Abstract. Nutrient dynamics based on field observations made along the eastern Hainan Island during the period 2006–2009 were investigated to understand nutrient biogeochemical processes, and to provide an overview of human perturbations of coastal ecosystems in this tropical region. The rivers showed seasonal variations in nutrient concentrations, with enrichment of dissolved inorganic nitrogen and dissolved silicate, and depletion of PO43−. High riverine concentrations of nitrate mainly originated from agricultural fertilizer inputs. The DIN : PO43− ratios ranged from 37 to 1063, suggesting preferential depletion of PO43− relative to nitrogen in rivers. Chemical weathering in the drainage area might explain the high levels of dissolved silicate. Aquaculture ponds contained high concentrations of NH4+ and dissolved organic nitrogen. The particulate phosphorus concentrations in the study area were lower than those reported for estuaries worldwide. The particulate silicate levels in rivers and lagoons were lower than the global average level. Nutrient biogeochemistry in coastal areas was affected by human activities (e.g., aquaculture, agriculture), and by natural phenomena including typhoons. The nutrient concentrations in coastal waters were low because of dispersion of land-derived nutrients in the sea. Nutrient budgets were built based on a steady-state box model, which showed that riverine fluxes are magnified by estuarine processes (e.g., regeneration, desorption) in estuaries and Laoyehai Lagoon, but not in Xiaohai Lagoon. Riverine and groundwater inputs were the major sources of nutrients to Xiaohai and Laoyehai lagoons, respectively, and riverine inputs and aquaculture effluents were the major sources for the eastern coast of Hainan Island. Nutrient inputs to the coastal ecosystem increased with typhoon-induced runoff of rainwater, elucidating the important influence of typhoons on small tropical rivers.

Source/description: The Pacific oyster (Crassostrea gigas) is a widely cultivated aquatic species with an annual world production of 4.6 millions metric tons in 2006. 1 To improve the increasingly valuable Pacific oyster industry, genetic improvement programmes have been initiated in several countries, and to date two preliminary genetic linkage maps have been developed. 2,3 Higher density maps, required for quantitative trait locus or genome scan studies, rely on the development of SNPs (single nucleotide polymorphisms). Here we report the first set of polymorphic SNP markers by tetra-primer ARMS-PCR method. 4 SNP identification: Polymorphic sites were identified from expressed sequence tags (ESTs) of C. gigas. A total of 29 000 EST sequences of C. gigas were downloaded from GenBank (8 July 2008). ESTs were assembled and the contigs that contained four or more sequences were identified to search for potential SNPs. A single-base mutation that occurred in two or more ESTs and that was surrounded by good flanking sequences was identified as a potential SNP. Sequences containing SNPs were annotated using the BLAST software, and sequence homology was accepted based on a cut-off E-value of 1.0 · 10 )6 . Fifty-one candidate SNPs were selected for tetra-primer ARMS-PCR primer design and optimization (Appendix S1). Primers were designed using BATCHPRIMER3. 5 Locus genotyping and data analysis: Polymorphism was evaluated in 30 individuals of the wild Weihai population (WH) collected in 2004 and 30 individuals of the cultured Lianyungang population (LYG) collected in 2005, which are about 500 km apart. The LYG population was cultured on stone pilings in intertidal areas for about 1 year. The data were analysed using POPGENE 1.32. 6 Of the 51 potential SNP makers, 27 were not easily amplified, four were monomorphic and 20 were found to be polymorphic. All loci had two alleles and the minor allele frequency ranged from 0.033 to 0.467 in WH, and from 0.033 to 0.367 in LYG (Table S1). The observed and expected heterozygosities in WH ranged from 0.067 to 0.800 and from 0.064 to 0.500, while those in LYG ranged from 0.067 to 0.733 and from 0.064 to 0.464 respectively. LD was not found, but significant deviation from HWE was observed at the same two loci in both populations after Bonferroni correction (P < 0.05). The development of polymorphic SNP markers will be useful for mapping studies, population genetics and marker-assisted breeding in C. gigas.