Unusual behaviour of phototrophic picoplankton in turbid waters

Abstract

Autotrophic picoplankton (APP) abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4–2250 mg l-1) and phytoplankton biomass (chlorophyll a: 1–460 μg l-1) range, as well as APP abundance (0 and 100 million cells ml-1) and contribution (0–100%) to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity), above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass) is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity.

Environmental constraint of intraguild predation: Inorganic turbidity modulates omnivory in fairy shrimps

“…The systems are naturally hypertrophic with total phosphorus concentrations (TP) ranging between 67 and 58,772 μg/L (measured between 2009 and 2010; Boros et al, 2013). Picosized unicellular algae are the dominant group of phytoplankton in these systems (Somogyi et al, , 2017. For this reason, soda pans and sodic meadows are important resting sites for numerous waterbirds during their seasonal migration on the north-south route in the Western Palaearctic (Boros et al, 2013;Horváth, Vad, Vörös, et al, 2013b).…”

“…The algal and zooplankton density generally increases with TSS in the pans, reaching extremely high abundances . Picosized unicellular algae are the dominant group of phytoplankton in these systems (Somogyi et al, , 2017. The dominant species of zooplankton are the calanoid copepod Arctodiaptomus spinosus and the cladoceran Moina brachiata, especially in turbid and saline pans .…”

Dual bloom of green algae and purple bacteria in an extremely shallow soda pan

“…According to our current knowledge, within Europe, soda lakes could be found exclusively in the Carpathian Basin; their size ranges from small wetlands of few m 2 to few hundred ha (Boros et al 2014 , 2017 ). Most of them are intermittent aquatic systems and have low water transparency (Boros et al 2017 ; Somogyi et al 2017 ). Two main types of these shallow lakes (which are usually referred as pans) could be distinguished, the ‘turbid type’ (high amount of suspended solids and usually high concentration of humic substances) and the ‘colored type’ (relatively low amount of suspended solids and very high concentration of humic substances) (Boros et al 2017 ).…”

“…The key primary producers in soda lakes of the Carpathian Basin are cyanobacteria, eukaryotic green algae and euglenophytes (Vörös et al 2008 ; Somogyi et al 2017 ). Phytobenthos is considered to be negligible due to the strong underwater light limitation (Boros et al 2013 ), while phytoplankton (especially in the turbid-type waters) is usually dominated by pico-sized (< 3 μm) species (Vörös et al 2008 ; Felföldi et al 2009 ; Somogyi et al 2009 , 2017 ) and has characteristic seasonal changes.…”

“…The key primary producers in soda lakes of the Carpathian Basin are cyanobacteria, eukaryotic green algae and euglenophytes (Vörös et al 2008 ; Somogyi et al 2017 ). Phytobenthos is considered to be negligible due to the strong underwater light limitation (Boros et al 2013 ), while phytoplankton (especially in the turbid-type waters) is usually dominated by pico-sized (< 3 μm) species (Vörös et al 2008 ; Felföldi et al 2009 ; Somogyi et al 2009 , 2017 ) and has characteristic seasonal changes. Below 15 °C, picoeukaryotes (mainly Chloroparva and Choricystis ) dominate, while above this temperature picocyanobacteria (mostly Synechococcus/Cyanobium ) occur (Vörös et al 2008 ; Felföldi et al 2009 , 2011 ; Somogyi et al 2009 , 2011 , 2016 ).…”