Viability of pico- and nanophytoplankton in the Baltic Sea during spring

Abstract

Phytoplankton cell death is an important process in marine food webs, but the viability of natural phytoplankton communities remains unexplored in many ecosystems. In this study, we measured the viability of natural pico-and nanophytoplankton communities in the central and southern parts of the Baltic Sea (55°21 0 N, 17°06 0 E-60°18 0 N, 19°14 0 E) during spring (4th-15th April 2016) to assess differences among phytoplankton groups and the potential relationship between cell death and temperature, and inorganic nutrient availability. Cell viability was determined by SYTOX Green cell staining and flow cytometry at a total of 27 stations representing differing hydrographic regimes. Three general groups of phytoplankton (picocyanobacteria, picoeukaryotes, and nanophytoplankton) were identified by cytometry using pigment fluorescence and light scatter characteristics. The picocyanobacteria and picoeukaryotes had significantly higher cell viability than the nanophytoplankton population at all depths throughout the study area. Viability correlated positively with the photosynthetic efficiency (F v /F m , maximum quantum yield of photosystem II) as measured on the total phytoplankton community. However, an anticipated correlation with dissolved organic carbon was not observed. We found that the abiotic factors suggested to affect phytoplankton viability in other marine ecosystems were not as important in the Baltic Sea, and other biotic processes, e.g. processes related to species succession could have a more pronounced role.

Temperature-related timing of the spring bloom and match between phytoplankton and zooplankton

“…Parasitism on phytoplankton has not been investigated in this area, but Elovaara et al (2020) observed that living cells accounted for ca 20-100% of the total phytoplankton community throughout the year, with higher proportion of living cells in spring (65%) than in summer (48%). These findings are comparable to observations during spring in the open Baltic Proper (Vanharanta et al 2020).…”

Seasonal variation in estuarine phytoplankton viability and its relationship with carbon dynamics in the Baltic Sea

“…Viability in our study varied between 18 and 97% and is therefore comparable to other studies. Viability of nano-and picophytoplankton was also studied on the open Baltic Proper by Vanharanta et al (2020) who reported viabilities ranging between 60 and 90% with surface water mean of 85%. We can therefore conclude that dying cells comprise an important proportion of the phytoplankton community in the Baltic Sea as in other systems.…”

“…Studies in the past two decades have highlighted the prevalence of high proportions of damaged or dead cells within phytoplankton communities in different aquatic ecosystems (Veldhuis et al, 2001;Hayakawa et al, 2008;Rychtecký et al, 2014;Kozik et al, 2019;Vanharanta et al, 2020). Non-viable cells have been detected by membrane probes which identify cells with compromised membrane integrity, and which are therefore considered to be dead (Veldhuis et al, 2001;Agustí & Sánchez, 2002;Kroemer et al, 2009) although defining the actual point of no-return for microbial death is difficult (Davey, 2011).…”

Seasonal and Spatial Changes of Primary Production in the Baltic Sea (Europe) Based on in situ Measurements in the Period of 1993–2018

“…The use of filters with smaller pores (cellulose acetate filter with a pore size 0.45 µm) in our measurements makes it possible to take into account smaller phytoplankton fractions (Nielsen and Bresta, 1984), which can significantly increase the value of determined PP. The study of plankton diversity in the Baltic waters reveal that pico-and nanoplankton can dominate from 5 to even 98% of the total phytoplankton biomass and those algae taxa have higher specific photosynthesis and growth rates than the larger cells (Wasmund and Uhlig, 2003;Jakubowska and Szeląg-Wasielewska, 2015;Hu et al, 2016;Vanharanda et al, 2020). Biomass of picocyanobacteria like Synechococcus spp.…”