Water masses and decadal variability in the East Sea (Sea of Japan)

Water masses in the East Sea are newly defined based upon vertical structure and analysis of CTD data collected in 1993–1999 during Circulation Research of the East Asian Marginal Seas (CREAMS). A distinct salinity minimum layer was found at 1500 m for the first time in the East Sea, which divides the East Sea Central Water (ESCW) above the minimum layer and the East Sea Deep Water (ESDW) below the minimum layer. ESCW is characterized by a tight temperature–salinity relationship in the temperature range of 0.6–0.12 °C, occupying 400–1500 m. It is also high in dissolved oxygen, which has been increasing since 1969, unlike the decrease in the ESDW and East Sea Bottom Water (ESBW). In the eastern Japan Basin a new water with high salinity in the temperature range of 1–5 °C was found in the upper layer and named the High Salinity Intermediate Water (HSIW). The origin of the East Sea Intermediate Water (ESIW), whose characteristics were found near the Korea Strait in the southwestern part of the East Sea in 1981 [Kim, K., & Chung, J. Y. (1984) On the salinity-minimum and dissolved oxygen-maximum layer in the East Sea (Sea of Japan), In T. Ichiye (Ed.), Ocean Hydrodynamics of the Japan and East China Seas (pp. 55–65). Amsterdam: Elsevier Science Publishers], is traced by its low salinity and high dissolved oxygen in the western Japan Basin. CTD data collected in winters of 1995–1999 confirmed that the HSIW and ESIW are formed locally in the Eastern and Western Japan Basin. CREAMS CTD data reveal that overall structure and characteristics of water masses in the East Sea are as complicated as those of the open oceans, where minute variations of salinity in deep waters are carefully magnified to the limit of CTD resolution. Since the 1960s water mass characteristics in the East Sea have changed, as bottom water formation has stopped or slowed down and production of the ESCW has increased recently.     

The relationship of anchovy and sardine to water masses in the Peruvian Humboldt Current System from 1983 to 2005

The Humboldt Current System (HCS) is dominated by two pelagic species; Peruvian anchovy or anchoveta (Engraulis ringens) and sardine (Sardinops sagax). Using data from 43 acoustic surveys conducted from 1983 through 2005 by the Peruvian Marine Institute (IMARPE), we examined the distribution of these two species relative to water masses. We tested the hypothesis that anchovy was found more frequently in upwelled cold coastal water (CCW) and mixed waters (MCW) than in other water types and that sardine was more associated with more offshore oceanic surface subtropical water (SSW). Surface temperature, salinity, latitude, season and distance to the coast data were used to define water masses. Results using generalized additive models (GAM), modelling sardine and anchovy presence–absence as a function of year, water body, bottom depth and latitude, showed that anchovy were primarily found in CCW and MCS, while sardine were more ubiquitous relative to water masses with some predilection for SSW. These results were supported by various indexes of anchovy and sardine distribution versus water mass as well as temporal and location variables.     

Relative molar mass distributions of chromophoric colloidal organic matter in coastal seawater determined by Flow Field-Flow Fractionation with UV absorbance and fluorescence detection

A new method for the characterization of chromophoric colloidal organic matter in seawater has been applied to samples from the Baltic Sea, Kattegatt and Skagerrak seas. Size fractionation of the sample by Flow Field-Flow Fractionation and measurement of the fluorescent and UV absorbing properties of the individual size fractions result in a relative molar mass distribution (RMM) of the optical properties. The RMM distributions have been used to estimate number and weight average relative molar masses, and polydispersity indices. At least two sources of coloured organic matter were identified from the ratio of fluorescence to UV: the Baltic surface water and the Skagerrak deep water. The dominating processes were mixing and dilution, but processes such as photo bleaching of fluorescence are also believed to be important. The RMM distribution derived from UV detection (1150–1300 Dalton) increased with increasing salinity while that derived for fluorescence (1500–1250 Dalton) decreased with increasing salinity. The specific UV absorbance taken as a proxy of the aromaticity of the chromophoric organic material showed decreasing trend with both increasing salinity and increasing UV derived weight average relative molar mass. Increasing polydispersity of the colloidal material was also observed as a function of salinity.     

Seasonal Variability of the Thermohaline Characteristics and Volumetric Statistical Parameters of Water Masses in the Drake Passage

On the basis of the many-year monthly average thermohaline data of the oceanographic array, we study some regularities of the seasonal cycle in the fields of temperature, salinity, and the characteristics of water masses in the Drake Passage. We obtain and analyze the amplitude and phase parameters of seasonal oscillations of the investigated quantities. By using the volumetric statistical T, S-analysis, we deduce quantitative estimates of the annual variations of the volumes of main water masses in the Drake Passage. Possible mechanisms responsible for the phenomena observed in this region are discussed.__________Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 62–73, November–December, 2004.     

Summer phytoplankton pigments and community composition related to water mass properties in the Gulf of Gabes

Variations in phytoplankton pigments and community composition were examined in the Gulf of Gabes in relationship to water mass properties, characterised by the influence of the Modified Atlantic Water and by the thermal stratification. Data were collected on board the R/V Hannibal during July 2005.Distinct water masses were identified using cluster analysis of temperature–salinity (T–S) characteristics. Three major clusters appeared based on the combined effects of temperature and salinity. The first cluster was identified as the cool and less salty bottom Modified Atlantic Water (MAW). The warmer and saltier Mediterranean Mixed Water (MMW) represented the second cluster. The third cluster was the Transition Water (TW) separating the two previous clusters.The pigment and taxonomic composition of these water masses were examined. Chlorophyll a was rather low (<200 ng l⁻¹). Chlorophyll b was generally the most abundant accessory pigment and fucoxanthin dominated the accessory pigments in the MAW. Proportions of chlorophyll a associated with different phytoplankton classes were estimated using CHEMTAX software, and did not present significant variations among water groups. The results pointed out variations in the relative contribution of each phytoplankton taxa in each station group. Chlorophytes and prasinophytes accounted for 65% of chlorophyll a in the MMW. Diatoms and chlorophytes were relatively abundant in the MAW contributing to almost 63% of chlorophyll a. An unstructured community, slightly dominated by prasinophytes, chlorophytes and cryptophytes, characterised the TW. Different trophic statuses were observed in these water masses, the MMW and the MAW being characterised by mesotrophy, while an oligotrophy was observed in the TW. Nutrient availability, particularly the P-limitation supported by the summer stratification, as revealed by the high N:P ratio (greater than 20), seems to enhance the development of small-sized phytoplankton, thereby supporting the regenerated production.     

Effect of low salinity on the survival of recently hatched veliger of Nassarius reticulatus (L.) in estuarine habitats: A case study of Ria de Aveiro

The effect of low salinity on the survival of recently hatched veliger of the gastropod Nassarius reticulatus (L.) was studied under laboratory conditions at 17 °C ± 1 °C. Significant mortality occurred for salinities ≤ 17 psu and the LS₅₀ (salinity that causes 50% mortality) varied from 14.5 psu to 17.2 psu for exposures between 1 h and 48 h, respectively. The results were included in a mathematical model in order to estimate the mortality of N. reticulatus veliger in Ria de Aveiro under different salinity scenarios determined by numerical simulation. The model predicts a massive mortality of veliger immediately after their eclosion (1 h) in Ria de Aveiro during spring tide when the river input reaches its expected maximum — a situation that has been observed occasionally and may overlap a massive eclosion of veliger in the water. Except in this extreme situation, the mortality in Ria de Aveiro is generally restricted to the upstream limits of the channels. The results indicate that N. reticulatus recruitment in estuaries may strongly depend on the prevailing salinity regime.     

Nitrous oxide solubility in water and seawater

The solubility of nitrous oxide in pure water and seawater has been measured microgasometrically over the range 0–40°C. The data have been corrected for nonideality and are fitted to equations in temperature and salinity of the form used previously to fit the solubilities of other gases. The fitted values have a precision of 0.1% and an estimated accuracy of 0.3%. The nonideal behavior of nitrous oxide—air mixtures is discussed, and the solubility of atmospheric nitrous oxide is presented in parametric form. A similar parametric representation for the solubility of atmospheric carbon dioxide is given in the Appendix.     

Effect of zinc on regeneration in the fiddler crab Uca pugilator and its interactions with methylmercury and cadmium

After multiple autotomy (one chela and six walking legs) fiddler crabs (Uca pugilator) were exposed to zinc chloride, cadmium chloride, methylmercuric chloride or combinations of these metals. Zinc at 1, 3 and 5 ppm had a retarding effect on limb regeneration, which was amplified in water of reduced salinity. Methylmercury at 0·5 ppm and cadmium at 1·0 ppm have previously been found to retard regeneration. When crabs were exposed to meHg and Zn the effects were additive, both in sea water (30% salinity) and in water of reduced salinity (7–8%). However, when crabs were exposed to combinations of Zn and Cd the effects were antagonistic and the rate of regeneration was almost that of controls. In water of 7–8% salinity the Cd effect was greatly intensified and growth was almost totally prevented. The presence of Zn counteracted this and allowed growth and ecdysis to occur.     

Signatures of different water masses in δ<Superscript>18</Superscript>O values,relative abundance of <Emphasis Type="Italic">G. Bulloides</Emphasis> and total planktonic foraminiferal assemblage across the Indian Ocean sector of the southern ocean: Initial results

Nineteen surface sediment samples, collected onboard ORV Sagar Kanya during the 199C and 200th (the pilot expedition to Southern Ocean) cruises along a north-south transect between 1.92° S to 55.01° S latitude and 67.88° E and 44.89° E longitude, were studied for total planktonic foraminiferal assemblage, relative abundance and the oxygen isotopic values of the indicator planktic species Globigerina bulloides. These profiles were compared with the latitudinal variations in the average salinity and nutrient (phosphate) contents of the top 100 meters water column. The initial results have traced the signatures of salinity linked variations of different water masses in the study region. The influence of Australian Mediterranean Water (AAMW) has been noticed in the present dataset.     

Water masses in the Gulf of Aden

Hydrographic data collected from Gulf of Aden since 1920 have been compiled to identify and refine the definitions of water masses in the Gulf of Aden (GA) and to describe their spatio-temporal variability. Four water masses have been identified based on their θ-S characteristics. The Red Sea Water (RSW) that flows from the Red Sea is the most prominent water in the GA; this occupies about 37% of the total volume of Gulf of Aden. The Gulf of Aden Surface Water (∼3%) forms as a mixture of local water and the water from western Arabian Sea during winter and Red Sea surface water during summer. The intermediate water, identified as Gulf of Aden Intermediate Water (GAIW), occupies about 9% of the total volume of GA; a characteristic salinity minimum is associated with it at σ_θ=26.50 kg m⁻³. The northward spread of sub-tropical subsurface water from the south appears to be the major source of GAIW. The bottom water, named Gulf of Aden Bottom Water, showed the least variability. It was formed due to the mixing of Red Sea Water and water of southern origin. Mixing triangles have been used to analyze the composition of water in the GA.     

Low-Frequency Temperature Variability at Fukue Island Located Southwest of the Tsushima Straits

Sea surface temperature (SST) and sea surface salinity variations at Fukue Island (located southwest of the Tsushima Straits) were investigated. In spring, low-frequency SST fluctuations with periods of 10–20 days predominate. Synthetic analysis of in situ observation and satellite infrared image reveals that these SST fluctuations are caused by movement of mixed warm water masses which have a temperature intermediate between those of the Kuroshio and the East China Sea (ECS) shelf waters. Since these fluctuations do not correspond with those in the Tsushima Straits, it is indicated that these water masses can hardly pass the Tsushima Straits while retaining their original water properties. In July, SST fluctuations with a period of several days are also found at Fukue Island. Since these SST fluctuations show an opposite correspondence with its salinity fluctuations and a good correspondence with the SST fluctuations at Okinoshima in the Tsushima Straits, it is inferred that warm and low-salinity water originated from the ECS shelf water causes these fluctuations and intrudes into the Tsushima Straits.     

北黄海及渤海变性水团的初步分析

根据1978—1980年渤海及北黄海70个测站的表、底层温、盐资料,用预先给定控制临界值的聚类方法,在该海域划分出5个水团。分析结果表明。1.渤黄海暧水团在冬季为高盐特征,夏季为中盐性质;其分布范围在冬—春季较小而夏—秋季较大。2.渤海水团为中温中盐性质:其温、盐度变化较小而冬—春季范围较大。3.黄海冷水团是一个高盐水团,它在5个水团中保守性最强,而从5月至8月范围较大。4.渤海沿岸水是一个不稳定的水团,其盐度较低,温度变化较小,春季和秋季范围较大而夏季和冬季较小。5.江河冲淡水是温度变化较大的低盐水,其范围夏季大而冬季小。水团的分布,在地理位置上是从该海区之东向西,一层套一层,而各水团在不同季节有自己的模式。此外,本文还探讨了水团消长变化和渔场的关系。     

Latitudinal trends in morphological characteristics of <Emphasis Type="Italic">Neogloboquadrina pachyderma</Emphasis> (Ehrenberg) along a north–south transect in the south-western Indian Ocean

A total of 25 surficial sediment samples (Peterson grab, gravity and piston cores), collected during the Pilot Expedition to Southern Ocean (PESO) 2004 cruises 199C and 200 onboard the ORV Sagar Kanya along a N–S transect between 9.69°N and 55.01°S, and 80 and 40°E in the Indian Ocean sector of the Southern Ocean (SW Indian Ocean), have been investigated for various morphological features—test size, mean proloculus size and coiling direction (dextral/sinistral forms)—of the planktic indicator species Neogloboquadrina pachyderma (Ehrenberg). The results show that the coiling directions co-vary with temperature and salinity, the abundances of sinistrally coiled forms increasing towards higher latitudes (south of 40°S), whereas dextrally coiled forms show a reverse trend. Similarly, overall test and proloculus sizes depend largely on the physicochemical properties (salinity, temperature, nutrients, calcium saturation) of the ambient water masses. These observations suggest that, particularly at the boundaries between different water masses, variations in morphological features of N. pachyderma can meaningfully be used to reconstruct paleoceanographic conditions from Indian Ocean sediments.     

Long-term physical,chemical and biological changes in a small,urban estuary

The Diep River estuary, a small estuary in suburban Cape Town, South Africa, has been subject to disturbance for centuries. Several earlier studies have documented conditions in the system, providing baselines against which to measure more recent changes. This study: (i) describes major physical and hydrological changes that have occurred within this estuary; (ii) documents faunistic changes subsequent to earlier biological surveys; and (iii) provides an up-to-date faunal list. Salinity measurements and both invertebrate and fish samples were taken at five stations along the estuary in summer and winter 2014. A census of sandprawn Callichirus kraussi densities was also undertaken to compare with earlier surveys. Developments within the Diep River catchment and estuary have resulted in extensive changes in flow and salinity regimes, causing marked reductions in summer salinity levels, changes in frequency of mouth closure, and deteriorations in water quality. These have resulted in major changes in faunal composition and distribution, including an increase in numbers of non-indigenous species. Surveys in the early 1950s recorded 47 invertebrate species, whereas only 23 were found in 1974. A total of 23 species were again recorded in 2014, but these included several freshwater forms not previously reported, which had entered the system due to lowered salinity values, as well as new alien introductions. Only six of the 69 taxa recorded were reported by all three surveys. There have been substantial declines in sandprawn abundance, from 40 million in 1998 to just over 12 million in 2014. In all, 12 fish species were recorded in the 1950s, nine in 1974, but only five in 2014, including the newly detected invasive mosquito fish Gambusia affinis and the translocated tilapia Tilapia sparrmanii. Thus, only three of the original native fish species remain. Contrary to these losses, the present bird fauna appear to be more abundant and diverse than previously. Regular monitoring is recommended to obtain a clearer understanding of ongoing changes, and major management interventions will be needed if further degradation is to be prevented.     

Water masses and hydrography in the tropical Pacific during Japanese Pacific Climate Study '91 cruise

Hydrographic measurements by CTD were made in the western-central Equatorial Pacific (160°W–147°E) during the Japanese Pacific Climate Study cruise in January–February 1991. InT-S diagram, three water masses are seen in the layer of kg/m³: salinity water corresponding to the Tropical Water of eastern South Pacific origin, less saline water in the North Pacific, and water with salinity between the above two, found on the equator. In three meridional sections (160°W–160°E), the Tropical Water of eastern South Pacific origin extends further equatorward than the climatological data of Levitus (1982).     

舟山渔场及其邻近海域水团的季节特征

根据2001年夏季和2002年冬季两次现场调查所收集的CTD和营养盐资料,利用模糊聚类分析法,对舟山渔场及其邻近海域水团的季节特征进行了分析.结果表明,舟山渔场及其邻近海域水团的配置、分布范围、温盐特性和营养盐含量都有明显的季节特征.其中,冬季在全海域共有3个水团(江浙沿岸水、台湾暖流表层水和黄海混合水),而夏季则存在4个水团(江浙沿岸水、台湾暖流表层水、台湾暖流深层水和黄海混合水);冬季,江浙沿岸水的分布范围较小,温度偏低,盐度略高,营养盐偏高,而夏季,其分布范围较大,温度偏高,盐度偏低,营养盐偏低;冬季,台湾暖流表层水北伸最强,厚度最厚,温度最低,盐度最高,硅酸盐和硝酸盐偏高,而夏季,则北伸最弱,厚度最薄,温度最高,盐度最低,硅酸盐和硝酸盐偏低;台湾暖流深层水是一个季节性水团,它含有较丰富的营养盐;黄海混合水的分布范围和营养盐含量也都呈现出明显的季节特征.     

APPLICATION OF THE CLUSTERING METHOD IN ANALYSING SHALLOW WATER MASSES AND MODIFIED WATER MASSES IN THE HUANGHAI SEA AND EAST CHINA SEA

The idea of modified water masses is introduced and a cluster analysis is used for determining the boundary of modified water masses and its variety in the shallow water area of the Huanghai Sea (Yellow Sea) and the East China Sea. According to the specified standards to make the cluster, we have determined the number and boundary of the water masses and the mixed zones.The results obtained by the cluster method show that there are eight modified water masses in this area. According to the relative index of temperature and salinity,the modified water masses are divided into nine different characteristic parts. The water, masses may also be divided into three salinity types. On the TS-Diagram, the points concerning temperature and safinity of different modified mater masses are distributed around a curve, from which the characteristics of gradual modification may be embodied. The variation ranges of different modified water masses are all large, explaining the intensive modification of water masses in th     

Oxygen and nutrient fluxes through the Straits of the Cretan Arc (March 1994–January 1995)

The Straits of the Cretan Arc are the gateways through which water exchanges between the Cretan Sea and the SE Ionian and NW Levantine Seas. Dissolved oxygen and nutrient fluxes have been quantified for the major straits — Antikithira, Kassos and Karpathos — by combining chemical bottle-sample data and current measurements obtained during the PELAGOS Project during 1994–1995. Two water masses, Cretan Deep Water (CDW) and Transitional Mediterranean Water (TMW) dominate the circulation through the straits and lead to a vertical redistribution of nutrients in the Eastern Mediterranean Sea.The transport of chemicals through the major straits of the Cretan Arc appears to be highly variable. In the Antikithira and Kassos Straits, a net export of oxygen and nutrients from the Cretan Sea towards the open waters of the Eastern Mediterranean was observed throughout the entire study period. In contrast, a net inflow of oxygen and nutrients of Levantine origin was taking place through the Karpathos Strait. It is concluded that the export of nutrients through the Antikithira and Kassos Straits are almost completely balanced by the net import through the Karpathos Strait.     

AN ANALYSIS OF MODIFIED WATER MASSES IN THE YELLOW SEA AND EAST CHINA SEA

The waters in the shallow part of the Yellow Sea and East China Sea are affected greatly by climatic and geographical conditions and fail to possess homogeneity and conservativeness like oceanic waters. They have apparent difference in modified degrees, so we may regard a certain range of mixed water as a relatively independent one. In fact, the study of water masses in the shallow sea means a modified analysis of waters. The idea of modified water masses is introduced, i. e., a water body which holds the similar physical and chemical characters, occupies a certain space, and varies seasonally and regularly. On the T-S diagram, it displays as a certain amount of points aggregated together, the centre of which changes regularly and may have a process of combination and separation.According to the clustering method, there are eight modified water masses in this area. They may also be divided into three salinity types. On the T-S diagram, the points concerning temperature and salinity of different modified     

Spring distribution of dissolved organic matter in a system encompassing the Northeast Water Polynya: Implications for early-season sources and sinks

This study addresses sources and diagenetic state of early-season dissolved organic matter (DOM) in the Northeast Water Polynya (NEWP) area northeast of Greenland from distributions of humic substance fluorescence (HSfl), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) in the water column inside and outside the NEWP area. The water masses of the polynya area had acquired their spring/summer temperature–salinity characteristics at the time of sampling, and also had individual, different DOM signatures. DOC concentrations were variable within and among water masses in the polynya area, indicating patchy local sources and sinks of DOC. PySW and polynya intermediate water (PyIW) had higher average DON concentrations and average lower C:N ratios than polynya bottom water (PyBW), indicating a larger fraction of fresh DOM in PySW and PyIW than in PyBW. Ice-covered, polynya area surface waters (PySW) had higher DOC concentrations (113±14 μM, n=68) than surface water (SW) outside the polynya area (96±18 μM, n=6). The DOM C:N ratios in a low-salinity, ice-melt subgroup of PySW samples indicate labile material, and these low-salinity surface waters appeared to have a local DOC and DON source. In contrast, HSfl was significantly lower inside than outside the NEWP area. Despite the lower HSfl values within the NEWP area, the PySW values were high when compared to open-ocean water. There were no local terrestrial sources for HSfl to the NEWP area and the East Greenland Current is therefore proposed as a likely source of allochtonous HSfl. When HSfl was used as a conservative tracer, up to 70% of the water in PySW and PyIW was found to be derived from SW, which contains a high fraction of water from the East Greenland Current. Similarly, a mixing model based on HSfl indicated that 80% of early-season DOC and 90–100% of early-season DON in PySW and PyIW were derived from SW, indicating a potentially high fraction of terrestrially-derived, relatively refractory DOM in the early-season NEWP area.