Seasonal changes of the microplankton community along a tropical estuary

Abstract

Microplankton organisms are an important link in the transfer of matter and energy between the benthic-pelagic microbial food web and higher trophic levels in estuaries. Although tropical estuaries are among the most productive aquatic systems globally, information on the spatial and seasonal dynamics of microplankton in such systems is scarce. In order to identify which variables control microplankton abundance and community structure a number of environmental variables were measured along the tropical Gulf of Nicoya (Costa Rica) during the rainy and dry seasons (2011)(2012). The Tempisque River was a major source of nutrients and turbidity and thus imposing a clear gradient along the estuary. Chlorophyll a (chl a) concentration was highest in the middle of the estuary (2.7-20 mg m -3 ), where turbidity decreased. The microplankton comprised mainly diatoms (88%) and dinoflagellates (8%).Multivariate analysis revealed five different microplankton assemblages associated with a seasonal and riverine-marine gradient, and supporting an ecotone model at the estuary head that shifts to an ecocline model for the rest of the estuary. Our results suggest that primary producers in the estuary were mainly limited by light rather than nutrients.

Size fractionated phytoplankton biomass and net metabolism along a tropical estuarine gradient

“…The flow of the Tempisque River affects phytoplankton abundance, community structure, and primary production in the inner basin of the Gulf of Nicoya due to its effects on water column stability, nutrient concentration, and light availability. Fresh water flow changes seasonally and controls the stability of the water column (Voorhis et al 1983;Seguro et al 2015). During the dry season, tidal and residual currents mix the water column between Sta.…”

Spatial and seasonal variation of microphytoplankton community and the correlation with environmental parameters in a hypereutrophic tropical estuary - Maranhão - Brazil

“…Based on that, the nitrogen was shown to be a limiting factor for the diatoms blooms and the phosphorus was a limiting factor for the proliferation of green algae and euglenoids. According to SIN et al (2015) and SEGURO et al (2015) it is common the nitrogen being the main limiting factor for marine phytoplankton and the phosphorus for continental phytoplankton. According to RODRIGUES and CUTRIM (2010), phosphorus is usually the main nutrient for microphytoplankton in the estuaries of Maranhão, suggesting that this community is physiologically well adapted to the conditions of nutrients mixing.…”

“…Regarding the microphytoplankton composition, diatoms were the most representative group, followed by dinoflagellates (SEGURO et al, 2015), which are transported by tidal currents, and are more frequent in the dry season (PAIVA et al, 2006). The dominance of diatoms is common in estuarine systems due to their euryhaline nature (SENA et al, 2015) and it is correlated directly with the silicate content, since the major source of silica is from the continent and the diatoms frustules have silica in their composition.…”

“…Thus, the phytoplankton acts as an outstanding environmental indicator (GUENTHER et al, 2015), once it is the transfer link and energy in estuarine trophodynamics. The phytoplankton community is capable of changing its composition and structure in response to different modifications of the environmental conditions caused by humans (REYNOLDS, 2006;GREGO et al, 2009;SEGURO et al, 2015).…”

Spring net community production and its coupling with the CO<sub>2</sub> dynamics in the surface water of the northern Gulf of Mexico

“…However, this assumption can be invalid in the dynamic coastal environments. Recent studies have shown that entrainment and upwelling processes (mixing with O 2depleted subsurface water) can lead to significant underestimation in NCP MLD using the O 2 /Ar method, especially in coastal upwelling zones (Castro-Morales et al, 2013;Nicholson et al, 2012;Shadwick et al, 2015;Teeter et al, 2018). As most regions in our study were characterized by the persistent surface stratification (Figs.…”