Environmental drivers of the spatio-temporal variations of chlorophyll-a within the coastal polynya in the Ross Sea

Ultraviolet and photosynthetically active radiation can both induce photoprotective capacity allowing barley to overcome high radiation stress

Steinhoff F.S., Wiencke C., Wuttke S. and Bischof K. 2011. Effects of water temperatures, UV radiation and low vs high PAR on phlorotannin content and germination in zoospores of Saccorhiza dermatodea (Tilopteridales, Phaeophyceae). Phycologia 50: 256–263. DOI: 10.2216/09-107.1Global climate change will have multiple effects on our environment and might especially change marine coastal ecosystems and their communities due to rising water temperatures and changing light regimes in the water column. Due to the key role of zoospores in the life-history cycle of kelps, we investigated how zoospores of the shallow water species Saccorhiza dermatodea (B. de la Pylaie) J.E. Areschoug respond to interactive effects of changing water temperatures, low/high photosynthetically active radiation (PAR) and UV radiation (UVR). Zoospores were examined with respect to germination pattern (germination rates, light micrographs) and phlorotannin content (Folin–Ciocalteu method). In summer 2007, we exposed S. dermatodea zoospores, obtained from fertile thalli in Kongsfjorden (Svalbard, Norway), to low PAR laboratory [UV-B∶UV-A∶PAR (W m−2) 8∶114∶100; 2–17°C] and high PAR outdoor experimental conditions [UV-B∶UV-A∶PAR (W m−2) 0.1∶5∶100; 7°C] for 8 h. Under low PAR+UVR conditions and at 2–12°C, almost 98% of zoospores germinated in all light treatments. The germination rate was reduced under PAR+UV-A+UV-B only in the 17°C and 7°C outdoor treatment, to 21.4% and 9.6%, respectively. Light microscopic investigations showed differences in germling appearance, growth and pigmentation in the outdoor treatment and at 17°C low PAR conditions, compared with all other treatments, after an exposure time of 8 h. However, phlorotannin content within zoospores remained unaffected by changing UV and low/high PAR conditions. These results suggest that combined effects of present water temperatures, high PAR and UVR can exhibit similar effects on germination as the combined effects of unnatural high temperatures (17°C), low PAR and UVR. With respect to global climate change, the ecological implications of the present study illustrate that zoospores of S. dermatodea are able to survive enhanced water temperatures up to 12°C. Moreover, high PAR in combination with UVR might potentially affect zoospores of S. dermatodea stronger than expected in clear waters.

Plant density is increasing in modern olive orchards to improve yields and facilitate mechanical harvesting. However, greater density can reduce light quantity and modify its quality. The objective was to evaluate plant morphology, biomass, and photosynthetic pigments under different red/far-red ratios and photosynthetically active radiation (PAR) combinations in an olive cultivar common to super-high-density orchards. In a greenhouse, young olive trees (cv. Arbequina) were exposed to low (L) or high (H) PAR with or without lateral FR supplementation (L+FR, L-FR, H+FR, H-FR) using neutral-density shade cloth and FR light-emitting diode (LED) modules. Total plant and individual organ biomass were much lower in plants under low PAR than under high PAR, with no response to +FR supplementation. In contrast, several plant morphological traits, such as main stem elongation, individual leaf area, and leaf angle, did respond to both low PAR and +FR. Total chlorophyll content decreased with +FR when PAR was low, but not when PAR was high (i.e., a significant FR*PAR interaction). When evaluating numerous plant traits together, a greater response to +FR under low PAR than under high PAR appeared to occur. These findings suggest that consideration of light quality in addition to quantity facilitates a fuller understanding of olive tree responses to a light environment. The +FR responses found here could lead to changes in hedgerow architecture and light distribution within the hedgerow.

The relationship between the seasonal Antarctic sea ice concentration (SIC) variability and the extratropical southern Indian Ocean (SIO) sea surface temperature (SST) is explored in this study. It is found that the Antarctic SIC in a wide band of the SIO, Ross Sea, and Weddell Sea is significantly related to an SIO dipole (SIOD) SST anomaly on the interannual time scale during austral spring. This relationship is linearly independent of the effects of El Niño–Southern Oscillation, the Indian Ocean dipole, and the Southern Hemisphere annular mode. The positive phase of the SIOD, with warm SST anomalies off of western Australia and cold SST anomalies centered around 60°E in high latitudes, stimulates a downstream wave train that induces large-scale cyclonic circulations over the SIO and the Ross and Weddell Seas. Subsequently, anomalous horizontal moisture advection causes water vapor divergence, changes the surface energy budget, and cools the underlying ocean, which leads to the increased SIC over the region in the SIO, Ross Sea, and Weddell Sea. This SIOD SST anomaly reached a record low during the austral spring of 2016 and promoted the prominent wave pattern at high latitudes, contributing to the dramatic decline of sea ice in the 2016 spring. In addition, the proportion of the SIC trend that is linearly congruent with the SIOD SST trend during austral spring is quantified. The results indicate that the trend in the SIOD SST may account for a significant component of the 1979–2014 SIC trend in the Ross Sea with the congruency peaking at 60%.

The nitrogen (N) response of competing plants may be affected by photosynthetically active radiation (PAR) availability and maximum potential growth rate, which determine N requirements. The responses of two crop (corn and soybean) and six weed species (common lambsquarters, common waterhemp, giant foxtail, velvetleaf, wild mustard, and woolly cupgrass) in low and high (150 and 450 μmol m−2s−1) PAR levels to daily fertilization with either low or high (0.2 or 7.5 mM) NH4NO3levels were studied. Leaf area of all species responded positively to N by 8 d after emergence (DAE) when grown in high PAR; in low PAR, most species did not respond until 11 DAE. Dry weight and leaf area of all species at 18 DAE were greater with high than with low N. These responses to high N were also greater in high than in low PAR for all species. Dry weights with high N were up to 100% greater in low PAR and up to 700% greater in high PAR than dry weights with low N. These responses suggest that low PAR reduced the benefit of N to the plants. The regression of relative growth rate (RGR) with high N to RGR with low N had a slope that was less than unity (β = 0.79), indicating that species with a higher RGR with high N experienced greater decreases in RGR with low N. Similarly, the sensitivity (change in RGR) of plants grown with high and low N was positively related to RGR with high N. RGR differences among crop and weed species may be related to differences in N requirement that could be exploited for weed management. RGR and seed size were negatively correlated, which may explain previous observations that small-seeded weeds were more sensitive to environmental stress.

Accurate forecasting of meteorological, hydrothermodynamic and ice characteristics in the Russian Western Arctic Seas using atmospheric circulation, marine circulation and sea ice models is currently impossible without assimilation of observational data. It improves the quality of the initial model state including hydrophysical and ice characteristics for carrying out forecasts. In this paper we present a technique for assimilation of sea surface temperature (SST) and sea ice concentration (SIC) satellite data in the INMOM marine circulation model using the DART (Data Assimilation Research Testbed) software with an assessment of the correctness of the assimilation algorithm used. A comparative analysis of the forecasts’ accuracy of the hydrothermodynamics reproduction with the assimilation of SST and SIC satellite data and without assimilation is carried out. It is shown that satellite data assimilation reduces the RMSE of the forecasts and observational data by 80% for SST and by 60–80% for SIC compared to the simulation without assimilation. Temporal variability of the RMSE in the SST and SIC forecasts shows that their largest errors are observed during the periods of intense heating of the upper sea layer and ice melting. The importance of joint SST and SIC data assimilation is noted: a more accurate reproduction of SST improves the accuracy of calculations of heat and salt fluxes at the ocean-ice boundary, which regulate the processes of thermal accretion/melting of ice, and, as a result, the reproduction of the ice area and its edge is improved. In turn, a more correct SIC calculation directly improves the accuracy of heat flux calculations at the water-air boundary and, thereby, SST improves.

As Germany accelerates its renewable energy transition aiming for 80% renewable electricity by 2030, the expansion of wind and solar capacity, the phase-out of fossil fuels, and improvements to grid infrastructure are crucial for ensuring a sustainable and secure energy system. In this context, seasonal forecasts of wind and solar radiation have the potential to support energy reserve management, planning for variable renewable supply, and improving the long-term resilience of the energy system. This study focuses on the development and evaluation of seasonal forecasts for 100m wind speed and solar radiation across Germany. We apply the statistical-dynamical downscaling method EPISODES (Kreienkamp et al., 2019) to hindcast data (1990–2020) from the German Climate Forecasting System Version 2.1 and investigate the predictability and forecast skill of 100m wind speed and solar radiation forecasts on lead times ranging from one to six months. The analysis focuses on the summer season, when solar energy production is highest, and the winter season, when wind energy production peaks. Despite the overall rather low forecast skill of seasonal forecasts for Germany, we find that skillful wind forecasts for the winter season are possible with a reasonable correlation to observations. Furthermore, the forecast model is able to predict solar radiation in summer over southern Germany, a region that contains most of the solar plants in Germany, relatively well. We further employ a statistically selected subsampling approach (Dalelane et al., 2020 and Dalelane et al. 2025, in preparation) to generate a smaller ensemble based on large-scale teleconnections in the North Atlantic and apply it to the forecasts. With this approach, we find a substantial increase in forecast skill for both wind and solar radiation in both summer and winter compared to the full ensemble. Our findings show that skillful seasonal forecasts in winter and summer are possible despite the limitations and challenges of seasonal prediction. In the future, we plan to use multi-model approaches and teleconnection indices to further explore potentials for more skillful seasonal prediction of wind and solar radiation and publish skillful forecasts on the DWD climate prediction webpage (http://www.dwd.de/climatepredictions). This user-oriented website consistently evaluates and displays subseasonal, seasonal and decadal climate predictions at high resolution for Germany.Kreienkamp, F., Paxian, A., Früh, B., Lorenz, P., & Matulla, C. (2019). Evaluation of the empirical–statistical downscaling method EPISODES. Climate dynamics, 52, 991-1026.Dalelane, C., Dobrynin, M., & Fröhlich, K. (2020). Seasonal forecasts of winter temperature improved by higher‐order modes of mean sea level pressure variability in the North Atlantic sector. Geophysical Research Letters, 47(16), e2020GL088717.

Grapevine morphological shade acclimation is mediated by light quality whereas hydraulic shade acclimation is mediated by light intensity

Abstract. We investigate the impacts of strong wind events on the sea ice concentration within the Ross Sea polynya (RSP), which may have consequences on sea ice formation. Bootstrap sea ice concentration (SIC) measurements derived from satellite SSM/I brightness temperatures are correlated with surface winds and temperatures from Ross Ice Shelf automatic weather stations (AWSs) and weather models (ERA-Interim). Daily data in the austral winter period were used to classify characteristic weather regimes based on the percentiles of wind speed. For each regime a composite of a SIC anomaly was formed for the entire Ross Sea region and we found that persistent weak winds near the edge of the Ross Ice Shelf are generally associated with positive SIC anomalies in the Ross Sea polynya and vice versa. By analyzing sea ice motion vectors derived from the SSM/I brightness temperatures we find significant sea ice motion anomalies throughout the Ross Sea during strong wind events, which persist for several days after a strong wind event has ended. Strong, negative correlations are found between SIC and AWS wind speed within the RSP indicating that strong winds cause significant advection of sea ice in the region. We were able to partially recreate these correlations using colocated, modeled ERA-Interim wind speeds. However, large AWS and model differences are observed in the vicinity of Ross Island, where ERA-Interim underestimates wind speeds by a factor of 1.7 resulting in a significant misrepresentation of RSP processes in this area based on model data. Thus, the cross-correlation functions produced by compositing based on ERA-Interim wind speeds differed significantly from those produced with AWS wind speeds. In general the rapid decrease in SIC during a strong wind event is followed by a more gradual recovery in SIC. The SIC recovery continues over a time period greater than the average persistence of strong wind events and sea ice motion anomalies. This suggests that sea ice recovery occurs through thermodynamic rather than dynamic processes.

SUMMARYThis research was done in order to explore genetic variation in carbon exchange rate (CER) of spring wheat (Triticum aestivum) leaves in response to variable photosynthetically active radiation (PAR) and to compare old and new Israeli cultivarsin this respect. Leaf gas exchange was measured in detached turgid leaves of 17 cultivars inan open system at 25 °C when PAR was reduced from c. 1200 to 200 μmol/m2 per s. Linear regressions of CER, stomatal conductance, transpirationand leaf internal CO2 concentration (Ci) on log PAR were fitted for each leaf(regression r2 was never <0·79) and the regressions were compared among cultivars by analysis of variance.Genotypes differed significantly for the slope (b) but not the intercept (a) of the regression of CER on log PAR, indicating that genotypic differences for CER increased with increasing PAR. Photosynthetic capacity, as expressed by the ratio of CER/Ci, differed significantly among cultivars only at high PAR. Stomatal conductanceand transpiration increased in a linear or a nonlinear fashion with log PAR and differences among cultivars for both were greatest at medium to low PAR. Photosynthetic water–use efficiency (WUE) and its variation among cultivars were greatest at the highest PAR. Genotypic variation in CER athigh PAR was confirmed by repeated results for 11 cultivars intwo independent experiments.The recently developed high-yielding cultivar V652 had a higher maximum CER, higher photosynthetic capacity and greater WUE at high PAR than older and lower-yielding cultivars. The results suggest an upward genetic shift in photosynthetic capacity andin CER at high PAR when selection for yield was performed under the high-irradiation conditions of Israel.

In the context of predicted alteration of sea ice cover and increased frequency of extreme events, it is especially timely to investigate plasticity within Antarctic species responding to a key environmental aspect of their ecology: sea ice variability. Using 13 years of longitudinal data, we investigated the effect of sea ice concentration (SIC) on the foraging efficiency of Adélie penguins (Pygoscelis adeliae) breeding in the Ross Sea. A ‘natural experiment’ brought by the exceptional presence of giant icebergs during 5 consecutive years provided unprecedented habitat variation for testing the effects of extreme events on the relationship between SIC and foraging efficiency in this sea-ice dependent species. Significant levels of phenotypic plasticity were evident in response to changes in SIC in normal environmental conditions. Maximum foraging efficiency occurred at relatively low SIC, peaking at 6.1% and decreasing with higher SIC. The ‘natural experiment’ uncoupled efficiency levels from SIC variations. Our study suggests that lower summer SIC than currently observed would benefit the foraging performance of Adélie penguins in their southernmost breeding area. Importantly, it also provides evidence that extreme climatic events can disrupt response plasticity in a wild seabird population. This questions the predictive power of relationships built on past observations, when not only the average climatic conditions are changing but the frequency of extreme climatic anomalies is also on the rise.

Antarctic sea ice formation is strongly influenced by polynyas occurring in austral winter. The sea ice production of Ross Ice Shelf Polynya (RISP) located in the Ross Sea is the highest among coastal polynyas around the Southern Ocean. In this paper, daily sea ice production distribution of RISP in wintertime is estimated during 2003–2015, and the spatial and temporal trends of ice production are explored. Moreover, the sensitivity of the ice production model to parameterization is tested. To define the extent of RISP, this study uses sea ice concentration (SIC) maps mainly derived from the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSRE) and the Advanced Microwave Scanning Radiometer 2 (AMSR2) by ARTIST (Arctic Radiation and Turbulence Interaction Study) sea ice algorithm (ASI) and constrains the ice production estimation to areas with SIC less than 75%. ERA-Interim reanalysis meteorological data are applied to a thermodynamic model to estimate daily ice production distribution between April and October during 2003–2015 for the open water fractions within the polynya. This estimation is conducted under the assumption that the meteorological data represent the reality. We further analyzed the spatial variability, monthly trend, and interannual trend for wintertime of the total RISP sea ice production. The results show that the ocean surface produces ice at a high rate within the distance of 20–30 km from the ice shelf front. In most high production areas, the ice production significantly increases. Some local regions show a contrarily significant decreasing trend as a result of ice shelf expansion and iceberg events. The monthly total RISP ice production ranges from 14 to 76 km3, showing substantial fluctuations in each month during 2003–2015. The seasonal variation of each year also shows substantial fluctuations. The wintertime total ice productions of RISP for 2003–2015 range 164–313 km3 with an average of 219 km3, showing no obvious temporal trend. More importantly, we conducted ten sensitivity tests, aiming to illustrate the sensitivity of the ice production model to parameterization. The output of the ice production model is sensitive to the value of the bulk transfer coefficients ( C s and C e ), latent heat of sea ice fusion ( L f ), and the threshold of SIC for RISP extent definition. C s and C e have the greatest influence, leading to a variation of average wintertime total RISP ice production results as high as 87.1%. A set of optimal local parameter values are recommended, including C s and C e = 0.002 and L f = 2.79 × 105 J·kg−1. L f is calculated by the salinity and temperature of sea ice, the value of which may lead to potential influence to the value of L f and the following ice production results.

The carbon balance and changes in leaf structure in Clusia minor L. were investigated in controlled conditions with regard to nitrogen supply and responses to low and high photosynthetically active radiation (PAR). Nitrogen deficiency and high PAR led to the production of smaller leaves with higher specific leaf dry weight (SLD W) and higher leaf water content, but with lower chlorophyll content. Nitrogen and PAR levels at growth also affected C02 exchange and leaf area. In — N conditions, total daily net C02 uptake and leaf area accumulation were slightly less for high-PTP-grown plants. In contrast, high-P/f P-grown plants supplied with nitrogen showed about a 4-fold higher total daily C02 uptake and about twice the total leaf area of low-PAR grown plants. Although total daily net C02 uptake of +N plants was only slightly higher than — N plants under the low PAR level, +N plants produced almost three times more leaf area but with lower SLDW. Under well-watered conditions, low-P/l P-grown plants showed only C02 evolution during the night and malic acid levels decreased. However, there was considerable night-time accumulation of titratable protons due to day/night changes in citric acid levels. High-PTP-grown plants showed net C02 uptake, malate and citrate accumulation during the dark period. However, most of the C02 fixed at night probably came from respiratory C02. Positive night-time C02 exchange was readily observed for low PA P-grown plants when they were transferred to high PAR conditions or when they were submitted to water stress. In plants grown in high and low PAR, CAM leads to a substantial increase in daily water use efficiency for water-stressed plants, although total net C02 uptake decreased.

Sunlight, including ultraviolet (UVA and UVB) and photosynthetically active radiation (PAR), is vital for the physiology of invertebrates with symbiotic Symbiodiniaceae. While the effects of UVB and PAR are well-studied, the impact of UVA remains underexplored. This study investigates the effects of varying UVA and PAR intensities on the metabolic, oxidative, and photosynthetic responses of Cassiopea andromeda jellyfish. Over 18 days, 24 medusae were exposed to four light treatments: low PAR (± low UVA) and high PAR (± high UVA). Results showed significant increases in jellyfish mass and umbrella diameter, with no differences between treatment groups. PAR intensity primarily drove aerobic respiration and photosynthesis, with reduced PAR enhancing ETS activity and chlorophyll-a concentration, while UVA had less effect. ETS activity was positively correlated with chlorophyll-a concentration but negatively with jellyfish size. Both high PAR and high UVA exposure increased lipid peroxidation (LPO), with the highest levels under combined high PAR and UVA. These findings show that UVA does not directly affect photosynthesis but might enhances oxidative stress when combined with high PAR, increasing LPO. Despite oxidative stress, jellyfish showed consistent growth and normal morphology, highlighting their resilience to varying light. Color changes linked to PAR exposure indicated shifts in algal symbiont density. This study highlights the adaptive capacity of C. andromeda jellyfish to fluctuating light, emphasizing PAR’s role in regulating metabolism and oxidative stress. It also offers new insights into UVA’s underexplored impact on jellyfish physiology, paving the way for future research on UVA’s broader effects on marine invertebrates.

The Vaucheria sp. microbial mats represent the most important primary producer in the tidal flat in Adventdalen, Svalbard. Its photosynthetic activity was monitored ex situ in a microcosm in late Arctic summer in 2016 and 2017 using variable chlorophyll fluorescence measurements with blue and red excitation lights. The effective quantum yield (FPSII) was measured, and the photosynthetic relative electron transport rate (rETR) was calculated. During the measurement period, the microclimate data, air temperature and photosynthetically active radiation (PAR), were recorded as well. Year 2016 was slightly warmer than year 2017. Despite of higher maximum PAR values found in 2016, the mean irradiance reached higher values in 2017 than 2016. When using red light excitation, the rETR and effective quantum yield values were lower than those measured using blue excitation light in 2016. However, opposite results were recorded in 2017, indicating thus rather sample-specific differences. According to redundancy analysis, the PAR was confirmed as the main driver of photosynthesis in late Arctic summer in both years. No serious photoinhibition, expressed as serious systematic decline of the rETR, was observed in both years indicating rapid photoacclimation of Vaucheria sp. photosynthesis to changing light environment. The air temperature was found to be less important driver of the photosynthetic activity. The inter-annual comparisons showed increased photosynthetic activity in 2017, probably caused by higher PAR in 2017, by differences in microcosmos design and/or heterogeneity of samples.