Subtropical coral-reef associated sedimentary facies characterized by molluscs (Northern Bay of Safaga, Red Sea, Egypt)

Summary The shallow marine subtropical Northern Bay of Safaga is composed of a complex pattern of sedimentary facies that are generally rich in molluscs. Thirteen divertaken bulk-samples from various sites (reef slopes, sand between coral patches, muddy sand, mud, sandy seagrass, muddy seagrass, mangrove channel) at water depths ranging from shallow subtidal to 40m were investigated with regard to their mollusc fauna >1mm, which was separated into fragments and whole individuals. Fragments make up more than 88% of the total mollusc remains of the samples, and their proportions correspond to characteristics of the sedimentary facies. The whole individuals were differentiated into 622 taxa. The most common taxon,Rissoina cerithiiformis, represented more than 5% of the total mollusc content in the samples. The main part of the fauna consists of micromolluscs, including both small adults and juveniles. Based on the results of cluster-, correspondence-, and factor analyses the fauna was grouped into several associations, each characterizing a sedimentary facies: (1) “Rhinoclavis sordidula—Corbula erythraeensis-Pseudominolia nedyma association” characterizes mud. (2) “Microcirce sp.—Leptomyaria sp. association” characterizes muddy sand. (3)”Smaragdia spp.-Perrinia stellata—Anachis exilis—assemblage” characterizes sandy seagrass. (4) “Crenella striatissima—Rastafaria calypso—Cardiates-assemblage” characterizes muddy seagrass. (5) “Glycymeris spp.-Parvicardium sueziensis-Diala spp.-assemblage” characterizes sand between coral patches. (6) “Rissoina spp.-Triphoridae —Ostreoidea-assemblage” characterizes reef slopes. (7) “Potamides conicus—Siphonaria sp. 2—assemblage” characterizes the mangrove. The seagrass fauna is related to those of sand between coral patches and reef slopes with respect to gastropod assemblages, numbers of taxa and diversity indices, and to the muddy sand fauna on the basis of bivalve assemblages and feeding strategies of bivalves. The mangrove assemblage is related to those of sand between coral patches and the reef slope with respect to taxonomic composition and feeding strategies of bivalves, but has a strong relationship to those of the fine-grained sediments when considering diversity indices. Reef slope assemblages are closely related to that of sand between coral patches in all respects, except life habits of bivalves, which distincly separates the reef slope facies from all others.     

Sedimentation on three caribbean atolls: Glovers reef,lighthouse reef and turneffe Islands,belize

Summary The chief mode of carbonate sedimentation on the Belizean atolls Glovers Reef, Lighthouse Reef and Turneffe Islands is the accumulation of organically-derived particles. Variations in the distribution of the composition and grain-sizes of surface sediments, collected along transects across the atolls, are environmentally controlled. Two major sediment types may be distinguished. (1) Reef and fore reef sediments are dominated by fragments of coral, coralline algae andHalimeda. Mean grain-sizes range from 1–2 mm. (2) Back reef sediments contain more mollusk fragments, more fine-grained sediment (<125 μm) and appear to have fewerHalimeda fragments. In addition, sediments from inner platforms and shallow lagoonal parts of Glovers and Lighthouse Reefs comprise non-skeletal grains, namely fecal pellets. Sediments from lagoonal patch reefs may contain up to 20% coral fragments. Mean grain-sizes range from 0.1–1 mm and are finest on the inner platform and lagoon floor of the back reef environment. Within the reef and fore reef environments, it is not possible to distinguish sub-environments on the basis of textural and compositional differences of the sediments. Sediments from patch reefs contrast with those from back reef lagoons and inner platforms and are similar in terms of grain-sizes and compositions to reef and fore reef surface sediments. Non-skeletal grains forming in shallow parts of the back reef in Glovers and Lighthouse Reefs are interpreted to be indurated by interstitial precipitation of calcium carbonate from warm, supersaturated water flushing the sediment. The lack of hardened non-skeletal particles in the back reef sediments of Turneffe Islands is most probably due to the abundance of muddy, organic-rich sediment in the well-protected lagoon. Fine sediment is less permeable and organic films prevent cement overgrowth on particles.     

The functional role of burrowing bivalves in freshwater ecosystems

1. Freshwater systems are losing biodiversity at a rapid rate, yet we know little about the functional role of most of this biodiversity. The ecosystem roles of freshwater burrowing bivalves have been particularly understudied. Here we summarize what is known about the functional role of burrowing bivalves in the orders Unionoida and Veneroida in lakes and streams globally. 2. Bivalves filter phytoplankton, bacteria and particulate organic matter from the water column. Corbicula and sphaeriids also remove organic matter from the sediment by deposit feeding, as may some unionids. Filtration rate varies with bivalve species and size, temperature, particle size and concentration, and flow regime. 3. Bivalves affect nutrient dynamics in freshwater systems, through excretion as well as biodeposition of faeces and pseudofaeces. Excretion rates are both size and species dependent, are influenced by reproductive stage, and vary greatly with temperature and food availability. 4. Bioturbation of sediments through bivalve movements increases sediment water and oxygen content and releases nutrients from the sediment to the water column. The physical presence of bivalve shells creates habitat for epiphytic and epizoic organisms, and stabilizes sediment and provides refugia for benthic fauna. Biodeposition of faeces and pseudofaeces can alter the composition of benthic communities. 5. There is conflicting evidence concerning the role of resource limitation in structuring bivalve communities. Control by bivalves of primary production is most likely when their biomass is large relative to the water volume and where hydrologic residence time is long. Future studies should consider exactly what bivalves feed upon, whether feeding varies seasonally and with habitat, and whether significant overlap in diet occurs. In particular, we need a clearer picture of the importance of suspension versus deposit feeding and the potential advantages and tradeoffs between these two feeding modes. 6. In North America, native burrowing bivalves (Unionidae) are declining at a catastrophic rate. This significant loss of benthic biomass, coupled with the invasion of an exotic burrowing bivalve (Corbicula), may result in large alterations of ecosystem processes and functions.     

The growth and life span of bivalve mollusks at the northeastern coast of Sakhalin Island

Numerous shells of bivalves, which study attributed to 37 species, were collected from samples of ground taken with a Van Veen dredge sampler at the northeast coast of Sakhalin Island at depths of about 10–60 m in June–October 2003–2009. Tellina lutea, Mactromeris polynyma, Serripes groenlandicus, Macoma spp., Liocyma fluctuosum, and Siliqua alta occurred most often in the samples. The assessment of growth in 18 bivalve species revealed common patterns of age variations that were irrespective of their way of life, maximum body size, and maximum age. The greatest annual increment in shell length was observed in the first 4 years of life, and the asymptotic size of the mollusks was reached with a 10-fold decrease in the annual growth rate. The life span of the mollusks varied from 2 up to 41 years and sometimes significantly differed from that of the studied species in other areas of their range, clearly displaying the ecological conditionality of this parameter. Species with maximum ages of less than 10 years were the most numerous in the bivalve community of the region. The results of the research are discussed in relation to the nature of the environment at the northeast coast of Sakhalin Island.     

Comparative taphonomy of three bivalve species from a mass shell accumulation in the intertidal regime of North Sea tidal flats

This study comprises a comparative taphonomic analysis of three endobenthic bivalves (Mya arenaria, Cerastoderma edule, and Macoma balthica) derived from a mass accumulation of mainly vertically packed shells from the “Wurster Watt” in Lower Saxony’s Wadden Sea, German Bight. Bulk samples from two transects were analyzed with respect to taxonomic composition, left/right valve presence, counts and weight percentages of taxa, and size-frequency distributions. Taphonomic features including abrasion, fragmentation, encrustation and bioerosion were subjected to a semi-quantitative analysis. Taphonomic results show significant differences with respect to bivalve taxa as well as between transects. Mya arenaria, a large endobenthic bivalve, shows the greatest amount of fragmentation and is often encrusted by balanids and bryozoans. The smaller and more robust Cerastoderma edule has the greatest values for bioerosion especially by the polychaete Polydora ciliata. Macoma balthica, which has the thinnest valves, shows the highest values for abrasion, but low values for the rest of the measured taphonomic features. Taphonomic differences between the taxa, samples and transects are related to (1) the origin of the bivalves (from living populations or exposed colonization horizons), (2) the different size and morphology of the valves (themselves related to mode of life), (3) the taphonomic trajectories of the different bivalves, as well as (4) the varying depositional environment of the two transects.     

Taphonomy of Eemian marine molluscs and acorn barnacles from eastern Arkhangelsk region, northern Russia

Marine Eemian deposits along the Pyoza river and its tributary Varchuska, Arkhangelsk region, constitute successions of muddy and sandy facies with rich macrobenthic fauna dominated by bivalves and barnacles. Taphonomic features formed by abrasion, disarticulation, dissolution, fragmentation, bioerosion and encrustation define taphofacies for a palaeoenvironmental model. Five bivalve taphofacies and three barnacle taphofacies could be distinguished. Both bivalves and barnacles are poorly preserved in foreshore/shoreface environments, as the shells were subjected to extensive transportation by currents. The shells were best preserved in offshore environments, where rapid episodic sedimentation enabled within-habitat preservation, in some cases even preservation in life position. Barnacles are absent from the most clay-rich offshore deposits, probably because of clogging of filters by turbidity and lack of suitable substrate. Such dissimilarities suggest that the number and distribution of taphofacies may depend on which fossil groups are used. Interspecific variability may exist within the individual taphofacies. The barnacles, for example, tend to be better preserved than the mussel Mytilus edulis, although both are fixosessile suspension feeders. This indicates that not only life habits but also intrinsic shell properties influence preservation. Thus, taphofacies analyses should combine data on taphonomic features, specific life habit and shell properties to determine overall preservation patterns. In that way, taphofacies analyses may form a powerful tool for palaeoenvironmental analyses of marine deposits.     

Structural features and taphonomic pathways of a high-biomass epifauna in the northern Gulf of Trieste, Adriatic Sea

Benthic ecologists and palaeoecologists usually associate soft bottoms with infaunal species. On the sublittoral muddy soft bottoms in the inner Gulf of Trieste, however, a complex epifauna is developed, whose biomass, structural features and taphonomy is investigated here. The total biomass amounted to an average of 556 g wet weight/m² and is strongly dominated by suspension feeders, followed by predators and deposit feeders. The biomass can be divided into two major groups: biomass on benthic islands (isolated and small-sized rockgrounds and shellgrounds which are embedded in or lie on the sediment) and sediment dwellers. The former category includes so-called multi-species clumps, which make up 92.5% of the total biomass. The latter category encompasses organisms that inhabit the sediment surface itself. The epigrowth on benthic islands makes up 84.6% of total epifaunal biomass and is exclusively represented by suspension feeders. Serpulids are strongly dominant, followed by ascidians, sponges, anemones and bivalves. The vagile organisms associated with multi-species clumps represent 7.9% of the total epifauna and are also mostly suspension feeders. The echino-derms Ophiothrix quinquetnaculata and Cucumaria planci are the two dominant forms, followed by crustaceans and echinoids. Soft-bottom dwellers represent only 7.5% of total epifaunal biomass and consist mainly of deposit feeders and predators. Three different post-mortem pathways can be recognized for the studied epifauna. Taphonomic loss due to selective preservation is the most important taphonomic process shaping the death assemblage and affects especially the soft-bodied epigrowth on benthic islands. Mineralized epigrowth and shelled soft-bottom dwellers are the main source of benthic islands. Vagile faunas on such islands, in contrast, are strongly affected by disarticulation / fragmentation and their body parts contribute considerably to the sediment composition. The death assemblage does not reflect the trend of low biomass near the shallow stations off the mouth of the Isonzo River and higher biomass at most stations positioned further away from the river and in deeper water (> 10 m), but acccurately reflects the borders of the epifauna, which coincide with the sedimentary facies and the preponderance of the suspension-feeding life habit.     

Composition, abundance and stratification of soft-bottom macrobenthos from selected areas of the Ross Sea shelf (Antarctica)

Composition, abundance and stratification of soft-bottom macrobenthos were studied at three selected sites on the Ross Sea shelf (Antarctica) with different geomorphology and sedimentation regimes. Sites A (southwest Ross Sea, 810 m depth) and B (Joides basin, 580 m depth) were characterized by biogenic mud and clay sediments, whereas site C (Mawson bank, 450 m depth) featured sandy sediments mixed with a conspicuous biogenic component characterized by shells and tests of calcareous invertebrates (mainly barnacles of the genus Bathylasma). The macrofauna of sites A and B was mainly composed of infaunal polychaetes and bivalves. The assemblages comprised both surface and sub-surface deposit feeders, including some conveyor-belt polychaetes (Maldanidae and Capitellidae) that are responsible for high sediment mixing and bioturbation. The macrobenthos of site C was dominated by crustaceans, polychaetes and echinoderms (ophiuroids), and mainly by filter feeders and epifaunal or interstitial forms. Abundances were higher (up to 1040 ind. m⁻²) at site B than at sites A and C (430 and 516 ind. m⁻², respectively). At sites A and B the benthos was mainly concentrated in the upper 5 cm of the sediment, and abundances declined sharply in the deeper sediment layers. These results indicate a high degree of consistency between sediment features and benthic community structure, which are both strongly related to local hydrography and bottom dynamics. Sites A and B represent areas where the organic input to the seafloor by vertical sedimentation from the upper water column is high. Site C, however, is characterized by high sediment instability and food particles advecting mainly horizontally. The community is more physically controlled by unpredictable, and probably frequent, disturbance events (e.g., bottom turbid currents, sediment reworking and displacement). Individuals were relatively small, indicating that probably they are not able to grow up to the adult size and reproduce. The community may be represented by “pseudopopulations” depending on the settlement of larvae invading from neighbouring areas. Accepted: 23 October 1998     

Environmental history and physiological state influence feeding responses of Atrina zelandica to suspended sediment concentrations

Epifaunal suspension-feeding bivalves can play important roles in marine ecosystems affecting macrobenthic communities, benthic boundary layers and benthic-pelagic coupling, not just by their presence but also by any changes in feeding behaviour. While seston quality and quantity have consistently been found to be important influences on the feeding rates of suspension-feeding bivalves, factors stressing individuals are also likely to be important, as they may affect energy-dependent thresholds of response. We postulated that (1) history of seston quantity would affect how suspension feeders deal with increases in total suspended particulates, and (2) high-seston concentrations would affect feeding rates more in individuals whose energy reserves were low after spawning. Three sites were selected for short-term (1 day) feeding experiments on the pinnid bivalve, Atrina zelandica. At one site, the experiment was run pre-and postspawning. Atrina exhibited high rejection of filtered particles (mostly 75% to 100%) and high organic absorption efficiencies (0.9-1) at all seston levels. Strong differences in the response of feeding behaviour to increased seston concentrations were observed between A. zelandica from the different sites, with lesser differences observed between times. The site-specific feeding responses to seston concentrations observed are likely to affect our ability to model responses of A. zelandica to sediment loading and to influence the importance of A. zelandica to benthic-pelagic coupling.     

Opisoma excavatum Boehm,a Lower Jurassic photosymbiotic alatoform‐chambered bivalve

Alatoform bivalves are a polyphyletic group characterized by antero‐posteriorly compressed shells and a ventro‐lateral wing originating from a tight fold of the shell wall. This bizarre shell morphology is interpreted as an adaptation for algal photosymbiosis in heliophilous bivalves. The group contains the living heart cockle Corculum together with four extinct genera ranging in age from the Permian to the Jurassic. The Jurassic alatoform bivalve is Opisoma, which has an aragonitic shell that is divided into two regions, both with different functions: one for stabilization, the other for hosting symbionts. The dorsal part of the shell is massive and played the stabilization role. The ventral part has a very thin and fragile shell that permitted the transmission of light into the internal tissues harbouring photosymbionts. The morphology of this delicate ventral part has thus far remained obscure, due to lack of preservation. Accumulations of Opisoma excavatum Boehm with exquisitely preserved shells containing the fragile winged ventral parts are common within the Pliensbachian shallow‐water, lagoonal carbonate succession of the Rotzo Formation of northern Italy. The wings have internal curved chambers limited by septa parallel to the wing edge. The shell of the ventral part consists of irregular fibrous prismatic and homogeneous structures which progressively infill the chambers. As the chambered wings are analogous structures among alatoform bivalves, they are no longer considered a taxonomic character. According to the observed shell orientation in the field and the consequent organization of the soft parts, Opisoma had an opisthogyrate shell.     

Depth-related changes to density,diversity and structure of benthic megafaunal assemblages in the Fimbul ice shelf region,Weddell Sea,Antarctica

The depth-related patterns in the benthic megafauna of the NE Weddell Sea shelf at the edge of the Fimbul Ice Shelf were investigated at seven sites using towed camera platform photographs. Megafaunal density decreased with depth from 77,939 ha⁻¹ at 245 m to 8,895 ha⁻¹ at 510 m. While diversity was variable, with H′ ranging between 1.34 and 2.28, there were no depth related patterns. Multivariate analyses revealed two distinct assemblages; a shallow assemblage with dense patches of suspension feeders in undisturbed areas and a deep assemblage where these were not present. Disturbance from icebergs explained many observed patterns in faunal distribution. In shallow waters probable effects of disturbance were observed as changes in successional stages; in deeper waters changes in habitat as a result of past disturbance explained faunal distributions. In deeper areas ice ploughing created a mosaic landscape of fine and coarse sediments. Total megafaunal density was highest in areas of coarse sediment (up to 2.9 higher than in finer sediment areas) but diversity was highest in intermediate areas (H′ = 2.35).     

A preliminary survey of the relative abundance of fecal coliform bacteria in water and sediment and in the fresh water bivalve,Lamellidens marginalis,of the Buriganga river,Bangladesh

Studies on the concentration of fecal coliforms in freshwater bivalves were carried out using a spread plate method and membrane fecal coliform medium. Water, sediment, and bivalves collected from the Buriganga River at Dhaka, Bangladesh, were examined. As demonstrated in many previous studies, fecal coliform counts were consistently higher for the bivalve tissue than those for water and sediment samples; in the bivalveLamellidens marginalis, they were 10.0- to 87.0-fold higher than those in water, and 2.0- to 11.0-fold higher than those in sediment.     

Use of Bivalve Metrics to Quantify Influences of Coal-related Activities in the Clinch River Watershed, Virginia

Previously, we reported that survivorship and growth of field-caged Asian clams (Corbicula fluminea [Müller]) were significantly reduced downstream of the wastewater effluent discharge of the Clinch River Plant (CRP), a coal-fired electric power-generating facility in Russell County, VA (USA). These findings warranted the present study, which investigated whether reduced survivorship and growth of transplanted C. fluminea were predictive of adverse effects on resident bivalves – most notably the Clinch River’s (CR’s) federally protected freshwater mussel fauna (Unionoidea). Thus, surveys of unionoid assemblages and C. fluminea population densities and age distributions were conducted to assess ecotoxicological effects on bivalve assemblages naturally occurring in the CR. Results of these surveys suggested that field bioassays with transplanted C. fluminea were predictive of in-stream C. fluminea densities and the presence/absence of indigenous unionoid assemblages. Relative to C. fluminea, additional field bioassays with a juvenile unionoid species (Villosa iris) native to the CR were less predictive of adverse effects on resident bivalves. Concurrence of transplant studies and in-stream surveys was evident at most study sites, particularly within 0.6 km downstream of the CRP effluent where resident bivalves were virtually non-existent relative to other stream sites having similar habitat conditions. Our findings indicate that in situ field bioassays with transplanted C. fluminea are valuable tools for predicting in stream occurrence and distribution of resident freshwater bivalves, and that field studies integrating multiple bivalve metrics may be useful for prioritizing source-reduction efforts in similar watersheds. Discrepancies observed for transplanted C. fluminea and V. iris have important implications to selection of bivalve species used in field bioassays and warrant further study.     

Taphofacies analysis of recent shelly cheniers (beach ridges), northeastern baja california,Mexico

Summary This report presents the results of taphofacies analyses of shelly cheniers (mollusk-dominated lag-concentrations) from the tidal flats of northeastern Baja California, Mexico. The three generations of moderm (formed during last 70 years), submodem (younger than 1,500 BP), and subfossil (5,000–2,000 BP) cheniers can be distinguished by their position relative to the shoreline, their topography, and the radiocarbon-age of their shells. The generations differ in the duration and complexity of their taphonomic history. Sixty-one samples from nine localities were collected to test the utility of the taphofacies approach for studying chenier-type shell deposits. The three chenier generations, although all dominated by the bivalve molluskMulinia coloradoensis, differ significantly in their taxonomic composition due to taphonomic and/or biologic factors. The taphofacies analysis included 4,334 specimens ofM. coloradoensis described by nine taphonomic variables. Univariate analysis of those variables indicated that the shells that accumulated in the cheniers are little-affected by biological processes (bioerosion, encrustation), and moderately affected by physical processes (fragmetation, cracking, peeling, edge preservation). Only the luster features of shells (external luster, internal luster, and internal features) vary substantially and consistently with chenier age —a result of subaerial weathering. Multivariate taphofacies analysis discriminates the three generations of cheniers even when the poorly preservable luster variables are excluded from the analysis. This suggests that taphofacies discrimination is possible for fossil cheniers. The shells collected from the chenier surface have substantially poorer preservation than shells from the subsurface, indicating that taphonomic degradation in the chenier plain environment is a surface phenomenon. Chenier plain shelly assemblages are taphonomically distinct from assemblages formed in other marine environments: they have a very low frequency of macroscopically recognizable bioerosion and encrustation. The existence of preservable taphonomic differences between the cheniers that differ in their age (i.e., duration of preburial history), suggests that fossil lag concentrations may be useful in detecting incompleteness gradients along stratigraphic boundaries. A ‘taphonomic clock’—a correlation between a ‘time-sincedeath’ and shell preservation—was found only for luster features, taphonomic attributes that are unlikely to be preserved in the fossil record.     

The relationship of bioenergetics and the environment to the field growth of cultured bivalves

The field culture of bivalve molluscs is dependent on the production and supply of phytoplankton and other food sources, its consumption by these suspension feeders, and its transformation into bivalve tissue. An understanding of the processes by which food is captured and utilized is fundamental to prediction of bivalve growth and management of shellfish aquaculture. The following perspective considers the role of food quality and quantity in the ingestion and absorption of food particles, as well as the influence of temperature, water circulation and other environmental variables on bivalve energy budgets and growth rate. A particular focus is the role of simulation modelling in quantifying the influence of these variables on scope for growth. Seston depletion is a major influence on cultured animals such that bivalves are limited by both food quality and quantity. Seston depletion can be managed by taking advantage of particle maxima (e.g. resuspension), matching culture species to turbidity gradients, and arranging hanging culture to take advantage of seston renewal in oblique flow. Food limitation interacts with temperature in cold temperate areas where high primary production occurs at low temperatures. Model simulations of mussel growth demonstrate the importance of temperature acclimation of filtration and its relationship to the timing and magnitude of the spring bloom. In addition to the energetics of individual animals, energy flow through culture ecosystems is considered in terms of bivalve processing of organic matter and competition with Zooplankton and fish. Because bioenergetics is at the root of all of these issues, simulation modelling of scope for growth and related components of the ecosystem is a vital tool in prediction and management of commercial bivalve aquaculture.     

Spatially Extended Habitat Modification by Intertidal Reef-Building Bivalves has Implications for Consumer-Resource Interactions

Ecosystem engineers can strongly modify habitat structure and resource availability across space. In theory, this should alter the spatial distributions of trophically interacting species. In this article, we empirically investigated the importance of spatially extended habitat modification by reef-building bivalves in explaining the distribution of four avian predators and their benthic prey in the Wadden Sea—one of the world’s largest intertidal soft-sediment ecosystems. We applied Structural Equation Modeling to identify important direct and indirect interactions between the different components of the system. We found strong spatial gradients in sediment properties into the surrounding area of mixed blue mussel (Mytilus edulis) and Pacific oyster (Crassostrea gigas) reefs, indicating large-scale (100s of m) engineering effects. The benthic community was significantly affected by these gradients, with the abundance of several important invertebrate prey species increasing with sediment organic matter and decreasing with distance to the reefs. Distance from the reef, sediment properties, and benthic food abundance simultaneously explained significant parts of the distribution of oystercatchers (Haematopus ostralegus), Eurasian curlews (Numenius arquata), and bar-tailed godwits (Limosa lapponica). The distribution of black-headed gulls (Chroicocephalus ridibundus)—a versatile species with many diet options—appeared unaffected by the reefs. These results suggest that intertidal reef builders can affect consumer-resource dynamics far beyond their own boundaries, emphasizing their importance in intertidal soft-bottom ecosystems like the Wadden Sea.     

Simulating harvesting scenarios towards the sustainable use of mangrove forest plantations

Mangrove forests appear among the most productive ecosystems on earth and provide important goods and services to tropical coastal populations. Thirty-five percent of mangrove forest areas have been lost worldwide in the last two decades. Management measures could be an option to combine human use and conservation of mangroves. These measures can be improved if their impacts are assessed before they are performed. By doing so, the best management option out of a set of all potential options can be selected in advance. The mangrove model—KiWi—has been proven to be suitable for analyzing mangrove forest dynamics in the neotropics. Here, the model was applied to mangrove management scenarios. For this, the model was parameterized to Rhizophora apiculata, one of the most common mangrove species planted in Asia for timber production. It is thus the first simulation model describing Asian mangrove plantations. The recently developed Pattern Oriented Modelling approach was used to find those parameters fitting best density patterns and dbh (diameter at breast height) size classes reported in literature. The results demonstrated that the KiWi model was able to: (1) reproduce the growth patterns of a mono-specific plantation of R. apiculata in terms of forest density and size class distribution and (2) can provide criteria for the selection of a thinning strategy within a harvesting cycle.     

Restoration of mangrove plantations and colonisation by native species in Leizhou bay,South China

To examine the natural colonisation of native mangrove species into remediated exotic mangrove stands in Leizhou Bay, South China, we compared soil physical–chemical properties, community structure and recruitments of barren mangrove areas, native mangrove species plantations, and exotic mangrove species—Sonneratia apetala Buch.Ham—between plantations and natural forest. We found that severely degraded mangrove stands could not regenerate naturally without human intervention due to severely altered local environments, whereas some native species had been recruited into the 4–10 year S. apetala plantations. In the first 10 years, the exotic species S. apetala grew better than native species such as Rhizophora stylosa Griff and Kandelia candel (Linn.) Druce. The mangrove plantation gradually affected soil physical and chemical properties during its recovery. The exotic S. apetala was more competitive than native species and its plantation was able to restore soil organic matter in about 14 years. Thus, S. apetala can be considered as a pioneer species to improve degraded habitats to facilitate recolonisation by native mangrove species. However, removal to control proliferation may be needed at late stages to facilitate growth of native species. To ensure sustainability of mangroves in South China, the existing mangrove wetlands must be managed as an ecosystem, with long-term scientific monitoring program in place.     

Macrofouling of the Scallop Mizuhopecten yessoensisin the Polluted Area of Amursky Bay, Sea of Japan

The fouling structure of the Japanese scallop was studied in Amursky Bay near Vladivostok. Fifty-six species of hydrobionts were identified. Barnacles prevailed in biomass and population density, and algae dominated in the number of species. The change in the dominant barnacle species observed in the fouling was caused, apparently, by the reproductive strategy of Hesperibalanus hesperius, which is more labile than that of Balanus rostratus, and by the anthropogenic impact on the ecosystem of the bay. The fouling was marked by bivalve and sea anemone species resistant to silting and pollution. The main groups of epibionts were classified as suspension feeders, and as selective detritophages that are characterized by their type of feeding. The total infestation of shells of the Japanese scallop by boring polychaetes and the depressed condition of most mollusks and algae evidenced the unfavorable ecological situation in the area surveyed.