Pathways of floating marine debris in Jakarta Bay, Indonesia.

Jakarta is the capital of Indonesia with a high population density, which affects the amount of waste generated. The waste that ends up in Jakarta Bay has become an environmental problem. Understanding the pathway of marine debris in the ocean is important to identify the mitigation strategies. Before this study, the pathways and sources of marine debris in Jakarta Bay were unknown. By using virtual floating marine debris particles in a high-resolution ocean model, the fate of marine debris based on the pathways of particles released in Jakarta Bay in both forward and backward tracking experiments was analyzed. It was found that most of the particles from Jakarta Bay flow toward the Indian Ocean in all seasons. They flow off through the Sunda Strait and reach the open Indian Ocean after a few weeks. With regard to the source location, most particles that end up in Jakarta Bay come from the north of Java Island locally and from the Gulf of Thailand, Sumatra, and Kalimantan coasts. The particles do not appear to vary significantly across all seasons and identifying the pathway of marine debris might be useful in pollution reduction.

Calcite encrustation in macro-algae Chara and its implication to the formation of carbonate-bound cadmium.

We studied the relationship between macro-algae Chara (Stoneworts) calcite (CaCO(3)) encrustation and the speciation of cadmium (Cd) accumulated by the plant. Results showed that 17% of the total Cd (0.3mgkg(-1)) accumulated by Chara fibrosa exposed to 1 microg Cd L(-1) was carbonate-bound. The percentage of carbonate-bound Cd in the plant exposed to 10 microg Cd L(-1) increased from 48% in young thalli (total Ca<50 mg g(-1), total Cd: 125 mg kg(-1)) to 63% in calcified mature thalli (total Ca: 190 mg g(-1); total Cd: 134 mg kg(-1)). Based on mineral saturation calculation and reliability analysis of the sequential fractionation procedure, precipitation of otavite (CdCO(3)) and co-precipitation of Cd with calcite, occurring in the alkaline regions of Chara cell wall, are probably the mechanisms of carbonate-bound Cd formation. Thick marl sediment frequently found beneath charophyte meadows suggests a long-term storage of Ca as well as the precipitated or co-precipitated Cd in the sediment after the plant senescence and decomposition.

Does calcite encrustation in Chara provide a phosphorus nutrient sink?

We studied the effect of calcite encrustation in stoneworts (Chara spp.) on P cycling in an aquatic ecosystem. Sequential fractionation was performed to quantify P fractions of the internodes of calcified (Ca-CF) and uncalcified (UCa-CF) Chara fibrosa Agardh ex Bruzelius. Our results showed that Ca-CF was able to store more P and about 14 to 23% of total P in Ca-CF was co-precipitated with encrusted calcite, while only 2 to 3% was found in UCa-CF. Furthermore, in Ca-CF, an increased amount of total P did not result in a higher release of bioavailable water-soluble and sodium hydroxide-extractable P. Extracellular calcification in Chara enhanced nutrient sink for P, provided a further bottom-up control of phytoplankton, and should be regarded as a positive feedback in stabilizing Chara dominance in lakes.