Sea Level Variations Associated with Upwelling/ Downwelling Along the West Coast of India

A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 2 10 -3 cm s -1 is predicted in July in the southern region off the coast.     

Sea Level Variations Associated with Upwelling/ Downwelling Along the West Coast of India

A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 ×10 -3 cm s -1 is predicted in July in the southern region off the coast.     

Trichodesmium erythraeum (Ehrenberg) bloom along the southwest coast of India (Arabian Sea) and its impact on trace metal concentrations in seawater

The incidence of a large scale Trichodesmium erythraeum bloom along the southwest coast of India (Arabian Sea) observed in May 2005 is reported. Around 4802 filaments of T. erythraeum ml⁻¹ seawater was observed and a colony consisted of 3.6 × 10⁵ cells. The bloom was predominant off Suratkal (12° 59′N and 74° 31′E) with a depth of about 47 m, covering an area of 7 km in length and 2 km width. The concentrations of Zinc, Cadmium, Lead, Copper, Nickel and Cobalt were determined in samples collected from the bloom and non-bloom sites using stripping voltammetry. The observed hydrographical and meteorological parameters were found to be favorable for the bloom. The concentrations of Zinc, Cadmium and Nickel were found to be higher at bloom stations, while the concentrations of Lead, Copper and Cobalt were found to be very low at bloom stations. Elevated concentrations of Cadmium and Cobalt were observed at Valappad mainly due to the decomposition of detrital material produced in the bloom. Statistically significant differences (P > 0.01) in metal concentrations between the bloom and non-bloom stations were not observed except for Copper. Metals such as Lead, Copper and Cobalt were removed from the seawater at all places where bloom was observed. Cadmium was found to be slowly released during the decaying process of the bloom.     

Concentration of Trace Metals and Biochemical Alterations in Various Species of Fishes along the West Coast of India

Ocean Science Journal - This study seeks to evaluate levels of seven trace metals (Cr, Mn, Fe, Cu, Zn, Pb and Hg) and biochemical (proteins, lipids and carbohydrates) alterations in muscle tissue...     

Coloured dissolved organic matter (CDOM) in Southern North Sea waters: Optical characterization and possible origin

The variability and origin of the Coloured Dissolved Organic Matter (CDOM) were studied in the Belgian coastal and adjacent areas including offshore waters and the Scheldt estuary, through the parameters: absorption at 375 nm, a_CDOM(375), and the slope of the absorption curve, S. a_CDOM(375) varied between 0.20 and 1.31 m⁻¹ and between 0.97 and 4.30 m⁻¹ in the marine area and Scheldt estuary, respectively. S fluctuated between 0.0101 and 0.0203 nm⁻¹ in the marine area and between 0.0167 and 0.0191 nm⁻¹ in the Scheldt estuary. The comparative analysis of a_CDOM(375) and S variations evidenced different origins of CDOM in the BCZ. The Scheldt estuarine waters showed decreasing a_CDOM(375) values with increasing salinity but constant S value of ∼0.018 nm⁻¹ suggesting a dominant terrestrial origin of CDOM. On the contrary, samples collected in the marine domain showed a narrow range of a_CDOM(375) but highly variable S suggesting the additional presence of autochthonous sources of CDOM. This source was evidenced based on the sorting of the marine offshore data according to the stage of the phytoplankton bloom when they were collected. A clear distinction was made between CDOM released during the growth stage characterized by high S (∼0.017 nm⁻¹) and low a_CDOM(375) and the decay phase characterized by low S (∼0.013 nm⁻¹) and high a_CDOM(375). This observation was supported by CDOM measurements performed on pure phytoplankton cultures which showed increased CDOM release along the wax and wane of the bloom but decreasing S. We concluded that the high variability of the CDOM signature in offshore waters is explained by the local biological production and processing of CDOM.     

辽宁沿海泥炭堆积与全新世海面变化

辽宁沿海分布有丰富的泥炭资源，主要为埋藏泥炭，属于低位型的草本泥炭。按其成因可分为泻湖型、河漫滩型和沟谷型泥炭三种类型。在整个全新世时期均有泥炭形成，可分为早、中、晚全新世三个发育期，中全新世是辽宁沿海泥炭发育的最盛时期；沉积速率为０．２５～１．１ｍｍ／ａ。全新世海侵，约在距今６０００～７０００ａ达到最大范围；近五千年来海面在下降过程中有波动和相对稳定时期。     

溶解有机碳在混合水中的行为研究

研究溶解有机碳(DOC)在海水和黄河水所组成的混合水中的迁移转化行为,结果表明,海水和已过滤黄河水混合时,DOC呈近似的保守性;海水与未过滤的黄河水混合时,DOC呈明显的非保守性。通过研究沉积物对DOC的解吸过程,发现沉积物在盐水中能解吸出DOC,随着盐度的增大,其解吸量也迅速增大。因此可以认为,DOC在河口区的非保守行为是DOC的絮凝和颗粒物的解吸共同作用的结果。     

海洋中二甲基亚砜的来源、分布及迁移转化

二甲基亚砜(DMSO)是海水中的主要溶解态甲基硫化物,DMSO在二甲基硫(DMS)的生物地球化学循环中起着重要的作用。它能通过DMS的光化学氧化和细菌氧化生成,可作为DMS的1个汇,也可以通过生物直接合成或其它途径产生。DMSO同时又可以被酶、细菌、植物等还原为DMS,因此,DMSO又可充当DMS的1个源。DMSO除了能被还原为DMS外,还可能会被细菌氧化为SO42-,在氯过氧化物酶作用下被H2O2氧化为DMSO2等。海洋中DMSO的测定通常采用还原剂NaBH4将其还原为DMS后,再利用气相色谱进行测定。海水中DMSO的分布不均匀,高浓度区是那些温度较高,光照充足、浮游植物较多、生物活性较高的表层水或近岸水。     

On vertical velocity fluctuations and internal tides in an upwelling region off the west coast of India

Hourly fluctuations of vertical velocity in relation to components of flow and wind and temperature oscillations at a morring site in the shelf waters off the west coast of India are discussed. The vertical velocities were computed from a time series of vertical temperature profiles assuming that horizontal advection of temperature is negligible. The computed values at a depth of 40 m during the 72-h period of observation were of the order of 10⁻¹ to 10⁻²cm s⁻¹, with a mean value of −2·77 × 10⁻² cm s⁻¹ indicating a net upward movement of water. The computed vertical velocity showed fluctuations of about 2–3 h, in addition to weaker signals of about 12 h. Based on the spectral estimates, we speculate that these fluctuations of 2–3 h in the vertical velocity may be caused by the fluctuations in the along-shore wind. The oscillations of isotherms found in the temperaturedepth time series and the spectral estimates of temperature and cross-shore flow component showed a periodicity of about 12 h, which indicated the presence of semi-diurnal internal waves. The fact that these internal wave troughs were associated with the measured onshore flow suggested that the waves were propagating offshore. The computed stability parameters showed little evidence of instability or mixing. It was found that the isotherm troughs in the temperaturedepth time series at about 12-h period coincided with high vertical shear in the cross-shore direction and low values of Brunt Vaisälä frequency.     

春季东海北部近岸水体中的溶解无机碳和有机碳的分布特征及其影响因素

根据2010年4月在东海北部近岸的调查,分析了研究海域溶解无机碳（DIC）和溶解有机碳（DOC）的含量及其分布状况,并分别对DIC、DOC与温度、盐度、表观耗氧量等要素的关系进行了初步探讨。结果表明,春季研究海域表、底层DIC平均含量分别为24．54mg／L和25．03mg／L,平面分布趋势均为近岸高于远岸,象山口附近...     

Macrofaunal density, biomass and composition of estuarine sediments and their relationship to the river plume of the Rhone River (NW Mediterranean)

This study investigates species community patterns and sediment relationships of benthic macrofauna off the Rhone river delta. Along a WE transect, changes in diversity, density, biomass and trophic structure were coupled with the mean extension of the river dilution plume. Species number and diversity were at a minimum off the river mouth, below the area of the minimum surface salinity. Density decreased by a factor 2 and biomass by a factor 5 from the fluvial to the marine system. These features are due to high overload of terrestrial organic matter in the river prodelta as evidenced by the carbon isotopic signature of surface sediment and by pigment content. On the basis of a non-metric MDS analysis and of Dufrêne and Legendre method (1997), groups of stations and characteristic species associated were identified. These species, mainly small capitellids, spionids, lumbrinerids and sternaspids, correspond to a successional dynamic in response to changes in sedimentation conditions, mainly in organic matter quality of the surface sediment. The succession observed in space was similar to described in macrotidal estuaries and off other deltaic systems all over the world and to that observed in time following the Rhone river severe flood events. Results suggest that organic matter quality is an important factor with regard to benthic macrofauna successions and recovery mechanisms following disturbances. The differences observed between the Rhone deltaic system and the general model of relations between shelf processes and discharge of large rivers are attributed to a more regular supply of organic material from terrestrial origin on the Rhone continental shelf.     

Distrubution of Dissolved and Particulate Iron, copper and Manganese in the Shelf waters of the Ross sea (Antarctica)

Abstract. During the austral summer 1997–98, within the framework of the activities of the Climatic Long-term Interaction for the Massbalance in Antarctica (CLIMA) Project of the Italian National Program for Antarctic Research (PNRA) in the Ross Sea, measurements were conducted to focus on the role of dissolved iron, copper and manganese as micronutrients, and on their distribution in suspended particulate matter in different water masses. Sampling was carried out in two selected shelf areas, both important for formation and mixing processes of the water bodies.
Metal data were evaluated together with physical measurements and classical chemical parameters such as oxygen and nutrients.
In both the studied areas, the distribution of dissolved metals along the waste column confirmed their micronutrient behaviour, showing depletion where phytoplanktonic activities occurred.
The trend of particulate metals underlined the scavenging phenomena along the water column and presented an interesting correlation at intermediate depths with the amount and origin of suspended matter.     

Polychaetes (Annelida) in the Gut Contents of Goatfishes (Mullidae), With New Polychaete Records for the Mediterranean Coast of Israel and the Gulf of Elat (Red Sea)

Abstract. An analysis was made of polychaete prey in the guts of 5 species of goatfishes ( Mullidiw): Upeneus usymmetricus , a Lessepsian migrant goatfish collected from both Mediterranean and Elat (Red Sea) locations; Mullus sunnuletus, ill. burbcuus , and U. moluccensis , a Lessepsian migrant taken only in the eastern Mediterranean; and Mulloides flavolineatus , collected in the Gulf of Elat. Mullus barbutus accounts for nine new polychaete records for the Mediterranean coast of Israel. Mulloides flavolineatus fed on two species which arc new records for the Gulf of Elat; one, Lumbrineris meteorunu , is a new record for the Red Sea. The polychaete prey provides some information on the ecology of the fishes: There appears to be little overlap regarding polychaete prey among the different goatfish species in the Mediterranean.     

Provenance Signature of Pre-Cambrian and Mesozoic Rocks in the Nearshore Placers of Konkan,Central West Coast of India

Heavy mineral studies of the nearshore placer deposits of the Konkan Coast reveal a dominant assemblage comprised of garnet and kyanite along with other accessory minerals like epidote, olivine and rutile. The heavy mineral assemblage of the study region shows a characteristic suite of 17 types of heavy minerals. Their abundance shows hardly any drastic variation in the four bays studied. Overwhelming presence of minerals like garnet and kyanite in the studied four bays points to the source as metamorphic rocks. The presence of etched garnets, overgrown zircons and etched kyanites corroborate the recycling of paleo-sediments into the bay. Characterization of opaques under the microscope also corroborates the influence of a metamorphic source, rather than the adjoining basaltic rocks. However, the absence of metamorphic rocks in the hinterland suggests the possibility of deposition of sediments predominantly from offshore. Factor analysis results also corroborate the overwhelming influence of metamorphic rocks in the present study region rather than the abutting basalts.     

Dissolved iron in the Australian sector of the Southern Ocean (CLIVAR SR3 section): Meridional and seasonal trends

We report measurements of dissolved iron (dFe, <0.4 μm) in seawater collected from the upper 300 m of the water column along the CLIVAR SR3 section south of Tasmania in March 1998 (between 42°S and 54°S) and November–December 2001 (between 47°S and 66°S). Results from both cruises indicate a general north-to-south decrease in mixed-layer dFe concentrations, from values as high as 0.76 nM in the Subtropical Front to uniformly low concentrations (<0.1 nM) between the Polar Front and the Antarctic continental shelf. Samples collected from the seasonal sea-ice zone in November–December 2001 provide no evidence of significant dFe inputs from the melting pack ice, which may explain the absence of pronounced ice-edge algal blooms in this sector of the Southern Ocean, as implied by satellite ocean-color images. Our data also allow us to infer changes in the dFe concentration of surface waters during the growing season. South of the Polar Front, a comparison of near-surface with subsurface (150 m depth) dFe concentrations in November–December 2001 suggests a net seasonal biological uptake of at least 0.14–0.18 nM dFe, of which 0.05–0.12 nM is depleted early in the growing season (before mid December). A comparison of our spring 2001 and fall 1998 data indicates a barely discernible seasonal depletion of dFe (0.03 nM) within the Polar Frontal Zone. Further north, most of our iron profiles do not exhibit near-surface depletions, and mixed-layer dFe concentrations are sometimes higher in samples from fall 1998 compared to spring 2001; here, the near-surface dFe distributions appear to be dominated by time-varying inputs of aerosol iron or advection of iron-rich subtropical waters from the north.     

Biology and Population Dynamics of Donax trunculus L. (Bivalvia: Donacidae) in the South Adriatic Coast (Italy)

Biology and population dynamics of the suspension-feeding wedge clam Donax trunculus (Linnaeus, 1758) were studied for 13 months (November 1994–April 1996) along the Italian Southern Adriatic coast near the Lagoon of Lesina. Specimens were found at depths between 0 and 2 m, mainly in fine grain bottoms. The spatial coastal distribution showed an intraspecific segregation between young and adult wedge clams. A unimodal recruitment (length >4 mm) occurred in winter (December–February). Length frequency distributions were used to determine age and growth rate. Three year classes were regularly observed and their growth pattern defined. The population showed a maximum length of 37 mm and a longevity of 4 years. Analysis of seasonal variations in the reproductive cycle showed that gametogenesis occurred in spring in females. After the spawning season (March–July) females of D. trunculus remained in a resting stage from August to January.     

The Fauna of Floating Cyanobacterial Mats in the Oligohaline Eulittoral Zone off Hiddensee (South-west Coast of the Baltic Sea)

Abstract. The fauna — including macrofauna, meiofauna, and large ciliates — of floating cyanobacterial mats in a brackish shallow-water area was studied by analysing six 20 cm² pieces of mat. Although these microbial aggregations were scarcely 1 cm thick, their total meiofauna abundance was about five times as high as in the uppermost 4 cm of the adjacent sediment. The mat fauna was dominated by harpacticoids, although large ciliates, rotifers, nematodes, and oligochaetes were also markedly more abundant than in the sediment. All species occurring in the mats were members of the surrounding sediment fauna. Out of the 47 species found, only a few, among them predominantly the harpacticoid, Mesochra lilljeborgi B oeck , 1864, and the nematode Daptonema setosum ( bütschli , 1874), accounted for the majority of the individual abundance in the mats. Both are regularly found in sulphidic biotopes near Hiddensee. As SEM micrographs revealed, the oligochaete Paranais litoralis (O. F. M üller , 1788) and the harpacticoid Cletocamptus confluens (Schmeil, 1894) were apparently optimal substrates for dense lawns of cyanobacteria. This indicates possible close interactions between the meiofauna and these microbiota. The frequent predation of histophagous ciliates on nematodes and harpacticoids, which were probably weakened by oxygen deficiency and/or high sulphide concentrations, were not only a sign of a generally neglected pathway in the food chain, but also impressively emphasized the huge variety of interactions taking place between meio- and microfauna within this specific benthic microcosm. Because of their floating character, the mats can play an important role in the dispersal of benthic fauna.     

Activity Pattern of the Sea-Star, Marthasterias glacial is, in Port-Cros Bay (France, Mediterranean Coast)

Abstract. Tagged individuals of Marthasterias giacialis (L.) followed in situ for 24 h cycles or for up to 4 consecutive days show that sea-star activity is not only nocturnal; we observed a non-synchronized (between individuals) movement, with 1 or 2 (ocassionally 3) peaks; movement, occurs mainly between 6:00 p.m. and 9:00 a.m., without a clear peak at the population level, independent the prevailing light conditions (for 6:00–9:00p. m. and 6:00–9:00a. m. periods). M. giacialis shows periods of inactivity ranging from 1 to 3 days. It is hypothesized that the study site is visited for short term feeding raids by individuals coming from the deep water and then moving back.     

Distribution and nature of organic matter in recent sediments of Lake Nokoué, Benin (West Africa)

The distribution and nature of organic matter clearly identify the principle sectors of the lagoon which vary according to hydrological and sedimentological conditions. The central area frequently includes coarse ancient fluviatile sediments. The rare organic matter there offers aliphatic and nitrogenous characters which may be derived from both the origin of organic matter (algae and meiofauna) and the level of oxygenation prevailing during deposition. In the southern sector, highly oxygenated conditions resulting from sea currents generated by the Cotonou outlet could cause the elimination of labile compounds, and hence be responsible for the high degradation state of organic matter. In the western sector, still water conditions allow fine sediments to be deposited. This frequently leads to the accumulation of organic matter showing such reducing conditions that they allow the integration of sulphur in humic compounds and a decrease of their solubility. In the northern area, the contribution of terrestrial material supplied by the Ouémé and Sô rivers is clearly indicated by the low average percentages of hydrolyzable fraction, C/N ratios ranging between 9 and 15, while H/C and N/C ratios are low in humic acids.