Influence Of Oceanic Waters Research Articles

Zn/Si records in diatom opal from Prydz Bay, East Antarctica

The Zn/Si records of diatom opal from Prydz Bay were investigated. The results show that the Zn/Si ratios range from 8 to 53μmolmol−1. The ratio from the continental slope is higher than those from the shelf. The difference in Zn/Si records could be attributed to the change of bioavailable Zn via the upwelling of Zn2+-rich deep water or the influence of oceanic water on the slope. However, phytoplankton productivity influences Zn/Si records on the continental shelf. Increased productivity leads to elevated Zn-pumping, and eventually to higher Zn/Si ratio in diatom opal. In this case, it is suggested that Zn/Si proxy could be a signal of marine productivity on the continental shelf of Prydz Bay. The down core profile of Zn/Si records shows an increase in marine productivity over the last century.

Short-Term Variability of Nutrients and Fecal Indicator Bacteria within the Gold Coast Seaway, Southern Moreton Bay (Australia)

Significant urban development surrounding the Gold Coast Broadwater and upper catchment has resulted in concerns about degrading water quality of the estuarine system. The Gold Coast Seaway plays an important role in the exchange of estuarine and oceanic waters influencing the intertidal waters of the region. Water quality within the Gold Coast Seaway and the immediately adjacent Broadwater was investigated three times at three sample depths at 13 sample locations. Conductivity, temperature, and depth casts, total (nitrogen and phosphorus) and dissolved inorganic (NOx and NH4 ) nutrients, and fecal indicator bacteria were measured at hourly intervals to compare the water quality under different tidal conditions at each location. Hydrological data were also collected. From these measurements, the intratidal variability of the Seaway waters was determined. Observed current velocities ranged from 0.001 to 0.909 m s−1 and 0.018 to 1.8 m s−1 during neap and spring tide periods, respectively. Physical parameters and nutrient concentrations demonstrated typical cyclic variations, with the influence of tidal and diurnal cycles apparent. Near minimum and maximum concentrations were generally observed at high and low water, respectively, indicating the influence of oceanic water during flood tides and catchment waters during ebb tides. Significant correlations were observed between surface water salinity values and total nitrogen and phosphorus concentrations. Fecal coliforms and Enterococcus spp. concentrations were low (<60 colony-forming units per 100 mL−1), with no significant trends apparent between concentration and sample location, depth, or tidal phase.

Physico-chemical factors involved in rivers and lagoons invasion by water hyacinth, Côte d’Ivoire

The invasion of freshwaters and coastal ecosystems by Eichhornia crassipes in tropical and subtropical countries causes serious economic and ecological problems. In the present work, the seasonal distribution of Eichhornia crassipes and abiotic factors that control its distribution in rivers and lagoons from Cote d’Ivoire were reported. Our data show that Eichhornia crassipes proliferation in lagoons was more related to freshwater discharges. By contrast, salinity inhibits its proliferation particularly during dry season when the influence of oceanic waters is significant. In rivers, Echhornia crassipes proliferation in rivers was completely different from one river to another. Higher proliferation of Echhornia crassipes in Comoe and Bia rivers was found during the wet season, while in Tanoe river the maximal proliferation was obtained in the dry season. Nutrient concentrations in rivers and lagoons were generally low due to their uptake accumulation of phosphorus in leaves, roots and rhizomes of Echhornia crassipes was different depending on aquatic systems. Higher phosphorus conditions (in rivers), Eichhornia crassipes accumulate more phosphorus in the rhizomes than in the other parts. By contrast, in the lower phosphorus conditions (in lagoons), Eichhornia crassipes accumulates more phosphorus in the leaves than in the other parts. Key words: Eichhornia crassipes, West Africa, coastal water, abiotic factors.

Life history reconstruction of modern and fossil sockeye salmon ( Oncorhynchus nerka) by oxygen isotopic analysis of otoliths, vertebrae, and teeth: Implication for paleoenvironmental reconstructions

We evaluate the use of oxygen isotope values of biogenic apatite for tracking freshwater to marine migration in modern and fossil Pacific sockeye salmon. Oxygen isotope analyses of otoliths, vertebrae, and teeth of three anadromous modern sockeye salmon from Alaska establish a basis for the interpretation of fossil vertebrae and tooth apatite from Pleistocene sockeye salmon of the Skokomish River Valley, Washington. High resolution δ 18O profiles in salmon otoliths provide, at a monthly resolution, a detailed record of individual history including continental rearing, migration to sea, seasonal variation in sea surface temperatures during marine life, and spawning migration before capture. Pacific salmon teeth are constantly renewed with the last set of teeth forming under the influence of freshwater. Therefore, they do not allow inference concerning sea-run versus landlocked life history in fossil salmon. Salmon vertebrae are also ambiguous indicators of life history regarding fresh versus marine water because centra are minimally ossified in the freshwater stages of life and the outermost layer of vertebral bone might be resorbed to provide nutrients during the non-feeding phase of the spawning migration. Therefore, δ 18O values of accretionary growth rings in sea-run salmon vertebrae are dominated by the marine signal only if they are not diagenetically altered in freshwater deposits. In Pleistocene sockeye reported here, neither the teeth nor vertebral apatite present clear marine δ 18O values due to the combined effects of tooth replacement and diagenetic alteration of bone and dentine. δ 18O(PO 4) values of fossil vertebrae are intermediate between δ 18O(PO 4) values of enamel and basal tooth dentin. Assuming a similar rate of isotope exchange of vertebrae and dentine with freshwater during diagenesis, these results are interpreted to reflect formation of the teeth under the influence of freshwater, and formation of the vertebrae under the influence of oceanic water. Our approach demonstrates that when appropriate knowledge of tissue formation is available, isotopic differences between altered and unaltered tissue holds promise of distinguishing between marine and freshwater origin of the tissues.

Influence of Subantartic and Subtropical Oceanic Water on the Zooplankton and Hydrology of Waters Adjacent to the Derwent River Estuary, South-eastern Tasmania

The oceanic influence on coastal waters adjacent to the mouth of the Derwent River estuary was examined over a season using zooplankton samples. There is strong evidence to indicate the influence of oceanic water in Storm Bay and the mouth of the Derwent River estuary. The occurrence of indicator species suggests that the area is invaded by subantarctic water from August to January and by subtropical water most strongly in February and March. The seasonal abundance and distribu- tion of the major copepods (12 species), chaetognaths (three species), one euphausiid and one tunicate species are described in detail and the importance of these species as indicators of intrusion and mixing of water masses in this region is evaluated.