Search

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.

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.

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.