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Additive pressures of elevated sea surface temperatures and herbicides on symbiont-bearing foraminifera.

van Dam JW, Negri AP, Mueller JF, Altenburger R, Uthicke S - PLoS ONE (2012)

Bottom Line: Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m)), while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v)/F(m)), interpreted as photodamage.A significant linear correlation was found between reduced F(v)/F(m) and loss of chlorophyll a.As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, School of Biological Sciences, St Lucia, Australia. j.vandam@aims.gov.au

ABSTRACT
Elevated ocean temperatures and agrochemical pollution individually threaten inshore coral reefs, but these pressures are likely to occur simultaneously. Experiments were conducted to evaluate the combined effects of elevated temperature and the photosystem II (PSII) inhibiting herbicide diuron on several types of symbiotic algae (diatom, dinoflagellate or rhodophyte) of benthic foraminifera in hospite. Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m)), while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v)/F(m)), interpreted as photodamage. Additionally, elevated temperatures were shown to cause bleaching through loss of chlorophyll a in foraminifera hosting either diatoms or dinoflagellates. A significant linear correlation was found between reduced F(v)/F(m) and loss of chlorophyll a. In most cases, symbionts within foraminifera proved more sensitive to thermal stress in the presence of diuron (≥ 1 µg L(-1)). The mixture toxicity model of Independent Action (IA) described the combined effects of temperature and diuron on the photosystem of species hosting diatoms or dinoflagellates convincingly and in agreement with probabilistic statistics, so a response additive joint action can be assumed. We thus demonstrate that improving water quality can improve resilience of symbiotic phototrophs to projected increases in ocean temperatures. As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

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Related in: MedlinePlus

Relative inhibition of maximum quantum PSII yield (Fv/Fm) of symbiotic microalgae of six species of benthic foraminifera.Fv/Fm was measured in hospite, following 96 h exposure to low diuron concentrations at temperatures ranging from 26–34°C. Data are means (x) ± SE, n = 6 specimens per treatment.
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pone-0033900-g003: Relative inhibition of maximum quantum PSII yield (Fv/Fm) of symbiotic microalgae of six species of benthic foraminifera.Fv/Fm was measured in hospite, following 96 h exposure to low diuron concentrations at temperatures ranging from 26–34°C. Data are means (x) ± SE, n = 6 specimens per treatment.

Mentions: Combined stressor inhibition curves for inhibition Fv/Fm (Fig. 3) followed similar patterns as those describing inhibition ΔF/F′m (Fig. 1). ANOVA revealed significant effects of both temperature and diuron on Fv/Fm for any of the species tested except for A. quoyi (unaffected by diuron) and P. planatus (unaffected by neither stressor) (Table 2). After 96 hours incubation, 1 µg L−1 diuron did not significantly decrease Fv/Fm in diatom-bearing species (Fig. 3A–C), but did so for M. vertebralis hosting dinoflagellates (4.5–6% reduction, p<0.003 (adjusted post-hoc α)) (Fig. 3D and 3E). 3 µg L−1 diuron caused 6–11% photodamage in diatoms and 7–17% in dinoflagellates (Table 2; Fig. 3).


Additive pressures of elevated sea surface temperatures and herbicides on symbiont-bearing foraminifera.

van Dam JW, Negri AP, Mueller JF, Altenburger R, Uthicke S - PLoS ONE (2012)

Relative inhibition of maximum quantum PSII yield (Fv/Fm) of symbiotic microalgae of six species of benthic foraminifera.Fv/Fm was measured in hospite, following 96 h exposure to low diuron concentrations at temperatures ranging from 26–34°C. Data are means (x) ± SE, n = 6 specimens per treatment.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3306314&req=5

pone-0033900-g003: Relative inhibition of maximum quantum PSII yield (Fv/Fm) of symbiotic microalgae of six species of benthic foraminifera.Fv/Fm was measured in hospite, following 96 h exposure to low diuron concentrations at temperatures ranging from 26–34°C. Data are means (x) ± SE, n = 6 specimens per treatment.
Mentions: Combined stressor inhibition curves for inhibition Fv/Fm (Fig. 3) followed similar patterns as those describing inhibition ΔF/F′m (Fig. 1). ANOVA revealed significant effects of both temperature and diuron on Fv/Fm for any of the species tested except for A. quoyi (unaffected by diuron) and P. planatus (unaffected by neither stressor) (Table 2). After 96 hours incubation, 1 µg L−1 diuron did not significantly decrease Fv/Fm in diatom-bearing species (Fig. 3A–C), but did so for M. vertebralis hosting dinoflagellates (4.5–6% reduction, p<0.003 (adjusted post-hoc α)) (Fig. 3D and 3E). 3 µg L−1 diuron caused 6–11% photodamage in diatoms and 7–17% in dinoflagellates (Table 2; Fig. 3).

Bottom Line: Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m)), while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v)/F(m)), interpreted as photodamage.A significant linear correlation was found between reduced F(v)/F(m) and loss of chlorophyll a.As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

View Article: PubMed Central - PubMed

Affiliation: The University of Queensland, School of Biological Sciences, St Lucia, Australia. j.vandam@aims.gov.au

ABSTRACT
Elevated ocean temperatures and agrochemical pollution individually threaten inshore coral reefs, but these pressures are likely to occur simultaneously. Experiments were conducted to evaluate the combined effects of elevated temperature and the photosystem II (PSII) inhibiting herbicide diuron on several types of symbiotic algae (diatom, dinoflagellate or rhodophyte) of benthic foraminifera in hospite. Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F'(m)), while elevated temperatures (>30 °C, only 2 °C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (F(v)/F(m)), interpreted as photodamage. Additionally, elevated temperatures were shown to cause bleaching through loss of chlorophyll a in foraminifera hosting either diatoms or dinoflagellates. A significant linear correlation was found between reduced F(v)/F(m) and loss of chlorophyll a. In most cases, symbionts within foraminifera proved more sensitive to thermal stress in the presence of diuron (≥ 1 µg L(-1)). The mixture toxicity model of Independent Action (IA) described the combined effects of temperature and diuron on the photosystem of species hosting diatoms or dinoflagellates convincingly and in agreement with probabilistic statistics, so a response additive joint action can be assumed. We thus demonstrate that improving water quality can improve resilience of symbiotic phototrophs to projected increases in ocean temperatures. As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures.

Show MeSH
Related in: MedlinePlus