Effects of high CO2 levels on the ecophysiology of the diatom Thalassiosira weissflogii differ depending on the iron nutritional status

Abstract Iron availability in seawater, namely the concentration of dissolved inorganic iron ([Fe′]), is affected by changes in pH. Such changes in the availability of iron should be taken into account when investigating the effects of ocean acidification on phytoplankton ecophysiology because iron plays a key role in phytoplankton metabolism. However, changes in iron availability in response to changes in ocean acidity are difficult to quantify specifically using natural seawater because these factors change simultaneously. In the present study, the availability of iron and carbonate chemistry were manipulated individually and simultaneously in the laboratory to examine the effect of each factor on phytoplankton ecophysiology. The effects of various pCO2 conditions (∼390, ∼600, and ∼800 µatm) on the growth, cell size, and elemental stoichiometry (carbon [C], nitrogen [N], phosphorus [P], and silicon [Si]) of the diatom Thalassiosira weissflogii under high iron ([Fe′] = ∼240 pmol l−1) and low iron ([Fe′] = ∼24 pmol l−1) conditions were investigated. Cell volume decreased with increasing pCO2, whereas intracellular C, N, and P concentrations increased with increasing pCO2 only under high iron conditions. Si:C, Si:N, and Si:P ratios decreased with increasing pCO2. It reflects higher production of net C, N, and P with no corresponding change in net Si production under high pCO2 and high iron conditions. In contrast, significant linear relationships between measured parameters and pCO2 were rarely detected under low iron conditions. We conclude that the increasing CO2 levels could affect on the biogeochemical cycling of bioelements selectively under the iron-replete conditions in the coastal ecosystems.

Download Full-text

Synergistic effects of pCO2 and iron availability on nutrient consumption ratio of the Bering Sea phytoplankton community

Biogeosciences ◽

10.5194/bg-10-6309-2013 ◽

2013 ◽

Vol 10 (10) ◽

pp. 6309-6321 ◽

Cited By ~ 20

Author(s):

K. Sugie ◽

H. Endo ◽

K. Suzuki ◽

J. Nishioka ◽

H. Kiyosawa ◽

...

Keyword(s):

Growth Rate ◽

Bering Sea ◽

Biogenic Silica ◽

Phytoplankton Community ◽

Specific Growth ◽

Iron Bioavailability ◽

Iron Availability ◽

Carbonate Chemistry ◽

High Co2 ◽

The Bering Sea

Abstract. Little is known concerning the effect of CO2 on phytoplankton ecophysiological processes under nutrient and trace element-limited conditions, because most CO2 manipulation experiments have been conducted under elements-replete conditions. To investigate the effects of CO2 and iron availability on phytoplankton ecophysiology, we conducted an experiment in September 2009 using a phytoplankton community in the iron limited, high-nutrient, low-chlorophyll (HNLC) region of the Bering Sea basin . Carbonate chemistry was controlled by the bubbling of the several levels of CO2 concentration (180, 380, 600, and 1000 ppm) controlled air, and two iron conditions were established, one with and one without the addition of inorganic iron. We demonstrated that in the iron-limited control conditions, the specific growth rate and the maximum photochemical quantum efficiency (Fv/Fm) of photosystem (PS) II decreased with increasing CO2 levels, suggesting a further decrease in iron bioavailability under the high-CO2 conditions. In addition, biogenic silica to particulate nitrogen and biogenic silica to particulate organic carbon ratios increased from 2.65 to 3.75 and 0.39 to 0.50, respectively, with an increase in the CO2 level in the iron-limited controls. By contrast, the specific growth rate, Fv/Fm values and elemental compositions in the iron-added treatments did not change in response to the CO2 variations, indicating that the addition of iron canceled out the effect of the modulation of iron bioavailability due to the change in carbonate chemistry. Our results suggest that high-CO2 conditions can alter the biogeochemical cycling of nutrients through decreasing iron bioavailability in the iron-limited HNLC regions in the future.

Download Full-text

Synergistic effects of pCO2 and iron availability on nutrient consumption ratio of the Bering Sea phytoplankton community

Biogeosciences Discussions ◽

10.5194/bgd-10-4331-2013 ◽

2013 ◽

Vol 10 (3) ◽

pp. 4331-4365 ◽

Cited By ~ 1

Author(s):

K. Sugie ◽

H. Endo ◽

K. Suzuki ◽

J. Nishioka ◽

H. Kiyosawa ◽

...

Keyword(s):

Growth Rate ◽

Bering Sea ◽

Biogenic Silica ◽

Phytoplankton Community ◽

Specific Growth ◽

Iron Bioavailability ◽

Iron Availability ◽

Carbonate Chemistry ◽

High Co2 ◽

The Bering Sea

Abstract. Little is known concerning the effect of CO2 on phytoplankton ecophysiological processes under nutrient and trace element-limited conditions, because most of the CO2 manipulation experiments have been conducted under these element-replete conditions. To investigate the effects of CO2 and iron availability on phytoplankton ecophysiology, we conducted an experiment using a phytoplankton community in the iron-limited, high-nutrient, low-chlorophyll (HNLC) region of the Bering Sea basin in September 2009. Carbonate chemistry was controlled by the bubbling of the several levels of CO2 concentration (180, 380, 600, and 1000 ppm) controlled air, and two iron conditions were established with or without the addition of inorganic iron. We demonstrated that in the iron-limited control conditions, the specific growth rate and the maximum photochemical quantum efficiency (Fv/Fm) of photosystem (PS) II decreased with increasing CO2 levels, suggesting a~further decrease in iron bioavailability under the high CO2 conditions. In addition, biogenic silica to particulate nitrogen and biogenic silica to particulate organic carbon ratios increased from 2.65 to 3.75 and 0.39 to 0.50, respectively with an increase in CO2 level in the iron-limited controls. In contrast, in the iron-added treatments, specific growth rate, Fv/Fm values and elemental compositions did not change in response to the CO2 variations, indicating that the addition of iron cancelled out the effect of the modulation of iron bioavailability due to the change in carbonate chemistry. Our results suggest that high CO2 conditions can alter the biogeochemical cycling of nutrients through decreasing iron bioavailability in the iron-limited HNLC regions in the future.

Download Full-text

Effects of iron on the elemental stoichiometry during EIFEX and in the diatoms Fragilariopsis kerguelensis and Chaetoceros dichaeta

Biogeosciences ◽

10.5194/bg-4-569-2007 ◽

2007 ◽

Vol 4 (4) ◽

pp. 569-579 ◽

Cited By ~ 47

Author(s):

L. J. Hoffmann ◽

I. Peeken ◽

K. Lochte

Keyword(s):

Laboratory Experiments ◽

Iron Availability ◽

Diatom Species ◽

Elemental Ratios ◽

Fertilization Experiment ◽

High Iron ◽

Iron Fertilization ◽

Elemental Stoichiometry ◽

Fertilization Experiments

Abstract. The interaction between iron availability and the phytoplankton elemental composition was investigated during the in situ iron fertilization experiment EIFEX and in laboratory experiments with the Southern Ocean diatom species Fragilariopsis kerguelensis and Chaetoceros dichaeta. Contrary to other in situ iron fertilization experiments we observed an increase in the BSi:POC, BSi:PON, and BSi:POP ratios within the iron fertilized patch during EIFEX. This is possibly caused by a relatively stronger increase in diatom abundance compared to other phytoplankton groups and does not necessarily represent the amount of silicification of single diatom cells. In laboratory experiments with F. kerguelensis and C. dichaeta no changes in the POC:PON, PON:POP, and POC:POP ratios were found with changing iron availability in both species. BSi:POC, BSi:PON, and BSi:POP ratios were significantly lower in the high iron treatments compared to the controls. In F. kerguelensis this was caused by a decrease in cellular BSi concentrations and therefore possibly less silicification. In C. dichaeta no change in cellular BSi concentration was found. Here lower BSi:POC, BSi:PON, and BSi:POP ratios were caused by an increase in cellular C, N, and P under high iron conditions. These results indicate that iron limitation does not always increase silicification in diatoms and that changes in the BSi:POC, BSi:PON, and BSi:POP ratios under iron fertilization in the field are caused by a variety of different mechanisms. Our results therefore imply that simple cause-and-effect relationships are not always applicable for modeling of elemental ratios.

Download Full-text

Behavioural responses to simulated bird attacks in marine three-spined sticklebacks after exposure to high CO2 levels

Marine and Freshwater Research ◽

10.1071/mf14144 ◽

2015 ◽

Vol 66 (10) ◽

pp. 877 ◽

Cited By ~ 20

Author(s):

Joacim Näslund ◽

Erik Lindström ◽

Floriana Lai ◽

Fredrik Jutfelt

Keyword(s):

Gasterosteus Aculeatus ◽

Elevated Pco2 ◽

Control Fish ◽

High Pco2 ◽

Control Group ◽

High Co2 ◽

Treatment Groups ◽

Predator Attack ◽

Partial Pressure Of Co2 ◽

Co2 Levels

The rising partial pressure of CO2 (pCO2) in oceanic water, termed ocean acidification, is an impending threat to marine life and has previously been reported to affect several aspects of fish behaviour. We evaluated the behavioural response to a simulated avian predator attack and lateralisation in three-spined sticklebacks (Gasterosteus aculeatus) after 10 and 20 days of exposure to present day pCO2 (400μatm) or elevated pCO2 (1000μatm). We show that elevated pCO2 lead to reduced behavioural lateralisation. However, no major differences in the sheltering response after an overhead avian attack were observed; fish from both treatments exhibited similar and strong responses. Compared with fish exposed to high pCO2, the control fish took longer time to freeze (i.e. stop moving) after attack at Day 20 but not Day 10. The freezing duration was significantly reduced between Day 10 and Day 20 in elevated pCO2, whereas no such reduction was observed in the control-group. However, no significant differences between treatment groups were detected at Day 20. These results demonstrate that behaviour is indeed altered by high CO2 levels, although the general responses to avian predation stimuli remain similar to those of unexposed fish, indicating that some predator avoidance behaviours of three-spined sticklebacks are robust to environmental disturbance.

Download Full-text

Effects of iron on the elemental stoichiometry during EIFEX and in the diatoms Fragilariopsis kerguelensis and Chaetoceros dichaeta

Biogeosciences Discussions ◽

10.5194/bgd-4-249-2007 ◽

2007 ◽

Vol 4 (1) ◽

pp. 249-275 ◽

Cited By ~ 1

Author(s):

L. J. Hoffmann ◽

I. Peeken ◽

K. Lochte

Keyword(s):

Laboratory Experiments ◽

Iron Limitation ◽

Iron Availability ◽

Diatom Species ◽

Fertilization Experiment ◽

High Iron ◽

Iron Fertilization ◽

Elemental Stoichiometry ◽

Fertilization Experiments

Abstract. The interaction between iron availability and the phytoplankton elemental composition was investigated during the in situ iron fertilization experiment EIFEX and in laboratory experiments with the Southern Ocean diatom species Fragilariopsis kerguelensis and Chaetoceros dichaeta. Contrary to other in situ iron fertilization experiments we observed an increase in the bPSi : POC, bPSi : PON, and bPSi : POP ratios within the iron fertilized patch during EIFEX. This is possibly caused by a relatively stronger increase in diatom abundance compared to other phytoplankton groups and does not necessarily represent the amount of silicification of single diatom cells. In laboratory experiments with F. kerguelensis and C. dichaeta no changes in the POC : PON, PON : POP, and POC : POP ratios were found with changing iron availability in both species. BPSi : POC, bPSi : PON, and bPSi : POP ratios were significantly lower in the high iron treatments compared to the controls. In F. kerguelensis this is caused by a decrease in cellular bPSi concentrations and therefore possibly less silicification. In C. dichaeta no change in cellular bPSi concentration was found. Here lower bPSi : POC, bPSi : PON, and bPSi : POP ratios were caused by an increase in cellular C, N, and P under high iron conditions. We therefore assume that iron limitation does not generally increase silicification of diatoms and that changes in the bPSi : POC, bPSi : PON, and bPSi : POP ratios under iron fertilization in the field are caused by a variety of different mechanisms. These results imply that the effect of iron on nutrient uptake is more complex than hitherto assumed.

Download Full-text

Physiological resilience of pink salmon to naturally occurring ocean acidification

Conservation Physiology ◽

10.1093/conphys/coaa059 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Andrea Y Frommel ◽

Justin Carless ◽

Brian P V Hunt ◽

Colin J Brauner

Keyword(s):

British Columbia ◽

Elevated Co2 ◽

Condition Factor ◽

Pacific Salmon ◽

Pink Salmon ◽

Hypoxia Tolerance ◽

High Co2 ◽

The North ◽

Naturally Occurring ◽

Co2 Levels

Abstract Pacific salmon stocks are in decline with climate change named as a contributing factor. The North Pacific coast of British Columbia is characterized by strong temporal and spatial heterogeneity in ocean conditions with upwelling events elevating CO2 levels up to 10-fold those of pre-industrial global averages. Early life stages of pink salmon have been shown to be affected by these CO2 levels, and juveniles naturally migrate through regions of high CO2 during the energetically costly phase of smoltification. To investigate the physiological response of out-migrating wild juvenile pink salmon to these naturally occurring elevated CO2 levels, we captured fish in Georgia Strait, British Columbia and transported them to a marine lab (Hakai Institute, Quadra Island) where fish were exposed to one of three CO2 levels (850, 1500 and 2000 μatm CO2) for 2 weeks. At ½, 1 and 2 weeks of exposure, we measured their weight and length to calculate condition factor (Fulton’s K), as well as haematocrit and plasma [Cl−]. At each of these times, two additional stressors were imposed (hypoxia and temperature) to provide further insight into their physiological condition. Juvenile pink salmon were largely robust to elevated CO2 concentrations up to 2000 μatm CO2, with no mortality or change in condition factor over the 2-week exposure duration. After 1 week of exposure, temperature and hypoxia tolerance were significantly reduced in high CO2, an effect that did not persist to 2 weeks of exposure. Haematocrit was increased by 20% after 2 weeks in the CO2 treatments relative to the initial measurements, while plasma [Cl−] was not significantly different. Taken together, these data indicate that juvenile pink salmon are quite resilient to naturally occurring high CO2 levels during their ocean outmigration.

Download Full-text