251 research outputs found
The Mangrove ecosystem of Deep Bay and the Mai Po marshes, Hong Kong : proceedings of the International Workshop on the Mangrove Ecosystem of Deep Bay and Mai Po Marshes, Hong Kong, 3-20 September 1993
No full textThis volume comprises original research papers reporting findings collected by participants of the International Workshop on the Mangrove Ecosystem of Deep Bay and the Mai Po Marshes, jointly organized by the University of Hong Kong and World Wide Fund for Nature Hong Kong and held at the Mai Po Marshes in September 1993. The papers cover a wide range of topics relevant to the future conservation and management of the threatened ecosystem, ranging from the flora and fauna of the mangrove forests and inner Deep Bay to pollution levels in the biotapublished_or_final_versionPreface / Shing-yip Lee pviiSect.I Flora and fauna p1Sect.II|tEcology and pollution p135The species composition of penaeid prawns in the north- western waters of Hong Kong / S.F. Leung p3Composition, structure and distribution of polychaete assemblages in Deep Bay, Hong Kong / Jian-wen Qiu p13Distribution of shrimp and fish associated with the mangrove forest of Mai Po Marshes Nature Reserve, Hong Kong / D.J. Vance p23A survey of mudflat gastropods in Deep Bay, Hong Kong / M.W. Cha p33Composition and zonation of benthic macrofauna in the Mai Po Marshes mangrove forest / C. Anderson S. McChesney p45The brachyuran fauna of the Mai Po Marshes Nature Reserve and Deep Bay, Hong Kong / S.Y. Lee V. Leung p57Structure and composition of the seaward mangrove forest at the Mai Po Marshes Nature Reserve, Hong Kong / Norman C. Duke M. Ajmal Khan p83Mangrove distribution in the gei wais at the Mai Po Marshes Nature Reserve / L. Young p105Distribution of mangrove species in the intertidal zone at the Mai Po Marshes Nature Reserve / L. Young p117Preliminary observations of ants in Hong Kong mangroves / John R. Fellowes p131Time activity budget of Perisesarma bidens and Parasesarma affinis (Brachyura : sesarminae) at the Mai Po Marshes mangrove, Hong Kong / P.W. Kwok p137Metal concentrations in shrimp and mantis shrimps from Deep Bay, Hong Kong and the eastern waters of the Pearl River estuary / Y.B. Ho p153Litter production and return of nutrient elements in Futian mangrove swamp, Shenzhen, China / M.S. Li C.Y. Lan G.Z. Chen S.H. Li Y.S. Wong N.F.Y. Tam X.R. Chen p165Observations on the mangrove community at the Mai Po Marshes, Hong Kong : implications for conservation / K. Kathiresan p17
Fate and effects of macro-and microplastics in coastal wetlands
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The dataset was used to evaluate the stocks, fate, biological and biogeochemical effects of plastics in coastal wetlands with plastics abundance dataThe data were used for analyses in the following paper: Xiaoguang Ouyang, Carlos M. Duarte,
Siu-Gin Cheung, Nora Fung-Yee Tam, Stefano Cannicci,
Cecilia Martin, Hoi Shing Lo, Shing Yip Lee (2022) Fate and effects of
macro-and microplastics in coastal wetland. Environmental Science &
Technology. doi:
10.1021/acs.est.1c06732.
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Structure and composition of the seaward mangrove forest at the Mai Po Marshes Nature Reserve, Hong Kong
No full textThe seaward mangrove fringe at Mai Po Marshes Nature Reserve, Hong Kong, has extended seaward by 7.6 m.yr-1 and possibly increased in relative ground elevation by 1.1 cm.yr-1 since 1949. It is apparently subject to constant deposition of terrestrial sediments. As a result, the area of mangrove forest has trebled since the construction of the Gei Wai ponds and bunds over 50 years ago. Since then, the mangrove fringe has undergone considerable changes in species composition. It apparently began as a forest dominated by Kandelia candel with an undercanopy of Acanthus ilicifolius and Aegiceras corniculatum. Immediately following bund construction, however, newer seaward forests were dominated by Avicennia marina var. marina until around 1969. After this, Kandelia forests again colonized the seaward margin until the present day, producing a curious bimodal distribution of Kandelia. It is proposed that the herbivore which defoliates Avicennia each year has possibly done so for about 20 or 30 years and now retards recruitment success of that species, allowing Kandelia now to dominate the lower intertidal zone
Prioritising mangrove ecosystem services results in spatially variable management priorities
No full textIncorporating the values of the services that ecosystems provide into decision making is becoming increasingly common in nature conservation and resource management policies, both locally and globally. Yet with limited funds for conservation of threatened species and ecosystems there is a desire to identify priority areas where investment efficiently conserves multiple ecosystem services. We mapped four mangrove ecosystems services (coastal protection, fisheries, biodiversity, and carbon storage) across Fiji. Using a costeffectiveness analysis, we prioritised mangrove areas for each service, where the effectiveness was a function of the benefits provided to the local communities, and the costs were associated with restricting specific uses of mangroves. We demonstrate that, although priority mangrove areas (top 20%) for each service can be managed at relatively low opportunity costs (ranging from 4.5 to 11.3% of overall opportunity costs), prioritising for a single service yields relatively low co-benefits due to limited geographical overlap with priority areas for other services. None-the-less, prioritisation of mangrove areas provides greater overlap of benefits than if sites were selected randomly for most ecosystem services. We discuss deficiencies in the mapping of ecosystems services in data poor regions and how this may impact upon the equity of managing mangroves for particular services across the urbanrural divide in developing countries. Finally we discuss how our maps may aid decisionmakers to direct funding for mangrove management from various sources to localities that best meet funding objectives, as well as how this knowledge can aid in creating a national mangrove zoning scheme
Mangrove Crab Ucides cordatus Removal Does Not Affect Sediment Parameters and Stipule Production in a One Year Experiment in Northern Brazil.
No full textMangrove crabs influence ecosystem processes through bioturbation and/or litter feeding. In Brazilian mangroves, the abundant and commercially important crab Ucides cordatus is the main faunal modifier of microtopography establishing up to 2 m deep burrows. They process more than 70% of the leaf litter and propagule production, thus promoting microbial degradation of detritus and benefiting microbe-feeding fiddler crabs. The accelerated nutrient turn-over and increased sediment oxygenation mediated by U. cordatus may enhance mangrove tree growth. Such positive feed-back loop was tested in North Brazil through a one year crab removal experiment simulating increased harvesting rates in a mature Rhizophora mangle forest. Investigated response parameters were sediment salinity, organic matter content, CO2 efflux rates of the surface sediment, and reduction potential. We also determined stipule fall of the mangrove tree R. mangle as a proxy for tree growth. Three treatments were applied to twelve experimental plots (13 m × 13 m each): crab removal, disturbance control and control. Within one year, the number of U. cordatus burrows inside the four removal plots decreased on average to 52% of the initial number. Despite this distinct reduction in burrow density of this large bioturbator, none of the measured parameters differed between treatments. Instead, most parameters were clearly influenced by seasonal changes in precipitation. Hence, in the studied R. mangle forest, abiotic factors seem to be more important drivers of ecosystem processes than factors mediated by U. cordatus, at least within the studied timespan of one year
Bewegungsmuster und Habitatsnutzung der Kommerziell genutzten Schwimmkrabbe Scylla serrata
No full textMangrove ecosystems are highly productive, providing habitat for a variety of species, of which many are harvested. In times of rapid global change, due to natural as well as anthropogenic drivers, these ecosystems are increasingly placed at risk, and so are the species living within them. The mud crab Scylla serrata (Portunidae) (Forskål, 1775) is a highly valued and exploited species associated with mangrove ecosystems in the Indo-West-Pacific. Its complex life-cycle includes a dispersing larval phase and a benthic phase as juveniles and adults. The planktonic larvae are restricted to oceanic waters, since they are stenohaline and therefore dependent on stable, high salinity conditions in order to survive. Benthic juveniles and adults are physiologically adapted to changing temperatures and varying salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied and these life stages are known to move between various mangrove habitats including intertidal mangrove area flats as well as subtidal channels and flats. Females undertake long distance movements from brackish inshore waters to waters with oceanic conditions for (supposed) spawning. However, little is known about larval stages, and early benthic stages are underrepresented in the literature. The aim of this thesis is to provide deeper insights into movement patterns and habitat use at these particular life stages and to understand how these characteristics might be affected by environmental factors, such as seascape and rainfall
Value of Small Seagrass Patches as Tidal Flow-Refuges
No full textOne central challenge in the study of seagrass meadows is explaining the abundance and diversity of nekton associated with these productive habitats. While many models have been proposed to explain fish use of seagrass habitats, mainly focusing on their nursery and predator-avoidance values based on the complex habitat structure, most empirical studies were conducted on relatively large patches using catch data collected from invasive capture methods. Seagrass meadows on peri-urban coasts, however, continually being threatened and fragmented, while invasive surveying techniques could bias fish abundance data. This thesis aims to determine if small remnant Zostera capricorni patches in a peri-urban estuary provide small mobile fish with a flow-refuge within a strong tidal flow environment, using non-invasive video surveying techniques to monitor fish abundance and behaviour.
The hydrodynamic characteristics of three small patches of Z. capricorni were measured using in situ deployment of Acoustic Doppler Current Profilers (ADCP) at the front and rear of the patches during tidal current flow between 20 and 30 cm/s. Seagrass canopies of densities and morphologies covered by these patches significantly baffled the free-stream flow (X), creating a near-zero, turbulent free, within-canopy hydraulic environment 0.25m from the canopy’s leading edge. Flows were deflected over the canopy surface causing the leaves to bend, compressing the canopy and thereby reducing the vertical flux under high flows. While lower flows were still significantly reduced, a small vertical flux occurred, with large turbulent eddies generating from the canopy friction. The hydraulic environment behind the patch was significantly different to that at the patch’s front – characterised by near zero flows and turbulent fluctuations (at 0m), and flow velocities increasing with downstream distance. This effect was noticeable due to the velocity above the canopy being significantly reduced from flows above the canopy (fast). This difference diminished with downstream distance, gradually resembling the front profile. The rear environment close to the patch edge matched those of other flow-refuges.Thesis (Masters)Master of Philosophy (MPhil)Griffith School of EnvironmentScience, Environment, Engineering and TechnologyFull Tex
Spontaneous Oscillations of Cerebral Blood Flow Velocity in the Middle Cerebral Arteries of Normal Subjects and Schizophrenic Patients
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The role of biogenic structures for greenhouse gas balance in vegetated intertidal wetlands
No full textThis chapter elucidates in detail the current knowledge on the role of biogenic structures for greenhouse gas biogeochemistry and dynamics in vegetated intertidal wetlands, i.e., mangrove forests and saltmarshes. The major types of biogenic structures formed by wetland plants and animals are portrayed and related to relevant biogeochemical processes affecting greenhouse gases. Subsequently, the impact of biogenic structures for greenhouse gas exchange is demonstrated by assessing and compiling the current knowledge on net primary production, carbon sequestration, and greenhouse gas emissions in mangrove forests and Spartina marshes. The data compilation clearly emphasizes the important role of biogenic structures (i.e., plant roots and infaunal burrows/tubes) for carbon cycling and greenhouse gas dynamics of intertidal wetlands. Emission of the greenhouse gases CO2, CH4, and N2O in mangrove forests with biogenic structures is increased 4.8, 29.9, and 3.8 times, respectively, compared with mangrove sediments devoid of these structures. Due to lack of reliable data on the role of burrow structures on greenhouse gas emission in Spartina marshes, only the impact of vegetation is available resulting in an increase of 2.7, 3.3, and 9.1 times, respectively. The strong enhancement of greenhouse gas emissions via biogenic structures largely counteracts the otherwise efficient capacity of carbon sequestration by these vegetated wetlands, leading to climate neutrality when embracing the global warming potential of the involved gases. This finding is surprising and contradicts previous estimates that indicated a distinct climate mitigation potential of mangrove and saltmarsh ecosystems.This chapter elucidates in detail the current knowledge on the role of biogenic structures for greenhouse gas biogeochemistry and dynamics in vegetated intertidal wetlands, i.e., mangrove forests and saltmarshes. The major types of biogenic structures formed by wetland plants and animals are portrayed and related to relevant biogeochemical processes affecting greenhouse gases. Subsequently, the impact of biogenic structures for greenhouse gas exchange is demonstrated by assessing and compiling the current knowledge on net primary production, carbon sequestration, and greenhouse gas emissions in mangrove forests and Spartina marshes. The data compilation clearly emphasizes the important role of biogenic structures (i.e., plant roots and infaunal burrows/tubes) for carbon cycling and greenhouse gas dynamics of intertidal wetlands. Emission of the greenhouse gases CO2, CH4, and N2O in mangrove forests with biogenic structures is increased 4.8, 29.9, and 3.8 times, respectively, compared with mangrove sediments devoid of these structures. Due to lack of reliable data on the role of burrow structures on greenhouse gas emission in Spartina marshes, only the impact of vegetation is available resulting in an increase of 2.7, 3.3, and 9.1 times, respectively. The strong enhancement of greenhouse gas emissions via biogenic structures largely counteracts the otherwise efficient capacity of carbon sequestration by these vegetated wetlands, leading to climate neutrality when embracing the global warming potential of the involved gases. This finding is surprising and contradicts previous estimates that indicated a distinct climate mitigation potential of mangrove and saltmarsh ecosystems
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