Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors

On a daily basis, planktonic organisms migrate vertically and thus experience widely varying conditions in their physico-chemical environment. In the Gulf of Finland, these changes are larger than values predicted by climate change scenarios predicted for the next century (up to 0.5 units in pH and 5 degrees C in temperature). In this work, we are interested in how temporal variations in physico-chemical characteristics of the water column on a daily and weekly scale influence oxidative stress level and antioxidant responses in the planktonic copepod of the genus Acartia. Responses were determined from samples collected during a two-week field survey in the western Gulf of Finland, Baltic Sea. Our results showed that GST (Glutathione-S-transferase) enzyme activity increased in the surface waters between Weeks I and II, indicating antioxidant defense mechanism activation. This is most likely due to elevating temperature, pH, and dissolved oxygen observed between these two weeks. During Week II also GSSG (oxidized glutathione) was detected, indicating that copepods responded to stressor(s) in the environment. Our results suggest that Acartia copepods seem fairly tolerant to weekly fluctuations in environmental conditions in coastal and estuarine areas, in terms of antioxidant defense and oxidative stress. This could be directly connected to a very efficient glutathione cycling system acting as antioxidant defense system for neutralizing ROS and avoiding elevated levels of LPX

The Effect of Changing Environmental Conditions on the Reproduction Success of Copepod Acartia bifilosa

The objective of this thesis is to shed light on how climate-induced changes in the environmental conditions of the Baltic Sea, mainly pH and temperature, affect the reproduction success of copepods, specifically Acartia bifilosa. The possible changes in the egg production rate and hatching success of A. bifilosa due to climate change may affect the future plankton trophic dynamics in the Baltic Sea as it is the most abundant zooplankton species and a major food source for many species, for example Baltic herring. The research was carried out by gathering quantitative data in a laboratory experiment in Tvärminne Zoological Station, in Hanko, southern Finland in August 2015. In the laboratory experiment, the copepods were sampled directly in the field and incubated in ambient pH and temperature conditions after which the egg production rate and hatching success were analyzed. The experiment was complemented with a description of long-term monitoring data of seawater pH collected since 1996 at Storfjärden, a pelagic area near Tvärminne Zoological Station and the sampling location for this experiment. The results show that elevated temperature and pH had a positive effect on the egg production rate. The hatching success results indicate that elevated temperature may increase hatching rates at least when the temperature is within the optimum range for copepod. These results imply that copepods are used to adapting to changing conditions at least in the short term due to their behaviour of diurnal vertical migration. Further studies would be needed to determine if this adaptability enhances the copepods’ ability to endure the effects of climate change also in the long term

Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors

On a daily basis, planktonic organisms migrate vertically and thus experience widely varying conditions in their physico-chemical environment. In the Gulf of Finland, these changes are larger than values predicted by climate change scenarios predicted for the next century (up to 0.5 units in pH and 5 degrees C in temperature). In this work, we are interested in how temporal variations in physico-chemical characteristics of the water column on a daily and weekly scale influence oxidative stress level and antioxidant responses in the planktonic copepod of the genus Acartia. Responses were determined from samples collected during a two-week field survey in the western Gulf of Finland, Baltic Sea. Our results showed that GST (Glutathione-S-transferase) enzyme activity increased in the surface waters between Weeks I and II, indicating antioxidant defense mechanism activation. This is most likely due to elevating temperature, pH, and dissolved oxygen observed between these two weeks. During Week II also GSSG (oxidized glutathione) was detected, indicating that copepods responded to stressor(s) in the environment. Our results suggest that Acartia copepods seem fairly tolerant to weekly fluctuations in environmental conditions in coastal and estuarine areas, in terms of antioxidant defense and oxidative stress. This could be directly connected to a very efficient glutathione cycling system acting as antioxidant defense system for neutralizing ROS and avoiding elevated levels of LPX.Peer reviewe

Glutathione S-transferase activity measured in <i>Acartia</i> sp.

<p>The animals were collected at different depths (5, 15, 20 and 25 m) during two weeks in August 2015.</p

Main hydrographic variables measured (mean ± SD) and the number of zooplankton samples collected during the study.

<p>Weeks I and II are separated by a thick border.</p

Antioxidant defense and oxidative stress variables measured in <i>Acartia s</i>p. in August 2015.

<p>Week I and II are separated by a thick border; CAT: Catalase, ORAC: Oxygen radical absorbance capacity, SOD: Superoxide dismutase, GR: Glutathione reductase, GST: glutathione S-transferase, totGSH: total glutathione, GSSG: oxidized glutathione, LPX: Lipid peroxidation, ND: under detection level, n: number of samples.</p

Component matrix for Fig 2.

<p>(A). Biomarker abbreviations are as follows: CAT: Catalase, LPX: Lipid peroxidation, GST: glutathione S-transferase, ORAC: Oxygen radical absorbance capacity, SOD: Superoxide dismutase, totGSH: total glutathione, GSSG.A: oxidized glutathione Absent, GSSG.P: oxidized glutathione Present, GR.A: Glutathione Reductase Absent, GR.P: Glutathione Reductase Present. (B). Environmental variables. Loadings highlighted in bold represent the highest absolute value of the parameter when considering different PCs.</p

Component 1 and 2 scores from Principal Component Analysis (PCA) for <i>Acartia</i> sp. collected in the western Gulf of Finland during two weeks.

<p>Samples collected during Week I (black dots 1–10), and samples collected during Week II (black squares, 11–24). The corresponding loading plots (biomarker variables and environmental variables) are superimposed on the scores plot. Abbreviations are as follows: CAT Catalase, LPX Lipid peroxidation, GST Glutathione S-transferase, ORAC Oxygen radical absorbance capacity, SOD Superoxide dismutase, totGSH total glutathione, GSSG.A oxidized glutathione Absent, GSSG.P oxidized glutathione Present, GR.A Glutathione reductase Absent, GR.P Glutathione reductase Present. One sample from 11 August was not considered in the PCA analysis as there were no replicates.</p