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Absolute cell count change after 10 days cultivation from initial values of (A) Actinocyclus octonarius (initially approximately 40 cells per ml) and (B) Nitzschia dubiiformis (initially approximately 1400–4000 cells per ml) at 20°C under different light [light (16:8 h light dark cycle) and dark] and medium conditions. Data represent mean values ± SD (n = 3). Different lowercase letters indicate significantly different means (p < 0.05; one-way ANOVA with post hoc Tukey’s test).
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Eight benthic diatom taxa (Actinocyclus octonarius, Melosira moniliformis, Halamphora sp. 1, Halamphora sp. 2, Navicula perminuta, Navicula phyllepta, Nitzschia dubiiformis, Nitzschia pusilla) were isolated from sediments sampled in the southern coastal brackish Baltic Sea and established as unialgal cultures. The coastal shallow water sampling are...
Citations
... This is under the assumption that the respiration rates remained constant, but light respiration rates can be higher than during the night (Fenchel & Glud, 2000). No notable increase of oxygen production in the MHW chambers compared with Control agrees well with the general concept that heterotrophic processes increase more strongly with rising temperatures compared with autotrophic processes (Alsterberg et al., 2012;Hancke & Glud, 2004;Prelle et al., 2019;Trnovsky et al., 2016;Yvon-Durocher et al., 2010). ...
The magnitude and frequency of marine heatwaves are increasing and predicted to intensify, but our ability to understand the real‐world effects on vital benthic ecosystems is lagging behind. Prior insights into the impacts of marine heatwaves are often derived from observational or laboratory studies. Observational studies may not fully disentangle the complexities of potential compound events and typically focus on severe, often lethal marine heatwaves. Laboratory studies, on the contrary, while valuable for understanding specific mechanisms, often use artificial setups and can introduce unnatural disturbances that do not reflect real‐world scenarios.
To investigate sublethal temperature effects of marine heatwaves in a natural benthic habitat, we developed a novel approach for inducing elevated water temperatures in situ over several days. The system utilizes domestic underfloor heating technology combined with custom‐made benthic chambers.
We placed 10 chambers for 15 days in a bare‐sediment habitat at 2.5 m depth and heated five chambers to 5°C above ambient water temperatures in summer for 6 days, followed by a period of 7 days at ambient temperatures. Incubations during day and night were performed during the experiment to assess changes in ecosystem functioning (solute fluxes) and sediment cores were collected at the end of the experiment to assess the effects of a realistic marine heatwave on benthic community structure.
The results indicate that while the benthic community structure remained similar between the treatments, except for a size shift of Marenzelleria spp. towards smaller individuals in the heated treatment, elevated temperatures caused a significant increase in community respiration and amplified the magnitude of either efflux or influx of nutrients (NH4⁺‐N, PO4³⁻‐P and Si).
Primary production during daytime incubations remained mostly unaffected by the heatwave treatment, contributing to the concept of heterotrophy being more influenced by increased temperatures than autotrophy.
This study confirms the suitability of the novel system for examining the impact of temperature on benthic habitats in situ and demonstrates its potential for the investigation of complex habitats and communities, which are essential for our understanding of the ecosystem‐level effects of climate change.
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... PI curves of the three Streptofilum strains (four replicates per strain) were measured according to the protocol published earlier (Prelle et al. 2019). Briefly, ~3 mL of thin log phase algal suspension of each strain and 2 mM final concentrationof NaHCO 3 were added to four airtight water-tempered (20°C) oxygen electrode chambers (DW1, Hansatech Instruments, King's Lynn, UK). ...
Streptofilum capillatum was recently described and immediately caught scientific attention, because it forms a phylogenetically deep branch in the streptophytes and is characterised by a unique cell coverage composed of piliform scales. Its phylogenetic position and taxonomic rank are still controversial discussed. In the present study, we isolated further strains of Streptofilum from biocrusts in sand dunes and Arctic tundra soil. Molecular and morphological characterisation including transmission electron microscopy confirmed that both new strains belong to Streptofilum . The Arctic strain is described as a new species, Streptofilum arcticum sp. nov., based on molecular differences, a specific sarcinoid morphology and unique ultrastructure with massive cell coverage composed of pili‐shaped scales. A comprehensive characterisation of the ecophysiological traits of both new Streptofilum isolates and the original one revealed a broad temperature tolerance, a rapid recovery of photosynthetic performance after desiccation, an efficient photosynthesis at low light and a tolerance to high‐light conditions. In addition, Streptofilum could cope with UV irradiation, but only S. capillatum grew under UV exposure. All Streptofilum strains are well‐adapted to water‐deprived terrestrial habitats such as biocrusts. From this study it can be concluded that already early‐branching streptophytes were able to tolerate terrestrial conditions.
... Again, from stock cultures, inoculum cultures were set up during their exponential growth by adding 2 ml in 40 ml f/2 medium with silicate in autoclaved Baltic Sea water. To measure the photosynthetic activity of the cultures, a so-called "Photosynthetic Irradiance Box" (PI-Box) was used, following a widely applied methodology [42,43] and mimicking natural conditions. Under a light gradient from 0 (dark) to 1446 ± 83 μmol photons m −2 s −1 , the oxygen production was measured using an optode as a sensor, with 4-8 technical replicates per culture. ...
Dormancy is a wide-spread key life history trait observed across the tree of life. Many plankton species form dormant cells stages that accumulate in aquatic sediments and under anoxic conditions, form chronological records of past species and population dynamics under changing environmental conditions. Here we report on the germination of a microscopic alga, the abundant marine diatom Skeletonema marinoi that had remained dormant for up to 6871 ± 140 years in anoxic sediments of the Baltic Sea and resumed growth when exposed to oxygen and light. Resurrected diatom strains, representing cohorts from 6 different time points of the past 6871 ± 140 years, are genetically differentiated and fundamental physiological functions such as growth and photosynthesis had remained stable through time, despite distinct environmental dynamics. Showing that resurrection and full functional recovery, in comparison to 3 ± 2 years of dormancy, is possible after millennial resting, we emphasize the relevance of dormancy and living sediment archives. For the future, sediment archives, together with the resurrection approach would offer a powerful tool to trace adaptive traits over millennia under distinct climatic conditions and elucidate the underlying mechanisms.
... Despite this potential bias, we consider that diatoms are the dominant group in sequences from sediment samples of New Caledonia. Within the microphytobenthos, this group could be the major source of oxygen production in such dynamic shallow coastal areas (Karsten et al. 2021;Prelle et al. 2019). In various marine ecosystems, the growth of photosynthetic organisms is often limited by the availability of certain metals, such as iron (Hutchins and Bruland 1998) or manganese (Browning et al. 2021), or nutrients like nitrogen (Moore et al. 2013). ...
Estuaries are a key component of the land‐sea continuum, and their microbial diversity depends on the connection with terrestrial ecosystems. This work aimed to demonstrate that the terrestrial matter carried by rivers influences the structuration of microeukaryote communities of superficial (0–3 cm) sediments collected at the interface between the land and marine coastal areas. To demonstrate this hypothesis, we have chosen the main island of New Caledonia as a study site, a French overseas territory located in the South West Pacific. Using amplicon sequencing of the 18S‐V4 rDNA extracted from sediments, we analyzed microeukaryote community composition in relation to numerous environmental parameters. Samples were collected in five bays influenced by riverine inputs and corresponding to distinct geological features of the watersheds, as revealed by high variations in metal concentrations released from specific minerals in the sediment. Particularly, the influence of ultramafic soils was highlighted by higher nickel concentration (correlated to Co, Cr, Mn, and Fe). Diatoms were the dominant taxonomic group, especially the classes of Bacillariophyceae and Mediophyceae. Then Apicomplexa, Ciliophora, Dinoflagellata, and Cercozoa followed. The metallic composition of the sediment explained 18.46% of the community spatial variability. The selection of ASVs based on their contribution to beta diversity and their correlation with metallic concentrations enabled us to identify spatial patterns. This information could lead to identifying microeukaryote bioindicators of terrestrial influences, particularly of ultramafic origin. We hypothesized that the association between microeukaryotes and metallic compositions is linked to selection processes, given the resistance of some microeukaryotes to some high metallic concentrations. In vitro experiments are needed to confirm this hypothesis. Our results emphasized the role of terrestrial inputs in shaping estuarine diversity and the need to consider the entire land–sea continuum for studying these ecosystems.
... Photosynthetic oxygen release rates of recent and subrecent N. spumigena strains were measured under increasing photon f lux densities (PFD) to investigate the light requirements of the resurrected strains at a fixed temperature of 20 • C. Therefore, eleven light levels were adjusted using neutral gray filter foils, which ranged from 0 to 1490 μmol photons m −2 s −1 (0, 4, 11, 27, 35, 89, 135, 336, 584, 886, 1490). The exact PFD was controlled inside each cuvette using a micro-sphere light meter (LI-250, LI-COR, Lincoln, United States) following Prelle [33]. ...
Cyanobacterial blooms in the Baltic Sea proliferated in recent decades due to rising sea surface temperatures, resulting in significant ecological impacts. To elucidate their current success, we examined ecophysiological, biochemical, and morphological traits of recent and ~33-year-old strains of Nodularia spumigena using a resurrection approach. The ability of many cyanobacteria to form dormant stages that can persist in anoxic sediments for decades provides a unique opportunity to study adaptive traits to past environmental conditions. A short sediment core from the Eastern Gotland Basin was processed to isolate strains of N. spumigena buried in 1987 ± 2 and 2020 ± 0.5 Common Era. Sequencing was used for species identification, followed by characterization of cell morphometry, carbon, nitrogen, and chlorophyll a content. Photosynthetic performance was evaluated by using pulse-amplitude modulated fluorimetry and oxygen optodes to assess light and temperature requirements. Our results revealed trait changes in N. spumigena over the past 3 decades: Temperature optimum for photosynthesis shifted from 15.3–21.1°C, which is consistent with the past and present local SST. Recent strains exhibited increased carbon, nitrogen, and chlorophyll a content despite decreased cell volume. The demonstrated adaptability of N. spumigena to increasing temperature suggests that this species will thrive in a warmer climate in the future. These insights will aid modeling efforts aimed at understanding and managing consequences of future cyanobacterial blooms in the Baltic Sea ecosystem.
... The dominant species are: Actinocyclus kuetzingii, Actinocyclus octonarius, Amphora coffeaeformis, Cyclotella striata, Paralia sulcata, Planothidium delicatulum, Pleurosigma angulatum, Surirella armoricana, Thalassionema nitzschioides, Thalassiosira leptopus, and Tryblioptychus cocconeisformis (Fig. S1). Among them, Planothidium delicatulum and Aulacoseira granulata are freshwater diatoms (Hartley et al., 1996;Hustedt, 1985); Actinocyclus octonarius, Cyclotella striata, S. armoricana, and Paralia sulcata are commonly found in brackish water in estuarine areas (Jiang et al., 2004;Prelle et al., 2019;Ran and Jiang, 2005). Some marine diatom species, such as Thalassionema nitzschioides, exhibit strong tolerance to SST and SSS (Jousé et al., 1971). ...
Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions, research on diatom transfer functions and database establishment remains incomplete. This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea, together with environmental variables. Principal component analysis of the environmental variables showed that sea surface salinity (SSS) and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area, whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution. Based on the modern diatom species-environmental variable database, we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area. The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatom-based SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area. Three low SSS events in AD 2019, 2013, and 1999, together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes, corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County. Thus, a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.
... Different results were found in the study of diatom isolates, as their photosynthesis reached saturation levels between approximately 30-150 μmol/m 2 /s. Nevertheless, the examined strains displayed a significant degree of photo-physiological adaptability, and there was no evidence of light inhibition (Woelfel et al., 2014;Prelle et al., 2019;Prelle and Karsten, 2022). This adaptability could prove advantageous for them in shallow coastal areas, where they frequently experience substantial fluctuations in incident radiation owing to the tidal rhythm. ...
... Temperatures in the chambers were maintained at 5°C using a refrigerated circulator pump system. More details for this experimental setup can be found elsewhere (Prelle et al., 2019). After O 2 measurements, algae were transferred onto Whatman GF/6 glass fiber filters, chlorophyll a was extracted with 96% EtOH (v/v) and quantified spectrophotometrically (Helcom, 2019). ...
Antarctic algae are exposed to prolonged periods of extreme darkness due to polar night, and coverage by ice and snow can extend such dark conditions to up to 10 months. A major group of microalgae in benthic habitats of Antarctica are diatoms, which are key primary producers in these regions. However, the effects of extremely prolonged dark exposure on their photosynthesis, cellular ultrastructure, and cell integrity remain unknown. Here we show that five strains of Antarctic benthic diatoms exhibit an active photosynthetic apparatus despite 10 months of dark-exposure. This was shown by a steady effective quantum yield of photosystem II (Y[II]) upon light exposure for up to 2.5 months, suggesting that Antarctic diatoms do not rely on metabolically inactive resting cells to survive prolonged darkness. While limnic strains performed better than their marine counterparts, Y(II) recovery to values commonly observed in diatoms occurred after 4-5 months of light exposure in all strains, suggesting long recovering times. Dark exposure for 10 months dramatically reduced the chloroplast ultrastructure, thylakoid stacking, and led to a higher proportion of cells with compromised membranes than in light-adapted cells. However, photosynthetic oxygen production was readily measurable after darkness and strong photoinhibition only occurred at high light levels (>800 µmol photons m⁻² s⁻¹). Our data suggest that Antarctic benthic diatoms are well adapted to long dark periods. However, prolonged darkness for several months followed by only few months of light and another dark period may prevent them to regain their full photosynthetic potential due to long recovery times, which might compromise long-term population survival.
... Thus, the history of where they live can be detected. Many species have high sensitivity to environmental changes and can respond quickly to them (Prelle et al. 2019). The genera from Bacillariophyceae are cosmopolitan, have high reproductive capacity, and can survive in extreme conditions (Padisak and Naselli-Flores 2021). ...
Tambaru R, Burhanuddin AI, Haris A, Amran MA, Massinai A, Muhiddin AH, Yaqin K, Firman, Yuliana. 2024. Diversity and abundance of phytoplankton in Bone Bay, South Sulawesi, Indonesia and its relationship with environmental variables. Biodiversitas 25: 624-631. Ecological studies of phytoplankton have been widely conducted in various bays around the world. However, such research is still limited in Bone Bay, South Sulawesi, Indonesia. Therefore, this study aimed to investigate the diversity and abundance of phytoplankton in Bone Bay and the relationships with environmental factors. Data collection was conducted in the dry season (May to June 2023) at four stations, namely Bajoe Harbor (PB), Cappa Ujung (CU), Libureng (LB), and Tongke-Tongke (TT). At each station, seawater samples were collected and environmental variables were measured including temperature, salinity, pH, currents, and nutrients (i.e. Nitrate, Nitrite, Ammonium, Orthophosphate, and Silicate). In general, the environmental variables in the studied area were within the range of optimal condition for phytoplankton to grow and develop. There were three classes of phytoplankton recorded, namely Bacillariophyceae, Cyanophyceae, and Dinophyceae, with a total of 31 genera were identified. Chaetoceros, Thallasionema, and Rhizosolenia were the dominant genera. The average abundance of phytoplankton was significantly different among stations with the highest was found in CU and PB compared to that in LB and TT (p-value <0.01). PCA analysis showed that phytoplankton abundance was related to high orthophosphate concentrations, silicate, and turbidity at the PB and CU stations, while the opposite condition occured at the LB and TT stations. Based on the diversity and abundance of phytoplankton, Bone Bay, South Sulawesi is now still in good condition, yet monitoring studies are recommended to see the changes in the future.
... Photosynthesis-irradiance (PI)-curves of the five diatom strains (four replicates per strain) were measured according to Prelle et al. (2019). Briefly, 3.1 mL of thin log phase algal suspension of each strain and 31 μL sodium bicarbonate (NaHCO 3 , 2 mM final concentration) were added to four airtight water-tempered (20°C) oxygen electrode chambers (DW1, Hansatech Instruments, King's Lynn, United Kingdom). ...
Terrestrial diatoms are widespread in a large variety of habitats and are regularly recorded in biocrusts. Although diatoms have long been known to live in terrestrial habitats, only a few studies have focused on their diversity of ecophysiology. Here we present a study on the ecophysiological performance of five terrestrial diatom cultures from biocrusts, which were collected in sand dunes of the German coast of the Baltic Sea. The sampling sites were selected along a gradient of human impacts on the dunes. The richness of diatom species, roughly estimated from permanent slides, was around 30 species per sampling site. The species abundance was calculated in the same way revealing a high proportion of broken diatom frustules. All diatom cultures established in the laboratory showed no photoinhibition and high oxygen production along a light gradient. The desiccation tolerance differed among the strains, with high recovery observed for Hantzschia abundans and Achnanthes coarctata and low to no recovery for Pinnularia borealis and Pinnularia intermedia. The maximum growth rate for most strains was between 25 and 30°C. These temperatures can be easily reached in their natural environments. Nevertheless, during short-term exposure to elevated temperatures, oxygen production was recorded up to 35°C. Interestingly, two of five diatom cultures (Hantzschia abundans and Pinnularia borealis) produced mycosporine-like amino acids. These UV-protective substances are known from marine diatoms but not previously reported in terrestrial diatoms.
