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Phytoplankton nutrient limitation in the Ria Formosa

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Rita Domingues
Rita Domingues

This document summarizes a study on phytoplankton nutrient limitation in the Ria Formosa coastal lagoon in Portugal. The study found that phytoplankton growth was nitrogen-limited throughout the year, with nitrogen uptake and growth increasing with nitrogen additions even at concentrations up to 12 亮M. The results indicate the need to consider seasonal variations and different limiting concentrations for different phytoplankton species when establishing nutrient criteria for eutrophication assessments. The document also describes several other experiments and effects analyzed as part of the overall study.

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Phytoplankton nutrient limitation in the Ria Formosa: implications for eutrophication assessment Rita B. Domingues1,2, C叩tia C. Guerra1, Ana B. Barbosa1, Helena M. Galv達o1 1 Centro de Investiga巽達o Marinha e Ambiental, Universidade do Algarve 2 Centro de Oceanografia, Faculdade de Ci棚ncias, Universidade de Lisboa
What is phytoplankton? unicellular, photosynthetic prokaryotic and eukaryotic organisms whose powers of locomotion are such that they drift freely in the water column diatoms, dinoflagellates, coccolithophores, cyanobacteria, Why is phytoplankton so important? phytoplankton is the main primary producer in most aquatic ecosystems phytoplankton is a fundamental player in many ecosystem processes phytoplankton is a gauge of ecological condition and change phytoplankton can be used to predict the functioning of aquatic ecosystems and ecosystem responses to natural and anthropogenic perturbations
Studying phytoplankton is not straightforward the ecological role played by different phytoplankton groups and species varies significantly phytoplankton in coastal ecosystems is undergoing marked changes (biomass, composition, phenology) linked to local anthropogenic influences and climate change links between environmental and phytoplankton changes are difficult to establish Importance of nutrients Nutrient availability is a key driver of phytoplankton dynamics Nutrient limitation is a central question for eutrophication control How do nutrients affect phytoplankton growth, diversity and production? Assessment of the impact of nutrient enrichment (eutrophication) and subsequent nutrient reduction strategies
Why the Ria Formosa coastal lagoon? multiple anthropogenic influences very vulnerable to climate change phytoplankton regulation is a critical aspect in a fast-changing ecosystem lack of information on phytoplankton regulation in the Ria Formosa studies are mostly descriptive Project PHYTORIA Environmental Regulation of Phytoplankton in the Ria Formosa coastal lagoon (PTDC/MAR/114380/2009) Goals to determine the limiting nutrients for phytoplankton growth and their seasonal variation in the Ria Formosa coastal lagoon to understand the effects of potential anthropogenic nutrient enrichment on phytoplankton structure in the Ria Formosa
Approaches nutrient addition experiments in 2 L microcosms containing natural phytoplankton assemblages from the Ria Formosa coastal lagoon autumn, winter, spring, summer addition of dissolved inorganic macronutrients, alone and in combinations, in a single, saturating pulse control +NO3- +NH4+ +P +Si +NP +SiN +SiP +NPSi in situ incubation (under in situ T and light) phytoplankton growth (epifluorescence and inverted microscopy) nutrient consumption
Results N consumption 25 13.5 Autumn 11.5 Spring N uptake (袖M d-1) 20 9.5 N uptake (袖M d-1) 15 7.5 5.5 10 3.5 5 1.5 -0.5 0 -2.5 -5 35 30 Summer 30 25 Winter N uptake (袖M d-1) 25 N uptake (袖M d-1) 20 20 15 15 10 10 5 5 0 0 -5 -5 higher N uptake in N-enriched treatments in relation to the control indicate N limitation phytoplankton in the Ria Formosa is N-limited throughout the year NO3- concentrations up to 12 袖M were limiting to phytoplankton growth
Results Establishing nutrient criteria Application of nutrient limitation criteria based on Ks problems Ks obtained for unialgal cultures under equilibrium conditions Ks vary temporally, spatially, inter- and intraspecifically Establishment of nutrient criteria - should consider the seasonal variation of phytoplankton community (different spp. are limited in different ways by different nutrients) - should consider that limiting concentrations dont have to be necessarily low concentrations (e.g., in the Guadiana estuary N is limiting up to 20 袖M: Domingues et al., 2011) B 0,5 ** Community net growth rate (d -1) 0,45 spring ** Initial N = 22 袖M 0,4 0,35 0,3 ** ** 0,25 0,2 0,15 0,1 0,05 0 control N P Si NP SiN SiP NPSi
Results Phytoplankton net growth 1.1 Summer Community net growth rate (d-1) 0.9 Increased nutrient uptake 0.7 0.5 0.3 phytoplankton growth 0.1 -0.1 -0.3 -0.5 control Nit Amm P Si NP SiN SiP NPSi 0.45 0.4 Winter luxury consumption 0.35 Net growth rate (d-1) 0.3 0.25 0.2 0.15 0.1 0.05 0 control Nit Amm P Si NP SiN SiP NPSi
Bottle effects on microcosm Effects of nutrient enrichment on Phytoplankton mortality in the experiments bacterioplankton in the RF Ria Formosa Effects of ultraviolet radiation and CO2 increase on winter phytoplankton assemblages in a temperate coastal lagoon (Ria Formosa) Rita B. Domingues, Ana B. Barbosa, Vanda Brotas 18h15
Thank You for Your Attention! Acknowledgements FCT project Phytoria Environmental regulation of phytoplankton in the Ria Formosa coastal lagoon (PTDC/MAR/114380/2009) Postdoctoral fellowship awarded to RBD (SFRH/BPD/68688/2010)

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Phytoplankton nutrient limitation in the Ria Formosa

  • 1. Phytoplankton nutrient limitation in the Ria Formosa: implications for eutrophication assessment Rita B. Domingues1,2, C叩tia C. Guerra1, Ana B. Barbosa1, Helena M. Galv達o1 1 Centro de Investiga巽達o Marinha e Ambiental, Universidade do Algarve 2 Centro de Oceanografia, Faculdade de Ci棚ncias, Universidade de Lisboa
  • 2. What is phytoplankton? unicellular, photosynthetic prokaryotic and eukaryotic organisms whose powers of locomotion are such that they drift freely in the water column diatoms, dinoflagellates, coccolithophores, cyanobacteria, Why is phytoplankton so important? phytoplankton is the main primary producer in most aquatic ecosystems phytoplankton is a fundamental player in many ecosystem processes phytoplankton is a gauge of ecological condition and change phytoplankton can be used to predict the functioning of aquatic ecosystems and ecosystem responses to natural and anthropogenic perturbations
  • 3. Studying phytoplankton is not straightforward the ecological role played by different phytoplankton groups and species varies significantly phytoplankton in coastal ecosystems is undergoing marked changes (biomass, composition, phenology) linked to local anthropogenic influences and climate change links between environmental and phytoplankton changes are difficult to establish Importance of nutrients Nutrient availability is a key driver of phytoplankton dynamics Nutrient limitation is a central question for eutrophication control How do nutrients affect phytoplankton growth, diversity and production? Assessment of the impact of nutrient enrichment (eutrophication) and subsequent nutrient reduction strategies
  • 4. Why the Ria Formosa coastal lagoon? multiple anthropogenic influences very vulnerable to climate change phytoplankton regulation is a critical aspect in a fast-changing ecosystem lack of information on phytoplankton regulation in the Ria Formosa studies are mostly descriptive Project PHYTORIA Environmental Regulation of Phytoplankton in the Ria Formosa coastal lagoon (PTDC/MAR/114380/2009) Goals to determine the limiting nutrients for phytoplankton growth and their seasonal variation in the Ria Formosa coastal lagoon to understand the effects of potential anthropogenic nutrient enrichment on phytoplankton structure in the Ria Formosa
  • 5. Approaches nutrient addition experiments in 2 L microcosms containing natural phytoplankton assemblages from the Ria Formosa coastal lagoon autumn, winter, spring, summer addition of dissolved inorganic macronutrients, alone and in combinations, in a single, saturating pulse control +NO3- +NH4+ +P +Si +NP +SiN +SiP +NPSi in situ incubation (under in situ T and light) phytoplankton growth (epifluorescence and inverted microscopy) nutrient consumption
  • 6. Results N consumption 25 13.5 Autumn 11.5 Spring N uptake (袖M d-1) 20 9.5 N uptake (袖M d-1) 15 7.5 5.5 10 3.5 5 1.5 -0.5 0 -2.5 -5 35 30 Summer 30 25 Winter N uptake (袖M d-1) 25 N uptake (袖M d-1) 20 20 15 15 10 10 5 5 0 0 -5 -5 higher N uptake in N-enriched treatments in relation to the control indicate N limitation phytoplankton in the Ria Formosa is N-limited throughout the year NO3- concentrations up to 12 袖M were limiting to phytoplankton growth
  • 7. Results Establishing nutrient criteria Application of nutrient limitation criteria based on Ks problems Ks obtained for unialgal cultures under equilibrium conditions Ks vary temporally, spatially, inter- and intraspecifically Establishment of nutrient criteria - should consider the seasonal variation of phytoplankton community (different spp. are limited in different ways by different nutrients) - should consider that limiting concentrations dont have to be necessarily low concentrations (e.g., in the Guadiana estuary N is limiting up to 20 袖M: Domingues et al., 2011) B 0,5 ** Community net growth rate (d -1) 0,45 spring ** Initial N = 22 袖M 0,4 0,35 0,3 ** ** 0,25 0,2 0,15 0,1 0,05 0 control N P Si NP SiN SiP NPSi
  • 8. Results Phytoplankton net growth 1.1 Summer Community net growth rate (d-1) 0.9 Increased nutrient uptake 0.7 0.5 0.3 phytoplankton growth 0.1 -0.1 -0.3 -0.5 control Nit Amm P Si NP SiN SiP NPSi 0.45 0.4 Winter luxury consumption 0.35 Net growth rate (d-1) 0.3 0.25 0.2 0.15 0.1 0.05 0 control Nit Amm P Si NP SiN SiP NPSi
  • 9. Bottle effects on microcosm Effects of nutrient enrichment on Phytoplankton mortality in the experiments bacterioplankton in the RF Ria Formosa Effects of ultraviolet radiation and CO2 increase on winter phytoplankton assemblages in a temperate coastal lagoon (Ria Formosa) Rita B. Domingues, Ana B. Barbosa, Vanda Brotas 18h15
  • 10. Thank You for Your Attention! Acknowledgements FCT project Phytoria Environmental regulation of phytoplankton in the Ria Formosa coastal lagoon (PTDC/MAR/114380/2009) Postdoctoral fellowship awarded to RBD (SFRH/BPD/68688/2010)