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Effects of climate change on phytoplankton
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Effects of climate change on phytoplankton



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  • 1. Effects of ultraviolet radiation and CO2 increase on winterphytoplankton assemblages in a temperate coastal lagoon (Ria Formosa, Portugal) Rita B. Domingues1,2, Ana B. Barbosa1, Vanda Brotas2 1Centro de Investigação Marinha e Ambiental, Universidade do Algarve 2 Centro de Oceanografia, Faculdade de Ciências, Universidade de Lisboa
  • 2. Global Climate Change significant threat to the environment one of the most pressing social concerns of the XXI centuryIndustrial development atmospheric CO2 air temperature destruction ozone layer UV radiationAlterations in climate influence organisms directly – acting on their physiology and phenology indirectly – modifying their environmental stressors Affects the whole community, up to the ecosystem level…Phytoplankton - basilar components of aquatic ecosystems - sensitive ecological indicators of environmental changesKey determinant to detect and forecast ecosystem responses to global climatechange
  • 3. Effects of UV radiation on phytoplankton depends on intensity and spectral composition and interaction with otherenvironmental variables deleterious effects on nutrient uptake, growth, species composition inhibition of photosynthesis damage on nucleic acids overproduction of reactive oxygen species (ROS), leading to oxidative damageEffects of CO2 increase on phytoplankton CO2 increase ocean acidification – dissolution of calcareous structures may enhance phytoplankton production
  • 4. Effects of UVR and CO2 increase on phytoplankton UVR and CO2 act together – interactions between them may produce differentresults than those observed for each individual variable e.g., elevated CO2 may increase sensitivity to UVR; UVR and CO2 may inhibitphotosynthesis effects of UVR and CO2 depend on and interact with other environmentalstressors (temperature, PAR, nutrients, …)Studying the effects of climate change most common approach - unialgal cultures, lab-controlled conditions in situ response of natural phytoplankton communities and effect of climate change alongseasonal biomass cycle are still largely unknown most studies focused on polar and sub-polar areas (destruction ozone layer) coastal ecosystems in temperate regions- provide wide range of ecosystem services and resources- affected by anthropogenic pressures that can exacerbate effects of climate change
  • 5. Ria Formosa coastal lagoon one of the most important coastal ecosystems in Portugal breeding and feeding ground for many bird and fishspecies supports wide range of human activities (fishing,shellfish farming, tourism)  subjected to strong anthropogenic pressures occurrence of harmful algal blooms affect food web and human activities may exacerbate effects of climate change UVR and T have been increasing in the winter Aim Evaluate the effects of UVR and CO2 increase on winter phytoplankton assemblage in the Ria Formosa coastal lagoon (effects on growth, photosynthesis and community structure)
  • 6. Methods January 2012, typical winter conditions (Tw = 13ºC) sampling at inner location (to avoid influence of adjacentcoastal waters) sub-superficial water samples collected into 4.5 L UVR-transparent LDPE cubitainers control UVR high CO2 UVR + high CO2 48-hour in situ incubation phytoplankton (community and specific)net growth rates (epifluorescence andinverted microscopy) phytoplankton production UV-absorbing film +CO2 (14C incorporation – PE curves)
  • 7. Results - Changes in phytoplankton community growth and structure 0.8  no significant changes on community Community net growth rate (d-1) 0.7 net growth rates (based on chlorophyll 0.6 0.5 a concentration) in relation to the control 0.4 0.3 0.2 But… 0.1 0 control highCO2 UVR UVR highCO2 25 diatoms  significant changes on the relative abundance of phytoplankton groups Abundance (x105cells L-1) cryptophytes 20 cyanobacteria 15 changes in community structure 10 5 Dominance of nano-cryptophytes and 0 solitary centric diatoms (Thalassiosira) initial control highCO2 UVR UVR highCO2
  • 8. Results - Effects on specific phytoplankton groups  mortality under UVR exposure Cyanobacteria low levels of photoprotection due to their small size  mortality under high CO2 levels competition?  mortality under high CO2 and UVR CO2 did not counteract negative effects of UVR Cryptophytes  no effects of UVR and CO2 on growth rates Diatoms  diatoms (Thalassiosira) responded significantly to high CO2, UVR and UVR + CO2  diatoms are usually more resistant to UVR  enhancement of summer Pseudo-nitzschia blooms?
  • 9. Results - Effects on phytoplankton production diatoms clearly benefited from increased CO2 and UVR exposure increased protection provided by silicon frustules effective xantophyll cycle detrimental effect on grazers – grazing pressure - net growth no significant differences in P-E curves and photosynthetic characteristics underhigh CO2 and UVR exposure
  • 10. Conclusions – Effects of UVR and CO2 increase on phytoplankton changes in phytoplankton community structure cyanobacteria mortality no significant effects on cryptophytes higher net growth rates of diatoms no significant changes in production damaging effect on grazers rather than stimulatory effect on diatoms?Future prospects effects of CO2 and UVR on phytoplankton mortality (dilution experiments) effects of CO2 and UVR on nutrient enrichment and uptake (nutrient additionexperiments) combined effects of CO2, UVR and temperature increase on phytoplanktondynamics
  • 11. Thank You for Your Attention!AcknowledgementsFCT project Phytoria – Environmental regulation of phytoplankton in the Ria Formosacoastal lagoon (PTDC/MAR/114380/2009)Postdoctoral fellowship awarded to RBD (SFRH/BPD/68688/2010)