A predator's perspective on causal links between climate change, physical forcing and ecosystem response

The seasonal evolution of sea‐ice extent, concentration, and drift in the western Antarctic Peninsula (WAP) region, along with regional atmospheric synoptic variability, are described for a winter period (1992) when sea‐ice advance and retreat were both anomalously early. Daily time series of winds, opening and closing of the sea‐ice cover, and volume fluxes in and out of the WAP region indicate that synoptic variability in meridional winds determines whether the ice‐edge advances or retreats on daily to weekly timescales. The importance of this finding is that the dynamics, as opposed to the thermodynamics, initiate, and thereby dominate, in the production of ice‐edge anomalies. Further, the abrupt mid‐winter shift from persistently positive to negative ice‐edge anomalies indicates that there was a distinct change in the regional atmospheric circulation. The ice‐atmosphere interactions in the winter of 1992 are then compared to those in the winter of 1990, when sea‐ice advance and retreat were both late instead of early, but again the mid‐winter shift was abrupt. The comparison highlights possible circumpolar and tropical‐polar atmospheric linkages in the South Pacific that involve changes in the amplitude/phase of the semi‐annual oscillation (SAO), which in turn appear to be related to El Niño‐Southern Oscillation (ENSO) changes in the tropical Pacific. The implication of a dynamically driven ice‐atmosphere system, together with an intraseasonal ENSO linkage, further supports the idea that the WAP region is particularly sensitive to changes in the tropical Pacific.

While the Antarctic Slope Current (ASC) has been intensively studied for the East Antarctica slope area and the Weddell Sea, its fate in the western Antarctic Peninsula (WAP) region remains much less known. Data from two cruises conducted near the South Shetland Islands (SSIs) and the Elephant Island (EI), one in austral summer of 2004 and one in austral winter of 2006, were analyzed to provide a broad picture of the circulation pattern over the continental slope of the surveyed area, and an insight into the dynamical balance of the circulation. The results indicate that southwestward currents are present over the upper slope in the study area, indicating the ASC in the WAP region. Near the Shackleton Gap (SG) north of the EI, the southwestward slope currents near the shelf break are characterized by a water mass colder and fresher than the ambient water, which produces cross-slope density gradients and then vertical shear of the along-slope (or along-isobath) velocity. The vertical shear is associated with a reversal of the along-slope current from northeastward at surface to southwestward in deeper layers, or a depth-intensification of the southwestward slope currents. The water mass with temperature and salinity characteristics similar to the observed cold and fresh water is also revealed on the southern slope of the Scotia Sea, suggesting that this cold and fresh water is originated from the Scotia Sea slope and flows southwestward through the SG. Over the shelf north of the SSIs, the cold and fresh water mass is also observed and originates mainly from the Bransfield Strait. In this area, vertical structure of the southwestward slope currents is associated with the onshore intrusion of the upper Circumpolar Deep Water that creates cross-slope density gradients.

Multiscale control of bacterial production by phytoplankton dynamics and sea ice along the western Antarctic Peninsula: A regional and decadal investigation

BackgroundA population of humpback whales (Megaptera novaeangliae) spends the austral summer feeding on Antarctic krill (Euphausia superba) along the Western Antarctic Peninsula (WAP). These whales acquire their annual energetic needs during an episodic feeding season in high latitude waters that must sustain long-distance migration and fasting on low-latitude breeding grounds. Antarctic krill are broadly distributed along the continental shelf and nearshore waters during the spring and early summer, and move closer to land during late summer and fall, where they overwinter under the protective and nutritional cover of sea ice. We apply a novel space-time utilization distribution method to test the hypothesis that humpback whale distribution reflects that of krill: spread broadly during summer with increasing proximity to shore and associated embayments during fall.ResultsHumpback whales instrumented with satellite-linked positional telemetry tags (n = 5), show decreased home range size, amount of area used, and increased proximity to shore over the foraging season.ConclusionsThis study applies a new method to model the movements of humpback whales in the WAP region throughout the feeding season, and presents a baseline for future observations of the seasonal changes in the movement patterns and foraging behavior of humpback whales (one of several krill-predators affected by climate-driven changes) in the WAP marine ecosystem. As the WAP continues to warm, it is prudent to understand the ecological relationships between sea-ice dependent krill and krill predators, as well as the interactions among recovering populations of krill predators that may be forced into competition for a shared food resource.

Detecting vulnerability of humid tropical forests to multiple stressors

Intense moist intrusions originating from the lower latitudes of the Pacific Ocean have been found to have a significant impact on the Antarctic Peninsula (AP), including enhancement of surface melt events, increased runoff, reduction in sea-ice cover and ice shelves destabilization. Clouds play an important role in the surface energy budget during these events and in precipitation formation. Precipitation phase and amounts determine local and regional surface mass and energy budget. Our  research focuses on cloud and precipitation microphysical and dynamic characteristics over the AP region, using  ground based remote sensing at the Ukrainian Antarctic Station Akademic Vernadsky Moreover, an enhanced radiosonde program was launched during the austral winter at the Vernadsky station as part of the Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) international initiative (May-August 2022). Here we present detailed analysis of one of the Targeted Observing Periods (TOPs) during an intense moisture and heat intrusion affecting the AP.Although there is a lot of research on the atmospheric processes over the AP region, the local dynamic and microphysical characteristics of clouds and precipitation are still poorly understood and misrepresented in the models due to the lack of direct measurements, particularly in winter.Further we performed  Polar-WRF model simulations, forced by ERA5 reanalysis and configured with Morrison double moment cloud microphysical scheme. The simulations were run at 1-km spatial resolution with 10-minute temporal output centered over the Vernadsky region. Simulation results were verified with precipitation properties derived from Micro Rain Radar-Pro measurements and radiosonde profiles. We found that there is  more snow in PolarWRF outputs in comparison to MRR-Pro measurements. Thus it does not represent mixed phased precipitation properly. At the same time Polar WRF shows warm temperature bias compared to radiosounding. Measurements and model output are used to analyze cloud ice and water particle distribution, thickness and precipitation particle spectra over the Vernadsky station and the AP mountains during the extreme precipitation events in the Antarctic Winter. In overall there were five TOPs over the AP region. However, not all of them were associated with extreme precipitation on Vernadsky station.Our preliminary results show the importance of the transition between dry and wet snowfall during intense moisture transport events at the AP (particularly remarkable during winter at the location of Vernadsky station). Polar-WRF shows differences in simulating the timing and intensity of such transitions probably related to the biases in temperature profiles influencing the melting layer height.

In this study, we examined the interannual variability of net community production (NCP) in the Western Antarctic Peninsula (WAP) using in situ O2/Ar‐NCP estimates (2008–2014) and satellite data (SeaWiFS and MODIS‐Aqua) from 1997 to 2014. We found that NCP generally first peaks offshore and follows sea‐ice retreat from offshore to inshore. Annually integrated NCP (ANCP) displays an onshore‐to‐offshore gradient, with coastal and shelf regions up to 8 times more productive than offshore regions. We examined potential drivers of interannual variability in the ANCP using an Empirical Orthogonal Function (EOF) analysis. The EOF's first mode explains ∼50% of the variance, with high interannual variability observed seaward of the shelf break. The first principal component is significantly correlated with the day of sea‐ice retreat (R = −0.58,p < 0.05), as well as the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO) climate indices in austral spring. Although the most obvious pathway by which the day of sea‐ice retreat influences NCP is by controlling light availability early in the growing season, we found that the effect of day of sea‐ice retreat on NCP persists throughout the growing season, suggesting that additional controls, such as iron availability, are preconditioned or correlated to the day of sea‐ice retreat.

Rapid warming in the highly productive western Antarctic Peninsula (WAP) region of the Southern Ocean has affected multiple trophic levels, yet viral influences on microbial processes and ecosystem function remain understudied in the Southern Ocean. Here we use cultivation-independent quantitative ecological and metagenomic assays, combined with new comparative bioinformatic techniques, to investigate double-stranded DNA viruses during the WAP spring–summer transition. This study demonstrates that (i) temperate viruses dominate this region, switching from lysogeny to lytic replication as bacterial production increases, and (ii) Southern Ocean viral assemblages are genetically distinct from lower-latitude assemblages, primarily driven by this temperate viral dominance. This new information suggests fundamentally different virus–host interactions in polar environments, where intense seasonal changes in bacterial production select for temperate viruses because of increased fitness imparted by the ability to switch replication strategies in response to resource availability. Further, temperate viral dominance may provide mechanisms (for example, bacterial mortality resulting from prophage induction) that help explain observed temporal delays between, and lower ratios of, bacterial and primary production in polar versus lower-latitude marine ecosystems. Together these results suggest that temperate virus–host interactions are critical to predicting changes in microbial dynamics brought on by warming in polar marine systems.

Research on the mechanism of how climate change affects cultivated soil organic carbon is the basis for the management of cultivated land quality in the context of climate change. Crop phenological responses to climate change have an important effect on cultivated soil organic carbon as well. However, previous research primarily focused on the independent effects of climate change or crop phenological responses on the changes in soil organic carbon, and few studies have analyzed the changes in cultivated soil organic carbon under the combined influence of both factors or quantified their contribution rates to the changes in cultivated soil organic carbon. Based on topsoil samples in 2008 and 2021, annual pre-season and mid-season climate data from 2008 to 2021, and the phenological parameters extracted from the enhanced vegetation index （EVI） time series from 2007 to 2022, a soil organic carbon predictive model was constructed using the random forest algorithm. The total change in soil organic carbon from 2008 to 2021, the change in soil organic carbon under climate change alone, and the change in soil organic carbon under the synergistic influence of climate change and crop phenological responses were simulated. Furthermore, the contributions of climate change and crop phenological responses to the changes in cultivated soil organic carbon were distinguished and quantified. Moreover, the dominant influencing factors of soil organic carbon changes and their spatial distributions were identified and analyzed. The results were as follows： ① Under the synergistic influence of climate change and crop phenological responses, a decrease was observed in soil organic carbon in 74.15% of the cultivated land area in Fujian Province during the years 2008-2021, with an average decrease of 2.20 g·kg-1. Additionally, there was an increase in soil organic carbon in 25.85% of the cultivated area, with an average increase of 1.48 g·kg-1. ②The average contribution rates of pre-season climate, crop phenological responses to climate change, mid-season climate, and phenological changes resulting from cultivars shifts or other adjustments of agricultural measures to soil organic carbon changes were 34.08%, 28.56%, 22.75%, and 14.61%, respectively. Overall, climate change had a greater impact on the changes in cultivated soil organic carbon in Fujian Province than the crop phenological response to climate change. ③ The regions where climate change and phenological response jointly acted as dominant influencing factors held the largest area, accounting for 47.06% of the total cultivated land area in Fujian Province, and the regions where climate change was the dominant influencing factor alone held the second-largest area, accounting for 28.64% of the total cultivated land area. ④ Higher contribution rates of pre-season climate factors and phenological changes resulting from cultivar shifts or other adjustments of agricultural measures tended to be distributed in higher-altitude areas, whereas higher contribution rates of mid-season climate factors and phenological responses to climate change tended to be distributed in lower-altitude areas. These research findings can provide a theoretical basis for decision making regarding the management of cultivated land quality and the safeguarding of food security in the context of climate change.

Variability in modern sea surface temperature, sea ice and terrigenous input in the sub-polar North Pacific and Bering Sea: Reconstruction from biomarker data

Despite the backdrop of continuous global warming, sea ice extent has been found not to consistently decrease across the globe, and instead exhibit heterogeneous variability at middle to high latitudes. However, the existing studies are focused primarily on high latitude frozen seas, while studies on the long-term variability of sea ice cover at middle latitudes are generally lacking. Afforded by continuous satellite imagery, evolution of sea ice cover over nearly three decades from 1988 to 2015 in the Bohai Sea as a peculiar mid-latitude frozen sea area is reported for the first time. An anomalous trend of slight overall increase of 1.38 ± 1.00% yr–1 (R = 1.38, i.e. at a statistical significance of 80%) in Bohai Sea ice extent was observed over the 28 year period. The detrended annual average ice area (AAIA) was further found to correlate with a slight decreasing mean ice-period average temperature (IAT, r = –0.58, p < 0.01) of 11 meteorological stations around the Bohai Sea as well as a mild increasing cumulative freezing degree days (CFDD, r = 0.65, p < 0.01). Correlation with decreasing Arctic Oscillation (AO) index (r = –0.60, p < 0.01) and North Atlantic Oscillation (NAO) index (r = –0.69, p < 0.01) over the study period suggested AO and NAO as the primary large-scale climate factors for Bohai Sea ice. In addition, the seasonal cycle of ice cover showed a single peak with longer freezing phase than melting phase, due to the different temperature change rate during the freezing and melting phases. The results can provide important references for monitoring the recent climate change in the region and beyond.

Organic ligands determine the threshold of dissolved-Fe (DFe) concentrations in seawater. Understanding the processes controlling the dynamics of natural organic ligands is of fundamental importance towards a better understanding of the impact of global warming on the Fe cycle. However, there is a paucity of Fe speciation data to comprehensively assess the effects of global climate change on the biogeochemical cycle of Fe. Therefore, this thesis reports organic ligand properties in the oceanic regions that are vulnerable to global climate change and in an area subject to temporal variability. This thesis used an electrochemical approach, competitive ligand exchange - adsorptive cathodic stripping voltammetry (CLE-AdCSV). This method is an indirect method to determine organic ligand properties, the concentrations ([Lt] in nM equivalents of Fe (nM eq. Fe) and the conditional stability constant ("K" _"Fe'L" ^"cond" in M-1; it is shown in logarithmic value, log "K" _"Fe'L" ^"cond" ). &#13;\nThe study of dissolved organic Fe-binding ligands in Fram strait reveals that the binding strength of organic ligands regulates the export of DFe from the largest glacier of northeast Greenland. A high [Lt] (up to ~3 nmol eq. Fe), yet with relatively weak binding strength, is found in the vicinity of the glacier terminus. These relatively weak ligands compete less efficient against scavenging and precipitation, relative to the stronger ligands. &#13;\nIn the waters adjacent to the western Antarctic Peninsula, Fe-binding ligand concentrations and characteristics are investigated in different hydrographic regions. Under sea ice cover near the coast, organic ligand production is linked to ice-associated algae. Sediment-water interaction and resuspension result in high concentrations of DFe and ligands in upwelling deep waters over the continental slope. Towards the open ocean, phytoplankton blooms deplete nutrients and iron, while actively or passively producing organic ligands. The presence of fronts affects the distribution of the ligands, marking the border between shelf derived ligands and bloom-associated ligands offshore. &#13;\nThe Hauraki Gulf in New Zealand, serves as a natural laboratory to study DFe speciation in a highly variable system, where changes of the microbial ecosystem can have a profound effect on DFe speciation. In the shelf regions, [Lt] was relatively high (~2.5 to 7.5 nM eq. Fe). The high [Lt] enabled relatively high DFe to persist on the shelf, and consequently, increased the potential export of DFe from the shelf to the open ocean, where Fe can be an important driver of primary productivity.&#13;\nThis thesis reports the concentration, distribution, and characteristics of Fe-binding ligands in different ocean regions with distinct environmental circumstances, adding a valuable data set to expand our current knowledge about global Fe speciation. The study areas in Fram strait and the Northeast Greenland shelf, the Western Antarctic Peninsula, as well as the Hauraki Gulf, all have distinct hydrographic settings. The study areas in the high latitude oceans are particularly susceptible to changes in climate, and our results help provide the fundamental overview that is needed to predict the consequences of climate change on the Fe biogeochemical cycle in these globally important high latitude oceans.

Background: The rising concern about climate change and risks associated with it around the world and locally compared to the disproportionate level of awareness in Jos Metropolis inspired this study. Achieving adaptation to climate change always relies on the level of awareness. Hence effort must be made to intensify awareness. Though religious leaders in the study area have significant followership to positively change the tides of climate change awareness, risk perception, adaptation, and action, the opportunity is not harnessed. The study sought to project the role and attitude of religious leaders in Jos Metropolis in the global climate crisis. Methodology: Through a survey of a systematically drawn sample of 293 religious leaders using the Climate Change Survey Questionnaire (CCSQ), data was gathered to answer questions on climate change awareness, climate risk perception, attitude towards climate change, and the role of religious leaders in fighting the climate crisis. The reliability of the CCSQ was computed using the Cronbach Alpha method to be 0.98 after validation by experts in the field of Geography. Findings: Insights from the data suggest that religious leaders have a superficial awareness but lack meaningful awareness of climate change, giving rise to the shrouded perception of climate risks. Further, their attitude towards climate change issues was found to be positive, but not to the extent of neither taking individual measures to reduce climate change nor accepting organized media communications on climate change as factual. The level of awareness, risk perception, and attitude of the subjects under study were sufficient to inspire acceptance of climate change issues for discussions in churches/mosques and inclusion in their strategic plans. Findings also revealed that though nearly all the religious leaders have never taught in church/mosque on the subject of climate change or taken climate action in their immediate communities, the result shows the willingness of religious leaders to accept informed persons/experts to talk to their members on climate change. Recommendations: Considering the necessity of awareness in combating climate change, it is recommended that the government should seek opportunities to deepen awareness among religious leaders which could have a ripple effect on the Nigerian populace. Religious leaders were advised to teach or create platforms to bring awareness of climate change and its risks to their members. Circulation of climate laws and policies to religious leaders and the public is strongly advocated.

Southern Ocean pelagic productivity relies on the abundance of Antarctic krill Euphausia superba, which fluctuates on a 5-7 yr cycle and is driven by interannual variability in recruitment. The western Antarctic Peninsula (wAP) is home to a significant proportion of the circum-Antarctic krill biomass and is the focus of the krill fishery. The wAP is warming at a rate quicker than most other places on Earth, with notable regional changes in the pelagic ecosystem. There is a major gap in our understanding of how environmental variability affects the reproductive success of krill. We used historical krill population data collected at the wAP (January 1993-2008, Palmer Antarctica Long Term Ecological Research) to assess the effects of environmental variability on the condition of mature female krill during the spawning season and its relationship with krill recruitment. Mature female krill condition during the spawning season was positively correlated with recruitment the subsequent year. Results of generalized additive models indicated that the predominant drivers of krill condition during the spawning season were climatological (Southern Annular Mode and Multivariate El Niño Southern Oscillation Index), though the timing of sea ice advance and retreat, and diatom concentrations were also important. Gaining a better understanding of the oceanographic and climatological factors that affect the physiological condition of mature female krill is critical for predicting future demographic patterns and responses to change. Results from our study emphasize the importance of including the effects of climate change in the management models for the Antarctic krill fishery.

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 15:303-310 (1998) - doi:10.3354/ame015303 Ectoaminopeptidase specificity and regulation in Antarctic marine pelagic microbial communities James R. Christian*, David M. Karl School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822, USA *Present address: Universities Space Research Association, NASA/GSFC, Code 970.2, Greenbelt, Maryland 20771, USA. E-mail: jrc@bluefin.gsfc.nasa.gov ABSTRACT: Ectoaminopeptidase activities of pelagic marine microbial communities were investigated on several research cruises in the western Antarctic Peninsula region from 1992 to 1994, using the fluorigenic substrate analogue L-leucyl- β-naphthylamine. Km values at in situ temperature were comparable to those observed by other investigators for a variety of aquatic environments. Competitive inhibition by dipeptides of a variety of amino acids showed that the aminopeptidases present were broadly specific; no strong tendency toward greater affinity for hydrophobic or hydrophilic amino acids was observed. Seawater cultures (1.0 μm filtrate) were inoculated with a variety of monomeric organic compounds and incubated for 24 to 72 h prior to activity determination; histidine and phenylalanine were found to consistently inhibit aminopeptidase expression. It is hypothesized that auxotrophy for histidine and phenylalanine may be widespread in these assemblages, giving rise to high levels of constitutive, nonspecific aminopeptidase activity which results in significant respiration of the more common amino acids. Whatever the exact mechanism, aminopeptidase activity is strongly affected by the specific compounds present and not simply by the carbon-to-nitrogen ratio. KEY WORDS: Aminopeptidase · Enzyme specificity · Enzyme regulation · Antarctica Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 15, No. 3. Publication date: August 31, 1998 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1998 Inter-Research.