Springer Science and Business Media LLC

This study presents the tidal exchange of ammonium, nitrite + nitrate, phosphate and silicate between two salt marshes and adjacent estuarine waters. Marsh nutrient fluxes were evaluated for Pointe-au-Père and Pointe-aux-Épinettes salt marshes, both located along the south shore of the lower St. Lawrence Estuary in Rimouski area (QC, Canada). Using nutrients field data, high precision bathymetric records and a hydrodynamic numerical model (MIKE21-NHD) forced with predicted tides, nutrients fluxes were estimated through salt marsh outlet cross-sections at four different periods of the year 2004 (March, May, July and November). Calculated marsh nutrient fluxes are discussed in relation with stream inputs, biotic and abiotic marsh processes and the incidence of sea ice cover. In both marshes, the results show the occurrence of year-round and seaward NH4 + fluxes and landward NO2 − + NO3 − fluxes (ranging from 9.06 to 30.48 mg N day−1 m−2 and from −32.07 to −9.59 mg N day−1 m−2, respectively) as well as variable PO4 3− and Si(OH)4 fluxes (ranging from −3.73 to 6.34 mg P day−1 m−2 and from −29.19 to 21.91 mg Si day−1 m−2, respectively). These results suggest that NO2 − + NO3 − input to marshes can be a significant source of NH4 + through dissimilatory nitrate reduction to ammonium (DNRA). This NH4 +, accumulating in marsh sediment rather than being removed through coupled nitrification–denitrification or biological assimilation, is exported toward estuarine waters. From average P and Si tidal fluxes analysis, both salt marshes act as a sink during high productivity period (May and July) and as a source, supplying estuarine water during low productivity period (November and March).

Reed stands in Germany and Europe were investigatedwith respect to their genetic diversity by means ofRandom Amplified Polymorphic DNA (RAPD) via thePolymerase Chain Reaction (PCR-fingerprinting).Different types of clonal distribution could bedistinguished: monoclonal reed stands and polyclonalreed stands, and among the latter, stands with low orhigh numbers of different clones as well as standswith mosaic-like coexisting or intermingling clones.Furthermore, clonal distribution and the expansion ofdifferent clones was observed within a newlydeveloping reed population. The findings appear tosupport a model of colonization postulating thatpopulations initiated by seeds are initiallygenetically diverse, but over time become dominated byone or a few clones adapted to the prevailing siteconditions. Thus, low genetic diversity seems to bethe result of a natural selection process. Clonaldiversity within a reed population and the type ofclonal distribution are discussed with regard to theirimportance for the reed stand's ability to adapt tochanging site conditions and eventually for itssurvival or die-back.

Most mangrove swamp/salt flat systems have tidal currents that are ebb dominated, however, some systems show only slight ebb dominance despite having a very large swamp volume relative to the creek volume. Cocoa Ck in northern Australia is such a system. Results are presented from a simple analytical model for flow in Cocoa creek together with detailed water level observations in the swamps. It was found that the primary factor reducing the ebb dominance of this system was the very low slope of the swamp surface. During rising tides, water floods as sheet flow; however, on ebb tides, the surface water slope in the swamp becomes greater than the swamp surface slope, with the result that areas of swamp closest to the main feeder creek (Cocoa Ck) dry before areas furthest from the creek. Thus, about an hour after ebb tide commences, there is a large quantity of water perched on the salt flats/mangroves, tens of centimetres higher than the water in the creek. This water cannot leave the swamp via sheet flow, but must leave through a very small and shallow creek which is also highly constricted by vegetation. This effectively increases the friction on ebb tides and results in a delay in water leaving the swamps and salt flats, reducing any tendency towards ebb dominance.

The Mira estuary is a narrow entrenched pristine estuary of the Ria type, about 30 km long. It comprises an area of 285 ha of salt marsh, of which250 ha have been proposed for reclamation for aquaculture. Dredging, village and recreation development menace the yet undisturbed estuarine ecosystem. To assess the biological importance of this wetland, a multidisciplinary study was conducted in apart of the salt marsh, considered as being representative of the whole area. Halophytic vegetation covering 75% of the total salt marsh site is dominated by Spartina maritima (28% of total vegetation area). Total primary production attains63,766 kg/yr (dw). A net export of 1541 kg/yr of COM to the relatively oligotrophic adjacent waters was also found. Insects and birds are described for the first time in the saltmarsh. Macrobenthic communities are dominated by Hediste diversicolor, Nepthys caeca and Scrobicularia plana. The fiddler crabUca tangeri attains here its north distribution limit. The mud flats and creeks associated with the salt marsh act as a nursery for 40.8% of the fish species present. The food web is dominated by detritivorous species like the grey mullets. The results obtained in this study support the need for an effective conservation of this area.

The frequency of fires in the Okavango Delta seasonal floodplains peaked at an intermediate frequency of flooding. Floodplains are commonly burnt every 3–5 years. This study showed fundamental changes in ecosystem properties due to burning. A burnt seasonal floodplain in the aquatic phase had oxygen levels well above saturation, 100–200%, while the levels in the un-burnt control site were below saturation and, at night, could decline to 10–40% saturation. The total phosphorous and total nitrogen concentrations were similar on both floodplains but considerably enriched relative to inflowing water, due to nutrient release from the flooded soil-sediment and animal droppings. Zooplankton biomass was very high in both systems although the abundance of fish fry was ten times higher on the un-burnt floodplain. In a low flood year the un-burnt floodplain water had high nutrient levels, primary production, methane emission, and subsequent uptake of methane in biota, as well as a high zooplankton biomass. The very high flood the following year showed the opposite with much lower production at all levels owing primarily to greater dilution of nutrients. The abundance of fish, however, was much higher during the high flood year. Macrophytes and litter provide direct shelter for fish fry but also promote low oxygen levels when decaying. Large flooded areas result in high fish production by removing obstacles related to congestion. This interplay between hydroperiod and fire may be crucial for the maintenance of high biological productivity both in the aquatic and terrestrial phases in a very nutrient poor wetland landscape. Understanding these interactions is crucial for optimal management.

This study examined changes in pH and extractable nutrients in soilsfollowing wetland creation. Sample plots were established in two areas: (1) an old-field with parts that were flooded during wetland creation, and (2) a native wetland in a floodplain of the Ohio River called Green Bottom Swamp. Soils were sampled before inundation and eight months afterwards. Compared to old-field soils in the pre-inundation period, swamp soils exhibited: (1) higher acidity, (2) lower NO3 and higher NH4 concentrations, (3) higher extractable P, Fe, and Mn, and (4) lower Ca, Mg, and Zn concentrations. Eight months after inundation, the old-field soil redox decreased from +210 mV in the old field −290 mV, and extractable NO3 and Ca decreased and extractable NH4 and Fe increased, but pH and extractable P, Mn, Mg, and Zn changed either slightly or not at all. These results suggest that eight months is an insufficient period of time for a complete change. Other results suggest that the response of nitrogen during the wetland creation processes may be extremely rapid.

Wetland habitat in the subalpine Rocky Mountains is an area of high biodiversity and includes many species of willow. These willow-dominated communities are often used for both summer and winter recreation. The maintenance of winter recreation trails has the potential to disturb wetland vegetation and compromise the long-term persistence of the wetland. In Breckenridge, Colorado, willow plants are clipped in October to a uniform height to prevent stems from protruding through the snow onto the ski trails, and large grooming tractors compact the snow on the trails. Our objective was to investigate the impact of winter recreation trail maintenance on growth and reproductive output of Salix planifolia (common names: planeleaf or diamondleaf willow) and to determine impacts on community diversity in a willow-dominated wetland system. Catkin production, plant height, and branch elongation were evaluated in meter-squared quadrats within paired belt transects both inside and outside a ski trail during the growing seasons of 2008 and 2009. In addition, percent cover of total vegetation was estimated for each species to calculate species richness and diversity. We found that maintenance of winter trails reduced catkin production and limited willow growth. Additionally, winter trail maintenance may have promoted the introduction of invasive species within the willow community. The activities associated with winter trail maintenance could interfere with the long-term persistence of the willow community adjacent to ski trails and should be considered when planning new trails in or along a wetland ecosystem.