Observations on vertical distribution of fungi associated with standing senescent Acanthus ilicifolius stems at Mai Po Mangrove,Hong Kong

The present study was carried out to investigate the higher fungi colonizing the herbaceous mangrove associate Acanthus ilicifolius. This paper reports part of an investigation to determine if there is vertical distribution of fungi on the standing plant.The Mai Po Mangrove, Hong Kong is estuarine with great variations in salinity mainly due to the influence of the Pearl River. Senescent and dead stems of standing Acanthus ilicifolius were collected from mangroves in Mai Po from April to December 1992. The maximum tidal range observed was 2.6 m. A stratified sampling strategy was employed to assess the vertical distribution on the standing plant. A total of 44 fungi were collected: 32 Deuteromycotina, 11 Ascomycotina and 1 Basidiomycotina. Very frequent species were Acremonium sp.(55%), Colletotrichum gloesporioides cf.(42.5%), Phoma sp. (42.5%) Fusarium sp.,(25%), Tubercularia sp. (24.2%) and Phialophora sp. cf. (19.2%). Agerita sp., Corynespora cassiicola, Stachybotrys chartarum, Trichoderma sp. and D82 were frequent, while the remaining species were recorded at less than 10%. Vertical zonation of fungi colonizing the standing stems was observed. The apical portions were colonized by typical terrestrial fungi and the basal portions by marine species. This can be attributed to both the nature of the substratum and the degree of exposure due to tidal inundation.     

The fate of traditional extensive (gei wai) shrimp farming at the Mai Po Marshes Nature Reserve, Hong Kong

Extensive shrimp farming around Deep Bay, Hong Kong,began in the mid-1940‘s after the construction of intertidal ponds (gei wai) among the coastal mangroves. The ponds are increasingly being seen as an example of how wetlands can be used sustainablysince they are naturally stocked with shrimp postlarvae (e.g. Metapenaeus ensis) and young fish (e.g. Mugil cephalus) flushed into the ponds from Deep Bay. Once inside, these shrimps and fish feed on naturally occurring detritus on the pond floor. The only gei wai remaining in the Territory, are those at the WWF Hong Kong Mai Po Marshes Nature Reserve, adjacent to Deep Bay. Analysis of the shrimp production between 1990–1995 showed that there were two seasonal peaks, from April–June (Recruitment-I)and from July–October (Recruitment-II). The second peak was significantly lower than the first (p <0.001), especially from those gei wai in the southern part of the reserve which are much closer to a polluted river. The average harvest from each gei wai had also significantly declined from40.9 ±6.0 kg ha⁻¹ yr⁻¹ in 1990 to15.1 ±3.6 kg ha⁻¹ yr⁻¹ in 1995 (p <0.01). This decline can be attributed to the abundance of predatory fish in the gei wai, and increasing water pollution in Deep Bay which adversely affects the amount of shrimp larvae for stocking the gei wai, as well as the quality of water for flushing the ponds during the rearing and harvesting seasons. Despite this, those gei wai which are not-commercially viable can still support many non-commercial, more pollution tolerant fish and shrimp species. As a result, the management of the segei wai has been altered such that their objective is to provide feeding habitat for piscivorous waterbirds, which is also in line with the aims of the nature reserve. This revised version was published online in August 2006 with corrections to the Cover Date.     

The population dynamics of Metapenueus ensis (Crustacea: Decapoda: Penaeidae) in a traditional tidal shrimp pond at the Mai Po Marshes Nature Reserve, Hong Kong

The population dynamics of Metapenaeus ensis in a traditional tidal shrimp pond (locally known as gei wai ) at the Mai Po Marshes Nature Reserve, Hang Kong, were studied over a 29-month period. The population of M. ensis was dominated by either one or two age groups throughout the year. Life span was < 16 months. M. ensis is sexually dimorphic in terms of size, with females growing faster and attaining a larger maximum size than males. The sex ratio did not differ significantly from 1:1. The prawns do not mature and reproduce in the gei wai so that the population is sustained by postlarval immigration which begins in June and ends in December, with peaks in August and November. The gei wai population of M. ensis is characterized by slower growth, lower maximum attainable size, shorter life span, reproductive sterility and an incomplete life cycle, as compared with 'natural' population in the coastal waters of Hong Kong.     

香港茜草科植物新记录

查阅馆藏植物标本,有3种茜草科植物：丹草（Hedyotis herbacea）、小耳草（H.pumila）和蕴璋耳草（Scleromitrion koanum）为香港新记录。这些资料为香港的生物多样性工作提供了基础数据。     

Mycorrhizal associations in Hong Kong Fagaceae

Polyphenols histochemically detected in fresh uninfected roots of Quercus, Castanopsis and Lithocarpus growing in Hong Kong and shown to be condensed tannins were found mainly as intracellular material in the cells of the root cap, the epidermal layer and the endodermis. The cell walls of the outer cortex and the endodermis also contained suberin. Following invasion by compatible ectomycorrhizal symbionts, condensed tannins disappeared from cells of the root cap and the epidermal layer but hyphae were prevented from colonizing the cortex presumably due to suberin barriers. In vitro experiments indicated that a number of broad-host ectomycorrhizal fungi could utilise various polyphenolic compounds, including tannins found in the root exudates of the host trees, with different degrees of efficiency.     

Microbiological quality of pork meat from local Hong Kong markets

Over a 3-week period, samples of fresh, chopped, pork meat were taken every morning and afternoon from 50 meat stalls. Microbiological examination revealed that the samples had (c.f.u./g): total microbes, 1×10³ to 2.14×10⁶; mean probable numbers of coliforms and Escherichia coli, 1.51×10³ to 1.15×10⁴; and yeasts and moulds, 0 to 1.28×10⁴. Salmonella, found in 32 samples from 21 stalls, were serotyped as B (three samples), C1 (four) or E (25). No Campylobacter were found. Because microbial growth and/or contamination of the meat occurred during the day, samples taken in the afternoon had greater total counts (P<0.05) and contained detectable numbers of Salmonella more frequently (42% versus 22%) than those taken in the morning.The author is with the Department of Biology and Chemistry, City Polytechnic of Hong Kong, 83 Tat Chee Ave, Kowloon, Hong Kong     

Burrow Architecture of the Ghost Crab Ocypode ceratophthalma on a Sandy Shore in Hong Kong

The ghost crab Ocypode ceratophthalma (Pallas) creates burrows of variety shapes at different ages. Juveniles (mean carapace length 11 mm) produced shallow J-shaped burrows, which incline vertically into the substratum (mean depth 160 mm). Larger crabs (17–25 mm carapace length) have Y-shaped and spiral burrows (mean depth 361 mm). These Y-shaped burrows have a primary arm, which extends to the surface forming the opening, and a secondary arm which terminates in a blind spherical ending. The two arms join in a single shaft and end with a chamber at the base. The secondary arms and chambers are believed to be used for mating or as a refuge from predation. The spiral burrows have spiral single channel ending in a chamber. Older crabs (mean carapace length 32.6 mm) had simple, straight single tube burrows, which inclined into the substratum at mean of 73° and had a mean depth of 320 mm. During summer daytime periods, the burrows shelter the crabs from heat and desiccation stress. The sand surface temperature at the burrow opening was ~48 °C but temperatures inside the burrows can drop to 32 °C at a depth of 250 mm. Variation in the burrow architecture with crab age appears to be related to the crab’s behaviour. Juvenile crabs have smaller gill areas and move out of the burrows regularly to renew their respiratory water and, as a result, they do not need a deep burrow. Larger crabs, in contrast, can tolerate prolonged periods without renewing their respiratory water and therefore create deeper and more complex burrows for mating and refuges.     

香港桦木科一新种——香港鹅耳枥(英文)

报道了桦木科(Betulaceae)鹅耳枥属(Carpinus L.)一新种——香港鹅耳枥(C.insularis N.H.Xia,K.S.PangY.H.Tong)。香港鹅耳枥与太鲁阁鹅耳枥(C.hebestroma Yamamoto)及多脉鹅耳枥(C.polyneura Franch.)相似,但习性灌木状,叶具13~16对侧脉,先端锐尖,边缘锯齿的芒尖较短,果苞宽半卵形或半卵形,长8~14 mm,小坚果顶端密被长柔毛且疏具树脂状腺体,与后两者易于区别。     

Phenology of Sargassum spp. in Tung Ping Chau Marine Park, Hong Kong SAR, China

Eight species of the brown alga Sargassum have been recorded from Tung Ping Chau Marine Park in Hong Kong and the phenology of four of these was monitored from 1996 to 2000. All four species followed a typical growth cycle of Sargassum species reported elsewhere but with some annual variations. For S. hemiphyllum, the maximum mean (±SD) plant length, ranging from 38.5 ± 10.5 to 61.9 ± 19.9 cm, was recorded in January to March. The peak reproductive season was also mainly in February to March with up to 89% of the plants being reproductive. Some plants, however, remained reproductive until May. For. S. henslowianum, the maximum mean plant length, ranging from 45.5 ± 25.5 to 77 ± 24.8 cm, was recorded mainly in November to January. The peak reproductive season was in November to February with up to 100% of the plants being reproductive. For S. siliquastrum, the maximum mean plant length, ranging from 48.2 ± 29.9 to 63.4 ± 22.1 cm, was also recorded mainly in January. The reproductive plants were found mainly between late December and mid February with up to 98% of the plants being reproductive. For. S. patens, the maximum mean plant length ranging from 87.6 ± 62.4 to 118.7 ± 41.3 cm was recorded in January to March. Reproduction of this species was not monitored. Changes in water temperature over seasons were likely to be critical in affecting the phenological patterns of these species.     

Large subunit rDNA sequences from Alexandrium catenella strains isolated during harmful algal blooms in Hong Kong

The partial sequences of the large subunit (24S) ribosomal RNA gene(LsurRNA) of three Alexandrium catenella strains isolatedduring the 1998 and 1989 red tide incidents in Hong Kong were compared,togetherwith the sequences of other Asian A. catenella speciescomplex. The sequences of two A. catenella strainsisolatedin 1998 were identical, despite being isolated at different time (March andApril) and different locations (eastern and southern Hong Kong). In cladisticanalysis, the two A. catenella HK98A & B strains, theA. catenella HK1989 strain, the Chinese strain clade andtheKorean/Japanese A. catenella form a clade distinct fromother A. catenella strains. Interestingly, the twoA. catenella HK98A & B strains only form a clade withtheA. catenella HK1989 strain/ChineseA. catenella (CCMP1493) with low bootstrap values (49%).     

Nutrient and faecal contamination and retention in wetland enclosures (gei wais) in the Mai Po Marshes,Hong Kong

Nutrient and faecal contamination is an increasing problem to the shrimp productivity and wildlife conservation at the internationally important wetland ecosystems of the Mai Po Marshes (Hong Kong, P.R. China). The present study examined the nutrient status and faecal bacteria loading and potential retention capacity of contaminants of two wetland enclosures. Water in the wetland enclosures was eutrophicated with high concentrations of dissolved inorganic nitrogen (inorg–N_diss= 15.0 mg l^–1) and orthophosphate phosphorus (o-P = 1.89 mg l^–1) and was loaded with high levels of faecal coliforms (172 ×10³ cfu in 100 ml) and faecal streptococci (1.94 ×10³ cfu in 100 ml). The pattern of nutrient enrichment of two wetland enclosures is related to a north-to-south pollution gradient from the Shenzhen River to the wetlands. By retaining tidal water in the wetland for an 8-day period, water quality was greatly improved; NH₄–N was removed by 83%, o-P by 45% and faecal bacteria by 100%. This implies a self-purification capability of the wetland enclosures and a potentiality of using them as an alternative sewage treatment.     

The population dynamics of some freshwater carideans (Crustacea: Decapoda) in Hong Kong,with special reference to Neocaridina serrata (Atyidae)

During a 15-month investigation of the population dynamics of three caridean shrimp species in the Lam Tsuen River, New Territories, Hong Kong, the numbers of the commonest species, Neocaridina serrata (Stimpson)(Atyidae), were reduced as water temperatures fell. By contrast, Caridina lanceifrons Yu became more numerous during the winter. The relatively scarce Macrobrachium hainanense (Parisi)(Palaemonidae) tended to be more abundant during the summer, and the abundance of this species was directly correlated with that of N. serrata. The population size of these two species was positively correlated with water temperatures prevailing one and two months prior to the collection of samples, but there was no significant relationship between C. lanceifrons abundance and water temperature.All species exhibited similar growth patterns with an inflection at the attainment of sexual maturity, occurring after the (presumed) 14th moult for N. serrata and in the (presumed) 13th and 18th stadium for C. lanceifrons and M. hainanensis respectively. Ovigerous shrimps of all species were only recorded when water temperatures exceeded 20 °C and the % incidence of ovigerous N. serrata was positively correlated with prevailing temperatures. It is suggested that restriction of freshwater caridean breeding periods by low temperatures may be common in the subtropics while perennial breeding is more likely to be typical of tropical regions.The mean carapace length of N. serrata populations was negatively correlated with prevailing temperatures, but more strongly correlated with temperatures recorded one and two months prior to sampling when gametogenesis may have taken place. Smallest mean sizes were recorded in late summer upon the cessation of juvenile recruitment. N. serrata has a maximum longevity of approximately 12 months and reproduction occurs in the 7th month of life or later. The hatchlings are well developed and clutch size is not related to the size of the brooding female. An annual life cycle, as seen in N. serrata, may be typical of many small freshwater carideans.Department of Zoology, The University of Hong Kong     

Seasonal patterns of pore-water nutrients, benthic chlorophyll a and sedimentary AVS in a macrobenthos-rich tidal flat

Monthly field investigations were carried out at controlled low-tide in an estuarine intertidal sandflat of the Seto Inland Sea (Japan) between January 1995 and April 1996. We assessed the spatial and temporal distribution of pore-water nutrient [NH ₄ ⁺ -N, (NO ₃ ⁻ + NO ₂ ⁻ )-N, PO ₄ ³⁻ -P and Si(OH)₄-Si], chlorophyll a (chl a) and acid-volatile sulphide (AVS) concentrations in the uppermost 0–10 cm sediment horizon, and evaluated their relationships with macrobenthic assemblages. Monthly hydrological data, nutrient and chl a concentrations in low-tide creek water adjacent to the flat were used as a complementary environmental characterisation of the study area. All different pore-water nutrients showed a 10 to > 30-fold variability between different layers and periods. NH ₄ ⁺ -N, PO ₄ ³⁻ -P and Si(OH)₄-Si concentrations were lowest in winter, progressively increased throughout spring and summer, and were highest between September and October, with a major increase at intermediate (4–8 cm) layers. In contrast, (NO ₃ ⁻ + NO ₂ ⁻ )-N concentrations, correlated positively with chl a, peaked in winter and sharply decreased with depth in all different seasons and in most occasions. Depth-integrated NH ₄ ⁺ -N, PO ₄ ³⁻ -P and Si(OH)₄-Si pools were correlated positively with biogenic nutrient flux calculated from the nutrient excretion rates of dominant bivalves Ruditapes philippinarum and Musculista senhousia. These relationships indicated rapid removal pathways of P, Si and N (i.e., every 0.1, 0.24 and 0.34 day, respectively), implying highly dynamic sediments. Based on the mass balance P = F + I, biogenic production (P) vs. diffusive flux (F) estimates suggested a predominant contribution of animal bioirrigation (I) to the upward flux of nutrients. AVS concentrations, correlated negatively with both (NO ₃ ⁻ + NO ₂ ⁻ )-N and chl a, showed a progressive increase from late summer throughout winter, subsequent to that of NH ₄ ⁺ -N, PO ₄ ³⁻ -P and Si(OH)₄-Si. The results indicate that in our study area the spatial and temporal distribution of pore-water nutrients, chl a and AVS in sediments are strongly interlinked and suggest that the metabolic processes (e.g., excretion, bio-deposition) and behavioural activities (e.g., particle mixing, bioirrigation) of abundant macrobenthos play an important role in the year-round biogeochemical processes occurring on this flat.     

香港草地、芒萁、灌木群落的C素动态

通过对香港草地、芒萁、灌木群落植物生物量和净生产量的研究,探讨这些植物群落的C素动态。结果表明草地、芒萁、灌木群落植物的C贮量分别为377,871和1448g/m     

Mineral element content in Ulva lactuca L. with reference to eutrophication in Hong Kong coastal waters

The amounts of tissue nitrogen, phosphorus, potassium, sodium, calcium and iron were estimated in the green alga Ulva lactuca L. collected from 9 rural and 14 urban littoral sites in the waters around Hong Kong Island during 1978 and 1979. The mean levels of tissue nitrogen and phosphorus were respectively 65% and 87% more in urban sites than in rural ones. Very significant correlation (r = 0.920) was found between the logarithmic concentration of seawater inorganic nitrogen and that of tissue nitrogen. The same applied to soluble reactive phosphorus in seawater and tissue phosphorus (r = 0.886). The levels of potassium, sodium and calcium in the alga were relatively uniform. However considerable variation in the level of iron was detected. The potential use of Ulva as an indicator species for eutrophication is discussed.     

Vermicomposting in the management of pig-waste in Hong Kong

The treatment and disposal of pig-waste in Hong Kong has received much attention in recent years but, following any of the presently used treatment processes, solids remain to be further stabilized. Vermicomposting is a waste stabilization technique which converts waste into potentially recyclable materials such as worm protein and worm casts. The earthworm, Pheretima asiatica, can stabilize most of the solids arising from the treatment of pig-waste, including raw pig manure, suggesting that vermicomposting has a high potential as a unit process in the management of pig-waste in Hong Kong.S.H. Wong is with the Environmental Protection Department, Hong Kong; and D.A. Griffiths is with the Department of Botany, University of Hong Kong, Hong Kong.     

中国香港17种植物新记录

报道了香港17种植物新记录:无配膜叶铁角蕨[Hymenasplenium apogamum(N.Murak.&Hatan.)Nakaike]、似薄唇蕨(Leptochilus decurrens Blume)、穿心藤[Amydrium hainanense(H.Li,Y.Shiao&S.L.Tseng)H.Li]、毛背...     

Mariculture development in Kenya: alternatives to siting ponds in the mangrove ecosystem

Pond culture of brackishwater prawns and shrimps has recently generated much interest in Kenya. The mangrove areas are the target zones for the construction of these ponds. With the increasing awareness of the unique ecological role played by the mangroves, there is an urgent need to stop the conversion of mangrove swamps into aquaculture ponds. To develop pond aquaculture without destroying the mangroves, a shift from tide-fed to pump-fed pond systems is recommended in order to divert the farming from the mangroves to higher grounds. Mangrove-friendly mariculture practices like pen, cage and raft culture are discussed. Methods of efficiently utilising the already destroyed mangrove areas are considered.     

香港长洲岛野生植物物种多样性与植被的研究

长洲岛共有野生维管植物237种,隶属于73科184属.植被类型以次生常绿阔叶林为主,其次为灌丛群落.植物区系以热带亚热带植物地理成分占优势,热带性质明显.该岛的植物区系与邻近岛屿植物区系具有极大的相似性,在香港植物区系组成中占有一定地位.由于人为活动和外来植物的影响,其植物多样性及植被的保护应引起注意.     

A phylogeographic study of the cosmopolitan genus Phragmites (Poaceae) based on AFLPs

Within the genus Phragmites (Poaceae), the species P. australis (the common reed) is virtually cosmopolitan, and shows considerable variation in ploidy level and morphology. Genetic variation in Phragmites was studied using AFLPs, and analysed with parsimony and distance methods. Groups of P. australis strongly supported in the analyses include one that comprises all South American clones, a distinct group from the US Gulf Coast, and a group of E. Asian and Australian octoploids. Among the other species, the paleotropical P. vallatoria is supported as monophyletic and most closely related to the paraphyletic P. mauritianus and to the Gulf Coast and S. American groups. The E. Asian species P. japonicus is closely related to a group of P. australis clones mostly from central North America. Tetraploidy predominates in the genus, and optimisation of chromosome numbers onto the phylogeny shows that higher ploidy levels have evolved many times.