Posts Tagged 'zooplankton'

Is the chemical composition of biomass the agent by which ocean acidification influences on zooplankton ecology?

Climate change impacts prevail on marine pelagic systems and food webs, including zooplankton, the key link between primary producers and fish. Several metabolic, physiological, and ecological responses of zooplankton species and communities to global stressors have recently been tested, with an emerging field in assessing effects of combined climate-related factors. Yet, integrative studies are needed to understand how ocean acidification interacts with global warming, mediating zooplankton body chemistry and ecology. Here, we tested the combined effects of global warming and ocean acidification, predicted for the year 2100, on a community of calanoid copepods, a ubiquitously important mesozooplankton compartment. Warming combined with tested pCO2 increase affected metabolism, altered stable isotope composition and fatty acid contents, and reduced zooplankton fitness, leading to lower copepodite abundances and decreased body sizes, and ultimately reduced survival. These interactive effects of temperature and acidification indicate that metabolism-driven chemical responses may be the underlying correlates of ecological effects observed in zooplankton communities, and highlight the importance of testing combined stressors with a regression approach when identifying possible effects on higher trophic levels.

Continue reading ‘Is the chemical composition of biomass the agent by which ocean acidification influences on zooplankton ecology?’

Species composition of microzooplankton Tintinnid from the coastal waters of Digha, Bay of Bengal

Tintinnid species distribution and hydrography were studied in the coastal waters of Digha during winter (November 2015) and summer (March 2016) seasons. Surface water samples were collected from 11 different stations from 0 to 10 km offshore with the help of a mechanized trawler. Parameters like tintinnid species enumeration, zooplankton biomass, phytoplankton concentration (total chlorophyll) and abundance, sea surface temperature (SST), pH, transparency, salinity, dissolved oxygen (DO), total phosphate, silicate and nitrate were analysed. A total of 20 different tintinnid species (16 agglomerated +4 non-agglomerated) belonging to 6 genera were recorded from the study area with seasonal variation in tintinnid diversity, i.e. higher in summer (total 2745 individual/l) compared to winter (total 1191 individual/l). Tintinnopsis was the most dominant genus during both the seasons, i.e. 2100 individual/l in summer and 727 individual/l in winter, contributing about 76 and 61% population for the respective seasons. The correlation between species and water quality parameters showed that Tintinnopsis sp. abundance was significantly regulated by nitrate concentration, salinity, dissolved oxygen, water transparency and pH. However, the mentioned hydrological parameters were not the only factors regulating the tintinnid abundance. Tintinnid abundance was also found to be positively related with transparency (r = 0.732) and salinity (r = 0.524) and moderately related with dissolved oxygen (r = 0.488) whereas strong negative relation (at p ≤ 0.05) was established between tintinnid abundance with nitrate (r = −0.681) and pH (r = −0.561). Bray-Curtis cluster analysis of tintinnid species showed more than 60% similarity. Shannon’s diversity index (H′), Simpson’s evenness index (D) and Margalef’s species richness index were found to be higher in summer, i.e. 1.61, 0.729 and 1.612, compared to the winter season, i.e. 1.139, 0.597 and 1.268. k-dominance curve showed maximum abundance of Tintinnopsis baltica in winter and Tintinnopsis gracilis in summer. Principal component analysis (PCA) was analysed to find out the environmental variables affecting different tintinnid species diversity. A significant spatiotemporal variation in Tintinnid population distribution was observed from two-way ANOVA. The results reflect significant seasonal (F = 840.0), spatial (F = 47.3) and interactive variation (F = 71.2) among the ciliate microzooplankton at n = 66, p ≤ 0.001. High chlorophyll content and phytoplankton population in summer indicated that tintinnid diversity in the season was positively influenced by producer community in coastal waters of Digha.

Continue reading ‘Species composition of microzooplankton Tintinnid from the coastal waters of Digha, Bay of Bengal’

Pontellid copepods, Labidocera spp., affected by ocean acidification: A field study at natural CO2 seeps

CO2 seeps in coral reefs were used as natural laboratories to study the impacts of ocean acidification on the pontellid copepod, Labidocera spp. Pontellid abundances were reduced by ∼70% under high-CO2 conditions. Biological parameters and substratum preferences of the copepods were explored to determine the underlying causes of such reduced abundances. Stage- and sex-specific copepod lengths, feeding ability, and egg development were unaffected by ocean acidification, thus changes in these physiological parameters were not the driving factor for reduced abundances under high-CO2 exposure. Labidocera spp. are demersal copepods, hence they live amongst reef substrata during the day and emerge into the water column at night. Deployments of emergence traps showed that their preferred reef substrata at control sites were coral rubble, macro algae, and turf algae. However, under high-CO2 conditions they no longer had an association with any specific substrata. Results from this study indicate that even though the biology of a copepod might be unaffected by high-CO2, Labidocera spp. are highly vulnerable to ocean acidification.

Continue reading ‘Pontellid copepods, Labidocera spp., affected by ocean acidification: A field study at natural CO2 seeps’

The future for microplankton in the Baltic Sea – Effects of SWS and climate change

The Baltic Sea is located between 53°N to 66°N and from 10°E to 30°E and is the second largest brackish water body in the world. It consists of several basins where the Baltic Proper is the major water mass. Around 85 million people live in the catchment area of the Baltic Sea, which subjects it to a range of environmental pressures, such as increased nutrient inputs from human activities (eutrophication), shipping, over-fishing, acid rain and trace metals released from anti-fouling paint. All these stressors, combined with low alkalinity, variable salinity and limited water exchange, makes the Baltic Sea a very sensitive area that may be less resilient to future stressors such as climate change or increased shipping activities. Microplankton communities consist of small heterotrophic bacteria, picoplankton, phytoplankton, cyanobacteria and smaller grazers, such as ciliates and zooplankton. In the Baltic Proper, there is a succession of blooms, within the microplankton community, from diatoms and dinoflagellates in the early spring to cyanobacteria during summer and ending with a second diatom and dinoflagellate bloom in the autumn. The cyanobacteria of the Baltic Proper bloom every summer and are dominated by Aphanizomenon sp. and Nodularia spumigena. Dolichospermum spp. is present but is less abundant. The effects of climate change were tested on a natural microplankton community, as well as on isolated cyanobacteria species from the Baltic Sea. To simulate effects of climate change, the temperature was increased from 12°C to 16°C, salinity decreased from 6-7 to 3-4 and atmospheric pCO2-levels was increased from 380 ppm to 960 ppm. The biovolume of Aphanizomenon sp. and N. spumigena increased when temperature was increased by 4°C. When salinity was decreased by three units, both the growth and photosynthetic activity of N. spumigena were reduced while Aphanizomenon sp. was unaffected, and the growth of Dolichospermum sp. was increased. Furthermore, present-day salinities were beneficial, in terms of increased biovolumes, of diatoms, dinoflagellates and ciliates, compared to reduced future salinity. Increased atmospheric pCO2 had no effect on any of the species in the microplankton community. These results show that the future microplankton community may be positive, in terms of increased biovolume, for the cyanobacteria species Aphanizomenon sp. and Dolichospermum spp. An increase of cyanobacteria blooms may open up to the possibility to grow and/or harvest these species as a source of biofuel or fatty acids (FA). Dolichospermum sp. yielded higher total FA content per biovolume, compared to the other two cyanobacteria species in phosphorus-depleted medium and Aphanizomenon sp. in nitrogen-depleted medium. Natural nutrient levels in the Baltic Proper are low both in nitrogen and phosphorus, which indicates a possible future market for biofuel and FA technologies. Additionally, the effects of seawater scrubbing (SWS) were tested on a natural summer-bloom microplankton community. Three different concentrations of scrubber water were added; 1%, 3% and 10%. To elucidate effects of decreased pH alone, water acidified with H2SO4 was added in equal concentrations. The six treatments were compared to a control without acidifying substances. SWS or the corresponding pH treatments, did not have a direct effect on microplankton species composition and biovolume. However, the increased amount of Cu and Zn in the scrubber water, combined with significant decrease in pH and alkalinity already at the 1% scrubber water treatment calls for precaution when implementing scrubber units on the shipping fleet of the Baltic Sea. The accumulated effects of long-term repeated addition constantly throughout the year, i.e. in a shipping lane, are yet to be elucidated.

Continue reading ‘The future for microplankton in the Baltic Sea – Effects of SWS and climate change’

Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure

Previously, we found that ocean acidification (OA) mitigates mercury (Hg) toxicity to marine copepod Tigriopus japonicus under multigenerational exposure (four generations, F0-F3). To determine the response mechanisms of T. japonicus against long-term exposure to OA and Hg pollution, we investigated the proteome of F3 copepods after multigenerational exposure to four conditions: pCO2 400 μatm + control; pCO2 1000 μatm + control; pCO2 400 μatm + 1.0 µg/L Hg; and pCO2 1000 μatm + 1.0 µg/L Hg. Functional enrichment analysis indicated that OA enhanced the copepod’s energy production mainly by increasing protein assimilation and proteolysis as a compensatory strategy, which explained its physiological resilience to reduced pH. Conversely, Hg treatment decreased many critical processes, including ferric iron binding, antioxidant activity, cellular homeostasis, and glutathione metabolism, and these toxic events could translate into higher-level responses, i.e., restrained reproduction in copepods. Importantly, the mediation of Hg toxicity in T. japonicus by OA could be explained by the enhanced lysosome-autophagy pathway proteomes that are responsible for repairing/removing damaged proteins/enzymes under stress. Overall, this study provided molecular insights into the response of T. japonicus to long-term exposure of OA and Hg, with a particular emphasis on the mitigating impact of CO2-driven acidification on Hg toxicity.

Continue reading ‘Global proteome profiling of a marine copepod and the mitigating effect of ocean acidification on mercury toxicity after multigenerational exposure’

Ocean acidification effects on mesozooplankton community development: Results from a long-term mesocosm experiment

Ocean acidification may affect zooplankton directly by decreasing in pH, as well as indirectly via trophic pathways, where changes in carbon availability or pH effects on primary producers may cascade up the food web thereby altering ecosystem functioning and community composition. Here, we present results from a mesocosm experiment carried out during 113 days in the Gullmar Fjord, Skagerrak coast of Sweden, studying plankton responses to predicted end-of-century pCO2 levels. We did not observe any pCO2 effect on the diversity of the mesozooplankton community, but a positive pCO2 effect on the total mesozooplankton abundance. Furthermore, we observed species-specific sensitivities to pCO2 in the two major groups in this experiment, copepods and hydromedusae. Also stage-specific pCO2 sensitivities were detected in copepods, with copepodites being the most responsive stage. Focusing on the most abundant species, Pseudocalanus acuspes, we observed that copepodites were significantly more abundant in the high-pCO2 treatment during most of the experiment, probably fuelled by phytoplankton community responses to high-pCO2 conditions. Physiological and reproductive output was analysed on P. acuspes females through two additional laboratory experiments, showing no pCO2 effect on females’ condition nor on egg hatching. Overall, our results suggest that the Gullmar Fjord mesozooplankton community structure is not expected to change much under realistic end-of-century OA scenarios as used here. However, the positive pCO2 effect detected on mesozooplankton abundance could potentially affect biomass transfer to higher trophic levels in the future.

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A combination of salinity and pH affects the recruitment of Gladioferens pectinatus (Brady) (Copepoda; Calanoida)

Carbon dioxide levels in many estuaries fluctuate and, in several cases, reach extremes much higher than those predicted for oceans by the end of the century. Moreover, estuaries are characterized by natural fluctuations in salinity, and reduced pH, from increased pCO2, exposes estuarine organisms to multiple stresses. Although the effects of low pH on the reproduction of several marine copepod species have been assessed, studies examining effects of pH in estuarine copepod species are extremely scarce. Here, we aim at understanding the reproductive response of Gladioferens pectinatus to the stress posed by both salinity and pH. G. pectinatus was exposed to salinities 2 and 10, at four different pH levels each. Our results show no impairment in the brood size, embryonic development time and hatching success under low pH levels at either salinities. However, at salinity 2, the percentage of nauplii growing into adults significantly decreased at low pH, whereas at salinity 10, no major effect was observed. We argue that the combination of osmoregulation and acidity induced stress response can affect the development of nauplii and copepodites, as well as adult recruitment, likely due to energy reallocation and molting impairment. We also argue that resilience and phenotypic plasticity highly influence the ability of different copepod species and populations to reproduce and grow under stressful combinations of environmental parameters. This study points out the importance of understanding the effects of multiple stresses or parameters on the adaptability of organisms to water acidification.

Continue reading ‘A combination of salinity and pH affects the recruitment of Gladioferens pectinatus (Brady) (Copepoda; Calanoida)’

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Ocean acidification in the IPCC AR5 WG II

OUP book