Subtropical Coastal Ecosystem Research Articles

Bacterial and fungal communities exhibit contrasting patterns in response to marsh erosion: A fine-scale observation

Coastal salt marshes, especially their seaward boundaries, are experiencing severe erosion and area loss worldwide because of human disturbances and natural changes. However, how marsh erosion affects soil microbial communities and their potential functions remains poorly understood in subtropical coastal ecosystems. Herein, simultaneous measurements of the abundance, diversity, and composition of bacterial and fungal communities were conducted along a marsh erosion gradient, based on Illumina sequencing of 16S rRNA and ITS genes. Our results indicate that marsh erosion is often accompanied by a loss of plant biomass and a decrease in soil total carbon, total nitrogen, and organic matter concentrations, but an increase in soil water content. We found that the abundance of bacteria and fungi tended to decrease with erosion, especially for bacterial communities. Marsh erosion had opposite effects on the alpha-diversity of bacterial and fungal communities, with bacterial diversity decreasing but fungal diversity increasing with marsh erosion. The beta-diversity and composition of bacterial and fungal communities were altered by marsh erosion, and in particular bacterial communities were clustered into three groups: uneroded, eroding, and eroded. Network analysis demonstrated that the inter-relationships of the bacterial community did not significantly change with the erosion gradient, but the complexity of the fungal networks increased. The diversity and composition of the bacterial and fungal communities can be jointly explained by plant biomass, soil nutrient dynamics, and bulk density. We conclude that marsh erosion-induced changes in soil properties and plant loss altered the diversity and composition of bacterial and fungal communities, which decrease bacterial abundance and diversity but increase fungal diversity and network complexity, suggesting that these microbial taxa contribute differently to soil function and nutrient cycling as marsh erosion continues.

Seasonal dynamics of antibiotic resistance genes and mobile genetic elements in a subtropical coastal ecosystem: Implications for environmental health risks

Antibiotic resistance poses a considerable global public health concern, leading to heightened rates of illness and mortality. However, the impact of seasonal variations and environmental factors on the health risks associated with antibiotic resistance genes (ARGs) and their assembly mechanisms is not fully understood. Based on metagenomic sequencing, this study investigated the antibiotic resistome, mobile genetic elements (MGEs), and microbiomes in a subtropical coastal ecosystem of the Beibu Gulf, China, over autumn and winter, and explored the factors influencing seasonal changes in ARG and MGE abundance and diversity. Results indicated that ARG abundance and diversity were higher in winter than in autumn, with beta-lactam and multidrug resistance genes being the most diverse and abundant, respectively. Similarly, MGE abundance and diversity increased in winter and were strongly correlated with ARGs. In contrast, more pronounced associations between microbial communities, especially archaea, and the antibiotic resistome were observed in autumn than in winter. The co-occurrence network identified multiple interactions between MGEs and various multidrug efflux pumps in winter, suggesting a potential for ARG dissemination. Multivariate correlation analyses and path modeling indicated that environmental factors driving microbial community changes predominantly influenced antibiotic resistome assembly in autumn, while the relative importance of MGEs increased significantly in winter. These findings suggest an elevated health risk associated with antimicrobial resistance in the Beibu Gulf during winter, attributed to the dissemination of ARGs by horizontal gene transfer. The observed seasonal variations highlight the dynamic nature of antibiotic resistance dissemination in coastal ecosystems, emphasizing the need for comprehensive surveillance and management measures to address the growing threat of antimicrobial resistance in vulnerable environments.

Spatiotemporal assessment of pathogenic Leptospira in subtropical coastal watersheds.

The World Health Organization classifies leptospirosis as a significant public health concern, predominantly affecting impoverished and unsanitary regions. By using the Pensacola Bay System as a case study, this study examines the underappreciated susceptibility of developed subtropical coastal ecosystems such as the Pensacola Bay System to neglected zoonotic pathogens such as Leptospira. We analyzed 132 water samples collected over 12 months from 44 distinct locations with high levels of Escherichia coli (>410 most probable number/100 mL). Fecal indicator bacteria (FIB) concentrations were assessed using IDEXX Colilert-18 and Enterolert-18, and an analysis of water physiochemical characteristics and rainfall intensity was conducted. The LipL32 gene was used as a quantitative polymerase chain reaction (qPCR) indicator to identify the distribution of Leptospira interrogans. The results revealed 12 instances of the presence of L. interrogans at sites with high FIB over various land cover and aquatic ecosystem types. Independent of specific rainfall events, a seasonal relationship between precipitation and elevated rates of fecal bacteria and leptospirosis was found. These findings highlight qPCR's utility in identifying pathogens in aquatic environments and the widespread conditions where it can be found in natural and developed areas.

Coastal degradation regulates the availability and diffusion kinetics of phosphorus at the sediment-water interface: Mechanisms and environmental implications

Coastal wetlands have experienced considerable loss and degradation globally. However, how coastal degradation regulates sediment phosphorus (P) transformation and its underlying mechanisms remain largely unknown in subtropical coastal ecosystems. This study conducted seasonal field measurements using high-resolution diffusive gradient in thin films (DGT) and dialysis (Peeper) techniques, as well as a DGT-induced fluxes in sediments (DIFS) model, to evaluate the mobilization and diffusion of P along a degradation gradient ranging from pristine wetlands to moderately and severely degraded sites. We observed that sediment P is diminished by coastal degradation, and severely degraded sites exhibit a decline in the concentration of available P, despite the presence of distinct seasonal patterns. High-resolution data based on DGT/Peeper analysis revealed that labile P and soluble reactive P (SRP) concentrations varied from 0.0006 mg L−1 to 0.084 mg L−1 (mean 0.0147 mg L−1) and from 0.0128 mg L−1 to 0.1677 mg L−1 (mean 0.0536 mg L−1), respectively. Coastal degradation had a substantial impact on increasing SRP and labile P concentrations, particularly at severely degraded sites. Although severely degraded wetlands appeared to be P sinks (negative P flux at these sites), we did also observe positive diffusive flux in October, indicating that coastal degradation may accelerate the diffusion and remobilization of sediment P into overlying water. The simulations of the DIFS model provided compelling proof of the high resupply capacity of sediment P at severely degraded sites, as supported by the increased R and k-1 values but decreased Tc values. Taken together, these results suggest coastal degradation reduces the sediment P pool, primarily attributed to the strong remobilization of P from the sediment to porewater and overlying water by enhancing the resupply capability and diffusion kinetics. This acceleration induces nutrient loss which adversely impacts the water quality of the surrounding ecosystem. To reduce the adverse effects of coastal degradation, it is essential to adopt a combination of conservation, restoration, and management efforts designed to mitigate the risk of internal P loading and release, and ultimately maintain a regional nutrient balance.

Is the use of drones cost-effective and efficient in detecting invasive alien trees? A case study from a subtropical coastal ecosystem

Is the use of drones cost-effective and efficient in detecting invasive alien trees? A case study from a subtropical coastal ecosystem

Assessing spatiotemporal variability in the concentration and composition of dissolved organic matter and its impact on iron solubility in tropical freshwater systems through a machine learning approach

Dissolved organic matter (DOM) plays important roles not only in maintaining the productivity and functioning of aquatic ecosystems but also in the global carbon cycle, although the sources and biogeochemical functions of terrestrially derived DOM have not been fully elucidated, particularly in the tropics and subtropics. This study aimed to evaluate the factors influencing spatiotemporal variability in (i) the concentration and composition of DOM, including dissolved organic carbon (DOC), ultraviolet absorption coefficient at 254-nm wavelength (a254), and components identified by fluorescence excitation–emission matrix coupled with parallel factor analysis (EEM-PARAFAC), and (ii) the concentration of dissolved iron (DFe) across freshwater systems (rivers, forested streams, and dam reservoirs) on a tropical island (Ishigaki Island, Japan) based on the results of water quality monitoring at 2-month intervals over a 2-year period. Random forests (RF) machine learning algorithm was employed, with the catchment characteristics (land use, soil type) and water temperature as the predictor variables for DOM and the composition of DOM (EEM-PARAFAC components) and hydrochemistry (water temperature, pH, and concentrations of divalent cations) as the predictor variables for DFe. The RF models for DOC, a254, and three humic-like components exhibited excellent predictive performance, indicating that these DOM properties are not only seasonally variable but also strongly influenced by the compositions of land uses and soil types in the upstream watershed. Poorly drained riparian lowland soil (Gleyic Fluvisols) was identified as the most important catchment parameter that positively influences these DOM variables. The RF model also explained a large portion of the variation in DFe, while terrestrial humic-like components were the most important parameters, emphasizing their significance as organic ligands for iron. These results improve our understanding of the impacts of terrestrial DOM and iron loadings on tropical and subtropical coastal ecosystems as well as on regional and global carbon budgets.

Spatial and temporal variability of phytoplankton dynamics in-relation to essential oceanographic variables in the south east coast of Bangladesh

Phytoplankton form the base of food chain and play a key role in maintaining the global climate system. However, very limited knowledge is available about the phytoplankton ecology of Bangladesh coast which is a representation of sub-tropical coastal ecosystem. Thus, this study aimed to understand the spatial and temporal variability of phytoplankton community in-relation to environmental variables in the South East coast of Bangladesh. Monthly data on essential oceanographic variables (i.e. temperature, salinity, dissolved oxygen, turbidity, silicate, nitrate and phosphate) and phytoplankton species abundance were collected from January 2022 to December 2022. We found a strong spatial and temporal variability in essential oceanographic variables and phytoplankton community compositions in Naf – Saint Martin Peninsula of Bangladesh. Estuarine ecosystem is characterized by high nutrients and low salinity while offshore ecosystem was found with comparatively low nutrients and high salinity. About 154 phytoplankton species were identified from the study area through year round sampling events. In the estuarine ecosystem Skeletonema marino, Coscinodiscus centralis, Coscinodiscus argus and Coscinodiscus traducens were found as the major contributing species at the estuarine ecosystem while Chaetoceros radican, Tripos trichoceros, Cylindrotheca Closterium, Chaetoceros convulutus, Tripos muelleri, and Cyclotella striata were found as the major contributing species at the offshore ecosystem. Our study found that 6 explanatory variables (i.e. temperature, salinity, turbidity, silicate, nitrate and phosphate) jointly explained about 78% variability in phytoplankton community dynamics. Nitrate concentration explained maximum variability (19%) followed by phosphate (17%), salinity (15%), silicate (12%), turbidity (10%) and surface temperature (5%). This study will play a key role in understanding the spatial and temporal variability of phytoplankton dynamics in the sub-tropical coastal ecosystem.

Environmental Controls of phytoplankton in the river dominated sub-tropical coastal ecosystem of Bangladesh

Sub-tropical coastal ecosystems are considered as the hotspot of species diversity. However, due to challenges regarding data collection, these regions are inherently data-limited and thus hindering informed species conservation strategies. Considering this, the present study aimed to assess the ecological characteristics of a river dominated sub-tropical coastal ecosystem of Bangladesh. More specifically, in this study we examined the spatial variability in environmental conditions and phytoplankton in the coastal ecosystems of Bangladesh. We also examined the causal relationship between environmental variables and phytoplankton species abundance. Data on environmental variables, including temperature, salinity, dissolved oxygen, turbidity, and macronutrients, was gathered in the north-east monsoon season between 2020 and 2022. We performed multivariate statistics to identify the variability in phytoplankton community dynamics. Results showed strong spatial variability in environmental conditions. Salinity, turbidity, nutrients concentrations and chlorophyll were found as the major drivers of this spatial heterogeneity. Central coast was characterized by low salinity, and high turbidity and silicate concentration while south-east coast was characterized by high salinity and low nutrient concentrations. In contrast, the south-west coast was characterized by high nitrate and phosphate, and moderate level of turbidity and salinity. Furthermore, our study identified 121 phytoplankton species. Maximum species diversity was observed in the south-west coast followed by central and south-east coast. Whereas 66 species occurred simultaneously in the three coastal zones, Coscinodiscus, Odontella and Nitzchia were the dominant phytoplankton genus in the central coastal zone. Skeletonema, Ditylum and Proboscia were found as dominant species in the south-east coastal zone. Coscinodiscus, Odontella, Nitzchia, Proboscia, Ditylum and Thalassionema were found as the key species in the south-west coastal zone. Seven explanatory variables (i.e. temperature, salinity, turbidity, silicate, nitrite, phosphate and zooplankton abundance) jointly explained about 44% to 73% variability in phytoplankton species abundance. We identified salinity and macronutrients as the major drivers of phytoplankton variability. This study is the first systematic report on phytoplankton community dynamics in-relation to environmental variables considering data from the entire coastal ecosystem of Bangladesh.

Strong Genetic Structure and Limited Gene Flow among Populations of the Tropical Seagrass Thalassia hemprichii in the Philippines

Seagrasses are marine angiosperms, and seagrass beds maintain the species diversity of tropical and subtropical coastal ecosystems. For proper understanding, management and conservation of coastal ecosystems, it is essential to understand seagrass population dynamics. Population genetic studies can cover large geographic scales and contribute to a comprehensive understanding of reproductive dynamics and potential dispersal among locations. The clonal and genetic diversity and genetic connectivity of Thalassia hemprichii in the Philippines were estimated by a population genetics approach. The geographic scale of this study has a direct distance of approximately 1600 km. Although high clonal diversity was found in some sites (R = 0.07–1.00), both sexual and asexual reproduction generally maintains separate populations. Genetic diversity is not definitely correlated with latitude, and genetic differentiation is significant in all pairs of sites (FST = 0.026–0.744). Complex genetic structure was found in some regions, even at a fine geographic scale. The migration of fruits and seedlings was elucidated as an infrequent and stochastic event. These results suggest the necessity for the conservation of this species due to a deficiency in migrants from external regions.

Annual Cycle of the Synechococcus spp. and Picoeukaryotic Growth and Loss Rates in a Subtropical Coastal Ecosystem

Seasonal variations in the picophytoplankton community structure (Synechococcus spp. and picoeukaryotes) were studied by flow cytometry in the coastal ecosystem of the subtropical western Pacific from October 2019 to September 2020. Synechococcus spp. was dominant in abundance during the study period, with its density ranging from 0.05 to 5.6 × 104 cells mL−1; its maximum occurred in July 2020. Picoeukaryotes were less abundant, with their density ranging from 0.2 to 13.6 × 103 cells mL−1. Their highest abundance was recorded in January 2020. The growth rates of Synechococcus spp. and picoeukaryotes ranged from −0.39 to 1.42 d−1 and 0.38 to 2.46 d−1, respectively, throughout the study period. Overall, the growth rate of the picoeukaryotes was significantly higher than that of Synechococcus spp. It is interesting to note that the grazing mortality of Synechococcus spp. and picoeukaryotes during the warmer period (April to September) was relatively low. Based on this study, we suggest that mixotrophic nanoflagellates lowered their feeding activity that obtained nutrients from prey and instead used additional nutrients during the incubation experiments. Our study demonstrated that a shift in the picophytoplankton community composition and grazing activity of predacious nanoflagellates in cold and warm periods can impact on the seasonal dynamics of the microbial food web.

Participatory mapping and fishers’ knowledge about fish and shrimp migration in a subtropical coastal ecosystem

Fishers’ ecological knowledge (FEK) has contributed to studies on the reproduction and migration of fish and marine invertebrates. With increasing accessibility to information technologies, several surveys have begun to use Geographic Information Systems (GIS) to access FEK through participatory mapping. Scientific knowledge on migration of fishery resources is fundamental to properly support initiatives for fisheries management. However, the technologies available to study migration are usually expensive and require several years of sampling. Our objective was to use GIS to access FEK and to identify the migration patterns of five fishery resources in a subtropical coastal ecosystem of the Southern Atlantic Ocean: the white catfish - Genidens barbus, the fat snook - Centropomus parallelus, the common snook - Centropomus undecimalis, the Atlantic spadefish - Chaetodipterus faber and the white shrimp - Litopenaeus schmitti. We interviewed 132 fishers in the Paranaguá estuarine complex and its adjacent coastal zone, Brazil. Of these fishers, 39 participated in the participatory mapping process. Our results based on FEK indicated that the migration of fishery resources is reproductive and occurs mainly in the later spring and summer when the species enter or exit the estuarine complex from coastal zone. The participatory mapping results indicated that G. barbus and C. faber migrate from the coastal zone to the estuary, while Centropomus species and the shrimp L. schmitti exit the estuary towards the coastal zone. The information generated by FEK and the methods used should be considered in future studies on ethno ecological research and to understand reproductive migration of these species. Furthermore, these observations could support fisheries management and environmental impact assessment of infrastructure projects.

Multi-year carbon and water exchanges over contrasting ecosystems on a sub-tropical sand island

Coastal wetland environments are an important sub-tropical ecosystem and a significant sink of carbon dioxide. They are under threat globally from coastal development, climate change, and sea level rise. Here we present eddy covariance measurements of carbon and water fluxes over three contrasting sub-tropical coastal ecosystems in eastern Australia: a wetland, an intermittently inundated swamp, and a commercial pine plantation. The aim is to quantify net ecosystem exchange and evapotranspiration to identify the meteorological and environmental factors that control carbon and water flux in these ecosystems. Results show that annual net ecosystem production ranged from 396 and 514 gC m-2 year-1 at the wetland, 571 and 694 gC m-2 year-1 at the pine plantation, and -74 and 108 gC m-2 year-1 at the swamp. In addition to photosynthetically available radiation and temperature, the strongest drivers of carbon flux were volumetric water content, vapour pressure deficit, and evapotranspiration at the wetland and swamp; at the swamp, leaf area index was also strongly correlated with carbon flux. In contrast, at the pine plantation, in addition to photosynthetically available radiation and temperature, only vapour pressure deficit had a strong correlation to carbon flux, with much weaker contribution from volumetric water content and leaf area index, and negligible correlation with evapotranspiration. Annual gross ecosystem production of the wetland site (2664–2739 gC m-2 year-1) was similar to those of tropical forests, while the pine plantation was the most effective at carbon capture from the atmosphere. Results provide valuable insight to these ecosystems and their water/carbon exchanges with the atmosphere, from which future change in response to climate change and land use change can be quantified.

Fishers’ ecological knowledge on the reproduction of fish and shrimp in a subtropical coastal ecosystem

Fishers’ ecological knowledge (FEK) has contributed to a better understanding about the reproduction of fishery resources, especially where biological data are scarce or unavailable. We analyzed FEK on the reproduction of five fishery resources in the Paranagua estuarine complex and adjacent coastal area, Brazil, including fishes (Genidens barbus, Centropomus parallelus, Chaetodipterus faber, Pseudobatos sp.) and shrimp (Litopenaeus schmitti). We also sought to compare FEK with biological data and investigate which characteristics (age, fish evisceration and fishers’ location) influence fishers' knowledge. We interviewed 132 artisanal fishers. FEK indicated reproductive peaks in the spring and summer for the fish species and in late winter and early spring for the shrimp. The maturation sizes according to FEK did not differ from sizes at first maturity (L50) as reported by biological studies for G. barbus and L. schmitti. Fishers’ residence sites and fish evisceration influenced more their knowledge related to species reproduction than age. Fishers showed a detailed ecological knowledge about some reproductive aspects, including size at first maturity of females, site of occurrence and reproductive peaks. Furthermore, fishers were able to identify sexual dimorphism, parental care and ovoviviparity. These results can be applied to improve fisheries management in the context of data poor fisheries.

Distribution gradient of fucoid algae (Sargassaceae, Phaeophyta) along the coastline of Okinawa Island, southern Japan: Relationship to environmental factors

Coastal ecosystems can provide significantly high ecosystem services via various processes. Tropical and/or subtropical coastal ecosystems are constituted by reef-building corals, macroalgae, and seagrasses. The study was conducted in a subtropical coastal area, Okinawa Island, Japan, where macroalgal beds are distributed. Since few studies have focused on the macroalgal community compared to corals in the study area, the relationship between macroalgal (especially Sargassaceae species) distribution and environmental factors were evaluated. Environmental parameters used in the analysis were obtained by field observation, geographic analysis, satellite observation of water quality, and numerical simulation of wave height. Sampling was conducted mainly between May and August in 2018 and 2019, and 31 sampling stations were established along the coastline of Okinawa Island. Though hermatypic corals occurred in most of the stations, the distribution of Sargassaceae was spatially skewed from the southern and central part of the east coast. Canonical correspondence analysis (CCA) was applied to obtained environmental variables and presence–absence data on macroalgae (Sargassaceae), corals, and seagrasses. CCA results indicated that the geographical setting (openness) and wave exposure in winter are the primary factors determining the macroalgal distribution, whereas nutrient (dissolved inorganic nitrogen, phosphorous, and silicon) concentrations at each sampling occasion were not significant factors. Since coastal ecosystems are threatened by both local and global impacts, elucidation of the major mechanism limiting Sargassaceae distribution is significant for coastal ecosystem management, here we use Okinawa Island as an example.

Extreme storms cause rapid but short-lived shifts in nearshore subtropical bacterial communities.

Climate change scenarios predict tropical cyclones will increase in both frequency and intensity, which will escalate the amount of terrestrial run-off and mechanical disruption affecting coastal ecosystems. Bacteria are key contributors to ecosystem functioning, but relatively little is known about how they respond to extreme storm events, particularly in nearshore subtropical regions. In this study, we combine field observations and mesocosm experiments to assess bacterial community dynamics and changes in physicochemical properties during early- and late-season tropical cyclones affecting Okinawa, Japan. Storms caused large and fast influxes of freshwater and terrestrial sediment - locally known as red soil pollution - and caused moderate increases of macronutrients, especially SiO2 and PO4 3-, with up to 25 and 0.5 μM respectively. We detected shifts in relative abundances of marine and terrestrially derived bacteria, including putative coral and human pathogens, during storm events. Soil input alone did not substantially affect marine bacterial communities in mesocosms, indicating that other components of run-off or other storm effects likely exert a larger influence on bacterial communities. The storm effects were short-lived and bacterial communities quickly recovered following both storm events. The early- and late-season storms caused different physicochemical and bacterial community changes, demonstrating the context-dependency of extreme storm responses in a subtropical coastal ecosystem.

Identification of Optimum Temperatures for Photosynthetic Production in Subtropical Coastal Ecosystems: Implications for CO2 Sequestration in a Warming World

AbstractTerrestrial ecosystems are often thought to be effective sinks of anthropogenic CO2 emissions with biosphere greening considered unequivocal evidence of this process. Increasing atmospheric concentrations of CO2 along with other greenhouse gases are however, responsible for global warming. As temperature increases, the rate at which biomes sequester CO2 may decline as the optimum temperature for photosynthetic production is exceeded, thereby reducing their potential to sequester CO2. Here we present evidence from 3 years of direct measurements of CO2 exchanges over subtropical coastal ecosystems in eastern Australia that the optimum temperature range for photosynthesis of 24.1°C to 27.4°C is routinely exceeded. This causes a rapid decline in photosynthetic production made worse when soil water content decreases. As climate change continues, both rising temperatures and predicted decline in rainfall will see these coastal ecosystems ability to sequester CO2 decrease further rapidly. We suggest similar research is needed urgently over other terrestrial ecosystems.

Microbial resistance and resilience in response to environmental changes under the higher intensity of human activities than global average level.

With the increasing intensity of global human activities, the ecosystem function, which is supported by the microbial community, will be dramatically changed and impaired. To investigate microbial resistance and resilience of microbial communities to human activities, we chose two typical types of human disturbances, urbanization, and reclamation under the higher intensity of human activities than the global average level. We examined microbial traits, including the abundance, diversity, phylogeny, and co-occurrence interactions in soil microbial communities, together with the nitrification activities observed in the subtropical coastal ecosystem of the Pearl River Estuary and in soil microcosm experiments. Microbial communities were less resistant to the environmental changes caused by urbanization than to those caused by reclamation, which was significantly reflected in the nitrogen and/or carbon-related patterns. However, most of the microbial traits could be recovered almost to the original level without significant differences in the microcosm after 40days of incubation. The co-occurrence interactions between nitrifiers and other microbial communities were dramatically changed and could not be completely recovered, but this change did not affect their nitrification activities for balancing the ammonium in the soil to the original level during the recovery stage, suggesting that the interactions between microbial communities might have fewer effects on their activities than previously thought. This study quantitatively demonstrated that microbial communities as a whole can recover to a status similar to the original state in a short time after the removal of stress at a large ecosystem scale even under the higher intensity of human activities than global average level in coastal ecosystems, which implied a strong recovery capacity of soil microbial community even after intense human disturbance.

The predominant role of soil in determining species composition of fern communities in subtropical coastal forest ecosystems

Ferns are an important component in the understorey of tropical forests and their distribution is influenced by several biotic and abiotic factors. At a regional scale, soil characteristics and canopy openness play an important role in fern species composition and richness, as well as in the abundance of individuals. Our objective was to compare the influence of edaphic conditions and vegetation structure on the abundance and distribution of fern communities in Atlantic forest andrestingaforest. Our hypotheses were that fern species richness and diversity are higher in Atlantic forest than inrestingadue to limiting conditions in this habitat and the composition of fern species in Atlantic forest differs fromrestinga, especially due to differences in edaphic conditions. A principal coordinates analysis was applied to ordinate sampling units in relation to the environmental variables and a permutational multivariate analysis of variance was used to test that environmental variables did not differ between the two vegetation types. Species richness was compared using rarefaction curves. The influence of abiotic variables in species composition and abundance was verified using canonical correspondence analysis. No differences were observed in species richness, diversity or dominance between vegetation types, although abundance was higher inrestinga. Fern communities respond to edaphic conditions and vegetation structure variations between vegetation types, the soil playing a major role. A greater variety of habitats resulting from differences in soil drainage inrestingafacilitates the co-existence of species with different ecological tolerance, increasing local diversity and compensating for limiting conditions inrestinga.

Influence of mangrove roots on microbial abundance and ecoenzyme activity in sediments of a subtropical coastal mangrove ecosystem

Although the rhizosphere effect has been widely studied, the relevant information about how mangrove roots affect microbial and enzymatic activity was still lacking due to the particularity of mangroves and intertidal zone. In order to understand the effects of mangrove roots on microbial growth and the indicators of nutrient cycling, microbial abundance as well as extracellular enzyme activities were investigated in both rhizosphere and non-rhizosphere sediments of a coastal mangrove wetland ecosystem. Comparing to non-rhizosphere sediments, bacterial abundance was slightly lower, but fungal abundance was notably higher in the rhizosphere sediments. Moreover, β-glucosidase (GLU), N-acetyl-glucosaminidase (NAG) and acid phosphatase (ACP) activities were enhanced clearly, whereas phenol oxidase (PHO) activity was significantly reduced in the rhizosphere sediments. Interestingly, it was found that soluble phenolics were closely related to fungal abundance and PHO activity (p < 0.05). Both fungal abundance and PHO activity were also significantly correlated with each other (p < 0.05). Therefore, the strong correlation between fungal abundance and both phenolics and PHO activity might partially suggest that fungi might contribute to the reduction of soluble phenolics.

Building a local spatial data infrastructure (SDI) to collect, manage and deliver coastal information

Mapping techniques and spatial data management in coastal areas are still the subject of methodological and technological development, especially regarding systems for the organization and integration of data and information. The availability of integrated and comprehensive spatial information within the context of a multidisciplinary project is therefore an important step towards to defining methodological solutions to the characterization of coastal environment and their interrelations for management. The “Biota/Araçá Project” (Biodiversity and functioning of a subtropical coastal ecosystem: subsidies for integrated management) is a multi-disciplinary program of biodiversity assessment of a small bay in Sao Paulo coast (Brazil). This paper discuss the issues involved in establishing a local spatial data infrastructure (SDI) developed to allow access, model and sharing of spatial data within such collaborative and multidisciplinary research project context.