Examination of reactive phosphate fluxes in an eutrophicated coastal area.

Reactive phosphate (RP) fluxes over sediment in an eutrophic bay were obtained under different conditions. The results were assessed together with water column, sediment solid, and liquid-phase parameters. The RP fluxes ranged from 0 to 1,300 µgatP × m(-2)d(-1) day depending on the sediment site and other variables. At stations with relatively high net RP fluxes, the clay fraction was >3% and disproportionate with salinity, which explained why the RP effluxes decreased by inhibition of the organic coating on particulate matter with increased SO(4) (-2) ions and good competition of RP anions with SO(4) (-2). The RP flux in Fe/RP ratios >2 in surface water decreased to approach a minimum asymptotically, which was thus defined with a hyperbolic curve to determine the maximum rate of the RP flux (J(RP)). The [RP(porewater)](initial)/[RP(ambient)] (initial) ratios were suggested to govern the net RP flux regionally, so the critical value where the RP flux turns positive could indicate eutrophication with Chl-a values <500 µg/g. So, this study investigated the phosphate fluxes between sediment and water column and determined the factors influencing the RP fluxes in the inner bay of Izmir.

The 210Po and 210Pb levels in surface sediment samples in the Izmir Bay (Aegean Sea-Turkey).

Bottom sediments reflect in general the relative contamination of a sea area. Therefore, a great deal of monitoring work has been dedicated to the analysis of bottom sediments. Izmir Bay is a very important pollution centre in Turkish Aegean coast region due to a densely populated community, industrial complex and maritime transportation, and there are many streams flowing into the bay that pass through a number of industrial and agricultural areas. It had received the majority of domestic and industrial wastewaters until the wastewater treatment plant was constructed. It is well known that sediments play an important role as reservoirs of a fraction of the pollution in aquatic systems. Therefore, sediment samples were collected monthly from three stations which are located in the inner part of the bay during the period January to December 2003. Temporal variations and seasonal changes on their (210)Po and (210)Pb contents were examined, and the activity concentrations of (210)Po and (210)Pb were found to vary from 43+/-6 to 132+/-12 and 27+/-5 to 91+/-9 Bq kg(-1) dry wt, respectively. The highest values of those natural radionuclides were measured at Karsiyaka Station because of the current systems of the bay. Seasonally, the (210)Pb levels were found to increase during the winter time for all the stations.

Spatio-temporal variations of organic carbon and chlorophyll degradation products in the surficial sediments of Izmir Bay (Aegean Sea/Turkey).

The aim of this research is to determine the effects of Izmir Big Channel Waste Water Treatment Project on the sediment quality of Izmir Bay. Wastewater treatment improves the water quality. However, sediment does not respond to this treatment as fast as water column. Monitoring of bottom water and sediment quality is necessary for identification of the recovery of the whole ecosystem. For this purpose, bottom water and sediment samples were collected from three stations which are located in the middle and inner parts of the Izmir Bay on a monthly basis between January 2003 and December 2003. Values measured at stations ranged between; 0.54-12.82 microg/L for chlorophyll-a, 0.09-9.32 microg/L for phaeopigment, 0.05-1.91 mg/L for particulate organic carbon in bottom waters, 11.88-100.29 microg/g for chlorophyll degradation products and 1.12-5.39% for organic carbon in sediment samples. In conclusion, it was found that grazing activity explained carbon variations in sediment at station 2, but at station 1 and station 3 carbon variations in sediment were not related to autochthonous biological processes.

Nutrient dynamics between sediment and overlying water in the inner part of Izmir Bay, Eastern Aegean.

The nutrient flux experiments for the sediments of Inner Izmir Bay were performed for the first time during January 2004-August 2004. The flux rates ranged between -127.9 and 358.2 microg atN m(-2) day(-1) for NH(4) (+), -47.88 and 320.9 microg at N m(-2) day(-1) for NO(2) (-), -62.96 and 121.3 microg at N m(-2) day(-1) for NO(3) (-), -64.1 and 528 microg atP m(-2) day(-1) for reactive phosphate (RP) and between -168.44 and 284.19 microg at Si m(-2) day(-1) for reactive silicate (RSi). Negative values were obtained from core incubations in winter except for nitrite (flux from water to sediment). The positive flux in all the core incubations during spring and summer (except nitrite in August) at least revealed that the sediment might be partially anoxic and/or included H(2)S. The turnover times obtained from water column nutrient inventory and flux rates indicated that Si and NH(4) (+) possessed a rapid cycle in water column. It was argued that NO(3) (-) would be more influenced by the removal processes within the sediment, therefore the water column would provide an additional contribution to the N limitation and the short turnover time of RP could rapidly supply RP to the water column. The continuous increase of pore water nutrient concentrations from January to August does not explain whether this nutrient reserve attains the next year with higher background levels or it is released back to environment at the end of autumn.