Changes in benthic communities along a presumed pollution gradient in Vancouver Harbour

Samples of macrobenthic organisms were obtained at seven stations on a presumed pollution gradient from the head of Vancouver Harbour through to outer Howe Sound. Polychaetes (83 apparent species) and molluscs (43 apparent species) were the most abundant faunal groups numerically (44.8 and 47.9%, respectively). Molluscs accounted for most of the biomass (87.9%). The following univariate and multivariate methods were used to investigate structural changes in the benthic communities: ANOVA, Abundance-Biomass Comparisons and related statistics, cluster analysis, multidimensional scaling, and the BIOENV procedure. Most of the analyses divided the seven stations into three groups: Port Moody Arm (Inner Harbour): two stations; Inner and Outer Harbour: four stations, and Gibsons (Howe Sound): one station. Further cause-effect investigations are needed to determine the sensitivity to organic pollution of indicator species identified in the survey. However our data correlating benthic community changes to sediment chemistry suggest the inner harbour was dominated by pollution-tolerant species. Depth and sediment grain size were confounding factors for the interpretations.     

Factors Affecting the Wintering Habitat of Major Fishery Resources in Southwestern Korean Waters

We investigated the temperature and salinity effects on the major fish species in the wintering grounds based on trawl surveys and oceanographic observations in the southwestern waters of Korea during March-early April in 2002-2003. The influence area of warm Kuroshio water was limited to the southwestern area of Korea in 2003 with a range of 7.7-16.3°C, 32.54-34.70 of salinity, wider than that of 2002. The number of fish species and density of major fish species in 2003 were higher than in 2002. Geographical estimation showed high proportions of species number and catches in the areas around Jeju Islands, southwestern waters and the southeastern coast of Korea. Five species; silver pomfret (Pampus echinogaster), hairtail (Trichiurus lepturus), anchovy (Engraulis japonicus), small yellow croaker (Larimichthys polyactis) and yellow goosefish (Lophius litulon) were most abundant, composing above 60% of the total catch in 2002 and 2003. More than 50% of catch in the major fish species were mostly distributed in the range of 9.5-11.0°C of temperature and 33.1-33.9 of salinity. Non-parametric estimation for the major species showed the 1st mode around 10°C and the 2nd mode at 8-9°C in 2002 and 11-14°C in 2003. A m o n g major fish species, hairtail was principally composed of juveniles, and larger individuals were caught in southeastern waters. These results are considered to be helpful for the areabased fishery management strategy for the wintering grounds of the Yellow Sea and coastal waters of Korea.     

Seasonal variation of freshwater budget in the Yellow and East China Seas simulated from an ocean general circulation model

This study investigates a freshwater budget in the Yellow and East China Seas (YECS) using a global f general circulation model with a regional focus on the YECS. A freshwater budget analysis finds that major freshwater contributors over the YECS change seasonally. In summer, freshwater inflow from Changjiang and positive precipitation minus evaporation (P-E) dominates freshwater outflow across the boundaries around the YECS, resulting in net freshwater gain in the YECS. In winter, evaporation, intensified by strong winds, dominates freshwater inflow from Changjiang and precipitation, while net freshwater transport across the boundaries around the YECS is negligible, causing freshwater loss in total over the YECS. Although P-E has often been assumed to be negligible by supposing that the annual mean of precipitation is nearly equal to that of evaporation, this study suggests that P-E needs to be included in the seasonal freshwater budget in the YECS.     

Estimates of sediment and nutrient loads in 10 major catchments draining to the Great Barrier Reef during 2006-2009

The Great Barrier Reef (GBR) catchment area has been monitored simultaneously for sediment and nutrient exports from 10 priority catchments discharging into the GBR lagoon between 2006 and 2009. This allows GBR catchment-wide exports to be estimated and spatially compared within a discrete time-frame. Elevated levels of sediment and nutrient exports were recorded in all monitored catchments as compared to pre-European estimates, but vary around previous estimates of mean annual loads. During the period of monitoring, the Burdekin and Fitzroy catchments contributed the highest sediment and nutrient exports, however when loads were normalised for area, these catchments produced the lowest unit yields. In contrast, the highest yields were produced in the wetter and proportionately more intensively cultivated Johnstone, O'Connell, and Pioneer catchments particularly for dissolved nitrogens. This assessment offers the necessary scientific foundation for future monitoring, assessment, and management of sediment and nutrient loads entering the GBR.     

A discontinuity in the late Pleistocene alluvial deposits,Hwacheon‐ri,Gyeongju, Korea: Occurrences and paleoenvironmental implication

A sedimentary discontinuity is present in the late Pleistocene alluvial deposits exposed along the cliff in stream side, Gyeongju, Korea. Sedimentological study, Optically Stimulated Luminescence (OSL) age dating, and X‐ray diffraction (XRD), and X‐ray fluorescence spectrometer (XRF) analyses were conducted in order to interpret the origin of the discontinuity surface. Based on the sedimentological study, these deposits can be divided into three distinct stages, in ascending order: (Stage 1) development of a braided stream flowing from south to north and deposition by debris flows from the mountain aside the stream during and/or after deposition of the braided stream; (Stage 2) deposition by intermittent events during a state of stagnation after the abandonment or migration of the previously existed braided stream; and (Stage 3) deposition of gravels from debris flows from the mountain aside the stream. Hornfelsic gravels are common in Stage 1, whereas andesitic gravels are predominant in Stage 3, suggesting the provenance change from Stage 1 to Stage 3. The discontinuity surface is laterally extensive and marked by a distinct carbonaceous dark grey horizon between Stage 2 and Stage 3. It is characteristic that rootlets mineralized by vivianite are present, and iron‐oxide crusts are cutting across irregularly below the discontinuity surface. It is thus interpreted that the shift of depositional environment from an alluvial plain (Stage 2) (125 ka) to an alluvial fan (Stage 3) (94–55 ka) was an alluvial response to sea level change from the interglacial to the glacial. The development of iron‐oxide crusts and diagenetic vivianite in the discontinuity surface suggests humid condition persisted during the paleoclimatic shift from the last interglacial to the last glacial stages.     

A Review on the Macromolecular Compositions of Phytoplankton and the Implications for Aquatic Biogeochemistry

Ocean Science Journal - Biochemical composition of phytoplankton is a key indicator of the physiological and nutritional status of phytoplankton. A balanced biochemical pattern represents a healthy...     

Experimental restoration of a salt marsh with some comments on ecological restoration of coastal vegetated ecosystems in Korea

Since the 1980s, the coastal wetlands in Korea have been rapidly degraded and destroyed mainly due to reclamation and landfills for coastal development. In order to recover damaged coastal environments and to develop wetland restoration technologies, a 4-year study on ecological the restoration of coastal vegetated ecosystems was started in 1998. As one of a series of studies, a small-scale experiment on salt marsh restoration was carried out from April 2000 to August 2001. The experiment was designed to find effective means of ecological restoration through a comparison of the changes in environmental components and species structure between two different experimental plots created using sediment fences, one with and one without small canals. Temporal variation in surface elevation, sedimentary facies, and benthic species were measured seasonally in each plot and in the adjacent natural reference sites. Monthly exposure occurred from 330 cm to mean sea level, which represents the critical tidal level (CTL) at which salt marsh plants colonize. Vegetation, especially Suaeda japonica, colonized the site the following spring and recovered to a similar extent in the natural marshes 16 months later. The sedimentary results indicated that the sediment fences had effects on particle size and sediment accumulation, especially in the plot with small canals. This experiment also showed that tidal height, especially that exceeding the CTL, is an important factor in the recovery of the benthic fauna of salt marshes. From these results, we suggested that designs for the restoration of salt marsh ecosystems must consider the inclusion of a tidal height exceeding CTL, as this may allow reconstruction of the previous natural ecosystem without artificial transplanting.     

Sediment mounds and other sedimentary features related to hydrate occurrences in a columnar seismic blanking zone of the Ulleung Basin, East Sea, Korea

A mound related to a cold vent in a columnar seismic blanking zone (CSBZ) was formed around site UBGH1-10 in the central Ulleung Basin (2077 m water depth), East Sea, Korea. The mound is 300–400 m wide and 2–3 m high according to multi-beam bathymetry, 2–7 kHz sub-bottom profiler data, and multi-channel reflection seismic data. Seafloor topography and characteristics were investigated using a remotely operated vehicle (ROV) around site UBGH1-10, which is located near the northern part of the mound. The origin of the mound was investigated through lithology, mineralogy, hydrate occurrence, and sedimentary features using dive cores, piston cores, and a deep-drilling core. The CSBZ extends to ∼265 ms two-way traveltime (TWT) below the seafloor within a mass-transport deposit (MTD) unit. Gas hydrate was entirely contained 6–141 m below the seafloor (mbsf) within hemipelagic deposits intercalated with a fine-grained turbidite (HTD) unit, characteristically associated with high resistivity values at site UBGH1-10. The hydrate is commonly characterized by veins, nodules, and massive types, and is found within muddy sediments as a fracture-filling type. Methane has been produced by microbial reduction of CO₂, as indicated by C₁/C₂₊, δ¹³CCH4, and δD₄CH analyses. The bowl-shaped hydrate cap revealed at 20–45 ms TWT below the seafloor has very high resistivity and high salinity, suggesting rapid and recent gas hydrate formation. The origin of the sediment mound is interpreted as a topographic high formed by the expansion associated with the formation of the gas hydrate cap above the CSBZ. The lower sedimentation rate of the mound sediments may be due to local enhancement of bottom currents by topographic effects. In addition, no evidence of gas bubbles, chemosynthetic communities, or bacterial mats was observed in the mound, suggesting an inactive cold vent.     

Spatial polychaeta habitat potential mapping using probabilistic models

The purpose of this study was to apply probabilistic models to the mapping of the potential polychaeta habitat area in the Hwangdo tidal flat, Korea. Remote sensing techniques were used to construct spatial datasets of ecological environments and field observations were carried out to determine the distribution of macrobenthos. Habitat potential mapping was achieved for two polychaeta species, Prionospio japonica and Prionospio pulchra, and eight control factors relating to the tidal macrobenthos distribution were selected. These included the intertidal digital elevation model (DEM), slope, aspect, tidal exposure duration, distance from tidal channels, tidal channel density, spectral reflectance of the near infrared (NIR) bands and surface sedimentary facies from satellite imagery. The spatial relationships between the polychaeta species and each control factor were calculated using a frequency ratio and weights-of-evidence combined with geographic information system (GIS) data. The species were randomly divided into a training set (70%) to analyze habitat potential using frequency ratio and weights-of-evidence, and a test set (30%) to verify the predicted habitat potential map. The relationships were overlaid to produce a habitat potential map with a polychaeta habitat potential (PHP) index value. These maps were verified by comparing them to surveyed habitat locations such as the verification data set. For the verification results, the frequency ratio model showed prediction accuracies of 77.71% and 74.87% for P. japonica and P. pulchra, respectively, while those for the weights-of-evidence model were 64.05% and 62.95%. Thus, the frequency ratio model provided a more accurate prediction than the weights-of-evidence model. Our data demonstrate that the frequency ratio and weights-of-evidence models based upon GIS analysis are effective for generating habitat potential maps of polychaeta species in a tidal flat. The results of this study can be applied towards conservation and management initiatives for the macrofauna of tidal flats.