Short-term CO\u3csub\u3e2\u3c/sub\u3e exposure and temperature rise effects on metazoan meiofauna and free-living nematodes in sandy and muddy sediments: Results from a flume experiment

© 2017 Elsevier B.V. Global concern over increasing CO2 emissions, and the resultant CO2 driven temperature rises and changes in seawater chemistry, necessitates the advancement of understanding into how these changes will affect marine life now and in the future. Here we report on an experimental investigation into the effects of increased CO2 concentration and elevated temperature on sedimentary meiofaunal communities. Cohesive (muddy) and non-cohesive (sandy) sediments were collected from the Eden Estuary in St. Andrews, Scotland, UK, placed within a flume setup and exposed to 2 levels of CO2 concentration (380 and 750 ppmv, current at the time of the experiment, and predicted CO2 concentration by 2100, respectively) and 2 temperature levels (12 °C and 16 °C, current in-situ and predicted temperature by 2100, respectively). We investigated the metazoan meiofauna and nematode communities before and after 28 days of exposure under these experimental conditions. The most determinative factor for abundance, diversity and community structure of meiofauna and nematodes was sediment type: on all levels, communities were significantly different between sand and mud sediments which agrees with what is generally known about the influence of sediment structure on meiofaunal organisms. Few CO2 and temperature effects were observed, suggesting that meiofauna and nematodes are generally much less responsive than, for instance, microbial communities and macrofauna to these environmental changes in estuarine environments, where organisms are naturally exposed to a fluctuating environment. This was corroborated by the observed effects related to the different seasons in which the samples were taken from the field to run the experiment. After 28 days, meiofauna and nematode communities in muddy sediments showed a greater response to increased CO2 concentration and temperature rise than in sandy sediments. However, further study is needed to investigate the underlying mechanisms and meiofauna species-specific resilience and responses to ocean acidification and warming, and their interactions with other biota, to understand what such changes may mean for meiofauna communities and the ecosystem processes and functions they contribute to

Short-term CO₂ exposure and temperature rise effects on metazoan meiofauna and free-living nematodes in sandy and muddy sediments: Results from a flume experiment

Global concern over increasing CO2 emissions, and the resultant CO2 driven temperature rises and changes in seawater chemistry, necessitates the advancement of understanding into how these changes will affect marine life now and in the future. Here we report on an experimental investigation into the effects of increased CO2 concentration and elevated temperature on sedimentary meiofaunal communities. Cohesive (muddy) and non-cohesive (sandy) sediments were collected from the Eden Estuary in St. Andrews, Scotland, UK, placed within a flume setup and exposed to 2 levels of CO2 concentration (380 and 750 ppmv, current at the time of the experiment, and predicted CO2 concentration by 2100, respectively) and 2 temperature levels (12 °C and 16 °C, current in-situ and predicted temperature by 2100, respectively). We investigated the metazoan meiofauna and nematode communities before and after 28 days of exposure under these experimental conditions. The most determinative factor for abundance, diversity and community structure of meiofauna and nematodes was sediment type: on all levels, communities were significantly different between sand and mud sediments which agrees with what is generally known about the influence of sediment structure on meiofaunal organisms. Few CO2 and temperature effects were observed, suggesting that meiofauna and nematodes are generally much less responsive than, for instance, microbial communities and macrofauna to these environmental changes in estuarine environments, where organisms are naturally exposed to a fluctuating environment. This was corroborated by the observed effects related to the different seasons in which the samples were taken from the field to run the experiment. After 28 days, meiofauna and nematode communities in muddy sediments showed a greater response to increased CO2 concentration and temperature rise than in sandy sediments. However, further study is needed to investigate the underlying mechanisms and meiofauna species-specific resilience and responses to ocean acidification and warming, and their interactions with other biota, to understand what such changes may mean for meiofauna communities and the ecosystem processes and functions they contribute to

Seaweed-based products from Ecklonia maxima and Ascophyllum nodosum as control agents for the root-knot nematodes Meloidogyne chitwoodi and Meloidogyne hapla on tomato plants

Two commercially available seaweed products, derived from Ascophyllum nodosum (An) and Ecklonia maxima (Em), were evaluated for their potential as control agents for the root-knot nematodes, Meloidogyne chitwoodi and Meloidogyne hapla. The effects of both products on hatching, host location and penetration by second-stage juveniles (J2) were examined. Continuous exposure of M. chitwoodi egg masses to 50 and 100 % An significantly reduced the final percentage hatch, but this result could not be confirmed. In a bioassay with pluronic gel, more J2 of M. chitwoodi and M. hapla were found within the 0.5-cm vicinity of a tomato root tip after 24- and 6-h pre-exposures to Em, respectively. On agar plates, J2 of M. chitwoodi pre-exposed to An or Em showed less attraction to tomato root diffusate compared with distilled water (DW). Moreover, J2 pre-exposed to An lost the ability to differentiate repellent and attractant solutions on agar plates, unlike J2 pre-exposed to Em or DW. A 24-h pre-exposure to An reduced the infectivity of M. chitwoodi and M. hapla, whereas pre-exposure to Em enhanced the infectivity of M. chitwoodi. In a glasshouse pot experiment, treatments with Em reduced M. hapla multiplication on tomato. For M. chitwoodi, no effect on the number of nematodes per gram root was seen. The root biomass significantly reduced for untreated plants infested with M. chitwoodi compared to Em- and An-treated plants. The results indicate that these seaweed products adversely affect hatching and sensory perception in in vitro assays, but assumptions about in vivo effects may be unwise as dilutions of the products when applied as soil drenches may compromise activity

Verônica da Fonsêca-Genevois and the rise of meiofauna studies in Brazil: life and contribution of a pioneer, in memoriam

The Head of the Brazilian Meiofauna Laboratory at the Federal University of Pernambuco (UFPE), Prof. Dra. Vernica Gomes da Fonsca-Genevois, passed away on Monday, 2 December 2013, after a long illness. Veronica studied meiofauna since the 1980s. In the last two decades, she focused mostly on nematode ecology and taxonomy, with a special interest in the unexplored deep-sea diversity of the Brazilian coast. Having been the promoter of over 50 Brazilian students on meiofauna-related subjects, and having sent many students abroad for expert training in Europe and the US, she was not only the pioneer of meiofaunal research in Brazil, but also the main driving force behind the impressive expansion of meiofaunal research in Brazil in the last 10 years. Vernica da Fonsca-Genevois was one of the first Brazilian benthologists to promote lasting collaborations with European institutes such as Ghent University and Plymouth Marine Laboratory. We will remember her as a magnificent colleague and an eminent and inspiring scientist with a tremendous knowledge of, and passion for, marine meiofauna

Daily Temperature Fluctuations Alter Interactions between Closely Related Species of Marine Nematodes.

In addition to an increase in mean temperature, climate change models predict decreasing amplitudes of daily temperature fluctuations. In temperate regions, where daily and seasonal fluctuations are prominent, such decreases in daily temperature fluctuations can have a pronounced effect on the fitness of species and on the outcome of species interactions. In this study, the effect of a temperature regime with daily fluctuations versus a constant temperature on the fitness and interspecific interactions of three cryptic species of the marine nematode species complex of Litoditis marina (Pm I, Pm III and Pm IV) were investigated. In a lab experiment, different combinations of species (monospecific treatment: Pm I and Pm IV and Pm III alone; two-species treatment: Pm I + Pm IV; three-species treatment: Pm I + Pm IV + Pm III) were subjected to two different temperature regimes: one constant and one fluctuating temperature. Our results showed that fluctuating temperature had minor or no effects on the population fitness of the three species in monocultures. In contrast, interspecific interactions clearly influenced the fitness of all three species, both positively and negatively. Temperature regime did have a substantial effect on the interactions between the species. In the two-species treatment, temperature regime altered the interaction from a sort of mutualism to commensalism. In addition, the strength of the interspecific interactions changed depending on the temperature regime in the three-species treatment. This experiment confirms that interactions between the species can change depending on the abiotic environment; these results show that it is important to incorporate the effect of fluctuations on interspecific interactions to predict the effect of climate change on biodiversity

Testing Bathymetric and Regional Patterns in the Southwest Atlantic Deep Sea Using Infaunal Diversity, Structure, and Function

A better understanding of deep-sea biology requires knowledge of the structure and function of their communities, the spatial, temporal, and environmental patterns, and the changes and dynamics that govern them. Some of the most studied patterns in deep-sea biology are those related to bathymetrical gradients. For meiofauna and nematodes, such studies have highlighted the importance of recognizing regional differences in using ecological mechanisms to explain those patterns. Despite holding significant fisheries and oil and gas resources, the eastern Brazilian Continental Margin is poorly understood with respect to its seafloor biology and ecology. To answer ecological questions of deep-sea infaunal structural and functional diversity in relation to bathymetrical patterns, we used nematode data from five bathymetric transects (400, 1000, 1900, 2500, and 3000 m water depth) sampled in 2011 and 2013 on the Espírito Santo slope off the coast of southeast (SE) Brazil. Deep nematode community analysis based on 6763 nematode identifications showed very high levels of diversity (201 genera; 43 families) compared to other ocean basins and deep-sea regions. Our analyses showed that there is a distinct bathymetric break in standing stocks and community structure between 1000 and 1900 m. Nematode standing stocks were much higher at 400 and 1000 m compared to those for similar depths worldwide, likely linked to the intense and frequent upwelling and specific hydrographic and topographic identity of the region. The bathymetric break was not present for structural and functional nematode diversity. Instead, bathymetric regressions showed that they increased gradually toward 3000 m water depth. The deep Espírito Santo basin is characterized by rich and equitable nematode communities that are both mature and trophically diverse. General deep-sea ecological theories apply to our findings, but there are also substantial regional effects related to the local margin topography, upwelling, and oceanographic and hydrodynamic processes that make the Espírito Santo Basin a unique and diverse deep-sea ecosystem

Total number of nematodes (adults: a + b, juveniles: c + d) over time in the different temperature treatments (constant temperature: a + c, fluctuating temperature: b + d) with assemblage dynamics at the different sampling times (three pie charts correspond with following time moments: 7, 14 and 21 days): upper pie charts for the T treatment (Pm I, Pm IV and Pm III with interspecific interactions), lower pie charts are the dynamics in the FiT treatment (Pm I, Pm IV and Pm III without interspecific interactions).

<p>Total number of nematodes (adults: a + b, juveniles: c + d) over time in the different temperature treatments (constant temperature: a + c, fluctuating temperature: b + d) with assemblage dynamics at the different sampling times (three pie charts correspond with following time moments: 7, 14 and 21 days): upper pie charts for the T treatment (Pm I, Pm IV and Pm III with interspecific interactions), lower pie charts are the dynamics in the FiT treatment (Pm I, Pm IV and Pm III without interspecific interactions).</p

Statistical results of the effect of temperature regime on assemblage dynamics.

<p>Results of the two 3-way PERMANOVA analyses on interspecific interactions (independent factors: temperature (constant vs. fluctuating), interspecific interactions (fictitious vs. real populations) and time), dependent factors: adult and juvenile assemblage compositions)) for experiments with two species (D vs. FiD) and three species (T vs. FiT). Level of confidence = 95%. Interspec.int. = interspecific interactions; temp. = temperature; p = statistical p value; F = F statistic.</p><p>Statistical results of the effect of temperature regime on assemblage dynamics.</p

Overview of the effect of the interspecific interactions on the fitness.

<p>Effect of interspecific interactions on population abundance (adults and juveniles) of the different cryptic species of <i>Litoditis marina</i> (Pm I, Pm III and Pm IV) in the D and T treatment compared with the M treatment (0 = statistically no differences;-: lower abundance compared with M; +: higher abundance compared with M).</p><p>*: At constant temperature a positive effect for Pm I adults occurred</p><p>a: at 14 days a negative effect occurred</p><p>b: at 21 days a negative effect occurred</p><p>c: at day 7 no difference was found</p><p>Overview of the effect of the interspecific interactions on the fitness.</p