Temporal and spatial variability of phytoplankton photosynthetic characteristics in a southern European estuary (Douro, Portugal)

Planktonic primary production in the western Dutch Wadden Sea

“…Visual inspection of the curves did not reveal any abnormalities. Rates higher than the theoretical maxima have been reported in other studies as well and were in those cases related to low chlorophyll-a concentrations due to the dominance of small, but very productive cells (Lohrenz et al 1994, Azevedo et al 2010. Low chlorophyll-a concentrations could also be the result of mistakes during filtration or incomplete extraction of pigments.…”

Seasonal and Spatial Variability of Phytoplankton Primary Production in a Shallow Temperate Coastal Lagoon (Ria Formosa, Portugal)

“…The maximal biomass-specific production rate (P B max ) and photosynthetic efficiency (α) were strongly correlated with each other, which is not expected, as α is related to the concentration of photosynthetically active pigments [48] and P B max is related to electron transport capacities [49]. However, many studies have observed linear relationships between the two parameters (e.g., [21,24,50]), attributed to a variety of physiological and ecological factors, and changes in phytoplankton composition [51]. The positive relationship between P B max and α indicates that phytoplankton with a lower photosynthetic efficiency tends to exhibit a lower maximum photosynthetic rate, which contradicts the typical photo-acclimation of phytoplankton, with lower photosynthetic efficiency but the higher maximum photosynthetic rate at surface waters, associated with higher light availability [52].…”

“…Despite no significant spatial variability or correlation with environmental variables, photosynthetic parameters varied seasonally, with significantly higher P B max and α observed during summer. Higher summer values for photosynthetic parameters are typically observed in coastal ecosystems, associated with higher water temperature and light availability [21] and favorable upwelling conditions [54]. In the Ria Formosa coastal lagoon, water temperature in the spring, summer, and autumn periods was significantly higher than in the winter, and upwelling events in the adjacent coastal area are a common occurrence throughout the late spring-early summer period [55].…”

“…In the Ria Formosa, phytoplankton growth is indeed limited by light at the deeper lagoon locations [28], particularly in the winter [27]. In other temperate coastal ecosystems, photosynthetic activity is also strongly correlated with light availability (e.g., [21]), particularly in turbid, nutrient-rich estuaries (e.g., [23,45]).…”

“…P-E curves are extremely helpful to understand the physiology and ecology of natural phytoplankton communities [16], and they have been the subject of many studies aiming to understand the environmental controls of primary production. The variability of photosynthetic parameters is usually related to variability in environmental drivers, such as water temperature [17], light intensity [18], and nutrients [19], as well as species composition [20] and endogenous circadian rhythms [21]. Therefore, variability in P-E curves is observed at different time scales, especially seasonally [22][23][24], due to the natural variability of light and temperature.…”