Zooplankton biomass in the ice-covered Weddell Sea,Antarctica

Zooplankton was sampled by a Rectangular Midwater Trawl (RMT 1 + 8) in Weddell Sea surface waters (0 to 300 m) between 66 and 78°S during austral summer (February – March 1983). Sixty-nine taxa including different developmental stages were considered and divided into 16 size classes between <1 and >39.5 mm length. Biomass was determined by taxon and size class for three different meso- and macroplankton communities in the oceanic region, on the northeastern shelf and on the southern shelf of the Weddell Sea. The highest biomass of 11.2 mg DW m^–3 (3.4 g DW m^–2) was found in the northeastern shelf community (70 to 74°S), where juvenile and adultEuphausia crystallorophias accounted for 3.7 mg DW m^–3 (1.1 g DW m^–2). Although not quantitatively sampled, early copepodite stages (CI to CIII) ofCalanoides acutus andCalanus propinquus ranked second with 2.7 mg DW m^–3 (0.8 g DW m^–2). Biomass in the northeastern shelf community was concentrated in the size ranges 1 to 4 mm and 19.5 to 39.5 mm. The oceanic community of the central Weddell Sea was dominated by copepods smaller than 5 mm, which made up half of the total oceanic biomass. The tunicateSalpa thompsoni (7.0 to 8.5 mm) was the dominant single species with 1.6 mg DW m^–3 (0.5 g DW m^–2). Euphausiids, mainly juvenile and adult krillEuphausia superba, comprised 1.2 mg DW m^–3 (0.4 g DW m^–2). Total standing stock in the oceanic community was 9.4 mg DWm^–3 (2.8 g DW m^–2). Lowest biomass values were found in the southern shelf community (south of 75°S) with 4.0 mg DW m^–3 (1.2 g DW m^–2), concentrated in the 1 to 4 mm and 14.5 to 34.5 mm size classes. Abundant species were the pteropodLimacina helicina (1 to 2 mm; 0.7 mg DW m^–3; 0.2 g DW m^–2) andE. crystallorophias (24.5 to 39.5 mm; 0.9 mg DW m^–3; 0.3 g DW m^–2). The data reveal that it is essential to distinguish among subsystems in the Southern Ocean. This leads to a better understanding of the structure and function of those pelagic food webs which represent alternatives to the paradigmatic krill-centered system.     

INSTANTANEOUS PEAK FLOW ESTIMATION PROCEDURES FOR NEWFOUNDLAND STREAMS1

ABSTRACT: A procedure of estimating instantaneous flood flows for various return periods on the Island of Newfoundland is presented. The procedure is based on annual maximum instantaneous flows rather than annual maximum daily-mean flows, as the latter requires the conversion of estimated daily-mean flows into instantaneous flows. Regression equations were developed for each of three homogeneous regions for the desired return periods. The flood flow estimation capability of the presented procedure is demonstrated to be better than any other currently available procedure on the Island.     

Copper and zinc speciation in the solution of a soil-sludge mixture

Only a small fraction of the transition metals content in sludge-amended soils is soluble, and yet this fraction is a major contributor to the mobility and bioavailability of the metals. The chemical species of zinc (Zn) and copper (Cu) in the soluble fractions of soil-sludge mixtures were characterized with respect to their charge, molecular weight, and stoichiometry using ion exchange resin and gel chromatography procedures. The change in the metals' species with time after sludge application was followed for 100 d. Copper in the water extracts of the sludge-sand mixtures was found almost exclusively in low molecular weight (below 1000 Da) complexes. Higher molecular weight (around 2500 Da) dissolved organic carbon (DOC) was present in the extracts as well, but this DOC fraction exhibited little complexation. Copper was present in the extracts mainly as negatively charged species throughout the incubation period, and zinc tended to form zwitter ions. As incubation progressed, the relative content of positively charged Zn in solution increased. Complexation capacity of DOC in sludge water extract, extrapolated to infinite dilution, was 8.75 mM Ca g(-1) DOC. When the complexation capacity of the extract is near saturation, a mean Cu-DOC complex can be defined. It consists of 1.9 Cu atoms attached to DOC species containing 5.6 C atoms. Thus, the organic Cu complexes consist primarily of about two Cu ions attached to DOC species containing only five or six C atoms. Amino acids and small peptides or polycarboxylic acids, such as citric acid, thus may be important complexing agents of the metal.     

Canada shows the way

Editorial

Canada shows the way     

EFFECTS OF SLUDGE AND CHEMICAL FERTILIZER APPLICATION ON RUNOFF WATER QUALITY1

ABSTRACT: Simulated rainfall was used on experimental field plots to compare the effect of chemical fertilizer and sludge application on sediment, nitrogen, and phosphorus in runoff from no-till and conventional tillage systems. Chemical fertilizer application under the no-till system resulted in the least amount of total N and P in surface runoff. However, sludge application under the no-till system resulted in the least amount of NO₃-N and sediment in surface runoff. The worst water quality scenarios were observed when either sludge or chemical fertilizer were surface-applied under a conventional tillage system. Nitrogen losses from the conventional tillage system were minimized when sludge was incorporated into the soil. However, phosphorus and sediment yield from such a system were significantly higher when compared to phosphorus and sediment yield from the no-till system. The results from this study indicate that the use of sludge on agricultural land under a no-till system can be a viable alternative to chemical fertilizer for nitrogen and phosphorus control in runoff. A more cautious approach is recommended when the sludge is incorporated into the soil in a conventional tillage system because of potential for high sediment and phosphorus yield in surface runoff.     

Eusociality has evolved independently in two genera of bathyergid mole-rats — but occurs in no other subterranean mammal

Summary Extensive field and laboratory studies show that Damaraland mole-rats, like naked mole-rats, have an extreme form of vertebrate sociality. Colonies usually contain 2 reproductives and up to 39 non-breeding siblings, 90% of whom live a socially-induced lifetime of sterility; they remain in the natal colony, forage for food, defend the colony and care for successive litters. Although there is heightened dispersal following good rainfall, the majority of adult non-reproductives remain in their natal colony and failure to disperse is not directly attributable to habitat saturation or unfavourable soil conditions. A major dispersal event follows the death of a reproductive. Differences in colony cohesion, ethology and the hormonal profiles of non-reproductive animals suggests that eusociality evolved along different pathways in these two phylogenetically divergent genera of the Bathyergidae.     

Vertical migration ofGonyaulax catenata andMesodinium rubrum

Diel migration patterns ofGonyaulax catenata andMesodinium rubrum in the central Baltic during spring 1986 are presented. The depth at which maximum cell concentration of these species occurred was dependent during daytime to a great degree on light intensity; it is hypothesized that the organisms migrated upwards toward higher light intensities until a certain threshold irradiance was reached, after which migration was directed downwards to avoid light intensities higher than the threshold. This threshold level probably depended on nutrient conditions and on the daily average of total irradiance of the foregoing days (light history). Furthermore, it is hypothesized that migration is an important mechanism for adapting to daily irradiance fluctuations. The dependence of migration on irradiance was more obvious forG. catenata than forM. rubrum.     

Process design for the environment: A multi-objective framework under uncertainty

Designing chemical processes for the environment requires consideration of several indexes of environmental impact including ozone depletion, global warming potentials, human and aquatic toxicity, photochemical oxidation, and acid rain potentials. Current methodologies, such as the generalized waste reduction algorithm (WAR), provide a first step towards evaluating these impacts. However, to address the issues of accuracy and the relative weights of these impact indexes, one must consider the problem of uncertainties. Environmental impacts must also be weighted and balanced against other concerns, such as their cost and long-term sustainability. These multiple, often conflicting, goals pose a challenging and complex optimization problem, requiring multi-objective optimization under uncertainty. This paper will address the problem of quantifying and analyzing the various objectives involved in process design for the environment. Towards this goal, we proposed a novel multi-objective optimization framework under uncertainty. This framework is based on new and efficient algorithms for multi-objective optimization and for uncertainty analysis. This approach finds a set of potentially optimal designs where trade-offs can be explicitly identified, unlike cost-benefit analysis, which deals with multiple objectives by identifying a single fundamental objective and then converting all the other objectives into this single currency. A benchmark process for hydrodealkylation (HDA) of toluene to produce benzene modeled in the ASPEN simulator is used to illustrate the usefulness of the approach in finding environmentally friendly and cost-effective designs under uncertainty.     

Distribution and levels of eight toxaphene congeners in different tissues of marine mammals, birds and cod livers

Levels and distribution of eight compounds of technical toxaphene (CTTs) were determined in different marine species (seals, cetaceans, birds, and fish). The eight CTTs included six commercially available and two chlorobornanes prepared in our lab. These congeners were present in all investigated samples. In agreement with earlier studies, the octachlorobornane B8-1413 (P-26) and the nonachlorobornane B9-1679 (P-50) were the most abundant congeners in most of the samples. In seal blubber, B8-1413 (P-26) and B9-1679 (P-50) contributed with up to approximately 80% (Weddell seal) to the sum of the eight CTTs. In seals from the northern hemisphere the nonachlorobornane was more abundant while in those from the southern hemisphere (Antarctic and Namibia), the octachlorobornane B8-1413 (P-26) usually appeared at higher concentrations. Depending on the species the contribution of the other congeners varied significantly. B9-1025 (P-62) ranged from 2-20%, B8-1412 was found at 4-25% with highest contribution in birds, and B8-2229 (P-44) was found at 5-15%. The remaining three congeners B7-1453, B8-1414 (P-40), and B8-1945 (P-41) were lower abundant except B8-1414 (P-40) which was found at high contribution in liver and kidney of birds. The sum of the eight CTTs ranged from 4 microg/kg to 1.4 mg/kg, depending on the species and region. In most of the seal blubber samples, PCBs and DDT were more abundant (factor 2-20) but Antarctic Weddell seals showed higher CTT levels than PCBs and DDT.