bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of human infection by Leishmania spp. in the Northwest of Argentina: immune response, double infection with Trypanosoma cruzi and species of Leishmania involved
Authors: FRANK F. M. , FERNÁNDEZ M. M. , TARANTO N. J. , CAJAL S. P. , MARGNI R. A. , CASTRO E. , THOMAZ-SOCCOL V. , MALCHIODI E. L.
Published: March 2003

The aims of this study were to characterize human American tegumentary leishmaniasis, which includes cutaneous, mucocutaneous and mucosal leishmaniasis, in Northwest Argentina, to determine the prevalence of double infection with Trypanosoma cruzi and to identify the species of Leishmania in this area. Most of the 330 leishmaniasis patients presented cutaneous ulcers (96·1%), 2·4% mucocutaneous and 1·5% the mucosal form (‘espundia’). The aetiological agents, determined by isoenzyme electrophoresis, were identified as Leishmania (Viannia) braziliensis in 16 out of 20 isolates and in the remaining 4 as Leishmania (Leishmania) amazonensis, the first ever-documented in Argentina. Sera analysed by ELISA and IFA using complex antigen from both T. cruzi and L. braziliensis showed a very high percentage of positives (66·3–78·2%). When antigens for specific diagnosis of Chagas' disease were used, 40·9% of the leishmaniasis patients were also found to be infected by T. cruzi. These results indicate that the strong immune response against T. cruzi gave no protection to Leishmania, in spite of the serological cross-reaction between these parasites. In addition, we showed that more than 40% of the patients would be misdiagnosed as chagasic if complex antigens, as epimastigotes or soluble fraction from epimastigotes, were used in IFA or ELISA. This is of paramount importance not only because patients' treatment would be associated to misdiagnosis but the fact that in many countries in Central and South America, a positive test for Chagas' disease means a rejection for those seeking employment.
Occurrence of intermediate hosts and structure of digenean communities of the black-headed gull, Larus ridibundus (L.)
Authors: šIMKOVÁ A. , SITKO J. , OKULEWICZ J. , MORAND S.
Published: March 2003

The factors contributing to the similarity between digenean parasite assemblages parasitizing the black-headed gull were investigated. Thirteen different digenean species from the digestive tract and the bursa of Fabricus were found. We predicted that the structure of parasite communities is not random at either component community or infracommunity levels. We searched for nested patterns in the digenean community, and explored the possible factors contributing to nestedness. We found that digenean species which occupy a narrow range of intermediate hosts are placed out of order in the nested matrix. The influence of several variables related to the water reservoir, geographical distances, and the abundance of intermediate hosts on the species diversity and similarity of parasite communities were tested as well. Because of the complexity in bird digenean life-cycles we supposed that intermediate hosts and ecological characters of their environment could play a major role. We showed that the presence of intermediate hosts is the factor limiting the qualitative and quantitative similarity of parasite communities among different host populations as well as influencing the digenean species diversity in the definitive host. The similarity in abundance of intermediate hosts between different localities was facilitated by the presence of vegetation in water reservoir and more diversified type of water bottom. Digenean species diversity was higher when the water reservoir was exposed to temporal drying. We hypothesized that this factor could facilitate the inclusion of molluscs infected by digeneans in the diet of birds. Both species diversity and dominance were influenced by the bottom type of water reservoir and temporal drying up. Geographical distances between localities influenced the quantitative similarity of digenean communities as well as species richness.
The effect of the anthelmintic emodepside at the neuromuscular junction of the parasitic nematode Ascaris suum
Authors: WILLSON J. , AMLIWALA K. , HARDER A. , HOLDEN-DYE L. , WALKER R. J.
Published: March 2003

Here we report on the action of the novel cyclo-depsipeptide anthelmintic, emodepside, on the body wall muscle of the parasitic nematode, Ascaris suum. Emodepside caused (i) muscle relaxation, (ii) inhibition of muscle contraction elicited by either acetylcholine (ACh), or the neuropeptide, AF2 (KHEYLRFamide) and (iii) a rapid relaxation of muscle tonically contracted by ACh. The inhibitory action of emodepside on the response to ACh was not observed in a denervated muscle strip, indicating that it may exert this action through the nerve cord, and not directly on the muscle. Electrophysiological recordings showed emodepside elicited a Ca++-dependent hyperpolarization of muscle cells. Furthermore, the response to emodepside was dependent on extracellular K+, similar to the action of the inhibitory neuropeptides PF1 and PF2 (SDPNFLRFamide and SADPNFLRFamide). Thus emodepside may act at the neuromuscular junction to stimulate release of an inhibitory neurotransmitter or neuromodulator, with a similar action to the PF1/PF2 neuropeptides.
Sequence heterogeneity of the small subunit ribosomal RNA genes among Blastocystis isolates
Authors: ARISUE N. , HASHIMOTO T. , YOSHIKAWA H.
Published: March 2003

Genes encoding small subunit ribosomal RNA (SSUrRNA) of 16 Blastocystis isolates from humans and other animals were amplified by the polymerase chain reaction, and the corresponding fragments were cloned and sequenced. Alignment of these sequences with the previously reported ones indicated the presence of 7 different sequence patterns in the highly variable regions of the small subunit ribosomal RNA. Phylogenetic reconstruction analysis using Proteromonas lacertae as the outgroup clearly demonstrated that the 7 groups with the different sequence patterns are separated to form independent clades, 5 of which consisted of the Blastocystis isolates from both humans (B. hominis) and other animals. The presence of 3 higher order clades was also clearly supported in the phylogenetic tree. However, a relationship among the 4 groups including these 3 higher order clades was not settled with statistical confidence. The remarkable heterogeneity of small subunit ribosomal RNAs among different Blastocystis isolates found in this study confirmed, with sequence-based evidence, that these organisms are genetically highly divergent in spite of their morphological identity. The highly variable small subunit ribosomal RNA regions among the distinct groups will provide useful information for the development of group-specific diagnostic primers.
Is body size or activity of copepods related to ingestion of parasite larvae?
Authors: VAN DER VEEN I. T.
Published: March 2003

This study shows that ingestion of Schistocephalus solidus coracidia was related to general activity of Macrocyclops albidus copepods at the time of exposure. The lower the activity of the host, the fewer parasites it ingested. In an earlier study it was shown that large M. albidus copepods were less likely to become infected with S. solidus than small copepods, which could potentially be caused by differential ingestion of parasites. However, the current study did not show any evidence for such an effect arising through differential ingestion. Body size was not related to ingestion of parasites, but was positively correlated to activity. So, even though size did not significantly relate to ingestion of parasites, if anything, through their higher activity large copepods rather than small copepods may have ingested more parasites. This study indicates that differences in resistance to this parasite do not come about through differential ingestion of parasites. Also, an earlier study failed to show differential elimination of the parasite from the haemocoel. This leaves avoidance of penetration through the gut wall as the most plausible candidate causing large copepods to be more resistant to this parasite than small copepods.
Fasciola hepatica: surface and internal tegumental changes induced by treatment in vitro with the sulphoxide metabolite of albendazole (‘Valbazen’)
Authors: BUCHANAN J. F. , FAIRWEATHER I. , BRENNAN G. P. , TRUDGETT A. , HOEY E. M.
Published: March 2003

A morphological study has been carried out to determine the effect of the active sulphoxide metabolite of the benzimidazole anthelmintic, albendazole (ABZ-SO) on the adult liver fluke, Fasciola hepatica. Whole flukes were treated with ABZ-SO for 12 and 24 h at a concentration of 10 μg/ml. The changes in response to drug treatment were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tubulin immunocytochemistry (ICC). No surface changes were apparent following 12 h ABZ-SO treatment, but localized blebbing was observed after 24 h, which became more extensive towards the posterior region of both surfaces. TEM of sections from the posterior midbody region revealed that ABZ-SO caused the accumulation of secretory bodies in the tegumental cells and in their cytoplasmic connections and, after 24 h, just above the basal plasma membrane. Localized blebbing of the apical membrane also occurred. The morphology of the Golgi complexes within the tegumental cells began to change after 12 h treatment with ABZ-SO and, by 24 h, few complexes were observed. A distinct increase in tubulin immunoreactivity occurred after 12 h treatment, but this decreased after 24 h. The results obtained are consistent with those expected for microtubule inhibition. They are discussed in relation to the action of established microtubule inhibitors, as well as the benzimidazole derivative, triclabendazole.
Delayed tail loss during the invasion of human skin by schistosome cercariae
Authors: WHITFIELD P. J. , BARTLETT A. , KHAMMO N. , BRAIN A. P. R. , BROWN M. B. , MARRIOTT C. , CLOTHIER R.
Published: March 2003

Schistosomiasis is initiated when cercarial larvae invade human skin. Contrary to long-held assumptions, most cercariae of Schistosoma mansoni do not shed their propulsive tails as they penetrate. Scanning electron microscopy studies and infection experiments with entire human skin and differentiated, stratum corneum-like, human keratinocyte cultures, have shown that most cercarial tails enter the skin along with their bodies. We propose that this behaviour is an adaptive trait linked with concomitant immunity.
Philasterides dicentrarchi (Ciliophora: Scuticociliatida) expresses surface immobilization antigens that probably induce protective immune responses in turbot
Authors: IGLESIAS R. , PARAMÁ A. , ÁLVAREZ M. F. , LEIRO J. , UBEIRA F. M. , SANMARTÍN M. L.
Published: March 2003

Philasterides dicentrarchi is a histophagous ciliate causing systemic scuticociliatosis in cultured turbot. This study demonstrates that turbot which survive this disease have serum antibodies that recognize ciliary antigens of this ciliate in ELISA and immobilize/agglutinate the ciliate in vitro. Mouse sera raised against ciliary antigens and integral membrane proteins are likewise capable of immobilizing/agglutinating the ciliates, indicating that P. dicentrarchi, like other ciliates, expresses surface immobilization antigens. Furthermore, the antigen agglutinating reaction induces the parasite to shed its surface antigens rapidly, replacing them with others with different specific serology. This antigen shedding and variation response is similar to that detected in other protozoan parasites. Immunization of turbot with ciliate lysate plus adjuvant or with formalin-fixed ciliates induced synthesis of agglutinating antibodies and conferred a degree of protection against challenge infection, suggesting that the response to surface antigens may play an important role in defence against this pathogen, SDS–PAGE and immunoblotting studies indicated the existence of a predominant polypeptide of about 38 kDa in the ciliary antigen and membrane protein fractions, and this may be the principal surface antigen of P. dicentrarchi.
Hookworm cathepsin D aspartic proteases: contributing roles in the host-specific degradation of serum proteins and skin macromolecules
Authors: WILLIAMSON A. L. , BRINDLEY P. J. , LOUKAS A.
Published: March 2003

Cathepsin D aspartic proteases of hookworms were recently implicated in the host-specific digestion of haemoglobin by adult parasites. Ac-APR-1 from the dog hookworm, Ancylostoma caninum and Na-APR-1 from the human hookworm, Necator americanus, were shown to be expressed in the infective larval stage (L3) as well as adult worms. We now show that both proteases degraded skin macromolecules and serum proteins, some of which were cleaved more readily from permissive definitive hosts as opposed to non-permissive hosts. Na-APR-1 degraded human collagens more efficiently than did Ac-APR-1, and Ac-APR-1 degraded canine serum albumin more efficiently than did Na-APR-1. On the other hand, both enzymes degraded human serum proteins (albumin and fibrinogen) with approximately equal efficiency under the conditions of our assays in vitro. Molecular models of these 2 orthologous, aspartic proteases showed that, despite having active site clefts with identical primary sequences, residues in the S3 pocket adopted different conformations, likely accounting for different substrate preferences reported previously. Antisera raised to both proteases partially inhibited (16–26%) migration of hookworm L3 through hamster skin in vitro, further implying a connective tissue invasive role for these enzymes in addition to digestion of serum and erythrocyte proteins for nutrition.
Secreted adhesion molecules of Strongyloides venezuelensis are produced by oesophageal glands and are components of the wall of tunnels constructed by adult worms in the host intestinal mucosa
Authors: MARUYAMA H. , EL-MALKY M. , KUMAGAI T. , OHTA N.
Published: March 2003

The parasitic female of Strongyloides venezuelensis keeps invading the epithelial layer of the host intestinal mucosa. Upon invasion, it adheres to the surface of the intestinal epithelial cells with adhesion molecules secreted from the mouth. It has been demonstrated that S. venezuelensis are expelled from the intestine because mucosal mast cells inhibit the attachment of adult worms to the mucosal surface. In the present study, we generated specific antibodies against secreted adhesion molecules to investigate their function in vivo, because these molecules have been demonstrated only in vitro in spite of the importance in the infection processes. A mouse monoclonal antibody specific to S. venezuelensis adhesion molecules inhibited the attachment of adult worms to plastic dishes and the binding of adhesion molecules to rat intestinal epithelial cells. Immunohistochemical study revealed that adhesion molecules were produced by oesophageal glands and were continuously secreted in vivo to line the wall of the tunnels formed by adult worms in the intestinal mucosa. Our findings indicate that adhesion molecules play essential roles in the infection processes of S. venezuelensis in the host intestine.
A Boophilus microplus vitellin-degrading cysteine endopeptidase
Authors: SEIXAS A. , DOS SANTOS P. C. , VELLOSO F. F. , DA SILVA VAZ I. , MASUDA A. , HORN F. , TERMIGNONI C.
Published: March 2003

Here we describe the purification and characterization of a vitellin (VT) degrading cysteine endopeptidase (VTDCE) from eggs of the hard tick Boophilus microplus. A homogeneous enzyme preparation was obtained by chromatographic fractionation on ion-exchange and gel filtration columns and an autolysis step. This step consisted of incubation of a semipurified enzyme (after the first ion-exchange chromatography) at pH 4·0 that dissociated the enzyme from VT, to which VTDCE is naturally tightly associated. The enzyme purity was confirmed by capillary and native gel electrophoresis, and SDS–PAGE suggested the enzyme is a dimer of 17 and 22 kDa. VTDCE was active upon several synthetic substrates, with a preference for a hydrophobic or a basic residue in P1, and a hydrophobic residue in P2. VTDCE also hydrolysed haemoglobin, albumin, gelatin and vitellin. VTDCE is inactive in the absence of DTT and was totally inhibited by E-64, indicating it is a cysteine endopeptidase. Our results suggest that VTDCE is a major enzyme involved in yolk processing during B. microplus embryogenesis.
The molecular evidence of Babesia microti infection in small mammals collected in Slovenia
Authors: DUH D. , PETROVEC M. , TRILAR T. , AVSIC-ZUPANC T.
Published: March 2003

In Europe, the zoonotic cycle of Babesia microti has not been determined so far. Recently, B. microti was detected in Ixodes ricinus ticks in Slovenia by using molecular methods. In order to investigate the mammalian hosts of B. microti in Slovenia we collected 261 small mammals representing 11 species. They were tested for the presence of babesial parasites with a PCR assay based on the nuclear small subunit rRNA gene (nss-rDNA). The bank vole (Clethrionomys glareolus) and yellow-necked mouse (Apodemus flavicollis) were infected with B. microti. The prevalence rate was 15·9% for C. glareolus and 11·8% for A. flavicollis. Nucleotide sequences of amplified portions of B. microti nss-rDNA from C. glareolus and A. flavicollis were indistinguishable from each other and identical with those previously described in I. ricinus ticks collected in Slovenia. The results of this study represent molecular evidence of B. microti in small mammals in Europe.
Determination of parameters of 3-dof spatial orientation manipulators for a
specified workspace
Authors: Kosinska A. , Galicki M. , Kedzior K.
Published: March 2003

The objective of the paper is to present a method of designing geometrical parameters of 3-dof orientation mechanisms. The parameters are to be determined for a given workspace, which in this case is described as a set of angles of
orientation. An algorithm is presented, based on the equations of constraints which makes it
possible to obtain the parameters of a manipulator. whose workspace involves the specified
taskspace.
Noncollocated passivity-based PD control of a single-link flexible manipulator
Authors: Liu Liang-Yih , Yuan King
Published: March 2003

The passivity property of a noncollocated single-link flexible manipulator with a parameterized output is studied. The system can be characterized by either the irrational transfer function of an infinite-dimensional model or its truncated rational transfer functions. Necessary and sufficient conditions for these transfer functions to be passive are found. It is also shown that a non-passive, marginal minimum-phase, truncated transfer function can be rendered passive by using either the root strain feedback or the joint angular acceleration feedback. For the noncollocated truncated passive transfer function, a PD controller suffices to stabilize the overall system. Numerical results are given to show the efficacy of the proposed approaches.
Effects of terrain irregularities on wheeled mobile robot
Authors: Prado Maria , Simón Antonio , Pérez Ana , Ezquerro Francisco
Published: March 2003

The influence of ground irregularities on the behavior of a wheeled mobile robot (WMR) navigating on uneven surfaces is addressed. The paper studies the vibratory movements induced on the body of the WMR, in order to analyze its ability
for carrying out on-board tasks, and on the accuracy of the data collected by its external sensorial systems. The adhesion capability of the wheels of the WMR on this uneven
terrain is also studied, since it conditions the braking, traction and steering performance. The method is applied to the WMR RAM.
Time suboptimal control of industrial manipulators along specified paths while
keeping an end-effector orientation unchanged
Authors: Kilicaslan S. , Ercan Y.
Published: March 2003

A method for the time suboptimal control of an industrial manipulator that moves along a specified path while keeping its end-effector orientation unchanged is
proposed. Nonlinear system equations that describe the manipulator motion are linearized at each time step along the path. A method which gives control inputs (joint angular velocities) for time suboptimal control of the manipulator is developed. In the formulation, joint
angular velocity and acceleration limitations are also taken into consideration. A six degree of freedom elbow type manipulator is used in a case study to verify the method developed.
Dynamic modelling of a compliant arm with 6-dimensional tip forces
using screw theory
Authors: Ding X. , Selig J. M.
Published: March 2003

In this paper, we try to find an efficient and accurate dynamic
model for a robot with spatial compliant links using the screw theory. After making some reasonable assumptions for the system, we introduce the Ding-Holzer method for system simplification. Instead of looking at the beam at rest, we consider the spatial forces and deflections of a moving elastic arm. We focus our study on the dynamic modelling problems of a compliant arm with six dimensional forces and deformations at the tip.
A contribution to minimum-time task-space path-following problem for redundant manipulators
Authors: Basile Francesco , Chiacchio Pasquale
Published: March 2003

The minimum-time path-following problem for non-redundant manipulator has already been analyzed and a number of efficient solution algorithms have been proposed. These algorithms can be applied also to redundant manipulators if the path is assigned in the joint space. If the path is assigned in the task space instead, how to exploit kinematic redundancy to reduce the execution time is still an open problem. In this paper it
is proposed to follow a heuristic approach to choose between different solutions to the inverse kinematics problem that underlies the minimum-time path-following control problem. The aim is to obtain a joint-space path which configures the manipulator so as to improve
acceleration/deceleration capabilities of the end-effector. This is obtained by penalizing
the motion of joints with higher inertia-to-torque ratios. Numerical results are presented for an “easy-to-understand” three degree-of-freedom planar manipulator involved
in two-dimensional paths.
Generating globally optimised sagittal gait cycles of a biped robot
Authors: Saidouni Tarik , Bessonnet Guy
Published: March 2003

The paper is aimed at generating optimal gait cycles in the sagittal plane of a biped, the locomotion system of which has anthropomorphic characteristics. Both single and double support phases are globally optimised, considering incompletely specified transition postural configurations from one phase to the other. An impactless heel-touch is prescribed. Full dynamic models are developed for both gait phases. They are completed by specific constraints attached to the unilaterality of contact with the supporting
ground.

A parametric optimisation method is implemented. The biped joint coordinates are approximated by cubic splines functions connected at uniformly distributed knots along the motion time. The finite set of unknowns consists of the joint coordinate values at knots, some gait pattern parameters at phase transitions, and the motion time of each phase. The step length is adjusted to the prescribed gait speed by the optimisation process. Numerical simulations concerning slow and fast optimal gaits are presented and discussed.
The study of auditory and haptic signals in a virtual
reality-based hand rehabilitation system
Authors: Shing Chang-Yih , Fung Chin-Ping , Chuang Tien-Yow , Penn I-Wen , Doong Ji-Liang
Published: March 2003

The purpose of the present study is to assess the influence of auditory and haptic signals on the manipulation performance in a virtual reality-based hand rehabilitation system. A personal computer, a tracker, and a data glove were included in this system. Three-dimensional virtual environments were developed. Forty volunteers were recruited to participate in a pick-and-place procedure, with three levels of difficulty and four feedback modes. Task time and collision frequency were the parameters used to evaluate
their manipulation performance. It can be concluded that the haptics is a significant signal for improving a subject's performance at the high difficulty level.
A joint trajectory generator for motion recovery
Authors: Li Wei , Red Edward
Published: March 2003

This paper describes an adaptive S-curve used to recover a tool path upon a system crash in the Windows operating system (OS). For a mechanism such as a robot or machine tool, the joint values, being delivered as setpoints to the servo-controller, are dynamically recorded by the real-time operating system also residing on the computer. The real-time OS can control the abort and record pertinent motion data after Windows OS crash.

Upon system recovery, the recovery trajectory generator examines the setpoints intervals to determine the current slow joint. At every trajectory step, and for the current slow joint, the S-curve velocity profile applies the joint entry state (position, speed, acceleration, and jerk) to interpolate the motion between the setpoints in a reverse direction. The other joints are proportionally interpolated (slowed) so that they pass through each setpoint simultaneously with the slow joint, but in a reverse direction.

The trajectory algorithm is optimal since the slow joint always uses the maximum allowable jerk to change the profile speed and acceleration for each trajectory step.
Tracking sequestered carbon in the timber trade
Authors: Blundell Arthur G.
Published: March 2003

The most recent meeting discussing the Kyoto Protocol focused on market-based mechanisms to reduce greenhouse gases. This could pave the way for initiatives that allow polluters to offset their emissions if they buy carbon sequestered through reforestation (Sandalow & Bowles 2001). But rather than lose credit when the trees are harvested, investors must continue to track the sequestered carbon once trees become timber. I examined trade statistics for the best-tracked timber species, namely mahogany, Swietenia macrophylla King (Meliaceae). Although mahogany is regulated by one of the most restrictive trade agreements, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), I found discrepancies in USA trade statistics of c. 30%, representing c. US$ 100 million over the last 4 years. For comparison, I also calculated differences in trade data for all sawnwood, according to the United Nations Food and Agricultural Organization (FAO); discrepancies between USA and exporter reports were c. 38%. Large accounting problems must be solved before sequestered carbon should become a globally traded commodity.
Funds for biodiversity
Authors: Gössling Stefan
Published: March 2003

A number of recent publications have pointed out the accelerating speed at which ecosystems and biodiversity are being lost (United Nations Development Programme/United Nations Environment Programme/The World Bank/The World Resources Institute 2000). The general view is that conservation can only be achieved in a global network of protected areas (see Pimm et al. 2001). To safeguard the most important ecosystems, Myers et al. (2000) have suggested that we primarily conserve 25 biodiversity hotspots, in particular forests, comprising 1.4% of the land surface of the Earth. The costs for the conservation of these hotspots have been estimated at US$ 500 million per year (Myers et al. 2000), while the costs of a global network of protected areas may even reach US$ 27.5 billion per year (James et al. 1999). Even though these costs may seem minor compared to, for example, the costs of global armament, governments in developing countries and environmental organizations are clearly not in the position to finance conservation. It is thus urgent to raise additional funds to safeguard biodiversity. In the following, I suggest a twofold strategy, based on tourism.
Long-term environmental trends and the future of tropical wetlands
Authors: Junk Wolfgang J.
Published: March 2003

Tropical wetlands assume important functions in the landscape and contribute considerably to the welfare of large parts of the human population, but they are seriously threatened because they are considered free resources of land and water. This review summarizes long-term environmental trends for tropical wetlands and predicts their future to the time horizon 2025. Many tropical countries do not have the economic strength, scientific and technological capacity, and/or administrative infrastructure to adequately react to the challenges of increasing population pressure and globalization of the economy with respect to the sustainable use of the resources. Furthermore, political instability and armed conflicts affect large areas in several tropical countries, hindering wetland research and management. Detailed wetland inventories are missing in most countries, as are plans for a sustainable management of wetlands in the context of a long-term integrated watershed management. Despite large regional variability, a continental ranking shows, in decreasing order of wetland integrity, South America, Africa, Australia and Asia, while efforts to mitigate human impacts on wetlands are largest and most advanced in Australia. Analysis of demographic, political, economic and ecological trends indicates fairly stable conditions for wetlands in tropical Australia, slight deterioration of the large wetland areas in tropical South America excepting the Magdalena and Cauca River flood plains where human population is larger, rapidly increasing pressure and destruction on many African and Central American wetlands and serious threats for the remaining wetlands in tropical Asia, by the year of 2025. Policy deficiencies, deficient planning concepts, limited information and awareness and institutional weakness are the main administrative reasons for wetland degradation and must be overcome to improve wetland management and protection in future. Intensification of international cooperation and assistance is considered of fundamental importance for most tropical countries to solve problems related to wetland research, protection and sustainable management.
The near future of coral reefs
Authors: McClanahan Timothy R.
Published: March 2003

In this paper the current status of coral reefs, predictions concerning the ecological state of coral reefs to the 2025 time horizon and the research needs that can help understanding and management activities that might alleviate detrimental ecological changes are evaluated and discussed. The present rate of CO2 emissions will produce an atmospheric concentration in 100 years not experienced during the past 20 million years and water temperatures above those of the past interglacial 130 000 years before present. Human influences on water temperatures, seawater chemistry (toxic substances, nutrients and aragonite saturation), the spread of diseases, removal of species and food web alterations are presently changing reef ecology. A significant ecological reorganization is underway and changes include a reduction in calcifying and zooxanthellae-hosting organisms, their obligate symbionts, and species at higher trophic levels, with an increase in generalist species of low trophic level that are adapted to variable environments. Late-successional fleshy brown algae of low net productivity or non-commercial invertebrates such as sea urchins, starfish and coral-eating snails will dominate many reefs. These changes will be associated with a loss of both net benthic and fisheries production and inorganic carbonate deposition; this will reduce reef complexity, species richness, reef growth and increase shoreline erosion. To avert these changes management is needed at both global and local levels. Both levels need to reduce greenhouse gases and other waste emissions and renew efforts to improve resource management including restrictions on the use of resources and globalization of resource trade, run-off and waste production, and balancing potential reef production and resource consumption.
Species-specific impacts of a small marine reserve on reef fish production and fishing productivity in the Turks and Caicos Islands
Authors: Tupper Mark , Rudd Murray A.
Published: March 2003

Marine reserves are widely considered to potentially benefit reef fisheries through emigration, yet the empirical basis for predicting the extent of this for small reserves is weak. The effects of fishing pressure and habitat on biomass and catch per unit effort (CPUE) of three species of exploited reef fish were studied at South Caicos, Turks and Caicos Islands. Distribution and abundance of hogfish (Lachnolaimus maximus) and white margate (Haemulon album) were inversely correlated with cover of fleshy macroalgae. Nassau grouper (Epinephelus striatus) were positively associated with vertical relief, but were unaffected by algal cover. Mean size, density, and biomass of hogfish were higher in a small (4 km2) marine reserve than on fished reefs, as was biomass of white margate. CPUE of hogfish was inversely related to distance from the centre of the reserve, suggesting that spillover of this species from the reserve to adjacent reefs may enhance local yields, possibly providing economic incentives for fishers to comply with reserve regulations. Fishing pressure, however, had no apparent effect on Nassau grouper. Larger fishes and those that migrate to spawn, such as economically valuable Nassau grouper, may move over too large a range to be effectively protected by small marine reserves. Small reserves may not protect all fish, but they can increase the biomass of smaller or more sedentary reef fishes and may be a useful tool for the conservation or management of species such as hogfish. Other policy options, such as seasonal spawning closures or total allowable catches, need to be considered for larger, more mobile fishes in the Turks and Caicos Islands.
Voluntary management in an inshore fishery has conservation benefits
Authors: Blyth Robert E. , Kaiser Michel J. , Edwards-Jones Gareth , Hart Paul J.B.
Published: March 2003

The management of fisheries in European Union (EU) waters has generally been regulated through government institutions and agreed quota allocations. This top-down management approach may have contributed to the continued decline of targeted fish stocks by forcing fishers to compete for limited resources without engendering a sense of resource stewardship. In attempting to reverse this decline, scientists and managers should examine management systems that do not solely depend on top-down approaches, and the Inshore Potting Agreement (IPA) is an example. The IPA is a voluntary fishery management system designed and operated by inshore fishers of south Devon, England. The IPA was conceived to reduce conflict between static-gear (pot and net) and towed-gear (trawl and dredge) fishers, and is regarded as a successful fisheries management regime by fishers and managers because it has effectively allowed fishers from both sectors to operate profitably on traditional fishing grounds. Another study determined that the IPA has incidentally protected benthic habitat complexity. Fishers from the static-gear and towed-gear sectors were interviewed to determine the evolution and function of the IPA, and to establish the factors that ensure the high level of regulatory compliance amongst fishers from both sectors. Towed-gear fishers gave significantly different responses to the same questions asked of static-gear fishers, and were generally less satisfied with the existence of the IPA. Multivariate analyses of the interview data suggested that fishers who thought the IPA was a good system also thought the system provided pot protection, but had experienced inter-sector conflict. Fishers who thought the IPA provided no personal benefit also thought that static-gear fishers should be more restricted, and that towed-gear corridors or more seasonal-use areas should be established within the existing IPA area. However, fishers from both sectors agreed that the IPA has maintained traditional practices of the local fishing industry, and that the system has conserved target finfish and scallop species. A number of factors were identified as critical to the success of the IPA. These included the voluntary nature of the agreement, the limited number of organizations representing fishers and very high level of membership of those organizations, and the simplicity of the system. Regulatory compliance is enhanced through the ability of fishers' organizations to respond rapidly to inter-sector conflict issues.
Attitudes of coastal-forest users in Eastern Cape Province to management options arising from new South African forest policies
Authors: Obiri John A.F. , Lawes Michael J.
Published: March 2003

New participatory forest management policies are being promoted in South Africa involving devolution from the state to local communities at a time when traditional authority has been eroded and is weak. Here, attitudes of forest stakeholders (forest resource users and managers) to three possible forest management policies, as well as to resource use, were investigated using questionnaires. There was concordance in the attitudes of resource users and managers and a general lack of support for community forest management (CFM), particularly among older resource users. Power shifts, uncertainty about land tenure and the management of what has essentially become an open-access system, all confound attempts to implement community-based forestry programmes. Local communities appeared to be wary of taking on responsibility for forest management at this time and indicated comparatively stronger support for state forest management (SFM). Forest stakeholders were more equivocal in their support for participatory forest management (PFM), although this probably reflects a poor understanding by forest users of the new PFM process. No stakeholders supported a total ban on forest resource use, but all supported controlled use. These latter attitudes were independent of the preferred management system (i.e. CFM, SFM or PFM). This study corroborates the view that CFM has been overemphasized. Rather than narrowing forest management around communities, but recognizing the state's incapacity to ensure the integrity of forest resources into the future without the co-operation of forest users, an all-inclusive approach, such as PFM, provides for greater management input by the state.
Tenure and forest conditions: community forestry in the Nepal Terai
Authors: Nagendra Harini
Published: March 2003

There is a current trend towards decentralization of forest management, particularly among developing nations. Nepal has taken a lead in initiating innovative policies of community forestry. Although these initiatives have been largely deemed successful in the mountains, within the Terai lowlands, there is considerable debate about their outcomes. This research evaluates forest condition within recently declared community forests, national forests and protected areas in the Nepal Terai, using plot mensuration techniques and interviews with local users. The initial condition of forests that were handed over to local communities for use was significantly poorer than those retained as national forests. Protected areas had the highest levels of plant abundance, biomass and biodiversity, which is not surprising, given the level of funds and manpower input to managing these limited areas. In the context of current controversy about the outcome of community forestry in the Nepal Terai, the poor initial condition of forests handed over to local communities is highly significant, and needs to be factored into evaluations of community forest management. This research underscores the need for benchmark studies for evaluating the future outcomes of forest policies in the Terai, provides a valuable addition to the limited information on forest conditions under different management regimes in Nepal, and indicates some of the difficulties that local communities face while dealing with community forestry in practice.
Seasonal variation in circulation and water mass distribution on
the Ross Sea continental shelf
Authors: ASSMANN K. , HELLMER H.H. , BECKMANN A.
Published: March 2003

Changes in water mass distribution and horizontal circulation due to seasonal influences on the
Ross Sea continental shelf are investigated using a circumpolar numerical model. An anticyclonic
circulation cell that extends across the open shelf and into the ice shelf cavity is formed in the model. The
increased east–west density gradient caused by the strong brine release in the Ross Sea polynya in winter
results in an intensification of this anticyclonic cell from 1.5 Sv to 2.5 Sv. This supports the concept of a
thermohaline-driven horizontal circulation on the Ross Sea continental shelf. In addition to a temporal
change in the circulation strength, the changes in the density structure lead to complex temporal and spatial
variability in the circulation around Ross Island. Due to seasonal variation in circulation strength and water
temperatures, the area averaged basal melt rate of 25 cm a−1 shows a bimodal seasonal cycle ranging from
20–28 cm a−1, with maxima in March and August.
Modelling the ocean circulation beneath the Ross Ice Shelf
Authors: HOLLAND DAVID M. , JACOBS STANLEY S. , JENKINS ADRIAN
Published: March 2003

We applied a modified version of the Miami isopycnic coordinate ocean general circulation
model (MICOM) to the ocean cavity beneath the Ross Ice Shelf to investigate the circulation of ocean waters
in the sub-ice shelf cavity, along with the melting and freezing regimes at the base of the ice shelf. Model
passive tracers are utilized to highlight the pathways of waters entering and exiting the cavity, and output is
compared with data taken in the cavity and along the ice shelf front. High Salinity Shelf Water on the
western Ross Sea continental shelf flows into the cavity along the sea floor and is transformed into Ice Shelf
Water upon contact with the ice shelf base. Ice Shelf Water flows out of the cavity mainly around 180°, but
also further east and on the western side of McMurdo Sound, as observed. Active ventilation of the region
near the ice shelf front is forced by seasonal variations in the density structure of the water column to the
north, driving rapid melting. Circulation in the more isolated interior is weaker, leading to melting at deeper
ice and refreezing beneath shallower ice. Net melting over the whole ice shelf base is lower than other
estimates, but is likely to increase as additional forcings are added to the model.
A model for the spreading and sinking of the Deep Ice Shelf Water
in the Ross Sea
Authors: RUBINO ANGELO , BUDILLON GIORGIO , PIERINI STEFANO , SPEZIE GIANCARLO
Published: March 2003

Spreading and sinking of the Deep Ice Shelf Water (DISW) in the Ross Sea are analysed using
in situ observations and the results of a nonlinear, reduced gravity, layered numerical model, which is able to
simulate the motion of a bottom trapped current over realistic topography. The model is forced by
prescribing thickness and density of the DISW layer at the southern model boundary as well as ambient
density stratification above the DISW layer. This density structure is imposed using hydrographic data
acquired by the Italian PNRA-CLIMA project. In the model water of the quiescent ambient ocean is allowed
to entrain in the active deep layer due to a simple entrainment parameterization. The importance of forcing
the model with a realistic ambient density is demonstrated by carrying out a numerical simulation using an
idealized ambient density. In a more realistic simulation the path and the density structure of the DISW vein
flowing over the Challenger Basin are obtained and are found to be in good agreement with data. It is found
that entrainment, which is particularly active in regions of strong topographic variation, significantly
influences the pattern followed by the DISW layer. The evolution of the DISW layer beyond the continental
shelf, i.e., in a region where the paucity of experimental data does not allow for a detailed description of the
deep ocean dynamics, is also investigated.
Tides of the Ross Sea and Ross Ice Shelf cavity
Authors: PADMAN LAURENCE , EROFEEVA SVETLANA , JOUGHIN IAN
Published: March 2003

Two new ocean tide models for the Ross Sea including the ocean cavity under the Ross Ice Shelf,
are described. The optimum model for predicting ice shelf surface height variability is based on assimilation
of gravimetry-derived tidal constituents from the Ross Ice Shelf. Synthetic aperture radar interferograms
provide an independent test of model performance. The standard deviation of tide height variability is largest
under the eastern ice shelf along the Shirase and Siple Coasts, where it can exceed 0.8 m. The maximum
peak-to-peak tidal range in this region is ∼3 m. The best predictor for ocean tidal currents north of the ice
front is a dynamics-based model that solves the depth-integrated shallow water equations with a linear
representation of benthic friction rather than the more usual quadratic form. Tidal currents over the open
Ross Sea are dominated by diurnal, topographically trapped vorticity waves. The strongest modelled
currents exceed 1 m s−1 at spring tide in a narrow band along the upper continental slope in the north-western
Ross Sea. Typical tidal currents in the central continental shelf area of the Ross Sea are 10–20 cm s−1. Under
the ice shelf the typical currents are ∼5 cm s−1.
M2 tidal dynamics in the Ross Sea
Authors: ROBERTSON ROBIN , BECKMANN AIKE , HELLMER HARTMUT
Published: March 2003

In certain regions of the Southern Ocean, tidal energy is believed to foster the mixing of different
water masses, which eventually contribute to the formation of deep and bottom waters. The Ross Sea is one
of the major ventilation sites of the global ocean abyss and a region of sparse tidal observations. We
investigated M2 tidal dynamics in the Ross Sea using a three-dimensional sigma coordinate model, the
Regional Ocean Model System (ROMS). Realistic topography and hydrography from existing observational
data were used with a single tidal constituent, the semi-diurnal M2. The model fields faithfully reproduced
the major features of the tidal circulation and had reasonable agreement with ten existing tidal elevation
observations and forty-two existing tidal current measurements. The differences were attributed primarily to
topographic errors. Internal tides were generated at the continental shelf/slope break and other areas of steep
topography. Strong vertical shears in the horizontal velocities occurred under and at the edges of the Ross Ice
Shelf and along the continental shelf/slope break. Estimates of lead formation based on divergence of
baroclinic velocities were significantly higher than those based on barotrophic velocities, reaching over 10%
at the continental shelf/slope break.
Estimating the thickness of ridged sea ice from ship observations
in the Ross Sea
Authors: TIN TINA , JEFFRIES MARTIN O. , LENSU MIKKO , TUHKURI JUKKA
Published: March 2003

Ship-based observations of sea ice thickness using the Antarctic Sea Ice Processes and Climate
(ASPeCt) protocol provide information on ice thickness distribution at relatively low cost. This protocol
uses a simple formula to calculate the mass of ice in ridges based on surface observations. We present two
new formulae and compare these with results from the “Original” formula using data obtained in the Ross
Sea in autumn and winter. The new “r-star” formula uses a more realistic ratio of sail and keel areas to
transform dimensions of sails to estimates of mean keel areas. As a result, estimates of “equivalent
thickness” (i.e. mean thickness of ice in ridged areas) increased by over 200%. The new “Probability”
formula goes one step further, by incorporating the probability that a sail is associated with a keel
underwater, and the probability that keels may be found under level surfaces. This resulted in estimates of
equivalent thickness comparable with the Original formula. Estimates of equivalent thickness at one or two
degree latitude resolution are sufficiently accurate for validating sea ice models. Although ridges are small
features in the Ross Sea, we have shown that they constitute a significant fraction of the total ice mass.