Photosynthetic, Respirational, and Growth Responses of Six Benthic Diatoms from the Antarctic Peninsula as Functions of Salinity and Temperature Variations

Abstract

Temperature and salinity are some of the most influential abiotic parameters shaping biota in aquatic ecosystems. In recent decades, climate change has had a crucial impact on both factors—especially around the Antarctic Peninsula—with increasing air and water temperature leading to glacial melting and the accompanying freshwater increase in coastal areas. Antarctic soft and hard bottoms are typically inhabited by microphytobenthic communities, which are often dominated by benthic diatoms. Their physiology and primary production are assumed to be negatively affected by increased temperatures and lower salinity. In this study, six representative benthic diatom strains were isolated from different aquatic habitats at King George Island, Antarctic Peninsula, and comprehensively identified based on molecular markers and morphological traits. Photosynthesis, respiration, and growth response patterns were investigated as functions of varying light availability, temperature, and salinity. Photosynthesis–irradiance curve measurements pointed to low light requirements, as light-saturated photosynthesis was reached at <70 µmol photons m−2 s−1. The marine isolates exhibited the highest effective quantum yield between 25 and 45 SA (absolute salinity), but also tolerance to lower and higher salinities at 1 SA and 55 SA, respectively, and in a few cases even <100 SA. In contrast, the limnic isolates showed the highest effective quantum yield at salinities ranging from 1 SA to 20 SA. Almost all isolates exhibited high effective quantum yields between 1.5 °C and 25 °C, pointing to a broad temperature tolerance, which was supported by measurements of the short-term temperature-dependent photosynthesis. All studied Antarctic benthic diatoms showed activity patterns over a broader environmental range than they usually experience in situ. Therefore, it is likely that their high ecophysiological plasticity represents an important trait to cope with climate change in the Antarctic Peninsula.

Lipid degradation and photosynthetic traits after prolonged darkness in four Antarctic benthic diatoms, including the newly described species Planothidium wetzelii sp. nov.

“…All measured P–I curves exhibited a typical shape without photoinhibition, as already reported for some of the species in detail in Prelle et al ( 2022 ). The key parameters NPP max and respiration were selected for all species before and after dark incubation ( Table 2 ), and species-specific responses could be outlined.…”

“…D300_015 was only identified at the genus level as Planothidium sp. in Prelle et al ( 2022 ). Morphological and molecular investigations showed that strain D300_025 is the same species.…”

“…This taxon was first published by Witkowski et al ( 2010 ) from the Kerguelen Islands coastal area, Southern Ocean, and more recently also reported from Livingston Island, north of the Antarctic Peninsula (Zidarova et al, 2022 ). LM and SEM pictures of this strain can be found in Prelle et al ( 2022 ).…”

Molecular phylogenetics coupled with morphological analyses of Arctic and Antarctic strains place Chamaepinnularia (Bacillariophyta) within the Sellaphoraceae

“…Our sample location at 15 m water depth from a sediment biofilm in a marine environment is quite different from the type locality. Prelle et al (2022) verified a broad salinity tolerance for this species, supporting its presence and adaptation to different habitats. Growth of this species in culture was proven at 0-65 S A (absolute salinity) and a photosynthetic potential up to 100 S A .…”

The interacting effect of prolonged darkness and temperature on photophysiological characteristics of three Antarctic phytoplankton species

“…Algal respiration rates in darkness are known to vary by two orders of magnitude (Geider & Osborne, 1989). A study of six Antarctic benthic diatoms showed 5‐fold variability in respiration rates between species as well as temperature dependence of respiration rates (Prelle et al, 2022). Therefore, differences in respiration rates and the capacity to store energy reserves may to a large extent explain how long species can maintain photosynthetic fitness in darkness.…”