Effects of ocean acidification on macroalgal communities

May combine two claims.

ANOVA results show a significant decrease in calcitic species number at mean pH 7.8, where the overall cover of calcareous algae was much lower than at mean pH 8.1.

“ANOVA results (Table 3) show a significant decrease in calcitic species number at mean pH 7.8, where the overall cover of calcareous algae was much lower than at mean pH 8.1.”

May combine two claims.

Twenty species of calcareous algae were sampled at normal pH, but only 15 at mean pH 7.8 and none at mean pH 6.7, where both calcite and aragonite saturation states were <1.

“Twenty species of calcareous algae were sampled at normal pH, but only 15 at mean pH 7.8 and none at mean pH 6.7, where both calcite and aragonite saturation states were b1 (Fig. 3).”

May combine two claims.

ANOVA and post hoc Tukey test showed highly significant reductions in species diversity (H′) as CO2 levels increased (H′ S1=2.29±0.07; H′ S2=1.88±0.07; H′ S3=1.18±0.05) (F=25.62; p<0.0001, and S1>S2>S3).

“Tukey test showed highly significant reductions in species diversity (H′) as CO 2 levels increased ( H′ S1 = 2.29 ± 0.07; H′ S2 = 1.88 ± 0.07 and H′ S3 =1.18 ± 0.05, respectively) (F = 25.62;p b 0.0001, and S1 N S2N S3).”

May combine two claims.

The highest species richness was sampled at S1 (pH=8.1); 5% fewer species were sampled at S2 (pH=7.8) and 72% fewer species were sampled at S3 (pH=6.7).

“The highest species richness (Table 2) was sampled at S1 (pH = 8.1); 5% fewer species were sampled at S2 (pH = 7.8) and 72% fewer species were sampled at S3 (pH = 6.7).”

May combine two claims.

At mean pH 6.7, where carbonate saturation levels were <1, calcareous species were absent and there was a 72% fall in species richness.

“At mean pH 6.7, where carbonate saturation levels were b 1, calcareous species were absent and there was a 72% fall in species richness.”

• AssumptionRests on an assumption: Differences in macroalgal communities among the three sectors along the pH gradient are attributable to pH/CO2 rather than other environmental differences among the sectors.

May combine two claims.

The Ochryophyte Dictyota dichotoma and the Rhodophyte Hildenbrandia rubra were present along the whole pH gradient with their highest percentage cover at mean pH 6.7 (S3).

“For example, the Ochryophyte Dictyota dichotoma and the Rhodophyte Hildenbrandia rubra were present along the whole pH gradient with their highest percentage cover at mean pH 6.7 (S3).”

May combine two claims.

Most calcitic and aragonitic species were more abundant at mean pH 8.1 (S1) although the thin calcitic crust Hydrolithon cruciatum and the lightly calcified aragonitic crust Peyssonnelia squamaria were more abundant at mean pH 7.8 (S2).

“Most calcitic (e.g., Jania rubens, Amphiroa rigida, Phymatolithon cf.lenormandii) and aragonitic species (e.g., Peyssonnelia spp., Padina pavonica and Halimeda tuna) were more abundant at mean pH 8.1 (S1) although the thin calcitic crust Hydrolithon cruciatum and the lightly calcified aragonitic crust Peyssonnelia squamaria were more abundant at mean pH 7.8 (S2).”

May combine two claims.

Calcitic species were significantly reduced in cover and species richness whereas a few non-calcified species became dominant along the pH gradient.

“Calcitic species were significantly reduced in cover and species richness whereas a few non-calcified species became dominant.”

• AssumptionRests on an assumption: Differences in macroalgal communities among the three sectors along the pH gradient are attributable to pH/CO2 rather than other environmental differences among the sectors.

May combine two claims.

Under extremely high CO2 conditions (mean pH 6.7), a few species dominated the simplified macroalgal assemblage and a very few exhibited enhanced reproduction, although high CO2 levels seemed to inhibit reproduction in others.

“Under these extremely high CO 2 conditions a few species dominated the simplified macroalgal assemblage and a very few exhibited enhanced reproduction, although high CO 2 levels seemed to inhibit reproduction in others.”

May combine two claims.

A total of 101 macroalgal taxa were recorded in the 27 20x20 cm quadrats, including 71 Rhodophyta, 16 Ochrophyta and 15 Chlorophyta.

“A total of 101 macroalgal taxa were recorded in the 27 20 * 20 cm quadrats, including 71 Rhodophyta, 16 Ochrophyta and 15 Chlorophyta (Table 1).”

May combine two claims.

The highest algal community complexity was evident at S1, whereas at S2 there was a shift towards greater dominance by fewer species and at S3 the simplified community was dominated by very few species.

“The highest algal community complexity was evident at S1, whereas at S2 there was a shift towards greater dominance by fewer species and at S3 the simplified community was dominated by very few species.”

• AssumptionRests on an assumption: Differences in macroalgal communities among the three sectors along the pH gradient are attributable to pH/CO2 rather than other environmental differences among the sectors.

May combine two claims.

SIMPER attributed the highest average similarity among quadrats of sector S3 dominated by D. dichotoma and the highest dissimilarity (>89%) among S3 and the other two sectors.

“SIMPER attributed the highest average similarity among quadrats of sector S3 dominated by D. dichotoma and the highest dissimilarity (N89%) among S3 and the other two sectors (Table 5).”

May combine two claims.

Some algal species are intolerant of increased CO2 levels whilst others thrive under these conditions.

“because some algal species are intolerant of increased CO 2 levels whilst others thrive under these conditions.”

May combine two claims.

Of the 101 macroalgal species recorded, 51% were turf-forming species, 25% were crustose and 24% were erect forms.

“Of the 101 macroalgal species recorded, 51% were turf-forming species, 25% were crustose and 24% were erect forms.”

May combine two claims.

There was an increase in reproductive frequency recorded in the high CO2 areas for D. dichotoma and O. truncata, whereas reproduction in calcareous species appeared to be negatively affected.

“There was even an increase in reproductive frequency recorded in the high CO 2 areas for D. dichotoma and O. truncata, whereas reproduction in calcareous species appeared to be negatively affected (Fig. 7).”

May combine two claims.

Only seven genera were contemporaneously found with reproductive structures at different pH values; among them, Polysiphonia scopulorum, O. truncata and D. dichotoma were able to reproduce at very high levels of CO2.

“Only seven genera were contemporaneously found with reproductive structures at different pH values (Fig. 7); among them, Polysiphonia scopulorum, O. truncata and D. dichotoma were able to reproduce at very high levels of CO 2 .”

May combine two claims.

The filamentous Rhodophyta P. scopulorum decreased in reproductive capacity as CO2 levels increased, even though it was present in the most acidified area.

“The filamentous Rhodophyta P. scopulorum, for example, decreased in reproductive capacity as CO 2 levels increased, even though it was present in the most acidified area.”

May combine two claims.

Samples A-C group together on the right side of the diagram and were from mean pH 8.1 (S1) with many calcified species present, samples D-F (from mean pH 7.8) group at the centre with fewer calcifiers and samples G-I from the most acidified area (S3) show a sharp discontinuity from the others.

“Samples A-C group together on the right side of the diagram and were from mean pH 8.1 (S1) with many calcified species present (circled), samples D-F (from mean pH 7.8) group at the centre with fewer calcifiers and samples G-I from the most acidified area (S3) show a sharp discontinuity from the others.”

The quote only partly states this claim.

Some of the Ochrophyta (D. dichotoma and O. truncata) appeared to grow and reproduce best at the highest CO2 levels found within the vents.

“Surprisingly, we found that some of the Ochrophyta (D. dichotoma and O. truncata) appeared to grow and Table 3 ANOVA results for carbonate saturation states (Ω calcite and Ω aragonite ) and the species richness of aragonitic and calcitic calcareous species from nine 20*20 cm quadrats placed along a rocky shore pH gradient from S1 (pH = 8.1), S2 (pH = 7.8) and S3 (pH = 6.7).Both Ω calcite and Ω a”

May combine two claims.

This differentiation is due both to species composition and their abundance differences among the three sites.

“This differentiation is due both to species composition and their abundance differences among the three sites.”

• AssumptionRests on an assumption: Differences in macroalgal communities among the three sectors along the pH gradient are attributable to pH/CO2 rather than other environmental differences among the sectors.

May combine two claims.

The first principal component explains 26.8% of the species distribution, and with the second component this reaches 38.8%.

“The first component explains 26.8% of the species distribution, and with the second component this reaches 38.8%.”

May combine two claims.

There was little change in the numbers of species in each morphological category from mean pH 8.1 to mean pH 7.8 although there was a large reduction in morphological category diversity at mean pH 6.7.

“There was little change in the numbers of species in each morphological category from mean pH 8.1 to mean pH 7.8 although there was a large reduction in morphological category diversity at mean pH 6.7 2007) (Table 1).”

May combine two claims.

Crustose algae remained abundant at mean pH 7.8 (S2) but were reduced in abundance in the area with highest CO2 levels (S3).

“Crustose algae remained abundant at mean pH 7.8 (S2) but were reduced in abundance in the area with highest CO 2 levels (S3).”

May combine two claims.

The SIMPER analysis shows that turf algae had a reduction and shift in species composition and area covered at mean pH 7.8 and that they were particularly scarce in the most acidified sector as also shown by the high values of average dissimilarity (91.8 and 93.2) between this sector and S2 and S1, respectively.

“The SIMPER analysis shows that turf algae had a reduction and shift in species composition and area covered at mean pH 7.8 and that they were particularly scarce in the most acidified sector as also shown by the high values of average dissimilarity (91.8 and 93.2) between this sector and S2 and S1, respectively (Table 6).”

May combine two claims.

Coralline algae appear to be amongst the most sensitive photoautotrophs as they have a skeletal mineralogy that dissolves easily at predicted levels of calcium carbonate saturation.

“Coralline algae appear to be amongst the most sensitive photoautotrophs as they have a skeletal mineralogy that dissolves easily at predicted levels of calcium carbonate saturation (Gao et al., 1993;Martin and Gattuso, 2009) and this is a particular concern as these algae are of fundamental ecological importance in a range of coastal habitats worldwide (Nelson, 2009).”

• cites Gao et al., 1993Not checked yet

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• cites Martin and Gattuso, 2009 sourceNot checked yet

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May combine two claims.

Differences in the susceptibility of macroalgae to ocean acidification may completely alter coastal ecosystems as changes in algal communities lead to changes in herbivore diversity and abundance.

“Differences in the susceptibility of macroalgae to ocean acidification may completely alter coastal ecosystems as changes in algal communities lead to changes in herbivore diversity and abundance (Benedetti-Cecchi et al., 2001;Darcy-Hall and Hall, 2008).”

• cites Benedetti-Cecchi et al., 2001 sourceNot checked yet

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• cites Darcy-Hall and Hall, 2008Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

In general, seagrasses seem able to thrive under high CO2 conditions, although the associated epiphytic algal cover falls as CO2 levels increase.

“In general, seagrasses seem able to thrive under high CO 2 conditions (Palacios and Zimmerman, 2007;Hall-Spencer et al., 2008), although the associated epiphytic algal cover falls as CO 2 levels increase (Martin et al., 2008).”

• cites Palacios and Zimmerman, 2007 sourceNot checked yet

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• cites Hall-Spencer et al., 2008 sourceNot checked yet

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• cites Martin et al., 2008 sourceNot checked yet

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May combine two claims.

Some marine algae benefit from higher CO2 levels, enhancing their growth and calcification, although the effects can vary between closely related species and even between strains of the same species.

“Some marine algae also benefit from higher CO 2 levels, enhancing their growth (Gao et al., 1999;Kübler et al., 1999;Riebesell et al., 2007) and calcification (Iglesias-Rodriguez et al., 2008), although the effects can vary between closely related species and even between strains of the same species (Langer et al., 2009).”

• cites Gao et al., 1999 sourceNot checked yet

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• cites Kübler et al., 1999 sourceNot checked yet

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• cites Riebesell et al., 2007 sourceNot checked yet

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May combine two claims.

Benthic photoautotrophs exhibit mixed responses to ocean acidification, indicating that there will be changes in their settlement, competition and dominance that will have knock-on effects on coastal ecosystems.

“Benthic photoautotrophs exhibit mixed responses to ocean acidification, indicating that there will be changes in their settlement, competition and dominance that will have knock-on effects on coastal ecosystems (Connell and Russell, 2010).”

• cites Connell and Russell, 2010Not checked yet

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May combine two claims.

Laboratory and mesocosm experiments have shown that changes in carbonate chemistry can significantly affect carbon fixation by photoautotrophs, which may cause global ecological disturbances over the coming decades.

“Laboratory and mesocosm experiments have shown that these changes in carbonate chemistry can significantly affect carbon fixation by photoautotrophs, which may cause global ecological disturbances over the coming decades (Kroeker et al., 2010) although there are still too few data to confirm whether this is the case (Hendricks and Duarte, 2010).”

• cites Kroeker et al., 2010 sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Normality and homogeneity of variances were always tested; when not met, data were log-transformed.

“The normality and homogeneity of variances were always tested; when not met, data were log-transformed.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Changes in species distributions and abundances are expected to propagate up through the trophic levels of marine food webs.

“Such changes in species distributions and abundances are expected to propagate up through the trophic levels of marine food webs (Fabry et al., 2008;Guinotte and Fabry, 2008) but little research has been carried out on the effects of ocean acidification at the ecosystem level (Wootton et al., 2008).”

• cites Fabry et al., 2008 sourceNot checked yet

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• cites Guinotte and Fabry, 2008Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

It is very difficult to scale up the observations undertaken to date to predict the effects of increasing CO2 emissions at the ecosystem level since most studies have been short-term (<1 year) on single or small groups of species.

“However, it is very difficult to scale up the observations undertaken to date to predict the effects of increasing CO 2 emissions at the ecosystem level since most studies have been short-term (b1 year) on single or small groups of species.”

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The average pH of the surface ocean has declined from 8.2 by 0.1 units since pre-industrial times due to CO2 emissions, and is projected to be around mean pH 7.8 by the end of the century.

“Observations and models indicate that the average pH of the surface ocean has declined from 8.2 by 0.1 units since pre-industrial times due to CO 2 emissions, and is projected to be around mean pH 7.8 by the end of the century (The Royal Society, 2005).”

• cites The Royal Society, 2005Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The oceans currently absorb over 25 million tonnes of anthropogenically produced CO2 every day, causing unprecedented changes to ocean chemistry.

“The oceans currently absorb over 25 million tonnes of anthropogenically produced CO 2 every day, causing unprecedented changes to ocean chemistry (IPCC, 2007).”

• cites IPCC, 2007Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Some cyanobacteria grow well with CO2 enrichment and their increased N2 fixation may alter ocean biogeochemistry.

“Some cyanobacteria grow well with CO 2 enrichment and their increased N 2 fixation may alter ocean biogeochemistry (Fu et al., 2008;Kranz et al., 2009).”

• cites Fu et al., 2008Not checked yet

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• cites Kranz et al., 2009 sourceNot checked yet

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May combine two claims.

Many macroalgal species are tolerant of long-term elevations in CO2 levels but macroalgal habitats are altered significantly as pH drops.

“Our data show that many macroalgal species are tolerant of long-term elevations in CO 2 levels but that macroalgal habitats are altered significantly as pH drops, contributing to a scant but growing body of evidence concerning the long-term effects of CO 2 emissions in vegetated marine systems.”

• AssumptionRests on an assumption: Differences in macroalgal communities among the three sectors along the pH gradient are attributable to pH/CO2 rather than other environmental differences among the sectors.
• AssumptionRests on an assumption: The species present in the acidified areas are not solely recruits from outside populations, so their presence indicates tolerance.
• AssumptionRests on an assumption: The autumn 2007 sampling is representative of the macroalgal community response to pH, not confounded by seasonal variation.

Classified as probably not a substantial claim.

Turf algae are usually considered opportunistic species that are resilient to ocean acidification.

“despite the fact that these are usually considered opportunistic species that are resilient to ocean acidification (Kleypas et al., 2006).”

• cites Kleypas et al., 2006Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Erect calcareous algae typically host a high biodiversity of associated fauna and flora.

“and typically host a high biodiversity of associated fauna and flora (Nelson, 2009).”

• cites Nelson, 2009Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

The biplot displays a typical horseshoe shape because of nonlinear relationships among species, for example, due to competition for space and light.

“The biplot displays a typical horseshoe shape because of nonlinear relationships among species, for example, due to competition for space and light.”

Probably not a substantial claim: may not pass S3 (load-bearing).

The unique occurrence of S. vulgare in the most acidified zone might relate to a lack of grazing by sea urchins.

“The unique occurrence of S. vulgare in the most acidified zone (Buia, unpublished data) might relate to a lack of grazing by sea urchins”

• cites Buia, unpublished dataNot checked yet

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• cites Miles et al., 2007 sourceNot checked yet

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• cites Hall-Spencer et al., 2008 sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

Crustose calcareous forms may benefit from chemical buffering in the benthic boundary layer.

“which may benefit from chemical buffering in the benthic boundary layer.”

Probably not a substantial claim: may not pass S3 (load-bearing).

Some parts of an organism's life history can be more vulnerable to the effects of ocean acidification than others.

“given that some parts of an organism's life history can be more vulnerable to the effects of ocean acidification than others (e.g., Ellis et al., 2009).”

• cites Ellis et al., 2009Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

The data on selective effects of high CO2 levels on seaweed reproduction are preliminary.

“Our data on the selective effects of high CO 2 levels on seaweed reproduction are preliminary and worthy of further investigation”

May combine two claims.

Rising CO2 levels will alter local ecosystems, including food web dynamics and the cycling of carbon and nutrients.

“indicates that rising CO 2 levels will alter local ecosystems, including food web dynamics and the cycling of carbon and nutrients.”

• AssumptionRests on an assumption: The pH gradient at the volcanic vents is a valid analogue for future ocean acidification conditions.
• AssumptionRests on an assumption: The observed differences in macroalgal communities along the pH gradient are caused primarily by elevated CO2/low pH rather than by other covarying environmental factors (e.g., temperature, nutrients, grazing, pollution).

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

Our paper adds to similar field studies on the effects of ocean acidification on seagrass algal epiphytes, foraminiferan community structure, invertebrate settlement, and bryozoan calcification, all of which indicate major ecological shifts as CO2 levels rise.

“Our paper adds to similar field studies on the effects of ocean acidification on seagrass algal epiphytes (Martin et al., 2008), foraminiferan community structure (Dias et al., 2010) invertebrate settlement (Cigliano et al., 2010), and bryozoan calcification (Rodolfo-Metalpa et al., 2010), all of which indicate major ecological shifts as CO 2 levels rise.”

• cites Martin et al., 2008 sourceNot checked yet

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• cites Dias et al., 2010Not checked yet

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• cites Cigliano et al., 2010Not checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

These two genera (Cystoseira and Sargassum) often dominate Mediterranean phytobenthic assemblages.

“These two genera often dominate Mediterranean phytobenthic assemblages but have steadily declined in abundance since the 1940s (Thibaut et al., 2005).”

• cites Thibaut et al., 2005 sourceNot checked yet

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Probably not a substantial claim: may not pass S3 (load-bearing).

Erect calcareous algae are often important for calcareous sediment production.

“Erect calcareous algae are often important for calcareous sediment production”

• cites Nelson, 2009Not checked yet

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