Rainfall effect on sediment and nutrient fluxes in a small mangrove river, Okinawa, Japan

To understand the effect of rainfall on sediment and nutrient fluxes in a mangrove river ecosystem, field observations were conducted in the Fukido River, Okinawa, Japan. Water currents and water quality parameters (salinity and turbidity) were measured at the river mouth and upstream, and surface water samples were analyzed for nutrient concentrations (NO3-N, NH4-N, PO4-P, SiO2-Si, suspended solids [SS], total nitrogen [TN], and total phosphorus [TP]). Observations were conducted on both clear and rainy days, which revealed the effect of weather. SS flux at the river mouth (outflux to sea) and upstream (influx from land) showed that sediment deposition occurred in the mangrove swamp, and the amount of sediment deposition on a rainy day (324 kg d–1) was approximately 14 times greater than that on a clear day (24 kg d–1). The higher influx from upstream on the rainy day caused levels of TN and TP deposition in the mangrove swamp that were 9.1 and 3.4 times higher, respectively, than levels on a clear day. Our findings highlight the importance of considering local weather conditions in the estimation and management of nutrient budgets, especially in a small mangrove river

Changes in sedimentary environments in Shihwa Lake, Korea

Shihwa Lake was an artificial freshwater lake formed in 1994 by constructing a 12.7-km-long seawall, but it became a seawater lake in 1997. The water quality of Shihwa Lake had not been recovered despite the seawater exchange through the drain gate. This may adversely affect not only the water but also the bottom sediment environment of the lake. To determine the possible reasons for the environmental deterioration, water and core samples from three points in the lake were collected. And the parameters, such as the water temperature, salinity, dissolved oxygen (DO), particle distribution, total carbon (TC) and total nitrogen (TN), C/N ratio, and radioactive strength, were measured to estimate the water and sediment quality. In addition, we investigated changes in the sedimentation environment based on heavy-metal analysis, stable-isotope analysis of the core sample, and numerical analysis of sand transport. The core-sample analysis revealed a change in the sedimentation process on a time basis (before, during, and after the construction of the seawall). As a result, the sedimentation rate was approximately 4 cm/year during the seawall construction and 2 cm/year after the construction near the center of the lake. Furthermore, we established that the trends in these calculated sedimentation rates, determined using the radioactive strength method, align consistently with the results obtained from simulations and ultrasonic-wave observations. Finally, we evaluated the effects of a tidal power plant on the exchange of seawater and sedimentation processes

Diffuse Sclerosing Variant of Papillary Thyroid Carcinoma : A Case Report

We present a rare case of a 26-year old woman with diffuse sclerosing variant of papillary thyroid carcinoma. The patient was referred to our hospital with diffuse enlargement of the thyroid accompanied with palpable bilateral cervical lymph nodes. Ultrasonography showed a heterogeneous pattern with ill-defined hypoechoic areas in both thyroid lobes. There were multiple small punctate echogenic foci. Fine-needle aspiration cytology revealed typical signs of papillary carcinoma. The patient underwent a total thyroidectomy using a bilateral modified neck dissection. Pathological findings demonstrated diffuse involvement and continuous infiltration of the tumors to both thyroid lobes, lymph nodes and cervical soft tissue. Postoperatively, 100 mCi of 131I was administrated to the small amount of residual thyroid tissue. The patient is free from recurrence one year after the operation