Early development of algal assemblages under different regimes of physical and biotic factors on a seasonal tropical rocky shore

The roles of physical factors and herbivory in structuring the early development of algal assemblages were investigated on a seasonal, tropical rocky shore in Hong Kong. Physical stress was manipulated by irrigating areas with filtered seawater, whilst herbivore access was controlled using fences. Algal colonisation was monitored at 2 tidal heights (high- and lowshore), once in the cool and dry season and once in the hot and wet season. Dry areas were only colonised in the lowshore and, even when herbivores were excluded, dry highshore areas never developed a macroalgal cover. Algal assemblages did however, develop in highshore irrigated areas where, in the presence of herbivores, encrusting algae (e.g. Hapalospongidion gelatinosum and coralline crusts) developed. In areas excluding herbivores, ephemeral erect algae (e.g. Ulva spp.) developed. All lowshore treatments developed algal assemblages. In the hot season, after an initial phase of erect algae, encrusting algae developed where herbivores had access, whereas, in the cool season, erect Corallina spp. dominated these treatments. In herbivore exclusions, erect ephemeral algae developed in the hot season with a sparse cover of encrusting algae (Ralfsia expansa and coralline crusts) whilst, in the cool season, a cover of Corallina spp. and erect ephemeral algae became abundant. When irrigation was terminated, erect algal cover decreased dramatically in each season in the highshore, although encrusting algae persisted at reduced cover. In lowshore areas, algal cover decreased marginally when irrigation was terminated and only during the hot season. The timing (i.e. hot or cool season) of liberation of rock space was, therefore. important for the development of algal assemblages. In lowshore areas, assemblages dominated by encrusting algae typical of rocky shores in Hong Kong developed only in the presence of herbivores and only during the hot season. During the cool season, Corallina spp. became dominant, while exclusion of herbivores (during either season) resulted in the development of ephemeral, erect algal assemblages.published_or_final_versio

Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll

The Dynamics of Eddy Impacts on Marion’s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planet’s biological diversity

Do factors influencing recruitment ultimately determine the distribution and abundance of encrusting algae on seasonal tropical shores?

Similar to many low-latitude shores, encrusting algae are the dominant space-occupying organisms on moderately exposed rocky shores in Hong Kong. A multifactorial experiment assessed the roles of herbivory, season, tidal height and substratum inclination on the initial recruitment of encrusting algae to artificial surfaces. Herbivores reduced recruit densities at certain times of the year and tidal heights, but did not prevent settlement. In contrast, the relative timing of recruitment and the prevailing environmental conditions greatly affected recruit success. No species recruited at any time to the high shore, and species recruited as high as the mid shore only during cooler months. Species that recruited during the cooler months (e.g. Hapalospongidion gelatinosum and coralline crusts) could colonise the mid shore, while Ralfsia expanse, which recruited primarily during the hot season, was restricted to the low shore and subtidal. Recruitment also varied with substratum inclination; cool-season recruits were found in greater densities on horizontal surfaces, whereas hot-season recruits exhibited no difference between horizontal and vertical plates. Seasonal availability of free space may influence the life-history strategies of encrusting algae. R. expanse recruited during the hot season to the low shore, when free space was available following the annual die-back of algae. In contrast, cool-season recruits (e.g. H. gelatinosum) have less free space to colonise and as a result become established in greater densities higher on the shore, resulting in increased physical stress and mortality during the following hot season. The timing of recruitment relative to spatial and temporal variation in the physical environment, therefore, greatly affects the potential distribution of mature encrusting algal populations on Hong Kong shores.published_or_final_versio

Structure and distribution of the slope fish community in the vicinity of the sub-Antarctic Prince Edward Archipelago

Demersal fish community structure, distribution and trophic relationships on the slope (depth range 200–1500 m) of the sub-Antarctic Prince Edward Islands and surrounding sea rises were investigated during a pilot survey conducted in April 2001 onboard fishing vessel MV Iris. A total of 56 fish taxa were collected during the survey, of which 44 were identified to the species level, seven to the genus level and five to the family level. Among the identified taxa, 36 constituted new records for the area investigated. Total catch per unit effort (cpue) during the survey ranged from 1•1 to 241•2 individuals h 1. Both average fish diversity and total cpue positively correlated with trawling depth. Overall, mean sampling depth and near-bottom temperature explained 56% of total fish cpue. Hierarchal cluster analysis identified three distinct fish assemblages with pronounced dominant species. Major shifts in fish community composition occurred at 500–600 m and 800–900 m depth strata and could probably be a result of physical and biological vertical zonation. Analysis of the diet of selected fish species showed that they were generalist feeders, consuming predominantly pelagic, including epipelagic, meso- and benthopelagic, prey. Diets of six species and nitrogen stable isotope signatures of 22 species revealed that with a few exceptions most fishes occupied the fourth trophic level and were tertiary consumers. Wide variability in carbon isotopic signatures is discussed with respect to alternative, e.g. possible importance of high Antarctic and chemoautotrophic v. photoautotrophic sub-Antarctic primary production, organic matter sources at the base of deep-sea food webs

Factors Affecting Perceived Stigma in Leprosy Affected Persons in Western Nepal

Background There are various factors which construct the perception of stigma in both leprosy affected persons and unaffected persons. The main purpose of this study was to determine the level of perceived stigma and the risk factors contributing to it among leprosy affected person attending the Green Pastures Hospital, Pokhara municipality of western Nepal. Methods A cross-sectional study was conducted among 135 people affected by leprosy at Green Pastures Hospital and Rehabilitation Centre. Persons above the age of 18 were interviewed using a set of questionnaire form and Explanatory Model Interview Catalogue (EMIC). In addition, two sets of focused group discussions each containing 10 participants from the ward were conducted with the objectives of answering the frequently affected EMIC items. Results Among 135 leprosy affected persons, the median score of perceived stigma was 10 while it ranged from 0–34. Higher perceived stigma score was found in illiterate persons (p = 0.008), participants whose incomes were self-described as inadequate (p = 0.014) and who had changed their occupation due to leprosy (p = 0.018). Patients who lacked information on leprosy (p = 0.025), knowledge about the causes (p = 0.02) and transmission of leprosy (p = 0.046) and those who had perception that leprosy is a severe disease (p<0.001) and is difficult to treat (p<0.001) had higher perceived stigma score. Participants with disfigurement or deformities (p = 0.014), ulcers (p = 0.022) and odorous ulcers (p = 0.043) had higher perceived stigma score. Conclusion The factors associated with higher stigma were illiteracy, perceived economical inadequacy, change of occupation due to leprosy, lack of knowledge about leprosy, perception of leprosy as a severe disease and difficult to treat. Similarly, visible deformities and ulcers were associated with higher stigma. There is an urgent need of stigma reduction strategies focused on health education and health awareness programs in addition to the necessary rehabilitation support

Exploitation status of infralittoral abalone (Haliotis midae) and alikreukel (Turbo sarmaticus) in the southern section of the Eastern Cape coast, South Africa

Intertidal size-frequency distributions and densities for Haliotis midae and Turbo sarmaticus were examined at 10 sites experiencing varying pressure of human exploitation along the southern section of the Eastern Cape coast, South Africa. Target species' densities and maximum sizes were related both to the numbers of collectors on the shore and to indirect indicators of exploitation such as number of households in the vicinity and distance to the nearest beach access point. For both species, there was variation in density (P < 0.05) and size (P < 0.05) among sites, with densities ranging between 0.03-2.23 m^(-2) and 0.07-4.93 m^(-2) for H. midae and T. sarmaticus, respectively. Maximum sizes ranged between 49.4-153.5 mm (H. midae) and 28.3-104.4 mm (T. sarmaticus) shell length. Population parameters such as mean maximum size and total density were significantly negatively related to exploitation indicators for both species. In addition, densities of sexually mature and legal-size individuals of T. sarmaticus were significantly negatively related to the number of households. However, only for H. midae were densities of subadults significantly negatively related to the number of collectors, suggesting that reproduction of abalone may be suppressed at the most exploited sites. Exploitation of T. sarmaticus tends to be localized near population centres, whereas H. midae is collected over a larger range of sites. Overall, T. sarmaticus is less affected by exploitation than H. midae

Physical and biological coupling in eddies in the lee of the South-West Indian Ridge

Eddies have some decisive functions in the dynamics of the Southern Ocean ecosystems. This is particularly true in the Indian sector of the Southern Ocean, where a region of unusually high-mesoscale variability has been observed in the vicinity of the South-West Indian Ridge. In April 2003, three eddies were studied: eddy A, a recently spawned anticyclone south of the Antarctic Polar Front (APF),; eddy B, an anticyclone north of lying between the Subantarctic Front and the APF; and eddy C, a cyclone north of the APF west of the ridge. Elevated concentrations of total Chl-a coincided with the edges of the cyclonic eddy, whereas both anticyclonic eddies A and B were characterised by low total Chl-a concentrations. Biologically, the two anticyclonic eddies A and B were distinctly different in their biogeographic origin. The zooplankton community in the larger anticyclonic eddy A was similar in composition to the Antarctic Polar Frontal Zone (APFZ) community with an addition of some Antarctic species suggesting an origin just north of the APF. In contrast, the species composition within the second anticyclonic eddy B appeared to be more typical of the transitional nature of the APFZ, comprising species of both subantarctic and subtropical origin and thus influenced by intrusions of water masses from both north and south of the Subantarctic Front. Back-tracking of these features shows that the biological composition clearly demarcates the hydrographic origin of these features

Freezing and chemical preservatives alter the stable isotope values of carbon and nitrogen of the Asiatic clam (Corbicula fluminea)

We tested the impacts of most common sample preservation methods used for aquatic sample materials on the stable isotope ratios of carbon and nitrogen in clams, a typical baseline indicator organism for many aquatic food web studies utilising stable isotope analysis (SIA). In addition to common chemical preservatives ethanol and formalin, we also assessed the potential impacts of freezing on δ¹³C and δ¹⁵N values and compared the preserved samples against freshly dried and analysed samples. All preservation methods, including freezing, had significant impacts on δ¹³C and δ¹⁵N values and the effects in general were greater on the carbon isotope values (1.3-2.2% difference) than on the nitrogen isotope values (0.9-1.0% difference). However, the impacts produced by the preservation were rather consistent within each method during the whole 1 year experiment allowing these to be accounted for, if clams are intended for use in retrospective stable isotope studies

Domain Wall Fermions in Quenched Lattice QCD

We study the chiral properties and the validity of perturbation theory for domain wall fermions in quenched lattice QCD at beta=6.0. The explicit chiral symmetry breaking term in the axial Ward-Takahashi identity is found to be very small already at Ns=10, where Ns is the size of the fifth dimension, and its behavior seems consistent with an exponential decay in Ns within the limited range of Ns we explore. From the fact that the critical quark mass, at which the pion mass vanishes as in the case of the ordinary Wilson-type fermion, exists at finite Ns, we point out that this may be a signal of the parity broken phase and investigate the possible existence of such a phase in this model at finite Ns. The rho and pi meson decay constants obtained from the four-dimensional local currents with the one-loop renormalization factor show a good agreement with those obtained from the conserved currents

The finite temperature QCD phase transition with domain wall fermions

The domain wall formulation of lattice fermions is expected to support accurate chiral symmetry, even at finite lattice spacing. Here we attempt to use this new fermion formulation to simulate two-flavor, finite temperature QCD near the chiral phase transition. In this initial study, a variety of quark masses, domain wall heights and domain wall separations are explored using an 8^3 x 4 lattice. Both the expectation value of the Wilson line and the chiral condensate show the temperature dependence expected for the QCD phase transition. Further, the desired chiral properties are seen for the chiral condensate, suggesting that the domain wall fermion formulation may be an effective approach for the numerical study of QCD at finite temperature.Comment: 44 pages, 15 figure