Enrichment of inorganic nutrients in the Inner Saronikos Gulf (1973–1976)

This paper is concerned with the enrichment of inorganic nutrients in the Inner Saronikos Gulf near the Athens sewage outfall. The Inner Gulf tends to accumulate nutrients above the background level, especially ammonia which was about four times more than the background value. Comparison of nutrient enrichment was made between the Inner Gulf and Elefsis Bay. It was found that Elefsis Bay contained considerably more nutrients than the Inner Gulf. This was mainly due to the different sources of nutrients as well as the morphology of each area and the circulation of the waters.     

Metal pollution in the Saronikos Gulf

Sediment samples from the Saronikos Gulf and Elefsis Bay were analysed for weak acid extractable Zn, Fe and Cu, as well as for organic carbon. The main sources of pollution (fertilizers, factory, sewage outfall, Piraeus Port and the heavily industrialized part of Elefsis Bay) showed levels that were higher than background by a ratio of 1000 for Cu, 3500 for Fe, 700 for Zn and 10 for organic carbon. The concentrations fell rapidly to background at a distance of 5 km and the affected area was estimated at 40 km².     

An index of marine pollution in the Saronikos Gulf

A method is investigated for monitoring the urban pollution in the Saronikos Gulf. In this research, measurements of nutrients and salinity were carried out. In this phase, the correlations between dilution relating to salinity and diminution coefficients relating to nutrients were defined by classical sampling methods. A wide variability of the pollution level of the. environment is occurring and the continuous analysis of phosphates is proposed in order to monitor the pollution.     

Trace elements in Acartia clausi from Elefsis bay of the Upper Saronikos Gulf,Greece

Twelve trace elements (antimony, arsenic, cadmium, chromium, cobalt, copper, iron, managenese, mercury, scandium, selenium and zinc) were determined by neutron activation analysis in a planktonic copepod (Acartia clausi) from Elefsis Bay of the Upper Saronikos Gulf, Greece. During the first cruise (January 1974) higher levels of most of these trace elements were found in this copepod collected from a polluted area of the bay. This trend however was not observed during the second cruise (February 1974) possibly due to the termination of the active vertical convection. Lower levels of cobalt, similar levels of iron and slightly increased levels of chromium were found in Elefsis Bay Acartia clausi from those reportedin Acartia clausi from the Bay of Roquebrune. Slightly increased concentrations of antimony and zinc as well as lower concentrations of arsenic and cadmium were found in Acartia clausi than those reported in other Copepoda. No significant differences were found for copper, manganese and mercury. More data are needed to confirm if higher levels of antimony, chromium and zinc found in Acartia clausi are due to the pollution of the bay.     

Enrichment by inorganic nutrients and oxygen utilization rates in Elefsis Bay (1973–1976)

This paper concerns the enrichment by nutrients and the oxygen utilization rates of an intermittently anoxic basin. The concentration of nutrients and dissolved oxygen have been determined during seasonal surveys of water characteristics. The oxygen utilization rates ranged between 1.3 and 1.8 ml l.⁻¹ month⁻¹ from March to June and were considerably higher than those reported for oceanic waters. The nutrients enrichment appears to be considerably influenced by eutrophication and human activity. During anoxic conditions in summer, the mineralization of organic matter was associated with consequent accumulation of enormous amounts of nitrogen (ammonia), phosphates and silicates. Nutrient ratios underwent great fluctuation mainly due to anoxic conditions.     

Effects of resuspension on benthic fluxes of oxygen,nutrients, dissolved inorganic carbon,iron and manganese in the Gulf of Finland,Baltic Sea

The effect of resuspension on benthic fluxes of oxygen (O₂), ammonium (NH₄⁺), nitrate (NO₃^?), phosphate (PO₄^3?), silicate (Si(OH)₄), dissolved inorganic carbon (DIC), total dissolved iron (Fe) and total dissolved manganese (Mn) was studied at three different stations in the Gulf of Finland (GoF), Baltic Sea during three cruises in June–July 2003, September 2004 and May 2005. The stations were situated on different bottom types in the western, central and eastern part, respectively, of the open GoF. The fluxes were measured in-situ using the autonomous Göteborg benthic lander. To simulate resuspension events, the stirring speed was increased in two of the four chambers of the lander after approximately half of the incubation time. The other two chambers were used as control chambers. Clear effects of resuspension were observed on the oxygen fluxes where an increase of the consumption was observed in 88% of the cases and on average with 59% (stdev=53). The NH₄⁺ fluxes were affected in 50% of the cases (4 out of 8 incubations) at stations with low bottom water oxygen concentrations, but in no cases where the bottom water was oxygenated (0 out of 9 incubations). The NH₄⁺ fluxes decreased by 26±27% in 2005 and by 114±19% in 2003. There was no clear effect of resuspension on the fluxes of any of the other solutes in this study. Thus, resuspension events did not play a significant role in release/uptake of NO₃^?, PO₄^3?, Si(OH)₄, DIC, Fe and Mn in GoF sediments. However, increased oxygen consumption as a result of resuspension may lead to spreading of anoxic/suboxic bottom water conditions, and thus indirectly to increased benthic release of phosphate, ammonium and iron.     

Seasonal upwelling on the Western and Southern Shelves of the Gulf of Mexico

An 8-year database of sea surface temperature (SST), 7 years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color images, wind fields, and numerical model results are analyzed to identify regions and periods of coastal upwelling on the western and southern shelves of the Gulf of Mexico. On the seasonal scale, it is found that on the Tamaulipas, Veracruz, and southwestern Texas–Louisiana shelves there are upwelling favorable winds from April to August, when southeasterly winds are dominant and cold SST anomalies associated with upwelling are observed along their coasts. However, during summer, values of chlorophyll-a concentration are lower than those in autumn and winter, which are high due to advection of old bloom biological material from upstream. During winter, there is a cold front on the Tamaulipas shelf produced by advection of cold water from the Texas–Louisiana shelf and not due to upwelling. On the eastern Campeche Bank, persistent upwelling is observed due to favorable winds throughout the year with cold SST and large chlorophyll-a content along the inner shelf from May to September. On the Tamaulipas shelf, the summer upwelling delays the annual SST peak until September, while in most of the Gulf SST peaks in August. This difference is due to the end of the upwelling favorable wind conditions and the September seasonal current reversal.     

Formation mechanisms of heavy oils in the Liaohe Western Depression,Bohai Gulf Basin

The Liaohe Oilfield in the Liaohe Western Depression of the Bohai Gulf Basin is the third-largest oil producing province and the largest heavy oil producing oilfield in China. A total of 65 oil samples,35 rock samples and 36 reservoir sandstone samples were collected and analyzed utilizing conventional geochemical and biogeochemical approaches to unravel the mechanisms of the formation of the heavy oils. Investigation of the oils with the lowest maturity compared with the oils in the Gaosheng and Niuxintuo oilfields indicates no apparent relation between the maturity and physical properties of the heavy oils. It is suggested that the heavy oil with primary origin is not likely the main mechanism re-sponsible for the majority of the heavy oils in the Liaohe Western Slope. The absence and/or depletion of n-alkanes etc.,with relatively low molecular weight and the occurrence of 25-norhopane series in the heavy oils as well as the relatively high acidity of the oils all suggest that the majority of the heavy oils once experienced secondary alteration. The fingerprints of the total scanning fluorescence (TSF) of the inner adsorbed hydrocarbons on the reservoir grains and the included hydrocarbons in fluid inclusions are similar to that of the normal oils in the area but are different from the outer adsorbed and reser-voired free oils at present,further indicating that most of the heavy oils are secondary in origin. Analyses of bacteria (microbes) in 7 oil samples indicate that anaerobic and hyperthermophilic Ar-chaeoglobus sp. are the dominant microbes relevant to oil biodegradation,which coincides with the shallow commercial gas reservoirs containing anaerobic bacteria derived gas in the Gaosheng and Leijia teotonic belts. The biodegradation most likely occurs at the water/oil interface,where the forma-tion water is essential for microbe removal and nutrient transportation. We think that biodegradation,water washing and oxidization are interrelated and are the main mechanisms for the formation of the heavy oils. Biodegradation was the predominant process with water washing being a prerequisite,and oxidization acting as a metabolic manifestation. This study provides unique approaches for further investigation of the formation mechanisms of heavy oils in general,and may provide some important insight for the exploration of shallow biogas in the area.     

声波探测显示的渤海湾西部全新世断层活动

本文展示了渤海湾西部浅地层声纳探测成果，讨论了渤海湾西部全新世和晚更新世上部地层划分、晚冰期与冰后期的沉积地层学特点及最新断裂活动的证据等。声波探测由于具有很高的分辨率和信号发射频度，可以获得高品质浅地层剖面，显示出沉积地层的结构与构造细节，如斜层理等三角洲沉积标志特征可清晰显示，水平层理不发育的黄土堆积特征也有显示。在声波剖面中地层界面的中断和弯折变形显示了最新断裂活动的证据，依据地层学资料，确定其年代距今仅为几千年，即全新世中期。这些断层的平面位置与基底或第三纪地质构造图中的断层位置一致，表明有些断层活动贯穿了更新世并延续到全新世，这些勘探成果对渤海西部断层活动性的鉴定具有重要意义。在声波剖面中还发现一些垂向小型结构构造，其成因不明，是否代表了某种地质事件，有待进一步深入研究。     

Modelling for anchovy recruitment studies in the Gulf of Lions (Western Mediterranean Sea)

Anchovy (Engraulis encrasicolus) is an important commercial species and one of the most abundant pelagic fish in the Gulf of Lions and the Catalan Sea. The factors influencing its recruitment are crucial to fisheries and ecological research. Among those factors transport of larvae by hydrodynamics (currents) is important because it determines whether the organisms can reach areas favourable to recruitment or are dispersed. Therefore, the first step in anchovy recruitment modelling is to simulate North-western Mediterranean Sea circulation. Several years (2001–2008) of hydrodynamics were simulated with the MARS-3D code. The resulting simulated currents and salinity are used by Lagrangian tool, Ichthyop, to transport anchovy eggs and larvae to the Western Mediterranean Sea. The aim of this study is to understand the main hydrodynamic processes that control anchovy transport and the effects of diel vertical migration on the transport and final distribution of anchovy.     

Interaction between inorganic nutrients and organic matter in controlling coral reef communities in Glovers Reef Belize

We studied the responses of algae, corals, and small fish to elevated inorganic fertilizer, organic matter, and their combination over a 49-day summer period in cages that simulated the coral reef in the remote Glovers reef atoll, Belize. The addition of organic matter reduced while fertilization had no effect on the numbers of herbivorous damsel and parrotfishes. All measures of algal biomass were influenced by fertilization. The combined inorganic and organic enrichment produced the highest algal biomass, which is most likely due to the combined effect of higher nutrients and lower herbivory. The cover of turf and total algae were influenced by all treatments and their interactions and most strongly and positively influenced by fertilization followed by organic matter and the combination of organic matter and inorganic fertilizer. The inorganic and combined treatments were both dominated by two turf algae, Enteromorpha prolifera and Digenia simplex, while the nonfertilized treatments were dominated by brown frondose algae Lobophora variegata, Padina sanctae, and Dictyota cervicornis. The organic matter treatment had greater cover of P. sanctae and D. cervicornis than the untreated control, which was dominated by Lobophora variegata, also the dominant algae on the nearby patch reefs. Crustose corallines grew slowly ( approximately 2.5 mm/49 days) and were not influenced by the treatments when grown on vertical surfaces but decreased on horizontal coral plates in the combined organic matter and fertilization treatment. No mortality occurred for the two coral species that were added to the cages. Porites furcata darkened in the fertilized cages while there was a mix of paling and darkening for a small amount of the coral tissue of Diploria labyrinthiformes. Inorganic fertilization stimulates small filamentous turf algae and Symbiodinium living in coral but inhibits brown frondose algae. Organic matter inhibits small herbivorous fish, L. variegata, and encrusting coralline algae when growing on horizontal surfaces.     

Short-term variations in mesozooplankton,ichthyoplankton, and nutrients associated with semi-diurnal tides in a patagonian Gulf

The relationships between the distribution of different zooplankton and ichthyoplankton stages and physical and chemical variables were studied using samples and data (CTD profiles, ADCP and current meter measurements, nutrients, mesozooplankton, ichthyoplankton) obtained from different strata during two 24-h cycles at two oceanographic stations in a Chilean Patagonian gulf during the CIMAR 10-Fiordos cruise (November, 2004). A station located at the Chacao Channel was dominated by tidal mixing and small increments in surface stratification during high tides, leading to decreased nutrient availability. This agreed with short periods of increased phytoplankton abundance during slack waters at the end of flood currents. Increases in larval density for all zooplankton and ichthyoplankton taxa corresponded to the flooding phases of the tidal cycle. When the larval density data were fit to a sinusoidal model, the regression coefficients were high, suggesting that tides are important features that modulate short-term variations in plankton abundance. All larvae did not vary synchronously with the tidal phase; rather, time lags were observed among species. The abundances of older individuals of the copepodite Rhincalanus nasutus and all zoea stages of the squat lobster Munida gregaria increased during night flood tides, whereas younger stages increased during daytime flood tides. At a station located at the Queullin Pass, which was dominated by vertical stratification patterns, the variations in peak larval density were better fitted to the semi-diurnal sea level fluctuations. Other evidence indicated internal tides below the pycnocline, which could promote larval transport in deeper layers. In the overall picture that emerges from this study, planktonic organisms from different habitats and phylogenetic origins seem to respond to the local tidal regimes. In some cases, this response might be beneficial, transporting these individuals inshore to areas that are rich in food during the peak biological production season.     

Integrated use of biomarkers (superoxide dismutase, catalase and lipid peroxidation) in mussels Mytilus galloprovincialis for assessing heavy metals' pollution in coastal areas from the Saronikos Gulf of Greece

Mussels are used as sentinel organisms and bioindicators to evaluate the toxic effects of chemical pollutants in marine organisms, especially heavy metals, representing an important tool for biomonitoring environmental pollution in coastal areas. Antioxidant defence enzymes play an important role in cellular antioxidant defence systems and protect from oxidative damage by reactive oxygen species (ROS). Indigenous mussels Mytilus galloprovincialis of the Saronikos Gulf of Greece were used for monitoring heavy metal pollution in three polluted sites in the area and in one unpolluted site. Seasonal variations of the activity of antioxidant defence enzymes, superoxide dismutase (SOD) and catalase (CAT), as well as lipid peroxidation (LP) were measured as biomarkers in a period of three years in relation to concentrations of trace metals in their gills and mantle and compared to mussels from an unpolluted sampling site. SOD activity increased at least 2 fold at the polluted sites when compared to the control site (the high activity was recorded in the spring time). CAT activity was increased 2-3 times at the polluted sites, with high activity in the winter and spring time, compared to the control site. LP concentration was twice higher at the polluted sites, following the same seasonal pattern. Trace metals contents in mussels collected at polluted sites were 3-4 fold higher compared to the control site and showed moderate variations along the months, with a winter maximum followed by a summer pre-spawning minimum matching the seasonal trends of temperature and salinity. Our results showed that metal pollution in the Elefsis Bay (the most polluted coastal area) causes relatively medium levels of oxidative stress in tissues of mussels due to cellular oxy-radical generation. This study, which is the first in the area, showed that seasonal variations of the activity of antioxidant defence enzymes and LP concentrations in mussels can be used as potential biomarkers of toxicity for long-term monitoring in marine coastal ecosystems.     

Dissolved inorganic nutrients and organic substrates in the River Warnow (North-Eastern Germany) – Utilisation by bacterioplankton

After 1990, external loads of Central European rivers with inorganic nutrients (nitrogen and phosphorus) and organic material were reduced because of changed environmental laws. However, in the eutrophic lowland River Warnow, North-Eastern Germany, nitrate concentrations remained high with 35–185 μmol l⁻¹ without a significant decrease since 1992. In contrast, phosphate concentrations, varying between 0.3 and 5.2 μmol l⁻¹ during the growth season 2002, decreased significantly over the years. However, its concentrations still exceeded 1 μmol l⁻¹ regularly in the growth seasons. This load led to a substantial accumulation of organic matter additional to high terrestrial inputs. Despite the high organic load, the remineralising bacteria were mainly inactive in River Warnow. Therefore, the composition of the dissolved organic material, especially its bioavailability, were investigated during the growth season 2002 and discussed with other potential controlling factors. River Warnow carried a high load of dissolved organic carbon (14 mg l⁻¹), especially of humic substances (5.5 mg C l⁻¹). Bacterial abundance (12×10⁶ ml⁻¹) as well as production (1.7 μg C l⁻¹ h⁻¹) depended on temperature. During late spring and summer at constantly higher temperatures, bacterial production correlated positively to readily utilisable substrates and to humic compounds. Thus, the bacterial community in River Warnow may be well adapted or contain enough species using the available amino acids and carbohydrates as well as humic matter compounds. However, calculated from protozoan biomass, grazing may control bacterial biomass and perhaps community composition profoundly, what lead to the low percentages of active bacteria.     

An Evaluation of Coulomb Stress Changes from Earthquake Productivity Variations in the Western Gulf of Corinth,Greece

Spatial and temporal evolution of the stress field in the seismically active and well-monitored area of the western Gulf of Corinth, Greece, is investigated. The highly accurate and vast regional catalogues were used for inverting seismicity rate changes into stress variation using a rate/state-dependent friction model. After explicitly determining the physical quantities incorporated in the model (characteristic relaxation time, fault constitutive parameters, and reference seismicity rates), we looked for stress changes across space and over time and their possible association with earthquake clustering and fault interactions. We focused our attention on the Efpalio doublet of January 2010 (M = 5.5 and M = 5.4), with a high aftershock productivity, and attempted to reproduce and interpret stress changes prior to and after the initiation of this seismicity burst. The spatial distribution of stress changes was evaluated after smoothing the seismological data by means of a probability density function (PDF). The inverted stress calculations were compared with the calculations derived from an independent approach (elastic dislocation model) and this comparison was quantified. The results of the two methods are in good agreement (up to 80 %) in the far field, with the inversion technique providing more robust results in the near field, where they are more sensitive to the uncertainties of coseismic slip distribution. It is worth mentioning that the stress inversion model proved to be a very sensitive stress meter, able to detect even small stress changes correlated with spatio–temporal earthquake clustering. Data analysis was attempted from 1975 onwards to simulate the stress changes associated with stronger earthquakes over a longer time span. This approach revealed that only M > 5.5 events induce considerable stress variations, although in some cases there was no evidence for such stress changes even after an M > 5.5 earthquake.     

Processing of humic-rich riverine dissolved organic matter by estuarine bacteria: effects of predegradation and inorganic nutrients

The bioavailability of predegraded dissolved organic matter (DOM) from a humic-rich, boreal river to estuarine bacteria from the Baltic Sea was studied in 39-day bioassays. The river waters had been exposed to various degrees of bacterial degradation by storing them between 0 and 465 days in dark prior to the bioassay. The resulting predegraded DOM was inoculated with estuarine bacteria and the subsequent changes in DOM quantity and quality measured. During the incubations, dissolved organic carbon (DOC) and oxygen concentrations decreased, indicating heterotrophic activity. Coloured DOM was degraded less than DOC, indicating a selective utilization of DOM, and humic-like fluorescence components increased during the incubations. The amount of DOC degraded was not affected by the length of DOM predegradation. The percentage of bioavailable DOC (%BDOC) was higher in experiment units with added inorganic nitrogen and phosphorus than without addition (on average 13.5 % and 9.0, respectively), but had no effect on the degradation of fresh, non-predegraded, DOC (%BDOC 12.0 %). Bacterial growth efficiency (BGE) was highest (65 ± 2 %) in the units with fresh DOM, and lowest in units with predegraded DOM and no added inorganic nutrients (11 ± 4 %). The addition of inorganic nutrients increased the BGE of predegraded DOM units by an average of 28 ± 4 %. There was no significant effect on BGE by length of predegradation after the initial drop (<3 months). This study suggests that both the length of predegradation and the inorganic nutrient status in the receiving estuary has consequences to carbon cycling and will determine the amount of terrestrial-derived DOC being ultimately assimilated into marine food webs.