Simulation study of phytoplankton photosynthesis and growth in the Fraser River estuary

Phytoplankton photosynthesis was estimated by a simulation model of the Fraser River estuary (Canada). For this estimation, two kinds of information were considered; (1) the photosynthetic response of phytoplankton taken from the estuary to each environmental factor; (2) actual measurement of changes in each environmental factor in the estuary. As the major limiting factors, light intensity, temperature, and nitrate were taken into account. Variations in these parameters were combined together under the assumption of the law of the minimum; that is, only one of the environmental factors was considered to limit photosynthesis at any given time and place. From the results obtained, it could be shown which environmental factors actually limited phytoplankton photosynthesis in the Fraser River estuary at different times of the year and at different depths.     

长江口浮游植物分布情况及与径流关系的初步探讨

利用2004—2008年5月（春季）和8月（夏季）共10个季度月航次调查资料,结合同时期长江口径流量的数据,研究了长江口海域浮游植物的分布特征、及其受长江径流影响的关系。分布情况的结果显示：同一年中,夏季调查航次鉴定的浮游植物种类数明显多于春季的种类数;浮游植物数量的基本趋势逐年增加,其中2008年调查航次的浮游植物数量急剧暴发;同时生物多样性指数呈逐年下降趋势,海域水质污染程度日趋严重。对浮游植物与长江口径流量的关系分析得到：拟合长江口5、8月平均径流量与对应调查航次的浮游植物数量呈正相关的幂函数关系,径流量与浮游植物多样度呈负相关的指数函数关系,径流量与浮游植物优势种数量百分比呈正相关的幂函数关系,关系都明显显著。其中长江口径流量的输入对优势种尤其是近岸低盐性的中肋骨条藻（Skeletonema costatum）分布有着决定性的影响;长江径流把大量的N、P等无机营养物质携带入海,导致长江口水域严重富营养化,造成长江口海域的局部区域频发赤潮。     

Comparative study of the carbon cycle in Venus verrucosa fed on bacteria and phytoplankton

The aim of this, the third part of our study, was to compare the quantities of food consumed and assimilated by Venus verrucosa L. fed on two different living suspensions: the bacterium Lactobacillus sp. and the alga Pavlova lutheri. The experimental results have been presented in parts I and II of our study. The present paper describes a model constructed for each series of experiments with bacteria and with phytoplankton. An analog-computer model was succesfully applied and revealed that bacterial food was more easily consumed and assimilated than algal food, the dissolved form more easily assimilated than the living particulate form.     

Comparative study of the carbon cycle in Venus verrucosa fed on bacteria and phytoplankton

Following a previous study, this paper deals with the utilisation of a phytoplankton suspension (Pavlova lutheri) by the clam Venus verrucosa Linné, 1767 as a function of time. Experimental clams filtered and ingested 100% of the suspension after 2 h. The radioactivity recovered in the whole soft body of the clams was 83.8% after 2 h, 66.0% after 10 h and 46.0% after 41 h. The faeces contained 13.7% after 3 h and 34.3% after 41 h. Carbon-dioxide radioactivity (gas plus dissolved) increased slowly to 12.4% after 41 h. When the water was not changed after 17 h, the clams reabsorbed a great part of their dissolved products and faeces. Under these latter conditions the radioactivity recovered from the whole soft body of the clams was roughly the same as that recovered after the start of the experiment. The aim of this study was the comparison of the consumption of two kinds of food: bacteria and phytoplankton. The work was carried out over three years, from 1977 to 1980.     

Comparative study of the carbon cycle inVenus verrucosa fed on bacteria and phytoplankton

The utilisation of a viable bacterial suspension (Lactobacillus sp.) by the clamVenus verrucosa Linné, 1767 has been investigated as a function of time. The clams filtered and ingested 95% of the suspension within 2 h. Radioactivity recovered from the soft-body of the clams measured 51% of the total radioactivity introduced at the start of the experiment after 2.5 h, 48.8% after 10 h, and 39.9% after 40 h. The dissolved organic matter remained nearly constant, with 27.5% after 2.5 h, 24.4% after 10 h, and 29.8% after 40 h. The faeces produced increased from 13.2% after 2.5 h to 21.9% after 10 h, and decreased until 40 h with 16.2%. The carbon-dioxide respired increased slowly to 5% after 40 h. These data on the functioning of the different compartments suggest an important recycling of the metabolic products of the bivalves by the bacteria of the suspension, demonstrating the role of bacteria as food for bivalves.     

Uptake and release of phosphorus by phytoplankton in the Chesapeake Bay estuary,USA

The phytoplankton uptake and release rates for inorganic phosphate, dissolved organic phosphate and polyphosphate were estimated during 5 cruises on the Chesapeake Bay over a 9-month period. Phosphorus in all pools turned over in several minutes to 100 h, and each soluble pool appeared to contain fractions which were metabolically useful to the phytoplankton. Maximal uptake rates (V _m ) for orthophosphate ranged from 0.02 to 2.95 μg-at P (1.h)^-1 with half saturation constants (K _s ) between 0.09 and 1.72 μg-at P l^-1. At low soluble reactive phosphorus concentrations, the uptake rate of trace ³²P orthophosphate was initially rapid, but declined after 15 to 60 min incubation. The data suggest that the initial uptake phase was dominated by exchange of ³²PO₄ ^≡ for ³¹PO₄ ^≡ in the membrane transport systems whereas the subsequent phase represented the net incorporation of orthophosphate into phytoplankton cells.     

The effect of Po river discharge on phytoplankton dynamics in the Northern Adriatic Sea

An oceanographic transet,, extending from Yugoslavia across the Northern Adriatic Sea to the Po delta in Italy, was occupied during 1972 and 1973 to establish the effect of Po river discharge on the phytoplankton communities of the region. Density distribution showed distinct seasonal features: a winter-spring period of low stability throughout the water column, and a summer period of stratification. The total water-column plant nutrients (nitrate, nitrite, phosphate, silicate) showed a 1.3 to 4.5-fold decrease eastward, with semi-eutrophic conditions restricted to an area off the Po delta. Nannoplankton usually dominated the phytoplankton community, in terms of cell density, surface chlorophyll a concentrations, and surface primary production rates. However, all significant maxima in these characteristics resulted from increases in the microplankton component. Changes in the frequency of major microplankton groups characterized three periods of the annual cycle: September–December, neritic, temperate diatom flora with some littoral elements (e.g. Nitzschia seriata); January–May, neritic, temperate diatom flora of different composition (e.g. Lauderia borealis, Skeletonema costatum); May–August, dinoflagellates (e.g. Prorocentrum micans) at western stations and dinoflagellates plus neritic, warm-water diatoms at eastern stations. The seasonal cycle was characterized by spring and fall maxima tending to coincide with maximum Po river discharge and/or periods of low water-column stability and vertical mixing. The higher nutrient input at western stations was correlated with the co-dominance of only a few species of microplankton during bloom periods, suggesting that these species (S. costatum, N. seriata, and 5 others) can serve as indicators of eutrophic conditions in this region. Assimilation ratios of both the micro- and nannoplankton suggested borderline nutrient conditions. Phosphate was implicated as the limiting nutrient.     

Distribution and behaviour of polycyclic aromatic hydrocarbons in subtropical river estuary,Okinawa, Japan

Surface water samples were collected along the salinity gradient of Manko estuary in Okinawa, Japan, between January and November 2012, to examine spatial and temporal variability in the distribution, composition, behaviour, and sources of particulate polycyclic aromatic hydrocarbons (PAHs). Concentrations of total particulate PAHs ranged from 169.7?ng?g^?1 at riverine station (N1) in November 2012 to 922?ng?g^?1 at another riverine station (K3) in May 2012. Based on observed environmental behaviour, particularly relationships to organic matter, the PAHs appear divisible into two groups: group I (low molecular weight) PAHs were characterised by low particles affinity and strong correlations with a pool of autochthonous organic matter (e.g. high concentrations of polyunsaturated fatty acids), reflecting processes controlling their delivery to the estuary; and, in contrast, group II (high molecular weight) PAHs were characterised by high particles affinity and exhibited estuarine distribution primarily controlled by suspended solid load and inputs from terrigenous sources through river inflows. This relationship, coupled with isomer ratios indicative of combined mixed sources from petroleum and petroleum combustions, indicates that terrestrial run-off is the dominant mode of delivery of particulate PAHs in the estuary. The relationships between distinct groups of PAHs and lipid biomarkers demonstrated in this study suggest that very specific pools of particulate organic matter, as opposed to concentrations of particulate organic carbon alone, can be important in the transport and fate of hydrophobic contaminants.     

Preliminary study on the consumption of dissolved organic matter (exudates) of bacteria and phytoplankton by the marine bivalve Venus verrucosa

The utilisation of the exudates of bacteria (Lactobacillus sp.) and phytoplankton (Pavlova lutheri) by the clam Venus verrucosa Linné under identical experimental conditions was studied. 61.7% of the bacterial exudates were consumed but only 19.9% of the algal exudates. V. verrucosa would seem to assimilate bacterial products more easily than phytoplankton exudates. The study was performed in 1980.     

浮游植物细胞程序化死亡研究进展

过去,动物摄食和沉降被认为是浮游植物死亡的原因。后来人们发现病毒感染以及逆境条件下的主动死亡(或程序化死亡),也是引起浮游植物死亡的重要原因。文章介绍了浮游植物存在细胞程序化死亡的实验证据和半胱氨酰天冬氨酸特异蛋白酶(caspase)在浮游植物细胞程序化死亡中可能起的作用及浮游植物基因组中的caspase直系同源物。程序化死亡是细胞自主死亡的过程,具有坏死的形态和生物化学过程。浮游植物具有一套后生动物caspase的直系同源物蛋白。作者构建了东海原甲藻cDNA文库,其中有两组EST分别与两个细胞程序化死亡的关键蛋白同源,它们分别是半胱氨酰天冬氨酸特异蛋白酶和分裂细胞核抗体。因此作者推断东海原甲藻可能存在细胞程序化死亡过程。尽管已从细胞生物学特征角度,获得了真核微藻程序化死亡的证据,并从基因组序列中预测出和大规模表达序列标签中鉴定出细胞程序化死亡相关蛋白的编码基因,但离全面认识单细胞真核浮游藻程序化死亡的分子机制以及其生态学意义相差甚远。     

Distribution of phytoplankton community and its influence factors in an urban river network,East China

To reveal the distribution characteristics of phytoplankton and the main influence factors under different conditions in the urban rivers, the investigations were conducted during autumn and winter 2014 in Changzhou City, East China. 178 taxa of phytoplankton belonging to 28 functional assemblages were identified. In autumn, the phytoplankton community compositions have high similarity for enhanced hydrological connectivity. The chlorophytes and diatoms (prevailing functional groups C, F, J, P), together with euglenoids (W1), showed high proportions of biomass in the main rivers and connected rivers. It was related to the well mixed eutrophic conditions. The phytoplankton community exhibited spatiotemporal heterogeneity in winter. Affected by the low water level and temperature, the free-living phytoflagellates (X2) replaced groups F and J in the main rivers. Phytoplankton productivity was the highest in the Tongji River. Chlorophytes Dictyosphaerium ehrenbergianum and Chlamydobotrys stellata had an overwhelming superiority during the winter bloom. They were significantly correlated with ammonium, total phosphorus and biochemical oxygen demand. Affected by tail water supply, the diatoms (MP) and euglenoids (W1) dominated in a beheaded river. The multivariate analyses based on the phytoplankton functional groups helped to evaluate the relationships and variations between the urban rivers. The redundancy analysis (RDA) results showed that nitrate nitrogen, water temperature, total nitrogen and total suspended solids were the main influence factors on the phytoplankton community. Except MP, the prevailing groups all showed significant negative correlations with nitrate nitrogen. Availability and utilization of dissolved inorganic nitrogen and hydrodynamic conditions affected the phytoplankton distribution.

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Autoradiographic study of feeding and the colonial transport of metabolites in the marine bryozoan Membranipora membranacea

Standard autoradiographic techniques were adapted to study the transport of carbon compounds in colonies of Membranipora membranacea (L.). The results indicate that there is transport of carbon-14 between polypides within a colony. Metabolite movement is generally in the direction of the rapidly growing colony edge. Estimates of metabolite transport rates are given.     

Risk assessment of pharmaceutically active compounds (PhACs) in the Klang River estuary,Malaysia

Environmental Geochemistry and Health - The concentration profile, distribution and risk assessment of pharmaceutically active compounds (PhACs) in the coastal surface water from the Klang River...     

Using GIS to study the coastal geomorphology of the Acheloos river mouth in West Greece

In this paper the counteractive dynamic marine and river environments responsible for a river mouth’s and a delta’s modulation is studied. The Acheloos River (West Greece) was chosen as the case study due to the recent changes taken place in its basin. The aim of this study is to analyze the present dominant environment and the impact of human activity on this balance. A GIS database was developed and updated in order to provide access for future use and computer analysis (both spatial and chronological). The study, includes an estimation of the delta forming processes, the impact of the anthropogenic parameters on these processes, and, finally, their representation.     

Physico-chemical characteristics of the Vellar estuary in relation to shrimp farming

All the physico-chemical parameters such as temperature, LEC, salinity, pH, dissolved oxygen and nutrients like total phosphorus, inorganic phosphate, nitrite and silicate studied in relation to shrimp farming. There are as many as 42 shrimp farms situated on the banks of Vellar estuary. These farms discharge the used water into the estuary, which may influence the biota there. In the present study the physico-chemical feature in relation to shrimp farming were studied in 3 stations of the estuary. When compared with the previous data from Vellar estuary there was no much difference in physico-chemical characteristics due to shrimp farming.     

Observations on phytoplankton productivity in relation to hydrography in the Northern Adriatic

This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.     

Diversity and vertical distributions of sediment bacteria in an urban river contaminated by nutrients and heavy metals

The aim of this study was to investigate the benthic bacterial communities in different depths of an urban river sediment accumulated with high concentrations of nutrients and metals. Vertical distributions of bacterial operational taxonomic units （OTUs） and chemical para- meters （nutrients： NH4＋, NO3, dissolved organic carbon, and acid volatile sulfur; metals： Fe, Zn, and Cu） were characterized in 30 cm sediment cores. The bacterial OTUs were measured using the terminal restriction fragment length polymorphism analysis. Biodiversity indexes and multivariate statistical analyses were used to characterize the spatial distributions of microbial diversity in response to the environmental parameters. Results showed that concentrations of the nutrients and metals in this river sediment were higher than those in similar studies. Furthermore, high microbial richness and diversity appeared in the sediment. The diversity did not vary obviously in the whole sediment profile. The change of the diversity indexes and the affiliations of the OTUs showed that the top layer had different bacterial community structure from deeper layers due to the hydrological disturbance and redox change in the surface sediment. The dominant bacterial OTUs ubiquitously existed in the deeper sediment layers （5-27 cm） corresponding to the distributions of the nutrients and metals. With much higher diversity than the dominant OTUs, the minor bacterial assemblages varied with depths, which might be affected by the sedimentation process and the environmental competition pressure.     

Growth and spawning in the pectinid Chlamys opercularis in relation to temperature and phytoplankton concentration

Groups of queens, Chlamys opercularis (L.), were maintained under semi-natural conditions for a period of 18 months while growth rates and spawning conditions were monitored. Temperature and phytoplankton standing crop (as chlorophyll a) were also measured. The data suggest that only 1 major growth ring is formed in 1 year (in spring), although disturbance rings may be present. Rings are the result of the build-up of a number of small growth increments (striae) formed as successive lamellae are laid down. One lamella is probably laid down during 1 day, but a lamella is not necessarily laid down every day. Lamellae are laid down most regularly when temperature is moderately high and food availability is good. It seems likely, however, that poor food availability can limit growth and thus restrict the formation of lamellae even under field conditions. Spawning does not seem to induce the formation of growth checks.     

A field study of interfacial friction and entrainment in a microtidal salt-wedge estuary

Environmental Fluid Mechanics - The interfacial friction and entrainment were investigated in a microtidal salt-wedge estuary. A detailed sampling campaign was conducted in the Rječina River...     

A comparative study of the glutamate dehydrogenase activity in several species of marine phytoplankton

Kinetic studies on the NADP-linked glutamate dehydrogenase (GDH) activity in 8 species of marine phytoplankton have been carried out. The pH optima, linearity of reactions, apparent energies of activation, and apparent K _m values for NADPH, NH ₄ ^>+ and -ketoglutarate were determined. Based on these data, an accurate, sensitive enzyme assay procedure is presented which was successfully tested on shipboard during a recent cruise in an upwelling region. Preliminary studies on inhibition and activation of the NADP-linked GDH activity have also been carried out. In addition to NADP-linked GDH activity, NAD-linked GDH activity was discovered in certain species of phytoplankton. The possible physiological roles of NAD-and NADP-linked GDH enzymes are discussed.Contribution No. 911 from the Department of Oceanography, University of Washington. This research was supported by the National Science Foundation Grants GA-34165 and GX-33502.