Evolution and dynamics of tropical river plumes in the Great Barrier Reef: An integrated remote sensing and in situ study

[1] The short-lived but intense discharge of freshwater from tropical rivers into the Great Barrier Reef (GBR) Lagoon and the associated salinity reductions are a critical consideration in marine research and management of the ecologically sensitive GBR World Heritage Area. Salinity provides a unique tracer that gives clues to the origin of river-borne contaminants and allows the influences of storm-induced resuspension and river discharge on turbidity to be clearly distinguished. We describe a field investigation of the evolution and dynamics of the Herbert River plume in the central GBR. Its primary goals were to use an airborne salinity mapper and in situ instruments to study the three-dimensional structure and evolution of the plume and to lay a foundation for numerical modeling studies of its dynamics. The aircraft surveys provided a rapid assessment of the plumes spatial extent, while the in situ data revealed details of its subsurface structure. The Herbert River plume was produced by heavy rainfall associated with tropical storms during the La Nina-dominated 1999/2000 monsoon season. In the near field, the surface expression of the plume boundaries was indicated by sharp color and salinity fronts that were clearly visible from the air and sea surface. In the far field and middle Lagoon, the plume was more dispersed and ultimately merged with the larger-scale salinity gradients and with the remnant plume of the more distant, and larger, Burdekin River. The plume location and structure evolved in response to changing river flows, tidal and subtidal circulation, and wind. Using Garvine\u27s Kelvin number-based scheme, the plume was classified as intermediate in dynamical character and thus is subject to a variety of forcings. The plume evolved in response to changes in the relative intensity of tidal currents and low-frequency circulation due to wind and western boundary current forcing. It also displayed a characteristic hook-shaped\u27\u27 structure, which has been identified previously in numerical plume model studies. This structure appeared in the presence of accelerating along-shelf current flow and horizontal shear and it indicates that the plume circulation had a strongly three-dimensional character. The approach demonstrates the efficacy of combining airborne and in situ methods to observe rapidly evolving coastal salinity structure and dynamics and sets the stage for future satellite-borne studies of larger-scale features showing contrasting salinity distributions

NANS-mediated synthesis of sialic acid is required for brain and skeletal development

We identified biallelic mutations in NANS, the gene encoding the synthase for N-acetylneuraminic acid (NeuNAc; sialic acid), in nine individuals with infantile-onset severe developmental delay and skeletal dysplasia. Patient body fluids showed an elevation in N-acetyl-D-mannosamine levels, and patient-derived fibroblasts had reduced NANS activity and were unable to incorporate sialic acid precursors into sialylated glycoproteins. Knockdown of nansa in zebrafish embryos resulted in abnormal skeletal development, and exogenously added sialic acid partially rescued the skeletal phenotype. Thus, NANS-mediated synthesis of sialic acid is required for early brain development and skeletal growth. Normal sialylation of plasma proteins was observed in spite of NANS deficiency. Exploration of endogenous synthesis, nutritional absorption, and rescue pathways for sialic acid in different tissues and developmental phases is warranted to design therapeutic strategies to counteract NANS deficiency and to shed light on sialic acid metabolism and its implications for human nutrition