Restoration of ailing wetlands

It is widely held that humankind's destructive tendencies when exploiting natural resources leads to irreparable harm to the environment. Yet, this thinking runs counter to evidence that many ecological systems damaged by severe natural environmental disturbances (e.g., hurricanes) can restore themselves via processes of natural recovery. The emerging field of restoration ecology is capitalizing on the natural restorative tendencies of ecological systems to build a science of repairing the harm inflicted by humans on natural environment. Evidence for this, for example, comes from a new meta-analysis of 124 studies that synthesizes recovery of impacted wetlands worldwide. While it may take up to two human generations to see full recovery, there is promise, given human will, to restore many damaged wetlands worldwide.     

Backfilling canals to restore wetlands: empirical results in coastal Louisiana

Wetland restoration is largely a developing science and engineering enterprise. Analyses of results are too few and constrained to observations over a few years. We report here on the effectiveness of one restoration technique used sparsely in coastal Louisiana for several decades. Canals have been dredged in coastal Louisiana wetlands since 1938 for oil and gas exploration and extraction. These canals are typically dredged to 2.5 m depth and are 20 to 40 m wide. Canal lengths vary from 100 m to several 1000s m in the case of outer continental shelf pipeline canals that cross the wetlands.Today, thousands of miles of canals crisscross these wetlands. Studies have linked dredged canals to a number of undesirable effects on the wetland environment including alterations in salinity, flooding and drainage patterns, direct loss of marsh by convention to open water, and increases in marsh erosion rates. These effects have led state and federal agencies charged with managing the wetland resource to look for methods of mitigating canal impacts. One possible method of managing spoil banks after the abandonment of a drilling site is to return spoil material from the spoil banks to the canal with the hope that marsh vegetation will be reestablished on the old spoil banks and in the canal. The movement of former spoil bank material back into the canal is referred to as backfilling.The purpose of this study was to (1) examine how backfilled canals changed over 10 years, (2) examine factors influencing success with multiple regression statistical models, and, (3) compare costs of backfilling with other Louisiana marsh restoartion projects. We examined the sites to document and interpret changes occurring since 1983/4 and to statistically model the combined data derived from these new and previous analyses. Specifically, we wanted to determine the recovery rates of vegetation, water depth, and soils in backfilled canals, restored spoil banks, and in nearby marshes, and to quantify the influence of plugging canals on these rates.The major factors determining backfilling restoration success are the depth of the canal, soil type, canal dimensions, locale, dredge operator skill, and permitting conditions. Plugging the canal has no apparent effect on water depth or vegetation cover, with the exception that submerged aquatic vegetation may be more frequently observed behind backfilled canals with plugs than in backfilled canals without plugs. Canal age, soil organic matter content, and whether restoration was done as mitigation on-site or off-site were the most important predictors of final canal depth. Canal length and percentage of spoil returned (+) had the greatest effect on the restoration of vegetation cover. Backfilled canals were shallower if they were older, in soils lower in organic matter, and backfilled off-site. Backfilling the canal restores wetlands at a cost of $1,200 to $3,400/ha, which compares very favorably with planned restoration projects in south Louisiana.Corresponding Editor: Anonumous     

Upscaling nitrogen removal processes in fluvial wetlands and irrigation canals in a patchy agricultural watershed

Wetlands Ecology and Management - The evaluation of nitrogen (N) removal in aquatic ecosystems within human exploited watersheds may allow the setting of upper limits of N use in agriculture....     

Restoration of floodplain wetlands: Opening polders along a coastal river in Mediterranean France, Vistre marshes

Restoration of wetlands has become an increasing field of application of ecological research due to mitigation regulations, changes in agricultural practices and an increasing consideration of the role of wetlands in the water cycle. In areas where the history of human use of natural areas is old and intense, restoration projects must not only consider ecological objectives but also social aspects. The Vistre project was developed to answer a social demand of restoring the flood storage function of a riverine wetland, formerly drained and polderized for agriculture. The river is located in the Petite Camargue, southern France, and flows into the sea a few km downstream of the study site. Openings in the dykes, calculated after a preliminary study, partly restored the connection between the polder and the river basin. A monitoring program of flora and fauna was launched to test the hypothesis that the change in hydrological functioning would be sufficient to obtain the desired vegetation and fauna. During the first years of the project, high rainfall and uncontrolled openings of sluices due to difficulties with the local users caused abnormally high water levels. The vegetation changed to hydrophyte-dominated communities and was controlled mainly by the fluctuations in water level. The habitat objective for fish-eating birds was met and a large tree-nesting heron colony established. Solving the social problem and maintenance of the sills should allow most objectives to be reached, although more slowly than expected.     

Organic matter accumulation in western boreal saline wetlands: A comparison of undisturbed and oil sands wetlands

Reconstructing landscapes after open pit mining of the Canadian oil sands presents enormous challenges. Freshwater peatlands dominate the pre-disturbance landscape; however, elevated salinity in the post-disturbance landscape will exclude the use of many freshwater vegetation species for reclamation. Successful reclamation will require plants to grow and accumulate peat despite elevated salinity. We evaluated the potential of salt-tolerant plants to accumulate peat by integrating plant production and decomposition rates in natural and oil sands wetlands across a salinity gradient. These wetlands were dominated by marsh-like vegetation with relatively rapid decomposition, especially of the belowground plant material. Aboveground production was high enough to compensate for rapid decomposition, resulting in mean annual organic matter accumulation of 307 g m^?2. Thus, both natural wetlands (which despite the elevated salinity had peat deposits >35 cm) and the oil sands wetlands accumulated organic matter during the study. There is potential for peat to accumulate in future oil sands wetlands, although long-term accumulation rates may be slower than in undisturbed freshwater fens and bogs. A reliable water supply and a host of other factors will be required for wetlands to accumulate organic matter, and eventually peat, in the post-mining landscape.     

Bioassessment of benthic macroinvertebrates in wetlands: a paired comparison of two standardized sampling protocols

Wetlands Ecology and Management - We compared a rapid bioassessment protocol (Traveling Sweep Approach [TSA]) with a more conventional time intensive protocol (Composite Transect Approach [CTA]) to...     

Gonorrhea modeling: a comparison of control methods

A population dynamics model for a heterogeneous population is used to compare the effectiveness of six prevention methods for gonorrhea involving population screening and contact tracing of selected groups. The population is subdivided according to sex, sexual activity, and symptomatic or asymptomatic infection. For this model contact tracing of certain groups is more effective than general population screening.     

Protein determination: a comparison of several methods

A comparison of four methods for the determination of total proteins is presented from the following points of view: - sensitivity; - specificity; - amount of work, chemicals, time and equipment needed for the performance of the determination. The following tests have been examined; Tombs' (absorbancy at 210 nm); Waddell's (difference in absorbancy between 215 and 225 nm); Warburg's (absorbancy at 280 nm); Lowry's (absorbancy at 500 nm after the reaction with phenol reagent). The authors recommend Tombs' method for its outstanding sensitivity, specificity and simplicity as the best of the four.     

Disrupting Escherichia coli: a comparison of methods

The often-encountered problem of disrupting bacteria for the purpose of extracting soluble protein has generated various methods. Many require specialized equipment. Very often, especially during preliminary studies, investigators need a simple, fast, and inexpensive method for cell disruption that preserves biological activity. This paper compares some simple and inexpensive methods for cell disruption, such as bead-vortexing, freezing-thawing, French pressing, and sonication. It also provides some tips to increase protein yield and preserve biological activity. If performed under optimal conditions, bead-vortexing gives protein yields that are comparable to French pressing and sonication. It also preserves the activities of labile enzymes and releases periplasmic enzymes. Vortexing with glass beads appears to be the simplest method for cell disruption.     

Virginity in haplodiploid populations: a comparison of estimation methods

1. The presence of ovipositing virgin females, who are able to produce only male offspring, may have several important consequences for the evolution of reproductive strategies.
2. The prevalence of virginity for five fig wasp species was estimated using three different methods: (1) the proportion of females developing in fruit that contained no conspecific males; (2) dissection of females caught on sticky traps; and (3) dissection of females that had emerged from their galled flowers into the fruit cavity.
3. The estimates obtained by method 1 (females developing in single sex broods) were lower than those obtained by the other methods.
4. Across species, the estimates obtained by method 1 (females developing in single sex broods) were significantly correlated with those obtained by method 2 (sticky trap caught females).
5. Mating with sperm-depleted males is unlikely to occur in these species.     

Prediction error estimation: a comparison of resampling methods

MOTIVATION: In genomic studies, thousands of features are collected on relatively few samples. One of the goals of these studies is to build classifiers to predict the outcome of future observations. There are three inherent steps to this process: feature selection, model selection and prediction assessment. With a focus on prediction assessment, we compare several methods for estimating the 'true' prediction error of a prediction model in the presence of feature selection. RESULTS: For small studies where features are selected from thousands of candidates, the resubstitution and simple split-sample estimates are seriously biased. In these small samples, leave-one-out cross-validation (LOOCV), 10-fold cross-validation (CV) and the .632+ bootstrap have the smallest bias for diagonal discriminant analysis, nearest neighbor and classification trees. LOOCV and 10-fold CV have the smallest bias for linear discriminant analysis. Additionally, LOOCV, 5- and 10-fold CV, and the .632+ bootstrap have the lowest mean square error. The .632+ bootstrap is quite biased in small sample sizes with strong signal-to-noise ratios. Differences in performance among resampling methods are reduced as the number of specimens available increase. SUPPLEMENTARY INFORMATION: A complete compilation of results and R code for simulations and analyses are available in Molinaro et al. (2005) (http://linus.nci.nih.gov/brb/TechReport.htm).     

Carbon-specific phytoplankton growth rates: a comparison of methods

Measurements of biomass and growth rate of two axenic algalcultures were carried out using three different methodologicalapproaches: the specific ¹⁴C-labelling of chlorophyll a, [³H]adenineincorporation into DNA and net organic carbon assimilation.Time-course experiments revealed that the specific activitiesof chlorophyll a were significantly higher than the specificactivity of total algal carbon in six of seven experiments.When the specific activity of chlorophyll a is used to calculatethe carbon biomass and growth rate, the carbon biomass of thealgae will thus be underestimated and the specific growth ratewill be too high. Determination of growth rates from incorporationof [³H]adenine gave lower values than those obtained from netorganic carbon assimilation and from ¹⁴C incorporation intochlorophyll a. Problems with adenine saturation are suggested.When [³H]adenine is used to measure growth rates in dense algalcultures, additions of >1 µM [³H]adenine are oftenrequired to maximally label the extracellular and intracellularadenine pools and hence DNA.     

Nutrient uptake in a stream affected by hydropower plants: comparison between stream channels and diversion canals

Small hydropower plants divert part of the water from wide and physically complex stream channels with active hyporheic areas to narrow and hydraulically simple concrete canals, and thus, might affect nutrient dynamics. We compared nutrient uptake in diversion canals and in stream channels in the Leitzaran Stream (Basque Country, northern Spain). We predicted that simple morphology in diversion canals will result in lower nutrient uptake in canals than in stream channels. Periphytic chlorophyll and biomass did not differ significantly between reach types. Water was significantly deeper and faster in canals than in stream channels, but the transient storage zone did not differ significantly between reach types. There were no significant differences between uptake length for neither phosphate nor ammonium between reach types. Uptake length in both stream channels and diversion canals decreased with discharge, in a pattern similar to that previously described for pristine rivers across the world. Uptake velocity and uptake rate for phosphate did not differ significantly between reach types, but in the case of ammonium both retention metrics were significantly larger in the diversion canals. Results suggest that although hydropower schemes have minor effects on nutrient retention, these depend on the proportion of flow diverted.     

Assessing the net effect of anthropogenic disturbance on aquatic communities in wetlands: community structure relative to distance from canals

Anthropogenic alterations of natural hydrology are common in wetlands and often increase water permanence, converting ephemeral habitats into permanent ones. Since aquatic organisms segregate strongly along hydroperiod gradients, added water permanence caused by canals can dramatically change the structure of aquatic communities. We examined the impact of canals on the abundance and structure of wetland communities in South Florida, USA. We sampled fishes and macroinvertebrates from marsh transects originating at canals in the central and southern Everglades. Density of all aquatic organisms sampled increased in the immediate proximity of canals, but was accompanied by few compositional changes based on analysis of relative abundance. Large fish ( >8 cm), small fish ( <8 cm) and macroinvertebrates ( >5 mm) increased in density within 5 m of canals. This pattern was most pronounced in the dry season, suggesting that canals may serve as dry-down refugia. Increases in aquatic animal density closely matched gradients of phosphorus enrichment that decreased with distance from canals. Thus, the most apparent impact of canals on adjacent marsh communities was as conduits for nutrients that stimulated local productivity; any impact of their role as sources of increased sources of predators was not apparent. The effect of predation close to canals was overcompensated by increased secondary productivity and/or immigration toward areas adjacent to canals in the dry season. Alternatively, the consumptive effect of predatory fishes using canals as dry-season refuges is very small or spread over the expanse of marshes with open access to canals. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Magnetic field exposure assessment: a comparison of various methods

The accurate and valid measurement of personal exposure to magnetic fields poses a major challenge for epidemiologic studies. When considering the various methods to assess exposure, it is unclear which measures are most relevant for studies of human disease, if any. Given these uncertainties, the Electromagnetic Fields and Breast Cancer on Long Island Study (EBCLIS) undertook a pilot study to develop the data collection protocol for a case-control study of breast cancer and magnetic fields. The pilot study used and compared various methods to assess residential exposures to magnetic fields, and related these measures to personal exposures. It included 31 women without breast cancer (mean age, 63+/-7 yr) who lived in their present homes for at least 15 yr. The pilot study consisted of an in-home interview, spot and 24-h magnetic field waveforms and broadband recordings, ground currents, wire coding, and personal 24-h broadband measurements. From the regression analyses, the model that best predicted personal magnetic field exposures included 24-h measurements in the bedroom and in the most lived-in room; as well as ground current test loads taken at the center of this most lived in room (r(2)=86%). The addition of other variables in this regression model yielded only small and nonsignificant increases in r(2). As a direct result of this pilot, EBCLIS will include ground current measurements in its protocol, which have not previously been collected as part of an epidemiologic study. Ground currents may be important because they may be richer in 180 Hz components than are the other currents in a power system. EBCLIS will have the opportunity to examine the ground-current hypothesis in the context of female breast cancer.     

The measurement of actin concentration in solution: a comparison of methods

Intrinsic optical density, Folin, and Biuret color development have been carefully studied as methods of determining actin concentration in solution. It appears that the Lowry (Folin) method is the most sensitive and reliable method as standardized by Kjeldahl analysis. Intrinsic optical density is also found to be a reliable method and the extinction coefficients of F and G actin at 280 and 290 nm are determined. The Biuret reaction is found to be the least reliable of the three methods for determining the concentration of actin in solution.     

Genetic evaluation with uncertain parentage: a comparison of methods

Summary The most common method for genetic evaluation when parents are unknown is best linear unbiased prediction with genetic groups (BLUP-G). With this method unknown parents are assumed to be unrelated to any other animals in the population. This assumption is unrealistic in most situations. If a finite number of potential parents can be identified and the probabilities of being the true parent can be assigned to these, genetic evaluation can be obtained given the uncertainty of parentage without introducing genetic groups into the model. The correct numerator relationship matrix with uncertain parentage () is derived. Rules are given to efficiently compute and ^-1. Computer simulation was used to compare BLUP-G with BLUP using . The simulated population consisted of ten sires and 200 dams per breeding season. The dams were always known; the sires were unknown for 10% or 30% of the males and 30% of the females. The number of potential sires was three (BLUP-₁ or ten (BLUP-₂), including the true sire in both cases. Equal probabilities were assigned to each potential sire. The increase in response with BLUP-₁ and BLUP-₂ relative to BLUP-G ranged from 4% to 8% in the fifth breeding season. Selection with BLUP-₁ or BLUP-₂ resulted in higher inbreeding, 17% and 12%, respectively, than with BLUP-G. Estimates of response to selection were unbiased with BLUP-₁ and BLUP-₂, but not unbiased with BLUP-G. Mean square error of estimated genetic means and mean prediction error variance were higher with BLUP-G than with blup-₁ or BLUP-₂.     

Methane flux in Peltandra virginica (Araceae) wetlands: comparison of field data with a mathematical model

We present a mathematical model of the diffusive flux of methane through Peltandra virginica. Data on the diurnal changes in both the petiolar [CH₄] gradient and the values of the radial bulk exchange coefficient, E_r, are entirely consistent with this model and the assertion that changes in stomatal conductance regulate the rate of methane efflux in P. virginica. The differences between the values of E_r calculated for daytime and nighttime conditions are -40% for the submerged condition and -54% for the emergent condition. The axial diffusivity of CH₄ through the petiole of P. virginica is estimated in vitro to be 0.771 cm² min^-1. Using our model, we estimate the equilibrium rate of methane efflux under daytime (97 ng CH₄ min ¹ petiole^-1) and nighttime (65 ng CH₄ min^-1 petiole^-1) emergent conditions. Numerical solutions of the model equations in the time domain offer a way of providing a dynamic model of the gas exchange responses of P. virginica to changing environmental conditions.