach depths of a few hundred meters on the slope, occasional formation of very dense coastal water provokes the rapid propagation of the plumes down to the base of the slope and eventually into the basin (Durrieu de Madron et al., 2005, 2013 ; Canals et al., 2006 ; Palanques et al., 2012; Palanques & Puig, 2018). The open-slope south of Cap de Creus Canyon, which is the main export pathway for dense water formed on the shelf, thus appears as a region where recurrent deposition of exported matter could po- tentially occur. Occasional deep DSWC events, observed in the southwesternmost canyons of the GoL, displace erodible sediment from the upper- and mid-canyons to their lower reaches (Canals et al., 2006; Palanques et al.,
The Ras Dege mangrove forest showed characteristics of an ‘inverse estuary’, i.e. a tidal system without freshwater inputs where the salinity values are elevated at low tide
in the upper reaches of the creek. This is a regular feature in mangrove creeks, and is typically observed during prolonged dry periods with high evaporation rates (Wolanski, 1986; Kitheka, 1996). Salinity variations therefore present a mirror image of the water column height (Fig. 2), showing typical oceanic values at high tide (∼35), but increasing to nearly 38 at low tide. Porewater salinities at the forest floor (0–12 cm) measured
The application of geochemical fingerprinting techniques in the Fukushima region clearly indicated that Fluvisols are a dominant source of sediment. This application, owing to the recent age of soils and the dominance of volcanic activity, demonstrated a unique approach to geochemical fingerprinting focused on soil types rather than geology. There were two main challenges with the application of this technique. First, there may simply be an influence of geology or varying subtypes of soil classes that may impact the fingerprinting results. Second, it was difficult to find laboratories willing to analyze radiocesium contaminated-sediment with mass-spectrometry. The result of these challenges was a narrow suite of elements provided with INAA, leading to only three elements providing significant discrimination between these soil types.
the river network, it affects only a small fraction of the entire drainage basin area (basin area of dam 1 watershed: S 1 ⬍⬍⬍ S2 , S 3 , 䡠 䡠 䡠 ), i.e., it affects only a small fraction of sediment
load, with the assumption that sediment loads are proportional to water discharge. This is not taken into account in the ap- proximation of Vo¨ro¨smarty et al. : a high-storage capacity in the upper reaches may be applied to the sediment load of the entire watershed although it affects only a small part of the sediment load.
RESULTS : Impact of dams on water fluxes
As outlined above, the Sebou River system is heavily regulated, thereby significantly altering the flow regime. Haïda (2000) estimated the water discharges before and after the construction of the dams (Table 1). Between 1940 and 1972, the water discharge of the Sebou River and its tributaries was about 5.10 Mm 3 . The construction of the Idriss 1 er (1973), Allal El Fassi (1990) and Al