Dissolved phosphorus retention and release from a coastal plain in-stream wetland

Dissolved phosphorus (DP) can be released from wetlands as a result of flooding or shifts in water column concentrations. Our objectives were to determine the long-term (1460 d) DP retention and release characteristics of an in-stream wetland, and to evaluate how these characteristics respond to flooding, draining, and changes in DP concentrations. The studied in-stream wetland drains an agriculturally intensive subwatershed in the North Carolina Coastal Plain region. The wetland's DP retention and release characteristics were evaluated by measuring inflow and outflow DP concentrations, DP mass balance, and DP movement across the sediment-water column interface. Phosphorus sorption isotherms were measured to determine the sediment's equilibria P concentration (EPCo), and passive samplers were used to measure sediment pore water DP concentrations. Initially, the in-stream wetland was undersized (0.31 ha) and released 1.5 kg of DP. Increasing the in-stream wetland area to 0.67 ha by flooding resulted in more DP retention (28 kg) and low outflow DP concentrations. Draining the in-stream wetland from 0.67 to 0.33 ha caused the release of stored DP (12.1 kg). Shifts both in sediment pore water DP concentrations and sediment EPCo values corroborate the release of stored DP. Reflooding the wetland from 0.33 to 0.85 ha caused additional release of stored DP into the outflowing stream (10.9 kg). We conclude that for a time period, this in-stream wetland did provide DP retention. During other time periods, DP was released due to changes in wetland area, rainfall, and DP concentrations.     

Perspectives on the nature and definition of ecological regions

Among environmental managers, recognition of the importance of integrating management activities across agencies and programs that have different responsibilities for the same geographic areas has created an awareness of the need for a common hierarchical framework of ecological regions (ecoregions) to implement the strategy. Responding to this need in the United States, nine federal agencies have signed a memorandum of understanding on the subject of developing a common framework of ecoregions. However, considerable disagreement over how to define ecoregions and confusion over the strengths and limitations of existing frameworks stand in the way of achieving this goal. This paper presents some perspectives on the nature and definition of ecoregions related to this confusion and provides a brief overview of the weight of evidence approach to mapping ecoregions, using an example initiated by the US Environmental Protection Agency. To effectively implement ecosystem assessment, management, and research at local, regional, and national levels, research is needed to increase our understanding of ecoregions. We must find ways to illustrate the nature of ecoregion boundaries and the variability of characteristics within ecoregions as they relate to management issues. Research must also be conducted on comparing existing frameworks and developing indices of ecological integrity to effectively evaluate their usefulness.     

Air pollution and forest health: toward new monitoring concepts

It is estimated that 49% of forests (17 million km(2)) will be exposed to damaging concentrations of tropospheric O(3) by 2100. Global forest area at risk from S deposition may reach 5.9 million km(2) by 2050, despite SO(2) emission reductions of 48% in North America and 25% in Europe. Although SO(2) levels have decreased, emissions of NO(x) are little changed, or have increased slightly. In some regions, the molar SO(4)/NO(3) ratio in precipitation has switched from 2/1 to near 1/1 during the past two decades. Coincidentally, pattern shifts in precipitation and temperature are evident. A number of reports suggest that forests are being affected by air pollution. Yet, the extent to which such effects occur is uncertain, despite the efforts dedicated to monitoring forests. Routine monitoring programmes provide a huge amount of data. Yet in many cases, these data do not fit the conceptual and statistical requirements for detecting status and trends of forest health, nor for cause-effect research. There is a clear need for a re-thinking of monitoring strategies.     

Contrasting effects of manure and compost on soil pH, heavy metal availability and growth of Chenopodium album L. in a soil contaminated by pyritic mine waste

Chenopodium album L. was found to be one of the initial plant species colonising a heavy metal-contaminated site, polluted by pyritic (sulphide-rich) waste from the Aznalcóllar mine spill (South-western Spain). This indicates its importance in the re-vegetation of this soil. In a pot experiment, C. album was sown in soil collected from the contaminated site, either non-amended or amended with cow manure or compost produced from olive leaves and olive mill wastewater, in order to study the effect on heavy metal bioavailability and soil pH. In non-amended and compost-amended soils, soil acidification, probably resulting from oxidation and hydrolysis of sulphide, led to increases in the concentrations of soluble sulphate and plant-available Cu, Zn and Mn in the soil (extractable with 0.1 M CaCl(2)). Under these conditions, shoot growth of C. album was negligible and shoot concentrations of Zn (2,420-5,585 microg g(-1)) and Mn (5,513-8,994 microg g(-1)) were phytotoxic. Manure application greatly increased shoot growth and reduced the shoot concentrations of Cu, Zn, and Mn, and their plant-available concentrations in the soil. These effects appeared to be related to an increase of soil pH, due to an inhibition of sulphide oxidation/hydrolysis, relative to the non-amended soil. For metal sulphides-contaminated soil, liable to acidification, manure application appears to be able to enhance the initial stages of re-vegetation, by species such as C. album.     

Behavioural and physiological responses of the Norway lobster,<Emphasis Type="Italic"> Nephrops norvegicus</Emphasis> (Crustacea: Decapoda), to sulphide exposure

The Norway lobster, Nephrops norvegicus, is moderately tolerant of sulphide [the lethal time to 50% mortality (LT₅₀) was 22.5 h when exposed to 500 M sulphide] but, whenever possible, it attempts to avoid the presence of sulphide in its immediate vicinity. Any sulphide entering the animal is oxidized to thiosulphate, which accumulates in the haemolymph and in the tissues. During exposure to low concentrations of sulphide, the rate of oxygen consumption is maintained or even enhanced even though the lobsters become quiescent. The apparent increase in oxygen consumption is probably due to the oxidation of sulphide to thiosulphate. At higher concentrations, oxygen consumption decreases, perhaps because of the inhibitory effect of sulphide on electron transport, and N. norvegicus resorts to anaerobic metabolism as indicated by the accumulation of lactate in the haemolymph and in the tissues.Communicated by L. Hagerman, Helsingør     

Anatomical and experimental evidence for particulate feeding in<Emphasis Type="Italic"> Lucinoma aequizonata</Emphasis> and<Emphasis Type="Italic"> Parvilucina tenuisculpta</Emphasis> (Bivalvia: Lucinidae) from the Santa Barbara Basin

Previous nutritional models for adults of the lucinid bivalve Lucinoma aequizonata contend that symbiotic chemoautotrophic bacteria provide most of the organic carbon for the host. The existence of this symbiosis, coupled with the hosts distinctive anatomical features, shaped the impression that particulate feeding was not a significant part of L. aequizonata nutrition. Here, we use several techniques to show that particulate feeding is a consistent and important part of the L. aequizonata nutritional strategy. Histological and scanning electron microscopy observations reveal that the gills of L. aequizonata, like those of the lucinid Parvilucina tenuisculpta, have functional mucociliary epithelia, able to transport captured particles to the mouth. Observations of gut content and radiolabeled feeding experiments indicate that L. aequizonata does ingest and assimilate carbon from particulate organic matter. Furthermore, molecular identification of a broad spectrum of organisms in the guts of native adult specimens demonstrates that L. aequizonata is non-selective when ingesting organic material, and has a mixotrophic diet.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by P.W. Sammarco, Chauvin     

Juvenile–adult relationship in the gregarious ophiuroid<Emphasis Type="Italic"> Ophiothrix fragilis</Emphasis> (Echinodermata): a behavioral and morphological study

Ophiothrix fragilis forms dense beds in the North Sea–English Channel region, where juveniles are exclusively found on adults. The aim of this study was to see how the behavior and morphology of juveniles could help elucidate the close juvenile–adult relationship found in this species. Juveniles are found on the disk, arms and in the bursae of adult conspecifics, the ones on the disks being significantly larger. No clear advantage seems to be gained by the juveniles being in the bursae, and their presence there is most likely due to juvenile movement on adults and to and from adults. Hooked spines serve as anchory organs during the early life of the juvenile, but growth of the arms enhances its anchory capabilities and the hooked spines become secondary in that respect. They regress as ophiuroids become older, to the advantage of the other spines used in suspension feeding. Juveniles are attracted to conspecifics, and true gregarious behavior has been observed. The tip of each arm, the terminal tentacle, plays a major role in distance chemoattraction, with juveniles needing at least one intact terminal tentacle to be able to initiate a response. Electron microscope observations of the terminal tentacle permitted us to recognize two different potential receptor structures designated stäbchens. The first possesses one long projecting cilia and is mostly present around the base of the terminal tentacle, while the other has one to five short projecting cilia and is mostly found on the tip. No receptors are found on the shaft. Receptors are not associated with secretory structures. Juveniles and adults are closely associated with one another, and both the morphology and behavior of juveniles play an important role in that relationship.Communicated by O. Kinne, Oldendorf/Luhe     

Prediction of ambient PM10 and toxic metals using artificial neural networks

In this study, an artificial neural network is employed to predict the concentration of ambient respirable particulate matter (PM10) and toxic metals observed in the city of Jaipur, India. A feed-forward network with a back-propagation learning algorithm is used to train the neural network the behavior of the data patterns. The meteorological variables of wind speed, wind direction, relative humidity, temperature, and time are taken as input to the network. The results indicate that the network is able to predict concentrations of PM10 and toxic metals quite accurately.     

Use of 129I and 137Cs in soils for the estimation of 131I deposition in Belarus as a result of the Chernobyl accident

Using radioactivity measurements for 131I and 137Cs and nuclear activation analysis (NAA) or accelerator mass spectrometry (AMS) for 129I, ratios of 131I/137Cs and 129I/137Cs have been determined in soils from Belarus. We find that the pre-Chernobyl ratio of 129I/137Cs in Belarus is significantly larger than expected from nuclear weapons fallout. For the Chernobyl accident, our results support the hypothesis that there was relatively little fractionation of iodine and caesium during migration and deposition of the radioactive cloud. For sites having 137Cs > 300 Bq/kg, 129I can potentially give more reliable retroactive estimates of Chernobyl 131I deposition. However, our results suggest that 137Cs can also give reasonably good (+/-50%) estimates for 131I in Belarus.     

Radiocesium in North San Francisco Bay and Baja California coastal surface waters

Radiocesium, 137Cs, and rare earth elements (REEs) were determined in suspended material and dissolved fractions of waters across the salinity gradient in North San Francisco Bay (estuary). We describe the variation of this conservative isotope tracer with salinity and sediment load. REE data are used to differentiate marine and terrigenous source terrains for suspended material and dissolved fractions. We estimate that about 1-4 x 10(10) Bq of 137Cs migrates annually on suspended material through the North Bay. In addition, 137Cs concentrations were measured in surface waters off Baja California. Combined in situ water density (sigma(t)) and 137Cs data distinguish between California Current and Gulf of California water, and delineate areas of upwelling, where nutrient-rich, deep Pacific Intermediate water, with little or no 137Cs, is brought to the surface off promontories along Baja California.