Diurnal photosynthetic performance of seaweeds measured under natural conditions

Statements comparing photosynthetic performance characteristics of species rely upon empirical data, usually light-saturation curves (photosynthesis, P, versus incidentlight flux-density, I _o, relationships) derived from instantaneous measurements. The specific comparative parameters are initial slope and maximum photosynthesis, P _max. For phytoplankton, diurnal variation in specific productivity at maximum incident light, I _max is typically asymmetrical, i.e., there is a morning maximum followed by an afternoon depression. Five seaweed species, numerical dominants from the Outer Banks of North Carolina, were examined for patterns of diurnal photosynthetic performance in sunlight of habitat equivalence. These were Codium decorticatum (Woodw.) Howe and Ulva curvata (Kütz.) De Toni in the Chlorophyceae, Dictyota dichotoma (Huds.) Lamour. and Petalonia fascia (O.F. Müll.) Küntze in the Phaeophyceae, and Gracilaria foliifera (Forssk.) Børg. in the Rhodophyceae. Diurnal patterns of oxygen exchange were varied, some symmetrical about the midday axis, others asymmetrical, and were specific for (1) species, (2) derived habitat, (3) thallus absorptance (1-I/I _o, where I is the transmitted light), (4) developmental stage, and (5) diurnal photosynthetically active radiation (PAR) history. All species show a depression in oxygen exchange rates at less than 0.1 I _max, and show varying degrees of recovery when I _o decreases from that value. Diurnal photosynthetic performance of some species at 0.03 I _o (total diurnal maximum) exceeds several times that at 0.70 I _o (total diurnal maximum), an observation not predicted by instantaneous measurements. Specific day-rate integrals of I _o vary, producing transient initial slope and P _max values. Thus, initial slope and P _max values derived from instantaneous measurements in the laboratory bear little relationship to actual diurnal production. At this time there appears to be no substitute for direct measurement of diurnal photosynthesis.     

Testosterone levels in midtrimester maternal and fetal plasma and amniotic fluid

Testosterone was measured in maternal plasma (58 samples), amniotic fluid (71 samples) and fetal plasma (55 samples) in 79 patients between 15 and 23 weeks' gestation. Maternal plasma testosterone levels were unrelated to fetal sex. Amniotic fluid testosterone was significantly higher in male than female fetuses but did not reliably predict fetal sex. A correct diagnosis of fetal sex was made by testosterone assay of pure fetal plasma in 39 out of 40 males and in 15 out of 15 females using 1.70 nmol/1 as the cut-off value. This investigation is not the method of choice for routine fetal sexing but may be of value in fetuses suspected of having certain endocrine disorders.     

DUI offenders' perceptions and misperceptions of basic alcohol information

This paper describes the perceptions and misperceptions of basic alcohol and DUI-related information held by two groups of subjects: first-time DUI offenders and multiple-DUI offenders. The results revealed that both samples of subjects were well informed regarding some basic information (e.g., tolerance, elimination of alcohol from the body by the liver, effect of several drinks on increased likelihood of accident) and that the multiple-DUI offenders appeared more knowledgeable on several items (e.g., penalty for refusing breath test, beverage equivalency). These results tend to discredit the knowledge-deficit model of DUI prevention/education/rehabilitation, and an alternative coping skills model is proposed.     

Vanishing seagrass (Zostera marina, L.) in Swedish coastal waters

Along the Swedish Skagerrak coast eelgrass (Zostera marina) is a dominant phanerogam on shallow soft bottoms. Eelgrass meadows are important biotopes for many crustacean and fish species being either migratory or stationary. During the 1980s, inventories of the shallow coastal areas with eelgrass have been carried out along the Swedish west coast as a basis for coastal zone management. In the present study we revisited 2000 ha of eelgrass meadows in 5 coastal regions along 200 km of the Skagerrak coast. The inventory was made with the same methods (aquascope) as during the 1980s, but increasing the mapping accuracy by using a Global Positioning System (GPS). The results from this study show that the areal extension of Zostera marina has decreased 58% in 10-15 years with great regional variations. The decline was mainly restricted to the shallow parts of the meadow. The causes and ecological consequences are discussed.     

Synergistic effects of cadmium and salinity combined with constant and cycling temperatures on the larval development of two estuarine crab species

The developmental stages from megalopa to third crab of the blue crab Callinectes sapidus Rathbun were tested in 12 combinations of cadmium (0, 50, and 150 ppb) and salinity (10, 20, 30, and 40) at 25°C. A reduction in survival and a significant delay in development from megalopa to third crab occurred within each salinity regime in 50 ppb compared with the control. Comparison of the delay in development within each salinity regime revealed that the sublethal effect of cadmium was most pronounced in the salinities normally preferred by C. sapidus. A similar comparison within each cadmium concentration, however, showed that the developmental time from megalopa to third crab was approximately the same irrespective of salinity. The developmental stages from hatch to first crab of the mud-crab Rhithropanopeus harrisii (Gould) were examined in 63 combinations of cadmium (0, 50, and 150 ppb), salinity (10, 20, and 30), constant temperature (20°, 25°, 30°, and 35°C) and cycling temperature (20° to 25°C, 25° to 30°C, and 30° to 35°C). The results indicated that cycling temperatures may have a stimulating effect on survival of the larvae compared to constant temperatures, both in the presence and in the absence of cadmium. Effects of cadmium and salinity and their interaction on the survival of the larvae from zoeae to megalopa were documented at most of the temperatures by analyses of variance. The zoeal larvae were more susceptible to cadmium than the megalopa. Effects of different combinations of cadmium and salinity on the duration of larval development were assessed by a t-test.     

Harmonized Nordic strategies for isocyanate monitoring in workroom atmospheres

The Nordic Network on Isocyanates (NORDNI) is financed by the Nordic Council of Ministers and is under the administration of Prof. Yngvar Thomassen and co-workers. National Institute of Occupational Health, Norway. The aim of NORDNI is to establish a broad network between the Nordic National Institutes of Occupational Health working within the field of isocyanate exposure and strategies for sampling and determination of isocyanates in workroom atmospheres. This viewpoint article summarizes the resolutions that were established at the 1st NORDNI consensus meeting arranged in Fr?ya, Norway, 31st August-2nd September, 2001. The consensus platform from the 1st NORDNI meeting was presented at the 4th International Symposium on Modern Principles of Air Monitoring, Lillehammer, Norway, 3-7 February, 2002.     

Prioritizing Stream Barrier Removal to Maximize Connected Aquatic Habitat and Minimize Water Scarcity

Instream barriers, such as dams, culverts, and diversions, alter hydrologic processes and aquatic habitat. Removing uneconomical and aging instream barriers is increasingly used for river restoration. Historically, selection of barrier removal projects used score‐and‐rank techniques, ignoring cumulative change and the spatial structure of stream networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. Here, a dual‐objective optimization model identifies barriers to remove that maximize connected aquatic habitat and minimize water scarcity. Aquatic habitat is measured using monthly average streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using economic penalty functions while a budget constraint specifies the money available to remove barriers. We demonstrate the approach using a case study in Utah's Weber Basin to prioritize removal of instream barriers for Bonneville cutthroat trout, while maintaining human water uses. Removing 54 instream barriers reconnects about 160 km of quality‐weighted habitat and costs approximately US$10 M. After this point, the cost‐effectiveness of removing barriers to connect river habitat decreases. The modeling approach expands barrier removal optimization methods by explicitly including both economic and environmental water uses.