Meiofauna on the seagrass Thalassia testudinum: population characteristics of harpacticoid copepods and associations with algal epiphytes

The composition and abundance of bladedwelling meiofauna was determined over a 15 mo period (1983–1984) from a Thalassia testudinum Banks ex König meadow near Egmont Key, Florida, USA. Harpacticoid copepods, copepod nauplii, and nematodes were the most abundant meiofaunal taxa on T. testudinum blades. Temporal patterns in species composition and population life-history stages were determined for harpacticoid copepods, the numerically predominant taxon. Sixteen species or species complexes of harpacticoid copepods were identified. Harpacticus sp., the most abundant harpacticoid, comprised 47.8% of the total copepods collected, and was present throughout the study. Copepodites dominated the population structures of the blade-dwelling harpacticoid species on most collection dates. Ovigerous females and/or copepodites were always present, indicating continuous reproductive activity. Results suggest that epiphytic algae influence meiofaunal abundance on seagrass blades, as densities of most meiofaunal taxa at Egmont Key were positively associated with percent cover of epiphytic algae throughout the study. The majority of significant correlations between meiofaunal density and cover of epiphytic algae involved filamentous algae, although encrusting algae dominated the epiphytic community. It appears that resources provided by epiphytic algae to seagrass meiofauna (additional food, habitat, and/or shelter from predation) may be associated with algal morphology.     

Mechanisms of copper tolerance in the marine fouling alga Ectocarpus siliculosus — Evidence for an exclusion mechanism

Copper-tolerant strains of the marine fouling alga Ectocarpus siliculosus (Dillw) Lyngb. have been recorded. The mechanisms of tolerance which may operate in a copper-tolerant strain were investigated by comparing the growth characteristics, copper content and extracellular organic production of tolerant and non-tolerant strains. Growth was measured by a wet-weight method. The copper content of dryashed cells was measured spectrophotometrically using tetraethylthiuram disulphide. The extracellular material is ultra-violet absorbing, and the production was measured by recording absorption at 265 nm. Evidence suggests that an exclusion mechanism is operating in the tolerant strain under investigation. The extracellular material, the cell wall or an associated organism make little or no contribution no this exclusion. Membrane and intracellular changes are believed to account for the tolerance in this strain of E. siliculosus.     

The impact of maternal serum alpha fetoprotein screening on open neural tube defect births in North-East Scotland

Over the three years period 1980–1982, 18 256 pregnancies in the Grampian Region of N-E Scotland including the islands of Orkney and Shetland were screened for raised levels of maternal serum alpha fetoprotein (MSAFP) in the second trimester. Thirty six cases of fetal open neural tube defect in singletons were detected (18 anencephaly and 18 spina bifida). Four additional cases of open spina bifida were associated with normal MSAFP levels although two of these were detected by amniotic fluid AFP measurement when amniocentesis was carried out because of previous NTD history. A further three cases of open spina bifida and two of anencephaly occurred in unscreened pregnancies. The MSAFP screening programme alone was thus instrumental in reducing the birth incidence of open neural tube defects by 36 out of 45 cases (80 per cent) in singletons.     

REGIONAL ASSESSMENT OF NLEAP NO3-N LEACHING INDICES1

ABSTRACT: Nonpoint source ground water contamination by nitrate nitrogen (NO₃-N) leached from agricultural lands can be substantial and increase health risks to humans and animals. Accurate and rapid methods are needed to identify and map localities that have a high potential for contamination of shallow aquifers with NO₃-N leached from agriculture. Evaluation of Nitrate Leaching and Economic Analysis Package (NLEAP) indices and input variables across an irrigated agricultural area on an alluvial aquifer in Colorado indicated that all leaching indices tested were more strongly correlated with aquifer NO₃-N concentration than with aquifer N mass. Of the indices and variables tested, the NO₃-N Leached (NL) index was the NLEAP index most strongly associated with groundwater NO₃-N concentration (r² values from 0.37 to 0.39). NO₃-N concentration of the leachate was less well correlated with ground water NO₃-N concentration (r² values from 0.21 to 0.22). Stepwise regression analysis indicated that, although inorganic and organic/inorganic fertilizer scenarios had similar r² values, the Feedlot Indicator (proximity) variable was significant over and above the NO₃-N Leached index for the inorganic scenario. The analysis also showed that combination of either Movement Risk Index (MIRI) or NO₃-N concentration of the leachate with the NO₃-N Leached index leads to an improved regression, which provides insight into area-wide associations between agricultural activities and ground water NO₃-N concentration.     

epa’s research program for controlling residential wood combustion emissions

A recently completed study has shown that emissions of participate, carbon monoxide, and organics (including polycyclic organic matter) are relatively high from residential woodburning stoves and fireplaces when compared to emissions from residential gas- and oil-fired furnaces. Since these emissions include a number of potentially hazardous compounds; the trend toward greater residential wood usage can have a negative impact on local ambient air quality. EPA is currently studying ways to operate existing stoves and design new stoves to minimize air pollutant emissions.     

Mercury balance in amalgamation in artisanal and small-scale gold mining: identifying strategies for reducing environmental pollution in Portovelo-Zaruma,Ecuador

The gold ore mined by artisanal and small-scale miners in Portovelo-Zaruma, Ecuador, is processed in custom mills. Miners can choose between Chilean-mill processing centers, where the ore is ground, concentrated and amalgamated, or “Chancha” Centers, where the whole ore is amalgamated. By weighing mercury before and after all unit operations involved in the amalgamation process, it was possible to determine mercury losses. Analyses in eight centers indicated that 51–59% of mercury introduced into the amalgamation process is recovered when miners squeeze the excess mercury. Around 29% of total mercury is lost when miners burn amalgam and gold is melted, and 15% is lost with the tailings. When only gravity concentrates are amalgamated, 1.4% of mercury entering the process is lost with tailings, whereas 29.5% is lost when the whole ore is amalgamated. Approximately 1.5 tonnes/annum of mercury is released in Portovelo-Zaruma, from which 70% is evaporated and 30% is released with tailings. Mercury-contaminated tailings are leached with cyanide in agitated tanks. A large majority of the processing centers dispose the final tailings with mercury and cyanide into the Calera River and Amarillo River. Mercury dissolved with cyanide likely becomes more bioavailable than metallic mercury. A campaign for reducing mercury emissions must focus on the use of individual retorts – mercury pollution control devices – and the elimination of whole ore amalgamation.     

Site Access and Sample Frame Issues for R-EMAP Central Valley, California, Stream Assessment

The Central Valley of California contains critical habitat for many aquatic and terrestrial biological resources. The purpose of this R-EMAP project was to assess the effects from a highly modified agriculturally dominated landuse area on the aquatic resources of the lower portion of the Central Valley watersheds. The study area is 24,346 mi2 and comprises the Sacramento Valley and San Joaquin Valley watersheds to the 1,000 ft. elevation contour. Populations of interest are man-made conveyances and wadeable natural streams. There are 40,756 miles of streams and constructed conveyances within the Central Valley as designated by RF3 database. Sample sites were selected to represent 14,399 miles of streams and sloughs, and 16,697 miles of constructed conveyances.     

Using Multiple Chemical Criteria for Critical Loads of Acidity in Maritime Regions

Critical loads have become a well-establishedpart of the work programme of the UnitedNations Economic Commission for Europe (UNECE) Conventionon Long-Range Transboundary Air Pollution (CLRTAP). Thelinking of ecosystem response to deposition level is thecentral principal of the critical loads approach. Foreach ecosystem, a biological indicator is chosen, asuitable chemical criterion selected and a criticalchemical limit assigned. The Bc:Al ratio is the mostwidely used chemical criterion for setting criticalloads. However, critical loads based on this criterionare very sensitive to marine deposition. In regions whichreceive high depositions of marine-derived base cations,such as the Republic of Ireland (ROI) and the UnitedKingdom (UK), critical loads based on the Bc:Al criterionwill inevitably be high. Therefore, it is proposed thatcritical loads are estimated using multiple chemicalcriteria with appropriate critical limits to protect thechosen biological indicators. The range of publishedchemical criteria have been applied to the ROI and theUK. The chemical criterion corresponding to the mostsensitive critical load have been mapped and thecontribution of each to the final maps investigated. Thesimulations indicate that the most sensitive criteria forsetting critical loads are based on specifying critical Hor Al concentrations. However, the choice of critical limits andmodel parameters will ultimately effect the criticalloads. Therefore, it is important that appropriate criticallimits are chosen to protect the biological indicator andreceptor ecosystem from long-term damage.     

The Role of Mineral Weathering Rate Determinations in Generating Uncertainties in the Calculation of Critical Loads of Acidity and their Exceedance

Current legislation within Europe aimed at limitingecosystem damage resulting from inputs of atmosphericpollution is based on the critical load concept. Mineralweathering rates are central to the calculation ofcritical loads (acceptable levels) of acid deposition.The authors have undertaken a number of studies whichillustrate the complications and limitations inherent inpredicting mineral weathering rates and the implicationswhich these have for critical loads calculations andmapping. Calculated weathering rates and critical loadsfor two acid-sensitive parent materials (greywackes andgranites) are presented and are used to illustrate theimpact that uncertainty can have on critical loadexceedances. The results have obvious implications forportraying the uncertainties of critical loads to policy makers.