The effects on human health and hydrogeochemical characteristics of the Kirkgeçit and Ozancik Hot Springs,Canakkale, Turkey

This investigation was carried out to determine the hydrogeochemical characteristics of the Kirkgeçit and Ozancik hot springs. The study areas are located northeast and southwest of the town of Çan, Çanakkale. During the investigation, geological maps of the hot springs and its surroundings were prepared, and hot waters and rock samples were collected from the study sites. The Paleogene–Neogene aged andesite, trachyandesite, andesitic tuff, silicified tuff and tuffites form the basement rocks in the Ozancik hot spring area. In the Kirkgeçit hot spring area, there are Lower Triassic aged mica and quartz schists at the basement rocks. The unit is covered by limestones and marbles of the same age. They are overlain by Quaternary alluvial deposits. A chemical analysis of the Kirkgeçit hot water indicates that it is rich in SO₄ ^2– (1200.2 mg L^–1), Cl^– (121.7 mg L^–1), HCO₃ ^– (32.5 mg L^–1), Na⁺ (494 mg L^–1), K⁺ (30.2 mg L^–1), Ca²⁺ (102 mg L^–1), Mg²⁺ (15.2 mg L^–1), and SiO₂ (65.22 mg L^–1). Chemical analysis of the Ozancik hot water indicates that it is rich in SO₄ ^2– (575 mg L^–1), Cl^– (193.2 mg L^–1), HCO₃ ^– (98.5 mg L^–1), Na⁺ (315 mg L^–1), K⁺(7.248 mg L^–1), Ca²⁺ (103 mg L^–1), Mg²⁺ (0.274 mg L^–1), and SiO₂(43.20 mg L^–1). The distribution of ions in the hot waters on the Schoeller diagram has an arrangement of r(Na⁺+K⁺)>rCa²⁺>rMg²⁺ and r(SO₄ ^2–)>rCl^–>r(HCO₃ ^–). In addition, the inclusion of Fe²⁺, Cu²⁺, Cr³⁺, Mn²⁺, Ni²⁺ and Hg²⁺ in the hot water samples indicates potential natural inorganic contamination. The water analysis carried out following the ICPMS-200 technique was evaluated according to the World Health Organisation and Turkish Standards. The use and the effects of the hot water on human health are also discussed in the paper.     

Physiological role of branchial carbonic anhydrase in the shore crabCarcinus maenas

Excretion of total CO₂ and uptake of sodium and chloride ions across the branchial epithelium of the posterior gills of the shore crabCarcinus maenas, collected from Kiel Bay (Baltic Sea) in 1989, were measured using isolated perfused gill preparations. Total CO₂ effluxes depended on the HCO ₃ ^- concentration of the internal perfusate in a saturable mode and were inhibited by internally and externally applied acetazolamide at 10^–4 M. Potential differences between hemolymph space and medium did not change significantly during experimental treatments. Neither a bicarbonate gradient (6 mM) directed from the internal perfusate to external bath solution nor symmetrically applied 10^–4 M acetazolamide significantly influenced the influxes of Na⁺ and Cl^–. Results confirmed the role of carbonic anhydrase in CO₂ excretion but called into question the assumed functioning of the enzyme in branchial ion transport processes.     

Extra- and intracellular acid-base balance and ionic regulation in cod (Gadus morhua ) during combined and isolated exposures to hypercapnia and copper

Cod (Gadus morhua) were exposed to hypercapnia (water Pco₂ = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO₃ ⁻]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na⁺] and [Cl⁻] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na⁺] and [Cl⁻] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances. The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia. Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma were significantly elevated only after 48 h, with liver showing the largest elevation. Received: 15 November 1996 / Accepted: 2 December 1996     

Degradation of Benzo[a]Pyrene in Soil with Arbuscular Mycorrhizal Alfalfa

Mycorrhizal and non-mycorrhizal alfalfa (Medicago sativa) was grown in pots containing soil artificially contaminated with various levels of benzo[a]pyrene (B[a]P)(0, 1, 10 and 100 mg kg^–1). Soil and plants were sampled after 30, 40, 50, 60 and 90 days and compared with unlanted pots. The percentage of mycorrhizal root length colonized by Glomus caledoniun was not significantly affected by the addition of B[a]P up to 10 mg kg^–1 but was significantly lower at 100 mg kg^–1B[a]P compared with low concentrations (p < 0.05). There was no difference in soil polyphenol oxidase and dehydrogenase activity among the controls and applications of 1 and 10 mg kg^–1 of B[a]P. However, enzyme activities were significantly higher at 100 mg kg^–1B[a]P compared with the other three treatments, and there was no mycorrhizal effect. Over a period of 90 days the concentration of B[a]P in soil in which alfalfa was grown was significantly lower than in unplanted soil (p < 0.05). Degradation rates of B[a]P added at 1, 10 and 100 mg kg^–1 without G. caledonium were 76, 78 and 53%, and with mycorrhizal inoculation were 86, 87 and 57%. The degradation rate in unplanted soil was significantly lower than in planted soil, and was significantly higher in medium- and low-B[a]P treatments than in the high B[a]P concentration tested. There is a possibility of enhancement phytoremediation of PAHs in rhizosphere soil with arbuscular mycorrhizal fungi.     

Cuttlebone calcification increases during exposure to elevated seawater pCO2 in the cephalopod Sepia officinalis

Changes in seawater carbonate chemistry that accompany ongoing ocean acidification have been found to affect calcification processes in many marine invertebrates. In contrast to the response of most invertebrates, calcification rates increase in the cephalopod Sepia officinalis during long-term exposure to elevated seawater pCO₂. The present trial investigated structural changes in the cuttlebones of S. officinalis calcified during 6 weeks of exposure to 615 Pa CO₂. Cuttlebone mass increased sevenfold over the course of the growth trail, reaching a mean value of 0.71 ± 0.15 g. Depending on cuttlefish size (mantle lengths 44–56 mm), cuttlebones of CO₂-incubated individuals accreted 22–55% more CaCO₃ compared to controls at 64 Pa CO₂. However, the height of the CO₂-exposed cuttlebones was reduced. A decrease in spacing of the cuttlebone lamellae, from 384 ± 26 to 195 ± 38 μm, accounted for the height reduction The greater CaCO₃ content of the CO₂-incubated cuttlebones can be attributed to an increase in thickness of the lamellar and pillar walls. Particularly, pillar thickness increased from 2.6 ± 0.6 to 4.9 ± 2.2 μm. Interestingly, the incorporation of non-acid-soluble organic matrix (chitin) in the cuttlebones of CO₂-exposed individuals was reduced by 30% on average. The apparent robustness of calcification processes in S. officinalis, and other powerful ion regulators such as decapod cructaceans, during exposure to elevated pCO₂ is predicated to be closely connected to the increased extracellular [HCO₃ ⁻] maintained by these organisms to compensate extracellular pH. The potential negative impact of increased calcification in the cuttlebone of S. officinalis is discussed with regard to its function as a lightweight and highly porous buoyancy regulation device. Further studies working with lower seawater pCO₂ values are necessary to evaluate if the observed phenomenon is of ecological relevance.     

Maintenance of coelomic fluid pH in sea urchins exposed to elevated CO2: the role of body cavity epithelia and stereom dissolution

Experimental ocean acidification leads to a shift in resource allocation and to an increased [HCO₃ ^?] within the perivisceral coelomic fluid (PCF) in the Baltic green sea urchin Strongylocentrotus droebachiensis. We investigated putative mechanisms of this pH compensation reaction by evaluating epithelial barrier function and the magnitude of skeleton (stereom) dissolution. In addition, we measured ossicle growth and skeletal stability. Ussing chamber measurements revealed that the intestine formed a barrier for HCO₃ ^? and was selective for cation diffusion. In contrast, the peritoneal epithelium was leaky and only formed a barrier for macromolecules. The ossicles of 6 week high CO₂-acclimatised sea urchins revealed minor carbonate dissolution, reduced growth but unchanged stability. On the other hand, spines dissolved more severely and were more fragile following acclimatisation to high CO₂. Our results indicate that epithelia lining the PCF space contribute to its acid–base regulation. The intestine prevents HCO₃ ^? diffusion and thus buffer leakage. In contrast, the leaky peritoneal epithelium allows buffer generation via carbonate dissolution from the surrounding skeletal ossicles. Long-term extracellular acid–base balance must be mediated by active processes, as sea urchins can maintain relatively high extracellular [HCO₃ ^?]. The intestinal epithelia are good candidate tissues for this active net import of HCO₃ ^? into the PCF. Spines appear to be more vulnerable to ocean acidification which might significantly impact resistance to predation pressure and thus influence fitness of this keystone species.     

Geochemistry and quality of groundwater of the Yarmouk basin aquifer,north Jordan

Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca²⁺ + Mg²⁺ versus HCO₃^? + CO₃^2?, Ca²⁺ + Mg²⁺ versus total cations, Na⁺ + K⁺ versus total cations, Cl^? + SO₄^2? versus Na⁺ + K⁺, Na⁺ versus Cl^?, Na⁺ versus HCO₃^? + CO₃^2?, Na⁺ versus Ca²⁺, and Na⁺: Cl^? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, CO₃^2?, SO₄^2?, and F^? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na⁺ and Cl^? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg²⁺, Na⁺, Cl^?, SO₄^2?, and NO₃^? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO₃^? + CO₃^2? > Cl^? > SO₄^2? > NO₃^? > F^? and Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg²⁺, Na⁺, and NO₃^? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes.     

Assessment of groundwater contamination using geographic information systems

In this study two sites were selected in order to investigate groundwater contamination and spatial relationships among groundwater quality, topography, geology, landuse and pollution sources. One site is the Asan area, an agricultural district where pollution sources are scattered and which is mainly underlain by granite of Cretaceous age. The other site is the Gurogu area of Seoul city, an industrial district where an industrial complex and residential areas are located and which is mainly underlain by gneiss of Precambrian age. Groundwater samples collected from these districts were analysed for chemical constituents. An attribute value files of chemical constituents of groundwater and the spatial data layers were constructed and pollution properties were investigated to establish out spatial relationships between the groundwater constituents and pollution sources using geographic information systems (GIS).Relatively high contents of Si and HCO₃ ^– in the groundwater from the Asan area reflect the effect of water–rock interaction whereas high contents of Cl^–, NO₃ ^– and Ca²⁺ in the groundwater from the Gurogu area are due to the pollution of various sources. The significant seasonal variation of SiO₂, HCO₂ ^– and Ca²⁺ contents, and that of Ca²⁺ content were observed in the Asan and the Gurogu areas, respectively. Seasonal variation of pollutants such as Cl^–, NO₃ ^– and SO₄ ^2– was not observed in either area. Pollution over the critical level of the Korean drinking water standard has been investigated from 15 sampling sites out of 40 in the Asan area, and 33 sampling sites out of 51 in the Gurogu area. Pollution by NO₃ ^–, Cl^–, Fe²⁺, Mn²⁺, SO₄ ^2– and Zn²⁺ in the groundwater from the industrial district (Gurogu area) and that of NO₃ , SO₄ ^2– and Zn²⁺ in the groundwater from the agricultural district (Asan area) were observed. The principal pollutant in both areas is NO₃ ^–. Deep groundwater from the Asan area is not yet contaminated with NO₃ ^– except for one site, but most of the shallow groundwater site occurring near the potential point sources is seriously contaminated. From the result of buffering analysis, it seems clear that factories and stock farms are the principal pollution sources in the Asan area. The groundwater from the Gurogu area has already been seriously polluted considering the fact of NO₃ ^– contamination of deep groundwater. Chlorine pollution of shallow groundwater in the Gurogu area was also observed. Spatial relationship between pollution level and its source was clarified in this study by using GIS, which will be applicable to the effective management of groundwater quality.     

Effects of ammonia on survival and osmoregulation of various development stages of the shrimp Penaeus japonicus

In Penaeus japonicus, the tolerance to ammonia increased with the development from nauplius to late juvenile. The 48-h LC₅₀ of ammonia in nauplii (III–V), 96-h LC₅₀ in zoeae (I–III), mysis (I–III), post-larvae (PL1) and late juveniles (10.4±1.1 g) were respectively 5.0, 6.1 to 8.1, 9.4 to 10.9, 15.5 and 52.7 mg Nl^-1 (0.5, 0.6 to 0.7, 0.9, 1.3 and 3.1 mg NH₃–Nl^-1). In a chronic experiment (20 d), the LC₅₀ in post-larvae (PL1) was 19.1 (1.4) at 96 h and 16.2 mg Nl^-1 (1.3 mg NH₃–Nl^-1) at 480 h. Osmoregulatory capacity (OC) was calculated as the osmotic gradient between the hemolymph and the external medium at given salinities. The effects of ammonia on OC, Na⁺ and Cl^- regulation and gill Na⁺–K⁺ ATPase activity in late juveniles were examined in fullstrength seawater, SW (1050 mosm kg^-1, 36 S) and in dilute SW (450 mosm kg^-1, 15%.), after 48 or 96 h exposure to various concentrations of ammonia. Ambient ammonia disrupted both hypo- and hyper-osmoregulation; decreased OC resulted from impaired Na⁺ and Cl^- regulation. Gill Na⁺–K⁺ ATPase activity increased in SW and was not affected in dilute SW. The decrease of OC was ammonia-dose-dependent. The threshold ammonia concentrations affecting hypo-OC and hyper-OC were, respectively, 16 (1.3) and 32 mg Nl^-1 (2.3 NH₃–Nl^-1) for a 48 h exposure; these concentrations were lower than the 48-h LC₅₀ value, 65.3 mg Nl^-1 (3.5 NH₃–Nl^-1). The time course of exposure to sublethal ammonia (48 mg Nl^-1) demonstrated that the effect on osmoregulation was time-dependent. This effect was also temporary, and the exposed shrimps recovered control OC values after removal of excessive ambient ammonia. The possibility of using OC as an indicator of physiological condition in osmoregulating crustaceans and the acting mode of ammonia on osmotic and ionic regulation are discussed.     

The influence of macrofauna on estuarine benthic community metabolism: a microcosm study

Effects of benthic macrofauna (Corophium volutator, Hydrobia sp., Nereis virens) on benthic community metabolism were studied over a 65-d period in microcosms kept in either light/dark cycle (L/D-system) or in continuous darkness (D-system). Sediment and animals were collected in January 1986 in the shallow mesohaline estuary, Norsminde Fjord, Denmark. The primary production in the L/D-system after 10 d acted as a stabilizing agent on the O₂ and CO₂ flux rates, whereas the D-system showed decreasing O₂ and CO₂ flux throughout the period. Mean O₂ uptake over the experimental period ranged from 0.38 to 1.24 mmol m^–2 h^–1 and CO₂ release varied from 0.80 to 1.63 mmol m^–2 h^–1 in both systems. The presence of macrofauna stimulated community respiration rates measured in darknes, 1.4 to 3.0 and 0.9 to 2.0 times for O₂ and CO₂, respectively. In contrast, macrofauna lowered primary production. Gross primary production varied from 1.06 to 2.26 mmol O₂ m^–2 h^–1 and from 1.26 to 2.62 mmol CO₂ m^–2 h^–1. The community respiratory quotient (CRQ, CO₂/O₂) was generally higher in the begining of the experiment (0–20 d, mean 1.89) than in the period from Days 20 to 65 (mean 1.38). The L/D-system exhibited lower CRQ (ca. 1) than the D-system. The community photosynthetic quotient varied for both net and gross primary production from 0.64 to 1.03, mean 0.81. The heterotrophic D-system revealed a sharp decrease in the sediment content of chlorophyll a as compared to the initial content. In the autotrophic L/D-system, a significant increase in chlorophyll a concentration was observed in cores lacking animals and cores with C. volutator (The latter species died during the experiment). Due to grazing and other macrofauna activities other cores of the L/D-system exhibited no significant change in chlorophyll a concentration. Community primary production was linearly correlated to the chlorophyll a content in the 0 to 0.5 cm layer. Fluxes of DIN (NH₄ ⁺+NO₂ ^–+NO₃ ^–) did not reveal significant temporal changes during the experiment. Highest rates were found for the cores containing animals, mainly because of an increased NH₄ ⁺ flux. The release of DIN decreased significantly due to uptake by benthic microalgae in the L/D-system. No effects of the added macrofauna were found on particulate organic carbon (POC), particulate organic nitrogen (PON), total carbon dioxide (TCO₂) and NH₄ ⁺ in the sediment. The ratio between POC and PON was nearly constant (9.69) in all sediment dephts. The relationship between TCO₂ and NH₄ ⁺ was more complex, with ratios below 2 cm depth similar to those for POC/PON, but with low ratios (3.46) at the sediment surface.     

Photosynthetic carbon acquisition in the red alga Gracilaria conferta

In this continuing study on photosynthesis of the marine red alga Gracilaria conferta, it was found that ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in crude extracts had a K _m (CO₂) of 85 M. Since seawater contains only ca. 10 M CO₂, it appears that this alga must possess a CO₂ concetrating system in order to supply sufficient CO₂ to the vicinity of the enzyme. Because this species is a C₃ plant (and thus lacks the C₄ system for concentrating CO₂), but can utilize HCO₃ ^- as an exogenous carbon source, we examined whether HCO₃ ^- uptake could be the initial step of such a CO₂ concetrating system. The surface pH of G. conferta thalli was 9.4 during photosynthesis. At this pH, estimated maximal uncatalyzed HCO₃ ^- dehydration (CO₂ formation) within the unstirred layer was too slow to account for measured phostosynthetic rates, even in the presence of an external carbonic anhydrase inhibitor. This observation, and the marked pH increase in the unstirred layer following the onset of light, suggests that a HCO₃ ^- transport system (probably coupled to transmembrane H⁺/OH^- fluxes) operates at the plasmalemma level. The involvement of surface-bound carbonic anhydrase in such a system remains, however, obscure. The apparent need of marine macroalgae such as G. conferta for CO₂ concentrating mechanisms is discussed with regard to their low affinity of Rubisco to CO₂ and the low rate of CO₂ supply in water. The close similarity between rates of Rubisco carboxylation and measured photosynthesis further suggests that the carboxylase activity, rather than inorganic carbon transport and intercoversion events, could be an internal limiting factor for photosynthetic rates of G. conferta.     

Elemental Contamination of Rainwater by Airborne Dust in Tamale Township Area of the Northern Region of Ghana

Rainwater samples were collected from Tamale town in the 1997 and 1998 rainy seasons. During this period road construction in the Tamale area resulted in the generation of suspended dust in the atmosphere. Analysis of the samples for major ions showed elevated levels of Cl^–. Ion ratios with Cl^– (Na⁺/Cl^–, K⁺/Cl^–, Ca²⁺/Cl^–/Cl^– Mg²⁺/Cl^– and SO₄ ^2–/Cl^–) in rainwater samples were higher than the corresponding ratios in seawater. Some samples also showed elevated concentrations of Fe, Mn, Al and Zn, all of which except Zn showed a correlation with the dry periods between rainfall events. Consequently, it was concluded that dust generated from lateritic soils was probably the major cause of the increase in concentration of these metals. Aluminium and Fe concentrations were observed to be higher than the World Health Organization drinking water guide limits.     

Acid–base regulation in the Dungeness crab (Metacarcinus magister)

Homeostatic regulation allows organisms to secure basic physiological processes in a varying environment. To counteract fluctuations in ambient carbonate system speciation due to elevated seawater pCO₂ (hypercapnia), many aquatic crustaceans excrete/accumulate acid–base equivalents through their gills; however, not much is known about the role of ammonia in this response. The present study investigated the effects of hypercapnia on acid–base and ammonia regulation in the Dungeness crab, Metacarcinus magister on the whole animal and isolated gill levels. Hemolymph pCO₂ and [HCO₃ ^?] increased in M. magister acclimated to elevated pCO₂ (330 Pa), while pH remained stable. Additionally, hemolymph [Na⁺], [Ca²⁺], and [SO₄ ^2?] were significantly increased. When challenged with varying pH during gill perfusion, the pH of the artificial hemolymph remained relatively unchanged. Overall, ammonia production and excretion, as well as oxygen consumption, were reduced in crabs acclimated to elevated pCO₂, demonstrating that either (amino acid) oxidation is reduced in response to this particular stress, or nitrogenous wastes are excreted in an alternative form.     

Photosynthetic utilisation of inorganic carbon by seagrasses from Zanzibar, East Africa

Photosynthetic rates of eight seagrass species from Zanzibar were limited by the inorganic carbon composition of natural seawater (2.1 mM, mostly in the form of HCO₃ ⁻), and they exhibited more than three time higher rates at inorganic carbon saturation (>6 mM). The intertidal species that grew most shallowly, Halophila ovalis, Halodule wrightii and Cymodocea rotundata, showed the highest affinity for inorganic carbon (K _1/2 = ca. 2.5 mM), followed by the subtidal species (K _1/2 > 5 mM). Photosynthesis of H. wrightii, C. rotundata, Cymodocea serrulata and Enhalus acoroides was >50% inhibited by acetazolamide, a membrane-impermeable inhibitor of carbonic anhydrase, indicating that extracellular HCO₃ ⁻ dehydration is an important part of their inorganic carbon uptake. Photosynthetic rates of H. wrightii, Thalassia hemprichii, Thalassodendron ciliatum, C. serrulata and E. acoroides were strongly reduced by changing the seawater pH from 8.2 to 8.6 in a closed system. In H. ovalis, C. rotundata and Syringodiumisoetifolium, photosynthesis at pH 8.6 was maintained at a higher level than could be caused by the ca. 30% CO₂ concentration which remained in the closed experimental systems at that pH, pointing toward HCO₃ ⁻ uptake in those species. It is suggested that the ability of H. ovalis and C. rotundata to grow in the high, frequently air-exposed, intertidal zone may be related to a capability to take up HCO₃ ⁻ directly, since this is a more efficient way of HCO₃ ⁻ utilisation than extracellular HCO₃ ⁻ dehydration under such conditions. The inability of all species to attain maximal photosynthetic rates under natural conditions of inorganic carbon supports the notion that seagrasses may respond favourably to any future increases in marine CO₂ levels. Received: 19 March 1997 / Accepted: 31 March 1997     

Automatic potentiometric determination of dissolved oxygen

Commercially available automatic titration systems were tested in 1988 for potentiometric titration of liberated iodine by the Winkler method of oxygen determination. The potentiometric equivalence point was also compared to the manual starch end point. Finally the automatic method was used in order to estimate belowhalocline respiration in the Kattegat, Sweden. Standard deviations of 0.007 ml O₂ l^–1 or 0.1 to 0.3% coefficients of variation (% standard deviation of the mean) were achieved when titrating 25 ml from replicate 60-ml oxygen bottles using the automatic method, or 50 ml manually. The precision for replicate titrations of 50-ml aliquots of 0.001N KIO₃ was <0.05% (0.002 ml 0.01N Na₂S₂O₃) for the automatic method. Titration time for 25-ml aliquots was 2 to 4 min, somewhat longer than for manual titrations (1 to 1.5 min). However, during titration the operator is free to perform other tasks. It is not possible to use automatic sample changers, due to rapid iodine volatilization. The equipment can be handled by relatively unskilled analysts and is suitable for use on board research vessels or in field stations [weight for a Mettler^TM titrator (Mettler Instrumente AG, Greifensee, Switzerland) <10 kg, volume <0.1 m³]. Below-halocline oxygen consumption in the SE Kattegat ranged from 0 to 6 ml O₂ m^–3 h^–1 (mean values for September and October 1988=1.69 and 0.66 ml O₂ m^–3 h^–1, respectively, with 95% confidence limits of ca. ±0.6 ml O₂ m^–3 h^–1).     

Fluorescence studies of dye displacement from DNA by chromium(III) complexes: Evidence for cation induced DNA condensations

The interactions of 10 different chromium(III) complexes with isolated calf thymus DNA have been analysed by studying the electronic and fluoresence spectra of intercalated ethidiumbromide. Triply charged cationic complexes including: [Cr(urea)₆]Cl₃.3H₂O, [Cr(1,10‐phenanthroline)₃](ClO₄)₃.2H₂O, [Cr(2,2'‐bipyridyl)₃] (ClO₄)₃.2H₂O, [Cr(ethylendiamine)₃]Cl₃.3.5H₂O and [Cr(NH₃)₆](NO₃)₃ displaced the dye from DNA. Similar effects were observed in experiments using the non‐intercalating dye bisbenzimidazole ("Hoechst 33258"). However, singly charged cationic, anionic and uncharged chromium(III) complexes such as: cis‐[Cr(1,10‐phenanthroline)₂Cl₂]Cl.2H₂O, cis‐[Cr(2,2'‐bipyridyl)₂Cl₂]Cl.2H₂O, [Cr(glutathione)₂]Na₂, [Cr(cysteine)₂]Na.2H₂O and [Cr(glycine)₃] were unable to displace both ethidiumbromide and bisbenzimidazole from DNA. There was no evidence for the formation of co‐ordinate bonds between chromium(III) and DNA for any of the above complexes. The charge and type of ligand are important in controlling the interaction of chromium(III) with isolated DNA in vitro. Our findings indicate that the outer sphere interaction of a chromium(III) complex with DNA is weak and unlikely to be the mechanism by which chromate causes DNA impairments in vivo and in vitro.     

Photosynthetic carbon acquisition in the red algaGracilaria conferta

Photosynthetic properties of the common red algaGracilaria conferta, collected from the eastern Mediterranean Sea were investigated in 1989, in order to begin evaluating its adaptative strategies with regard to the inorganic carbon composition of seawater, and to test whether the alleged C₄ photosynthesis of anotherGracilaria species is common within the genus. Net photosynthetic rates ofG. conferta were, under ambient conditions of inorganic carbon (ca. 10µM, CO₂ and 2.2 mM HCO ₃ ^- ), not sensitive to O₂ over the range 10 to 300µM, and the CO₂ compensation point was low (ca. 0.005µM). Ribulose-1,5-bisphosphate carboxylase/oxygenase was the major carboxylating enzyme, with a crude extract activity of 175µmol CO₂ g^–1 fresh wt h^–1 while phosphoenolpyruvate carboxylase and phosphoenolpyruvate carboxykinase were present at 70 and 20%, respectively, of that activity. No activities of the decarboxylases NAD-and NADP-malic enzyme could be detected. The¹⁴C pulse-chase incorporation pattern showed thatG. conferta fixes inorganic carbon via the photosynthetic carbon reduction cycle only, with no evidence for photosynthetic C₄ acid metabolism. Photosynthesis at the natural seawater pH of 8.2 was, at 25°C and saturating light, saturated at the ambient inorganic carbon concentration of 2.5 mM. It is proposed that, under ambient inorganic carbon conditions, a CO₂ concentrating system other than C₄ metabolism provides an internal CO₂ concentration sufficient to suppress the O₂ effect on ribulose-1,5-bisphosphate carboxylase/oxygenase and, thus, on photorespiration, in a medium where the external free CO₂ concentration is lower than theK _m(CO₂) of the carboxylating enzyme. Since inorganic carbon, under natural saturating light conditions, seems not to be a limiting factor for photosynthesis ofG. conferta, it likely follows that other nutrients limit the growth of this alga in nature.     

Assessment of Groundwater Quality and Contamination from Uranium-Bearing Black Shale in Goesan–Boeun Areas, Korea

This study was initiated to identify the impact of metals and uranium enriched soil and black shale in groundwater quality and contamination. From a Piper diagram, groundwater was classified into four types as (Ca+Mg)–HCO₃ type, (Ca+Mg)–SO₄ type, the mixed type of these two and Na–HCO₃ type, reflecting the complicated nature of geology of the study area. Silicate weathering appeared to be the major water–rock interaction. In groundwater, metals including Cr, Pb, Cu and V, previously identified as being enriched in soils and black shale, were much lower in concentrations than Korean and US EPA drinking water guidelines. Instead, Fe and Mn caused major water-quality problems. In the artesian groundwater from an abandoned uranium mine, the uranium concentration was 21.3 µg L^–1, slightly higher than EPA guidelines of 20 µg L^–1. Heavy metals in groundwater appeared to be controlled mostly by sorptions on to Fe- and Mn-oxyhydroxides. They could be remobilised in groundwater with changes of pH and Eh conditions due to acid mine drainage from black shale or the recharge of fresh water. Uranium would be associated with carbonate and sulphate complexes in groundwater. Because of the remaining water-quality problems in the study area, we suggested containment of identified mine wastes, considering remedial measures for local problems with Fe and Mn, continuous monitoring of groundwater and developing groundwater from deep aquifers.     

Wet deposition chemistry studies at Suva, Fiji, a remote tropical island site in the south Pacific

A field project encompassing wet-only rainwater sampling was initiated as a bilateral Fiji/Australia activity. Normally, biweekly samples were collected, using a wet-only rainwater sampler, and analysed for H⁺, Na⁺, K⁺, Mg²⁺, NH₄ ⁺, Cl^–, NO₃ ^–, SO₄ ^2–, PO₄ ^3-, methane sulphonic acid, oxalic acid, formic acid and acetic acid. The pH of the rainwater ranged between 5.730 and 4.480 with an average value of 5.176, slightly lower than the pH of unpolluted rainwater saturated with atmospheric CO₂(pH = 5.650). Na⁺and Cl^–were the major ions with average concentrations of 98.15 M and 109.57 M respectively. There is an excellent correlation between the cation sum (average 147.71 eq L^-1) and the anion sum (average 142.12 eq L^-1) attesting to the quality of the data generated. This paper presents the detailed results of the study for a relatively clean remote island site in Suva, Fiji, latitude 18° 09 S, longitude 178° 27 E, height 6 m, and outlines prospects for further work.     

Response of the microbial food web to manipulation of nutrients and grazers in the oligotrophic Gulf of Aqaba and northern Red Sea

The control mechanisms within the pelagic microbial food web of the oligotrophic Gulf of Aqaba and the northern Red Sea were investigated in the spring of 1999. Nutrient conditions and potential grazer impact were manipulated in a series of dilution experiments. Ambient nutrient concentrations and autotrophic biomass were very low (0.23–1.21 µmol NO₃ l^–1, 0.06–0.98 µmol NH₄ l^–1, 1.08–1.17 µmol Si l^–1, 0.08–0.12 µmol P l^–1, 0.15–0.36 µg chlorophyll a l^–1). The planktonic community was characterized by low abundances [3.0–5.5×10⁵ heterotrophic bacteria ml^–1, 0.58–7.2×10³ ultraphytoplankton <8 µm ml^–1 (small eukaryotic photoautotrophs and Prochlorococcus sp., excluding Synechococcus sp.), 0.45–4.4×10⁴ Synechococcus sp. ml^–1, 0.32–1.2×10³ heterotrophic nanoflagellates ml^–1, 1.3–3.8×10³ phytoplankton >8 µm l^–1, 0.93–5.4×10² microzooplankton l^–1] and dominated by small forms (0.2–8 µm). Dinoflagellates and oligotrichous ciliates were the most common groups in initial samples among the phytoplankton >8 µm and microzooplankton, respectively. Results show that bottom-up and top-down control mechanisms operated simultaneously. Small organisms were vulnerable to grazing, with maximum grazing rates of 1.1 day^–1 on heterotrophic bacteria and 1.3 day^–1 on ultraphytoplankton. In contrast, algae >8 µm showed stronger signs of nutrient limitation, especially when the final assemblages were dominated by diatoms. Synechococcus sp. were not grazed and only showed moderate to no response to nutrient additions. The high spatial and temporal variation of our results indicates that the composition of the planktonic community determines the prevailing control mechanisms. It further implies that, at this transitional time of the year (onset of summer stratification), the populations fluctuate about an equilibrium between growth and grazing.Communicated by O. Kinne, Oldendorf/Luhe