Spatio-temporal dynamics of phytoplankton community in a well-mixed temperate estuary (Sado Estuary, Portugal)

Abstract

Estuaries are highly productive ecosystems, which are strongly affected by several anthropogenic pressures. Phytoplankton is a key element for assessing the ecological quality status in these transitional waters. Moreover, understanding physico-chemical and biological drivers is crucial to disentangle their effect on the structure of phytoplankton community. The present work aims to study the effect of the main physico-chemical drivers on the phytoplankton community structure and dynamics in a temperate well-mixed estuary (Sado Estuary). Four sampling stations were analyzed monthly in three regions of the estuary, from 2018 to 2019. Surface water samples were collected to analyze the phytoplankton community and several concomitant physico-chemical parameters. Temperature, turbidity, salinity, and nutrients availability were the drivers that best explained the spatio-temporal patterns observed in the phytoplankton community. The upper estuary was characterized by higher phytoplankton cell abundances and biomass. Three phytoplankton groups stood out in the characterization of the estuarine assemblages: diatoms, cryptophytes, and dinoflagellates. Diatoms were the dominant group most of the year, being dominated by small cell species (single and chain-forming) upstream, and by larger chain-forming species downstream. Cryptophytes had a high contribution to the community in the inner regions of the estuary, while dinoflagellates contributed more for the community composition downstream, where high abundances of harmful algal species were sporadically found. Previous studies on the phytoplankton community dynamics in this estuary are limited to the 1990s. Thus, the present study provides insight into changes in the dominant phytoplankton groups of the Sado Estuary in the last 25 years, namely an increase in cryptophytes over diatoms in the inner estuarine regions, and an increase in dinoflagellates near the estuary mouth.

Daily Fluctuation of Planktons Abundance in Percut Sei Tuan Waters, Deli Serdang Regency, North Sumatera

“…Research conducted by Witariningsih, et al (2020), in the waters of the Lombok Strait also found the most species from the Bacillariophyceae class. This is also supported by Santos, et al (2022) which state that many types of phytoplankton found in the Estuary Area in Sado, Portugal come from the Bacillariophyceae class. The least phytoplankton found at the study site came from the Pyramimonadophyceae class (2%) with only 1 genus, namely Halosphaera and from the Dinophyceae class (2%) also only found 1 genus, namely Peridinium.…”

Teleconnection Between Coastal Phytoplankton Blooms Phenomenon in Western North Pacific and El Niño–Southern Oscillation by Time‐Frequency Analysis

“…Climate change affects the primary production, that is, phytoplankton, in the aquatic environment (Behrenfeld et al, 2006;Doney, 2006;Doney et al, 2012). It has been confirmed that the phytoplankton was climate-driven, either in basin scale or on a more small scale, like bays, estuaries (Santos et al, 2021(Santos et al, , 2022. Nevertheless, much less knowledge is known about the marine scale due to the complex influences, and lack of long-term observations.…”

“…Marine phytoplankton are naturally believed and already proven to be influenced by climate oscillations. For instance, although strong correlations between marine phytoplankton and modes of climate variability (i.e., North Atlantic Oscillation, El Ni ño-Southern Oscillation) were reported for several lakes in coastal areas, much less is known for large scales in the marine as a unit, comparing to small and medium scales (i.e., bays, estuaries) (Santos et al, 2021(Santos et al, , 2022. Furthermore, on large level, the ultimate drivers of climate oscillations on phytoplankton are not yet understood, and the consequences of the ecosystem remain uncertain (Menge et al, 2009).…”

Phytoplankton community response to a drought‐to‐wet climate transition in a subtropical estuary

“…Similarly, the low-inflow (average river inflow 1-60 m 3 s À1 ) Sado Estuary system in Portugal is also typically dominated by diatoms, although an increasing abundance of cryptophytes in the upper estuary was observed over the past 20 yr, potentially due to nutrient enrichment patterns (Santos et al 2022). Cryptophytes were the third most abundant taxa in the Mission-Aransas Estuary, and although no change was detected across the drought-to-wet transition, the relative abundance of cryptophytes was associated with high DIN and PO 4 3À concentrations (Fig.…”