The effects of UVB radiation on the different developmental stages of the carrageenan-producing red alga Iridaea cordata were evaluated considering: (1) carpospore and discoid germling mortality; (2) growth rates and morphology of young tetrasporophytes; and (3) growth rates and pigment content of field-collected plant fragments. Unialgal cultures were submitted to 0.17, 0.5, or 0.83 Wm −2 of UVB radiation for 3 h per day. The general culture conditions were as follows: 12 h light/12 h dark cycles; irradiance of 55µmol photon . per square meter per second; temperature of 9±1°C; and seawater enriched with Provasoli solution. All UVB irradiation treatments were harmful to carpospores (0:17 W m À2 ¼ 40:9 AE 6:9%, 0:5 W m À2 ¼ 59:8 AE 13:4%, 0:83 W m À2 ¼ 49 AE 17:4% mortality in 3 days). Even though the mortality of all discoid germlings exposed to UVB radiation was unchanged when compared to the control, those germlings exposed to 0.5 and 0.83 Wm −2 treatments became paler and had smaller diameters than those cultivated under control treatment. Decreases in growth rates were observed in young tetrasporophytes, mainly in 0.5 and 0.83 Wm −2 treatments. Similar effects were only observed in fragments of adult plants cultivated at 0.83 Wm −2 . Additionally, UVB radiation caused morphological changes in fragments of adult plants in the first week, while the young individuals only displayed this pattern during the third week. The verified morphological alterations in I. cordata could be interpreted as a defense against UVB by reducing the area exposed to radiation. However, a high level of radiation appears to produce irreparable damage, especially under longterm exposure. Our results suggest that the sensitivity to ultraviolet radiation decreases with increased algal age and that the various developmental stages have different responses when exposed to the same doses of UVB radiation.

Short-term ecophysiological and biochemical responses of Cystoseira tamariscifolia and Ellisolandia elongata to changes in solar irradiance and nutrient levels were analyzed in situ in oligotrophic coastal waters by transferring macroalgae collected at 0.5 and 2.0 m depth and exposing them to 2 irradiance levels (100 and 70% of surface irradiance) and nutrient conditions (nutrient-enriched and non-enriched). Both species were affected by changes in irradiance and nutrient levels. Few interactive effects between these 2 physical stressors were found, suggesting major additive effects on both species. C. tamariscifolia collected at 0.5 m and exposed to 70% irradiance had the highest maximal electron transport rate (ETR max ), saturated irradiance (Ek ETR ) and chl a content and the lowest antioxidant activity. Under the same conditions, E. elongata had increased Ek ETR , antheraxanthin and β-carotene content. At 100% irradiance, C. tamariscifolia collected at 2.0 m had higher maximal quantum yield (F v /F m ), photosynthetic efficiency (α ETR ), ETR max , maximal non-photochemical quenching (NPQ max ), saturation irradiance for NPQ (Ek NPQ ), and antheraxanthin and polyphenol content increased, whereas in E. elongata only α ETR increased. In nutrient-enriched conditions, phenolic compounds, several carotenoids and N content increased in C. tamariscifolia at both depths. E. elongata from 2.0 m depth at 100% irradiance and nutrient-enriched conditions showed increased N content and total mycosporine-like amino acids (MAAs). Our results show rapid photophysiological responses of C. tamariscifolia to variations in in situ irradiance and nutrient conditions, suggesting efficient photoacclimation to environmental changes. In E. elongata, F v /F m and ETR max did not change in the transplant experiment; in contrast, N content, pigment and MAAs (biochemical variables) changed. The responses of these macroalgae to nutrient enrichment indicate oligotrophic conditions at the study site and environmental stress.

Short-term variations of mycosporine-like amino acids (MAAs) in Pyropia columbina (Montage) W.A. Nelson exposed to nitrate (NO3 -) enrichment under different outdoor light treatments during the spring ozone depletion of 2008 in Punta Arenas (Chile) were investigated. Segments of P. columbina thalli were cultivated under three treatments of solar radiation without or with NO3 - supply (0.38 mmol l-1): PAR (P), PAR+UVA (PA), and PAR+UVA+UVB (PAB). Samples were taken at 8:00 h (initial value), 9:30, 12:30, 15:30, and 18:00 h on November 8 and at 9:00 h on November 9 (recovery period). A complex dynamic of MAAs affected by light quality and NO3 - supply was observed. During the light period, the highest content of MAAs was reached under PAB and NO3 - enrichment, whereas MAAs increased during the recovery period in P and PAB with no NO3 - supply. Five MAAs were identified: porphyra-334, shinorine, asterina-330, palythine, and mycosporine-glycine. The hourly accumulation of each MAA varied mainly according to the time of exposure and NO3 - supply. In general, the percentage of porphrya-334 increased, whereas the other MAAs decreased during the exposure period. These results suggest that MAA content in P. columbina varied in the short-term (hours) and the changes were related to the solar irradiance received and NO3 - availability.

UV-absorbing compounds, such as mycosporine-like amino acids (MAAs), are a group of secondary metabolites present in many marine species, including red seaweeds. In these organisms, the content and proportion of the composition of MAAs vary, depending on the species and several environmental factors. Its high cosmetic interest calls for research on the content and composition of MAAs, as well as the dynamics of MAAs accumulation in seaweeds from different latitudes. Therefore, this study aimed to survey the content of UV-absorbing MAAs in three Subantarctic red seaweeds during a seasonal cycle. Using spectrophotometric and HPLC techniques, the content and composition of MAAs of intertidal Iridaea tuberculosa, Nothogenia fastigiate, and Corallina officinalis were assessed. Some samples were also analyzed using high-resolution mass spectrometry coupled with HPLC-ESI-MS in order to identify more precisely the MAA composition. I. tuberculosa exhibited the highest MAA values (above 1 mg g−1 of dried mass weight), while C. officinalis showed values not exceeding 0.4 mg g−1. Porphyra-334 was the main component in N. fastigiata, whereas I. tuberculosa and C. officinalis exhibited a high content of palythine. Both content and composition of MAAs varied seasonally, with high concentration recorded in different seasons, depending on the species, i.e., winter (I. tuberculosa), spring (N. fastigiata), and summer (C. officinalis). HPLC-ESI-MS allowed us to identify seven different MAAs. Two were recorded for the first time in seaweeds from Subantarctic areas (mycosporine-glutamic acid and palythine-serine), and we also recorded an eighth UV-absorbing compound which remains unidentified.

The effects of nitrate supply on growth, pigments, mycosporine-like amino acids (MAAs), C:N ratios and carrageenan yield were investigated in Mazzaella laminarioides cultivated under solar radiation. This species is economically important in southern Chile where an increase of nitrogen in coastal waters is expected as a consequence of salmon aquaculture activity. Apical segments were cultivated in enriched seawater with five different NO À 3 concentrations (0, 0.09, 0.18, 0.38 and 0.75 mM) during 18 days. Although phycoerythrin and phycocyanin content, as well as C:N ratios, were reduced in the control treatment (without NO À 3 supply), when compared to NO À 3 treatments, total MAA concentration, carrageenan yield and growth rates were similar in all tested conditions. Nevertheless, during the experiment, an important synthesis of mycosporine-glycine took place in a nitrate concentrationdependent manner, with accumulation being saturated around 0.18 mM of nitrate. These results indicate that exposure to high NO À 3 concentration of more than 100 times the values observed in the nature did not impair the photoprotection system, as determined by MAAs, nor did it have a deleterious effect on growth or carrageenan yield of M. laminarioides, a late successional species from Chile.

No abstract

The effects of UVB radiation on the growth of macroalgal thalli were evaluated using tetrasporophytic fronds of the Rhodophytes Gigartina skottsbergii, Sarcothalia crispata and Mazzaella laminarioides. The tetrasporophytic fronds were collected from nature and the tetrasporophyte sporelings grown in a temperature regulated chamber at 8 ± 2 • C with a 12L:12D (Light: Dark) photoperiod, Photosynthetically Active Radiation (PAR) of 55 μmol photons m −2 s −1 and seawater enriched with 20 mL L −1 of Provasoli medium. We exposed the thalli of these macroalgae to PAR (55 μmol photons m −2 s −1 ) and three treatments using a combination of PAR with three different levels of UVB radiation (0.10, 0.15 and 0.23 W m −2 for G. skottsbergii and S. crispata and 0.02, 0.05 and 0.10 W m −2 for M. laminarioides) during a period of 71 days. Growth of thalli was quantified by measuring their length using digitized photographs of samples.Important differences were detected in the growth of individuals cultured under the effects of UVB radiation, when compared to the control (i.e. plants exposed to PAR only). In the case of G. skottsbergii and S. crispata higher levels of UVB radiation resulted in slower growth of thalli. In nearly all measurements for the first two species, UVB radiation levels of 0.1 W m −2 induced differences in thallus growth, while for M. laminarioides levels of UVB radiation of 0.1 W m −2 were effective only after a prolonged period of exposure.Differential effects of UVB radiation on G. skottsbergii, S. crispata and M. laminarioides could interfere with the natural populations of these economically important macroalgal species in southern Chile, where they occur under the annual influence of the Antarctic Ozone Hole and the general thinning of the ozone layer.

No abstract