Solving the coastal eutrophication problem by large scale seaweed cultivation

Eutrophication is becoming a serious problem in coastal waters in many parts of the world. It induces the phytoplankton blooms including 'Red Tides', followed by heavy economic losses to extensive aquaculture area. Some cultivated seaweeds have very high productivity and could absorb large quantities of N, P, CO2, produce large amount of O-2 and have excellent effect on decreasing eutrophication. The author believes that seaweed cultivation in large scale should be a good solution to the eutrophication problem in coastal waters. To put this idea into practice, four conditions should be fulfilled: (a) Large-scale cultivation could be conducted within the region experiencing eutrophication. (b) Fundamental scientific and technological problems for cultivation should have been solved. (c) Cultivation should not impose any harmful ecological effects. (d) Cultivation must be economically feasible and profitable. In northern China, large-scale cultivation of Laminaria japonica Aresch. has been encouraged for years to balance the negative effects from scallop cultivation. Preliminary research in recent years has shown that Gracilaria lemaneiformis (Bory) Daws. and Porphyra haitanensis Chang et Zheng are the two best candidates for this purpose along the Chinese southeast to southern coast from Fujian to Guangdong, Guangxi and Hong Kong. Gracilaria tenuistipitata var. liui Chang et Xia is promising for use in pond culture condition with shrimps and fish.

Diverse tetracycline resistant bacteria and resistance genes from coastal waters of Jiaozhou Bay

Environmental microbiology investigation was carried out in Jiaozhou Bay to determine the source and distribution of tetracycline-resistant bacteria and their resistance mechanisms. At least 25 species or the equivalent molecular phylogenetic taxa in 16 genera of resistant bacteria could be identified based on 16S ribosomal deoxyribonucleic acid sequence analysis. Enterobacteriaceae, Pseudomonadaceae, and Vibrionaceae constituted the majority of the typical resistant isolates. Indigenous estuarine and marine Halomonadaceae, Pseudoalteromonadaceae, Rhodobacteraceae, and Shewanellaceae bacteria also harbored tetracycline resistance. All the six resistance determinants screened, tet(A)-(E) and tet(G), could be detected, and the predominant genes were tet(A), tet(B), and tet(G). Both anthropogenic activity-related and indigenous estuarine or coastal bacteria might contribute to the tet gene reservoir, and resistant bacteria and their molecular determinants may serve as bioindicators of coastal environmental quality. Our work probably is the first identification of tet(E) in Proteus, tet(G) in Acinetobacter, tet(C) and tet(D) in Halomonas, tet(D) and tet(G) in Shewanella, and tet(B), tet(C), tet(E), and tet(G) in Roseobacter.

The dominant Ulva strain of the 2008 green algal bloom in the Yellow Sea was not detected in the coastal waters of Qingdao in the following winter

The region of Qingdao, China, experienced the world's largest green tide from May to July 2008. More than one million tons of fresh algal biomass of the green alga Ulva prolifera was harvested, while more was suspected to have sunk to the bottom. The original source of this seaweed was suspected to be from the south as revealed by satellite images. The floating biomass drifted with the water current northward and flourished in nearshore waters around Qingdao. However, direct biological evidence for "seed" source is lacking. It is still unclear whether this alga could survive the Qingdao local coastal environment and pose future danger of potential blooming. Systematic and seasonal sampling of waters in the intertidal zone at six collection sites along the Qingdao coast was conducted from December 2008 to April 2009. Forty-eight water samples were analyzed. From these, nine different morphotypes of Ulva were grown in the laboratory under standard temperature and light regimes. Growth of Ulva was observed in all water samples. However, molecular phylogenetic analyses revealed that the dominant U. prolifera strain of the 2008 bloom was absent in all the water-derived cultures during the sampling period. These results provide evidence that the dominant bloom-forming alga was unlikely able to survive the coastal waters (the minimal surface water temperature in February is 2A degrees C) in winter conditions in Qingdao, even though all the sampling locations were heavily covered by this alga in June 2008.

Growth of Gracilaria lemaneiformis under different cultivation conditions and its effects on nutrient removal in Chinese coastal waters

Gracilaria lemaneiformis (Bory) Daws has been extensively cultivated as a source of commercial agar and the ecomaterials in Shenao Bay, Guangdong Province, Jiaozhou Bay, Shandong Province and other waters in China. This paper examines the in situ suspended farming of G. lemaneiformis using raft cultivation under different conditions and its effects on nutrient removal in the laboratory. The results showed that cultivated Gracilaria grew well in both Shenao Bay and Jiaozhou Bay. The biomass of Gracilaria increased from 50 to 775 g m(-1) (fresh weight) during 28 days, with special growth rate (SPG) 13.9% d(-1) under horizontal cultivation in Jiaozhou Bay. Light, temperature, nutrient supply, as well as cultivation treatments such as initial density, and depth of suspension seaweed were important to the growth of Gracilaria. The highest biomass production was observed in the horizontal culture condition (0.0 m) and 0.5-1.5 m deep layer in Jiaozhou Bay. However, the highest growth rate in Shenao Bay appeared under the lowest initial stocking density treatment. In the laboratory, the aquarium experiments (fish and seaweed culture systems) demonstrated that Gracilaria was able to remove inorganic nutrients effectively. The concentration of NH4+-N decreased by 85.53% and 69.45%, and the concentration of PO4-P decreased 65.97% and 26.74% in aquaria with Gracilaria after 23 days and 40 days, respectively. The results indicate that Gracilaria has the potential to remove excess nutrient from coastal areas, and the large-scale cultivation of G. lemaneiformis could be effective to control eutrophication in Chinese coastal waters. (c) 2005 Elsevier B.V. All rights reserved.

Cross-Ocean distribution of Rhodobacterales bacteria as primary surface colonizers in temperate coastal marine waters

Bacterial surface colonization is a universal adaptation strategy in aquatic environments. However, neither the identities of early colonizers nor the temporal changes in surface assemblages are well understood. To determine the identities of the most common bacterial primary colonizers and to assess the succession process, if any, of the bacterial assemblages during early stages of surface colonization in coastal water of the West Pacific Ocean, nonnutritive inert materials (glass, Plexiglas, and polyvinyl chloride) were employed as test surfaces and incubated in seawater off the Qingdao coast in the spring of 2005 for 24 and 72 h. Phylogenetic analysis of the 16S rRNA gene sequences amplified from the recovered surface-colonizing microbiota indicated that diverse bacteria colonized the submerged surfaces. Multivariate statistical cluster analyses indicated that the succession of early surface-colonizing bacterial assemblages followed sequential steps on all types of test surfaces. The Rhodobacterales, especially the marine Roseobacter clade members, formed the most common and dominant primary surface-colonizing bacterial group. Our current data, along with previous studies of the Atlantic coast, indicate that the Rhodobacterales bacteria are the dominant and ubiquitous primary surface colonizers in temperate coastal waters of the world and that microbial surface colonization follows a succession sequence. A conceptual model is proposed based on these findings, which may have important implications for understanding the structure, dynamics, and function of marine biofilms and for developing strategies to harness or control surface-associated microbial communities.

Distribution and their pollution assessment of heavy metals in the sediments of the Yalu River Estuary and its adjacent coastal waters

The present paper deals with the distribution patterns of heavy metals and the associated influencing factors in the Yalu River Estuary and its adjacent coastal waters. Based upon the analysis of the surficial and core sediments measurements, the pollution of heavy metal and potential ecological risk were evaluated. The burial flux and contents of heavy metals (except for copper) have been continuously increasing since the 1920s. Therefore, the gross potential ecological risk for the sediments was high or very high, and the study area was endangered by heavy metals contamination. Heavy metals originated mainly from upstream pollutant input, correlation analysis showed that chromium, nickel, zinc, cadmium, lead, arsenic, and mercury in the sediments of the middle and west channels as well as the sea area of the western Yalu River Estuary concentrations were most probably derived from similar sources. In contrast, the metal of copper most probably originated from sources different from the other metals. Preliminary studies indicate that copper contamination was most likely the result of emission from mining activities situated at the upstream of the river. The contents of heavy metals in the sediments of estuarine turbidity maximum zone of Yalu River were larger than those of any other areas in the middle channel. With large portion of fine sediments, weaker hydrodynamics, and richer sources of heavy metals, the sediments of the west channel, were even more enriched with heavy metals than those of the middle channel.

Modern changes of tidal troughs among the radial sand ridges in northern Jiangsu coastal zone

Using satellite images taken on different dates, GIS analysis of aerial photos, bathymetric maps and other field survey data, tidal troughs and major sand ridges in the northern Jiangsu coastal area were contrasted. The results show that there have been three types of movement or migration of tidal trough in this area: (1) Periodic and restricted, this type of trough usually developed along the beaches with immobile gully head as a result of the artificial dams and the swing range increased from gully head to the low reaches, so they have been obviously impacted by human activity and have longer swing periods; (2) Periodic and actively, this kind of trough, which swung with a fast rate and moved periodically on sand ridges, were mainly controlled by the swings of the host tidal troughs and hydrodynamic forces upon tidal sand ridge and influenced slightly by human constructions; (3) Steadily and slowly, they are the main tidal troughs with large scale and a steady orientation in this area and have slow lateral movement. The differences in migration mode of tidal trough shift result in different rates of migration and impact upon tidal sand ridges. Lateral accumulation on current tidal trough and deposition on abandoned tidal troughs are the two types of sedimentation of the tidal sand ridges formation. The whole radial sand ridge was generally prone to division and retreat although sand ridges fluctuated by the analysis of changes in talwegs of tidal troughs and shorelines of sand ridges.

The Shandong mud wedge and post-glacial sediment accumulation in the Yellow Sea

Two well-defined deltaic sequences in the Bohai Sea and in the South Yellow Sea represent post-glacial accumulation of Yellow River-derived sediments. Another prominent depocenter on this epicontinental shelf, a pronounced clinoform in the North Yellow Sea, wraps around the northeastern and southeastern end of the Shandong Peninsula, extending into the South Yellow Sea. This Shandong mud wedge is 20 to 40 m thick and contains an estimated 300 km(3) of sediment. Radiocarbon dating, shallow seismic profiles, and regional sea-level history suggest that the mud wedge formed when the rate of post-glacial sea-level rise slackened and the summer monsoon intensified, at about 11 ka. Geomorphic configuration and mineralogical data indicate that present-day sediment deposited on the Shandong mud wedge comes not only from the Yellow River but also from coastal erosion and local rivers. Basin-wide circulation in the North Yellow Sea may transport and redistribute fine sediments into and out of the mud wedge.

Dominant chloramphenicol-resistant bacteria and resistance genes in coastal marine waters of Jiaozhou Bay, China

Studies of abundance, diversity and distribution of antibiotic-resistant bacteria and their resistance determinants are necessary for effective prevention and control of antibiotic resistance and its dissemination, critically important for public health and environment management. In order to gain an understanding of the persistence of resistance in the absence of a specific antibiotic selective pressure, microbiological surveys were carried out to investigate chloramphenicol-resistant bacteria and the chloramphenicol acetyltransferase resistance genes in Jiaozhou Bay after chloramphenicol was banned since 1999 in China. About 0.15-6.70% cultivable bacteria were chloramphenicol resistant, and the highest abundances occurred mainly in the areas near river mouths or sewage processing plants. For the dominant resistant isolates, 14 genera and 25 species were identified, mostly being indigenous estuarine or marine bacteria. Antibiotic-resistant potential human or marine animal pathogens, such as Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Shewanella algae, were also identified. For the molecular resistance determinants, the cat I and cat III genes could be detected in some of the resistant strains, and they might have the same origins as those from clinical strains as determined via gene sequence analysis. Further investigation about the biological, environmental and anthropogenic mechanisms and their interactions that may contribute to the persistence of antibiotic-resistance in coastal marine waters in the absence of specific antibiotic selective pressure is necessary for tackling this complicated environmental issue.

Response of coastal marine eco-environment to river fluxes into the sea: A case study of the Huanghe (Yellow) River mouth and adjacent waters

The impact of the Huanghe (Yellow) River outflows on its estuary was investigated with river gauging and shipboard hydrographic observations. The river flux has been decreasing dramatically; the discharges of water and sediment in the 1990s dropped to 27.4% and 31.9% of those in the 1950s, respectively, resulting in frequent and lengthy events of downstream channel dry-up since the 1970s. There were accumulatively 897 zero-flow days during the 1990s in the river course below the Lijin Hydrological Station, 100 km upstream from the river mouth, which is 82.4% of that in 1972. As freshwater input decreases, river-borne nutrients to the estuarine increased significantly. Concentration of dissolved inorganic nitrogen (DIN) in the 1990s was four times of that in 1950s. Changes in amount and content of the riverine inputs have greatly affected the estuarine ecosystem. Over the past several decades, sea surface temperature and salinity in the estuary and its adjacent waters increased and their distribution pattern altered in response to the reduction of freshwater inflow. The distribution of and seasonal succession in nutrient concentrations in the surface layer have also changed with a shift of river outlet and the decrease in riverine nutrient loads. Furthermore, deterioration of estuarine ecosystem by less river input has decreased primary productivity in the deltaic region waters, and in turn depressed the fishery. (C) 2008 Published by Elsevier Ltd.

Characteristics of shallow gas hydrate in Okhotsk Sea

Multidisciplinary field investigations were carried out in Okhotsk Sea by R/V Akademik M.A. Lavrentyev (LV) of the Russian Academy of Sciences (RAS) in May 2006, supported by funding agencies from Korea, Russia, Japan and China. Geophysical data including echo-sounder, bottom profile, side-scan-sonar, and gravity core sample were obtained aimed to understand the characteristics and formation mechanism of shallow gas hydrates. Based on the geophysical data, we found that the methane flare detected by echo-sounder was the evidence of free gas in the sediment, while the dome structure detected by side-scan sonar and bottom profile was the root of gas venting. Gas hydrate retrieved from core on top of the dome structure which was interbedded as thin lamination or lenses with thickness varying from a few millimeters to 3 cm. Gas hydrate content in hydrate-bearing intervals visually amounted to 5%-30% of the sediment volume. This paper argued that gases in the sediment core were not all from gas hydrate decomposition during the gravity core lifting process, free gases must existed in the gas hydrate stability zone, and tectonic structure like dome structure in this paper was free gas central, gas hydrate formed only when gases over-saturated in this gas central, away from these structures, gas hydrate could not form due to low gas concentration.

A semi-analytical theory of coastal upwelling and jet

The general forms of the conservation of momentum, temperature and potential vorticity of coastal ocean are obtained in the x-z plane for the nonlinear ocean circulation of Boussinesq fluid, and a elliptic type partial differential equations of second order are derived. Solution of the partial differential equations are obtained under the conditions that the fluid moves along the topography. The numerical results show that there exist both upwelling and downwelling along coastline that mainly depends on the large scale ocean condition. Numerically results of the upwelling (downwelling), coastal jet and temperature front zone are favorable to the observations.