Lower Intertidal Zone Research Articles

Biogeographic Patterns in Density, Recruitment, Body Size and Zonation of Rocky Intertidal Predators Suggest Increased Population Vulnerability Near Southern Range Limits

ABSTRACTAimSurveying the demography of populations near species range edges may indicate their vulnerability to range contractions or local extinction as the climate changes. In the rocky intertidal, not only are latitudinal ranges constricted by thermal stress, but tides also create zonation or a ‘vertical range’ driven by sharp environmental gradients. By investigating demographics along the latitudinal and vertical ranges simultaneously, we can investigate whether populations may be vulnerable to a changing climate.LocationRocky intertidal habitats along west coast of the United States.TaxaOchre sea star Pisaster ochraceus, six‐armed sea star Leptasterias spp., emarginate whelks (Nucella ostrina and N. emarginata) and channeled whelk N. canaliculata.MethodsIn 2018, we surveyed the demographics of the taxa above at 33 sites spanning > 11° latitude from central Oregon to southern California, near the southern range limits of each taxon. We counted and sized individuals from the high to low intertidal zone. To understand how environmental stress changed with latitude, we evaluated intertidal temperatures in situ, as well as tidal extremes, tidal amplitude and wave exposure using offshore buoys.ResultsFor all taxa, population density, the relative proportion of smaller individuals (except for emarginate whelks) and the upper vertical limits on the shore declined from north to south as temperatures increased and high tide height, tidal amplitude and wave heights decreased. In addition, smaller individual Leptasterias spp. generally inhabited lower shore levels while smaller individual emarginate whelks inhabited higher shore levels coastwide. For N. canaliculata, smaller animals were higher on shore northward, but lower on shore southward.Main ConclusionsWhile this study is a snapshot in time and cannot assess impacts of climate change, our surveys suggest environmentally‐related demographic limitation toward southern range limits and demographically vulnerable southern populations. Therefore, a warming climate may cause local extinctions or range contractions near southern limits.

Spatial and temporal dynamics of groundwater biogeochemistry in the deep subsurface of a high-energy beach

Intertidal sandy beach systems are considered complex biogeochemical reactors. At beach sites that are subject to high tidal and wave energy, seawater circulation can reach tens of meters deep into the subsurface and changing environmental conditions are assumed to lead to dynamic groundwater flow paths, saltwater-freshwater mixing zones, and a spatio-temporally variable groundwater biogeochemistry. Previous studies mainly focused on the upper meters of subterranean estuaries (STE), while the deep subsurface remained a black box. This study presents spatial (cross-shore) and temporal (~six-weekly, over 1.5 years) dynamics of the groundwater biogeochemistry that were observed down to 24 m below the ground surface (mbgs) of a sandy high-energy beach on Spiekeroog Island (Germany).In addition to redox conditions along a cross-shore transect ranging from oxic to Fe oxide reducing/slightly sulfidic, we found a previously unknown, distinct vertical redox zonation as well. Temporal variations of the biogeochemistry within low salinity groundwater at the most landward station close to the dune base were mainly driven by storm flood related seawater infiltration. Around the high water line, the extent of the upper saline plume (USP) varied over time. Furthermore, temporal dynamics of the O2 saturation at 6 mbgs indicated a seasonally shifting depth of the oxycline at this location. In the lower intertidal zone, groundwater solute concentrations displayed a temporally variable zone of deep freshwater discharge.Regarding the impact of the deep STE on the groundwater biogeochemistry of the discharge zone, our data revealed that nutrient, Mn, and Fe release along the deep flow paths through the USP towards the discharge zone was limited, likely due decreasing availability of labile organic matter and subsequent slowing down of metabolic processes with depth. High concentrations of metabolites in the upper ~2 mbgs of the discharge zone were, therefore, rather attributed to the incorporation of labile organic matter during continuous and storm flood related sediment relocation and/or the contribution of older waters, e.g., the subtidal saltwater wedge.

Fate and partition of perfluoroalkyl acids (PFAAs) driven by particles in mangrove ecosystems: Mechanistic insights and environmental implications

A critical gap in understanding emerging pollutants in mangrove ecosystems should be addressed. Despite their ecological importance, the state of environmental quality in fragmented mangrove patches, especially emerging contaminants, remains largely uncharted. Our research presented an in-depth analysis of the distribution of perfluoroalkyl acids (PFAAs) across porewater, suspended particles, and sediment in these small, fragmented mangroves, revealing the mechanisms behind their distribution. The findings indicated that PFAA concentrations in sediments were generally lower than in suspended particles, except for C12–C14 perfluorinated carboxylic acids (PFCAs) and C4–C6 perfluorinated sulfonic acids (PFSAs). A comparison of contamination levels in different mangrove patches concurred with conventional water quality assessments and crab burrow surveys, showing that large artificially planted patches were less contaminated, while areas with intense human activity were more polluted. Notably, no significant differences were observed in the concentrations of long-chain PFAAs and PFCAs between patches (p > 0.1). Elevated crab burrowing activity and higher concentrations of perfluorobutanoic acid (PFBA) and perfluorohexane sulfonic acid (PFHxS) in suspended particles in low intertidal zones suggested that seafood, particularly crabs and shellfish, might be at risk of PFAA pollution. Rainfall-runoff was identified as the primary source of PFAA pollution in porewater and suspended particle systems in these areas. The transport of PFAAs and organic carbon in mangroves was influenced by the concentrations and properties of suspended particles. These insights were critical for developing targeted environmental management strategies to mitigate the impact of PFAAs and preserve the ecological integrity of mangrove ecosystems.

Non-indigenous species and their realized niche in tidepools along the South-East Pacific coast

Non-indigenous species (NIS) have the potential to colonize and become established in a wide range of coastal habitats. Species with broad environmental tolerances can quickly adapt to local conditions and expand their niches along environmental gradients, and even colonize habitats with extreme abiotic conditions. Here we report and document the distribution of eight marine NIS (four seaweed and four invertebrate species) found in tidepools along a 3000 km latitudinal gradient along the Pacific coast of Chile (18.4°S to 41.9°S). The seaweed NIS Codium fragile, Capreolia implexa, Schottera nicaeensis and Mastocarpus latissimus were mostly distributed towards high latitudes (i.e., more southerly locations), where temperatures in tidepools were low. The invertebrate NIS Anemonia alicemartinae, Ciona robusta, Bugula neritina and Bugulina flabellata were more common towards low latitudes, where high temperatures were registered in the tidepools. Across the intertidal gradient, seaweed NIS were mostly found in pools in the mid and low intertidal zone, while invertebrate NIS occurred mostly in pools from the mid and upper intertidal zones. The realized niche spaces of NIS (based on the Outlying Mean Index, OMI) in the study area were mainly influenced by environmental conditions of temperature and salinity (along the latitudinal and intertidal gradients), while other tidepool characteristics (depth, surface area, exposition, and complexity) only had minor effects. Five of the eight NIS exhibited a realized niche space coinciding with the average tidepool environmental conditions, while marginal niches were occupied by species with affinities for specific temperatures and salinities along the latitudinal and intertidal gradients. Our results indicate that physiological tolerances to environmental factors play a fundamental role in the distribution of seaweed and invertebrate NIS in tidepools along the Chilean coast. This study confirms that tidepools offer suitable conditions for some seaweed and invertebrate NIS, potentially facilitating their invasion into new natural habitats.

Morphodynamics of macrotidal channels in Korean tidal flats: implications for the role of monsoon precipitation and the stratigraphic architecture of tidal point bars

Abstract Tidal channels exert a crucial control on sediment transport and drive geomorphic changes in the tidal environment. Despite their ubiquitous occurrence, long-term morphodynamics and processes driving the morphologic changes remain less well understood than fluvial counterparts. Spanning from straight to dendritic, Korean tidal channels become more sinuous and densely populated with elevation due to higher mud content. Mutually evasive current patterns resulted in a cuspate meander bend, where a flood barb develops at the seaward side of the bend. Multiannual observation revealed that tidal channels migrate from up to 80 m per year in the lower intertidal zone of open-coast sandy tidal flats to nearly stationary for several years in the upper intertidal zone of protected muddy tidal flats. Migration rates are temporarily pronounced during the summer monsoon, when heavy rainfall-induced surface runoff intensifies ebb tidal asymmetry and promotes headward erosion. Meander bends are mostly landward-skewed and shift downstream, implying that ebb currents primarily drive the long-term channel morphodynamics. Tidal point bars commonly display ebbward dipping, inclined heterolithic stratification (IHS) dominated by bedforms formed by subordinate flood tidal currents. An overall ebb dominance and mutually evasive current patterns account for the counterintuitive stratigraphic architecture of point bars in Korean tidal channels.

Biogeographic effects shape soil bacterial communities across intertidal zones on island beaches through regulating soil properties

Island coastal zones are often mistakenly perceived as “ecological desert”. Actually, they harbour unique communities of organisms. The biodiversity on islands is primarily influenced by the effects of area and isolation (distance from the mainland), which mainly focused on plants and animals, encompassing studies of entire islands. However, the application of area and isolation effects to soil microorganisms on island beaches across the intertidal zones remains largely unexplored. We hypothesized that island area and isolation shape soil bacterial communities by regulating soil properties on island beaches, due to the fact that local soil properties might be strongly influenced by land-use, which may vary among islands of different sizes and isolations. To test this hypothesis, we conducted a study on 108 plots spanning 4 intertidal zones on 9 representative island beaches within Zhoushan Archipelago, eastern China. We employed one-way ANOVA and Tukey's honestly significant difference (HSD) test to assess the differences in diversity, composition of soil bacterial communities and soil properties among intertidal zones. Redundancy analysis and structural equation modelling (SEM) were used to examine the direct and indirect impacts of beach area and isolation on soil bacterial communities. Our findings revealed that the area and isolation did not significantly influence soil bacterial diversity and the relative abundance of dominant soil bacterial phyla. However, soil nitrogen (soil N), phosphorus (soil P), organic carbon (SOC), available potassium content (soil AK), and electrical conductivity (soil EC) showed significant increases with the area and isolation. As the tidal gradient increased on beaches, soil bacterial OTU richness, Chao 1, and relative abundance of Planctomycetota and Crenarchaeota decreased, while relative abundance of other soil bacterial phyla increased. We found that influences of island area and isolation shape soil bacterial communities on beaches by regulating soil properties, particularly soil moisture, salinity, and nutrients, all of which are also influenced by area and isolation. Island with larger areas and in lower intertidal zones, characterized by higher soil water content (SWC), soil EC, and soil AK, exhibited greater soil bacterial diversity and fewer dominant soil bacterial phyla. Conversely, in the higher intertidal zones with vegetation containing higher soil N and SOC, lower soil bacterial diversity and more dominant soil bacterial phyla were observed. These findings have the potential to enhance our new understanding of how island biogeography in interpreting island biome patterns.

MACROZOOBENTHOS COMMUNITY STRUCTURE IN THE INTERTIDAL ZONE OF MUARA AIR HAJI VILLAGE PESISIR SELATAN REGENCY WEST SUMATERA PROVINCE

Muara Air Haji Village is a coastal area with various anthropogenic activities that can disrupt the aquatic ecology, especially in the intertidal zone. Biological indicators such as macrozoobenthos are needed to provide a correct and sustainable picture of water quality. This research uses a survey method to determine macrozoobenthos' type, abundance, diversity, uniformity, dominance, and distribution pattern in the intertidal zone. Sampling was carried out using three stations, and each station consisted of three transects and three subzones comprised of the upper, middle, and lower intertidal zones using a quadrant plot measuring 1 x 1 m. The results of this research found three classes of macrozoobenthos with five species. Abundance values ​​at each station ranged from 0.89–4.56 ind/m2, while abundance in the intertidal subzone ranged from 1.11–3.56 ind/m2. The diversity index (H') at stations I and III is 1.93 and 1.17, which means it is included in the medium diversity category, while the diversity index (H') at station II is 0.84, which means it is included in the low category, moderate distribution of individuals or non-uniform number of individuals, moderate ecological pressure and moderately polluted water stability. The uniformity index value ranges from 0.65–0.99, which means the uniformity category is balanced. At station II, macrozoobenton dominates with an index value of 0.62, while stations I and III have no dominant species with index values ​​of 0.30 and 0.45. The distribution pattern (Id) of macrozoobenthos is clustered with a value of 3.45–4.18

Variations in macrofaunal communities along sand physico-chemical gradient across the intertidal zones on island beaches

Island beaches, once mistakenly considered as 'ecological deserts', are actually unique ecosystems that support abundant macrofaunal communities. However, limited studies have examined the variations and determinants of macrofaunal communities across the intertidal zones on island beaches, which is crucial for shedding light on the underlying ecological processes and enhancing biodiversity conservation efforts. Here, we explored the variations in macrofaunal communities along sand physico-chemical gradient across four intertidal zones on nine representative beaches, within the largest land-bridge archipelago in eastern China. Our findings revealed that species richness, density, and Shannon-Wiener diversity of macrofaunal communities were notably higher in the lower intertidal zones, exhibiting a positive correlation with elevated levels of sand moisture (M), electrical conductivity (EC), available potassium (AK), and grain size (GS). Conversely, macrofaunal Simpson diversity displayed an inverse pattern, with heightened values observed in the vegetation zone. The Saprophagous, Predaceous, and Omnivorous groups of macrofaunal communities demonstrated an increase with higher levels of EC, AK, and M in the lower intertidal zones. Furthermore, Phytophagous group of macrofaunal communities tended to inhabit the vegetation zones characterized by elevated levels of sand total phosphorus (TP), total nitrogen (TN), and organic carbon (OC). Primarily, our findings indicate that sand nutrition, moisture, and salinity play pivotal roles in shaping the variations of macrofaunal communities on island beaches. These insights offer valuable perspectives into the holistic responses of macrofauna on island beaches to changes in sand physico-chemical properties, serving as a crucial theoretical foundation for the assessment, conservation, and restoration of island beaches.

The two salinity peaks mode of marine salt supply to coastal underground brine during a single tidal cycle

Seawater salt is constantly supplied from the marine environment to coastal underground brine deposits, meaning that brine has the potential for continuous extraction. There is currently a lack of information about the processes that drive the fluxes of seawater salt to underground brine deposits in tidal-driven brine mining areas. We chose the Yangkou salt field on the southern coast of Laizhou Bay, a brine mining area, as our study site. We monitored the spatial and temporal distribution of the underground brine reserve and the changes in water level and salinity in the mining area and adjacent tidal flats using electrical resistivity tomography and hydrogeological measurements. We monitored cross-sections along two survey lines and observed that the underground brine reserve receives a stable supply of seawater salt, and calculated that the rate of influx into the brine body in the mining area near the boundary of the precipitation funnel was 0.226−0.232 t/h. We calculated that a total salt flux of approximately 5.50 t enters the underground brine body every day through a 150 m long shoreline and a 1322.3 m2 window, which is sufficient to sustain the daily extraction of one brine well. During tidal cycles, there are two peaks in the salinity of the water supplied to the underground brine reserve, which means that the brine supply is from at least two high-salinity salt sources in different tidal stages. The first salinity peak occurs during the initial stage of the rising tide after seawater inundates the tidal flat. At this time, seawater, which is a solution and carries a large amount of evaporated salt, is transported into the brine layer through highly permeable areas or biological channels and replenishes the brine in the mining area. The second salinity peak occurs during the early stage of the falling tide. Influenced by hysteresis-driven tidal pumping, high-salinity brine from the lower intertidal zone is rapidly transported into the mining area, thereby increasing the salinity of the underground brine.

Changes in the leaf functional traits of mangrove plant assemblages along an intertidal gradient in typical mangrove wetlands in Hainan, China

The understanding of biodiversity-ecosystem functioning linkages under environment change has been advanced immensely by the development and application of the functional trait theory. Intertidal zones, characterized by significant environmental gradient differences, are severely threatened by sea-level rises caused by global warming. The functional trait distribution pattern for mangrove communities along the intertidal gradient and underlying mechanisms remain unclear. We investigated differences in the leaf functional traits of mangrove plant assemblages among the high, middle, and low intertidal zones, and their relationships to sediment physicochemical properties, in Dongzhaigang and Qinglan Harbor reserves, Hainan, China. In both reserves, most sediment physicochemical properties (pH; salinity; total potassium, carbon, nitrogen, and sulfur concentrations; organic carbon content; ammonium nitrogen and available phosphorus concentrations) differed significantly among gradient zones. The sediment pH, total phosphorus, and available potassium concentrations differed significantly between the dry and wet seasons. From the low to the high intertidal zone, the mangrove specific leaf area and leaf nitrogen and phosphorus concentrations increased significantly and the leaf thickness decreased significantly. The leaf tannin and lignin concentrations were significantly lower and the leaf phosphorus concentration, nitrogen concentration and hardness were significantly higher in the dry season than in the wet season. The sediment salinity, pH, and total sulfur and potassium contents were key factors affecting the distribution of mangrove leaf functional traits along the intertidal gradient. The changes in mangrove leaf functional traits reflect gradient-level responses to environmental stress and the sediment nutrient status. Our findings improve the understanding of the functional trait diversity and maintenance mechanisms of mangrove communities under environmental change and provide a new perspective for the prediction of how coastal mangroves will respond to future global warming.

Aerial exposure tolerance of juvenile flat oysters (Ostrea angasi) depends on shell length and air temperature

Oyster reefs have declined globally, impacting ecosystem structure, function, and services. The flat oyster Ostrea angasi was a dominant ecosystem engineer throughout southern Australia, forming extensive reefs now diminished to <1% of historical coverage. Restoration of O. angasi has gained traction over the last decade, exclusively in subtidal habitats. However, O. angasi historically occurred in the intertidal zone, which could broaden restoration opportunities and success. There is little information quantifying factors that influence the performance of O. angasi in intertidal habitats. To test survival of O. angasi under thermal and desiccation stress experienced in intertidal habitats under winter, summer, and heatwave conditions, we emersed individuals from three age classes (1, 4, and 7 months old) at air temperatures of 10, 25, or 40°C in a series of laboratory experiments. Oysters exhibited moderate tolerance to exposure, with survival depending on interactions between emersion duration and temperature, and emersion duration and shell length. Survival broadly increased with shell length, but decreased with temperature and emersion duration. We used model predictions from the laboratory experiments to simulate intertidal survival rates at a potential restoration site in southern Australia. The simulation revealed low survival when low tides coincided with heatwaves. Field validation is needed to understand the effects of repeated tidal cycles and other biotic and abiotic influences. Our findings provide preliminary evidence for extending the restoration range of O. angasi into the low intertidal zone and can be considered when mitigating transport‐related mortality during large‐scale restoration.

Investigating the impact of introduced crabs on the distribution and morphology of littorinid snails: Implications for the survival of the snail Littorina saxatilis

Introduced species can have profound impacts on communities by displacing and consuming native organisms. The intertidal communities in the Gulf of Maine have been radically altered through a suite of invasions in the early 1800s, including the herbivorous snail Littorina littorea and the omnivorous European green crab Carcinus maenas leading to morphological and distributional changes in two native gastropod grazers (Littorina saxatilis and Littorina obtusata). Green crabs and native cancrid crabs occupy the mid to low intertidal zones, leaving the high intertidal zones relatively free from crab predation pressure. However, a more recent invasion in the 1980s by the intertidal omnivorous Asian shore crab Hemigrapsus sanguineus, has eliminated this predator-free zone in the high intertidal. This invasion is of particular concern to populations of L. saxatilis, which were relegated to the high intertidal through combined competition and predation pressure by L. littorea and C. maenas. In order to quantify the potential impact of H. sanguineus on native snails, we conducted both field and lab experiments, testing the susceptibility of different sized snails to predation by introduced crabs. Additionally, we measured the distribution, abundance, and morphology of intertidal snails and crabs. Smaller snails of all species were the most susceptible to predation, although susceptibility differed among snail species and predation capabilities differed among crab species. L. saxatilis was the most vulnerable snail species to predation, with 73 and 64% of the population susceptible to large H. sanguineus and small C. maenas, respectively, while >96% of the L. littorea population was resistant to predation. L. saxatilis has been relegated to the high intertidal where there is high abiotic stress and poor-quality food, but until the invasion of H. sanguineus, there was little predation risk. This added predation pressure may further threaten populations of L. saxatilis, especially as the upper intertidal becomes more hostile with increasing temperatures and possible species introductions.

Roles of Exposure Time and Geochemical Factors in the Characteristics of the Surface Sediments of the Hwangdo Tidal Flat, Taean, Cheonsu Bay, West Coast of Korea

The Hwangdo tidal flat is an intertidal landform located in Cheonsu Bay, Taean-gun, Chungcheongnam-do, on the west coast of Korea. The topographical characteristics of the semi-enclosed bay on the eastern side of the study area include waterways, sandbars, small islands, and tidal flats. In this study, data were acquired from tide gauges installed on the Hwangdo Bridge, and the height of the ellipsoid was measured using a real-time kinematics global positioning system (RTK-GPS). Digital elevation model (DEM) using Matrice 300 drone data were also acquired after processing. The geochemical sediment characteristics in the study area were analyzed, together with tidal-flat exposure-time characteristics based on environmental factors. Sediment data (n = 107) collected from October 25 to 28, 2022 (Korean local time) were used to classify sediment particles according to Folk and Ward (1957). Sedimentary facies ranged from coarse sand (sand:mud ratio = 9:1) to sandy silt (sZ) followed by muddy sand (mS) and slightly gravelly sandy mud ((g)sM). Total organic carbon (TOC) in the surface sediments was also characterized based on a particle-size analysis. The mean change in tidal height measured at Hwangdo Bridge during the sampling period was ~7.53 m (minimum: −3.86 m, maximum: +3.67 m). Based on the Boryeong’s sea level measurement tide data in 2022, the tidal area in the drone images ranged from 6.362 m2 (0.006 km2) at DEM +4.0 to 4,841,078 m2 (4.841 km2) at DEM −4.0 m, indicating an increase in the tidal-flat area according to the tidal level of up to ~800-fold. The daily average exposure time was 9.0 h (minimum: 1.5 h, maximum: 17.9 h). Based on the results of multivariate analysis using exposure times and a geochemical dataset, four groups were identified: upper, middle, and lower intertidal zones and regions with a relatively high organic-matter concentration. A determination of the main characteristics of the Hwangdo tidal flat according to their spatial distribution showed that, among various environmental factors, changes in the sand or clay sediment composition were determined by community factors. The results of this study demonstrate the four statistically processed groups of marine environmental characteristics in the Hwangdo tidal flats. Changes in sedimentary patterns, rather than in the exposure time, accounted for the differences in the sediment compositions of the upper, middle, and lower stations, a response that is expected to continue.

Long-term community shifts driven by local extinction of an iconic foundation species following an extreme marine heatwave.

Gradual ocean warming combined with stronger marine heatwaves (MHWs) can reduce abundances of foundation species that control community structures, biodiversity, and ecosystem functioning. However, few studies have documented long-term succession trajectories following the more extreme events that cause localized extinctions of foundation species. Here, we documented long-term successional changes to marine benthic communities in Pile Bay, New Zealand, following the Tasman 2017/18 MHW, which caused localized extinctions of dominant southern bull kelp (Durvillaea sp.). Six years on, multiscale annual and seasonal surveys show no sign of Durvillaea recolonization. Instead, the invasive annual kelp (Undaria pinnatifida), rapidly colonized areas previously dominated by Durvillaea, followed by large changes to the understory community, as Durvillaea holdfasts and encrusting coralline algae were replaced by coralline turf. Between 3 and 6 years after the total loss of Durvillaea, smaller native fucoids colonized in high densities. Although Undaria initially colonized plots throughout Durvillaea's tidal range, later in the succession Undaria only retained dominance in the lower intertidal zone and only in spring. Ultimately, the tidal zone was slowly replaced by alternative foundation species, composed of different canopy-forming brown seaweeds that dominated different intertidal elevations, resulting in a net increase in canopy and understory diversity. This study is a rare example of long-term effects following an extreme MHW that caused extinctions of a locally dominant canopy-former, but these events and their associated dramatic changes to community structures and biodiversity are expected to become increasingly common as MHWs continue to increase in strength, frequency, and duration.

Influence of the invasive bivalve Isognomon bicolor on the native community found in northeast Brazilian coast

The Caribbean bivalve Isognomon bicolor (C. B. Adams, 1845) is currently among the main invasive species along the Brazilian coast. The present study evaluated the co-occurrence, influence, and relationship of the native macrobenthic community with I. bicolor. The study was performed on samples collected from two sandstone reefs located in Northeast Brazil. We observed that the macrobenthic community differed significantly across reefs, zones, and seasons. The higher density of I. bicolor in the lower intertidal zone (347.7 ind/m² ± 800.8) was one of the main differentiation factors of zonation. The results indicated that the evenness of the community and some gastropods had a negative effect on I. bicolor. We found a negative correlation between the co-occurrence of I. bicolor with the macroalgae Hypnea sp. and Gracilaria caudata J. Agardh 1852 and the microgastropod Eulithidium affine (C. B. Adams, 1850). This study provides data on the relationship between I. bicolor and the native community of sandstone reefs, which could be applied to monitor the expansion of I. bicolor to the Northeast region of Brazil.

KEPADATAN, KARAKTER MORFOLOGI, DAN PERTUMBUHAN LAMUN Cymodocea rotundata DI PANTAI YANKARWAR, MANOKWARI, PAPUA BARAT: APAKAH ADA PERBEDAAN DIANTARA ZONA INTERTIDAL?

Cymodocea rotundata is a seagrass species that occupy habitats in the intertidal zone. The ability of this species to occupy the intertidal zone is thought to be related to its particular morphological adaptations in response to fluctuations in local aquatic environmental conditions. This study aims to describe habitat conditions, distribution related to density, morphological differences, and growth among C. rotundata seagrass stands in the upper, middle, and lower intertidal zones of Yankarwar Beach, Manokwari, West Papua. Transects and quadrats methods were used to collect seagrass samples, so information on their distribution and density could be obtained. The seagrass samples collected were also analyzed (counted and measured) for their morphological characters including the number of leaves, leaf length, leaf width, horizontal sheath internode length, root length, stand weight, leaf weight, rhizome weight, and root weight. Seagrass growth was obtained by marking the leaves and observing them for 10 days. The results of this study indicate that the conditions of the physicochemical parameters of the intertidal waters are still suitable for the growth of this seagrass species. The highest density was found in the upper intertidal zone (3,161.73 stands.m-2) and followed by the middle intertidal zone (962.04 stands.m-2). Although most of the morphological characters of seagrasses and seagrass parts were relatively the same between the three intertidal zones, larger leaf widths and lengths of horizontal rhizome internodes were found in stands in the two upper intertidal zones. Differences in growth as reflected by the increase in leaf length and dry leaf weight also showed greater values in the upper and middle intertidal zones. This condition shows the adaptability of this seagrass species to variations in environmental parameter conditions in the middle and upper intertidal zone. In addition, the results of this study indicate the presence of C. rotundata, especially in the intertidal aquatic environment which has an important ecological role, including as a substrate stabilizer. Therefore, this vegetation conservation effort is very important.
 
 Keywords: intertidal zone, morphological adaptation, seagrass growth

Population structure and dynamics of Petrolisthes armatus (Gibbes, 1850) (Anomura: Porcellanidae) in an Amazon estuary

The aim of this study was to assess the environmental factors that modulate the spatiotemporal distribution of Petrolisthes armatus and analyze their population structure, dynamics and secondary production in an Amazon estuary. Monthly samplings were carried out over one year in the intertidal rocky outcrop considering the following environmental features; season (dry and rainy), areas (middle and lower estuary), banks (east and west), substrate with different rock sizes, and the upper and lower intertidal zones. Crab density was positively correlated with salinity and negatively correlated with temperature. Higher densities occurred during dry season, on the eastern bank, in the lower estuary, in the lower intertidal zone, and in the larger rock substrate. The high abundance of P. armatus indicates that this estuary is a suitable habitat for the development of this anomuran, and salinity and substrate were the most important factors driving population structure. High production reflects high density and biomass and the fast growth of this crab indicated that this filter feeder generates substantial production to the benthos. This study corroborated the hypothesis that the high metabolism of P. armatus combined with the high temperature in the Amazon region results in short life span (∼one year), high mortality rate (∼6 year −1), and high P/B ratio (∼4 year −1).

Dolomite porosity related to peritidal microbialites textures and facies succession in Mesoproterozoic Wumishan Formation, North China

There are three main types of microbial dolostones in Mesoproterozoic Wumishan Formation in Jixian, North China. They are stromatolite, thrombolite and granular microbialite. The microbialite lithofacies are intensely environmentally associated. Several kinds of stromatolite can be found in the peritidal environments. Mostly planar or wavy stromatolites show in intertidal and supratidal zones while domy and conic stromatolites occur in subtidal or lower intertidal zones. In more agitated subtidal zone or tidal channels, microbial grains deposited, such as thrombolite, oncolite, and sand- gravel sized microbial-coated grains. The intraclasts related laminite facies mostly deposited in shallow subtidal zone.Representative four outcrop sections of Wumishan Formation in Jixian are measured and documented. The petrophysical and petrological study from the outcrop and well core samples reveals that the reservoir rocks are closely related to lithofacies and their depositional environments. The more agitated the depositional environment is, the better the reservoir quality, even so that after the diagenesis (surface and burial). The dolostone porosity of planar stromatolite in supratidal and intertidal are much worse than the subtidal high-agitated microbialite rocks, whether samples from the outcrops or drilling cores.The effective reservoir interval is normally located in the lower part of a peritidal microbial facies succession, mainly consists of subtidal microbialite, such as thrombolite, thrombo-stromatolite, oncolite, columnar stromatolite and coated intraclastic grainstone and rudstone, commonly deposited in agitated environment. The thickness of reservoir rocks in microbialite para-sequences ranges commonly from 4 to 14 m, deeply related to depositional cycles or sequence stratigraphy in vertical lithofacies texture and their areal extent to the paleogeography.

Predator effects on behavior and anaerobic capacity in the common acorn barnacle (Balanus glandula)

ABSTRACT Differences in the stress experience of sessile organisms across the intertidal zone can differentially influence phenotype. For example, Balanus glandula barnacles from the low intertidal zone have higher lactate levels, greater lactate dehydrogenase (LDH) activity and reduced cirral activity compared to conspecifics from the high intertidal zone. We tested the hypothesis that enhanced anaerobic capacity in lower intertidal B. glandula results from increased predation and hypoxia-inducing shell closure. To investigate this hypothesis, we compared the density of whelk predators across the intertidal zone, and quantified the behavioral response and LDH activity levels of B. glandula exposed to predators in the lab. We consistently found more predators in the low intertidal zone, although the response of B. glandula to predators was short-term operculum closure (<1hr) which did not result in significant differences in LDH activity. Thus, increased predation is not the cause of high anaerobic capacity in lower intertidal B. glandula.

New evidence for coiling direction of benthic foraminifera as a temperature proxy

Foraminifera are sensitive to climate change and their species composition, shell chemical element composition and morphological characteristics are useful paleoenvironmental proxies. Coiling direction is a distinctive and easily identifiable morphological feature in trochospiral foraminifera and has been used for paleoceanographic reconstruction. Here, we conducted a field survey in a low intertidal zone in Yellow Sea for 13 months and performed a culture experiment under three temperatures and four salinities for the benthic foraminifera to seek the relationship between coiling direction and environmental factors. Our results showed that the dominant benthic foraminifera Ammonia aomoriensis (Asano, 1951) preferred sinistral direction under high temperature and had no preference with salinity. Statistical analysis showed that the ratio of sinistral/dextral in A. aomoriensis was significantly positively correlated with temperature (r = 0.5017, p = 0.0011 for field survey and r = 0.5117, p = 0.0014 for culture experiment), but had no evident relationship with salinity (p &amp;gt; 0.05). The ratio of sinistral/dextral was significantly negatively related with the abundance of A. aomoriensis (p &amp;lt; 0.05) and the ratio of sinistral/dextral was significantly positively related with the size (p &amp;lt; 0.05). This was the first study on the coiling direction of benthic foraminifera combining the field survey and culture experiment. Our findings suggested that the ratio of sinistral/dextral in A. aomoriensis could be used to indicate the change of temperature. This study offered new evidence for the reliability of the coiling direction as a temperature proxy and made us rethink the significance of the morphological change in biological adaptation and evolution.