Middle Intertidal Zone Research Articles

Root Effect of Three Vegetation Types on Shoreline Stabilization of Chongming Island, Shanghai

Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis + Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. ascendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20–30 cm soil depth of the middle intertidal zone and in the 10–20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher ( P < 0.05) than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher ( P < 0.05) than those of other vegetation conditions at the 30–40 cm soil depth for the lower intertidal zone and at the 20–40 cm layer for middle and higher intertidal zones.

A study on seed characteristics and seed bank of Spartina alterniflora at saltmarshes in the Yangtze Estuary, China

Since Spartina alterniflora was introduced into the Chongming Dongtan Nature Reserve in 1995, there has been a rapid expansion of this species, seriously threatening the overall biodiversity. In this study, the seed production, germination characteristics and soil seed bank of S. aterniflora were studied at the nature reserve along an intertidal gradient where this invasive species distributed and spread. The results showed that the middle intertidal zone (MIT) had the largest seed production and higher viability than those of lower (LIT) and higher (HIT) intertidal zones. The differences in seed production among these sites were largely dependent on the higher percentage of fruiting culms, longer spike and higher seed number per spike. The differences in seed viability among these sampling sites seemed largely dependent on the higher seed weight at the site MIT. The chilling treatment (at low temperature and in moist conditions) could significantly enhance the germinability of S. alterniflora seeds and shorten the time of onset seed germination. The seeds from the site MIT had much higher germinability than the sites LIT and HIT. The highest density of soil seed bank was recorded at the site of MIT, where had the highest seed production. By July, before there was any replenishment with fresh seeds from the current year, the soil seed bank was completely exhausted and the persistent time of soil seed bank for S. alterniflora was less than 9 months, which is in agreement with that of the transient seed bank. The results from this study indicated that the seed propagation could have an important attribution to the spreading of this invasive plant and the implications in terms of controlling and managing the invasion of S. alterniflora at the nature reserve were discussed.

한국 일광만 저서 해조류의 해조상과 군집구조

Marine algal flora and community structure were investigated seasonally at three sites in Ilkwang Bay on the southern east coast of Korea from May 2007 to February 2008. Total 103 species including 10 of green algae, 17 of brown algae, 76 of red algae were collected and identified. Among these species, 21 species were found throughout the year. Ulva pertusa, Enteromorpha linza, Grateloupia lanceolata, Chondracanthus intermedia and Caulacanthus ustulatus were distributed dominantly in upper intertidal zone. By contrast, crustose coralline algae, Grateloupia spp., Chondracanthus tenellus, Prionitis cornea and Sargassum spp. occurred predominantly in middle intertidal zone. Grateloupia spp., Sargassum spp., Ecklonia cava and Ulva pertusa were dominant in lower intertidal zone. Annual mean biomass in wet weight was 478.3 g m. Maximum biomass was recorded in site 1 (731.8 g m), and minimum was recorded in site 3 (78.5 g m). The R/P, C/P and (R + C)/P value reflecting flora characteristics were 4.47, 0.59 and 5.06, respectively. Two groups produced by cluster analysis, one including sites 1, 2 and the other including site 3, showed meaningful difference in similarity, each other. Site 3 showed the limited species composition due to inflow of fresh water and absence of solid substratum. However, there was no significant difference between site 1 and site 2. In conclusion, the number of marine algae species and biomass in Ilkwang Bay were markedly reduced comparing with the previous studies. These suggest that a solution for reconstruction of the poor marine algal vegetation is considerably demanded.

한려해상국립공원의 해조상

This study elucidated the floral composition of marine algae and community structure at Hallyeo-haesang National Park, on the southern coast of Korea. In all, 89 species, comprising 10 green, 30 brown and 49 red algae, were identified. The dominant species in terms of importance value were Ulva pertusa, Colpomenia sinuosa, Undaria pinnatifida, Padina arborescens, Hizikia fusiformis, Sargassum sagamianum and Amphiroa dilatata. The vertical distribution of marine vegetation was characterized by Enteromorpha linza - Ulva pertusa - Gelidium divaricatum in the upper intertidal zone, Hizikia fusiformis - Sargassum thunbergii in the middle intertidal zone, and Amphiroa spp. - Hildenbrandtia rubra - Corallina pilulifera in the lower intertidal zone. Functional form group analysis showed that coarsely branched forms comprised 50.3% of the algal community, whereas thick leathery forms, sheet forms and filamentous forms comprised 11.9-13.1%. R/P, C/P and (R+C)/P values were 1.91, 0.74 and 2.64, respectively. A cluster analysis of species occurrence suggested that the number of marine algal species differed greatly among the sampling sites.

Microdistribution of juveniles and adults of the mud crab Panopeus americanus (Brachyura, Panopeidae) in a remnant mangrove area in the southwest Atlantic

The distribution and density of a population of the narrowback mud crab Panopeus americanus were evaluated, with emphasis on the different developmental stages (juveniles and adults) and sexes. Specimens were collected in a remnant human‐impacted mangrove at Araçá on the northern coast of São Paulo, Brazil, at two‐month intervals from January through July 2006, using 1 m×1 m sample plots randomly distributed in the intertidal zone. The population was abundant, with a mean density of 14.3±9.3 individuals/m2. Larger individuals were more abundant in the upper and middle intertidal zones, whereas smaller crabs were predominant in the lower intertidal and thus remained submerged longer. Males and juveniles were homogeneously distributed. Females preferred regions farther from the waterline. A clustered distribution pattern suggested gregarious behaviour and settling of juveniles in the vicinity of the adults' habitats, in an adaptive process as a function of tidal rhythms.

New Record of Sargassum filicinum Harvey (Fucales, Phaeophyceae) in the Pacific Coast of Mexico

Sargassum filicinum Harvey, a brown alga (Phaeophyceae) native to Northeastern Asia, has been recently reported from the coast of Southern California (USA). Here we report the occurrence and range extension of this introduced species, as we found the alga at La Jolla and Rancho Packard in Todos Santos Bay, Baja California, Mexico. The first collections of S. filicinum correspond to several immature plants, found on September 8, 2005, drifting in the intertidal zone at La Jolla. Later on November 9, 2006, we found a well-established population in Rancho Packard in the middle intertidal zone to 2 m depth. Since S. filicinum is an annual monoecious species with air bladders, the risk there is a high risk of spreading rapidly along the Pacific, as in the case for S. muticum. The population in Rancho Packard extends 500 m along the coast, consisting mainly of young plants with an average length of 30 cm and a density of 5 thallus/m2. This is the first record of this invasive species for the Mexican Pacific coast, and it represents the southern limit along the Pacific coast of North America. This finding suggests that this invasive species has successfully colonized the Pacific coast of North America and its distributional range is still expanding.

An Ichnological and Sedimentological Facies Model for Muddy Point-Bar Deposits

Abstract Detailed analysis of fine-grained clastic deposits associated with the macrotidal estuarine mouth of the Shepody River, New Brunswick, Canada, concentrated on identifying the ichnological and sedimentological characteristics of tidally dominated point bars and their adjacent tidal flats. The aim of the study was to establish an ichnological facies model for similar deposits. Within the study area, the distribution of ichnological structures and sedimentary characteristics such as grain-size distribution and total organic content are associated with bar elevation (i.e., upper, middle, or lower intertidal), tidal-bank slope, and the local hydraulic processes. The distribution of animal traces is also influenced by the duration of intertidal exposure and sedimentation rates. Polykladichnus- and Skolithos-like traces characterize upper-subtidal and lower-intertidal zones of the point bars; Arenicolites-, Diplocraterion-, Polykladichnus-, Palaeophycus-, and Planolites-like forms are pervasive in middle-intertidal zones; and, Siphonichnus- and Polykladichnus-like burrows typify the upper-intertidal point bars and the tidal flats. The size and diversity of the burrowing fauna are affected by the chemistry of the depositional waters and by seasonal variations in composition and temperature of those waters. The extreme seasonality of the area favors opportunistic fauna and thereby contributes to an impoverished, brackish-water trace assemblage. Geomorphologically, the area is dominated by point-bar and tidal-flat deposits, which comprise rhythmic bedding, composed of interlaminated to thinly interbedded silty and sandy mud. Point-bar bedding dips channelwards and represents mud-dominated inclined heterolithic stratification (IHS). The IHS alternates between burrowed and laminated beds. Laminated beds contain rhythmic lamination. Cyclic variations in laminae thickness are attributed to neap–spring variation in tidal-current strength. The burrowed interbeds exhibit high degrees of bioturbation that eradicate the preexisting lamination. The intercalation of laminated and burrowed beds represent seasonal variations in the depositional system: laminated beds characterize early winter and early spring sedimentation, and the bioturbated beds represent late spring through fall deposits.

Seasonal dynamics of the populations of intertidal harpacticoids (Harpacticoida: Copepoda) in the White Sea

In May to October 2001, seasonal variations in the population structure of four species of intertidal harpacticoids—Paraleptastacus kliei, Huntemannia jadensis, Heterolaophonte minuta, and Stenhelia palustris—were studied at three sites in the middle intertidal zone of Chernorechenskaya Bay (White Sea) with different sediment compositions. At different sites, the changes in the harpacticoid abundance, and the times and amplitudes of the peaks were different. The features of the local dynamics of the population are determined both by the intensity of its reproduction at the reproductive habitats and by the intensity of subsequent migrations. A comparison of the data available on the seasonal dynamics of the intertidal harpacticoids at various latitudes allows one to suggest that they are mainly determined by the temperature regime.

Comparison of mussels and semi-permeable membrane devices as intertidal monitors of polycyclic aromatic hydrocarbons at oil spill sites

Side-by-side comparisons of polycyclic aromatic hydrocarbon (PAH) concentrations in resident blue mussels ( Mytilus trossulus) and in semi-permeable membrane devices (SPMDs) were made at four sites in Prince William Sound, Alaska. SPMDs were deployed for ∼30 days on the surface of the beach sediment at three tidal elevations on each shore and in 0.5 m deep open pits in the middle intertidal zone. Total PAH (TPAH) concentrations in mussels and in SPMDs were correlated, but the PAH compositions were different. The lower molecular weight PAH were relatively more abundant in the SPMDs than in the mussels at oiled and HA sites. TPAH concentrations in SPMDs deployed in pits and mussels collected adjacent to those pits at oiled sites were higher than in SPMDs and mussels from non-pitted SPMD locations ∼3–15 m from the pits. Pitting released buried oil making its PAH bioavailable. SPMDs deployed in the supratidal zone (+4.0 m tidal elevation) were exposed to atmospheric contaminants for a large fraction of the deployment time and accumulated primarily pyrogenic (combustion-sourced) PAH from the atmosphere. The SPMD strips supplied by the manufacturer contained significant amounts (∼125 ng/strip) of primarily alkylated 2–3 ring PAH. These blank levels make SPMDs unsuitable for shoreline assessments when environmental PAH concentrations are low. Consequently, where available, mussels are recommended for use in assessments of the bioavailability of buried oil residues sequestered in intertidal sediments following an oil spill. Mussels are the preferred monitoring tool when the assessments involve food-chain effects. At locations where the absence of mussels necessitates the use of SPMDs or other passive sampling devices, their limitations need to be carefully considered in the interpretation of results.

Morphology of the spermatozoon of the limpet Fissurella crassa Lamarck, 1822 (Mollusca: Vetigastropoda)

Summary Fissurella crassa is a keyhole limpet, which inhabits the middle rocky intertidal zone of the southwest coast of South America. The present study details the ultrastructure of the spermatozoon of this species. These cells are of the aquasperm type, typical of species that release free gametes into seawater. The conical head of the spermatozoon contains a truncated conical, elongated nucleus with a subconical acrosome with a rounded anterior tip, and a deep subacrosomic space. The midpiece of the spermatozoon is typically formed of six mitochondria arranged in a ring around the proximal and distal centrioles, from which emerges the 9 + 2 axoneme of the flagellum. The spermatic morphology is characteristic by the shape and size of the nucleus and acrosome, showing two differentiated zones and a deep subacrosomic space, which are valid taxonomic criteria to distinguish F. crassafrom other fissurellid species.

이원방조제 주변의 조간대 및 조하대 대형저서동물의 군집과 환경요인과의 관계

Spatial patterns in the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike and environmental variables were examined in August 2001, In total, 156 macrobenthic species(123 intertidal species and 90 subtidal species) were recorded during this study, predominately polychaetes , bivalves , and crustaceans . Polychaetes made up less than of the intertidal communitr, but more than of the subtidal community. The mean density during this study was Multivariate analysis (multidimensional scaling) revealed significant differences in community structure among four regions: near the Iwon dike (B1), the high and middle intertidal zone (B2), low intertidal zone (Al), and subtidal zone (A2). The number of species, total density, and diversity (H`) varied significantly among the four regions. The distribution of macrobenthic community was affected by environmental variables, such as silt/clay content, total sulfide, lose of ignition, and chemical oxygen demand. These environmental variables were negatively correlated with the dominant species (Nephtys polybranchia, Umbonium thomasi, and Scoloplos armiger) in the intertidal area, but positively correlated with the dominant species (Lumbrineris cruzensis, Notomastus latericeus, and Moerella sp.) in the subtidal area. Environmental variables were positively correlated with the dominant species (Heteromastus filiformis) in region Bl, but negatively correlated with the dominant species (Umbonium thomasi and Scoloplos koreanus) in region B2. Amphipods Urothoe spp. and Monoculodes koreanus were the dominant species in region Al. Umbonium thomasi, the dominant species in region B2, was not found in regions Bl or Al. We suggest that the inter-specific competition for territory and exposure to seawater may be important factors controlling the macrobenthic community structure in the inter- and subtidal zones in front of the Iwon Dike.

Density‐Dependent Effects in Jehlius cirratus (Darwin, 1854) (Cirripedia: Chthamalidae) under Different Growth Conditions

Abstract. We analyse the effects of crowding (‘hummocking’) on the growth, reproduction and mortality of the chthamaloid barnacle Jehlius cirratus (Darwin, 1854) on the coast of Chile. Recruitment intensity, ranging from solitary individuals to dense groups, generates different growth conditions. Density‐dependent effects are reflected in the shape, growth parameters, fecundity, sexual maturity and mortality of solitary and crowded specimens. The skewing of size distribution during growth was not significant at the beginning of the growth period, irrespective of initial density. Nevertheless, skewness in size increased with time, both at high and low densities, indicating that the dominance and suppression exerted by larger specimens over smaller ones generate a density‐dependent effect on size during growth. Mortality was greatest when high‐density recruitment occurred immediately before the period when water temperature and food quantity are highest (spring), when it is assumed that growth is greatest; this seasonal effect was not detected at lower levels of recruitment density. Similarly, no differences in mortality were detected between recruitment densities during the period when temperatures are lowest (autumn) and growth is probably slower. In the middle‐high intertidal zone, where J. cirratus co‐exists with Notochthamalus scabrosus (Darwin, 1854), the proportion of dead J. cirratus specimens was directly related both to the relative abundance of N. scabrosus and the total barnacle density. Although the mortality of J. cirratus was density dependent, the increase in the number of N. scabrosus towards the lower section of the middle intertidal zone could have a greater effect on J. cirratus mortality than intra‐specific competition.

汽水棲巻貝ワカウラツボ（腹足綱：ワカウラツボ科）の分布に関係する要因

Factors affecting the spatial distribution of the brackish water snail Iravadia (Fairbankia) sakaguchii were investigated in the field in the Waka River Estuary (34°10'N, 135°10'E) of central Japan and in the laboratory. The snails occurred under stones partially buried on intertidal muddy flats. A tracking survey of marked snails released beneath stones revealed that many of the snails moved among the stones. Observations in tide-simulating tanks indicated that most of the snails came out from beneath the stones and were active during both daytime and nighttime submergence. Salinity tolerance tests in the laboratory showed that the snails died within 6 days at 0 psu, 7 days at 5 psu, and 12 days at 10 psu, whereas no snails died during 13 days of exposure to higher salinity conditions (20-35 psu). Neither immigration nor retention rates of snails differed significantly between partially buried stones and non-buried stones artificially placed in the field. This indicates that the extent of burial of the stones is not critical for habitat selection by the snails. Preference tests conducted in the laboratory and in the field revealed that the snails prefer mud to sand under the stones. Retention and survival rates were lower for snails released with stones in the lower intertidal zone than for those released with stones in the middle intertidal zone, and this suggests the importance of tidal exposure in habitat selection of I. (F) sakaguchii.

The Cellular Ability of Desiccation Tolerance in Japanese Intertidal Seaweeds

Photosynthetic activities of submerged seaweeds before and after drying were measured in eighteen species collected from different vertical positions from a Pacific shore at Shimoda City in Japan. The seaweeds were desiccated until the cellular water levels equilibrated with the air in the chamber under various humidities at 10 °C. Relative water contents of all species drastically decreased as the cellular water potentials were reduced from 0 to −14MPa and gradually decreased in the range from −14 to −158MPa. Porphyra dentata, which is an upper intertidal species, recovered photosynthetic activity from the lowermost water potential of −158MPa, while the plants collected from the lower intertidal and subtidal zones reduced their photosynthetic activities after desiccation to comparatively higher water potentials from 0 to −14MPa. Other species collected from the middle intertidal zone reduced their photosynthetic activities following desiccation to water potentials in the range from −14 to −158MPa. It is concluded that the cellular abilities of desiccation tolerance in intertidal seaweeds varied between the species examined and correlated with their vertical position within the tidal zone.

Spatial distribution of algae and invertebrates in the rocky intertidal zone of the Strait of Magellan: are patterns general?

Spatial variability in the distribution of macroalgae and invertebrates was examined at a number of sites in the Strait of Magellan. Two main predictions of models of zonation were tested in this study: (1) consistency in patterns of vertical distribution among sites one to tens of kilometers apart, and (2) homogeneity between areas at the same level on the shore, tens to hundreds of meters apart. Two types of habitat were considered: continuous rocky shores and blocks of rock in gravel beaches. In the former habitat, percent cover estimates of sessile organisms (algae and mussels) were obtained from three replicated plots (0.5 × 0.5 m) sampled non-destructively in each of three random areas (stretches of shore about 20 m long) at each of three levels on the shore: high, middle and low intertidal zone. This procedure was repeated at six different sites along the Chilean coast of the Strait of Magellan. Blocks of rock were sampled at two sites about 1 km apart. Estimates of the abundance of sessile (barnacles and mussels) and mobile (limpets) organisms were obtained for six blocks at each of two levels on the shore (high and low intertidal zone) at each site. At each level on the shore, three blocks were sampled on the top and three on the vertical sides. A single plot was sampled on each block. This design allowed a test of the null hypothesis of no interactive effects between position on the blocks and level on the shore. Both the predictions were falsified: (1) there were large between-site differences in the vertical structure of assemblages and (2) variability between areas at the same level on the shore was large for some of the most common algae. In contrast, the null hypothesis of no interactive effects of position on the blocks and level on the shore was retained. The results of this study show that vertical position on the shore alone is not a good predictor of the structure of assemblages of benthic organisms in the rocky intertidal of the Strait of Magellan.

The unique intertidal subterranean habitat and filtering system of a limpet-like brachiopod, Discinisca sparselineata

Living limpet-like brachiopods, Discinisca sparselineata (Inarticulate), were found in a unique intertidal subterranean habitat in the Seto Inland Sea, Japan. They were attached beneath boulders that were deeply buried in coarse sand in the middle intertidal zone, and were accompanied by a characteristic sessile epifauna. The habitat was protected from ultraviolet light, desiccation, turbidity, physical turbulence by harsh waves, disturbance by rock-scraping epiphyte-grazers, and from predation by carnivorous snails, seastars, and fishes. The filter-feeding mechanism is unusual in that water enters the mantle cavity frontally and exits laterally through lateral filaments and dorsally through ventrally directed spires as in D. strigata, which is distributed on the Pacific coast of Central America. However, D. sparselineata inhabits more protected habitats and has less capacity for spatial competition than D. strigata.

Distribution, reproduction and shell utilization patterns in three species of intertidal hermit crabs on a rocky shore on the Pacific coast of Japan

The spatial distribution, reproduction, and shell utilization patterns of three species of common intertidal hermit crabs Pagurus geminus McLaughlin, Pagurus lanuginosus De Haan and Clibanarius virescens (Krauss) on a rocky shore of Kominato, Boso Peninsula, Japan, are described. Although the distribution of each species greatly overlapped, Pagurus geminus mainly inhabited the middle intertidal zone, with Clibanarius virescens occupying a lower and Pagurus lanuginosus the lowest zone. This pattern was maintained over a 1-yr period with a few minor changes. Female Pagurus geminus generally inhabited a lower zone than males, ovigerous female Clibanarius virescens were distributed slightly lower than males, whereas a distinct sexual difference in the distribution was not seen in Pagurus lanuginosus. The ovigerous period of Pagurus geminus extended from October to August and is the longest reproductive season reported for a rocky intertidal decapod in Japanese waters. Pagurus lanuginosus became ovigerous from December to May and Clibanarius virescens, from April to December. The sex ratio was biased toward females in each case. Shell utilization patterns differed significantly between the three species, with Clibanarius virescens using the greatest variety of shells (33 species). Within species, sexual differences in shell utilization were seen in Pagurus geminus and Clibanarius virescens.

Stable Carbon Isotopic and Gut Content Analyses of a Tidal Flat Food Web

The tidal flat at the mouth of the Obitsu River is one of the best areas for ecological research around Tokyo Bay. Annual variation in the biomass, collected 1 m grid units, showed that the seagrass Zostera japonica which grows at the middle intertidal zone along the river route, has a great influence on the ecosystem. During the summer it forms zostera beds, providing a good habitat for fauna, while during the winter most of the grass disappears except for the roots. The benthonic diatom fractions also increase during the summer. Analysis of the gut contents showed that Batillaria cumingii contained Cocconeis scutellum, a benthonic diatom which lives on Zostera japonica, while the gastropod Umbonium moniliferum and the bivalves Tapes japonica, Mactra veneriformis, Mactra chinensis, Dosinia Japonica and Solen strictus, on the sandy bottom of the lower tidal zone, contained a wider composition of benthonic diatoms. Stable carbon isotopic analysis showed that the primary producers in the Obitsu River tidal flat consisted of benthonic diatoms (-19 to-16‰), seagrasses (-11 to -14‰) and salt marsh plants (-26.5 to -24.5‰). 13C ratios for the Batillaria cumingii from the zostera beds were about 1.5‰ higher than for benthonic diatom fractions from the same location. 13C ratios for the other primary or higher consumers are between the ratios of the benthonic diatom fractions and the zostera, suggesting that they have a mixed diet.

Environmental characteristics and distribution of macrobenthos in a mudflat of the west coast of Korea (Yellow Sea)

The spatio-temporal changes of environmental factors and the distribution patterns of macrobenthos were investigated on an intertidal mudflat near Panweol on the west coast of Korea. Temperatures of the surface sediments and salinities of the intertitial water were highest in summer and lowest in winter, while water content of the sediment was lowest in summer and highest in winter. Hourly variations of sediment temperature, water content and interstitial salinity during the daytime depended largely upon both the timing of ebb tide and daylight intensity. Temperature, water content and interstitial salinity showed a marked variation with sediment depth. Temperatures decreased sharply from the surface to 10 or 15 cm depth, and below this depth they were nearly constant, except in summer. Water content and interstitial salinity underwent a rapid decline in this upper layer and began to rise from this depth. From the high tide mark toward the main tidal channel, water content increased but salinity decreased. The sand fraction increased with the decrease of clay content toward the main tidal channel. This tidal flat could be divided into two zones: the “upper intertidal zone” and the “lower intertidal zone”, based on the spatial differences of the water content, interstitial salinity and grain-size composition in the surface sediment. There were three distinct zones of macrobenthos. The upper intertidal zone was dominated by burrowing deposit feeders, such as Ilyoplax dentimerosa, Helice tridens sheni, Cleistostoma dilatatum and Perinereis vancaurica tetradentata. The middle intertidal zone was characterized by other burrowing deposit feeders, such as Ilyoplax pingi, Macrophthalmus japonicus and Periserrula leucophryna. And the lower intertidal zone was dominated by suspension feeders represented by Laonome tridentata and Potamocorbula amurensis. Each zone was named after these characteristic species. Although the species composition of the upper intertidal community was different from that of the middle intertidal, the way of living and the feeding behaviour of the species occurring in these two zones were very similar. But the lower intertidal zone showed a characteristic community structure differing not only in species composition but also in ways of living and feeding of the species. Some sets of environmental factors are considered to explain the zonation. Water content of the sediment and interstitial salinity will be the main factors causing the observed zonation.

Effects of Sewage Outfalls on Intertidal Ecosystems in Kuwait

Kuwait City has an impact on the nearshore marine environment by discharging sewage randomly through short emergency outfalls into the intertidal zone. The effect of the discharged sewage on the biological activity and the chemical characteristics of the relevant intertidal areas, which are controlled by a dry, tropical climate, was studied. Pore water, tidal water characteristics and nutrient release and transport from the intertidal zone during tidal flushing were investigated in polluted and unpolluted areas. The accumulation of particulate organic matter in the upper, middle and lower intertidal zones was characterized. It was concluded that in addition to settling, a great deal of particulate organic matter entered into the upper tidal sediment by infiltration during high tide and was filtered out by the sediment and migrated toward the low tide zone during the falling tide. The rate of the release of the substances associated with inorganic particulates was controlled by the overall organic load and the microbial activity. Sediment core samples were taken for multistage carbon dioxide treatment, and the results showed a decrease in carbonate-bound phosphates with depth. Photosynthetic productivity observed during the spring showed a close relationship with the sewage discharges and were also controlled by the tidal current. Based on the determination of dissolved nutrients, it was concluded that the limiting nutrient for photosynthesis was nitrogen rather than phosphorous. The release of some heavy metals from the sewage-polluted intertidal sediment was significant, and beachrock development also related to the discharges. The intertidal fauna was impoverished because of the organic sludge.