Chemically mediated interactions between the red algaPlocamium hamatum (Rhodophyta) and the octocoralSinularia cruciata (Alcyonacea)

Interactions between the red algaPlocamium hamatum J. Agardh (Rhodophyta) and other benthic organisms including the alcyonacean soft coralSinularia cruciata (Tixier-Durivault) were investigated on an inshore fringing reef environment in whichP. hamatum was the dominant large fleshy alga. Field observations of sessile reef organisms including octocorals and sponges living in close proximity toP. hamatum revealed that varying degrees of tissue necrosis were suffered by the invertebrates when in physical contact with the alga. In order to establish whether the chemical constituents of the alga, especially chloromertensene, played a role in this necrosis, manipulative field experiments were carried out in the Pelorus Channel, Palm Island group (18°34S; 146°29E), North Queensland, Australia, in November and December 1988. The first experiment involved the relocation of healthy plants and soft corals into contact and non-contact situations on a mesh grid. In all cases of contact betweenP. hamatum andS. cruciata, the soft coral suffered tissue necrosis (n=6,p=0.0022). The second experiment had the same design, but involved the use of artificial plants both uncoated and coated with natural levels of chloromertensene, in contact withS. cruciata. In all cases of contact with coated treatments, necrosis was observed inS. cruciata (n=4,p=0.025). In cases where uncoated artificial fronds were placed in contact with soft corals,S. cruciata showed minor abrasion effects, but no appreciable necrosis. Coated treatments were not fouled by epiphytes during the experiment and were not consumed by predators. Uncoated treatments were rapidly reduced in size by predation and any remaining material was biofouled. These experiments thus demonstrated that the deleterious effects observed in soft corals in the field were caused by contact with the algaP. hamatum, that these effects were indeed chemically mediated by chloromertensene, and that physical contact without chemical intervention caused no such deleterious effects. This is the first experimental evidence which conclusively demonstrates allelopathy between an alga and other marine organisms and identifies the compound responsible for the observed allelopathic effects.     

Temperature and metabolic rate in sedentary fish from the Antarctic,North Sea and Indo-West Pacific Ocean

Resting metabolic rate was measured in demersal stages of the teleostNotothenia neglecta Nybelin from the South Orkney Islands, Antarctica, from 1985 to 1987. The relationship between and body mass (Mb) conformed to the general relationship , wherea is a proportionality constant andb is the scaling exponent. (mg O₂ h^–1) was found to scale toMb ^{(0.82±0.011)} in the summer (November to April, 1.6 to 1 850 g,n=56) and toMb ^{(0.76±0.013)} in the winter (May to October, 0.9 to 1 850 g,n=57) (values ofb are means ± SD). Although the scaling exponents were significantly different (P<0.01), was similar in the juvenile stages of summer- and winter-caught fish matched for body mass. The effects of activity on oxygen consumption was studied using a Brett respirometer. Adult stages had a factorial aerobic scope for activity of 5.7, which is similar to that reported for demersal fish from temperate latitudes. The effects of temperature on resting metabolism was investigated in fish with similar sedentary lifestyles from the North Sea (Agonus cataphractus andMyoxocephalus scorpius) and the Indo-West Pacific (Paracirrhites forsteri, P. arcatus, Neocirrhites armatus andExallias brevis). Extrapolated values of for the tropical species approached zero at 5 to 10°C. For a standard 50 g fish, for the tropical species at 25°C was in the range 3.4 to 4.4 mg O₂ h^–1, compared with 1.3 mg O₂ h^–1 forNotothenia neglecta at its acclimation temperature. Thus, the maximum metabolic rate of sedentary tropical species at 24°C is likely to be 2 to 4 times higher than inN. neglecta at 0°C. This suggests that the energy available for sustained activity is significantly lower in cold- than in warm-water fish.     

Temperature acclimation of respiration and photosynthesis in the brown algaLaminaria saccharina

Sporophytes of the brown algaLaminaria saccharina (L.) Lamour grown at 15°C contained significantly more chlorophylla (chla) than did similar plants grown at 5°C. The increase in chla in 15°C plants was due to increased numbers of photosystem II reaction centes, and possibly to increased photosynthetic unit size, compared with 5°C plants. These changes were associated with increased values (photosynthetic efficiencies) in 15°C-grownL. saccharina relative to 5°C-grown plants. The changes in together with reduced respiration rates allowed 15°C-grownL. saccharina to achieve net photosynthesis and light-saturated photosynthesis at a lower photon fluence rate (PFR) than 5°C plants when both groups were assayed at the same temperature (15°C). The photon fluence rates necessary to reach the compensation point and achieve light-saturated photosynthesis (I _c andI _k , respectively) increased with increasing incubation temperature inL. saccharina grown at both 5 and 15°C. However, acclimation responses to growth temperature compensated for the short-term effect of temperature onI _c andI _k . Consequently, plants grown at 5 and 15°C were able to achieve similar rates of light-limited photosynthesis, and similarI _c andI _k values at their respective growth temperatures. These responses are undoubtedly important for perennial seaweeds such asL. saccharina, which frequently grow in light-limited habitats and experience pronounced seasonal changes in water temperature.Please address all correspondence and requests for reprints to I.R. Davison     

Air Pollution in Singapore: Its Multielemental Aspect as Measured by Nuclear Analytical Techniques

Aerosol samples were collected in 1994 in Singapore on two occasions: once in June during the normal meteorological conditions and later in October during a long haze period caused by the heavy forest fire in Indonesia. Filtration and impaction collection methods were used simultaneously so that detailed elemental analysis of bulk as well as of different size fractions could be performed. Accelerator based nuclear analytical techniques such as Particle Induced X-Ray Emission (PIXE), Rutherford Backscattering (RBS) and Nuclear Microscopy (NM) were used for analysis. These techniques are fast, truly multielemental and perfectly suited for routine analysis of a large number of aerosol samples. Typically all samples were analysed for the following 24 elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Cr, Fe, Co, Ni, Cu, Zn, Ga, As, Br, Rb, Sr and Pb. Detection limits for bulk analysis were generally below ng/m3 and for single particle analysis absolute detectable mass was approximately 10-17 g. Additionally, trace elements such as Cd, Sn, Sb and Ba whose characteristic X-ray lines were normally "obscured" by the lines of other more abundant elements, were detected when analysing by nuclear microscope in single particle mode.Judging by the average concentrations of lead and sulphur which are good indicators of industrial component of air pollution the situation in Singapore is satisfactory. Pb was typically found in concentrations of 5 to 50 ng/m3 and sulphur in concentrations of 1 to 2 µg/m3. These concentrations are well below limits set by the World Health Organisation (1500 ng/m3 and 40 µg/m3, respectively). On the other hand during the haze period the average concentrations of elements like S, K, Ti, V, Mn, Ni, As and Pb were found to be 3 to 6 times higher than usual. Results are presented and discussed.     

Tree species in relation to soil moisture regime in northwestern Ontario,Canada

Selected data on site, vegetation cover, and soil, including soil moisture regime (SMR), were collected from 2 167 field plots in northwestern Ontario, Canada. SMR provides an estimate of an averaged, annualized soil moisture supply throughout a complete vegetation cycle. SMR is based upon a relative scale that subjectively ranks sites from , 0, and 1 through 9 along a soil moisture continuum which relates to a dry to wet gradient. SMR may be generally correlated to tree growth, stand composition, degree of competition, nutrient availability and overall site quality.This paper reports on relationships between SMR and major tree species. Results highlight relationships between SMR class and the broad ecological ranges of several tree species. In northwestern Ontario, the determination of SMR can help resource managers to better understand the ecology of boreal sites.     

Suspended particulates and bioaerosols emitted from an agricultural non-point source

Suspended particulate and bioaerosol levels were measured at three sites downwind of an agricultural non-point source during the wheat harvesting season. Suspended particulates were detected at mean values ranging from 10000 to 2420 micrograms m-3 at distances of from 20 to 60 m downwind of the source, respectively. Airborne viable bacterial counts were recorded at mean values ranging between 10(4) and 10(6) colony forming units (cfu) m-3, whereas, Gram negative (Gram -ve) bacteria varied between 10(3) and 10(5) cfu m-3. Fungi levels were detected at mean values varying between 10(5) and 10(6) cfu m-3. However, streptomycetes were found at lower counts than those recorded for viable bacteria and fungi. Total viable bacteria, Gram -ve bacteria, fungi and streptomycetes associated hay fragments were determined at mean values of 1.5 x 10(6), 1.6 x 10(3), 2.2 x 10(4) and 6 x 10(3) cfu g-1 of hay, respectively. Cladosporium, white and red yeasts as well as Alternaria were the predominant airborne fungi, whereas, Alternaria was the dominant species associated with hay fragments. Pseudomonas, Acinetobacter and Enterobacteriaceae were the dominant Gram -ve bacteria. The most common fungal genera, such as Cladosporium and Fusarium (minor short axis), as well as Streptomyces species have an aerodynamic diameter (dae) of less than 5 microns, which can penetrate and deposit in the alveoli. Farmers and nearby residents are exposed to high levels of organic dust and bioaerosols during the wheat harvesting season. This may cause health problems in exposed persons based on toxic or allergic reactions.     

Control of rumen methanogenesis

During the last decades, considerable research on methane production in the rumen and its inhibition has been carried out. Initially, as methane production represents a significant loss of gross energy in the feed (2–15%), the ultimate goal of such intervention in rumen fermentation was an increase in feed efficiency. A second reason favouring research on methane inhibition is its role in the global warming phenomenon and in the destruction of the ozone layer. In this review, the authors describe briefly several interventions for reducing methane emission by ruminants. The objective can be reached by intervention at the dietary level by ration manipulation (composition, feeding level) or by the use of additives or supplements. Examples of additives are polyhalogenated compounds, ionophores and other antibiotics. Supplementation of the ration with lipids also lowered methanogenesis. More biotechnological interventions, e.g., defaunation, probiotics and introduction of reductive acetogenesis in the rumen, are also mentioned. It can be concluded that drastic inhibition of methane production is not unequivocally successful as a result of several factors, such as: instantaneous inhibition often followed by restoration of methanogenesis due to adaptation of the microbes or degradation of the additive, toxicity for the host animal, negative effects on overall digestion and productive performance. Therefore, methanogenesis and its inhibition cannot be considered as a separate part of rumen fermentation and its consequences on the animal should be taken into account.     

Global and Regional Distribution of Carbon Monoxide from MOPITT: Seasonal Distribution at 700 hPa

The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer, which was launched on the Earth Observing System (EOS) Terra satellite in 1999. Carbon monoxide (CO) is one of the important trace gases because its concentration in the troposphere directly influences the concentrations of tropospheric hydroxyl (OH), which controls the lifetimes of tropospheric trace gases. CO traces the transport of global and regional pollutants from industrial activities and large scale biomass burning. The global and regional distributions of CO were analyzed using the MOPITT data for East Asia, which were compared with the ozone distributions. In general, seasonal CO variations are characterized by a peak in the spring, which decrease in the summer. This work also revealed that the seasonal cycles for CO are at a maximum in the spring and a minimum in the summer, with average concentrations ranging from 118 to 170 ppbv. The monthly average for CO shows a similar profile to that for O3. This fact clearly indicates that the high concentration of CO in the spring is possibly due to one of two causes: the photochemical production of CO in the troposphere, or the transport of the CO into East Asia. The seasonal cycles for CO and O3 in East Asia are extensively influenced by the seasonal exchanges of different air mass types due to the Asian monsoon. The continental air masses contain high concentrations of O3 and CO, due to the higher continental background concentrations, and sometimes to the contribution from regional pollution. In summer this transport pattern is reversed, where the Pacific marine air masses that prevail over Korea bring low concentrations of CO and O3, which tend to give the apparent summer minimums.     

Development of an ombrotrophic peat bog (low ash) reference material for the determination of elemental concentrations

Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material (i.e. collection and preparation, homogeneity and stability studies, and certification) are described in detail.     

The fate of fipronil in modular estuarine mesocosms

The degradation and corresponding product manifold for the pesticide fipronil was determined in three replicate estuarine mesocosms. Aqueous fipronil concentrations rapidly decreased over the 672 h timescale of the experiment (95% removal). Loss was apparently first-order in fipronil, although there appeared to be a change in the removal mechanism after 96 h that corresponded to a dramatic slowdown in its disappearance. The reduction product of fipronil, fipronil sulfide, was not detected in the water column; however, it formed rapidly in sediments and was identified as the major product of fipronil degradation in the system (20% yield at 672 h, with respect to initial fipronil concentration). Fipronil sulfone is thought to form primarily via biological oxidation; and, although it was generated rapidly in the water column (10% yield), only trace amounts were detected in the sediment (1% yield). The direct photolysis product of fipronil, fipronil desulfinyl, was present in all samples; it formed rapidly in the water column (4% yield) and partitioned into the sediment phase (7% yield) over the course of the experiment. The mass balance on fipronil and associated products was 42% at 672 h.