Primary production and heterotrophy of a pennate and a centric salt marsh diatom

Radionuclide labeled sodium bicarbonate and glucose were used to measure the rates of primary production and glucose uptake by Nitzschia obtusa var. undulata and Cymbella pusilla. The presence of glucose in the medium enhanced primary production in both diatom species. Uptake of glucose in C. pusilla was photoinhibited. A maximum of 9.3 nmol C mg dry wt^-1 h^-1 of glucose was taken up in the light without the presence of NaHCO₃ in the medium and with NaHCO₃ present the value was 18 nmol C mg dry wt^-1 h^-1. The ratio of inorganic carbon fixed to the total carbon budget (autotrophy and heterotrophy) was 0.51 for N. obtusa var. undulata and 0.62 for C. pusilla.     

Microbial control of organic carbon in marine sediments: Coupled chemoautotrophy and heterotrophy

The chemoautotrophic fixation of carbon dioxide is responsible for an appreciable component of the organic matter apparent as a carbon-rick peak at 40 cm sub-bottom in the marine muds of Halifax Harbour, Nova Scotia, Canada. Dissolved oxygen and sulfide profiles show that the 40 cm horizon represents a transitional environment from aerobic to underlying anaerobic conditions. A dissolved sulfate maximum and pH minimum at 40 cm indicate that sulfur-oxidizing chemoautotrophs are associated with the organic carbon production at this horizon. The stimulation of CO₂-fixation by thiosulfate and inhibition by anaerobic conditions, ammonia, nitrate and nitrite further support the contention that sulfur-oxidizers are primary producers at this horizon. Heterotrophic activity data show that both aerobic and anaerobic heterotrophs are active in the sediments. These data, in conjunction with the measurement of CO₂-fixation and the calculation of organic carbon accumulation over time, show that the peak of organic carbon observed is residual carbon that is not heterotrophically recycled to CO₂ at the 40 cm horizon.     

Deoxyribonuclease activity in seawater and sediment

This paper describes a fluorometric method for assaying deoxyribonuclease (DNase) activity in natural seawater and sediment. DNase activity was detected in a sea-water sample taken from Tokyo Bay (Japan), and in various sediment samples taken from Suruga, Sagami and Tokyo Bays, and from Aburatsubo Inlet. Much more DNase occurred in seawater in a state bound to suspended particles or microbial cells than dissolved free in seawater. Although viable DNA-hydrolyzing bacteria were found to be widely distributed in seawater and sediment, poor correlation existed between the bacterial population and the intensity of DNase activity in the sediments examined. In addition, intensities of DNase activity in various surface sediments had no apparent correlation with the DNA contents and the sediment types. However, a close correspondence was found between the vertical variation of DNase activities and the gradient of DNA contents and of Eh in the core sediment at Aburatsubo Inlet.     

Comparison of methods for the analysis of dissolved urea in seawater

A comparison between the diacetyl monoxime and urease methods for measuring dissolved concentrations of urea in seawater was conducted in artificial seawater, phytoplankton-culture filtrate and both natural and ureaspiked field samples from coastal and oceanic enviroments during 1984. The urease technique underestimated urea concentrations in unbuffered photoplankton-culture filtrate as a result of the inhibition of the urease enzyme, causing the incomplete hydrolysis of urea in these samples. Factors responsible for inhibiting urease included pH, seawater ions, and possibly extracellular metabolites produced in unialgal cultures. Seawater type and time of sample collection were important variables affecting urea measurement by the urease method, and recovery of internal standards ranged from 40 to 100%. Increasing the heating time of the urease assay, or the concentration of urease added to the seawater samples increased the amount of urea determined by the urease method. However, measured values were still less than the concentration of the urea internal standards. The diacetyl monoxime method was suitable for urea determinations in all the seawater samples we examined; it was easily automated, and the results were accurate and reproducible. This modified technique is recommended for measuring disolved concentrations of urea in seawater.     

The trophic role of glycolic acid in coastal seawater. I. Heterotrophic metabolism in seawater and bacterial cultures

Glycolic acid, a known algal excretory product, represents a potentially important energy source for heterotrophic bacteria in marine waters. Measurements of heterotrophic uptake and mineralization by the natural microbes in the plankton indicate quantitative use of glycolic acid comparable to other common microbial substrates. This activity shows vertical and horizontal variations that correlate in a general way with primary productivity. Glycolic acid appears to be present at higher concentrations than other low molecular weight substrates, and it also shows a lower rate of turnover. It is mineralized (respired) to a greater extent than other recorded substrates, an average of 70% of total uptake. Two-thirds of a total of 141 colonies of bacteria cultured from seawater on marine agar proved capable oftaking up and respiring glycolic acid. These same bacteria, however, were unable to utilize glycolic acid for growth when it was the sole carbon source. Glycolate may therefore occur at higher concentrations and show erratic fluctuations in natural waters because microbial use is not tied to glycolate production but to the presence of other substrates. The fact that so many bacteria are able to metabolize it indicates a possibly important trophic role as an energy source. It is suggested that glycolic acid may be a major source of energy for active transport of other substrates by marine bacteria.     

Rate of dissolution of diatom silica walls in seawater

The solubility and dissolution rate of silica were investigated using cell walls prepared from two species of diatoms, Thalassiosira decipiens and Rhizosolenia hebetata forma semispina. The solubility (C _e) as a function of temperature (T, °C) can be described by the following equation: C _e (SiO₂ mg l^-1)=67.8+1.48 T. The first-order reaction equation without the surface-area term was considered to be reasonable in estimating the dissolution rate of biogenic silica in the ocean system. The rate of dissolution differed not only from one species to another but also from one portion to another portion of the same wall. The rate constants of dissolution in the ocean system were estimated to range in the order of from 10^-1 to 10^-9 per hour.     

Identification of marine bacteria affecting lithium adsorbents in seawater

Lithium manganese oxide–based adsorbents have been developed for the recovery of lithium from seawater. To maximize the recovery efficiency, it is important to prevent microfouling of lithium adsorbents by marine bacteria. To identify the marine bacteria that cause biofouling against the lithium adsorbents, lithium adsorbents were installed into a non-coated frame or a frame coated with an antifouling agent soaked in seawater. Microorganisms from the surface of lithium adsorbents were collected for 30 days at 10-day intervals, cultured in marine broth, isolated, and identified by 16S rDNA sequencing. Pseudoalteromonas and Vibrio were constituted to 35.6 and 28.8 % of total isolates, respectively, and were predominant in the non-coated frame, whereas Vibrio was poorly isolated (2.3 %) from the antifouling agent–coated frame. In this study, antifouling strategy for maximum lithium recovery efficiency in the marine area takes account of Pseudoalteromonas and Vibrio.     

A rapid,highly sensitive technique for the determination of ammonia in seawater

A reliable and sensitive technique for the rapid determination of ammonia in seawater is described. The procedure is based on the conversion of NH ₄ ⁺ in seawater to NH₃ and the subsequent diffusion of NH₃ across a hydrophobic membrane using flow-injection analysis. Sixty determinations can be made per hour on a flowing stream of seawater or discrete samples. The lower limit of detection is 0.05 M. Results of two applications that demonstrate the potential of this technique are presented, a laboratory excretion experiment employing the crabPachygrapsus crassipes, and small-scale vertical mapping of ammonia in the ocean.     

Relationship between cadmium concentrations in seawater and those in the mussel Mytilus edulis

Various forms of regression analysis are presented which show that there is a significant equilibrium relationship between total recoverable cadmium in seawater and its concentration in the mussel Mytilus edulis (P<0.001). The calculations show that the concentration of cadmium in seawater should not exceed 0.20 g l^-1 if the mussel is not to reach a cadmium concentration of 2 mg kg^-1 wet weight: a value frequently used as a food standard for human consumption. Further, when a cadmium value of 2 mg kg^-1 wet weight is reached, the concentration factor by mussels for cadmium from seawater is 9 950.     

Scanning electron microscopy of dialysis tubes incubated in flowing seawater

Scanning electron micrographs (SEM) demonstrate the growth of an epiphytic diatom and bacterial community on the surface of dialysis membranes incubated In situ, Narragansett Bay, Rhode Island (USA). A comparison is made between brushed and unbrushed tubes in summer, and unbrushed tubes in winter. Detrital deposition and epiphytic growth may decrease surface area and, by uptake and regeneration, influence nutrient flux through the membrane.     

Microbial clumps in seawater in the euphotic zone of Saanich Inlet (British Columbia)

Viable heterotrophic microorganisms were enumerated to be 3.7±7.3 bacterial cells per microbial clump during summer in the euphotic zone of Saanich Inlet, British Columbia, Canada. Large microbial aggregates were observed, especially after the phytoplankton bloom, when the phytoplankton biomass formed about 1/2 the total suspended organic matter in the sea. The cell number per microbial clump was minimal when the phytoplankton fraction in the total suspended organic matter was almost 0 (i.e., before the phytoplankton bloom), and again when the phytoplankton bloom occurred. The size of the microbial clumps is discussed, particularly in reference to the food chain in the sea.The work was carried out at the Fisheries Research Board of Canada, Biological Station, Nanaimo, during the tenure of a National Research Council Post-doctoral fellowship.     

Rare earth elements distribution in seawater and suspended particulate of the Central Mediterranean Sea

Rare earth element (REE) content in suspended and dissolved phases from the Strait of Sicily (Central Mediterranean Sea) has been measured. Vertical profiles of several dissolved REEs along the water column reflect the 3-D oceanographic features of the studied area and identifies the different water masses present there. Shale-normalized REE distribution patterns and derived parameters calculated for the suspended particulate show different atmospheric dust-surface inputs and their interactions with seawater. Finally, combined information from [La/Yb]_N, ratios, REE/La ratios and Eu anomalies measured in the suspended particulate suggest an important contribution of volcanic materials from the Etna volcano and Saharan dust to the lithogenic fraction of the suspended particulate.     

Rare earth elements distribution in seawater and suspended particulate of the Central Mediterranean Sea

Rare earth element (REE) content in suspended and dissolved phases from the Strait of Sicily (Central Mediterranean Sea) has been measured. Vertical profiles of several dissolved REEs along the water column reflect the 3-D oceanographic features of the studied area and identifies the different water masses present there. Shale-normalized REE distribution patterns and derived parameters calculated for the suspended particulate show different atmospheric dust-surface inputs and their interactions with seawater. Finally, combined information from [La/Yb]_N, ratios, REE/La ratios and Eu anomalies measured in the suspended particulate suggest an important contribution of volcanic materials from the Etna volcano and Saharan dust to the lithogenic fraction of the suspended particulate.     

Effect of temperature on seawater desalination-water quality analyses for desalinated seawater for its use as drinking and irrigation water

The effect of feed seawater temperature on the quality of product water in a reverse osmosis process was investigated using typical seawater at Urla Bay, Izmir region, Turkey. The tests were carried out at different feed seawater temperatures (11–23°C) using two RO modules with one membrane element each. A number of variables, including pH, conductivity, total dissolved solids, salinity, rejection percentage of a number of ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃ ⁻, and SO₄ ²⁻), and the levels of boron and turbidities in collected permeates, were measured. The suitability of these permeates as irrigation and drinking water was checked by comparison with water quality standards.     

流沙湾海水中石油烃的时空分布特征研究

于2008年2月（冬季）、5月（春季）、8月（夏季）和11月（秋季）对流沙湾进行了4次采样考察,研究分析了流沙湾表层海水中石油烃质量浓度的平面分布和季节变化特征。结果表明,在2008年度,流沙湾表层海水石油烃的质量浓度为0~1.930 mg.L-1,平均值为0.080 mg.L-1,季节差异比较明显,呈春、冬、夏、秋季依次减小的变化趋势,冬、春季节海水呈现不同程度石油污染,夏、秋季节属Ⅰ、Ⅱ级水质,整个流沙湾海域表层海水石油烃的平面分布相对比较均匀。在内外湾分布上,冬、春、秋季节外湾大于内湾,而夏季节内湾大于外湾。流沙湾的水产养殖活动是其海水石油烃时空分布的主要影响因素。     

Bisphenol A and metabolites released by biodegradation of polycarbonate in seawater

This is the first report of bisphenol A release from polycarbonate during biodegradation by marine microorganisms. Bisphenol A is a monomer in polycarbonate and an endocrine disruptor toxic for marine organisms. Biodegradation of polycarbonate is poorly documented. Here, we have tested the possible release of bisphenol A and metabolites during biodegradation of polycarbonate by marine microorganisms. Polycarbonate degradation was carried out in vitro using a mixed marine microbial consortium isolated from the Bay of Bengal, India, 1 year under controlled laboratory conditions. The degradation was monitored by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography—mass spectrometry (GC–MS). The organic soluble metabolites were analyzed by high-performance liquid chromatography (HPLC). We found that bisphenol A was released. The amount of bisphenol A released during 1 year is higher than the half-maximal effective concentration (EC₅₀) values reported for marine organisms. We also identified the following bisphenol A metabolites: 4-hydroxyacetophenone, 4-hydroxybenzaldehyde, and 4-hydroxybenzoic acid. Polycarbonate biodegradation was evidenced by gravimetric weight loss and Fourier transform infrared spectroscopy. The reduction of methyl and carbonyl indices suggests oxidation and hydrolysis of the polymer, respectively. 2D NMR showed an aromatic C–C cleavage.     

Ecotypic differentiation of Laminaria longicruris in relation to seawater nitrate concentration

The ultraplankton (cell diameters >3 μm), which compromises about 70% of the biomass of phytoplankton in subtropical surface waters near Oahu, Hawaii, was isolated for growth rate studies. The specific growth rate (μ) was estimated from the rate of increase of the chlorophyll biomass during incubations in the absence of grazers. This growth rate of the ultraplankton ranged from 0.037 to 0.071 h^?1 (=1.3 to 2.5 doublings d^?1) during a period when P:B ratios of 5 to 14.5 μg C μg^?1 chl a h^?1 prevailed. The co-occurrence of atypically high P:B ratios and nonlimiting ambient nutrient concentrations suggests that the calculated values are higher than those characteristic of such subtropical ecosystems in general. Rates of ammonium uptake and photosynthesis by the >3 μm fraction were also compared to those of larger fractions. Organisms in the >3 μm fraction assimilated NH ₄ ⁺ at a rate which was about 75% greater than that of the 3 to 20 μm size fraction. Comparison of μ and P:B data collected over a 2 mo period (November–December, 1980) shows that the correlation between these two rate indices is nonlinear. The predominance of small-celled phytoplankton in oligotrophic waters is explained, in part, by its higher μ, its higher nutrient assimilation rates, and the absence of its loss through sedimentation.     

Further studies on decomposition of dissolved organic matter in coastal seawater

Experiments were made on decomposition of dissolved organic matter (DOM) in coastal seawater (Sagami Bay and Tokyo Bay, Japan). Decomposition of DOM seems to proceed in two steps: a rapid decrease in DOM during the first several days, followed by a slow decrease after this time. The apparent rate constant for decomposition of the total DOM was calculated as 0.01 to 0.09 day^-1 for the first step and 0.001 to 0.009 day^-1 for the second step, assuming that such decomposition proceeds as a first-order reaction. A part of such utilizable fractions of DOM may be derived from excretion and decomposition products of phytoplankton, especially “red-tide” organisms occurring in summer. Molecular weight distribution of DOM changed with advancing decomposition. The low-molecular-weight DOM (mainly less than 500) in the surface water of Tokyo Bay was 0.67 mgC/l (24% of the total DOM) at the initiation of incubation; this decreased to 0.36 mgC/l (16% of the total DOM) after 2 days incubation at 20°C in the dark. Low-molecular-weight DOM was thought to be firstly utilized by micro-organisms. After 6 to 10 months incubation, the proportion of low-molecular-weight DOM decreased and that of high-molecular-weight DOM increased.     

A new application of the diacetyl monoxime method to the automated determination of dissolved urea in seawater

A new application of the diacetyl monoxime method for the determination of dissolved urea in seawater is presented, based on the Alpkem autoanalyzer (OI, Analytical). This system has several advantages over automated methods previously described in the literature. The urea cartridge can be easily built using nut/ferrule connections, and the external thermostatic bath is not required. The system is set up to operate at low urea concentrations (0–3 µM urea), but it is linear up to 100 µM urea. The sample volume needed for analysis is 0.4 ml, and the rate of analysis is 25 samples h^–1. The precision of analysis (CV) of seawater samples is 2.1% at 0.50 µM urea, and the detection limit is 0.02 µM urea. The interference on the colorimetric measurement due to formation of Brij-35 aggregate in strongly acidic media was eliminated by substituting this wetting agent with hexadecyl–trimethyl–ammonium bromide; thus, this method is suitable for other autoanalyzer technologies that use small-diameter transmission tubes and small-sized spectrophotometric flowcells.Communicated by R. Cattaneo-Vietti, Genova