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Three macroalgal species belonging to Chlorophyta (Ulva rigida), Rhodophyta (Ellisolandia elongata) and Phaeophyceae (Heterokontophyta; Cystoseira tamariscifolia), natu- rally growing at the same shore level and representing 3 morpho-functional groups, were exposed to short-term changes in temperature under different carbon and nitrogen regimes. Experiments were conducted in outdoor tanks at 4 combinations of carbon and nitrogen levels under reduced solar radiation. In vivo chl a fluorescence parameters and pigment contents were monitored to assess diurnal physiological responses and potential for recovery. Strong fluctuations in chl a flu- orescence parameters, but not in chl a content, were observed in response to diurnal variation in solar radiation and light climate within the tanks; sensitivity varied between algal species and, in some cases, depended on the carbon and nitrogen regime. Nitrogen uptake was similarly high in U. rigida and E. elongata and lowest in C. tamariscifolia. In U. rigida and E. elongata, chl a con- centrations decreased after high-carbon treatments. Effective photosystem II quantum efficiency was reduced in all species at noon, and lowest in C. tamariscifolia. The results highlight the com- plexity of physiological short-term acclimations which were most likely linked to biochemical changes at the cellular level. Long-term experiments are required in future for more comprehen- sive investigation of the observed interactive effects of the different environmental parameters.

The effects of increased photosynthetic active radiation (PAR), UV radiation (UVR), and nutrient supply on photosynthetic activity, pigment content, C:N ratio and biomass yield were studied in tank cultivated Gracilaria conferta (Rhodophyta). Electron transport rate (ETR) and biliprotein content were higher under high nutrient supply (HNS), obtained from fishpond effluents, compared to low nutrient supply (LNS), in contrast to mycosporine-like amino acids (MAAs) dynamic. The high MAA content in LNS-algae could be explained by higher UVR penetration in the thallus and by the competition for the use of nutrients with other processes. Effective quantum yield decreased after short-term exposure to high irradiance whereas full recovery in shade was produced only under slightly heat shock. UVA radiation provoked an additional decrease in photosynthesis under high water temperature. UVB radiation reversed UVA's negative effect mainly with HNS. Results support that nutrient-sufficiency help G. conferta to resist environmental changes as short-term temperature increase.

In order to test their usability in vertical structured, integrated aquaculture approaches, the light acclimation characteristics of three commercially important red algal species of southern Chile were investigated. Light affinity, maximum photosynthesis and respiration rate were measured. Analyses of the non-photochemical quenching and pigment contents were conducted. This work is focused on the differences between field-grown algae exposed to the full range of irradiance variability in the field caused by tidal changes, and algae grown in buoyant long-line aquacultures at different depths (1, 3, 5 and 7 m). The acclimation patterns of the respective species were clearly related to the irradiance regime of their natural habitat. However, all species were also able to acclimate their photosynthesis characteristics to conditions exceeding the irradiance ranges of their natural habitat. The results revealed that the three species followed different acclimation strategies: Gracilaria chilensis was almost completely lacking physiological acclimation. Sarcothalia crispata exhibited a combination of both morphological as well as physiological acclimation processes, while Mazzaella laminarioides exclusively used physiological acclimation mechanisms. Further differences were found with respect to their ability to survive periods of supersaturating irradiation. As expected, the subtidal S. crispata was unable to acclimate to large irradiance fluctuations in shallow water, whereas the other two species adjusted their capability for dynamic photoinhibition to the respective irradiance climate. The implications of these acclimation patterns for aquaculture purposes are discussed and recommendations for appropriate positioning of these species in vertical structured aquaculture are given.

Although charophytes have been studied from South America since the 19th century, large regional gaps in their distribution and manifold taxonomic problems hinder a trans-Andean comparison of charophyte diversity. In total, 14 charophyte species have been previously published for Chile. This number is very low compared to countries east of the Andean barrier. Here we present the results of a series of expeditions that gathered data concerning charophyte distribution in Chile between Patagonia and the Peruvian border. About one-third of the several hundred sites investigated between 2011 and 2013 exhibited rich charophyte communities. Accordingly, the number of species known for Chile has increased to a total of 31 and includes two species (Chara fulgens and Nitella asagrayana) reported from South America for the first time. Our results show some marked differences between charophyte communities west and east of the Andes, notably the absence of the Willdenowia group in the region west of the Andes. Possible reasons for this discrepancy are discussed, and different types of charophyte habitats are characterized in order to widen our knowledge about global distribution and dispersal routes of charophytes.

Short-term effects of increasing pCO(2); 380 ppm (LC) vs. 700 ppm (HC); at different nitrogen levels; 5 mu M nitrate (LN) vs. 50 mu M (HN); on the contents of protein, mycosporine-like amino acids (MAAs), phenolic compounds and total fatty acids, antioxidant activity, calcification and C: N ratios were analyzed in 3 eulittoral Mediterranean macroalgae with different bio-optical characteristics and carbon assimilation efficiencies: Cystoseira tamariscifolia (Heterokontophyta), Ulva rigida (Chlorophyta) and Ellisolandia elongata (Rhodophyta). After acclimation to different pCO(2) and nitrogen conditions for 6 d, the algae were subjected to a 4 degrees C temperature increase for 3 d. Increasing temperature and pCO(2) produced alterations in the biochemical composition of the 3 macroalgae. Short-term variations of protein levels were observed in U. rigida, with clearly decreased values in the HCLN treatment. In C. tamariscifolia, protein decreased after the temperature increase but only under LC. The interaction of temperature and N affected phenolic compounds only in U. rigida and the content of MAAs in E. elongata. The functional patterns of the 3 macroalgae in response to the pCO(2), nitrogen and temperature regimes may be explained in terms of their bio-optical characteristics and antioxidant activity. The vulnerability and acclimation of the 3 species to the expected variations of climate change factors are discussed.

Remane’s species-minimum concept, which states that the lowest number of taxa occurs at the horohalinicum (5–8 psu), was tested by investigating macroalgal diversity on hard substrates along the natural salinity gradient in the Baltic Sea. Field data on species occurrence and abundance were collected by SCUBA diving along 10 transects of the Finnish, Swedish and German coasts, covering a salinity range from 3.9 to 27 psu. Macroalgal species numbers declined steadily with salinity, decreasing until 7.2 psu was reached, but in the horohalinicum, a marked reduction of species number and a change in diversity were indicated by the Shannon index and evenness values. The non-linear decrease in macroalgal diversity at 5–8 psu and the lack of increase in species numbers at salinities below 5 psu imply a restricted applicability of Remane’s species-minimum concept to macroalgae.

Thallus absorptance, daily courses of maximal quantum yields of chlorophyll fluores- cence of photosystem II (Fv/Fm) and electron transport rates (ETR) were determined in 3 macroalgae (Hypnea spinella, Rhodophyta; Sargassum vulgare, Phaeophyta; and Ulva lactuca, Chlorophyta) collected from a low nutrient supply (LNS) ecosystem (Red Sea, Gulf of Aqaba, Eilat, Israel). In addi- tion, U. lactuca grown previously in high nutrient supply (HNS) fishpond effluents was used to eval- uate the effect of nutrient enrichment on photosynthesis. Short-term (2 d) and mid-term (5 d) effects of both photosynthetically active radiation (PAR) and full solar irradiance (PAB: PAR+UVA+UVB) at 3 solar irradiance treatments (no neutral filters, no NF; 2 neutral filter layers, 2NF; and 4 neutral filter layers, 4NF simulating levels of irradiance at 5, 10 and 20 m depth respectively) were evaluated in algae incubated with running seawater. Significant effects of time (variation throughout the day) and irradiance (number of neutral filters) on both Fv/Fm and ETR were observed. Photoinhibition occurred at noon under the no NF (up to 40% decrease) and 2NF (up to 30% decrease) treatments; however, full recovery in all treatments was reached in the afternoon (dynamic photoinhibition) except in H. spinella. The highest maximum ETR was observed in the no NF treatment despite its strongest photoinhibitory effect. The decrease in Fv/Fm at noon was similar to or higher under the PAB than under the PAR treatment alone, depending on the species. Photoinhibition was lower and the maxi- mum ETR was higher in HNS than in LNS U. lactuca, indicating positive effects of nutrient supply on both photosynthesis and photoprotection. The maximum ETRs exhibited by different algae may be related to their zonation in the field and the resulting energy supply.

The effects of nutrient supply on photosynthesis (estimated as chlorophyll fluorescence), chlorophyll content, biomass yield and proximate chemical composition of tank cultivated Ulva lactuca L. (Chlorophyta) were evaluated. To assess the effect of nutrient supply on resistance capacity against short-term stress, algae grown in high nutrient supply (FINS) fishpond effluents and in low nutrient supply (LNS) oligotrophic seawater were transferred to small vessels with increased irradiance of PAR and UV radiation (PAR+UVA and PAR+UVA+UVB using cut-off filters) and increased temperature as compared to culture tanks. Electron transport rate and chlorophyll content were higher in HNS than in LNS algae. Effective quantum yield and chlorophyll content decreased after short-term exposure to high PAR irradiance. Full recovery of photosynthesis in the shade was observed under a moderately higher temperature (Delta+6 degrees C). UVB exposure reduced the negative effect of UVA on photosynthesis and pigment accumulation under temperature stress (Delta+10 degrees C), particularly in FINS algae. Growth under HNS appeared to accelerate acclimation of Ulva lactuca to short-term environmental changes, such as higher temperatures (as in heat waves) and higher UV radiation. Furthermore, nitrogen enrichment reduced the common inhibitory effects of short-term stress such as increased irradiance, UV radiation and temperature on photosynthesis.