Posts Tagged 'zooplankton'

Response of pelagic calcifiers (Foraminifera, Thecosomata) to ocean acidification during oligotrophic and simulated up-welling conditions in the subtropical North Atlantic off Gran Canaria

Planktonic Foraminifera and thecosome pteropods are major producers of calcite and aragonite in the ocean and play an important role for pelagic carbonate flux. The responses of planktonic foraminifers to ocean acidification (OA) are variable among the species tested and so far do not allow for reliable conclusion. Thecosome pteropods respond with reduced calcification and shell dissolution to OA and are considered at high risk especially at high latitudes. The present investigation was part of a large-scale in situ mesocosm experiment in the oligotrophic waters of the eastern subtropical North Atlantic. Over 62 days, we measured the abundance and vertical flux of pelagic foraminifers and thecosome pteropods as part of a natural plankton community over a range of OA scenarios. A bloom phase was initiated by the introduction of deep-water collected from approx. 650 m depth simulating a natural up-welling event. Foraminifers occurred throughout the entire experiment in both the water column and the sediment traps. Pteropods were present only in small numbers and disappeared after the first two weeks of the experiment. No significant CO2 related effects were observed for foraminifers, but cumulative sedimentary flux was reduced at the highest CO2 concentrations. This flux reduction was most likely accompanying an observed flux reduction of particulate organic matter (POM) so that less foraminifers were intercepted and transported downward.

Continue reading ‘Response of pelagic calcifiers (Foraminifera, Thecosomata) to ocean acidification during oligotrophic and simulated up-welling conditions in the subtropical North Atlantic off Gran Canaria’

Environmental controls on pteropod biogeography along the Western Antarctic Peninsula

Pteropods are abundant zooplankton in the Western Antarctic Peninsula (WAP) and important grazers of phytoplankton and prey for higher trophic levels. We analyzed long‐term (1993–2017) trends in summer (January–February) abundance of WAP pteropods in relation to environmental controls (sea ice, sea surface temperature, climate indices, phytoplankton biomass and productivity, and carbonate chemistry) and interspecies dynamics using general linear models. There was no overall directional trend in abundance of thecosomes, Limacina helicina antarctica and Clio pyramidata, throughout the entire WAP, although L. antarctica abundance increased in the slope region and C. pyramidata abundance increased in the South. High L. antarctica abundance was strongly tied to a negative Multivariate El Niño Southern Oscillation Index the previous year. C. pyramidata abundance was best explained by early sea ice retreat 1‐yr prior. Abundance of the gymnosome species, Clione antarctica and Spongiobranchaea australis, increased over the time series, particularly in the slope region. Gymnosome abundance was positively influenced by abundance of their prey, L. antarctica, during the same season, and late sea ice advance 2‐yr prior. These trends indicate a shorter ice season promotes longer periods of open water in spring/summer favoring all pteropod species. Weak relationships were found between pteropod abundance and carbonate chemistry, and no long‐term trend in carbonate parameters was detected. These factors indicate ocean acidification is not presently influencing WAP pteropod abundance. Pteropods are responsive to the considerable environmental variability on both temporal and spatial scales—key for predicting future effects of climate change on regional carbon cycling and plankton trophic interactions.

Continue reading ‘Environmental controls on pteropod biogeography along the Western Antarctic Peninsula’

Microzooplankton grazing responds to simulated ocean acidification indirectly through changes in prey cellular characteristics

Microzooplankton (MZP) grazing is a factor that regulates oceanic primary production and is a controlling mechanism for marine biogeochemical cycling. Despite the prominent ecological role of MZP, few studies have explored their responses to ocean acidification (OA). Studies to date generally indicate that MZP are affected indirectly by OA through changes in phytoplankton prey composition and biomass concentration. Here, we conducted a series of experiments testing whether OA-induced changes in cellular characteristics of individual prey species can cause changes in MZP grazing. Two tintinnid ciliates (Eutintinnus sp. and Schmidingerella sp.) and a heterotrophic dinoflagellate (Oxyrrhis marina) were offered phytoplankton prey (Emiliania huxleyi) cultured under 3 pCO2 concentrations. Using linear mixed effects models, we found that Eutintinnus sp. and O. marina exhibited a step-wise increase in ingestion rates on E. huxleyi cells cultured under elevated pCO2. Schmidingerella sp. ingestion showed a non-linear response, whereby cells cultured under high pCO2 were ingested at higher rates than cells from moderate pCO2. The percentages of all 3 MZP populations observed feeding were higher on E. huxleyi cells cultured under elevated pCO2, with Eutintinnus sp. showing a step-wise increase. We postulate that this response is caused by the observed increased coccosphere volume in E. huxleyi cells cultured under elevated pCO2. If changes in phytoplankton cell volume are widespread under OA, this could be an important mechanism by which MZP grazing behavior shifts and planktonic food web dynamics are altered in the future ocean.

Continue reading ‘Microzooplankton grazing responds to simulated ocean acidification indirectly through changes in prey cellular characteristics’

Projected amplification of food web bioaccumulation of MeHg and PCBs under climate change in the Northeastern Pacific

Climate change increases exposure and bioaccumulation of pollutants in marine organisms, posing substantial ecophysiological and ecotoxicological risks. Here, we applied a trophodynamic ecosystem model to examine the bioaccumulation of organic mercury (MeHg) and polychlorinated biphenyls (PCBs) in a Northeastern Pacific marine food web under climate change. We found largely heterogeneous sensitivity in climate-pollution impacts between chemicals and trophic groups. Concentration of MeHg and PCBs in top predators, including resident killer whales, is projected to be amplified by 8 and 3%, respectively, by 2100 under a high carbon emission scenario (Representative Concentration Pathway 8.5) relative to a no-climate change control scenario. However, the level of amplification increases with higher carbon emission scenario for MeHg, but decreases for PCBs. Such idiosyncratic responses are shaped by the differences in bioaccumulation pathways between MeHg and PCBs, and the modifications of food web dynamics between different levels of climate change. Climate-induced pollutant amplification in mid-trophic level predators (Chinook salmon) are projected to be higher (~10%) than killer whales. Overall, the predicted trophic magnification factor is ten-fold higher in MeHg than in PCBs under high CO2 emissions. This contribution highlights the importance of understanding the interactions with anthropogenic organic pollutants in assessing climate risks on marine ecosystems.

Continue reading ‘Projected amplification of food web bioaccumulation of MeHg and PCBs under climate change in the Northeastern Pacific’

A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod

Ocean acidification is the ongoing decrease in the pH of the oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere. Increased carbon dioxide (CO2) from the burning of fossil fuels and other human activities continues to affect our atmosphere, resulting in global warming and climate change. Less well known is that this carbon dioxide is altering the chemistry of the surface oceans and causing them to become more acidic. From scientists and marine resource managers to policy- and decision-makers, there is a growing concern that the process called ocean acidification could have significant consequences on marine organisms which may alter species composition, disrupt marine food webs and ecosystems and potentially damage fishing, tourism and other human activities connected to the seas.

Continue reading ‘A microcosm study on the impact of acidification on feeding, survival, nauplii production rate, post-embryonic development and nutritional composition of marine copepod’

Additive effects of pCO2 and temperature on respiration rates of the Antarctic pteropod Limacina helicina antarctica

The Antarctic pteropod, Limacina helicina antarctica, is a dominant member of the zooplankton in the Ross Sea and supports the vast diversity of marine megafauna that designates this region as an internationally protected area. Here, we observed the response of respiration rate to abiotic stressors associated with global change—environmentally relevant temperature treatments (−0.8°C, 4°C) and pH treatments reflecting current-day and future modeled extremes (8.2, 7.95 and 7.7 pH at −0.8°C; 8.11, 7.95 and 7.7 pH at 4°C). Sampling repeatedly over a 14-day period in laboratory experiments and using microplate respirometry techniques, we found that the metabolic rate of juvenile pteropods increased in response to low-pH exposure (pH 7.7) at −0.8°C, a near-ambient temperature. Similarly, metabolic rate increased when pteropods were exposed simultaneously to multiple stressors: lowered pH conditions (pH 7.7) and a high temperature (4°C). Overall, the results showed that pCO2 and temperature interact additively to affect metabolic rates in pteropods. Furthermore, we found that L. h. antarctica can tolerate acute exposure to temperatures far beyond its maximal habitat temperature. Overall, L. h. antarctica appears to be susceptible to pH and temperature stress, two abiotic stressors which are expected to be especially deleterious for ectothermic marine metazoans in polar seas.

Continue reading ‘Additive effects of pCO2 and temperature on respiration rates of the Antarctic pteropod Limacina helicina antarctica’

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’


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Ocean acidification in the IPCC AR5 WG II

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