Primary production in three lakes of differing salinity in Victoria,Australia

Lakes Purrembete, Bullenmerri and Gnotuk are relatively deep lakes with salinities of 0.4, 8 and 58 respectively. From Carbon-14 experiments conducted monthly over a year annual primary production was 96.2, 182.1 and 90.1 gCm^-2. These values correlate well with chlorophyll-a in Purrumbete and Bullenmerri, but not in Gnotuk. There is considerable dark fixation in both the saline lakes.     

Use of15N/14N rations to evaluate the food source of the mysid,Neomysis intermedia Czerniawsky,in a eutrophic lake in Japan

The stable isotope ratios of nitrogen were measured in the mysid,Neomysis intermedia, together with various biogenic materials in a eutrophic lake, Lake Kasumigaura, in Japan throughout a year of 1984/85. The mysid, particulate organic matter (POM, mostly phytoplankton), and zooplankton showed a clear seasonal change in ¹⁵N with high values in spring and fall, but the surface bottom mud did not. A year to year variation as well as seasonal change in ¹⁵N was found in the mysid. The annual averages of ¹⁵N of each material collected in 1984/85 are as follows: surface bottom mud, 6.3 (range: 5.7–6.9); POM, 7.9 (5.8–11.8); large sized mysid, 11.6 (7.7–14.3); zooplankton, 12.5 (10.0–16.4); prawn, 13.2 (9.9–15.4); goby, 15.1 (13.8–16.7). The degree of¹⁵N enrichment by the mysid was determined as 3.2 by the laboratory rearing experiments. The apparent parallel relationship between the POM and the mysid in the temporal patterns of ¹⁵N with about 3 difference suggests the POM (mostly phytoplankton) as a possible food source ofN. intermedia in this lake through the year.     

Stable isotope and radiocarbon compositions of methane emitted from tropical rice paddies and swamps in Southern Thailand

Stable isotopes (¹³C, D) and radiocarbon weremeasured in methane bubbles emitted from rice paddies and swamps in southernThailand. Methane emitted from the Thai rice paddies was enriched in¹³C (mean ¹³C; –51.5 ±7.1 and–56.5 ± 4.6 for mineral soil and peat soil paddies,respectively)relative to the reported mean value of methane from temperate rice paddies(– 63 ± 5). Large seasonal variation was observed in¹³C(32) in the rice paddies, whereas variationinD was much more smaller (20), indicating that variation in¹³C is due mainly to changes in methane production pathways.Values of ¹³C were lower in swamps (–66.1 ±5.1)than in rice paddies. The calculated contribution of acetate fermentation from¹³C value was greater in rice paddies (mineral soils:62–81%, peat soils: 57–73%) than in swamps (27–42%). Din methane from Thai rice paddies (–324± 7 (n=46)) isrelativelyhigher than those from 14 stations in Japanese rice paddies ranging from–362 ± 5 (Mito: n=2) to –322 ± 8(Okinawa: n=3), due tohigher D in floodwaters. ¹⁴C content in methane produced fromThai rice paddies (127±1 pMC) show higher ¹⁴Cactivity compared with previous work in paddy fields and those from Thai swamps(110±2 pMC).     

Hydrogen isotope discrimination in higher plants: Correlations with photosynthetic pathway and environment

Summary The ratio of deuterium to hydrogen (expressed as D) in hydrogen released as water during the combustion of dried plant material was examined. The D value (metabolic hydrogen) determined on plant materials grown under controlled conditions is correlated with pathways of photosynthetic carbon metabolism. C₃ plants show mean D values of-132 for shoots and -117 for roots; C₄ plants show mean D values of -91 for shoots and-77 for roots and CAM plants a D value of-75 for roots and shoots. The difference between the D value of shoot material from C₃ and C₄ plants was confirmed in species growing under a range of glasshouse conditions. This difference in D value between C₃ and C₄ species does not appear to be due to differences in the D value (tissue water) in the plants as a result of physical fractionation of hydrogen isotopes during transpiration. In C₃ and C₄ plants the hydrogen isotope discrimination is in the same direction as the carbon isotope discrimination and factors contributing to the difference in D values are discussed. In CAM plants grown in the laboratory or collected from the field D values range from-75 to +50 and are correlated with ¹³C values. When deprived of water, the D value (metabolic hydrogen) in both soluble and insoluble material in leaves of Kalanchoe daigremontiana Hamet et Perr., becomes less negative. These changes may reflect the deuterium enrichment of tissue water during transpiration, or in field conditions, may reflect the different D value of available water in areas of increasing aridity. Whatever the origin of the variable D value in CAM plants, this parameter may be a useful index of the water relations of these plants under natural conditions.     

Competition between the sibling species Tisbe holothuriae and T. battagliai (Harpacticoida)

The influence of salinity on the performance of the sibling species Tisbe holothuriae and T. battagliai in pure and mixed cultures was studied, using laboratory stocks adapted to 32 for over 175 generations. Cohort studies show that T. holothuriae has higher growth rates (R_o and r) at 32, T. battagliai at 20 The latter's life cycle is much less affected by the difference in salinity. De Wit replacement series were used to study competitive interactions. Without water renewal, T. holothuriae eliminates its sibling species in less than 2 generations, apparently through chemical interference. With water renewal, i.e. when exploitation competition becomes relatively more important, T. holothuriae still proves superior at 27 but the two species are competitively almost equal at 20. The two species cooccur in situ during autumn, but their differential predominance at different sites is not explained by the effect of salinity.     

Stable isotope ratio as a tracer of mangrove carbon in Malaysian ecosystems

Summary The ratio of stable carbon isotopes (¹³C) in plants and animals from Malaysian mangrove swamps, coastal inlets, and offshore waters was determined. Vascular plants of the swamps were isotopically distinct ( x±s.d.=-27.1±1.2) from plankton (-21.0±0.3) and other algae (-18.7±2.2). Animals from the swamps (-20.9±4.1) and inlets (-19.8±2.5) had a wide range of isotope ratios (-28.6 to-15.4), indicating consumption of both mangrove and algal carbon. Several commercially important species of bivalves, shrimp, crabs, and fish obtained carbon from mangrove trees. Mangrove carbon was carried offshore as detritus and was isotopically distinguishable in suspended particulate matter and sediments. Animals collected from 2 to 18 km offshore, however, showed no isotopic evidence of mangrove carbon assimilation, with ratios (-16.5±1.1, range-19.1 to-13.1) virtually identical to those reported for similar animals from other plankton-based ecosystems. Within groups of animals, isotope ratios reflected intergencric and interspecific differences in feeding and trophic position. In particular, there was a trend to less negative ratios with increasing trophic level.     

Variations in the natural abundance of 15N in ryegrass/white clover shoot material as influenced by cattle grazing

Biological N2 fixation in clover is an important source of N in low external-N input farming systems. Using the natural 15N-abundance method, variations in N2 fixation were investigated in grazed and mowed plots of a ryegrass/white clover field. Ryegrass 15N varied considerably, from 0.2 to 5.6 under mowed conditions and from –3.3 to 11.6 under grazed conditions. Variations in 15N white clover were lower than in ryegrass, especially in the mowed plots (SE = 0.05, n = 20). The variations in the percentage of nitrogen derived from the atmosphere (%Ndfa) in white clover were highest in the grazed plots where it ranged from 12 to 96% (mean = 64%) compared with the mowed plots where it ranged from 64 to 92% (mean = 79%). Thus, the N2 fixation per unit white clover DM in the grazed ley was lower and more variable than under mowing conditions.Urine from dairy cows equivalent to 0, 200, 400 and 800 kg N ha-1 was applied to a ryegrass/white clover plot 6, 4 or 2 weeks before harvest. Without urine application 15N of ryegrass was positive. By increasing urine application (15N = –1) two weeks before sampling, the 15N of ryegrass decreased strongly to about –7 (P < 0.001). However, this effect was only observed when urine was applied two weeks before sampling. When applying 800 kg N four and six weeks before sampling, 15N in ryegrass was not significantly different from the treatment without urine application. White clover 15N was unaffected by whatever changes occurred in 15N of the plant-available soil N pool (reflected in 15N of ryegrass). This indicates that within the time span of this experiment, N2 fixation per unit DM was not affected by urine. Therefore, newly deposited urine may not be the main contributing factor to the variation in %Ndfa found in the grazed fields. This experiment suggested that the natural abundance method can be applied for estimating %Ndfa without disturbance in natural animal-grazed systems.     

Über den Einfluß des Salzgehaltes auf die photosynthetische Leistung verschiedener Standortformen vonDelesseria sanguinea undFucus serratus

Zusammenfassung 1. Es wurde untersucht, welchen Einfluß kurzfristige und langfristige Salzgehaltsveränderungen auf verschiedene Standortformen der RotalgeDelesseria sanguinea und der BraunalgeFucus serratus haben. Als Kriterium des Lebenszustandes wurde die photosynthetische Leistung gewählt. Die Algen wurden folgenden Salzgehaltskonzentrationen ausgesetzt: 0, 5, 10, 15, 20, 30, 40, 50 S.2. Die Versuche ergaben, daß kurzfristige Konzentrationsveränderungen (30 min) — sowohl Erniedrigung als auch Erhöhung des Salzgehaltes — die photosynthetische Leistung stimulieren. Ein langfristiger Aufenthalt (24 Std) unter den veränderten Bedingungen bewirkt, sofern diese innerhalb der Toleranzgrenzen der Algen liegen, einen Ausgleich der anfänglichen Stimulation. Außerhalb der Toleranzgrenzen liegende Konzentrationen rufen nach der Stimulation eine Leistungsdepression hervor. Bei Rückübertragung in den Ausgangssalzgehalt sind die Depressionen teilweise reversibel.3. Im hypotonischen Milieu verhalten sich die Delesserien der verschiedenen Standorte (Helgoland, Kattegat, Kieler Bucht) gleich: in 5 S treten starke Depressionen auf. Nordsee-Delesserien sind im hypertonischen Milieu weniger empfindlich, sie zeigen noch bei 50 S eine gesteigerte photosynthetische Leistung. In diesem Bereich sind die Ostseeformen schon schwer geschädigt. Am empfindlichsten gegenüber allen Konzentrationsänderungen ist die BrackwasserformDelesseria sanguinea formalanceolata aus der Kieler Bucht.4.Fucus serratus aus dem Litoral von Helgoland zeichnet sich im Gegensatz zu der submers lebenden Form der Ostsee, die sich ähnlich wieDelesseria verhält, in allen untersuchten Konzentrationsbereichen durch eine unveränderte photosynthetische Leistung aus. Die beiden Standortformen vonFucus entsprechen gemäß der Einteilung vonMontfort (1931) dem resistenten Typ und dem Stimulations-Depressionstyp.

---

On the influence of salinity on photosynthetic performance of various ecotypes ofDelesseria sanguinea andFucus serratus

The phaeophyceanF. serratus and the rhodophyceanD. sanguinea came from the North Sea (30 S) and the Baltic Sea (15 S). The activity of photosynthesis was taken as a criterion of algae vitality. Experiments were made in salinity concentrations of 0, 5, 10, 15, 20, 30, 40 and 50 S. Thirty-minute exposures to sub- or supranormal salinities stimulate photosynthesis. Within their physiological salinity ranges the algae assume normal photosynthetic rates within 24 hours. Extreme salinities cause a reduction in photosynthetic activity; this reduction mostly disappears, however, after re-transfer into normal salinity conditions. At 5 S all test individuals ofDelesseria from different locations exhibit a reduction of photosynthetic rates. At 50 SDelesseria from the North Sea still show increased activity, whileDelesseria from the Baltic are already severely damaged. The brackish-water formD. sanguinea (formalanceolata) is most sensitive to salinity variations. The photosynthetic activity ofF. serratus from Helgoland does not vary in all salinities employed. The range of test salinities corresponds to that of the habitat in the littoral zone, where high salinities occur during air exposure, and low salinities, during rainfall. By contrast, inF. serratus from the Baltic Sea occurring only in the sublittoral zone, photosynthetic rates are similarly affected by salinity as inDelesseria.

     

Effects of salinity on metabolism and life history characteristics of Daphnia magna

In the Baltic Sea area, the cladoceran Daphnia magna is commonly found in brackish water rockpools and it has been suggested that salinity is one of the niche dimensions that affects the distribution of the species. The salinity tolerance of D. magna was studied both in physiological and life history experiments. The experimental salinities were freshwater, 4S and 8S. The highest respiration and ammonium excretion rates were measured in the freshwater treatment with decreasing respiration and ammonium excretion rates at higher salinities. The lowest O/N ratio (oxygen consumption to ammonium excretion), describing the metabolic status of an organism, was obtained at 8S, although the only significant differences were detected when comparing to 4S treatments. Individual growth rate, reproductive output and population growth rate were highest at 4S. At 8S growth and reproduction were reduced as compared to freshwater and 4S. The life history parameters in the performed experiments indicated higher fitness (expressed as r) as well as more favourable conditions for growth and reproduction at 4S, whereas the O/N ratio was more difficult to interpret and, in this case, gave a less clear picture of the salinity influence.     

The Use of the [13C]/[12C] Ratio for the Assay of the Microbial Oxidation of Hydrocarbons

The study deals with a comparative analysis of the relative abundances of the carbon isotopes ¹²C and ¹³C in the metabolites and biomass of the Burkholderia sp. BS3702 and Pseudomonas putida BS202-p strains capable of utilizing aliphatic (n-hexadecane) and aromatic (naphthalene) hydrocarbons as sources of carbon and energy. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of Burkholderia sp. BS3702 on n-hexadecane (¹³C = –44.6 ± 0.2) were characterized by the values of ¹³C_{CO 2} = –50.2 ± 0.4, ¹³C_biom = –46.6 ± 0.4, and ¹³C_exo = –41.5 ± 0.4, respectively. The isotope compositions of the carbon dioxide, biomass, and exometabolites produced during the growth of the same bacterial strain on naphthalene (¹³C = –21 ± 0.4) were characterized by the isotope effects ¹³C_{CO 2} = –24.1 ± 0.4, ¹³C_biom = –19.2 ± 0.4, and ¹³C_exo = –19.1 ± 0.4, respectively. The possibility of using the isotope composition of metabolic carbon dioxide for the rapid monitoring of the microbial degradation of petroleum hydrocarbons in the environment is discussed.