Posts Tagged 'nematodes'

Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico

In this study, we analyse the horizontal and vertical distribution of the meiofauna in the Wagner and Consag basins. Samples were collected at soft bottom sites on board of the R/V “El Puma” (WAGNER-02 Expedition) during July- August 2010 with a Smith McIntyre grab and 10 cm cores. At each station physical and chemical variables were measured including depth, salinity, pore water temperature and pH. Twelve higher taxa of meiofauna were recorded in both basins. Meiofauna was dominated by Nematoda (73.1%) followed by Copepoda Harpacticoida (11.28%), Polychaeta (8.41%) and Kinorhyncha (4.71%). Density of meiofauna in these two basins ranked from 19.12 to 742.20 ind.10 cm-2 and were mainly concentrated in the first four centimeters of the sediment (78.6%) and decreased with sediment depth; PERMANOVA analysis show significant differences among sediment depth layers. However, PERMANOVA analysis did not show significant differences of the abundances of meiofauna between basins. Multivariate Correspondence Canonica l Analysis (MCCA) was performed but the assemblages identified had no spatial gradient. This only confirms the patchy distribution already reported for the meiofauna. This analysis reported two faunal groups: Nematoda -Polychaeta and Copepoda – Kinorhyncha. In the present study, we report for the first time the horizontal and vertical distribution of the meiofauna in a natural CO2 venting area in the Gulf of California. There is still so much that we do not know about meiofauna processes, more studies are needed specially down to species level in order to have a clearer view of how environmental factors affect each species spatial distribution.

Continue reading ‘Composition and spatial distribution of the meiofauna in the Wagner and Consag basins, Gulf of California, Mexico’

Impact of ocean acidification on the biogeochemistry and meiofaunal assemblage of carbonate-rich sediments: results from core incubations (Bay of Villefranche, NW Mediterranean Sea)


• A sediment incubation experiment to assess the effect of ocean acidification
• Porewater concentration gradients and sediment-water fluxes (DIC, TA, pH, Ca2+, O2)
• Ocean acidification impacts early diagenesis in carbonate-rich sediments.
• CaCO3 dissolution and the TA release may increase the buffering capacity of bottom water.


Marine sediments are an important carbonate reservoir whose partial dissolution could buffer seawater pH decreases in the water column as a consequence of anthropogenic CO2 uptake by the ocean. This study investigates the impact of ocean acidification on the carbonate chemistry at the sediment-water interface (SWI) of shallow-water carbonate sediments. Twelve sediment cores were sampled at one station in the Bay of Villefranche (NW Mediterranean Sea). Four sediment cores were immediately analyzed in order to determine the initial distribution (T0) of dissolved inorganic carbon (DIC), total alkalinity (TA), pH and dissolved oxygen (O2) in the porewaters and to quantify sediment-water fluxes. Four other cores were kept submerged in the laboratory for 25 days with ambient seawater (pHT = 8.12) and the remaining four cores were incubated with acidified seawater (average pH offset of −0.68). This acidification experiment was carried out in an open-flow system, in the dark and at in-situ temperature (15 °C). Every three days, sediment-water fluxes (DIC, TA, pH, O2 and nutrients) were determined using a whole core 12-h incubation technique. Additionally, vertical O2 and pH microprofiles were regularly recorded in the first 2 cm of the sediment during the entire experiment. At the end of the experiment, TA, DIC and Ca2+ concentrations were analyzed in the porewaters and the abundance and taxonomic composition of meiofaunal organisms were assessed. The saturation states of the porewaters with respect to calcite and aragonite were over-saturated but under-saturated with respect to 12 mol% Mg-calcite, in both acidified and non-acidified treatments. The sediment-water fluxes of TA and DIC increased in the acidified treatment, likely as a consequence of enhanced carbonate dissolution. In contrast, the acidification of the overlying water did not significantly affect the O2 and nutrients fluxes at the SWI. Meiofaunal abundance decreased in both treatments over the duration of the experiment, but the organisms seemed unaffected by the acidification. Our results demonstrate that carbonate dissolution increased under acidified conditions but other parameters, such as microbial redox processes, were apparently not affected by the pH decrease, at least during the duration of our experiment. The dissolution of sedimentary carbonates and the associated release of TA may potentially buffer bottom water, depending on the intensity of the TA flux, the TA/DIC ratio, vertical mixing and, therefore, the residence time of bottom water. Under certain conditions, this process may mitigate the effect of ocean acidification on benthic ecosystems.

Continue reading ‘Impact of ocean acidification on the biogeochemistry and meiofaunal assemblage of carbonate-rich sediments: results from core incubations (Bay of Villefranche, NW Mediterranean Sea)’

Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage

In future global change scenarios the surface ocean will experience continuous acidification and rising temperatures. While effects of both stressors on marine, benthic communities are fairly well studied, consequences of the interaction of both factors remain largely unknown. We performed a short-term microcosm experiment exposing a soft-bottom community from an intertidal flat in the Westerscheldt estuary to two levels of seawater pH (ambient pHT = 7.9, reduced pHT = 7.5) and temperature (10 °C ambient and 13 °C elevated temperature) in a crossed design. After 8 weeks, meiobenthic community structure and nematode staining ratios, as a proxy for mortality, were compared between treatments and structural changes were related to the prevailing abiotic conditions in the respective treatments (pore water pHT, sediment grain size, total organic matter content, total organic carbon and nitrogen content, phytopigment concentrations and carbonate concentration). Pore water pHT profiles were significantly altered by pH and temperature manipulations and the combination of elevated temperature and reduced pH intensified the already more acidic porewater below the oxic zone. Meiofauna community composition was significantly affected by the combination of reduced pH and elevated temperature resulting in increased densities of predatory Platyhelminthes, reduced densities of Copepoda and Nauplii and complete absence of Gastrotricha compared to the experimental control. Furthermore, nematode staining ratio was elevated when seawater pH was reduced pointing towards reduced degradation rates of dead nematode bodies. The observed synergistic interactions of pH and temperature on meiobenthic communities and abiotic sediment characteristics underline the importance of multistressor experiments when addressing impacts of global change on the marine environment.

Continue reading ‘Combined, short-term exposure to reduced seawater pH and elevated temperature induces community shifts in an intertidal meiobenthic assemblage’

The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages


  • Higher seawater temperature did not effect meiofaunal abundance.
  • Lower seawater pH did reduce meiofaunal abundance and species richness.
  • Nematode assemblages showed increased dominance under a future OW/OA scenario.


Climate change due to increased anthropogenic CO2 in the atmosphere is causing an increase in seawater temperatures referred to as ocean warming and a decrease in seawater pH, referred to as ocean acidification. The meiofauna play an important role in the ecology of marine ecosystems and the functions they provide. Using microcosms, meiofaunal assemblages were exposed to two temperatures (15 and 19 °C) and two pHs (pCO2 of 400 and 1000 ppm), both individually and in combination, for a period of 90 days. The hypothesis that increased temperature will increase meiofaunal abundance was not supported. The hypothesis that a reduced pH will reduce meiofaunal abundance and species richness was supported. The combination of future conditions of temperature and pH (19 °C and pCO2 of 1000 ppm) did not affect overall abundance but the structure of the nematode assemblage changed becoming dominated by a few opportunistic species.

Continue reading ‘The combined effects of ocean warming and acidification on shallow-water meiofaunal assemblages’

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 CO2concentration 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.

Continue reading ‘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’

Impact of predicted climate change scenarios on a coral reef meiofauna community

Changes in marine communities in response to elevated CO2 have been reported but information on how representatives of the benthic lower trophic levels will be impacted remains scarce. A laboratory experiment was conducted to evaluate the impact of different climate change scenarios on a coral reef meiofauna community. Samples of the meiofauna community were collected from the coral reef subtidal zone of Serrambi beach (Ipojuca, Pernambuco, Brazil), using artificial substrate units. The units were exposed to control treatments and to three climate change scenarios, and collected after 15 and 29 d. Important changes in the meiofauna community structure were observed after 15 d of exposure. The major meiofauna groups exhibited divergent responses to the various scenarios. Although polychaetes were negatively affected after 29 d in the most severe scenario (Scenario III), harpacticoid copepods were negatively affected in Scenarios II and III after 15 and 29 d. Harpacticoid nauplii were strongly and negatively affected in all scenarios. In contrast, Nematoda exhibited higher densities in all scenarios. To the best of our knowledge, this community-based study was the first to observe how meiofauna organisms from a coral reef environment react to the synergetic effects of reductions in seawater pH and increased temperature.

Continue reading ‘Impact of predicted climate change scenarios on a coral reef meiofauna community’

Simulated leakage of high pCO2 water negatively impacts bivalve dominated infaunal communities from the Western Baltic Sea

Carbon capture and storage is promoted as a mitigation method counteracting the increase of atmospheric CO2 levels. However, at this stage, environmental consequences of potential CO2 leakage from sub-seabed storage sites are still largely unknown. In a 3-month-long mesocosm experiment, this study assessed the impact of elevated pCO2 levels (1,500 to 24,400 μatm) on Cerastoderma edule dominated benthic communities from the Baltic Sea. Mortality of C. edule was significantly increased in the highest treatment (24,400 μatm) and exceeded 50%. Furthermore, mortality of small size classes (0–1 cm) was significantly increased in treatment levels ≥6,600 μatm. First signs of external shell dissolution became visible at ≥1,500 μatm, holes were observed at >6,600 μatm. C. edule body condition decreased significantly at all treatment levels (1,500–24,400 μatm). Dominant meiofauna taxa remained unaffected in abundance. Densities of calcifying meiofauna taxa (i.e. Gastropoda and Ostracoda) decreased in high CO2 treatments (>6,600 μatm), while the non – calcifying Gastrotricha significantly increased in abundance at 24,400 μatm. In addition, microbial community composition was altered at the highest pCO2 level. We conclude that strong CO2 leakage can alter benthic infauna community composition at multiple trophic levels, likely due to high mortality of the dominant macrofauna species C. edule.

Continue reading ‘Simulated leakage of high pCO2 water negatively impacts bivalve dominated infaunal communities from the Western Baltic Sea’

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Ocean acidification in the IPCC AR5 WG II

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