Posts Tagged 'field'

Primary producers may ameliorate impacts of daytime CO2 addition in a coastal marine ecosystem

Predicting the impacts of ocean acidification in coastal habitats is complicated by bio-physical feedbacks between organisms and carbonate chemistry. Daily changes in pH and other carbonate parameters in coastal ecosystems, associated with processes such as photosynthesis and respiration, often greatly exceed global mean predicted changes over the next century. We assessed the strength of these feedbacks under projected elevated CO2 levels by conducting a field experiment in 10 macrophyte-dominated tide pools on the coast of California, USA. We evaluated changes in carbonate parameters over time and found that under ambient conditions, daytime changes in pH, pCO2, net ecosystem calcification (NEC), and O2 concentrations were strongly related to rates of net community production (NCP). CO2 was added to pools during daytime low tides, which should have reduced pH and enhanced pCO2. However, photosynthesis rapidly reduced pCO2 and increased pH, so effects of CO2 addition were not apparent unless we accounted for seaweed and surfgrass abundances. In the absence of macrophytes, CO2 addition caused pH to decline by ∼0.6 units and pCO2 to increase by ∼487 µatm over 6 hr during the daytime low tide. As macrophyte abundances increased, the impacts of CO2 addition declined because more CO2 was absorbed due to photosynthesis. Effects of CO2addition were, therefore, modified by feedbacks between NCP, pH, pCO2, and NEC. Our results underscore the potential importance of coastal macrophytes in ameliorating impacts of ocean acidification.

Continue reading ‘Primary producers may ameliorate impacts of daytime CO2 addition in a coastal marine ecosystem’

Effect of elevated pCO2 on trace gas production during an ocean acidification mesocosm experiment

A mesocosm experiment was conducted in Wuyuan Bay (Xiamen), China to investigate the effects of elevated pCO2 on phytoplankton species and production of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) as well as four halocarbon compounds (CHBrCl2, CH3Br, CH2Br2, and CH3I). Over a period of 5 weeks, P. tricornutum outcompeted T. weissflogii and E. huxleyi, comprising more than 99 % of the final biomass. During the logarithmic growth phase (phase I), DMS concentrations in high pCO2 mesocosms (1000 µatm) were 28.2 % lower than those in low pCO2 mesocosms (400 µatm). Elevated pCO2 led to a delay in DMSP-consuming bacteria attached to T. weissflogii and P. tricornutum and finally resulted in the delay of DMS concentration in the HC treatment. Unlike DMS, the elevated pCO2 did not affect DMSP production ability of T. weissflogii or P. tricornutum throughout the 5 week culture. A positive relationship was detected between CH3I and T. weissflogii and P. tricornutum during the experiment, and there was a 40.2 % reduction in mean CH3I concentrations in the HC mesocosms. CHBrCl2, CH3Br, and CH2Br2 concentrations did not increase with elevated chlorophyll a (Chl a) concentrations compared with DMS(P) and CH3I, and there were no major peak in the HC or LC mesocosms. In addition, no effect of elevated pCO2 was identified for any of the three bromocarbons. Continue reading ‘Effect of elevated pCO2 on trace gas production during an ocean acidification mesocosm experiment’

Residing at low pH matters, resilience of the egg jelly coat of sea urchins living at a CO2 vent site

The sea urchin egg jelly coat is important in fertilisation as a source of sperm activating compounds, in species-specific gamete recognition and in increasing egg target size for sperm. The impact of ocean acidification (− 0.3 to 0.5 pHT units) on the egg jelly coat of Arbacia lixula was investigated comparing populations resident in a control (pHT 8.00) and a CO2 vent site (mean pHT 7.69) in Ischia. Measurements of egg and jelly coat size showed no significant differences between sea urchins from the different sites; however, sensitivity of the jelly coat to decreased pH differed depending on the origin of the population. Acidification to pHT 7.7 and 7.5 significantly decreased egg jelly coat size of control urchins by 27 and 23%, respectively. In contrast, the jelly coat of the vent urchins was not affected by acidification. For the vent urchins, there was a significant positive relationship between egg and jelly coat size, a relationship not seen for the eggs of females from the control site. As egg and jelly coat size was similar between both populations, vent A. lixula jelly coats are likely to be chemically fine-tuned for the low pH environment. That the egg jelly coat of sea urchins from the vent site was robust to low pH shows intraspecific variation in this trait, and that this difference may be a maternal adaptive strategy or plastic response. If this is a common response in sea urchins, this would facilitate the maintenance of gamete function, facilitating fertilisation success in a low pH ocean.

Continue reading ‘Residing at low pH matters, resilience of the egg jelly coat of sea urchins living at a CO2 vent site’

Comprehensive research of the coastal water area of the Sea of Japan and Sea of Okhotsk under the influence of river runoff ( cruise 71 of the R/V Professor Gagarinskii)

An expedition abroad the R/V Professor Gagaranskii was conducted in the water area of the north-western shelf of the Sea of Okhotsk and the Tatar Strait to study the production and destruction of organic matter, as well as the biochemical processes governing the distribution and accumulation of particulate and dissolves forms of microelements (Fe, Mn, Zn, Cu, Cs, Ni, Pb) in a coastal and estuary ecosystems.

The main aim of the expedition was comprehensive hydrological, hydrochemical, hydrobiological, and geochemical observations on the northeasten slope of Sakhalin Island; in the estuaries of the Usalgin, Ulban, Tugur, and Uda rivers and their adjacent water areas (Shantar archipelago); in the estuary of the Amur River and adjacent water areas (Sakhalin Bay, Tatar Strait); and in the estuary of the Tumnin River.

Continue reading ‘Comprehensive research of the coastal water area of the Sea of Japan and Sea of Okhotsk under the influence of river runoff ( cruise 71 of the R/V Professor Gagarinskii)’

The Red Sea simulator: a high‐precision climate change mesocosm with automated monitoring for the long‐term study of coral reef organisms

Experimental systems that enable the controlled perturbation of environmental parameters toward future scenarios are in high demand and becoming increasingly advanced. Herein, we describe the design and assess the performance of a large‐scale, flow‐through, mesocosm system. Located in the northern Gulf of Aqaba, the Red Sea simulator (RSS) was constructed in order to expose local coral reef organisms to future ocean scenarios. Seawater temperature and pH are typically set to a delta from incoming seawater readings and thus follow the diel range. This is achieved through automated monitoring (sensor‐carrying robot) and feedback system and a remote‐controlled user interface. Up to six different temperatures and four pH scenarios can be concomitantly operated in a total of 80 experimental aquaria. In addition, the RSS currently facilitates the manipulation of light intensity, light spectra, nutrient concentration, flow, and feeding regime. Monitoring data show that the system performs well; meeting the user‐defined environmental settings. A variety of reef organisms have been housed in the system for several months. Brooding reef building and soft coral species maintained in the simulator for many months have released planulae in synchrony with field colonies. This system boasts a high degree of replication, potential for multistressor manipulation, typical physiochemical environmental variability, and remotely controlled monitoring and data acquisition. These aspects greatly enhance our ability to make ecologically relevant performance assessments in a changing world.

Continue reading ‘The Red Sea simulator: a high‐precision climate change mesocosm with automated monitoring for the long‐term study of coral reef organisms’

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°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.

Continue reading ‘Oxidative stress and antioxidant defense responses in Acartia copepods in relation to environmental factors’

Macrobenthic assemblage characteristics under stressed waters and ecological health assessment using AMBI and M-AMBI: a case study at the Xin’an River Estuary, Yantai, China

To understand the ecological status and macrobenthic assemblages of the Xin’an River Estuary and its adjacent waters, a survey was conducted for environmental variables and macrobenthic assemblage structure in September 2012 (Yantai, China). Several methods are adopted in the data analysis process:dominance index, diversity indices, cluster analysis, non-metric multi-dimentional scaling ordination, AMBI and M-AMBI. The dissolved inorganic nitrogen and soluble reactive phosphorus of six out of eight sampling stations were in a good condition with low concentration. The average value of DO ((2.89±0.60) mg/L) and pH (4.28±0.43) indicated that the research area faced with the risk of ocean acidification and underlying hypoxia. A total of 62 species were identified, of which the dominant species group was polychaetes. The average abundance and biomass was 577.50 ind./m2 and 6.01 g/m2, respectively. Compared with historical data, the macrobenthic assemblage structure at waters around the Xin’an River Estuary was in a relatively stable status from 2009 to 2012. Contaminant indicator species Capitella capitata appeared at Sta. Y1, indicating the animals here suffered from hypoxia and acidification. AMBI and M-AMBI results showed that most sampling stations were slightly disturbed, which were coincided with the abiotic measurement on evaluating the health conditions. Macrobenthic communities suffered pressures from ocean acidification and hypoxia at the research waters, particularly those at Stas Y1, Y2 and Y5, which displays negative results in benthic health evaluation.

Continue reading ‘Macrobenthic assemblage characteristics under stressed waters and ecological health assessment using AMBI and M-AMBI: a case study at the Xin’an River Estuary, Yantai, China’


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