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Hot stamping operations of a quenchable steel sheet were included in progressive-die plate forging to produce a tailored high strength gear part without additional heat treatments. As process design for the inclusion, the former stages in the progressive-die operations for punching and trimming were cold stamping, and subsequently, resistance heating, blanking, forging and die quenching were performed. The plate was partially resistance-heated with a pair of electrodes to produce a tailored gear part having high strength teeth and a ductile remainder. The tooth portion was uniformly heated around 1050 °C in the transversal current direction, and a gear part having teeth having 520 HV2 in hardness was produced. The quality of the teeth was improved by hot semi-blanking with local compression and cold scrap removing. It is found that the combined process of plate forging and hot stamping is useful to produce ultra-high strength steel parts.

Around intertidal coral reefs, viscous layers, flocs, and bubbles can form on the water surface, and these are collectively referred to as mucus aggregates. To assess effects of substances contained in mucus aggregates on population growth rates of autotrophic and heterotrophic organisms, aqueous materials extracted from mucus aggregates and polysaccharides collected from cultured microalgae were added to rocky intertidal reef sediments in a controlled laboratory experiment. Temporal changes in autofluorescence cell density and nonautoflorescence cell density in reef sediments were examined. Results suggested that microorganism population growth in subtropical rocky intertidal reefs is limited by low concentrations of organic carbon and nutrients in the environment, and that components of mucus aggregates can supplement these materials, leading to increased microbial population growth rates. In particular, aqueous extracts of mucus aggregates contained nutrients that likely promoted growth of autotrophic bacteria, whereas extracellular polymeric substances (EPS) contained polysaccharides that likely promoted growth of heterotrophic bacteria.

We tested the regional-scale latitudinal patterns of occurrence and community structure of rocky tidepool fishes in relation to local environmental factors, particularly substrate characteristics. Data were derived from intensive field observations conducted on 36 shore sites spread across ca. 1,000 km north–south (24°03′N–32°45′N) in the south-western Japan. While numbers of families, genera, species and individuals per unit area decreased with latitude, these were dependent on substrate types: sites with non-limestone rock substrates tended to harbour larger numbers than limestone sites at the same latitude. Relative abundances of two dominant families (Blenniidae and Gobiidae) varied among sites with weak latitudinal gradients. Species-specific trends of latitudinal distribution were observed in most of the common intertidal fishes, with over half of the species demonstrating substrate-dependent variation. Species composition was clearly different between the Kyushu Island and the Ryukyus and also between limestone and non-limestone sites. Thus, our results clearly demonstrated that the regional-scale latitudinal trends of tidepool fish assemblages were partially dependent on local environmental characteristics (substrate types). Consideration was given to the influences of the Kuroshio Current and other factors including species interactions that might have helped modify observed latitudinal patterns.

Some scleractinian coral larvae have an extraordinary capacity to delay metamorphosis, and this is reflected in the large geographic range of many species. Coral eggs typically contain a high proportion of wax esters, which have been hypothesized to provide a source of energy for long-distance dispersal. To better understand the role of lipids in the dispersal of broadcast spawning coral larvae, ontogenetic changes in the lipid and fatty acid composition of Goniastrea retiformis were measured from the eggs until larvae were 30 days old. Egg biomass was 78.8 ± 0.5% lipids, 86.3 ± 0.2% of which were wax esters, 9.3 ± 0.0% polar lipids, 4.1 ± 0.2% sterols, and 0.3 ± 0.1% triacylglycerols. The biomass of wax esters declined significantly through time, while polar lipids, sterols and triacylglycerols remained relatively constant, suggesting that wax esters are the prime source of energy for development. The most prevalent fatty acid in the eggs was palmitic acid, a marker of the dinoflagellate Symbiodinium, highlighting the importance of symbiosis in coral reproductive ecology. The proportion of polyunsaturated fatty acids declined through time, suggesting that they are essential for larval development. Interestingly, triacylglycerols are only abundant in the propagules that contain Symbiodinium, suggesting important differences in the energetic of dispersal among species with vertical and horizontal transmission of symbionts.

Mucus films, flocs or foams consisting of fine sand, algae and detritus frequently occur in the surface waters of rocky intertidal reef flats during incoming tide. These masses are referred to as mucus aggregates. We examined the developmental process of mucus aggregates and their abundance, distribution, migration and trophic composition. The trophic composition of mucus aggregates was then compared to those of sediments to evaluate their potential nutritional value for benthic animals. The organic matter content, chlorophyll a concentration, microalgal density and bacteria-derived fatty acid contents of mucus aggregates were higher than those observed in sediment, suggesting that mucus aggregates contain not only high levels of organic matter but also dense concentrations of microalgae and bacteria; therefore, mucus aggregates may serve as a qualitatively more energetic food source for benthic fauna compared to sediments. Benthic diatoms were the most abundant organisms in mucus aggregates. Large numbers of diatoms were trapped in fine mineral particles and mucilage-like strings, suggesting that a portion of the mucus is secreted by these benthic microalgae. Mucus aggregate accounted for only 0.01–3.9% of the daily feeding requirements of the dominant detritivore, Ophiocoma scolopendrina (Echinodermata: Ophiuroidea) over the entire sampling area. In contrast, for the species population on the back reef, where mucus aggregates ultimately accumulate, mucus aggregates provided from 0.4 to 113.3% of food for this species. These results suggest that mucus aggregate availability varies spatiotemporally and that they do not always provide adequate food sources for O. scolopendrina populations.

Estuaries and their associated rivers are organically rich sites that play an important role in the removal and transformation of organic matter and nutrients derived from terrigenous and anthropogenic sources. This study conducted comprehensive field surveys from March 2010 to January 2011 to study the downstream pattern and distribution of nutrients (NO , NO , NH and PO ) and dissolved organic carbon (DOC) and particulate organic carbon (POC) and nitrogen (PN) in the surface waters of the Manko estuary, a subtropical estuary in Okinawa, Japan. Fatty acid (FA) analysis and POC–C/N ratios were used to further identify variations in the sources of particulate organic matter along the estuary during summer (July) and winter (January). The results suggest that the estuary contains high concentrations of dissolved inorganic (N and P) and organic (DOC) nutrients, which are largely influenced by terrestrial sources from the Kokuba and Noha rivers, and moderate levels of particulate nitrogen and carbon. In gener...

We evaluate the use of the combination approach of fatty acid (FA) profiles and Carbon/Nitrogen ratios to investigate the feeding preference of the sesarmid crab Perisesarma bidens on different diets. The alga Enteromorpha intestinalis, Kandelia obovata leaves and propagules were used in a laboratory feeding assay. Consumption rates of P. bidens were higher in the order of algae= leaves>propagules. C/N ratios indicate that P. bidens significantly assimilates both nitrogen and carbon from algae, nitrogen but not carbon from brown leaves, and only carbon from propagules. A comparison of FAs in tissues and faeces indicated that crabs efficiently assimilate essential FAs (EFAs) from a given diet in the order of algae>leaves>propagules. Results of higher EFA ratios ( 3/ 6) match with that of low C/N ratios indicating that algae had higher nutritional value than leaves and propagules. FA profiles suggested that brown leaf palatability was due to decomposing activity by bacteria and fungi in the leaf tissues. These data suggest that the combination of FA profiles and C/N ratios provides a better understanding of the diet choice by sesarmid crabs.

This study aimed to elucidate Dotilla myctiroides (H. Milne-Edwards) food resources and how the soldier crab influences the organic matter composition on the intertidal flat. A preliminary assessment of D. myctiroides size, sex, and population distribution was conducted to clarify the characteristics of the inhabiting population. Overall, D. myctiroides size and abundance was normal across the tidal flat area. Comparison of different sediment types from the soldier crab habitat (surface sediments, igloos, burrow lining, burrow pellets, feeding pellets, and feces) using the fatty acid (FA) analysis technique revealed D. myctiroides removes organic matter via the significantly lower contributions of polyunsaturated FAs, essential FAs, and dinoflagellates in the feeding pellets. Dotilla myctiroides tissue analysis of the hepatopancreas and hindgut in individuals that had been starved for 24 h confirmed not only the consumption of dinoflagellates, but diatoms and macroalgae as well. In addition, the FA metabolism within the digestive system implied the ability of the soldier crab to synthesize highly unsaturated FAs (HUFAs) such as 20:4n–6, 20:5n–3 and 22:6n–3.

The feeding preference of the sesarmid crabPerisesarma bidenswas investigated when offered different diets:Enteromorpha intestinalis(algae),Kandelia obovataleaves, and propagules. Nutritional value of food, its assimilation, and fates were evaluated using a combination approach of the fatty acids (FAs) and C/N ratios. When offered a mixed diet, male crabs preferred algae than leaves and/or propagules, while a female preference was equally for leaves and algae but less than propagules. The nutritional value of algae was higher as indicated by low C : N ratios and highω3/ω6ratios than leaves and propagules. FAs comparison of tissues and faeces indicated that crabs efficiently assimilate essential fatty acids (EFAs) from a given diet in the order of algae greater than leaves and propagules. Despite of sesarmid crabs being a mangrove leaf-eater,E. intestinaliscan potentially be important source of nitrogen supplement forP. bidensunder mangrove forests.

Changes in the fatty acid composition in the tissues of the bivalve Quidnipagus palatum from the Tomigusuku intertidal flat, Okinawa, Japan, collected in four different seasons (November 2000, the beginning of cold season; January 2001, the cold season; May 2001, the rainy season; and July 2001, the warm season) were examined and compared to the composition of surface sediments and suspended particulate materials. Assessment of fatty acid markers suggested that the food sources of Q. palatum differed between seasons and depended on the sources of organic material present in the sediment and water column. Vascular plants and bacteria were the main dietary components from July to November because of their abundance in the sediment. From November to January, macroalgae and phytoplankton were the major food sources of Q. palatum, corresponding to their predominance in sediments and algal blooms, respectively. During the May rainy season, organic matter in the sediment was dominated by diatoms, whereas the water column contained diatoms and resuspended macroalgal detritus. The transition to the warm season by July significantly increased the contribution of diatoms to the organic matter present in both the sediment and the water column. Consequently, from May to July, diatoms became the main food source for Q. palatum.

The temperature tolerances of embryonic and early larval development stages of Tripneustes gratilla were investigated from 13-34°C under laboratory conditions. Zygotes showed unequal cleavage at 13°C, whereas cleavage did not occurred at 34°C. Hatching was observed between 16–31°C with maximum hatching rates observed at 22–29°C. The lower and higher temperature limits for embryonic development were approximately 22°C and 29°C, respectively. Outside of this temperature range, embryos showed abnormality at different incubation times. Early larvae of this species have the ability to survive the higher temperature limit for short periods of time. Prism and 2 arm pluteus larvae survived at temperatures between 30 and 33°C, whereas 4 arm pluteus larvae survived at temperatures between 30 and 36°C for 2 h. These results suggest that the larval temperature tolerance capability of T. gratilla is stage dependent. These findings are important for understanding the life history strategy of this sea urchin in the shallow open water environment.

On the shallow sandy bottom in the innermost part of the Gulf of Thailand, the regular sea urchin Salmacis sphaeroides feeds on two spatangoid urchins: Brissus latecarinatus, one of the locally dominant infaunal macrobenthic animals, and Lovenia elongata. Aggregations of Salmacis were frequently seen on the soft bottom during a survey of the macrobenthos in the Gulf, and Brissus individuals lacking spines were found beneath the aggregations. Brissus species, which are infaunal, were attacked by Salmacis, although the reason for their presence on top of the sandy bottom remains unknown. Salmacis were seen feeding first on the spines of Brissus, exposing the test. Occasionally, Salmacis carrying empty, broken tests of Brissus were observed, indicating that the Brissus organs were also eaten by Salmacis. The fact that Salmacis ate several kinds of food items such as water hyacinths originated from the nearby river system, sea pens, jellyfish, and other urchins indicates that this species is an omnivore. Cannibalism was also found both in the field and laboratory. The feeding strategy of Salmacis has evolved to incorporate diverse food items, but Brissus is undoubtedly an important food source because of its high abundance.

We observed a severe reduction in salinity around Khang Khao Island at the end of the rainy season in September and October, 1995, caused by the most serious freshwater flooding in Thailand in recent 15 years. During low tide, corals around Khang Khao Island were exposed to 23‰ at three meters depth, and 25‰ at five meters. As a result, Pocillopora damicornis and a few species of Acropora showed colony bleaching or partial or complete colony death in the field. On the other hand, Porites spp., the dominant corals of this area, did not show any conspicuous effects. Porites lutea could survive five days of experimental exposure to 17‰, the critical salinity for other corals. The chlorophyll-a concentration of P. lutea that become partially bleached after seven days exposure to 20‰ was higher than in normal control fragments. These phenomena suggest that P. lutea has a compensation mechanism against salinity reduction. Both field observations and experiments suggest that lowered salinity caused by runoff during the rainy season is an important factor besides turbidity in establishing the characteristics of the coral community structure around Khang Khao Island. A detailed study of the process of coral community formation in this area may contribute to an understanding of not only the negative effects of continental great rivers on the establishment of coral reefs around tropical continental shores but also the influence of the heavy rainfall on a coral community in the coral reef region by the global climate change.

The fatty acid composition of suspended particulate organic matter (POM) and tilapia (Oreochromis mossambicus) and potential sources of organic material in the Manko Estuary, Okinawa Island, Japan, were investigated to elucidate the origin of organic matter in suspended particulate matter and the contribution of these inputs to the diet of tilapia. Fatty acid fingerprints of POM revealed that diatoms, bacteria, and possible material input originating from domestic waste discharges contributed a major proportion of the organic matter pool in the estuary. The diet of tilapia is likely influenced by domestic waste-derived organic matter through a POM link. Because of their highly plastic feeding habits, tilapia may develop a feeding strategy of utilizing the most favorable food resources in the ecosystem. Tilapia likely does not prefer mangrove detritus as a food source as indicated by the absence of even-number long-chain fatty acids (LCFAs) in their tissues. Instead of mangrove detritus, tilapia preferentially utilized more palatable organic food sources in the water column, such as phytoplankton and its detrital matter. In addition to phytoplankton and bacterioplankton, the other dietary sources that contributed a minor fraction were possible green macroalgal materials and zooplankton.

The present study aimed to investigate the spatial structure of fish communities at juvenile and adult stages on coral reefs at Kudaka Island (Ryukyu Archipelago, Japan) and to relate spatial patterns in the structure of the fish communities to gradients in environmental variables. Diurnal visual censuses allowed us to record 2,602 juveniles belonging to 60 species and 1,543 adults belonging to 53 species from October to December 2005. The distribution of species highlighted that the juvenile community was organised into three distinct assemblages, rather than exhibiting gradual change in community structure along the cross-reef gradient. Correlations between spatial patterns of juvenile community and environmental variables revealed that the most significant factors explaining variation in community structure were coral rubble and coral slab. In contrast, the adult community was organised into one assemblage, and the most significant variation factors in community structure were depth, live coral in massive form, live coral in branched form, dead coral and sand. Overall, the present study showed that most juvenile and adult coral reef fish at Kudaka Island exhibited striking patterns in their distribution and depth and some biological factors (e.g., abundance of live coral, dead coral and coral rubble) might exert considerable influence on the distribution of fishes.

Bioturbation by burrowing macroinvertebrates has a major impact on sediment properties, pollutant redistribution, and biogeochemical cycling. We assessed the impact of bioturbation on the nutrient dynamics and organic matter of sediments receiving anthropogenic inputs in the Manko wetland, located in southern Okinawa, Japan. We compared sediments that were and were not subjected to the activities of the tidal-flat crab Helice formosensis . The fatty acid composition of sediments indicated that different sources contributed to the organic matter profile. Agricultural and domestic waste discharge seemed to induce a high amount of green macroalgae and bacteria in the tidal flat. Sediments without crabs exhibited 2.1–2.4× more NH 4 -N release, which was associated with a low C/N ratio during the summer. In the crab burrow sediments, NO 3 -N concentrations were 1.4–1.9× more pronounced during winter. A significant correlation existed between NO 3 -N and NO 2 -N concentrations in sediments of the burrow chamber (r = 0.837, p p H. formosensis thus contributes to balancing the effects of anthropogenic inputs by removing nitrogen loads in sediments.

Litter consumption by grapsid crabs enhances detritus turnover and nutrient cycling in mangrove ecosystems. However, unlike tropical mangroves, subtropical mangroves are subjected to pronounced seasonal changes in weather; particularly, low winter temperatures may slow down important ecological processes such as litter decay. This study aimed at evaluating the effect of temperature (low winter and high summer temperatures) on leaf litter consumption by two grapsid crabs (Parasesarma pictum and Helice leachi) in a subtropical mangrove forest of Okinawa Island, south Japan. We also tested whether leaf litter consumption between the low winter and summer temperatures could be affected by leaf species type and quality. A leaf-tethering technique was used to conduct field feeding experiments in the high and low intertidal sites of the mangroves using leaves of Bruguiera gymnorrhiza and Kandelia obovata. Leaves of different stages of decay: fresh (green), yellow, brown, two and four weeks were used. Results showed significant differences in leaf consumption between seasons, leaf species and shore heights. More leaves were consumed during summer than winter. In both seasons and shore heights, crabs consumed significantly more leaves of K. obovata than B. gymnorrhiza. Consumption was higher in the high than low intertidal mangrove. Although crabs preferred aged leaves in summer, during the winter season they consumed significantly more green leaves of K. obovata than yellow and brown leaves of B. gymnorrhiza. The slow litter processing during winter was consistent with lower carbon contents and lower C/N ratios in the surface sediments, signifying low input of organic matter. Results of this study suggest that temperature affects mangrove litter processing in Oura Bay mangroves, and consequently the amounts of organic matter and nutrients conserved inside subtropical mangrove sediments.

To investigate whether or not regional–temporal patterns of seagrass habitat use by fishes existed at the Ryukyu Islands (southern Japan), visual surveys were conducted in seagrass beds and adjacent coral reefs in northern, central, and southern Ryukyu Islands, in November 2004, and May, August, and November 2005, the northern region having less extensive seagrass beds compared with the central and southern regions. During the study period, the seagrass beds were utilized primarily by 31 species, the densities of some of the latter differing significantly among regions. With the exception of Apogonidae and Holocentridae, all species were diurnal and could be divided into 6 groups based on seagrass habitat use patterns; (1) permanent residents A (10 species, e.g. Stethojulis strigiventer ), juveniles and adults living in seagrass beds as well as other habitats; (2) permanent residents B (5 species, e.g. Calotomus spinidens ), juveniles and adults living only or mainly in seagrass beds; (3) seasonal residents A (4 species, e.g. Cheilodipterus quinquelineatus ), juveniles living in seagrass beds as well as other habitats; (4) seasonal residents B (6 species, e.g. Lethrinus atkinsoni ), juveniles living only or mainly in seagrass beds; (5) transients (5 species, e.g. Parupeneus indicus ), occurring in seagrass beds in the course of foraging over a variety of habitats; and (6) casual species (1 species, Acanthurus blochii ), occurring only occasionally in seagrass beds. Regarding temporal differences, juvenile densities in each group were high in May and August compared with November in each region, whereas adult densities did not differ drastically in each month. For regional differences, juvenile and adult densities of permanent residents A and B were higher in the southern and central regions than in the northern region. Moreover, some seasonal residents showed possible ontogenetic habitat shift from seagrass beds to coral reefs in each region. These results indicated that seagrass habitat use patterns by fishes changed temporally and regionally and there may be habitat connectivity between seagrass beds and coral reefs via ontogenetic migration in the Ryukyu Islands.

In the one-step method, fatty acid methyl esters (FAMEs) have been prepared without prior lipid extraction. Each oyster, clam, and squid sample was esterified with 14% boron-trifluoride (BF 3 ) in methanol at 100 °C for 120 min, and hexane was used to help dissolve the lipids. This method gave a higher recovery of fatty acids as compared to the conventional method. Using an internal standard, the fatty acid content of the sample can be determined quantitatively and qualitatively. Due to its simplicity, speed, and reduced organic solvent usage, the one-step method should be useful for the determination of fatty acid composition in marine biological samples.

Grapsid crabs are one of the most abundant and potentially the most important group of macrofauna inhabiting mangrove forests. A field study was conducted in the Manko wetland (Okinawa Island, southern Japan) to investigate how the burrowing crab Helice formosensis affects the sedimentary fatty acid (FA) and physicochemical characteristics of subtropical mangrove sediments. Multi-dimensional scaling (MDS) results from FA profiles revealed clear differences between burrow compartments and sediments with and without crabs. The impacts of burrowing were demonstrated by higher percentages of bacterial, vascular plant, and macroalgal FA markers in the burrow compartments and crab sediment areas. Conductivity and redox potential were significantly higher in sediments of the burrow opening shaft than in the burrow chamber. We found a similar pattern in surface sediments with crabs, but not in surface sediments without crab habitats. These results suggest that H. formosensis significantly influences the physicochemical properties, FA composition, and organic matter profiles of its surrounding environment.

The seagrass beds at Muk Island and Talibong Island in Thailand are important areas for dugong (Dugong dugon) feeding and reproduction. We used opportunistic observations during aerial surveys to investigate dugong mating behavior in shallow water areas near Talibong Island on three different days. The mating pattern was categorized by five stages: (1) following: the male followed the female, (2) approaching and stimulating: the male approached and muzzled the female, (3) pairing: both male and female swam in parallel, ventral to ventral or dorsal to dorsal side, (4) mounting: the male copulated with the female, and (5) separating: the male and female swam in different directions. Parental care of calves included one observation of a cow embracing her neonatal calf by the flippers.

An adaptive notch filter based on a second order IIR all pass filter uses a steepest descent algorithm whose cost function is the mean square of the error signal. However, there is a problem that bias error occurs in case that a broadband signal is color. In order to reduce the bias error for a FIR filter. SSCF (square sum of correlation function) adaptive algorithm has been proposed. This algorithm takes advantages of different auto correlation function between a narrowband signal and a broadband signal. By using a delayed input signal as an input signal of a cost function. In this paper, we introduce the SSCF algorithm into an adaptive IIR filter. In addition we consider the convergence condition of the SSCF algorithm for a second order IIR filter.

Mangrove forests provide several important ecosystem services including (1) storage of high quantities of organic materials and nutrients; (2) sources of organic material supply to coral reefs; (3) environmental purification functions via feeding behaviors of benthic animals; (4) refuge for young coral reef fish; (5) sites for marine leisure activities such as kayaking; (6) habitat provision to birds, insects, and other animal species; (7) opportunities for food resources; and (8) opportunities for environmental education including ecotours; and others. To clarify these services, a preliminary survey was conducted in Palau, where mangroves connected to coral reefs are dominant along the coast.

Fatty acid compositions of the leaves of six species of mangroves were studied to ascertain their use as biomarkers for determining the fate of mangrove organic matter in the habitat and as taxonomic tool. Mangrove leaves were collected from three locations in the western Pacific Ocean: Moreton Bay (MB) (Australia), Hong Kong (China) and Okinawa (Japan). In MB, samples were collected from two sites separated by 15 km: Logan River Estuary (LRE) and Jabiru Island. In addition, along the LRE, leaves were collected from five stations at ∼2–3 km apart. Results show that the analysis of the entire fatty acid profiles of the mangrove leaves is a promising taxonomic tool as the profiles of most species were sufficiently different to be separated in an non-metric multidimensional scaling plot. In addition, geographically separated populations of the same species could also be identified by their fatty acid profiles. In most cases, two non-ubiquitous groups of fatty acids dominated in the mangrove leaves: the polyunsaturated 18:2ω6 and 18:3ω3 and the long chain fatty acids (≥24:0). With respect to the relative contributions of these fatty acids, three groups of species were identified, in which one or both groups of fatty acids may potentially be used as markers of the mangrove organic matter in the estuarine environment.

The role of the opportunistically feeding gastropods Batillaria zonalis and B. flecto- siphonata on the material flux within tidal flat ecosystems was studied using a laboratory tide simu- lated system. Gastropods were cultured in the system for 2 wk using natural seawater; in one treat- ment the gastropods were restricted to suspension feeding only, while in the other they were free to engage in suspension and deposit feeding (dual feeding or opportunistic feeding). Clearance rates in both species were higher in the suspension feeding treatment than in the dual feeding treatment, and were maintained on a diet of high concentration particulate nitrogen (PN) in the water column. In the suspension feeding treatment, B. zonalis and B. flectosiphonata exhibited remarkable biodeposition on the surface sediment, as indicated by chlorophyll a (chl a), pheopigments (pheo), sediment PN and total organic carbon. In contrast, deposition was less evident in the dual feeding and control (no gas- tropods) treatments. 'Freshness', as indicated by the chl a:pheo ratio in the surface sediment, was higher in the control than in the other treatments. The removal rate of suspended PN by B. zonalis and B. flectosiphonata was variable, although uptake from the suspended matter was 0.7 to 2.0 times greater than that of deposited matter. We conclude that these opportunistically feeding gastropods play a significant and unique role in biodeposition by accumulating organic materials on the surface sediment during suspension feeding, and in decreasing the biodeposition by ingesting the bio- deposited materials during deposit feeding.

Under bleaching conditions, corals lose their symbiotic zooxanthellae, and thus, the ability to synthesize fatty acids (FAs) from photosynthetically derived carbon. This study investigated the lipid content and FA composition in healthy and bleached corals from the Odo reef flat in Okinawa, southern Japan, following a bleaching event. It was hypothesized that the FA composition and abundance would change as algae are lost or die, and possibly microbial abundance would increase in corals as a consequence of bleaching. The lipid content and FA composition of three healthy coral species (Pavona frondifera, Acropora pulchra, and Goniastrea aspera) and of partially bleached and completely bleached colonies of P. frondifera were examined. The FA composition did not differ among healthy corals, but differed significantly among healthy, partially bleached, and completely bleached specimens of P. frondifera. Completely bleached corals contained significantly lower lipid and total FA content, as well as lower relative amounts of polyunsaturated FAs and higher relative amounts of saturated FAs, than healthy and partially bleached corals. Furthermore, there was a significantly higher relative concentration of monounsaturated FAs and odd-numbered branched FAs in completely bleached corals, indicating an increase in bacterial colonization in the bleached corals.

Changes in the concentration of total lipid and fatty acids (FAs) during the decomposition of mangrove leaves were investigated by field experiments using yellow leaves of Bruguiera gymnorrhiza (L.) Lamk. and Kandelia candel (L.) Druce, in order to quantify mangrove contribution to lipid and fatty acid inputs to marine sediments. Total lipid and total FA in the fresh (green and yellow) and decomposing leaves of both species were significantly higher during winter than summer. During decomposition, total lipid content and FA concentration, in particular branched chain fatty acids (BrFAs) and bacterial fatty acids (BFAs), increased to a maximum concentration in 45 days during winter and in 17 days during summer. Lipids were lost faster in K. candel leaf detritus than in B. gymnorrhiza leaf detritus in which >90% of the total lipid original weight was lost during the summer experiment and

Total mass flux, size distribution of sediment particles and some chemical compo- nents such as total carbon (TC), total nitrogen (TN) and calcium carbonate (CaCO 3 ) were monitored monthly using a multi-cup sediment traps at seven coral reef sites (6 reef flat and 1 reef slope) of the Marine Protected Areas around Ishigaki, Kohama, Kuroshima and Iriomote Islands in the southern Ryukyus, Japan from September 2000 to September 2001. The size distribution of trapped sediments revealed mostly uni-modal fine sand to mud in the reef flat and gravelly to coarse sand in the reef slope. The total mass flux ranged between 0.54 to 872 gm -2 d -1 , and showed a pro- nounced seasonality (high in summer-autumn and low in spring) at each site, which was consistent with the rainfall and typhoon regime. Exceptionally high values were observed on the reef slope (Iriomote) in February-March 2001 (1533 gm -2 d -1 ) owing to a large amount of bottom sediment re-suspension. On the reef flat (Todoroki South and North; Ishigaki), values obtained in July-August 2001 (872 gm -2 d -1 ) and Au- gust-September 2001 (800 gm -2 d -1 ) indicate the high terrestrial discharge from Todoroki River. Trapped sediment particles consist of CaCO 3 (1.2-27.1%) and a non- carbonate fraction (98.8-72.9%), which contains total carbon (4.9-26%), carbonate carbon (CO 2 -C) (0.2-3.1%) and non-carbonate carbon (NC-C) (7.9-25.6%). Total nitrogen content was in the range 0.02-0.48%. TN is contained mainly in the carbon- ate fraction and NC-C may be contained in the non-carbonate fraction. The low TN/ OC ratio of the trapped sediments suggests that they were mostly of terrestrial origin and that both fractions migrated. The high total mass flux derived from Todoroki River exceeded the threshold at which a lethal effect on coral community is caused. The results stress the importance of conducting seasonal studies of sedimentation over more than one year and at more than one location in south Japan coral reef ecosystems to gain an understanding of the processes controlling the total mass fluxes and their nutrients content, also to develop an awareness of how to prevent the dam- age of coral reef ecosystems and, if it does occur, to allow mitigation measures to be undertaken.

Litter dynamics and outwelling of particulate organic matter (POM) was investigated in a subtropical mangrove (Okinawa Island, South Japan) in order to quantify the impact of mangrove POM on adjacent intertidal sediments. A distinct seasonal pattern was found with maximum litter fall during the autumn season, and minimum during winter. Total litter production between sites did not differ significantly. Tall mangroves (average 7 m) did not show any higher contribution to the litter production than short mangroves (average 4 m). The mean annual litter production was 12.95 ± 2.95 t ha−1 (dry weight) with leaf fall contributing more than 70% of the total litter production. Analysis of fatty acids (FAs) in the surface sediments of an adjacent mud flat and sand flat during the winter, spring and autumn seasons indicated that outwelling of POM from the mangrove ecosystem occurs. However, it is spatially restricted to within 300 m from the mangrove forest. The magnitude of the outwelling increased during spring and autumn consistent with the increase in the total litter production. Despite the presence of mangrove-derived organic matter in the estuarine surface sediments, autochthonous sources of organic matter, green macroalgae (Ulva pertusa and Enteromorpha intestinalis), diatoms and bacteria are the main contributors of sedimentary organic matter and ω3 and ω6 PUFAs than mangrove-derived (POM) during winter and spring. While the contribution of mangrove-derived POM to sedimentary organic matter is limited to the autumn season.

Lysozyme acts as a non-specific defence substance and is found in the peripheral blood, cutaneous mucus and certain tissues of marine and freshwater fishes. In the present study, we examined the effect of various environmental factors (water temperature, salinity, pH and suspended sediments) on plasma lysozyme activity in the Nile tilapia, Oreochromis niloticus L. When the fish were reared at different water temperatures (18.4, 23, 28 and 33 degrees C), plasma lysozyme activity increased at 28 degrees C after 2 and 4 weeks. A significant decrease in lysozyme activity was found in the fish reared at 33 degrees C for 4 weeks. These results suggest that there is a water temperature range that affects the amount of plasma lysozyme activity that can be detected. Fish cultured at 24 g L(-1) of salinity for 2 and 4 weeks and 12 g L(-1) for 4 weeks resulted in significantly increased plasma lysozyme activity, suggesting that environmental salinity also affects the amount of plasma lysozyme that can be detected. Lysozyme activity also significantly increased when the fish were held in acidic water at pH 4.0 and in suspended sediments at 2000 mg L(-1) for 2 weeks. It was concluded that changes in some aquatic environmental factors affect the non-specific immune responses of Nile tilapia.

Effects of short-term sedimentation on common coastal coral species, Goniastrea aspera, Porites lobata and Pavona frondifera, from the reef flat southeast of the Ryukyu Islands, Okinawa, Japan were investigated in laboratory experiments using oxygen uptake respirometers. The O2 consumption rate was significantly different among species and between sediment treatments (20 and 200mg l-1 red soil suspension, P

Immunoglobulin M (IgM) in teleost fishes is the only component of the specific humoral defense system that is affected by environmental factors. In the present study, we examined the effect of various environmental factors (water temperature, salinity, pH and suspended solids) on the plasma IgM in the Nile tilapia, Oreochromis niloticus. For all treatments, fish were acclimatized in particular environmental conditions for 2 or 4 weeks. For fish reared at 18.4, 23 and 28 °C, the circulating IgM concentration increased with increased water temperature for 2 weeks. Rearing the fish at 33 °C resulted in a decrease in IgM concentration, suggesting that the fish possess an appropriate thermal range for production of immune substances. Plasma level of IgM increased significantly with salinity at 12 and 24 parts per thousand (ppt). On the other hand, plasma IgM concentration did not change by exposing the fish to acidification (pH 4.0) and suspended solids (20, 200, and 2000 mg/l). These results suggest that the specific immune system of tilapia changes by certain factors in aquatic environment.

Feeding behaviors of the gastropods Batillaria zonalis, a suspension and deposit feeder, and Cerithideopsilla cingulata, an obligate deposit feeder, were studied to examine their effect on dynamics of suspended materials, total nitrogen (TN) and total organic carbon (TOC) in sediments. Suspension feeding in B. zonalis was observed in detail visually, as it had been previously unreported. An experimental system where B. zonalis and C. cingulata were cultured for 10 weeks, using previously frozen microalgae Nannochloropsis oculata as food, was then constructed. During feeding observations, the suspension-feeding B. zonalis formed a mucus “food cord” to entangle particulate materials, which were subsequently ingested. The feeding mode of B. zonalis is hence categorized as ctenidial filter feeding. For the culture experiments, decreases in suspended materials were seen only in the B. zonalis cultures, while the control (no gastropods) and C. cingulata cultures remained nearly unchanged. Sediment TN and TOC showed no significant differences between B. zonalis (with mean TN at 0.0345% and mean TOC at 0.261%) and control cultures (with TN at 0.0389% and TOC at 0.331%), but the sediments in C. cingulata cultures had lower levels (with TN at 0.0204% and TOC at 0.156%). The C/N ratios were similar for both B. zonalis (7.55) and C. cingulata (7.68) cultures, and both were lower than the control cultures (8.55). The filtration rate for B. zonalis was lower than that previously observed in bivalves inhabiting the same intertidal flat (e.g. Cyclina sinensis, Grafrarium tumidum and Barbatia virescens). However, Batillaria zonalis occurs at higher abundances than these bivalves. Therefore, it is expected that this species has a large affect upon the transport of suspended materials to the sediments. The addition of TN and TOC to sediments in B. zonalis cultures was probably caused by biodeposition, but deposit feeding by B. zonalis may have restrained the accumulation of those components. The impact of deposit feeding in Cerithideopsilla cingulata cultures was most probably stronger than sedimentation and biodeposition, because of the lower sediment TN and TOC. Bioturbation by both B. zonalis and C. cingulata yields the same effect on sediment quality, as indicated by the low C/N in the culture sediment of both treatments, despite difference in feeding modes. This paper demonstrates, for the first time, the importance of gastropods in bioturbation and removal of suspended materials in subtropical tidal flat habitats.

Fatty acid compositions in the tissues of the clam Geloina coaxans collected from Oura mangal, Okinawa, Japan, during the cold and warm seasons (January and July 2001, respectively) were compared with those in suspended materials (SM) in order to assess the clams' diet. In both seasons, the suspended mangrove detritus at the sediment–water interface was high as indicated by the mean percentage of even-numbered long-chain fatty acids in SM (12.8–18.4%). The contribution of this marker in the clam tissues, especially during the cold season (3.9%), indicates the consumption of mangrove detritus in considerable amounts by the clams. The occurrence of the fatty acids 16:1ω7, 18:1ω9, 18:2ω6 and 18:3ω3 in SM was most likely due to the mangrove detritus sources, whereas in the SM they together constituted 12.9% and 23.9% of total fatty acid contents during the cold and warm seasons, respectively. As a result, their contribution in the clam tissues was high in the cold (15.4%) and warm seasons (19.0%). These results indicate that mangrove detritus play a significant role in the clams' diet. The mean percentages of bacterial markers (odd-numbered branched fatty acids and vaccenic acid, 18:1ω7) in the SM and tissues during both seasons ranged from 8.1% to 9.5%. This indicates that the clam diet is also dependent on the attached bacteria on the partially decomposed leaf detritus suspended at the sediment–water interface. The relative contribution by microalgae markers (18:4ω3, 20:5ω3 and 22:6ω3) in clam tissues ranged from 4.3% to 7.6%, suggesting considerable microalgae sources in the diets.