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Lack of Physiological Depth Patterns in Conspecifics of Endemic Antarctic Brown Algae: A Trade-Off between UV Stress Tolerance and Shade Adaptation?

Gómez I, Huovinen P - PLoS ONE (2015)

Bottom Line: The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius).These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation.The high contents of phlorotannins and antioxidant potential appear to be strongly responsible for the lack of clear depth patterns in light demand characteristics and UV tolerance.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.

ABSTRACT
A striking characteristic of endemic Antarctic brown algae is their broad vertical distribution. This feature is largely determined by the shade adaptation in order to cope with the seasonal variation in light availability. However, during spring-summer months, when light penetrates deep in the water column these organisms have to withstand high levels of solar radiation, including UV. In the present study we examine the light use characteristics in parallel to a potential for UV tolerance (measured as content of phenolic compounds, antioxidant activity and maximum quantum yield of fluorescence) in conspecific populations of four Antarctic brown algae (Ascoseira mirabilis, Desmarestia menziesii, D. anceps and Himantothallus grandifolius) distributed over a depth gradient between 5 and 30 m. The main results indicated that a) photosynthetic efficiency was uniform along the depth gradient in all the studied species, and b) short-term (6 h) exposure to UV radiation revealed a high tolerance measured as chlorophyll fluorescence, phlorotannin content and antioxidant capacity. Multivariate analysis of similarity indicated that light requirements for photosynthesis, soluble phlorotannins and antioxidant capacity are the variables determining the responses along the depth gradient in all the studied species. The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius). These patterns are consistent with the underwater light penetration that defines two zones: 0-15 m, with influence of UV radiation (1% of UV-B and UV-A at 9 m and 15 m respectively) and a zone below 15 m marked by PAR incidence (1% up to 30 m). These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation. The high contents of phlorotannins and antioxidant potential appear to be strongly responsible for the lack of clear depth patterns in light demand characteristics and UV tolerance.

No MeSH data available.


Related in: MedlinePlus

Effect of UV radiation on the maximal quantum yield of fluorescence (Fv ⁄ Fm) of four Antarctic algae collected to different depths.Algae were exposed for 6 h to PAR+UV-A+UV-B (PAR + UV) and PAR conditions (20 μmol m-2 s-1 for PAR, 3 W m-2 for UV-A and 0.25 W m-2), and returned to control culture conditions under dim PAR for 12 h (recovery). Initial is the time cero before the 6 h exposure to UV radiation. Values are means ± S.D., n = 9. The significant decrease in photosynthesis in the UV treatment relative to PAR (ANOVA and Tukey HSD post hoc test) is indicated.
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pone.0134440.g005: Effect of UV radiation on the maximal quantum yield of fluorescence (Fv ⁄ Fm) of four Antarctic algae collected to different depths.Algae were exposed for 6 h to PAR+UV-A+UV-B (PAR + UV) and PAR conditions (20 μmol m-2 s-1 for PAR, 3 W m-2 for UV-A and 0.25 W m-2), and returned to control culture conditions under dim PAR for 12 h (recovery). Initial is the time cero before the 6 h exposure to UV radiation. Values are means ± S.D., n = 9. The significant decrease in photosynthesis in the UV treatment relative to PAR (ANOVA and Tukey HSD post hoc test) is indicated.

Mentions: Results of Fv/Fm from 6-h UV exposure indicated, overall, high UV tolerance of the studied algae. In A. mirabilis and D. menziesii, the most UV tolerant species, Fv/Fm decreased between 0 and 10% in UV relative to PAR treatment (Fig 5). Decreases in photosynthesis in D. anceps were highly variable in relation with the collection depth: at 20 m photosynthesis practically did not decrease after 6 h exposure to UV radiation, but in algae collected at 10 and 30 m, Fv/Fm was inhibited by 9 and 25%, respectively (>0.05; Fig 5). In H. grandifolius, Fv/Fm decreased 6% in algae collected at 30 m and 11% in algae from 20 m depth (>0.05, Fig 5). In all the studies species, irrespective of their collection depth there was a tendency of a full recovery of photosynthesis after exposure for 12 h to dim light (Fig 5). The factorial ANOVA indicated a significant interaction of depth and UV treatment in A. mirabilis and D. anceps, while in D. menziesii and H. grandifolius, only single effects of both factors on the variability of Fv/Fm were observed (p> 0.01, two-way ANOVA; Table A in S2 Table).


Lack of Physiological Depth Patterns in Conspecifics of Endemic Antarctic Brown Algae: A Trade-Off between UV Stress Tolerance and Shade Adaptation?

Gómez I, Huovinen P - PLoS ONE (2015)

Effect of UV radiation on the maximal quantum yield of fluorescence (Fv ⁄ Fm) of four Antarctic algae collected to different depths.Algae were exposed for 6 h to PAR+UV-A+UV-B (PAR + UV) and PAR conditions (20 μmol m-2 s-1 for PAR, 3 W m-2 for UV-A and 0.25 W m-2), and returned to control culture conditions under dim PAR for 12 h (recovery). Initial is the time cero before the 6 h exposure to UV radiation. Values are means ± S.D., n = 9. The significant decrease in photosynthesis in the UV treatment relative to PAR (ANOVA and Tukey HSD post hoc test) is indicated.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4529099&req=5

pone.0134440.g005: Effect of UV radiation on the maximal quantum yield of fluorescence (Fv ⁄ Fm) of four Antarctic algae collected to different depths.Algae were exposed for 6 h to PAR+UV-A+UV-B (PAR + UV) and PAR conditions (20 μmol m-2 s-1 for PAR, 3 W m-2 for UV-A and 0.25 W m-2), and returned to control culture conditions under dim PAR for 12 h (recovery). Initial is the time cero before the 6 h exposure to UV radiation. Values are means ± S.D., n = 9. The significant decrease in photosynthesis in the UV treatment relative to PAR (ANOVA and Tukey HSD post hoc test) is indicated.
Mentions: Results of Fv/Fm from 6-h UV exposure indicated, overall, high UV tolerance of the studied algae. In A. mirabilis and D. menziesii, the most UV tolerant species, Fv/Fm decreased between 0 and 10% in UV relative to PAR treatment (Fig 5). Decreases in photosynthesis in D. anceps were highly variable in relation with the collection depth: at 20 m photosynthesis practically did not decrease after 6 h exposure to UV radiation, but in algae collected at 10 and 30 m, Fv/Fm was inhibited by 9 and 25%, respectively (>0.05; Fig 5). In H. grandifolius, Fv/Fm decreased 6% in algae collected at 30 m and 11% in algae from 20 m depth (>0.05, Fig 5). In all the studies species, irrespective of their collection depth there was a tendency of a full recovery of photosynthesis after exposure for 12 h to dim light (Fig 5). The factorial ANOVA indicated a significant interaction of depth and UV treatment in A. mirabilis and D. anceps, while in D. menziesii and H. grandifolius, only single effects of both factors on the variability of Fv/Fm were observed (p> 0.01, two-way ANOVA; Table A in S2 Table).

Bottom Line: The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius).These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation.The high contents of phlorotannins and antioxidant potential appear to be strongly responsible for the lack of clear depth patterns in light demand characteristics and UV tolerance.

View Article: PubMed Central - PubMed

Affiliation: Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.

ABSTRACT
A striking characteristic of endemic Antarctic brown algae is their broad vertical distribution. This feature is largely determined by the shade adaptation in order to cope with the seasonal variation in light availability. However, during spring-summer months, when light penetrates deep in the water column these organisms have to withstand high levels of solar radiation, including UV. In the present study we examine the light use characteristics in parallel to a potential for UV tolerance (measured as content of phenolic compounds, antioxidant activity and maximum quantum yield of fluorescence) in conspecific populations of four Antarctic brown algae (Ascoseira mirabilis, Desmarestia menziesii, D. anceps and Himantothallus grandifolius) distributed over a depth gradient between 5 and 30 m. The main results indicated that a) photosynthetic efficiency was uniform along the depth gradient in all the studied species, and b) short-term (6 h) exposure to UV radiation revealed a high tolerance measured as chlorophyll fluorescence, phlorotannin content and antioxidant capacity. Multivariate analysis of similarity indicated that light requirements for photosynthesis, soluble phlorotannins and antioxidant capacity are the variables determining the responses along the depth gradient in all the studied species. The suite of physiological responses of algae with a shallower distribution (A. mirabilis and D. menziesii) differed from those with deeper vertical range (D. anceps and H. grandifolius). These patterns are consistent with the underwater light penetration that defines two zones: 0-15 m, with influence of UV radiation (1% of UV-B and UV-A at 9 m and 15 m respectively) and a zone below 15 m marked by PAR incidence (1% up to 30 m). These results support the prediction that algae show a UV stress tolerance capacity along a broad depth range according to their marked shade adaptation. The high contents of phlorotannins and antioxidant potential appear to be strongly responsible for the lack of clear depth patterns in light demand characteristics and UV tolerance.

No MeSH data available.


Related in: MedlinePlus