Carbon fluxes from a mangrove creek with adjacent seagrass meadows and coral reefs (at 4 km from the creek) were investigated in Gazi Bay (Kenya). Analysis of the stable isotope signature of sediment carbon in the seagrass zone and data on the sediment carbon content indicate that outwelling of particulate organic matter (POM) from the mangrove forest occurs, but that deposition of this POM rapidly decreases away from the forest. No evidence for any input of mangrove POM in the seagrass zone was found at a distance of 3 km from the mangrove creek, near the reefs. The gradient in sediment 6I3C values in the seagrass zone was paralleled by a similar gradient of 6I3C values in Thalassodendron ciliatum, the dominant subtidal seagrass. This gradient probably reflects the availability of respiratory CO2 denved from mangrove POM as a carbon source for the seagrass. Analysis of C:N ratios of particulate material (< 1 mm) collected with sediment traps in the seagrass zone yielded values ranging from 8.5 to 11.2. This range is remarkably low compared to C:N ratios of plant matenal produced in the mangrove forest, and suggests that some of the mangrove-derived organic particles deposited in the seagrass zone have gone through a phase of intensive processing. During flood tides conspicuous decreases were found in 6I3C values of seston flowing over the seagrass zone, coinciding with significant increases in the carbon content of the seston. These findings point to a reversed flux of organic particles from the seagrass zone to the mangrove forest. Our data indicate that, as far as POM fluxes are concerned, the mangrove forest and adjacent seagrass meadows are tightly coupled, but that the nearby coral reefs may exist in relative isolation.

Abstract. The biogeochemistry of mangrove sediments was investigated in several mangrove forest communities in Gazi Bay, a coastal lagoon in Kenya, Africa. Carbon dioxide fluxes, sediment median grain sizes, sedimentary organic carbon, nitrogen and phosphorus contents and pore-water characteristics (ammonium, nitrate, sulfate and chloride) could be related to forest type. Mangrove sediments have pH values that range from 3.5 to 8.3 due to the limited buffer capacity of these sediments and intense acidifying processes such as aerobic degradation of organic matter, oxidation of reduced components, ammonium uptake by roots and root respiration. The mangrove sediments are nitrogen-rich compared to mangrove litter, as a result of microbial nitrogen retention, uptake and fixation, and import of nitrogen-rich material. It appears that mangrove sediments in Gazi Bay act as a nutrient and carbon sink rather than as a source for adjacent seagrass and reef ecosystems.

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Charcot neuro-osteoarthropathy is a significant problem with a rapid devastating nature. If not recognized it may lead to progressive foot deformity, ulceration or osteomyelitis, or eventually to amputation. The diagnosis is challenging, and imaging plays a pivotal role. Rapid and accurate diagnosis and early intervention is important to prevent progressive and destructive Charcot deformity of the foot. The imaging workup of the warm swollen Charcot foot is presented. The advantages and disadvantages of different imaging modalities are discussed. This review provides the consulting radiologists with tools to cautiously differentiate Charcot's neuro-osteoarthropathy from osteomyelitis. It is crucial to look beyond radiological features and integrate the location of pathology and presence of ulcer in the reading process. Because imaging plays a pivotal role in arriving at the definitive diagnosis and adequate treatment, the radiologist "makes the difference"-can be a friend or a foe.