Intertidal Environments Research Articles

Mid-Holocene relative sea-level changes along Atlantic Patagonia: New data from Camarones, Chubut, Argentina

This paper concerns the relative sea-level changes associated with the Atlantic Patagonian coast derived from sea-level index points whose elevation was determined by a differential global position system (DGPS). Bioencrustations from outcrops located near Camarones, Chubut, Argentina, consist of autochthonous deposits characterized by Austromegabalanus psittacus (Molina, 1782), encrusting acervulinid foraminifera, coralline red algae and bryozoans. The association of the different organisms is interpreted as being associated with an intertidal environment, and they have been used as index points to establish the relative sea-level position. The main conclusion is that the relative sea-level between c. 7000 and 5300 cal. yr BP was in the range of c. 2–4 m a.s.l., with a mean value of c. 3.5 m a.s.l. Our data seem to support the existence of different rates of relative sea-level fall in different sectors of Atlantic Patagonia during the Holocene and highlight the importance of a more precise and accurate relative sea-level estimation by producing new data and revisiting the indicative meaning of most of the indicators so far used in the area.

Reefcrete: Reducing the environmental footprint of concretes for eco-engineering marine structures

The ecological value of engineered marine structures can be enhanced by building-in additional habitat complexity. Pre-fabricated habitat units can be cheaply and easily cast from concrete into heterogeneous three-dimensional shapes and surface topographies, with proven ability to enhance biodiversity on artificial structures. The net ecological benefits of enhancement using concrete, however, may be compromised on account of its large environmental footprint and poor performance as substrate for many marine organisms. We carried out a pilot study to trial alternative cast-able “Reefcrete” concrete mixes, with reduced environmental footprints, for use in the marine environment. We used partial replacement of Portland cement with recycled ground granulated blast-furnace slag (GGBS), and partial replacement of coarse aggregate with hemp fibres and recycled shell material. We calculated the estimated carbon footprint of each concrete blend and deployed replicate tiles in the intertidal environment for 12 months to assess their performance as substrate for marine biodiversity. The hemp and shell concrete blends had reduced carbon footprints compared to both ordinary Portland cement based concrete and the GGBS based control concrete used in this study. At the end of the experiment, the hemp and shell blends supported significantly more live cover than the standard GGBS control blend. Taxon richness, particularly of mobile fauna, was also higher on the hemp concrete than either the shell or GGBS control. Furthermore, the overall species pool recorded on the hemp concrete was much larger. Community compositions differed significantly on the hemp tiles, compared to GGBS controls. This was largely explained by higher abundances of several taxa, including canopy-forming algae, which may have facilitated other taxa. Our findings indicate that the alternative materials trialled in this study provided substrate of equal or better habitat suitability compared to ordinary GGBS based concrete. Given the growing interest in ecological engineering of marine infrastructure, we propose there would be great benefit in further development of these alternative “Reefcrete” materials for wider application.

Comparative Analysis of Transcriptomes in Rhizophoraceae Provides Insights into the Origin and Adaptive Evolution of Mangrove Plants in Intertidal Environments.

Mangroves are woody plants that grow at the interface between land and sea in tropical and subtropical latitudes, where they exist in conditions of high salinity, extreme tides, strong winds, high temperatures, and muddy, anaerobic soils. Rhizophoraceae is a key mangrove family, with highly developed morphological and physiological adaptations to extreme conditions. It is an ideal system for the study of the origin and adaptive evolution of mangrove plants. In this study, we characterized and comprehensively compared the transcriptomes of four mangrove species, from all four mangrove genera, as well as their closest terrestrial relative in Rhizophoraceae, using RNA-Seq. We obtained 41,936–48,845 unigenes with N50 values of 982–1,185 bp and 61.42–69.48% annotated for the five species in Rhizophoraceae. Orthology annotations of Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Clusters of Orthologous Groups revealed overall similarities in the transcriptome profiles among the five species, whereas enrichment analysis identified remarkable genomic characteristics that are conserved across the four mangrove species but differ from their terrestrial relative. Based on 1,816 identified orthologs, phylogeny analysis and divergence time estimation revealed a single origin for mangrove species in Rhizophoraceae, which diverged from the terrestrial lineage ~56.4 million years ago (Mya), suggesting that the transgression during the Paleocene–Eocene Thermal Maximum may have been responsible for the entry of the mangrove lineage of Rhizophoraceae into intertidal environments. Evidence showed that the ancestor of Rhizophoraceae may have experienced a whole genome duplication event ~74.6 Mya, which may have increased the adaptability and survival chances of Rhizophoraceae during and following the Cretaceous–Tertiary extinction. The analysis of positive selection identified 10 positively selected genes from the ancestor branch of Rhizophoraceae mangroves, which were mainly associated with stress response, embryo development, and regulation of gene expression. Positive selection of these genes may be crucial for increasing the capability of stress tolerance (i.e., defense against salt and oxidative stress) and development of adaptive traits (i.e., vivipary) of Rhizophoraceae mangroves, and thus plays an important role in their adaptation to the stressful intertidal environments.

Taxonomy and distribution of benthic foraminifera in an intertidal zone of the Yellow Sea, PR China: Correlations with sediment temperature and salinity

Abstract Seasonal variations in foraminiferal populations from the intertidal environment of the Yellow Sea are not well known. This results in restricted understanding of environmental implications of foraminifera and their application in paleoenvironment reconstruction in this region. Community dynamics of both living and total (living plus dead) assemblages in a Qingdao intertidal flat were investigated from 2010 to 2012 during 17 months' sampling in two intertidal zones. Our study revealed a distinct seasonal variation in assemblages, which was more prominent in the low intertidal area. Foraminiferal abundance, species richness and Margalef index showed significant positive correlations to salinity, while species richness was negatively associated with temperature. A total of 52 species was identified and illustrated, including the dominant species: Ammonia beccarii , A. aomoriensis , A. aberdoveyensis , A. sobrina , Quinqueloculina seminula and Murrayinella globosa. Foraminiferal community parameters in the low intertidal area were higher than those in the high intertidal area, especially for the living assemblages, reflecting a seaward preference. Our study revealed that different tidal levels (low vs. high intertidal) had a more distinct influence in regulating foraminiferal assemblages than did seasonal influence.

High fragility of the soil organic C pools in mangrove forests

Mangrove forests play an important role in biogeochemical cycle of C, storing large amounts of organic carbon. However, these functions can be controlled by the high spatial heterogeneity of these intertidal environments. In this study were performed an intensive sampling characterizing mangrove soils under different type of vegetation (Rhizophora/Avicennia/dead mangrove) in the Venezuelan coast. The soils were anoxic, with a pH~7; however other soil parameters varied widely (e.g., clay, organic carbon). Dead mangrove area showed a significant lower amounts of total organic carbon (TOC) (6.8±2.2%), in comparison to the well-preserved mangrove of Avicennia or Rhizophora (TOC=17–20%). Our results indicate that 56% of the TOC was lost within a period of 10years and we estimate that 11,219kgm−2 of CO2 was emitted as a result of the mangrove death. These results represent an average emission rate of 11.2±19.17tCO2ha−1y−1.

Trophic and stoichiometric consequences of nutrification for the intertidal tropical zoanthid Zoanthus sociatus

Zoanthids are conspicuous and abundant members of intertidal environments, where they are exposed to large environmental fluctuations and subject to increasing loads of anthropogenic nutrients. Here we assess the trophic ecology and stoichiometric consequences of nutrient loading for symbiotic zoanthids inhabiting different intertidal habitats. More specifically, we analysed the stable isotope signature (δ13C and δ15N), elemental composition (C, N and P) and stoichiometry (C:N, C:P, N:P) of Zoanthus sociatus differently exposed to nutrification. Results suggest that autotrophy is the main feeding mode of zoanthids and that the effect water nutrient content differently affects the elemental phenotype of zoanthids depending on tidal habitat. Additionally, habitat effects on Z. sociatus P-related stoichiometric traits highlight functional differences likely associated with variation in Symbiodinium density. These findings provide an innovative approach to assess how cnidarian-dinoflagellate symbioses response to ecosystem changes in environmentally dynamic reef flats, particularly nutrient loading.

Behavioral and physiological photoresponses to light intensity by intertidal microphytobenthos

Behavioral and physiological responses to light are the two major mechanisms by which natural microphytobenthic assemblages adapt to the intertidal environment and protect themselves from light stress. The present study investigated these photoresponses with different light intensities over 8 h of illumination, and used a specific inhibitor (Latrunculin A, Lat A) for migration to compare migratory and non-migratory microphytobenthos (MPB). Photosynthetic activity was detected using rapid light curves and induction curves by chlorophyll fluorescence. It showed distinct variation in migratory responses to different light intensities; high light induced downward migration to avoid photoinhibition, and low and medium light (50–250 μmol/(m2·s)) promoted upward migration followed by downward migration after certain period of light exposure. No significant difference in non-photochemical quenching (NPQ) or PSII maximal quantum yield (Fv/Fm) was detected between low and medium light irradiance, possibly indicating that only high light influences the photosynthetic capability of MPB. Decreased photosynthetic activity, indicated by three parameters, the maximum relative electron transport rate (rETR max), minimum saturating irradiance (Ek) and light utilization coefficient (α), was observed in MPB after exposure to prolonged illumination under low and medium light. Lat A effectively inhibited the migration of MPB in all light treatments and induced lower Fv/Fm under high light (500 and 100 μmol/(m2·s)) and prolonged illumination at 250 μmol/(m2·s), but did not significantly influence Fv/Fm under low light (0–100 μmol/(m2·s)) or NPQ. The increase of NPQ in Lat A treatments with time implied that the MPB assemblages can recover their physiological photoprotection capacity to adapt to light stress. Non-migratory MPB exhibited lower light use efficiency (lower α) and lower maximum photosynthetic capacity (lower rETR max) than migratory MPB under light intensities above 250 μmol/(m2·s) after 4.0 h illumination.

Inhabiting fauna in holdfasts of Lessonia nigrescens complex. Is it an indicator of ecological integrity in exploited kelp beds in northern Chile?

Lessonia nigrescens complex holdfasts habitats are home to a wide diversity of invertebrates. The holdfasts associated fauna is sensitive to the kelp fishery in northern Chile because one of the management recommendation is to harvest the whole plant. Considering the above, and the ecological role play by brown algae as foundation species, this study proposes the use of fauna inhabiting the holdfasts as an ecological indicator to monitor the integrity of exploited kelp beds. To accomplish this objective, the morphology of plants and holdfasts was evaluated together with the composition, abundance and community structure associated in three types of resource conservation strategies based on fishery management spatially explicit: open access areas and management areas (to harvest), and marine protected areas (with no harvest), in Atacama and Coquimbo (26-32°S). The results show that high harvest pressure on exploited kelp beds transforms the plant morphology and holdfast, altering the colonization process and species aggregation predicted for these biogenic habitats modifying the expected biodiversity. Thus, associated fauna in open access areas has lower species richness, abundance and biodiversity of organisms than their counterparts in management areas or marine protected areas. Moreover, the structure of the holdfast associated communities, are more variables in open access areas. The results suggest that holdfasts are representative micro-ecosystems of the intertidal environment, and can be used as sampling replicable and comparable units to monitor exploited kelp beds integrity in fisheries open access areas. This ecological indicator is easy to evaluate and disseminate among users of the kelp productive chain.

Assessing the morphological and physiological adaptations of the parasitoid wasp Echthrodesis lamorali for survival in an intertidal environment

AbstractAs a result of a variety of chemical, environmental, mechanical and physiological difficulties, insects that spend their entire life spans in the marine or intertidal region are relatively rare. The present study assesses whether morphological and physiological adaptations have evolved in a maritime parasitoid wasp species Echthrodesis lamorali Masner, 1968 (Hymenoptera: Platygastridae, Scelioninae), in response to environmental pressures on its respiratory functioning. Scanning electron and light microscopy of whole and sectioned specimens show the presence of structure‐retaining taenidia in the tracheal tubes, although there is an absence of other major adaptations associated with the trachea or spiracles. Histological sectioning reveals the presence of unusual sacs in the female metasoma whose role is unknown, although they are hypothesized to most likely be linked to ovipositor control. Respirometry experiments illustrate the formation of a plastron when submerged, with the longevity of the wasps being increased by quiescence. The critical thermal range of E. lamorali is shown to be large: from −1.1 °C ± 0.16 to 45.7 °C ± 0.26 (mean ± SE). Behavioural and physiological adaptations in E. lamorali appear to have evolved in response to exposure to the heterogeneous environmental conditions experienced within the intertidal zone.

Metal concentrations in intertidal water and surface sediment along the west coast of the Cape Peninsula, Cape Town, South Africa

The concentrations of metals in intertidal water and surface sediment were measured at Scarborough, Hout Bay, Green Point, Milnerton and Bloubergstrand in Cape Town, South Africa, between Autumn 2010 and Autumn 2011. In terms of Pollution Load Index (PLI) of metals in the sediment, the sites were ranked in the following order: Bloubergstrand > Hout Bay > Green Point > Milnerton > Scarborough. Seasonally, metal loads were highest in Autumn 2011 and lowest in Autumn 2010. The higher metal concentrations reported in sediment suggested that both localised anthropogenic and natural weathering were the sources of metals recorded. Surprisingly, metal concentrations were similar to those reported in 1985 for the same sites, suggesting that the intertidal environment in Cape Town has not been increasingly contaminated with metals. The findings provide a baseline of metal concentrations that can be used for further research in the region. Keywords : metals, intertidal water, sediment, contamination factor, pollution load index, Cape Town

Prehistoric Human Impacts to Marine Mollusks and Intertidal Ecosystems in the Pacific Islands

ABSTRACTFrom long-term stratigraphic records in Pacific Island archaeological sites, researchers have documented alterations to molluskan species richness and abundance, decreases or increases in mollusk shell size and, in rare cases, human foraging may have contributed to the extirpation of mollusk taxa. Mollusks perform critical ecosystem functions in tropical intertidal environments, including improving water quality through filtration, regulating algal cover, and increasing habitat and substratum complexity through ecosystem engineering. These critical ecosystem functions can be negatively affected by human foraging, possibly contributing to decreased resilience of coral reefs to climatic alterations. We review modern ecological research on human impacts to mollusks and intertidal ecosystems that illustrates the mechanisms and effects of human foraging. We then examine centuries to millennial scale archaeological records from the Pacific Islands to understand long-term, time-averaged trends in human impacts to intertidal ecosystems.

Asociaciones de ostrácodos bentónicos actuales y del Holoceno del estuario de Bahía Blanca (Buenos Aires, Argentina): interpretaciones paleoambientales

The study of ostracod fauna in sediment samples from present environments at the Bahia Blanca estuary led to the identification of different ostracod associations, through which it was possible to identify Holocene depositional environments. Based on the systematic analysis of the ostracods present in different core levels, a total of 11 genera represented by 13 species of benthic ostracods were identified, out of which Neocytherideis ruidis, Loxocythere variasculpta and Callistocythere litoralensis were dominant along the core. The quantitative and qualitative analysis of ostracods from the Holocene allowed us to determine the following palaeoenvironments: at the base of the core the sediments were deposited in an intertidal environment with developed mudflats; the middle sector evidenced an increase in environmental energy; and the upper portion of the core contained deposits of marshes environment with greater freshwater input. The detailed study of the benthic Ostracoda allowed to identify palaeoenvironments and to provide new evidence of negative fluctuations of the mean sea level for the Holocene.

A regression approach to the mapping of bio-physical characteristics of surface sediment using in situ and airborne hyperspectral acquisitions

Remote sensing has been successfully utilized to distinguish and quantify sediment properties in the intertidal environment. Classification approaches of imagery are popular and powerful yet can lead to site- and case-specific results. Such specificity creates challenges for temporal studies. Thus, this paper investigates the use of regression models to quantify sediment properties instead of classifying them. Two regression approaches, namely multiple regression (MR) and support vector regression (SVR), are used in this study for the retrieval of bio-physical variables of intertidal surface sediment of the IJzermonding, a Belgian nature reserve. In the regression analysis, mud content, chlorophyll a concentration, organic matter content, and soil moisture are estimated using radiometric variables of two airborne sensors, namely airborne hyperspectral sensor (AHS) and airborne prism experiment (APEX) and and using field hyperspectral acquisitions by analytical spectral device (ASD). The performance of the two regression approaches is best for the estimation of moisture content. SVR attains the highest accuracy without feature reduction while MR achieves good results when feature reduction is carried out. Sediment property maps are successfully obtained using the models and hyperspectral imagery where SVR used with all bands achieves the best performance. The study also involves the extraction of weights identifying the contribution of each band of the images in the quantification of each sediment property when MR and principal component analysis are used.

Geochemistry of Core Sediments from Tropical Mangrove Region of Tamil Nadu: Implications on Trace Metals

The present study aims to determine the concentrations of certain trace metals (Fe, Mn, Cr, Cu, Pb, Zn, Co, Ni, Ba, Sr, V and Rb) and to identify the possible sources of the trace metals with multivariate analyses and assess the metal contamination using the enrichment factor (EF) and geo-accumulation index (Igeo) from the two core samples taken from Pichavaram lagoon. Pichavaram mangrove is a dynamic intertidal environment lying in between Vellar and Coleroon estuaries in Cauvery delta along the east coast of India. High OM in the present study is noted in both core samples which are mainly controlled by productivity and sediment texture. The increase of trace metals concentrations was observed at lower intersects which indicates that the trace metals were reprecipitated around the redox boundaries. Further it signifies that the enrichment of metals in C1 core sample is closely related to the diagenetic. Factor 1 with significant positive loadings on Mud and good loadings on Fe and Mn suggests the associations of these metals with finer sediment fractions and aluminosilicates. These elements to be enriched in the clay fraction in both core samples. They are mainly related to anthropogenic inputs and reflect the complexing nature of the organic matter. Igeo studies confirm the contamination of the study area. Overall the study highlights significant anthropogenic contributions in terms of heavy metal pollution. Comparative data for normalized enrichment factors and the modified degree of contamination show that Pichavaram sediments have suffered significant systematic heavy metal contamination following catchment urbanization.

Niche dimension differs among life-history stages of Pacific oysters in intertidal environments

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 562:113-122 (2016) - DOI: https://doi.org/10.3354/meps11961 Niche dimension differs among life-history stages of Pacific oysters in intertidal environments Brenda Walles1,2,3,*, Aad C. Smaal1,2, Peter M. J. Herman3, Tom Ysebaert1,3 1Wageningen Marine Research, Wageningen University & Research, PO Box 77, 4400 AB Yerseke, The Netherlands 2Aquaculture and Fisheries Group, Wageningen University and Research, PO Box 338, 6700 AH Wageningen, The Netherlands 3NIOZ Yerseke, Royal Netherlands Institute for Sea Research and Utrecht University, PO Box 140, 4400 AC Yerseke, The Netherlands *Corresponding author: brenda.walles@nioz.nl ABSTRACT: Structure-building, autogenic ecosystem engineers are recognized worldwide as potential tools for coastal protection, which depends on long-term sustainability and persistence of their structures. For reef-building oysters, reefs are maintained through accumulation of shell material, which depends on recruitment and growth and which provides substrate for new generations. Knowledge of the fundamental niche of oysters in relation to biotic and abiotic conditions helps define the area where ecosystem engineers grow and survive well and where their structures are likely to persist and be effective for coastal protection. Response curves of different life-history stages (larvae, juveniles and adults) of the Pacific oyster Crassostrea gigas were investigated along a tidal emersion gradient in a manipulative field study. Density of juvenile oysters was maximal around 36% tidal emersion. Shell growth of juveniles and adults, condition index (CI) of adults and mortality of adults were negatively related to tidal emersion, whereas mortality of juveniles was positively related to tidal emersion. Tidal emersion had a strong effect on oyster survival and growth, with the most favourable being around 20 to 40% tidal emersion, as indicated by recruit density and the CI of adults. These findings suggest that the area of 20 to 40% tidal emersion is optimal for reef development, which is in line with other investigations of C. gigas and the eastern oyster C. virginica across different systems, supporting a broader geographical application of these findings. KEY WORDS: Oyster reef · Ecosystem engineering · Recruitment · Growth · Niche · Ecosystem-based management · Tidal flats Full text in pdf format Supplementary material PreviousNextCite this article as: Walles B, Smaal AC, Herman PMJ, Ysebaert T (2016) Niche dimension differs among life-history stages of Pacific oysters in intertidal environments. Mar Ecol Prog Ser 562:113-122. https://doi.org/10.3354/meps11961 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 562. Online publication date: December 29, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Seven new species of the genus Xestoleberis (Ostracoda: Podocopida:Cytheroidea) from the Fiji Archipelago.

The genus Xestoleberis has a global distribution, and although they are predominant in shallow marine environments adapted to both sediment and algal habitats, only two species of this genus, Xestoleberis curta (Brady, 1866) and Xestoleberis variegata Brady, 1880, have previously been reported from the Fiji archipelago. Herein we report seven new species of the genus Xestoleberis from intertidal environments of fringing reef flats of the Fiji Islands: Xestoleberis becca n. sp., Xestoleberis concava n. sp., Xestoleberis gracilariaii n. sp., Xestoleberis marcula n. sp., Xestoleberis natuvuensis n. sp., Xestoleberis penna n. sp. and Xestoleberis petrosa n. sp. With the exception of X. becca n. sp., Xestoleberis species show restricted distribution within Fijian waters. The possible causes for their distribution patterns are suggested to be physical barriers imposed by the fast flowing Bligh Water currents, and islands separated by deep ocean waters.

Sedimentation rhythms and hydrodynamics in two engineered environments in an open coast managed realignment site

Managed Realignment (MR) schemes are considered by many coastal managers and engineers to be a preferable method of coastal flood defence and compensating for habitat loss, by creating new areas of intertidal saltmarsh and mudflat habitat. Monitoring of MR sites has tended to focus on short term ecological factors, resulting in a shortage of high frequency, high resolution long term measurements of the evolution of the sediment erosion, transportation, deposition and consolidation cycle (ETDC) in newly breached sites. This is particularly true of analysis of the formation and preservation of sedimentary rhythmites and evaluations of sedimentation rates (and their variability) in newly inundated intertidal environments. This study provides an evaluation of sedimentation rhythms and hydrodynamics from two contrasting sites within the Medmerry Managed Realignment scheme, the largest open coast realignment in Europe (at the time of site inundation). Bed sediment altimeter data highlighted different sedimentation patterns at the two sites; near constant deposition of sediment occurred near the breach resulting in 15.2cm of sediment being accreted over the one year monitoring period, whereas periodic accretion and erosion of sediment occurred inland leading to 2.7cm of net accretion. Differences in the relationship between suspended sediment concentrations and site hydrodynamics were observed on a semi-diurnal to annual scale. This study highlights the need for further consideration of the sedimentation processes in MR schemes in order to enhance the design and construction of these sites. Advancements in the understanding of these processes will increase the success of MR schemes in terms of the evolution of the sediment regime and the ecosystem services provided, particularly as they are more widely accepted as a form of coastal flood defence and intertidal habitat creation method.

Global microbial carbonate proliferation after the end-Devonian mass extinction: Mainly controlled by demise of skeletal bioconstructors.

Microbial carbonates commonly flourished following mass extinction events. The end-Devonian (Hangenberg) mass extinction event is a first-order mass extinction on the scale of the ‘Big Five’ extinctions. However, to date, it is still unclear whether global microbial carbonate proliferation occurred after the Hangenberg event. The earliest known Carboniferous stromatolites on tidal flats are described from intertidal environments of the lowermost Tournaisian (Qianheishan Formation) in northwestern China. With other early Tournaisian microbe-dominated bioconstructions extensively distributed on shelves, the Qianheishan stromatolites support microbial carbonate proliferation after the Hangenberg extinction. Additional support comes from quantitative analysis of the abundance of microbe-dominated bioconstructions through the Famennian and early Tournaisian, which shows that they were globally distributed (between 40° latitude on both sides of the palaeoequator) and that their abundance increased distinctly in the early Tournaisian compared to the latest Devonian (Strunian). Comparison of variations in the relative abundance of skeleton- versus microbe-dominated bioconstructions across the Hangenberg and ‘Big Five’ extinctions suggests that changes in abundance of skeletal bioconstructors may play a first-order control on microbial carbonate proliferation during extinction transitions but that microbial proliferation is not a general necessary feature after mass extinctions.

Comparative transcriptome analyses of a mangrove tree Sonneratia caseolaris and its non-mangrove relatives, Trapa bispinosa and Duabanga grandiflora

Mangroves are a group of unique plants anchoring in and well adapting to the extreme intertidal environment with high salinity, hypoxia and high temperature and ultraviolet (UV) radiation. Sonneratia caseolaris is a major mangrove tree widely distributed across the West-Indo Pacific region, however the genetic mechanisms of its adaptive evolution are still unclear. In the present study, we performed comparative transcriptome analyses between S. caseolaris and its two non-mangrove relatives, Trapa bispinosa and Duabanga grandiflora, to better understand the evolutionary adaptation of S. caseolaris. We obtained 39.92, 69.96 and 47.78 million high-quality paired-end reads using the Illumina platform and de novo assembled them into 47,954, 73,284 and 66,459 unigenes with low redundancy and high coverage. Of them, 20,181, 28,657 and 25,244 unigenes were successfully assigned to level-2 Gene Ontology (GO) terms, and we found the distribution of GO terms were similar among the three species. Approximate 56% unigenes were involved in “response to stimulus” in all three species. Furthermore, we identified 23 unigenes under positive selection in S. caseolaris, which may be crucial for adaptation of this mangrove species to the extreme intertidal environment.

Evaluation of fermentation conditions triggering increased antibacterial activity from a near-shore marine intertidal environment-associated Streptomyces species

A near-shore marine intertidal environment-associated Streptomyces isolate (USC-633) from the Sunshine Coast Region of Queensland, Australia, cultivated under a range of chemically defined and complex media to determine optimal parameters resulting in the secretion of diverse array of secondary metabolites with antimicrobial properties against various antibiotic resistant bacteria. Following extraction, fractioning and re-testing of active metabolites resulted in persistent antibacterial activity against Escherichia coli (Migula) (ATCC 13706) and subsequent Nuclear Magnetic Resonance (NMR) analysis of the active fractions confirmed the induction of metabolites different than the ones in fractions which did not display activity against the same bacterial species. Overall findings again confirmed the value of One Strain–Many Compounds (OSMAC) approach that tests a wide range of growth parameters to trigger bioactive compound secretion increasing the likelihood of finding novel therapeutic agents. The isolate was found to be adaptable to both marine and terrestrial conditions corresponding to its original near-shore marine intertidal environment. Wide variations in its morphology, sporulation and diffusible pigment production were observed when different growth media were used.