Trends and long-term variability of ocean properties at Ocean Station P in the northeast Pacific Ocean [abstract]

Twenty-seven years (1956-1983) of oceanographic data collected at Ocean Station P (50°N/145°W), as well as supplementary data obtained in its neighborhood, have been examined for trends and interannual variability in the northeast Pacific Ocean. There is evidence that the water is warming and freshening and that the isopycnal surfaces are deepening. Trends in oxyty are mostly not significant. The most common periods for the interannual variability appear to be 2 1/2 and 6-7 years. The vertical movement of water accounts for one half of the changes in temperature and salinity and 30% of those in oxyty. Other factors, such as a shift of water masses, may also be important.

Elemental signatures in otoliths of larval walleye pollock (Theragra chalcogramma) from the northeast Pacific Ocean

The population structure of walleye pollock (Theragra chalcogramma) in the northeastern Pacific Ocean remains unknown. We examined elemental signatures in the otoliths of larval and juvenile pollock from locations in the Bering Sea and Gulf of Alaska to determine if there were significant geographic variations in otolith composition that may be used as natural tags of population affinities. Otoliths were assayed by using both electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Elements measured at the nucleus of otoliths by EPMA and laser ablation ICP-MS differed significantly among locations. However, geographic groupings identified by a multivariate statistical approach from EPMA and ICP-MS were dissimilar, indicating that the elements assayed by each technique were controlled by separate depositional processes within the endolymph. Elemental profiles across the pollock otoliths were generally consistent at distances up to 100 μm from the nucleus. At distances beyond 100 μm, profiles varied significantly but were remarkably consistent among individuals collected at each location. These data may indicate that larvae from various spawning locations are encountering water masses with differing physicochemical properties through their larval lives, and at approximately the same time. Although our results are promising, we require a better understanding of the mechanisms controlling otolith chemistry before it will be possible to reconstruct dispersal pathways of larval pollock based on probe-based analyses of otolith geochemistry. Elemental signatures in otoliths of pollock may allow for the delineation of fine-scale population structure in pollock that has yet to be consistently revealed by using population genetic approaches.

Marine bacteria as indicators of upwelling in the Sea

The “oxidase reaction” (using p-amino-dimethyl-aniline oxalate as the reagent) has been used to distinguish oxidase-negative from oxidase-positive bacteria from the sea, when grown on membrane filters. By this means, it has been shown (a) that under conditions of stable stratification of the sea as in the tropics, a relationship exists between the percentage incidence of oxidase negative bacteria in the flora and the depth of the water; (b) that the maximum value for this percentage incidence (100) is reached at or immediately below the upper limit of the oxygen minimum layer; (c) that this percentage value (expressed as Oxⁿvalues) may be used to demonstrate the movements of water masses during upwelling. Such upwelling as indicated by theoretical findings and by temperature determinations along two transects off the west coast of Ceylon during the north east monsoon, has been confirmed by the distribution of Oxⁿvalues at these transects.

A Comparison of the bacterial flora of surface and sub-surface water of the sea off Ceylon

Under stable conditions of stratification of the sea, evidence of generic differences of the associated bacterial flora of the water masses has been obtained, between surface and sub-surface water. Gram negative rods, especially pseudomonads and achromobacters were more frequent at the surface. The fermentative and oxidase negative flora was more frequent in sub-surface water. The surface water in general had a greater variety of bacterial types while the sub-surface water had a flora with a greater range of biochemical activity. These results are discussed in relation to the hydrological condition of the water masses and the bacterial flora of freshly caught fish.

El estuario del Plata: donde el río se encuentra con el mar

The Rio de la Plata estuary is one of the largest estuarine environments of South America. It is characterized by a two-layer vertical salinity distribution and the existence of water masses convergence zones (fronts). Oceanographic scenario greatly influence the biology of the planktonic organisms that live in the water column, the benthic organisms that inhabit the soft sediment bottoms of the estuary, and the fishes, which show a differential degree of penetration into the diluted water of the estuary. Short and frequent events of strong weastward winds ('sudestada') alter completely the oceanographic conditions greatly influencing the especies ecology. Biological production of the estuary is high, and most of their organisms have a marine heritage.

Hydrology and fish distribution at the Sofala Bank (Mozambique)

A brief review is made of the hydrologic conditions at the Sofala Bank, mainly based on the research data obtained from 1978 to 1982. A description is attempted of the circulation pattern and the distribution of water masses in the area, four hydrologic regimes being identified. These are compared with the distributions of different pelagic and demersal fish species. A tendency is found for different groups of species to prefer different hydrologic regimes.

Salinity measurements and use of the Practical Salinity Scale (PSS)

Salinity, temperature and pressure are parameters which govern the oceanographic state of a marine water body and together they make up density of seawater. In this contribution we will focus our interest on one of these parameters, the salinity: accuracy in relation to different purposes as well as observation technique and instrumentation. We will also discuss the definition of salinity. For example most of the Indian Ocean waters are within the salinity range from 34.60-34.80, which emphasize the importance of careful observations and clear definitions of salinity, in such a way that it is possible to define water masses and predict their movements. In coastal waters the salinity usually features much larger variation in time and space and thus less accuracy is sometimes needed. Salinity has been measured and defined in several ways over the past century. While early measurements were based on the amount of salt in a sea water sample, today the salinity of seawater is most often determined from its conductivity. As conductivity is a function of salinity and temperature, determination involves also measurement of the density of seawater is now more precisely estimated and thus the temperature. As a result of this method the Practical Salinity Scale (PSS) was developed. The best determination of salinity from conductivity and the temperature measurements gives salinity with resolution of 0.001 psu, while the accuracy of titration method was about ± 0.02‰. Because of that, even calculation of movements in the ocean is also improved.

Occurrence of whale sharks in coastal waters in the Indian Ocean: an interesting coincidence

Salinity, temperature and pressure are parameters which govern the oceanographic state of a marine water body and together they make up density of seawater. In this contribution we will focus our interest on one of these parameters, the salinity: accuracy in relation to different purposes as well as observation technique and instrumentation. We will also discuss the definition of salinity. For example most of the Indian Ocean waters are within the salinity range from 34.60-34.80, which emphasize the importance of careful observations and clear definitions of salinity, in such a way that it is possible to define water masses and predict their movements. In coastal waters the salinity usually features much larger variation in time and space and thus less accuracy is sometimes needed. Salinity has been measured and defined in several ways over the past century. While early measurements were based on the amount of salt in a sea water sample, today the salinity of seawater is most often determined from its conductivity. As conductivity is a function of salinity and temperature, determination involves also measurement of the density of seawater is now more precisely estimated and thus the temperature. As a result of this method the Practical Salinity Scale (PSS) was developed. The best determination of salinity from conductivity and the temperature measurements gives salinity with resolution of 0.001 psu, while the accuracy of titration method was about ± 0.02‰. Because of that, even calculation of movements in the ocean is also improved.

On the fishing power of monofilament and multifilament gill nets

The authors have discussed the results of comparative fishing, conducted in the Govindsagar reservoir, with simple monofilament and multifilament gill nets. The experiments were conducted both in clear and turbid water. In both these water masses, the monofilament gill net has been found to be more efficient. It is also found that the four major species of fishes of the reservoir have not shown any preference towards a specific gear.

Arabian Sea sub-surface salinity minima (ASSM)

This paper presents the results of the study on the Arabian Sea sub-surface salinity minima (ASSM). The data collected under the North Arabian Sea Environment and Ecosystem Research (NASEER) programme and World Ocean Circulation Experiment (WOCE) has been used in the study. Study of the Arabian Sea water masses is most significant in understanding marine productivity and monsoonal reversal features. Analysis of the data shows that the Arabian Sea sub-surface salinity minima (ASSM) can be found between 25.8 to 26.0 Sigma Theta surfaces. ASSM originates from the south and south east. It is inferred from the results that the salt content of the ASSM varies during different seasons. Appreciable mixing of Arabian Sea salinity minima is observed over Murray Ridge.

Spreading of Persian Gulf water in the northwestern Arabian sea during the month of January

The presence of different water masses in the North Arabian Sea continues to remain of interest to scientists and researchers. Focus on these water masses is due to the unique monsoonal reversal features of the Arabian Sea. The encroachment of Persian Gulf water into the Arabian Sea has been acknowledged and traced. This paper presents the results of an investigation on the spreading patterns of Persian Gulf water in the northwestern Arabian Sea. The study incorporated two different techniques: the core-layer method and the constant sigma-theta surface method on data collected during the North Arabian Sea Environment and Ecosystem Research (NASEER) programme. Horizontal curves of temperature and salinity plotted by both methods show that the Persian Gulf water reduces in concentration as it moves from west to east, whereas the major direction of flow is along the coast of Oman. The results of the study indicate that features of the Persian Gulf water in the northwestern Arabian Sea are so pronounced that either of the method can be used to study and identify the water mass fairly well.

Taxonomía y distribución de los poliquetos pelágicos del Atlántico Sudoccidental

This work is based on the analysis of 420 planktonic samples of 7 oceanopraphic cruises distributed over the Argentine, Uruguayan and South brasilian continental shelf (SW Atlantic ocean), as well as from some oceanic sectors, adjacent to the continental slope. Vertical hauls were performed in all stations from 100 m depth to surface, except in the Walter Herwig cruise (where vertical hauls were predominantly performed out of slope sectors, between 300 and 500 m depth to surface) and Productividad cruise in which only surface waters were hauled. A list of 27 species are determined, corresponding to 5 families: Iospilidae (3 species), Lopadorrhynchidae (4), Alciopidae (9), Typhloscolecidae (5) and Tomopteridae (6). Larvae and epitokous forms of benthonic species are not taken into account. The genus Iospilus is revised, Pariospilus and Iospilopsis being considered their synonyms; the identity of Pariospilus affinis Viguier is maintained, being transferred to the genus Iospilus. The species Vanadis studeri Apstein is redescribed and its synonymy is established. The taxonomic value of the apical glands of Tomopteris species is discussed and some specimens are found to coincide with T. kefersteini in relation to the mentioned glands. All the species found in this work are described and illustrated, a systematic key being added for their identification. Considering the vertical nature of the hauls, it was not possible to specify the habitats of the different species; for this reason they are grouped as species from subtropical and subantartic areas of influence. The first group, made up of 17 species, shows and evident graduation in its latitudinal distribution, some of them being more restricted in their distribution than the others. The second group, of 4 species, is found south to the tropical convergence, in transitional waters, towards cold sectors. The third group, of 6 species, is found to be distributed all along the continental shelf, in subtropical and subantartic regions, and extending their distribution northwards, possibly related to deep water levels. The general scheme is coincident with the distribution of other planktonic groups (Copepods, Euphausiids). As a general feature, neither coastal nor shelf water specimens of pelagic Polychaeta were found, with exception of T. septentrionalis. A comparison with the results in Tebble's paper (1960) in the southwest Atlantic ocean is made, 12 of our species being coincidently found in the same hydrological area by that author. The drift of the main water masses of the South Atlantic ocean is accepted as a possible cause for the distribution of the pelagic Polychaeta of the southwest Atlantic regions.