Photosynthetic responses to inorganic carbon in Ulva lactuca under aquatic and aerial states

Intertidal macroalgae experience continual alternation of photosynthesis between aquatic state at high tide and aerial state at low tide. The comparative photosynthetic responses to inorganic carbon were investigated in the common intertidal macroalga Ulva lactuca L. along the coast of Shantou between aquatic and aerial state. The inorganic carbon dissolved in seawater at present could fully (at 10 degreesC or 20 degreesC) or nearly (at 30 degreesC) saturate the aquatic photosynthesis of U. lactuca. However, the aerial photosynthesis was limited by current ambient atmospheric CO2 level, and such a limitation was more severe at higher temperature (20degrees - 30degrees T) than at lower temperature (10 T). The carbon-saturated maximal photosynthesis of U. lactuca under aerial state was much greater than that under aquatic state at 10 degreesC and 20 degreesC, while the maximal photosynthesis under both states was similar at 30 degreesC. The aerial values of K-m (CO2) for photosynthesis were higher than the aquatic values. On the contrary, the values of apparent photosynthetic CO2 conductance under aerial state were considerably lower than that under aquatic state. It was concluded that the increase of atmospheric CO2 would enhance the primary productivity of U. lactuca through stimulating the photosynthesis under aerial state during low tide.

Genome mapping in aquatic animals: Progress and future perspectives

The genome of aquatic animals is poorly understood and information from different taxonomic groups is sketchy. While there have been intensive genomic studies on some fish models, investigations on other fishes and invertebrates have been scarce. Yet there are recently some coordinated studies on genome mapping in a number of aquaculture animals of economic importance. This review summarizes information available on genome mapping of the important fish models and aquaculture animals. The future perspectives of this field of studies are discussed.

Effects of the stocking density and body size of the mitten crab (Eriocheir sinensis) on aquatic plant biomass

Experiments in tanks and cages were conducted to examine the effects of stocking density and body size of the Mitten crab (Eriocheir sinensis) on transplanted submersed macrophyte biomass. The early juvenile crab with 7.0 +/-0.6 mm. carapace width (CW) had little effect on plant biomass, regardless of the stocking densities. However, larger crabs (CW: 18.0 +/-2.2,35.0 +/-3.6, and 60.0 +/-5.7 mm) significantly influenced plant biomass, especially at large stocking densities. Predictive models, using crab body size and stocking density, were generated to demonstrate effect of the mitten crab on the changes Of plant biomass. The results indicate that dense mitten crab populations may adversely affect aquatic plant communities, particularly when its animal food resources are scarce.

The role of plants in channel-dyke and field irrigation systems for domestic wastewater treatment in an integrated eco-engineering system

Eight kinds of plants were tested in channel-dyke and field irrigation systems. The removal rates of TP, phosphate, TN, ammonia, CODcr and BOD, in the channel-dyke system with napiergrass (Pennisetum purpurem Schumach, x Pennisetum alopecuroides (L.) Spreng American) were 83.2, 82.3, 76.3, 96.2, 73.5 and 85.8%, respectively. The field irrigation systems with rice I-yuanyou No.1(88-132) (Oryza sativa L.) and rice II- suakoko8 (Oryza glaberrima) had high efficiency for N removal; the removal rate were 84.7 and 84.3%, respectively. The mass balance data revealed that napiergrass, rice I and II were the most important nutrient sinks, assimilating more than 50% of TP and TN. Plant uptake of N and P as percentage of total removal from wastewater correlated with biomass yield of and planting mode. (C) 2000 Elsevier Science B.V. All rights reserved.

The distribution of monogenean parasites on aquatic vertebrates inhabiting Chinese inland waters

The general distribution of monogenean parasites of aquatic vertebrates inhabiting Chinese inland waters is summarised. Five hundred and seventy-two out of a total of 581 species of monogeneans were discovered on fish, while only nine species were found on Amphibia and Reptilia. Most dactylogyrids and diplozoids parasitise cyprinids, while ancyrocephalids occur on silurids and cyprinids, and gyrodactylids are found mainly on cyprinids and cobitids. Analyses of host-specificity and host-diversity suggests that the family Ancyrocephalidae should be divided into several families parallel with the Dactylogyridae. Of 12 subfamilies of the Cyprinidae, only the Gobiobotinae was found to be free of infection with monogeneans, and the genus Dactylogyrus has more species than any other monogenean genus associated with every cyprinid subfamily.

MOBILITY AND TRANSFER OF RESIDUAL HEXACHLOROCYCLOHEXANE (HCH) IN AQUATIC ENVIRONMENT

An investigation was carried out to study the mobility and transfer of HCH-residues in Yanjia lake, Hubei, China, from 1990-1993. By sampling at different locations, the horizontal distribution of HCH-residues was determined; by sampling at different depths in the same location, the vertical mobility of HCH-residues and its penetration were measured. The vertical profiles of HCH-residues in sediment showed a gradient distribution, which was reduced with the increase in depth. This was very similar in shape to the organic carbon and nitrogen content profiles. The penetration of HCH-residues was measured as 60cm approximately. Meanwhile, water, sediment (0-12cm), benthos and benthic fish collected from the lake were analyzed to determine the transfer of HCH-residues along aquatic food chain. The BCF values of HCH-residues indicated that the bioaccumulation of HCH-residues in freshwater food chain still exsisted in spite of the banning of HCH since 1983. The maxium BCF value of HCH-residues in the liver samples of 5-year-old common carp was up to 61966 (calculated by beta-HCH).

A colorimetric assay for screening microcystin class compounds in aquatic systems

Secondary metabolites produced by water-blooming cyanobacteria in eutrophic waters include some potent hepatotoxins, These compounds also have tumour-promoting properties, attributable to their inhibition and activation of protein phosphatases and kinases respectively. The inhibitory effect of these toxins on protein phosphatases have been employed in a commonly used radiometric assay, involving the use of a P-32-labeled substrate, for the detection and quantitation of these compounds. This paper investigates and describes a colorimetric method in which the activity of protein phosphatase 2A is determined by measuring the rate of colour production from the release of yellow p-nitrophenol using p-nitrophenyl phosphate as the substrate. Results of this study suggest that the colorimetric protein phosphatase inhibition assay is a simple, inexpensive tool for screening substances that may have tumour-promoting characteristics in aquatic systems. The detection limit of the colorimetric method is comparable to the radiometric assay. (C) 1998 Elsevier Science Ltd. All rights reserved.