Diversity and composition of sulfate- and sulfite-reducing prokaryotes as affected by marine-freshwater gradient and sulfate availability.

Sulfate- and sulfite-reducing prokaryotes (SSRP) communities play a key role in both sulfur and carbon cycles. In estuarine ecosystems, sulfate concentrations change with tides and could be limited in tidal freshwater reach or deep sediments. In a subtropical estuary of northern Taiwan in December 2007, we examined the compositional changes of SSRP communities. We examined three sites: from the lower estuarine brackish-water reach (site GR and mangrove vegetation site, GM) to the upper estuarine tidal freshwater reach (site HR), as well as from surface to a 50-cm depth. The partial sequence of sulfite reductase (dsrB) genes was used as a molecular marker of SSRP, linked to polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE) techniques. SSRP communities of the DGGE profiles varied with sites according to one-way analyses of similarities (Global R = 0.69, P = 0.001). Using cluster analysis, the DGGE profile was found to show site-specific clusters and a distinct depth zonation (five, six, and two SSRP communities at the GM, GR, and HR sites, respectively). SSRP composition was highly correlated to the combination of salinity, reduced sulfur, and total organic carbon contents (BIO-ENV analysis, r ( s ) = 0.56). After analyzing a total of 35 dsrB sequences in the DGGE gel, six groups with 15 phylotypes were found, which were closely related to marine-freshwater gradient. Moreover, sequences neighboring sulfite-reducing prokaryotes were observed, in addition to those affiliated to sulfate-reducing prokaryotes. Four phylotypes harvested in HR resembled the genus Desulfitobacterium, a sulfite-reducing prokaryote, which failed to use sulfate as an electron acceptor and were active in freshwater and sulfate-limited habitat. The other five phylotypes in the HR reach belonged to the sulfate-reducing prokaryotes of the genera Desulfatiferula, Desulfosarcina, Desulfovibrio, and Desulfotomaculum, which appeared to tolerate low salinity and low sulfate supply. SSRP phylotypes at the mangrove-vegetated GM site (five phylotypes in two groups) were phylogenetically less diverse, when compared with those at the non-mangrove-vegetated GR site (three phylotypes in three groups) and the tidally influenced freshwater HR site (nine phylotypes in five groups). Phylotypes found at GR and GM were all affiliated to marine sulfate-reducing prokaryote strains of the genera Desulfofaba, Desulfobotulus, Desulfatiferula, Desulfosarcina, and Desulfotomaculum. Notably, a phylotype recorded in the surface sediment at GR resembled the genus Desulfobulbus, which was recorded from freshwater environment consisting of the freshwater input at GR during ebb tides.

Population subdivision of the tri-spine horseshoe crab, Tachypleus tridentatus, in Taiwan Strait.

The genetic structure of the Asian tri-spine horseshoe crab, Tachypleus tridentatus, was investigated in three populations of Taiwan Strait using mitochondrial (mt) AT-rich region DNA sequences. We examined 23 individuals from Kinmen, an island located on the western side of Taiwan Strait, and 12 each from Tiexianwei and Dongwei near Magong Island in the Penghu Archipelago, in the middle of Taiwan Strait. DNA sequence analysis of 369 base pairs (bp) of the mt AT-rich region revealed 10 haplotypes among the 47 individuals, with a mean haplotypic diversity (h) of 0.626+/-0.075 and nucleotide diversity (pi) of 0.0039+/-0.00055. Pairwise F-statistics (F(ST)) revealed significantly high gene flow between Kinmen and Dongwei (F(ST)=-0.0351, p>0.05, N(e)m=infinity), but marked population subdivision and restricted gene flow between Kinmen and Tiexianwei (F(ST)=0.1382, p<0.05, N(e)m=3.1176). Between populations at Magong Island, gene flow was moderate (F(ST)=0.0634, p>0.05, N(e)m=7.3913). Mismatch distribution analysis indicated that the relatively low haplotype and nucleotide diversity observed in the Tiexianwei T. tridentatus population can be attributed to a recent bottleneck, probably due to isolation of Tiexianwei in semi-closed Magong Bay that prevents gene flow from neighboring populations.

Relationships between pesticides and organic carbon fractions in sediments of the Danshui River estuary and adjacent coastal areas of Taiwan.

In order to understand the fate of pesticides in marine environments, concentrations of pesticides and different carbonaceous fractions were determined for surface sediments in the Danshui River and nearby coastal areas of Taiwan. The major compounds detected were tetrachlorobenzene, HCHs, chlordane, aldrin, DDDs, DDEs and DDTs. Total concentrations of pesticides in the sediments ranged from not detectable to 23 ng g(-1), with the maximum value detected near the discharge point of the marine outfall from the Pali sewage treatment plant. These results confirm that pesticides persist in estuarine and nearby coastal environments of the Danshui River well after their ban. Concentrations of total pesticides significantly correlate with concentrations of total organic carbon and black carbon in these sediments, suggesting that total organic carbon and black carbon regulate the distribution of trace organic pollutants in fluvial and coastal marine sediments.

A trophic model for the Danshuei River Estuary, a hypoxic estuary in northern Taiwan.

The estuary of the Danshuei River, a hypoxic subtropical estuary, receives a high rate of untreated sewage effluent. The Ecopath with Ecosim software system was used to construct a mass-balanced trophic model for the estuary, and network analysis was used to characterize the structure and matter flow in the food web. The estuary model was comprised of 16 compartments, and the trophic levels varied from 1.0 for primary producers and detritus to 3.0 for carnivorous and piscivorous fishes. The large organic nutrient loading from the upper reaches has resulted in detritivory being more important than herbivory in the food web. The food-chain length of the estuary was relatively short when compared with other tropical/subtropical coastal systems. The shortness of food-chain length in the estuary could be attributed to the low biomass of the top predators. Consequently, the trophic efficiencies declined sharply for higher trophic levels due to low fractions of flows to the top predators and then high fractions to detritus. The low biomass of the top predators in the estuary was likely subject to over-exploitation and/or hypoxic water. Summation of individual rate measurements for primary production and respiration yielded an estimate of -1791 g WW m(-2) year(-1), or -95 g C m(-2) year(-1), suggesting a heterotrophic ecosystem, which implies that more organic matter was consumed than was produced in the estuary.

Relationship between carbonaceous materials and polychlorinated biphenyls (PCBs) in the sediments of the Danshui River and adjacent coastal areas, Taiwan.

Persistent organic pollutants, POPs (e.g., polychlorinated biphenyls) can seriously and deleteriously affect environmental quality and human health. These organic pollutants are exhibiting high affinities to solid phases and thus, quickly end up in sediments. To better understand the role of carbonaceous materials in the transport and distributions of POPs in terrestrial and near-shore environments, concentrations of PCBs and carbonaceous materials (including total organic carbon, black carbon and total carbohydrates), were determined in surface sediments of the Danshui River and nearby coastal areas, Taiwan. Total concentrations of PCBs in the sediments ranged from non-detectable to 83.9 ngg(-1), dry weight, with the maximum value detected near the discharge point of the marine outfall from the Pali Sewage Treatment Plant. These results suggest that the sewage treatment plant has discharged PCBs in the past and the concentrations are still high due to their persistence; alternatively, PCBs are still being discharged in the estuarine and near-shore environment of the Danshui River. Organic carbon and black carbon concentrations correlated well with those of total PCBs in the sediments, suggesting that both organic carbon and black carbon significantly affect the distribution of trace organic pollutants through either post-depositional adsorption, or by co-transport of similar source materials. The field results demonstrate that black carbon and plays an important role in the general distribution of PCBs, while concentrations of some specific PCBs are affected by both black carbon and organic carbon concentrations.

Trophic structure and functioning in a eutrophic and poorly flushed lagoon in southwestern Taiwan.

Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web.

An ecosystem-service approach to evaluate the role of non-native species in urbanized wetlands.

Natural wetlands have been increasingly transformed into urbanized ecosystems commonly colonized by stress-tolerant non-native species. Although non-native species present numerous threats to natural ecosystems, some could provide important benefits to urbanized ecosystems. This study investigated the extent of colonization by non-native fish and bird species of three urbanized wetlands in subtropical Taiwan. Using literature data the role of each non-native species in the urbanized wetland was evaluated by their effect (benefits/damages) on ecosystem services (ES) based on their ecological traits. Our sites were seriously colonized by non-native fishes (39%-100%), but <3% by non-native birds. Although most non-native species could damage ES regulation (disease control and wastewater purification), some could be beneficial to the urbanized wetland ES. Our results indicated the importance of non-native fishes in supporting ES by serving as food source to fish-eating waterbirds (native, and migratory species) due to their high abundance, particularly for Oreochromis spp. However, all non-native birds are regarded as "harmful" species causing important ecosystem disservices, and thus eradication of these bird-invaders from urban wetlands would be needed. This simple framework for role evaluation of non-native species represents a holistic and transferable approach to facilitate decision making on management priority of non-native species in urbanized wetlands.

Ecosystem Functions Connecting Contributions from Ecosystem Services to Human Wellbeing in a Mangrove System in Northern Taiwan.

The present study examined a mangrove ecosystem in northern Taiwan to determine how the various components of ecosystem function, ecosystem services and human wellbeing are connected. The overall contributions of mangrove services to specific components of human wellbeing were also assessed. A network was developed and evaluated by an expert panel consisting of hydrologists, ecologists, and experts in the field of culture, landscape or architecture. The results showed that supporting habitats was the most important function to human wellbeing, while water quality, habitable climate, air quality, recreational opportunities, and knowledge systems were services that were strongly linked to human welfare. Security of continuous supply of services appeared to be the key to a comfortable life. From a bottom-up and top-down perspective, knowledge systems (a service) were most supported by ecosystem functions, while the security of continuous supply of services (wellbeing) had affected the most services. In addition, the overall benefits of mangrove services to human prosperity concentrated on mental health, security of continuous supply of services, and physical health.

Nucleotide sequences of ribosomal internal transcribed spacers and their utility in distinguishing closely related Perinereis polychaets (Annelida; Polychaeta; Nereididae).

Nucleotide sequences of a segment of the rRNA transcription unit spanning from the 3' end of the 18S rDNA to the 5' end of 28S rDNA were determined for four species of Perinereis polychaetes: P. aibuhitensis, P. floridana, and two undescribed species, Perinereis sp1 and sp2. The 5.8S rDNA sequences are identical among the four species. Intraspecific variability was low with the Kimura 2-parameter (K2P) distance, ranging from 0 to 0.0138 for ITS1 and 0 to 0.0247 for ITS2. The interspecific nucleotide difference was significantly higher than those within species, with a mean K2P of 0.172 for ITS1 and 0.204 for ITS2, suggesting that comparisons of ITS regions can be used to evaluate the phylogenetic relationships among Perinereis species. Both neighbor-joining and parsimony analyses of ITS variability indicate a close relationship between the two undescribed species of Perinereis. These findings highlight the utility of the ITS sequence in conjunction with other morphological and ecological characters to delineate species boundaries among closely related polychaetes.

Tungsten and other heavy metal contamination in aquatic environments receiving wastewater from semiconductor manufacturing.

Through analyses of water and sediments, we investigate tungsten and 14 other heavy metals in a stream receiving treated effluents from a semiconductor manufacturer-clustered science park in Taiwan. Treated effluents account for ∼ 50% of total annual river discharge and <1% of total sediment discharge. Dissolved tungsten concentrations in the effluents abnormally reach 400 µg/L, as compared to the world river average concentration of <0.1 µg/L. Particulate tungsten concentrations are up to 300 µg/g in suspended and deposited sediments, and the corresponding enrichment factors are three orders of magnitude higher than average crust composition. Surprisingly, the estimated amount of tungsten exported to the adjacent ocean is 23.5 t/yr, which can approximate the amount from the Yangtze River should it be unpolluted. This study highlights the urgency of investigating the biological effect of such contamination.

Effects of semidiurnal tidal circulation on the distribution of holo- and meroplankton in a subtropical estuary.

We examined how tidal changes and which physical factors affected holo- and meroplankton assemblages in a subtropical estuary in Taiwan in February 1999. A factor analysis showed that during tidal flooding, the water mass properties changed from low salinity (5-16) and high particulate organic carbon (POC, 2.6-4.5 mg L(-1)) content to increasing salinity and high total suspended matter content (29.0-104.5 mg L(-1)). With a receding tide, the water became more saline again, and its velocity increased (from non-detectable to 0.67 m s(-1)). One-way ANOVA showed that the distributions of four dominant taxa were affected by the ebb tide and exhibited two distinct groups. The first group consisted of non-motile invertebrate eggs and weakly swimming polychaete sabellid embryos and larvae (at densities of 1.25-1.40 ind. L(-1)), while the second consisted of better-swimming copepods and polychaete spionid larvae (at densities of 0.70-1.65 ind. L(-1)). A canonical correlation analysis demonstrated that the former group occurred at sites with greater freshwater input, higher POC content and greater depth, whereas the latter group was significantly associated with sites subject to seawater and faster flows. We propose that a two-layered circulation process and tidally induced oscillations in water movements might account for the distributional differences between these two groups.

Isolation and characteristics of 10 microsatellite markers from the endangered coconut crab (Birgus latro).

The coconut crab (Birgus latro), an endangered marine-dispersed crustacean, is facing severe and probably accelerating population extinction worldwide, but biological information on its conservation remains deficient. In order to reveal the genetic structure of B. latro, 10 microsatellite loci were developed. A high degree of polymorphism was observed with a mean number of alleles per locus of 16.9. The mean expected heterozygosities were also high, ranging from 0.742 to 0.965. The observed heterozygosities ranged from 0.210 to 0.925. Departures from Hardy-Weinberg equilibrium were observed at five loci after the Bonferroni correction. These hypervariable markers will be utilized to study the genetic diversity and conservation of B. latro throughout its distribution range in the Pacific and Indian Oceans.