Jun Kita

Comparison of the lethal effect of CO2 and acidification on red sea bream (Pagrus major) during the early developmental stages

To compare the acute toxicity of CO(2)- and HCl-acidified seawater, eggs and larvae of a marine fish, Pagrus major, were exposed to seawater equilibrated with CO(2)-enriched gas mixtures (CO(2)=5% or 10%, O(2)=20.95% balanced with N(2)) or seawater acidified with 1 N HCl at two pH levels (pH 6.2 (=5% CO(2)) and 5.9 (=10% CO(2))) for 6 h (eggs) or 24 h (larvae). Mortalities of eggs were 85.8% (CO(2)) and 3.6% (HCl) at pH 6.2, and 97.4% (CO(2)) and 0.9% (HCl) at pH 5.9, while those of larvae were 61.2% (CO(2)) and 1.6% (HCl) at pH 6.2, and 100% (CO(2)) and 5.0% (HCl) at pH 5.9. Thus, previous research on the effects of acidified seawater on marine organisms, as a substitute for CO(2), has largely underestimated the toxic effects of CO(2).

Effects of Lethal Levels of Environmental Hypercapnia on Cardiovascular and Blood-Gas Status in Yellowtail, Seriola quinqueradiata

Abstract The cardiorespiratory responses were examined in yellowtail, Seriola quinqueradiata exposed to two levels of hypercapnia (seawater equilibrated with a gas mixture containing 1% CO2 (water PCO2 = 7 mmHg) or 5% CO2 (38 mmHg)) for 72 hr at 20°C. Mortality was 100% within 8 hr at 5% CO2, while no fish died at 1% CO2. No cardiovascular variables (cardiac output, Q̇; heart rate, HR; stroke volume, SV and arterial blood pressure, BP) significantly changed from pre-exposure values during exposure to 1% CO2. Arterial CO2 partial pressure (PaCO2) significantly increased (P < 0.05), reaching a new steady-state level after 3 hr. Arterial blood pH (pHa) decreased initially (P < 0.05), but was subsequently restored by elevation of plasma bicarbonate ([HCO3–]). Arterial O2 partial pressure (PaO2), oxygen content (CaO2), and hematocrit (Hct) were maintained throughout the exposure period. In contrast, exposure to 5% CO2 dramatically reduced Q̇ (P < 0.05) through decreasing SV (P < 0.05), although HR did not change. BP was transiently elevated (P < 0.05), followed by a precipitous fall before death. The pHa was restored incompletely despite a significant increase in [HCO3–]. PaO2 decreased only shortly before death, whereas CaO2 kept elevated due to a large increase in Hct (P < 0.05). We tentatively conclude that cardiac failure is a primary physiological disorder that would lead to death of fish subjected to high environmental CO2 pressures.

Effects of CO2 on benthic biota: an in situ benthic chamber experiment in Storfjorden (Norway)

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO2 leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO2. In situ CO2 exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO2 in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO2 concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.

Methodology for Impact Assessment of Ocean CO 2 Sequestration on Deep-sea Organisms

In order to assess the biological impact of ocean CO2 sequestration, we present a methodology to quantify impacts of elevated CO2 concentration on marine organisms using existing biological data and discuss required research work for the future. For a quantitative assessment of deep-sea CO2 injection (mid- depth type) impacts on marine organisms, we estimated No Observed Effect Concentration (NOEC) of CO2 for copepods. Our preliminary analysis indicated that the NOECco2 for copepods including deep-sea species is ap Delta3,000 ppm. However, further data are needed on acute, chronic and ecosystem impacts for applying reduced Assessment Factor (AF) which is essential for reliable estimation of Predicted No Effect Concentration (PNECco2). For an acute impact assessment, careful consideration on differences in sensitivities to CO2 between shallow and deep- sea species is required. For the purpose of accurate chronic impact assessment, long-term experiments on sub-lethal impacts are required. However, ecosystem impacts would be difficult to predict based only on laboratory experiments and field experiments are necessary for confirming expected consequences from laboratory experiments and for lessening the uncertainties of extrapolation.