How nematode morphometric attributes integrate with taxonomy-based measures along an estuarine gradient

Nematodes are highly susceptible to environmental change and possess a wide array of morphological and functional characteristics for the assessment of the “Good Environmental Status”, within Marine Strategy Framework Directive. However, while the taxonomic sufficiency of nematodes in detecting spatial gradients and related ecological niche conditions is well recognized, very little is known about nematodes functional morphometric attributes in response to environmental drivers. To explore this knowledge gap, we aimed to assess the efficacy and efficiency of nematode morphometric attributes (length, width, length/width ratio, biomass) in detecting spatial patterns along a Portuguese estuarine gradient, and compare it with the taxonomic approach. We hypothesized that abundance data weighted by the morphometric attributes will have a higher explanatory power in detecting spatial patterns than using abundance of morphometric data alone. Based on the recent recommendations regarding the time and cost related efficacy of methods in biomonitoring and ecological assessments we also hypothesized that a reduced dataset based on the most common genera will suffice to capture the same distributional patterns displayed by the whole assemblage. Our results demonstrated that dataset solely based on genera abundances had consistently better explanatory power than combined datasets or morphometric datasets alone, however, combined dataset provided different spatial patterns and performed better at discriminating estuary areas. The main gradients described by the taxonomy-based dataset were related to the sediment particle size and water depth. Considering combined datasets, spatial discrimination was mainly driven by the variation in dissolved oxygen % saturation, pointing out to the importance of this variable in determining estuarine conditions substantial for nematodes morphometric distributional patterns. The same analysis repeated for the most frequent genera resulted in similar distributional patterns as for the whole assemblage dataset, clearly demonstrating that spatial estuarine gradients can be sufficiently described by using only the most frequent genera. Such information may substantially increase the efficiency of bio-assessment surveys by reducing the cost and work associated with identification and measurements of all of the individual nematode genera

Variação da distribuição espacial das comunidades meiobentónicas dos sedimentos subtidais, sujeitos a diferentes níveis de pressão antropogénica: estuários do Mira e Mondego

Esta apresentação oral Analisa o padrão de distribuição espacial das comunidades subtidais de meiofauna ao longo dos gradientes estuarinos, nomeadamente ao longo dos gradientes de salinidade. Concluindo quea composição trófica das comunidades de nemátodes parecem permitir distinguir o efeito do stress natural do stress antropogénico na variabilidade das comunidades meiobentónicas

Nematodes vs Macrofauna assemblages along an estuarine gradient (Mondego estuary, Portugal)

The spatial distribution of the nematodes and macrofauna communities in the subtidal sediments along estuarine gradient in the Mondego estuary was studied. The main aim is to compare the response of the nematodes and macrofauna communities structure adjusted for each estuarine stretch. Spatial distribution of nematode assemblages followed the estuarine gradients, allowing to distinguish: The freshwater and oligohaline sections, characterised by the presence of freshwater nematodes, low densities and diversity; Mesohaline section, the densities and diversity were also low; Polyhaline and Euhaline sections, attained highest densities and diversity. Significant differences of diversity were obtained between estuarine sections by Shannon-Wiener index. Significant differences in macrofauna densities were also obtained, the highest values were obtained in euhaline and mesohaline areas. The euhaline stations presented higher species richness, while the freshwater section registered lower values. Significant differences of diversity were also obtained between estuarine sections by Shannon-Wiener index. From the management point of view both communities are very useful in assessing ecological quality in transitional waters, however the rapid response of nematodes to environmental changes became an important tool

M162 – GLORIA FLOW: Exploring subsurface fluid flow and active dewatering along the oceanic plate boundary between Africa and Eurasia (Gloria Fault)

Between 06.03.2020 and 11.04.2020 a R/V Meteor cruise M162 was conducted along the unexplored area of the Gloria Fault between the Azores Plateau and the Madeira-Tore Rise in the central Northeast Atlantic.The results obtained during the cruise might have important implications concerning the alteration of oceanic lithosphere and their control on tectonic and seismic activity as well as the spread of chemosyn thetic ecosystems and the understanding of global element cycles. Simultaneously, the meiofauna samples were collected with the main aim to establish the link between sedimentary conditions, microbial diversity and nematode communities and to analyze the large-scale distributional patterns of nematode assemblages along the Oceanic Plate boundary between Africa and Eurasia - Gloria Fault (Central North Atlantic)

Recovery of Benthic Nematodes Assemblages After a Major Collapse in Seagrass Beds of Zostera Noltii.

During 2008, Zostera noltii seagrass beds of the Mira estuary (SW coast of Portugal) suffered a total collapse. During 2009 symptoms of early recovery were observed. The availability of pre-collapse data and the sequence of sudden collapse followed by early and gradual recovery create a rare natural experiment on recovery and resilience of seagrass ecosystems. The principal goal of this study is to assess the evolution and resilience of the benthic nematodes assemblages during the natural recovery of the seagrass beds through analysis of the spatial and seasonal differences in structural and functional characteristics of the communities. The horizontal macroscale (km). and small scale variability will be evaluate. We hypothesize that the new environmental conditions of the early recovery, with sparsely distributed and small-sized seagrass patches, will increase the spatial heterogeneity of nematode communities and significantly affect community diversity, both taxonomic and functional. The sampling design was follows: Samples were collected in four “occasions”, (June, September, Dezember 2010 and February 2011), at randomly “stations” located over a distance 50 m, at two “sites”, 2km distance. In order to test the hypothesis that the composition of nematodes assemblages changes spatially and seasonally a two–way PERMANOVA analysis was performed. Mean nematode densities varied between 2 ind. 10 cm-2 and maximum of 4735 ind. 10 cm-2 both at station B and 89 species were identified. The PCO ordination based on abundance and composition of nematode genera clearly reflected the discrimination of the two sites, and Permanova analysis showed significant differences across “sites”, and sampling stations, nevertheless no significant differences was observed between “sampling occasions. The increase of spatial heterogeneity was clear identified. The response of the nematode assemblages after an extreme event as the collapse of the seagrass bed, both in terms of density and diversity, highlight a substantial resilience and recovery potential

Food web analysis of meiobenthos in estuarine seagrss bed.

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at a genus/species level in an estuarine food web in Zostera noltii beds and in adjacent sediments, using natural abundances of stable carbon and nitrogen isotopes. Microphytobenthos is among the main resources of most taxa, but seagrass-associated resources also contribute to meiobenthos nutrition, with seagrass detritus being available also in deeper sediments and in unvegetated patches close to seagrass beds. A predominant reliance on chemoautotrophic bacteria was demonstrated for the nematode Terschellingia and the copepod family Cletodidae

Spatial distribution of subtidal meiobenthos along estuarine gradients in two Southern European estuaries (Portugal).

Abstract The spatial variation in abundance and composition of subtidal meiobenthos communities was studied in two Portuguese estuaries under distinct degrees of anthropogenic pressure. Samples were collected from 20 sampling stations along both estuarine gradients from freshwater (30). Of these stations 11 were located in the Mondego estuary, a system exposed to high anthropogenic stress, and 9 in the Mira estuary, a naturally stressed system located inside the Natural Park ‘Costa Vicentina’ (south-western coast of Portugal). Total meiobenthos density was higher in the Mira estuary and in both estuaries the community was dominated by nematodes. Among the twelve taxa identified in the Mira estuary, Harpacticoid copepods and Polychaeta were the second and the third most abundant groups respectively. In the Mondego estuary, Polychaeta was the second while Harpacticoid copepods was the third most abundant group in the thirteen total taxa recorded. Estuarine gradients of salinity, particles size and water nutrients were clearly detected in both estuaries and there was significant spatial heterogeneity in abundance and composition of the subtidal meiobenthos communities along these environmental gradients. Accordingly, three distinct sections were identified in both estuaries: (i) freshwater sections, where total density, and density of nematodes and Harpacticoid copepods reached minimum values; (ii) oligohaline and mesohaline sections, where the total density was low and diversity was poor; and (iii) polyhaline and euhaline sections, where both total density and diversity reached the highest values. The similar spatial distribution of meiobenthos assemblages in both estuaries suggests that natural stressors may be the major factors controlling the physicochemical conditions that determine meiobenthos community patterns. The mesoscale variability of subtidal meiobenthos density and composition within estuaries (in the order of kilometres) seems to be more important than the variability between estuaries (at the scale of hundreds of kilometres), a common feature in intertidal systems. From the management point of view, these results, based on higher taxa resolution, represent an obvious constraint to the applicability of ecological quality evaluation tools

Benthic nematode biodiversity of the Abzu, Tiamat and Michael Ivanov mud volcanoes located along the SWIM fracture zone (Gulf of Cadiz)

Studies that focus on meiofaunal assemblages of deep-sea mud volcanoes show an unpredictable abundance and diversity in a clear response to the different environmental conditions of the seeped sediment. The mud volcanoes Abzu, Tiamat and M. Ivanov (ATI), are located along the SWIM1 fracture zone, in front of the accretionary wedge of the Gulf of Cadiz (AWGC). The geological setting and the fluid geo- chemical characteristics of the ATI mud volcanoes are differ- ent from those located within the AWGC. The main aim of this study is to describe and compare the spatial and vertical distributions of the meiofauna and nematode assemblage s from the ATI mud volcanoes, the Porto mud volcano located in the AWGC, and a non-seep site (Site 2) as reference. The pore-water on the uppermost sediment layers has composi- tions close to the near-bottom seawater. The meiofauna abun- dances were generally lower and the vertical distribution of the assemblages showed a typical pattern, gradually decreas- ing towards depth. The lack of spatial patterns of the standing stocks contrasts with the spatial variability of diversity and biomass, related to the differences in the nematode assem- blages that are distinct between ATI, Site 2 and the Porto mud volcano. The ATI and Site 2 assemblages are similar to deep-sea non-seep habitats, and are clearly coupled with the environmental conditions of the bottom seawater. No evi- dence of seep conditions favouring the development of specialised fauna were found. The lower diversity and the presence of higher dominance species could be driven by dis- tinct seepage conditions of the Porto mud volcano

Spatial patterns of subtidal nematodes and macrofauna assemblages along the estuarine gradient to assess benthic condition: Definition of homogenous sectors along a naturally stressed estuary (Portugal).

In transitional waters the definition of reference conditions must take into account the natural variability. Therefore, prior to the use of environmental quality assessment tools the estuarine stretches reflecting different physical-chemical and biological conditions should be defined in order to correctly establish the benthic specific reference conditions. The main goal of this study is the definition of homogeneous sectors along a naturally stressed estuary by: analysis of the structure and composition and diversity of nematodes and macrobenthos spatial distribution patterns along the estuarine gradients; and comparison of the environmental patterns change with the biodiversity trends. The subtidal assemblages (meio- and macrofauna) of the Mira estuary (considered a undisturbed system) were sample in the summer of 2006 and several environmental factors were determined. The environmental factors salinity and the particle size reflect an estuarine gradient. The Nematode and macrobenthos densities and assemblages composition change along the gradient, establishing homogenous sections: (i) the tidal and oligohaline sections are characterised by the presence of freshwater nematodes, the total densities and diversity reach the minimum values; macrobenthos is dominated by Gammarus, Chironomidae and Corbicula fluminae;(ii) in the mesohaline sections the nematode densities is lower and the diversity is poor, the dominant genera are Terschellingia and Sabatieira, Daptonema and Anoplostoma; macrobenthos is dominated by Corophium orientale, Leptocheirus pilosus and Ciathura carinata; (iii) in the polyhaline and euhaline sections the total densities and the diversity are higher, and the Nematode dominant genera are Paracomesoma and Synonchiella; the macrobenthic Heteromastus filiformes, C. orientale and Hediste diversicole are present in the polyhaline section While in the euhaline section the species Nephtys hombergii and Maldanidae are exclusive

Contact-line friction of liquid drops on self-assembled monolayers: Chain-length effects

The static and dynamic wetting properties of self-assembled alkanethiol monolayers of increasing chain length were studied. The molecular-kinetic theory of wetting was used to interpret the dynamic contact angle data and evaluate the contact-line friction on the microscopic scale. Although the surfaces had a similar static wettability, the coefficient of contact-line friction Cζ0increased linearly with alkyl chain length. This result supports the hypothesis of energy dissipation due to a local deformation of the nanometer-thick layer at the contact line. © 2007 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe