Denitrification in a seashore sandy deposit influenced by groundwater discharge

The chemical compositions of ground water and organic matter in sediments were investigated at a sandy shore of Tokyo Bay, Japan to determine the fate of ground water NO₃ ^–. On the basis of Cl^– distribution in ground water, the beach was classified into freshwater (FR)-, transition (TR)-, and seawater (SW)-zones from the land toward the shoreline. The NO₃ ^– and N₂O did not behave conservatively with respect to Cl^– during subsurface mixing of freshwater and seawater, suggesting NO₃ ^– consumption and N₂O production in the TR-zone. Absence of beach vegetation indicated that NO₃ ^– assimilation by higher plants was not as important as NO₃ ^– sink. Low NH₄ ⁺ concentrations in ground water revealed little reduction of NO₃ ^– to NH₄ ⁺. These facts implied that microbial denitrification and assimilation were the likely sinks for ground water NO₃ ^–. The potential activity and number of denitrifiers in water-saturated sediment were highest in the low-chlorinity part of the TR-zone. The location of the highest potential denitrification activity (DN-zone) overlapped with that of the highest NO₃ ^– concentration. The C/N ratio and carbon isotope ratio (¹³C) of organic matter in sediment (< 100 -m) varied from 12.0 to 22.5 and from –22.5 to –25.5, respectively. The ¹³C value was inversely related to the C/N ratio (r ² = 0.968, n = 11), which was explained by the mixing of organic matters of terrestrial and marine origins. In the DN-zone, the fine sediments were rich in organic matters with high C/N ratios and low ¹³C values, implying that dissolved organic matters of terrestrial origin might have been immobilized under slightly saline conditions. A concurrent supply of NO₃ ^– and organic matter to the TR-zone by ground water discharge probably generates favorable conditions for denitrifiers. Ground water NO₃ ^– discharged to the beach is thus partially denitrified and fixed as microbial biomass before it enters the sea. Further studies are necessary to determine the relative contribution of these processes for NO₃ ^– removal.     

Water chemistry and periphyton in an alpine wetland

Remote high elevation sites are thought to be good sites to monitor global change and anthropogenic effects on ecosystems. This study was conducted during 1987–1990 in a high elevation wetland (3593 m) located in the Green Lakes Valley, Front Range, Colorado (USA). Salix spp. was the dominant riparian species in this 2 ha. wetland. Small shallow pools (<0.5 m depth) constituted a water area of 236 m³. The major source of water during the study period was snowmelt. The wetland had a well defined outlet and inlet, although an undetermined amount of water entered as groundwater from the snow patch above. Outlet discharge was 424–460 m³ during the month of July and declined thereafter as water input from the snowpatch declined. Inlet discharge was 67% of outlet discharge. Water temperatures in the outlet were always less than 6.8°C, pH 6.0–6.3, and mean conductivity 30.8 µS cm^–1. Both NO _inf3 ^sup– and SO _inf4 ^sup–2 were higher in the inlet thanin the outlet. Dominant cations in the inlet and outlet waters were Ca⁺² Mg⁺² > K⁺ + Na⁺; dominant anions were SO _inf4 ^sup–2 HCO _inf3 ^sup– > NO _inf3 ^sup– Cl^–. Nutrient limitation by P was demonstrated once using nutrient diffusing substrata. No limitation could be shown for NO _inf3 ^sup– , HCO _inf3 ^sup– , or Fe+EDTA. Slow colonization rates of periphyton on tiles were attributed to low temperatures and/or ultraviolet radiation. However, interannual differences in biomass on tiles were as much as 300% after 35 days. A minimum of 16–54 samples would be needed to detect a significant interannual change in biomass on tiles after 35 days assuming that the extreme case for periphyton patchiness. Global climate change is likely to affect discharge and water temperature in this wetland which hill have direct and indirect affects on population dynamics and ecosystem function.     

A new technique for continuous measurement of the heat of fermentation

Summary A special temperature control system has been developed and applied to continuous measuring of the heat evolved during a fermentation process. In this system, the fermentation broth was overcooled by a given constant cooling water flow. The excess heat removed from the fermentor was then made up by an immersion electrical heater. The action of the temperature controller was precisely monitored as it varied in response to the amount of heat produced by the microbial activities.The technique was used for determining the heat evolution byEscherichia coli grown on glucose. The ratio between quantities of total heat release and total oxygen consumption has been determined to be 0.556 MJ/mol O₂.The newly developed technique can be employed as an online sensor to monitor the microbial activities of either aerobic or anaerobic fermentation systems.Symbols C_c Heat capacity of cooling water (MJ/kg · °C) - C_p Heat capacity (MJ/kg · °C) - I Current of immersion heater (A) - K Constant in Equation (2) (h) - K Constant in Equation (13) (m³ · h · °C/MJ) - Q_c Flow rate of cooling water (m³/h) - Heat of agitation (MJ/m³ · h) - Heat dissipated by the bubbling gas (MJ/m³ · h) - Heat removal by the action of controller (MJ/m³ · h) - Heat of fermentation (MJ/m³ · h) - Heat loss to the surroundings (MJ/m³ · h) - Q_pass Constant average power dissipated by the immersion heater (MJ/m³ · h) - Fluctuating power dissipated by the immersion heater (MJ/m³ · h) - Power dissipated by the immersion heater (MJ/m³ · h) - T Temperature of fermentation broth (°C) - Constant average temperature of fermentation broth (°C) - Fluctuating temperature of fermentation broth (°C) - T_a Temperature of the ambient air (°C) - T_c Inlet temperature of cooling water (°C) - U₁A₁ Specific heat transfer coefficient for determination of heat loss to the surroundings (MJ/m³ · h · °C) - U₂A₂ Specific heat transfer coefficient for cooling surfaces (MJ/m³ · h · °C) - U₃A₃ Constant in Equation (16) (MJ/m³ · h · °C) - V Voltage of immersion heater (V) - V_L Liquid volume (m³) - OUR Oxygen uptake rate (mol O₂/m³ · h) Greek Letters H_fo The ratio between the total heat release and the total oxygen uptake (MJ/mol O₂) - _c Density of cooling water (kg/m³) - Time constant defined in Equation (6) (h) - _iM_iC_pi Heat capacity of system components (fermentation broth + fermentor jar + stainless steel) (MJ/m³ · °C)     

Coral growth in high-nutrient,low-pH seawater: a case study of corals cultured at the Waikiki Aquarium,Honolulu, Hawaii

Fifty-seven species of hermatypic corals have been maintained and grown in high-nutrient seawater at the Waikiki Aquarium, Honolulu, Hawaii. In this study we document the chemical conditions of aquarium water in terms of dissolved nutrients and carbon. Aquarium water is characterized by concentrations of inorganic nutrients that are high relative to most natural reef ecosystems: SiO₃ 200 M; PO₄ 0.6 M; NO₃ 5 M; NH₄ 2 M. In contrast, concentrations of organic nutrients are lower than most tropical surface ocean waters: DOP 0.1 M and DON 4 M. The incoming well-water servicing the facility has low pH, crating over-saturation of carbon dioxide. The coral communities in aquaria took up inorganic nutrients and released organic nutrients. Rates of nutrient uptake into aquaria coral communities were similar to nutrient uptake by natural reef communities. Coral growth rates were near the upper rates reported from the field, demonstrating corals can and do flourish in relatively high-nutrient water. The growth of corals does not appear to be inhibited at concentrations of nitrogen up to 5 M. Statements implying that corals can only grow in low nutrient oligotrophic seawater are therefore oversimplifications of processes that govern growth of these organisms. Some basic guidelines are given for maintenance of coral communities in aquaria.     

Physiological modelling of the response of Kocuria rosea exposed to changing water activity

Physiological effects of NaCl concentration (equivalent water activities, a_w, 1 to 0.87) were investigated with the moderately halophilic and piezotolerant bacterium, Kocuria rosea (formerly Micrococcus roseus), grown in bacteriological peptone/yeast extract broth. This bacterium, which was isolated from open shallow seawater, can grow in 150 g NaCl l^–1 (optimum NaCl concentration: 30 g l^–1, a_w=0.984) and under 207 MPa of hydrostatic pressure. The effects of water activity on _m can be quantitatively predicted, to a high level of accuracy by application of the Aiba/Edwards, and the Levenspiel-type unstructured inhibition-type kinetic models.     

Nickel sorption and speciation in a marine environment

Six sediment samples were collected from the northern Arabian Gulf. Nickel was added to each sediment- seawater suspension and the concentration of total dissolved Ni in the suspensions was monitored for 75 days. The analytical data were used to obtain a linear regression equation relating Ni²⁺ activity in the sediment suspensions to pH. Using this equation and thermodynamic information, the distribution of Ni species in the suspensions was calculated. The major inorganic species, extrapolated to 35 salinity and pH 8.1, were: Ni²⁺ (60.1%), NiCl⁺ (16.9%), NiCl _inf2 ^sup0 (5.0%), NiOH⁺ (0.4%), and NiSO _inf4 ^sup0 (17.5%). An increase in the seawater salinity increased the concentration of total dissolved Ni and Ni chloro-complexes. A decrease in pH of seawater increased total dissolved Ni and decreased NiOH⁺ complex, but the proportion of other species remained unchanged. There was no significant (P < 0.05) effect of Cu, Cd, Pb, Fe, Mn, and Al additions on Ni sorption in the marine sediment suspensions.     

Quantification of mussel (Mytilus edulis) growth from power station cooling waters in response to chlorination procedures

The age and growth history of individual mussels collected from the cooling water culverts of a power station were determined from the growth bands present in acetate peels of polished and etched shell sections. During periods of exposure to the antifouling agent, sodium hypochlorite (0.2mgl^‐1), shell growth was severely reduced, resulting in marked changes in the structure and deposition of the shell. As a consequence of chlorination, the growth rate of the mussel population occurring within the culverts was substantially lower and the mean length‐at‐age significantly smaller than that of a naturally occurring population immediately outside the cooling water intake. The growth patterns present in the shells of mussels experimentally added to the cooling waters during chlorination were compared with, and found to be similar to, the patterns in the shells of mussels that had settled naturally in the culverts. The daily growth of the experimentally exposed mussels (1.1–5.2 μm d^‐1) is two orders of magnitude lower than the growth rate of mussels growing in untreated waters. The use of mussels for evaluating the efficiency and long‐term effects of low level chlorination is discussed.     

Stable oxygen isotopes in<Emphasis Type="Italic"> Porites</Emphasis> corals monitor weekly temperature variations in the northern Gulf of Aqaba,Red Sea

In order to assess the ability of Porites corals to accurately record environmental variations, high-resolution (weekly/biweekly) coral ¹⁸O records were obtained from four coral colonies from the northern Gulf of Aqaba, which grew at depths of 7, 19, 29, and 42 m along one transect. Adjacent to each colony, hourly temperatures, biweekly salinities, and monthly ¹⁸O of seawater were continuously recorded over a period of 14 months (April 1999 to June 2000). Contrary to water temperature, which shows a regular and strong seasonal variation and change with depth, seawater ¹⁸O exhibits a weak seasonality and little change with depth. Positive correlations between seawater ¹⁸O and salinity were observed. The two parameters were related to each other by the equation ¹⁸O _Seawater (, VSMOW) = 0.281 × Salinity – 9.14. The high-resolution coral ¹⁸O records from this study show a regular pattern of seasonality and are able to capture fine details of the weekly average temperature records. They resolve more than 95% of the weekly average temperature range. On the other hand, attenuation and amplification of coral seasonal amplitudes were recorded in deep, slow-growing corals, which were not related to environmental effects (temperature and/or seawater ¹⁸O) or sampling resolution. We propose that these result from a combined effect of subannual variations in extension rate and variable rates of spine thickening of skeletal structures within the tissue layer. However, no smoothing or distortion of the isotopic signals was observed due to calcification within the tissue layer in shallow-water, fast-growing corals. The calculations from coral ¹⁸O calibrations against the in situ measurements show that temperature (T) is related to coral ¹⁸O ( _c ) and seawater ¹⁸O ( _w ) by the equation T (°C) = –5.38 ( _c – _w ) –1.08. Our results demonstrate that coral ¹⁸O from the northern Gulf of Aqaba is a reliable recorder of temperature variations, and that there is a minor contribution of seawater ¹⁸O to this proxy, which could be ignored.     

Enhanced oxygen transfer rates in fermentation using soybean oil-in-water dispersions

Summary The effect of soybean oil on the volumetric oxygen transfer coefficient during the cultivation ofAerobacter aerogenes cells is presented. For our aeration-agitation conditions (0.278 vvm and 500 rpm), it has been demonstrated that the use 19% (v/v) of soybean oil enabled a 1.85-fold increase of thek _l a coefficient (calculated on a per liter aqueous phase basis). For smaller volumetric oil fractions,k _L a increased linearly with the oil loading. Because of the oxygen-vector properties of soybean oil, this oil is able to significantly increase thek _L a of a bioreactor.Nomenclature C^*, C saturation and actual dissolved oxygen concentrations respectively (g/m³) - K_La volumetric oxygen transfer coefficient (h^–1) - K_La_initial k _La measured before the oil addition (h^–1) - M_O2 molar mass of oxygen (dalton) - N oxygen transfer rate (g/m³. h) - P_O2. P_N2 partial pressures ofO ₂ andN ₂ in the gas (atm) - P_H2OT partial pressure of water in air at the temperatureT (atm) - P_T total pressure (atm) - Q₀ volumetric flow rate of outlet air before seeding (m³/h) - Sp spreading coefficient (dynes/cm) - T absolute temperature of outlet gas (K) - V_i volume of the liquidi in the fermentor (m³) - V_M molar volume at 273 K and 1 atm (m³/mole) - _ij interfacial tension betweeni andj componants (dynes/cm) - _v volumetric fraction of the oil (v/v) - G gas - O oil - W water - i inlet - o outlet     

Impacts of chlorination and heat shocks on growth, pigments and photosynthesis of Phaeodactylum tricornutum (Bacillariophyceae)

The main impacts of cooling water from thermal (nuclear) power plants on aquatic organisms were caused by chlorination and temperature increase. In this study, we investigated the impacts of residual chlorine and short-term heat shocks on growth, pigment contents and photosynthesis of Phaeodactylum tricornutum. Growth of P. tricornutum was completely inhibited; Chlorophyll a and carotenoids contents deceased about 63.3% and 61.4% in 24 h treated with 0.2 mg L^− 1 chlorine. The negative effects of chlorination increased with enhanced concentration and prolonged exposure time. Relative electrode transfer rate (rETR) of P. tricornutum was significantly suppressed when treated with 0.2 mg L^− 1 residual chlorine for 24 h. Furthermore, the effective quantum yield (F_v'/F_m') decreased first but then recovered with prolonged exposure when residual chlorine ranged between 0.1 and 0.2 mg L^− 1. The cells were less sensitive to heat shocks compared with chlorination: the rETR and F_v'/F_m' was suppressed only when the temperature exceeded 35 °C for 1 h. When P. tricornutum was exposed to chlorination combined with heat shocks, the rETR was further inhibited at 35 °C. It indicated that both chlorination and heat shocks had negative impacts on the primary producers living in discharging coastal waters; furthermore, there were synergistic effects of heat shocks on chlorination toxicity.     

Spectroscopic and elemental investigation of microbial decomposition of aquatic fulvic acid in biological process of drinking water treatment

As humic substances left in treated water tend to form trihalomethans during chlorination, their removal in water treatment processes is a significant concern for drinking water supplies. One of the removal technologies, the biofilm reactor is studied for the microbial decomposition of aquatic fulvic acid (AFA). The AFA is characterized by elemental analysis, UV-Vis, ¹³C-NMR, and IR spectroscopic methods. The spectroscopic and elemental investigation was capable of characterizing the microbial decomposition of AFA. Biologically treated fulvic acid was in a more oxidized state; its spectra displayed a higher degree of condensation of aromatic constituents than influent fulvic acid. Microbial degradation of AFA was more active in the low molecular weight fractions and intensively occurred in the aliphatic fraction.Abbreviations A the absorbance at wavelength - specific absorptivities - AFAs aquatic fulvic acids - AHS aquatic humic substances - COD chemical oxygen demand - Da dalton - DO dissolved oxygen - E₄/E₆ratio a ratio between absorbance at 465 and 665 nm - FA fulvic acid - IR infrared - NMR nuclear magnetic resonance - TOC total organic carbon - UV-Vis ultraviolet-visible     

Fertilization acid release in Urechis eggs: I. The nature of the acid and the dependence of acid release and egg activation on external pH

The amount of fertilization acid produced by eggs of Urechis caupo, monitored by automatically back-titrating egg suspensions with base, depends linearly on the pH of the seawater. Above pH 7.0, at which no acid is released (Paul, M., Dev. Biol.43, 299–312, 1975), acid release increased approximately 0.34 pmole/egg/0.1 pH unit. Activation (germinal vesicle breakdown) depended on the amount of acid release in natural seawater; it did not occur if eggs released <1.5 pmole acid/egg. When fertilization acid is released into HCO^?₃-free seawater and the pH permitted to decrease, the supernatant can be tested for the presence of a volatile acid, such as CO₂, by bubbling with N₂ and comparing the increase in pH as volatile acid is driven off with experiments in which HCl or CO₂ is substituted for fertilization acid. An increase in pH of <0.2 pH units occurred on N₂ bubbling when fertilization acid or HCl was used to acidify HCO^?₃-free seawater compared to an increase of >0.5 pH units when CO₂ was used. Therefore, most, if not all, of Urechis fertilization acid is not volatile, and since Paul (1975) showed that it is not a nonvolatile weak acid, it must be H⁺.     

Oxygen transfer in a stirred loop fermentor with dilute polymer solutions

Oxygen transfer in a 0.35 m diameter stirred loop fermentor (a stirred tank with a concentric draft tube) has been studied with water containing a small amount of polymer(polyethylene oxide) as a drag-reducing additive.Power consumption was measured. It was found that the addition of polyethylene oxide causes an increase of power consumption. This is contrary to the results reported in the literature.Volumetric mass transfer coefficients (K _La) were measured. In water the introduction of the draft tube increased the K _La coefficient. The increase in K _La became larger with impeller speed. On the other hand, mass transfer in dilute polymer solutions decreased due to the presence of the draft tube. An empirical correlation has been proposed for the volumetric mass transfer coefficient in stirred loop fermentors. It has a general applicability.List of Symbols a 1/m specific surface area - C constant in Eq. (6) - g m/s² gravitational acceleration - K _L m/s overall liquid-phase mass transfer coefficient - n 1/s impeller speed - P W aerated power input by mechanical agitation - P _g W power input by sparged air - Q m³/min volumetric gas flow rate - U _sg m/s superficial gas velocity - V m³ liquid volume Greek Symbols exponents in Eq. (3) - exponent in Eq. (6) - kg/m³ density     

Growth ofEnteromorpha linza in sewage effluent and sewage effluent-seawater mixtures

Enteromorpha linza (L.) J. Ag. was grown in full strength sewage effluent, various combinations of sewage effluent and seawater, and in natural seawater. It was found that full strength sewage effluent with a salinity of 14 supported best growth of the alga. After a 12 day cultivation period, growth ofE. linza in full strength sewage effluent and 75% sewage effluent- seawater mixture showed 3.5-fold and 2-fold increase in fresh weight over that grown in natural seawater; respectively. Uptake of PO _inf4 ^sup3– -P, NH₃-N and NO _inf3 ^sup– -N by cells ofE. linza was extremely efficient in all tested media. Data obtained from the experiments indicated that inorganic nitrogen rather than phosphorus was the limiting nutrient factor for growth ofE. linza in full strength sewage effluent and in other sewage effluent- seawater mixtures. NH₃-N at concentrations above 4.5 ppm was found to inhibit uptake of NO _inf3 ^sup– -N in the same culture medium by the algal cells. The fact that sewage grownE. linza contained comparatively much higher protein content (30.2% dry weight) than that grown in natural seawater (12.5% dry weight) leads to the conclusion that sewage grownE. linza could serve as an economically feasible feed for livestock in Hong Kong where the sewage is characterized by having a salinity of approximately 14. It is proposed that this multicellular green alga is a suitable algal species to serve the dual function of wastewater purification through the production of algal protein from sewage effluent having high salinities.     

Planktonic chlorophyll a and eutrophication in two Mediterranean littoral systems (Mallorca Island,Spain)

Two Mediterranean littoral systems of Mallorca Island have been studied using planktonic chlorophyll a (total concentration and seasonal variations) as trophic indicator. The studied systems are quite different in geomorphology, physicochemical trends and anthropic incidence. S'Albufera-Alcudia Bay is the drainage outlet of a coastal marsh, with a salt wedge estuarine regime. Andratx Harbour is a narrow bay affected by a high anthropic incidence due to the presence of a small fishing port and mainly a large leisure harbour. Both systems are affected by a typical Mediterranean climate and a negligible tide incidence. The present work is based on several year monitoring of physical, chemical and biological water parameters. In S'Albufera-Alcudia Bay, Chl a concentration ranged from 0.01 to 17.10 mg m^–3, the values dropping from the inland site to the sea. The phytoplankton biomass gradient takes its origin in physical and chemical differences. The variance is mainly related to the inland-sea water axis. Nitrogen and silica enriched inland waters are the main source of eutrophication, hence their relation with Chl a. These nutrients entering the Albufera are mainly derived from leaching from farmed soils. The transition from an inland eutrophic system to an oligotrophic marine one show the filter character of these coastal marshes. In Andratx Harbour, Chl a ranged from a non detectable concentration to 6.36 mg m^–3. The ultraplankton (<5 m) was the most important contributor to total concentration. The ultraplankton in this system is related to influence of more oligotrophic open seawater. A greater proportion of microplankton (>20 m) is related both to higher nutrient concentrations and a higher water column stability. In Andratx Harbour, the enclosure state seems very important for development of phytoplankton blooms.     

Growth,N2 fixation and photosynthesis in a cyanobacterium,Trichodesmium sp., under Fe stress

Trichodesmium sp., isolated from the Great Barrier Reef lagoon, was cultured in artificial seawater media containing a range of Fe concentration. Fe additions stimulated growth, N₂ fixation, cellular chlorophyll a content, light-saturated chlorophyll a-specific gross photosynthetic capacity (P_m ^chla) and the dark respiration rate (R_d ^chla). Cell yields only doubled for 9 nM Fe relative to zero added Fe, whereas N₂ fixation increased 11-fold considerably for 450 nM Fe. The results suggest that N₂ fixation of Trichodesmium is more sensitive to Fe limitation than are the cell yields.     

Heat transfer in vertical perl mills

A model of heat transfer during grinding in vertical multi-disk perl mills has been proposed. Heat transfer intensity in such mills depends on thermal resistance in a boundary layer formed at the inner surface of mill tank wall. The layer thickness changes depending on process variables. Results obtained are presented in the form of a dimensionless correlation equation.List of Symbols C ball filling of the mill, - c _pw specific heat of cooling water, kJ/(kg K) - d disk diameter, m - d _k ball diameter, m - D inner diameter of the mill tank, m - G _w mass flow rate of cooling water, kg/s - h distance between impeller disks, m - n revolutions frequency of the impeller shaft, s^–1 - q heat flux density, kW/m² - Q _c total heat energy emitted in the mill, W - T temperature, K - T _w1 temperature of cooling water at the cooling jacket inlet, K - T _w2 cooling water temperature at the outlet, K - T _m average temperature inside the mill, K - T _s average temperature of the tank wall, K - u peripheral speed of the impeller disk, m/s - heat transfer coefficient, kW/(m²K) - boundary layer thickness, m - porosity of the lying bed, - _m porosity of the suspended bed, - _c liquid dynamic viscosity, Pa s - _cs liquid dynamic viscosity at wall temperature, Pa s - _c thermal conductivity coefficient of liquid, W/(mK) - _c liquid density, kg/m³ - _s solid density, kg/m³ Dimensionless Numbers Reynolds number for mixing process - Reynolds number for liquid parameters - Nusselt number for liquid parameters - Prandtl number for liquid parameters - modified Euler number     

Noradrenalin antagonizes effects of serotonin and acetylcholine in the seawater eel intestine

After inhibiting ion and water transport with 10^-6 mol·l^-1 serotonin and 10^-6 mol·l^-1 methacholine, a muscarinic agonist of acetylcholine, 10^-5 mol·l^-1 (±)noradrenaline restored the serosa-negative transepithelial potential difference and short-circuit current in a step-like manner, accompanied by an increase in water absorption across the seawater eel intestine. Such recovery by noradrenalin was not obtained after pretreatment with 10^-7 mol·l^-1 eel atrial natriuretic peptide. This means that the inhibitory mechanisms of serotonin and acetylcholine are different from those of atrial natriuretic peptide. Similarly, 10^-7 mol·l^-1 clonidine and guanabenz (₂-agonists) also reversed the inhibitory action of serotonin and methacholine, but 10^-7 mol·l^-1 phenylephrine (₁-agonists) and 10^-7 mol·l^-1 isoproterenol (-agonist) did not antagonize serotonin and methacholine actions. Further, the enhancement by 10^-5 mol·l^-1 noradrenalin was blocked by 10^-4 mol·l^-1 yohimbine (₂-agonists) and 10^-4 mol·l^-1 prazosin (₁-agonists), but not by 10^-4 mol·l^-1 propranolol (-antagonist). Although relatively high dosage is required to obtain a significant effect, and discrimination between ₁- and ₂- is not successful in the present study, these results suggest that noradrenalin acts on an -type receptor. The -type receptor may exist on the enterocytes, since the effects of noradrenalin are observed even in the presence of 10^-6 mol·l^-1 tetrodotoxin. Interestingly, the tissue resistance also increased in parallel with increase in the short-circuit current after treatment with noradrenalin in the posterior part of the seawater eel intestine.Abbreviations ACh acetylcholine - 5-HT serotonin - eANP eel atrial natriuretic peptide - I _sc short-circuit current - MCh methacholine - NA noradrenalin - PD transepithelial potential difference - R _t tissue resistance - TTX tetrodotoxin - VIP vasoactive intestinal peptide     

Na+/H+ exchange in the kidneys of eels (Anguilla anguilla) adapted to sea water or to freshwater environments: Studies with brush border membrane vesicles

• 1.1. In brush border membrane vesicles isolated from eel kidneys, adapted either to sea water or freshwater environments, a Na⁺/H⁺ antiporter is present.
• 2.2. Using a calibration plot it is possible to evaluate the amount of protons that this antiporter can accumulate inside the vesicular space.
• 3.3. The activity of the antiporter seems to be affected by the salinity of the water; it is higher in animals adapted to seawater.
• 4.4. This adaptation seems to occur by a J_max regulation of the antiporter.

     

Exogenous inorganic carbon sources for photosynthesis in seawater by members of the Fucales and the Laminariales (Phaeophyta): ecological and taxonomic implications

Summary Characteristics of inorganic carbon assimilation by photosynthesis in seawater were investigated in six species of the Fucales (five Fucaceae, one Cystoseiraceae) and four species of the Laminariales (three Laminariaceae, one Alariaceae) from Arbroath, Scotland. All of the algae tested could photosynthesise faster at high external pH values than the uncatalysed conversion of HCO ₃ ^- to CO₂ can occur, i.e. can use external HCO ₃ ^- . They all had detectable extracellular carbonic anhydrase activity, suggesting that HCO ₃ ^- use could involve catalysis of external CO₂ production, a view supported to some extent by experiments with an inhibitor of carbonic anhydrase. All of the algae tested had CO₂ compensation concentrations at pH 8 which were lower than would be expected from diffusive entry of CO₂ supplying RUBISCO as the initial carboxylase, consistent with the operation of energized entry of HCO ₃ ^- and / or CO₂ acting as a CO₂ concentrating mechanism. Quantitative differences among the algae examined were noted with respect to characteristics of inorganic C assimilation. The most obvious distinction was between the eulittoral Fucaceae, which are emersed for part of, or most of, the tidal cycle, and the other three families (Cystoseiraceae, Laminariaceae, Alariaceae) whose representatives are essentially continually submersed. The Fucaceae examined are able to photosynthesise at high pH values, and have lower CO₂ compensation concentrations, and lower K_1/2 values for inorganic C use in photosynthesis, at pH 8, than the other algae tested. Furthermore, the Fucaceae are essentially saturated with inorganic C for photosynthesis at the normal seawater concentration at pH 8 and 10°C. These characteristics are consistent with the dominant role of a CO₂ concentrating mechanism in CO₂ acquisition by these plants. Other species tested have characteristcs which suggest a less effective HCO ₃ ^- use and CO₂ concentrating mechanism, with the Laminariaceae being the least effective; unlike the Fucaceae, photosynthesis by these algae is not saturated with inorganic C in normal seawater. Taxonomic and ecological implications of these results are considered in relation to related data in the literature.