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- Increased vulnerability of Zostera noltii to stress caused by low light and elevated ammonium levels under phosphate deficiencyPublication . Brun, Fernando G.; Olive, Irene; Malta, Erik-jan; Vergara, Juan J.; Hernandez, Ignacio; Lucas Perez-Llorens, J.The effects of light and ammonium levels on net production, fluorescence parameters and non-structural carbohydrates of the seagrass Zostera noltii under different phosphate conditions were studied. A fully factorial design was used with light (low/high levels), ammonium supply and phosphate preculture conditions of the plants as the experimental variables. Both ammonium supply and low light caused negative and synergistic effects on net production, while ammonium toxicity was more severe at high light levels; in this case, it was independent of the non-structural carbohydrate (sucrose and starch) content. Preculturing of plant with added phosphate alleviated the ammonium toxicity, and also attenuated the negative production balance of plants grown at low light levels. The results indicated that phosphate preculture ameliorated the plant's short-term response against the assayed stressors (low light, high ammonium) significantly. An overall consumption of non-structural carbohydrates in response to environmental stressors was recorded throughout the experiment, indicating the importance of carbon and phosphorus reserves to cope with adverse conditions. ln addition, phosphate deficiency increased the vulnerability of plants, which could have negative ecological consequences for seagrass species thriving under phosphate deficiency conditions, or in developing seagrass transplantation programs.
- Acclimation of Red Sea macroalgae to solar radiation: photosynthesis and thallus absorptancePublication . Figueroa, Felix L.; Martinez, Brezo; Israel, Alvaro; Neori, Amir; Malta, Erik-jan; Ang, Put, Jr.; Inken, Sven; Marquardt, Ronny; Rachamim, Tamar; Arazi, Uri; Frenk, Sammy; Korbee, NathalieThallus absorptance, daily courses of maximal quantum yields of chlorophyll fluorescence of photosystem II (F-v/F-m) 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 addition, U. lactuca grown previously in high nutrient supply (HNS) fishpond effluents was used to evaluate 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 F-v/F-m 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 F-v/F-m 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 maximum 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.
- Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoonPublication . Malta, Erik-jan; Stigter, Tibor Y.; Pacheco, André; Carvalho Dill, Amélia; Tavares, Diogo; Santos, RuiThe seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.
- Effects of nutrient supply on photosynthesis and pigmentation in Ulva lactuca (Chlorophyta): responses to short-term stressPublication . Figueroa, Felix L.; Israel, Alvaro; Neori, Amir; Martinez, Brezo; Malta, Erik-jan; Ang, Put, Jr.; Inken, Sven; Marquardt, Ronny; Korbee, NathalieThe 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.
- Nitrogen load and irradiance affect morphology, photosynthesis and growth of Caulerpa prolifera (Bryopsidales : Chlorophyta)Publication . Malta, Erik-jan; Ferreira, D. G.; Vergara, J. J.; Perez-Llorens, J. L.The effect of nitrogen (N) load and irradiance on morphology, growth and photosynthetic performance was studied in the green macroalga Caulerpa prolifera (Forsskal) J. V. Lamouroux from the Gulf of Cddiz (south Spain). Constant growth rates were obtained for thalli growing at different N loads, which could be fitted to tissue N using the Droop equation, rendering a maximum growth rate of 0.09 d(-1), a minimum tissue N level of 1.71 % dry weight (DW) and a critical tissue N of 5.2 % DW. N limitation had no effects on F-v/F-m (maximum quantum yield of chlorophyll a fluorescence). Stolon production was significantly highest at low N loads; a reverse trend was observed for assimilator production. In a second experiment, algae were subjected to combinations of high and low N loads (HN and LN) and irradiance (HL and LL) levels. Highest growth rates were observed in the HNLL treatment, whereas the reverse combination rendered the lowest growth rate. High irradiance and high N load both led to increased biomass allocation to assimilators; at low N, the bulk of the biomass (> 75 % in the HLLN treatment) was allocated to the stolons. HN had a positive effect on F-v/F-m and HL had a negative effect. HL algae had a higher capacity for non-photochemical quenching. Despite its prolific nature, C. prolifera should be characterised as a slow-growing, but highly nitrophilic alga which has the capacity to forage for nutrients by allocating biomass to the stolons.