Nutrient profiles in interstitial water and flux in water-sediment interface of the Zhujiang Estuary of China in summer

The profiles of nutrient salts in the interstitial water of sediment were analyzed in the Zhu- jiang Estuary in the summer of 1999, and based on the profiles of content and characteristic of nutri- ents, the relationship between nutrients in the interstitial water and organic matter decomposition in sediment was discussed. The results showed that ammonium with high content was the main existence form of nutrients in the interstital water of sediment, and the organic matter decomposition was com- pleted in anaerobic condition. The increase of ammonium content in the bottom water resulted from the decomposition of organic matter and release of metabolic production, and the ammonium bottom flux was an important resource for nutrients geochemistry in the Zhujiang Estuary.

Evaluation of the Quality for the Egyptian Red Sea Coastal Waters during 2011-2013

To assess the quality of the Egyptian Red Sea coastal waters for the sustainable use and development, due to its importance for the national income, four field campaigns were annually carried out during the period from 2011-2013 to investigate the hydrography, nutrient salts, heavy metals and petroleum hydrocarbons. Except for the area of Bir Shalatein, the results of beach litter cleared out that the shoreline of the studied area is not affected by man-made litter. No sewage could be observed. The results of the present study showed that water temperature followed seasonal changes in air temperature. Red Sea water is more saline than adjacent Arabian Sea. DO revealed high values and presence of well oxygenated waters. Minor changes in the distribution of pH, BOD, DOM and COD, revealed that limited effects of human impacts and depend mainly on the dynamics of its water as well as on the geographical location. Low Chl-a and TSM concentrations and high transparency revealed that also the effect of human impacts is almost negligible. Significantly higher sea water temperatures, TSM, pH, DO, BOD, DOM, and COD were observed in summer season compared to their corresponding values in winter season. Dissolved inorganic nitrogen concentrations were quite low because there is little nutrient input from soil, agriculture and pollution on land. Based on the annual mean values, the pattern concentrations of dissolved inorganic nitrogen forms followed the order: NO3 > NH4 > NO2. The Red Sea coastal waters are classified as oligotrophic to mesotrophic state. A remarkable increase of PO4 concentration was observed in the middle Red Sea stations due to huge amounts of effluents enriched with phosphate from the main shipping and industry of Phosphate Companies. SiO4 displayed a large variability due to the supply of SiO4, which flows in the Red Sea through the strait of Bab El-Mandab, biological consumption, organic matter decomposition and the partial dissolution of quartz particle transported to the sea from the surrounding desert during sand storms. Concentrations of ammonia, phosphorus, total nitrogen, and total phosphorus were significantly higher in summer compared to their corresponding values in winter. In general, the majority of TN and TP in winter were in the form of organic-N (91.3%) and organic P (96.8%). The mean DIN/DIP ratio revealed high nitrogen concentrations in comparison with that of phosphorous and the surface coastal waters of the Red Sea are principally, P-limited for phytoplankton growth with higher values in winter season compared to summer season. Concentrations of heavy metals were quite low most probably due the absence of major local impacts of any land-based sources and/or any major negative impacts of coastal tourism. Regional variations were almost negligible and except for Mn, Cd, and Hg insignificant seasonal variations were observed. The present study revealed concentrations for metals in the acceptable levels. Furthermore, concentrations of petroleum hydrocarbons were significantly higher in winter than in summer which is mainly attributed to the increase in the rate of evaporation for petroleum hydrocarbons in summer. In general, the maximum concentration was much lower than the harmful concentrations reported for seawater. Correlation coefficients as well as principle component analysis (PCA) were applied.

Assessment of the Hydrochemical Characteristics of the Suez Gulf Coastal Waters during 2011-2013

The coastal region of the Suez Gulf, is one of the most densely industrialized zones in Egypt. In order to assess the quality of Suez Gulf coastal waters for the sustainable use and development, and consequently for the national income, 12 field campaigns were carried out in 3 years (2011-2013). The results of beach litter cleared out that the shoreline of the Suez Gulf, especially Ras Gharib area was subjected to many factors which undoubtedly affected the rate of man-made litter accumulation. The most abundant visible items were general litter as they represented 30.64% of the total items encountered. Oil, seaweeds as well as old and new tar constituted 15.41%, 14.85% and 11.84%, respectively. The increase on the levels of water temperature, Chl-a, TSM, DO, BOD, DOM, COD, ammonium ion, nitrite, nitrate, total phosphorus, silicate and total nitrogen developed a eutrophic region. In general, dissolved inorganic nitrogen (DIN) species were almost 9 times higher in the northern parts compared to the south-ern ones revealing that the northern parts of the Gulf were more affected by human impacts compared to the southern area. Moreover, concentrations of most studied metals such as Zn, Mn, Ni, Cu, Cr, Cd, Pb, and Hg were higher in Northern parts com-pared to southern parts of the Gulf. The concentrations of dissolved metals in the northern and southern Suez Gulf followed the following order: Fe ≥ Zn ≥ Cu > Pb > Mn > Ni > Cr > Cd ≥ Hg. Except for Hg, concentrations of metals were in the accepta-ble ranges recommended internationally. Hg concentrations especially in the northern Suez Gulf were slightly higher than the permissible levels. As the northern parts of the Gulf were more suffered from oil pollution, total petroleum hydrocarbons revealed higher concentrations in the northern parts compared to the southern parts of the Gulf. Seasonal variations, on the other hand, indicated higher levels of DO, BOD, DOM and COD, chloropyll-a, TSM, ammonia, nitrate, total nitrogen in winter compared to their corresponding values in summer. In general, the majority of TN and TP in winter were in the form of organic-N (87.2%) and organic P (94.1%). These percentages were 77.8% and 37.3%, respectively in summer. The surface coastal water of the Suez Gulf was principally, P-limited for phytoplankton growth in different investigated regions. Furthermore, the DIN/DIP ratio was higher (94.2:1) in winter season compared to summer season (6.3:1). Concentrations of Fe, Zn, Cd, and Hg in winter exhibited sig-nificantly higher values compared to their corresponding values in summer. On con-trast, Mn, Ni, Cu, Cr, and Pb exhibited significantly higher values in summer compared to their corresponding values in winter. Furthermore, concentrations of petroleum hy-drocarbons were significantly higher in winter than in summer which is mainly at-tributed to the increase in the rate of evaporation for petroleum hydrocarbons in summer due to the increase in water temperature and water salinity. In general, the maximum concentration was much lower than the harmful concentrations reported for seawater. A stepwise multiple linear regression, analysis of variance (ANOVA), and principle component analysis (PCA) were applied.

Comparison on Purification Effect of Two Macroalgae Species on Prawn Tailwater

[Objectives]This study was conducted to investigate the purification effects of two common large seaweeds on the tail water of prawn farming in greenhouses,and to determine the best culture density of seaweeds.[Methods]Two large seaweed species,Gracilaria lichevoides and Ulva lactuca,were selected to set four culture densities of 0.5,2,4 g/L and a blank control group,respectively.The seaweeds were cultured in 100 L white polyethylene buckets,each of which contained 50 L of tail water from prawn culture.[Results]After 5 d,the nutrient removal rates of the two seaweeds were directly proportional to the density.There was no significant difference in NH_(4)-N removal rate between G.lichevoides and U.lactuca(P>0.05)by two-way analysis of variance,and the NH_(4)-N removal rate of the latter was higher.The removal rates of NO_(3)-N,TN and TP by G.lichevoides were significantly higher than those by U.lactuca(P<0.05).The specific growth rates of seaweeds were negatively correlated with their culture densities.The specific growth rates of G.lichevoides were 5.73%,1.654%and 0.48%,respectively,and those of U.lactuca were 2.01%,1.187%and 0.138%,respectively,when the culture densities were 0.5,2.0 and 4.0 g/L.Two-factor analysis of variance showed that the former was significantly higher than the latter,when the culture density of the two species of seaweeds was 0.5 g/L(P<0.05).The two-way analysis of variance showed that when the culture density of the two kinds of seaweeds was 0.5 g/L,the specific growth rate of G.lichevoides was significantly higher than that of U.lactuca(P<0.05).Based on the above research,the two macroalgae could reduce the nutrients in the wastewater to a large extent,but the culture density determined the scale and economic benefits of seaweed cultivation and further affected the normal growth,metabolism and quality of the seaweeds.[Conclusions]This study provides some theoretical basis for large-scale seaweed farming and biological selection of in-situ ecological restoration of eutrophic seawater.