Phytoplankton distribution and photosynthesis dynamics in the Chubut River estuary (Patagonia, Argentina) throughout tidal cycles

Abstract

The aim of this study was to determine the effects of the tidal dynamics and physical forcing on phytoplankton distribution and photosynthesis dynamics in the Chubut River estuary, Argentina. Physical, chemical, and biological variables measured at the surface and at the bottom of the water column (variable between 0.5-m and 6-m depth) were made every 30-45 d during tidal cycles (13 h of duration) from June 2007 to November 2008 (11 tidal cycles). There was a remarkable consistency among different tidal cycles throughout the year, with strong stratification during the flood and almost complete mixing during the period high tide-ebb-low tide. Strong stratification during the flood resulted in significant inhibition of photosynthesis of mostly nanoplankton cells at the surface, while microplankton sank out of this upper layer and, thus, were less inhibited. Mixing conditions during the ebb, together with relatively high concentration of dissolved organic matter and particulate material, resulted in partial protection for phytoplankton against solar radiation stress and, therefore, relatively high maximum electron transport rate values were determined under this condition. However, the lowest photoinhibition and higher maximum rate of production (P max ) values occurred at depth during stratified conditions, probably due to relatively low solar radiation in this condition. Tidal dynamics together with physical forcing are key factors that condition the distribution, dynamics, and photoinhibition of phytoplankton in the Chubut River estuary.

Increase in Rubisco activity and gene expression due to elevated temperature partially counteracts ultraviolet radiation–induced photoinhibition in the marine diatom Thalassiosira weissflogii

“…In the case of midlatitudes, as characterized our study site, phytoplankton experience great changes throughout the year, not only in terms of temperature and the depth of the upper mixed layer but also in terms of solar radiation impinging the sea surface (Villafañ e et al 2004). The lowest temperature used in our experiments (20uC) is close to the mean summer seawater surface value of 18uC along the Patagonian coast and is within the observed range of temperatures during summer (Villafañ e et al 2004;Helbling et al 2010). However, we imposed an increase of 5uC over the in situ value, as was predicted for the year 2100 (Houghton et al 2001).…”

Impact of Increased Nutrients and Lowered pH on Photosynthesis and Growth of Three Marine Phytoplankton Communities From the Coastal South West Atlantic (Patagonia, Argentina)

“…Only a few studies have focused on the effects of global change variables in this site; namely, one investigated the impact of solar ultraviolet radiation (UVR) on photosynthesis, and another the interactive effects of UVR and nutrients on phytoplankton growth and species composition (Villafañe et al, 2004;Marcoval et al, 2008). The PU site is under the influence of riverine waters that carry a heavy load of anthropogenic nutrients (Helbling et al, 2010;Bermejo et al, 2018), which also results in high Chl a concentration at the plume of the river (Figure 1B). Several global change studies have been done on phytoplankton communities from this site, with variables such as lowered pH, nutrients, temperature, input of terrigenous materials and mixing (Helbling et al, 2015b;Bermejo et al, 2018;Villafañe et al, 2018;Bermejo et al, 2020).…”

Global change effects on biogeochemical processes of Argentinian estuaries: An overview of vulnerabilities and ecohydrological adaptive outlooks

“…1H) is a coastal mesotidal-plain polluted by nutrient inputs from the use of fertilizers and the discharge of effluents Helbling et al, 2010), hydrocarbons from portuary activities (Commendatore and Esteves, 2004), and metals (Gil et al, 1999). The estuaries of the river Deseado, Santa Cruz, and Gallegos ( Fig.…”