Dissolved inorganic phosphorus (DIP) concentrations in the oligotrophic surface waters of the South China Sea decrease from ∼20 nM in March 2000 to ∼5 nM in July 2000, in response to seasonal water column stratification. These minimum DIP concentrations are one order of magnitude higher than those in the P‐limited, iron‐replete stratified surface waters of the western North Atlantic, suggesting that the ecosystem in the South China Sea may be limited by bioavailable nitrogen or some trace nutrient rather than DIP. Nutrient enrichment experiments using either nitrate, phosphate or both indicate that nitrogen limits the net growth of phytoplankton in the South China Sea, at least during March and July 2000. The fixed nitrogen limitation may result from the excess phosphate (N:P<16) transported into the South China Sea from the North Pacific relative to microbial population needs, or from iron control of nitrogen fixation. The iron‐limited nitrogen fixation hypothesis is supported by the observation of low population densities of Trichodesmium spp. (<48 × 103 trichomes/m3), the putative N2 fixing cyanobacterium, and with low concentrations of dissolved iron (∼0.2–0.3 nM) in the South China Sea surface water. Our results suggest that nitrogen fixation can be limited by available iron even in regions with a high rate of atmospheric dust deposition such as in the South China Sea.

Up to 2 μM of nitrate anomaly, N*, were found in the upper nutricline at the South East Asia Time‐series Study (SEATS) site in the northern South China Sea (SCS). These concentrations were among the higher values reported in the Pacific and indicate the significant contribution of the remineralization of nitrogen‐rich organic matter formed by nitrogen fixation to the nutrient dynamics of the area. The concentrations were systematically higher, by up to 2.5 μM, in the Fall through the early Spring, during the northeast monsoon, than in the Summer, suggesting that the impact of nitrogen fixation was higher during the former time period. This pattern is in phase with that of the atmospheric deposition of Asian dust to the northern SCS. The coherence is consistent with a coupling between nitrogen fixation and the availability of atmospherically derived iron.

We report the elemental composition (P, Si, Al, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) in the size-fractionated plankton and suspended particulate matter (SPM) in the surface waters of the South China Sea. The sizefractionated plankton were effectively and gently separated by gravity through a novel trace-metal-clean filtration device, equipped with 150-, 60-, and 10-mm aperture nets in sequence to concentrate the plankton. P-normalized metal quotas in the largest fraction, mostly composed of copepods, were close to or slightly lower than the average metal quotas obtained from previous field studies. However, the total metal quotas in the two smaller fractions were 8-to 40-fold higher than the largest one, and they increased with decreasing sizes. The striking correlation between some essential metals and chlorophyll (Chl) in the SPM at the offshore site indicates that the majority of the metals were associated with algae. Nevertheless, the P-normalized metal quotas also showed positive correlations with abiogenic Al and Mn, indicating that most of the metals associated with phytoplankton were from extracellular inorganic particles. Preliminary evidence suggests that the extracellular metals were originally derived from anthropogenic aerosols, which contain abundant dissolvable trace metals. The metal quotas of the zooplankton assemblages have a fairly consistent value as compared to observations from other regions, but algae larger than 10 mm carry overwhelming amounts of extracellular metals even in offshore areas. The stoichiometry concept for trace-metal composition in marine plankton assemblages is unrealistic in the field.Particles, including both biogenic and abiogenic, play a vital role in controlling trace-metal distribution and cycling in the ocean (Turekian 1977;Whitfield and Turner 1987;Li 1991). In particular, the cycling of many biologically essential trace metals is driven and transformed by biogenic particles generated in the euphotic zones (Collier and Edmond 1984;Bruland et al. 1994). Biogenic particles in oceanic surface waters, mainly composed of diverse phytoplankton and zooplankton, interact with dissolved and particulate trace metals in ambient seawater through various processes, including active biological uptake, adsorption-desorption, zooplankton grazing and repackaging, particle aggregation, microbial decomposition, and so on. In terms of vertical cycling, large biogenic particles, mostly composed of sizable plankton, such as large diatom, zooplankton, and their hard parts and detritus (Alldredge and Silver 1988), serve as the predominant components of sinking particles and thus are principal agents in transporting both major and trace elements from oceanic surface waters to the deep waters (Bruland 1983;Fowler and Knauer 1986;Alldredge and Jackson 1995). The trace-metal composition in large-sized marine plankton assemblages may thus provide fundamental information for further studies and help models of the cycling processes of trace metals in marine water columns (e.g., Martin an...

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the important antibiotic resistant pathogens causing infections in humans and animals. The increasing observation of MRSA in wildlife species has raised the concern of its impact on animal health and the potential of zoonotic transmission. This study investigated the prevalence of S. aureus in fecal samples from non-human primates in a zoo located in Jiangsu, China, in which 6 out of 31 (19.4%) fecal samples, and 2 out of 14 (14.3%) indoor room floor swab samples were S. aureus-positive. The antibiotic susceptibility tests of the eight isolates showed that the two isolates were resistant to both penicillin and cefoxitin, the three isolates were resistant only to penicillin, while three isolates were susceptible to all detected antibiotics. The two isolates resistant to cefoxitin were further identified as MRSA by the presence of mecA. Five different spa types were identified including t034 of two MRSA isolates from Trachypithecus francoisi, t189 of two methicillin-susceptible S. aureus (MSSA) isolates from Rhinopithecus roxellana, t377 of two MSSA isolates from Colobus guereza, and two novel spa types t19488 and t19499 from Papio anubis. Whole genome sequencing analysis showed that MRSA t034 isolates belonged to ST398 clustered in clonal complex 398 (CC398) and carried the type B ΦSa3 prophage. The phylogenetic analysis showed that the two MRSA t034/ST398 isolates were closely related to the human-associated MSSA in China. Moreover, two MRSA isolates contained the virulence genes relating to the cell adherence, biofilm formation, toxins, and the human-associated immune evasion cluster, which indicated the potential of bidirectional transfer of MRSA between monkeys and humans. This study is the first to report MRSA CC398 from monkey feces in China, indicating that MRSA CC398 could colonize in monkey and have the risk of transmission between humans and monkeys.

Here, we investigated the diagnostic performance of manganese (Mn)-enhanced magnetic resonance imaging (MEMRI) in colorectal cancer (CRC). The ability of CRC cell lines SW620 and SW480 to uptake Mn was evaluated and compared with a normal colon cell using MEMRI. Subcutaneous xenografts in nude mice underwent MRI examination at tumor sizes of 5, 10, and 15 mm. Contrast enhancement was compared between gadolinium (Gd)- and Mn-enhanced MRI. SW620 and SW480 cell lines took up more Mn2+ than normal cells, resulting in 4.5 and 2 times greater T1 value shortening than normal cell using in vitro MEMRI (P < .001). Most xenografts (17/23) enhanced markedly on MEMRI. A heterogeneous enhancement pattern invariably noted whether Mn or Gd agents were administered, but tumors imaged using MEMRI showed a greater degree of enhancement with a larger extent of enhanced area than those imaged using Gd-enhanced MRI. The numbers of markedly Mn-enhanced cases were more in the 5-mm-size tumor group than in 10- or 15-mm-size tumor groups. Overall, MEMRI could enhance CRCs and it showed potential in detecting early small lesions and markedly enhancing tumors that had minimal Gd enhancement.