Changes in limpet diet according to habitat type.

Limpets are a key taxon regulating the benthic community structure and serving as prey for various predators in rocky shores, however, their role in food web dynamics is still unclear. To determine environmental factors influencing the limpet diet, carbon and nitrogen stable isotopes in limpets and food sources were analyzed on three different coastal habitats. Sediment organic matter contributed the most (86 %) to the limpet diet in bedrocks around tidal flats with abundant sediment supply from the terrestrial matter inflow and the sediment resuspension. Microphytobenthos and macroalgae were the main food sources (57 % and 20 %, respectively) for the limpets around beaches, where benthic flora was abundant. Limpets in bedrocks, erosional habitat, primarily consumed relatively abundant phytoplankton (33 %) and microphytobenthos (28 %). Contrary to previous studies, habitat type, rather than latitude or seawater characteristics, was the most important factor determining the limpet diet. This result also suggests that limpets are non-selective scraper that consume abundant food sources.

Cost-efficient PCR based DNA barcoding of marine invertebrate specimens with NovaSeq amplicon sequencing.

BACKGROUND: The marine environment harbors high biodiversity; however, it is poorly understood. Nucleotide sequence data of all marine organisms should be accumulated before natural and/or anthropogenic environmental changes jeopardize the marine environment. In this study, we report a cost-effective and easy DNA barcoding method. This method can be readily adopted without using library preparation kits. It includes multiplex PCR of short targets, indexing PCR, and outsourcing to a sequencing service using the NovaSeq system. METHODS AND RESULTS: We targeted four mitochondrial genes [cytochrome c oxidase subunit I (COI), COIII, 16S rRNA (16S), and 12S rRNA (12S)] and three nuclear genes [18S rRNA (18S), 28S rRNA (28S), internal transcribed spacer 2 (ITS2)] in 95 marine invertebrate specimens, which were primarily annelids. The primers, including adapters and indices for NovaSeq sequencing, were newly designed. Two PCR runs were conducted. The 1st PCR amplified specific loci with universal primers and the 2nd added sequencing adapters and indices to the 1st PCR products. The gene sequences obtained from the FASTQ files were subjected to BLAST search and phylogenetic analyses. One run using 95 specimens yielded sequences averaging 2816 bp per specimen for a total length of six loci. Nuclear genes were more successfully assembled compared with mitochondrial genes. A weak but significantly negative correlation was observed between the average length of each locus and success rate of the assembly. Some of the sequences were almost identical to the sequences obtained from specimens collected far from Japan, indicating the presence of potentially invasive species identified for the first time. CONCLUSIONS: We obtained gene sequences efficiently using next-generation sequencing rather than Sanger sequencing. Although this method requires further optimization to increase the success rate for some loci, it is used as a first step to select specimens for further analyses by determining the specific loci of the targets.

Effects of cable bacteria on vertical redox profile formation and phenanthrene biodegradation in intertidal sediment responded to tide.

Periodic oxygen permeation is critical for pollutant removal within intertidal sediments. However, tidal effects on the vertical redox profile associated with cable bacterial activity is not well understood. In this study, we simulated and quantified the effects of tidal flooding, exposing, and their periodic alternation on vertical redox reactions and phenanthrene removal driven by cable bacteria in the riverbank sediment. Results show that electrogenic sulfur oxidation (e-SOx) mediated by cable bacteria during exposing process drove the vertical permeation of oxidation potential characterized by a decrease in Fe(II) and sulfide concentrations. The sulfate produced was observed in deep sediment (5-10 mm) and served as an electron acceptor for anaerobic oxidation, thereby triggering the functional succession of microbial community. About 78.2 % and 80.8 % of phenanthrene was degraded in deep sediment where cable bacteria grew well under exposing and tidal conditions. Anaerobic processes during tidal flood were also found to be important for the survival of cable bacteria. Higher cable bacteria abundance (up to 1.5 %) was observed under tidal conditions compared to that under continuous exposing conditions and flooding conditions. This might be attributed to lower oxidation stress and sulfide replenishment via sulfate reduction while flooding. Under tidal conditions, the cable bacteria interacted with sulfate reduction bacteria (e.g. Desulfobacca spp. and Desulfatiglans spp.) and maintained the dynamic balance of HS- and SO42- in sediment profiles. This HS--SO42- cycle could serve as a "redox connector" that continuously delivers oxidation potential to deep sediments, resulting in the removal of organic pollutants. The findings provide preliminary evidence of the self-purification mechanisms within intertidal sediments and suggest a potential strategy for sediment remediation.

Baseline for the Northeast Atlantic (58-70°N) intertidal Mytilus species complex (Mytilus spp.).

Mussels (Mytilus spp.) are abundant in the North Atlantic, sessile, and sensitive to environmental change, and suitable as sentinels of environment and climate change of costal ecosystems. We aimed to determine the baseline for the Northeast Atlantic (58-70°N) Mytilus species complex, and to show the present distribution to surveys conducted 60 years ago. Baseline was obtained by investigating a total of 509 stations in the intertidal zone, in four regions comprising the environmental gradient from head of fjord to coast, and distributed over the latitudinal gradient from 58 to 70°N. The baseline shows a range in continuous abundance of mussels from 12% to 36%, patchy abundance from 26% to 57% and no or very limited mussel abundance from 26% to 46% between the four regions. The presence of mussels in the southeast and west region was visualized to previous surveys conducted 60 years ago. The data points to similar past and present presence of mussels in both regions, yet past major mussel fields in the inner section of region southeast was not detected in this study. The baseline of Mytilus spp. in the Northeast Atlantic (58-70°N) is now available for future reference. The baseline, plotted to surveys conducted 60 years ago, points to awareness of the population situated in the southeast section of the investigated region. Continued monitoring and modeling are needed to clarify drivers of temporal and spatial variation in the mussel populations along the Northeastern Atlantic coast.

Epibiont communities on mussels in relation to parasitism and location in the rocky intertidal zone.

The factors shaping host-parasite interactions and epibiont communities in the variable rocky intertidal zone are poorly understood. California mussels, Mytilus californianus, are colonized by endolithic cyanobacterial parasites which erode the host shell. These cyanobacteria become mutualistic under certain abiotic conditions because shell erosion can protect mussels from thermal stress. How parasitic shell erosion affects or is affected by epibiotic microbial communities on mussel shells and the context dependency of these interactions is unknown. We used transplant experiments to characterize assemblages of epibiotic bacteria and endolithic parasites on mussel shells across intertidal elevation gradients. We hypothesized that living mussels, and associated epibacterial communities, could limit colonization and erosion by endolithic cyanobacteria compared to empty mussel shells. We hypothesized that shell erosion would be associated with compositional shifts in the epibacterial community and tidal elevation. We found that living mussels experienced less shell erosion than empty shells, demonstrating potential biotic regulation of endolithic parasites. Increased shell erosion was not associated with a distinct epibacterial community and was decoupled from the relative abundance of putatively endolithic taxa. Our findings suggest that epibacterial community structure is not directly impacted by the dynamic symbiosis between endolithic cyanobacteria and mussels throughout the rocky intertidal zone.

Intertidal assemblages on groynes along sandy shores in Portugal: Exploring the effects of orientation and distance to rocky shore.

Coastal erosion is becoming increasingly problematic as sea level rise and coastal areas become more urbanised. In response, more defence structures such as groynes are being built, which are crucial for counteracting sediment loss and coastline retreat. Despite worldwide use, comparatively little is known about the factors that determine the species composition on such structures. In this study, the composition and abundance of intertidal benthic species on groynes was investigated as a function of groyne orientation (North vs. South) and distance to natural rocky shores (5 km vs. 42 km). While orientation showed no effect on benthic assemblages, distance to rocky shores was identified as a key factor influencing the assemblage composition. Macroalgae were found in greater abundance further away from rocky shores, while snail and barnacle species were found in greater numbers closer to rocky shores.

Interactive effects of temperature and salinity on metabolism and activity of the copepod Tigriopus californicus.

In natural environments two or more abiotic parameters often vary simultaneously, and interactions between covarying parameters frequently result in unpredictable, non-additive biological responses. To better understand the mechanisms and consequences of interactions between multiple stressors it is important to study their effects on not only fitness (survival and reproduction) but also performance and intermediary physiological processes. The splashpool copepod Tigriopus californicus tolerates extremely variable abiotic conditions and exhibits a non-additive, antagonistic interaction resulting in higher survival when simultaneously exposed to high salinity and acute heat stress. Here, we investigated T. californicus' response in activity and oxygen consumption under simultaneous manipulation of salinity and temperature to identify if this interaction also arises in these sublethal measures of performance. Oxygen consumption and activity rates decreased with increasing assay salinity. Oxygen consumption also sharply increased in response to acute transfer to lower salinities, an effect that was absent upon transfer to higher salinities. Elevated temperature led to reduced rates of activity overall, resulting in no discernible impact of increased temperature on routine metabolic rates. This suggests that swimming activity has a non-negligible effect on copepod's metabolic rates and must be accounted for in metabolic studies. Temperature also interacted with assay salinity to affect activity and with acclimation salinity to affect routine metabolic rates upon acute salinity transfer, implying that the sublethal impacts of these co-varying factors are also not predictable from experiments that study them in isolation.

Discovery of Candidatus Nitrosomaritimum as a New Genus of Ammonia-Oxidizing Archaea Widespread in Anoxic Saltmarsh Intertidal Aquifers.

Ammonia-oxidizing archaea (AOA) are widely distributed in marine and terrestrial habitats, contributing significantly to global nitrogen and carbon cycles. However, their genomic diversity, ecological niches, and metabolic potentials in the anoxic intertidal aquifers remain poorly understood. Here, we discovered and named a novel AOA genus, Candidatus Nitrosomaritimum, from the intertidal aquifers of Yancheng Wetland, showing close metagenomic abundance to the previously acknowledged dominant Nitrosopumilus AOA. Further construction of ammonia monooxygenase-based phylogeny demonstrated the widespread distribution of Nitrosomaritimum AOA in global estuarine-coastal niches and marine sediment. Niche differentiation among sublineages of this new genus in anoxic intertidal aquifers is driven by salinity and dissolved oxygen gradients. Comparative genomics revealed that Candidatus Nitrosomaritimum has the genetic capacity to utilize urea and possesses high-affinity phosphate transporter systems (phnCDE) for surviving phosphorus-limited conditions. Additionally, it contains putative nosZ genes encoding nitrous-oxide (N2O) reductase for reducing N2O to nitrogen gas. Furthermore, we gained first genomic insights into the archaeal phylum Hydrothermarchaeota populations residing in intertidal aquifers and revealed their potential hydroxylamine-detoxification mutualism with AOA through utilizing the AOA-released extracellular hydroxylamine using hydroxylamine oxidoreductase. Together, this study unravels the overlooked role of priorly unknown but abundant AOA lineages of the newly discovered genus Candidatus Nitrosomaritimum in biological nitrogen transformation and their potential for nitrogen pollution mitigation in coastal environments.

Impact of water level management on organic carbon availability and nitrogen transformations in wetland sediments.

The impact of water level management via water retention on benthic carbon and nitrogen fluxes was studied in a wetland of the Seine estuary. Carbon and inorganic nitrogen fluxes at the sediment-water interface were determined during periods of intermittent and permanent immersion along a lateral gradient. In addition to fluxes, nitrate reduction rates, quantity and quality of both sedimentary and dissolved organic carbon, and organic matter lability via external enzymatic activities were analyzed. During both periods, the sediments subject to water level management facilitated nitrogen removal, with potential NO3- fluxes averaging -109 ± 31 nmol NO3- cm-2 h-1 under permanent immersion and -34 ± 13 nmol NO3- cm-2 h-1 under intermittent immersion. During permanent immersion, more water retention favors a higher input of dissolved organic matter including fresh and labile compounds, which most likely explained the significantly higher NO3- influxes. Intermittent immersion resulted in a lower quantity of retained dissolved organic matter, which likely explains the low N fluxes. The results of this study indicate the implementation of water retention strategies can markedly enhance NO3- removal by increasing the availability of organic matter. This underscores the importance of considering water-level management of wetlands to sustain the ecological functions of these valuable ecosystems, which are often the first barriers against environmental disturbance.

Resource utilisation and trophic niche overlap of coralline intertidal benthic amphipods: an isotopic perspective.

Benthic amphipod feeding groups are a well-established trophic classification that is mostly based on field observations and laboratory tests and are used in ecological studies to monitor the ecological state of benthic ecosystems. Globally, carbon and nitrogen stable isotope ratio investigations have provided confirmation of, and novel insights into, the trophic ecology of benthic animals, such as polychaetes. However, stable isotopic examinations of benthic amphipods have been limited. Here, we used microgram samples to compare the species-specific dietary sources, trophic positions, and isotopic niche overlap of selected benthic amphipods from the Gulf of Kachchh, Marine National Park, using elemental analyser-isotopic ratio mass spectrometry (EA-IRMS) of carbon and nitrogen. Overall, all primary carbon sources presented wide variation in the isotopic values of δ13C (6.3‰) and δ15N (greater than 13‰). Conversely, the amphipod taxa displayed relatively narrow range for δ13C (3.9‰) and wider range for δ15N (more than 10‰). The results of the Bayesian mixing model revealed that the benthic amphipods had species-specific feeding preferences. However, the predominant carbon source was organic matter in sediment which reinforced benthic pathways for energy flow for most species. According to the estimated trophic level values (1.62-3.39), these species play a significant role as primary and secondary consumers serving as crucial trophic intermediaries in the food chain, connecting the base to the top consumers. High overlapping ecological niche amongst species was detected by SIBER analysis which indicated co-existence of the benthic amphipods in their respective microhabitats. This signifies wider utilisation of resources and inter-specific feeding preferences with minimal competition amongst amphipod species.

Warming sea surface temperatures are linked to lower shorebird migratory fuel loads.

Warming sea surface temperatures (SSTs) are altering the biological structure of intertidal wetlands at a global scale, with potentially serious physiological and demographic consequences for migratory shorebird populations that depend on intertidal sites. The effects of mediating factors, such as age-related foraging skill, in shaping the consequences of warming SSTs on shorebird populations, however, remain largely unknown. Using morphological measurements of Dunlin fuelling for a >3000 km transoceanic migration, we assessed the influence of climatic conditions and age on individuals' migratory fuel loads and performance. We found that juveniles were often at risk of exhausting their fuel loads en route to primary wintering grounds, especially following high June SSTs in the previous year; the lagged nature of which suggests SSTs acted on juvenile loads by altering the availability of critical prey. Up to 45% fewer juveniles may have reached wintering grounds via a non-stop flight under recent high SSTs compared to the long-term trend. Adults, by contrast, were highly capable of reaching wintering grounds in non-stop flight across years. Our findings suggest that juveniles were disproportionately impacted by apparent SST-related declines in critical prey, and illustrate a general mechanism by which climate change may shape migratory shorebird populations worldwide.

Thalassospira aquimaris sp. nov. and Winogradskyella marincola sp. nov. two marine bacteria isolated from an agar-degrading co-culture.

Two novel Gram-stain-negative, aerobic, and non-motile strains, designated FZY0004T and YYF002T, were isolated from an agar-degrading co-culture, which was obtained from seawater of the intertidal zone of Yancheng City, the Yellow Sea of China. Strain FZY0004T optimally grew at 28 °C, pH 7.0, and 2-6% NaCl, while strain YYF002T optimally grew at 28 °C, pH 7.5, and 2-4% NaCl. Strain FZY0004T possessed Q-9 as the major respiratory quinone, and its major fatty acids (> 10%) were summed feature 8 (C18:1 ω7c), C16:0, and summed feature 3 (C16:1 ω7c/C16:1 ω6c). The polar lipids identified in strain FZY0004T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and several unidentified phospholipids (PL) and lipids (L). On the other hand, strain YYF002T had MK-6 as the predominant respiratory quinone and its major fatty acids consisted of iso-C15:0, iso-C15:1 G, and iso-C15:0 3-OH. The polar lipids identified in strain YYF002T were aminolipid (AL), PE, and several unidentified lipids. Strain FZY0004T shared 99.5% 16S rRNA gene sequence similarity and 90.1% average nucleotide identity (ANI) with T. povalilytica Zumi 95T, and strain YYF002T shared 99.2% 16S rRNA gene sequence similarity and 88.2% ANI with W. poriferorum JCM 12885T. The genomic DNA G + C contents of strains FZY0004T and YYF002T were 54.5% and 33.5%, respectively. The phylogenetic, phenotypic, and physiological characteristics permitted the distinction of the two strains from their neighbors, and we thus propose the names Thalassospira aquimaris sp. nov. (type strain FZY0004T = JCM 35895T = MCCC 1K08380T) and Winogradskyella marincola sp. nov. (type strain YYF002T = JCM 35950T = MCCC 1K08382T).

Changes in the composition of invertebrate assemblages from wave-exposed intertidal mussel stands along the Nova Scotia coast, Canada.

Rocky intertidal habitats occur worldwide and are mainly characterized by primary space holders such as seaweeds and sessile invertebrates. Some of these organisms are foundation species, as they can form structurally complex stands that host many small invertebrates. The abundance of primary space holders is known to vary along coastlines driven directly or indirectly by environmental variation. However, it is less clear if the invertebrate assemblages associated to a foundation species may remain relatively unchanged along coastlines, as similar stands of a foundation species can generate similar microclimates. We examined this question using abundance data for invertebrate species found in mussel stands of a similar structure in wave-exposed rocky habitats at mid-intertidal elevations along the Atlantic coast of Nova Scotia (Canada). While the most abundant invertebrate species were found at three locations spanning 315 km of coastline, species composition (a combined measure of species identity and their relative abundance) differed significantly among the locations. One of the species explaining the highest amount of variation among locations (a barnacle) exhibited potential signs of bottom-up regulation involving pelagic food supply, suggesting benthic-pelagic coupling. The abundance of the species that explained the highest amount of variation (an oligochaete) was positively related to the abundance of their predators (mites), further suggesting bottom-up forcing in these communities. Overall, we conclude that species assemblages associated to structurally similar stands of a foundation species can show clear changes in species composition at a regional scale.

Elongatibacter sediminis gen. nov., sp. nov., isolated from intertidal sediment, and genomic comparison with all genera in the family Wenzhouxiangellaceae.

A novel slightly halophilic, aerobic, and Gram-stain-negative strain, designated as CH-27T, was isolated during a bacterial resource investigation of intertidal sediment collected from Xiaoshi Island in Weihai, PR China. Cells of strain CH-27T were rod-shaped with widths of 0.3-0.6 µm and lengths of 2.0-11.0 µm. Strain CH-27T grew optimally at 37 °C, pH 7.0 and with 2.0 % (w/v) NaCl. Catalase activity was weakly positive and oxidase activity was positive. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain CH-27T was most related to Marinihelvus fidelis KCTC 92639T (93.6 %), followed by Wenzhouxiangella marina MCCC 1K00261T (92.0 %). Based on genome comparisons between strain CH-27T and M. fidelis KCTC 92639T, the average amino acid identity was 63.6 % and the percentage of conserved proteins was 48.3 %. The major cellular fatty acid of strain CH-27T (≥10 %) was iso-C15 : 0 and the sole respiratory quinone was quinone-8. The polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, and aminophospholipid. The DNA G+C content was 62.7 mol%. Based on comprehensive analysis of its phylogenetic, physiological, biochemical, and chemotaxonomic characteristics, strain CH-27T represents a novel species in a novel genus, for which the name Elongatibacter sediminis gen. nov., sp.nov. is proposed. The type strain is CH-27T (=MCCC 1H00480T=KCTC 8011T).

Ice in the intertidal: patterns and processes of freeze tolerance in intertidal invertebrates.

Many intertidal invertebrates are freeze tolerant, meaning that they can survive ice formation within their body cavity. Freeze tolerance is a fascinating trait, and understanding its mechanisms is important for predicting the survival of intertidal animals during extreme cold weather events. In this Review, we bring together current research on the ecology, biochemistry and physiology of this group of freeze-tolerant organisms. We first introduce the ecology of the intertidal zone, then highlight the strong geographic and taxonomic biases within the current body of literature on this topic. Next, we detail current knowledge on the mechanisms of freeze tolerance used by intertidal invertebrates. Although the mechanisms of freeze tolerance in terrestrial arthropods have been well-explored, marine invertebrate freeze tolerance is less well understood and does not appear to work similarly because of the osmotic differences that come with living in seawater. Freeze tolerance mechanisms thought to be utilized by intertidal invertebrates include: (1) low molecular weight cryoprotectants, such as compatible osmolytes and anaerobic by-products; (2) high molecular weight cryoprotectants, such as ice-binding proteins; as well as (3) other molecular mechanisms involving heat shock proteins and aquaporins. Lastly, we describe untested hypotheses, methods and approaches that researchers can use to fill current knowledge gaps. Understanding the mechanisms and consequences of freeze tolerance in the intertidal zone has many important ecological implications, but also provides an opportunity to broaden our understanding of the mechanisms of freeze tolerance more generally.

Microhabitat acclimatization alters sea anemone-algal symbiosis and thermal tolerance across the intertidal zone.

Contemporary symbioses in extreme environments can give an insight into mechanisms that stabilize species interactions during environmental change. The intertidal sea anemone, Anthopleura elegantissima, engages in a nutritional symbiosis with microalgae similar to tropical coral, but withstands more intense environmental fluctuations during tidal inundations. In this study, we compare baseline symbiotic traits and their sensitivity to thermal stress within and among anemone aggregations across the intertidal using a laboratory-based tank experiment to better understand how fixed genotypic and plastic environmental effects contribute to the successful maintenance of this symbiosis in extreme habitats. High intertidal anemones had lower baseline symbiont-to-host cell ratios under control conditions, but their symbionts had higher baseline photosynthetic efficiency compared to low intertidal anemone symbionts. Symbiont communities were identical across all samples, suggesting that shifts in symbiont density and photosynthetic performance could be an acclimatory mechanism to maintain symbiosis in different environments. Despite lower baseline symbiont-to-host cell ratios, high intertidal anemones maintained greater symbiont-to-host cell ratios under heat stress compared with low intertidal anemones, suggesting greater thermal tolerance of high intertidal holobionts. However, the thermal tolerance of clonal anemones acclimatized to different zones was not explained by tidal height alone, indicating additional environmental variables contribute to physiological differences. Host genotype significantly influenced anemone weight, but only explained a minor proportion of variation among symbiotic traits and their response to thermal stress, further implicating environmental history as the primary driver of holobiont tolerance. These results indicate that this symbiosis is highly plastic and may be able to acclimatize to climate change over ecological timescales, defying the convention that symbiotic organisms are more susceptible to environmental stress.

Characterization and ecological risk assessment of microplastics accumulated in sea water, sand, sediment, shell water and selected tissues of hermit crab of Sundarban Biosphere Reserve.

Sundarban, a Ramsar site of India, has been encountering an ecological threat due to the presence of microplastic (MP) wastes generated from different anthropogenic sources. Clibanarius longitarsus, an intertidal hermit crab of Sundarban Biosphere Reserve, resides within the abandoned shell of a gastropod mollusc, Telescopium telescopium. We characterized and estimated the MP in the gills and gut of hermit crab, as well as in the water present in its occupied gastropod shell. The average microplastic abundance in sea water, sand and sediment were 0.175 ± 0.145 MP L-1, 42 ± 15.03 MP kg-1 and 67.63 ± 24.13 MP kg-1 respectively. The average microplastic load in hermit crab was 1.94 ± 0.59 MP crab-1, with 33.89 % and 66.11 % in gills and gut respectively. Gastropod shell water exhibited accumulation of 1.69 ± 1.43 MP L-1. Transparent and fibrous microplastics were documented as the dominant polymers of water, sand and sediment. Shell water exhibited the prevalence of green microplastics followed by transparent ones. Microscopic examination revealed microplastics with 100-300 µm size categories were dominant across all abiotic compartments. ATR-FTIR and Raman spectroscopy confirmed polyethylene and polypropylene as the prevalent polymers among the five identified polymers of biotic and abiotic components. The target group index indicated green and black as the preferable microplastics of crab. The ecological risk analysis indicated a considerable level of environmental pollution risk in Sundarban and its inhabiting organisms. This important information base may facilitate in developing a strategy of mitigation to limit the MP induced ecological risk at Sundarban Biosphere Reserve.

Spatial distribution of PAHs and microbial communities in intertidal sediments of the Pearl River Estuary, South China.

The exploration of sediment pollution caused by PAHs and its impact on microbial communities can provide valuable insights for the remediation of sediments. The spatial distribution of PAHs and their impact on the microbial community within the Pearl River Estuary were investigated in this study. The findings revealed that the total concentration ranges of 16 PAHs were between 24.26 and 3075.93 ng/g, with naphthalene, fluorene, and phenanthrene potentially exerting adverse biological effects. More PAHs were found to accumulate in subsurface sediments, and their average accumulation rates gradually decreased as the number of rings in PAHs increased, ranging from 180 % for 2-ring to 36 % for 6-ring. The phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Chloroflexi were found to dominate both surface and subsurface sediments The correlation between microbial genera and PAHs contents was weak in sediments with low levels of PAHs contamination, while a more significant positive relationship was observed in sediments with high levels of PAHs contamination. The physicochemical properties of sediments, such as pH, soil structure and Cu significantly influence bacterial community composition in highly contaminated sediments. Additionally, the network analysis revealed that certain bacterial genera, including Novosphingobium, Robiginitalea and Synechococcus_CC9902, played a pivotal role in the degradation of PAHs. These findings are significant in comprehending the correlation between bacterial communities and environmental factors in intertidal ecosystems, and establish a scientific foundation for bioremediation of intertidal zones.

Investigating the interactive effects of habitat type and light intensity on rocky shores.

Light availability and habitat complexity are two key drivers of community assembly. Urbanisation has been shown to affect both, with important consequences to ecological communities. On the intertidal, for instance, studies have shown that light intensity is greater on natural rocky shores than on less complex artificial habitats (seawalls), though different habitats can also experience similar light intensities, for example when shaded by urban structures. Understanding therefore how these factors individually, and combined, affect communities is important to understand the mechanisms driving changes in community structure, and consequently provide solutions to tackle the increasing homogenisation of habitats and lightscapes in urbanised spaces through smart infrastructure designs. Here, we assessed how different light levels affect the recruitment of communities in rock pools and on emergent rock on an intertidal rocky shore. We cleared 30 patches of emergent rock and 30 rock pools and manipulated light using shades with different light transmissions (full light, procedural control, 75%, 35%, and 15% light transmission, full shade) and assessed mobile and sessile communities monthly for 6 months. Effects of reducing light levels were generally stronger on rock than in pools. Fully shaded plots supported double the amount of mobile organisms than plots in full sunlight, in both habitats. Algal cover was higher in pools compared to rock, and at intermediate light levels, but effects varied with site. This study highlights the importance of variable light conditions and different habitats for rocky shore communities, which should be considered in future coastal developments to retain natural biodiversity.

Spatial-temporal impacts of invasive Spartina anglica on the rates and pathways of organic carbon mineralization and resulting C-Fe-S cycles in the intertidal wetland of the Han River Estuary, Yellow Sea.

To elucidate the spatial-temporal impact of invasive saltmarsh plant Spartina anglica on the biogeochemical processes in coastal wetlands, we investigated the rates and partitioning of organic carbon (Corg) mineralization in three representative benthic habitats: (1) vegetated sediments inhabited by invasive S. anglica (SA); vegetated sediments by indigenous Suaeda japonica; and (3) unvegetated mud flats. Microbial metabolic rates were greatly stimulated at the SA site during the active growing seasons of Spartina, indicating that a substantial amount of organic substrates was supplied from the high below-ground biomass of Spartina. At the SA site, sulfate reduction dominated the Corg mineralization pathways during the plant growing season, whereas iron reduction dominated during the non-growing season. Overall, due to its greater biomass and longer growing season than native Suaeda, the expansion of invasive Spartina is likely to greatly alter the Corg-Fe-S cycles and carbon storage capacity in the coastal wetlands.