The spatial and temporal distribution of heavy metals in sediments of Victoria Harbour, Hong Kong

Author name used in this publication: Chloe Wing-yee TangAuthor name used in this publication: Carman Ching-man Ip2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Transplant experiments on growth and mortality of the fan mussel Pinna bicolor

Growth and mortality for different size classes (30-49 mm, 50-79 mm and 80-100 mm shell width) of the fan mussel Pinna bicolor transplanted at open sea bottom, within enclosure cages, and on suspended rafts were studied and compared over an 18-month study period. Growth, in terms of shell width, dry tissue weight and condition index of the same size class, did not show significant differences (P > 0.05) between the transplanted populations at the open sea bottom and in enclosure cages. Fastest growth was noted for the small-size class during the initial 12-month period, with a net increase in maximum shell width of 50-60 mm (100-120 mm shell length). Thereafter, growth tended to slow down and all growth parameters became similar for all the three size classes. In comparison of the small-size fan mussels between the bottom (open and caged) transplants and that on the suspended rafts, a better growth result was registered in the suspended raft population possibly due to a faster induced flow and availability of food in the water column. Mortality of transplanted P. bicolor was the highest at open sea bottom, and predominantly caused by predation by fish and crabs. Highest mortality was also noted in the small-size class as the larger fan mussels were less vulnerable to predation than the small juvenile. The number of transplanted P, bicolor at open sea bottom fell to the same natural density within the fast 12 months of the study and stabilized afterwards, suggesting that the natural population of P. bicolor was controlled by its predators. In rearing of fan mussels, both growth and mortality should be considered in concert, so as to select an optimal size class of transplants which would attain the maximum growth, with minimum mortality, over the culture period.link_to_subscribed_fulltex

Sediment characteristics and colonization of soft-bottom benthos: A field manipulation experiment

A field manipulation experiment was carried out to test the effects of sediment characteristics (particle size and organic content) on colonization of soft-bottom benthos. Defaunated mud and sand in experimental trays were exposed at sub-tidal levels of two sites with sandy and muddy sea bottom, and retrieved monthly for examination of benthic composition. Seventy-eight out of the 107 species recorded, and 50% of the dominant species identified in the present study, were common in both the sand and mud trays. Classification analysis revealed higher faunal similarity of benthic composition in both sediment types within each of the two study sites. Results of three-way ANOVA (Sediment, Site and Time) showed that sediment effect was only significant for colonization of bivalves and gastropods, but not for polychaetes, amphipods, total species and individual numbers, or overall benthic diversity and evenness. This suggested that many of the benthic species can colonize both sediment types, and that factors other than sediment particle size and organic content may play a significant role in determining colonization of these species. The faunal composition of the same sediment type between sites was found to be different, indicating that the availability and abundance of benthic larvae/adults may be more important than sediment characteristics in determining benthic settlement. An increase in faunal similarity between mud and sand was observed over the study period, implying that the importance of sediment characteristics to benthic colonization decreased with exposure time.link_to_subscribed_fulltex

Food segregation in three species of portunid crabs

Gastric mills of 2,619 specimens of portunid crabs (Portunus pelagicus, P. sanguinolentus and Charybdis feriatus) in Tolo Harbour, Hong Kong were examined. Of these, 1,498 contained recognizable food items. A total of 34 food items were identified, 10 of which (29.4%) were common to the three crab species. The principal food items were bivalves, decapods, fish and algae. However, the percent frequency of occurrence of these food items differed significantly (ANOVA, p < 0.001) among the crabs. In addition to these principal food items, differences were noted in other dietary categories: P. pelagicus and P. sanguinolentus fed on the brittle star Ophiura kinbergi, whereas P sanguinolentus and C. feriatus fed on detritus and gastropods. The diet of P. sanguinolentus was found to be more similar to C. feriatus than to P. pelagicus. Exploitation of different food items and selective feeding on common prey may reduce inter-specific competition for natural food resources and allow the three portunid crabs to co-exist in the same habitat.link_to_subscribed_fulltex

Turning the tides - 33 Years of Professor Brian Morton

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Induction, adaptation and recovery of lysosomal integrity in green-lipped mussel Perna viridis

Biomarkers are generally applied to detect pollution in environmental monitoring. Such biological responses should accurately reflect the stress over time in a quantitative manner. As such, the initial and maximum responses induced by stress, as well as adaptation and recovery of these biomarkers, need to be fully understood or else erroneous false-negative or false-positive may be arrived. However, most of the biomarker studies only provided information on initially induced responses under different concentrations of toxicants, while biological adaptation and recovery were poorly known. In this study, the time required for induction, adaptation and recovery of lysosomal integrity in green-lipped mussel Perna viridis upon exposure to benzo[a]pyrene was investigated over a period of 62 days. Maximum induction occurred on day 6 when lysosomal integrity was significantly reduced by 51%, and no further change or adaptation was detected thereafter. When mussels were depurated in clean seawater after 18 days of exposure to benzo[a]pyrene, a gradual recovery was observed, with lysosomal integrity returning to its background level and showing a complete recovery after 20 days of depuration. Lysosomal integrity was significantly correlated with the body burden concentrations of benzo[a]pyrene and condition index of the mussels. The relatively fast induction (6 days) and recovery (20 days) without apparent adaptation suggested that lysosomal integrity in P. viridis can serve as a good biomarker in biomonitoring, as its response is not likely to generate both false-negative and false-positive results. © 2008 Elsevier Ltd. All rights reserved.link_to_subscribed_fulltex

Seasonality of bioaccumulation of trace organics and lysosomal integrity in green-lipped mussel Perna viridis

Lysosomal integrity in mussels is widely used as a biomarker in coastal environments to demonstrate exposure to trace organic pollutants. However, few studies have determined the long-term influences of seasonal variations on the bioaccumulation of trace organics and subsequently altered response of lysosomal integrity in mussels. This study aimed to test three null hypotheses that (1) bioaccumulations of total polycyclic aromatic hydrocarbon (∑ PAH) and (2) total polychlorinated biphenyl (∑ PCB), and (3) lysosomal integrity as indicated by Neutral Red retention time (NRRT) in haemocytes, in the green-lipped mussel Perna viridis were not seasonally dependent. The tissue concentrations of ∑ PAH and ∑ PCB and haemocytic NRRT were determined in P. viridis in a metropolitan harbour, subtropical Hong Kong during the wet and dry seasons from 2004 to 2007. Additional information on temperature, salinity, dissolved oxygen and total ammonia nitrogen in seawater, and sediment levels of ∑ PAH and ∑ PCB, were extracted from published data and re-analyzed. Our results accepted all null hypotheses, based on the minimal seasonal influences of seawater temperature and salinity on all studied parameters, in which no significant differences between the wet and dry seasons were detected. The seasonal effect was likely outweighed by the greatly improved water quality and pollution abatement noted inside the harbour, with a gradual shift in mussel PAHs from a pyrolytic origin to a petrogenic origin. Spatially, the site east of the harbour was relatively unpolluted. The single use of NRRT in P. viridis explained 25% of the total variation of the integrated pollution patterns in seawater, sediments and mussels. The present study suggested that the dynamic change of trace organics could be reflected by the response on lysosomal integrity in P. viridis, which was recommended as a routine screening biomarker in monitoring of harbour water quality across seasons. © 2009 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex

An updated baseline of subtropical macrobenthic communities in Hong Kong

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The use of muscle burden in rabbitfish Siganus oramin for monitoring polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Victoria Harbour, Hong Kong and potential human health risk

Muscle concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) were determined in rabbitfish Siganus oramin collected from Victoria Harbour and its vicinity, Hong Kong from 2004 to 2007. Spatially, relatively higher levels of ∑PAH (1.05-4.26 μg g- 1) and ∑PCB (45.1-76.9 ng g- 1) were determined in the central and western sites inside the harbour. Temporally, upward trend of ∑PAH, accompanied with a proportion shift from high molecular weight to low molecular weight PAHs, was detected during the three-year study period, suggesting a heavier marine traffic in Victoria Harbour and its western region. However, human health risk assessment based on five individual PAHs indicated that PAHs in fish muscles posed minimal health risk through consumption. In contrast, a downward trend of ∑PCB was registered as the open use of PCBs has been banned. Despite this, the level of ∑PCB in fish muscles still posed a health risk on the local people who have a high fish consumption rate. While seasonal influences on ∑PAH/∑PCB accumulation in S. oramin seemed to be negligible, our findings in S. oramin were in line with the established PAH and PCB levels in sediments and/or mussels from the harbour, suggesting S. oramin can be used as a model fish species for monitoring PAHs and PCBs in the region. © 2009 Elsevier B.V. All rights reserved.link_to_subscribed_fulltex