Climate-driven Environmental Change Research Articles

A Tapestry of Human-Induced and Climate-Driven Environmental Change in Western Uganda: The Ndali Crater Lakes Region

Abstract Recent archaeological and paleoenvironmental research in the Ndali Crater Lakes Region (NCLR) of western Uganda provide important new insights into anthropogenic impacts on moist forests to the East of the Rwenzori Mountains. This research significantly changes previous interpretations of paleoenvironmental records in western Uganda and helps to distinguish climate change from human impacts. By drawing on multiple sources such as historical linguistics, archaeological evidence, and environmental proxies for change, a new picture emerges for a region that was a cultural crossroads for early Bantu-speakers and Central Sudanic-speakers between 400 BCE and 1000 CE. Detailed archaeological data and well-dated sites provide fine-grained evidence that closely fits episodes of significant environmental change, including a later and separate phase of forest clearance, soil degradation, and lake pollution caused by the saturation of the landscape by Bigo-related populations between 1300 and 1650 CE. Fresque de changements environnementaux induits par l’homme et le climat dans l’ouest de l’Ouganda : la région des lacs du cratère de Ndali

Sentinel protist taxa of the McMurdo Dry Valley lakes, Antarctica: a review

High-latitude meromictic lakes such as those in the Antarctic McMurdo Dry Valleys (MDV) harbor aquatic ecosystems dominated by the microbial loop. Within this habitat, which is limited year-round by light and nutrients, protists, or single celled eukaryotes, play outsized roles in the food web as the dominant primary producers and the apex predators. Thus, the MDV lake ecosystem represents an ideal system to study the role of sentinel protist taxa in carbon and nutrient cycling. The perennially ice-covered lakes are part of the McMurdo Long Term Ecological Research (McM LTER; mcmlter.org) established in 1993. In this review we will highlight the diversity and trophic roles of the MDV lake protist community and compare environmental factors driving spatiotemporal patterns in key protist taxa in two lakes within the McM LTER, Lakes Bonney and Fryxell. We will then discuss lessons learned from manipulated experiments on the impact of current and future climate-driven environmental change on sensitive protist taxa. Last, we will integrate knowledge gained from 25 years of lab-controlled experiments on key photosynthetic protists to extend our understanding of the function of these extremophiles within the MDV aquatic food webs. Our research group has studied the distribution and function of the MDV microbial community for nearly two decades, training the next generation of scientists to tackle future problems of these globally significant microbes. This review article will also highlight early career scientists who have contributed to this body of work and represent the future of scientific understanding in the Anthropocene.

Whole genome sequencing reveals stepping-stone dispersal buffered against founder effects in a range expanding seabird.

Many species are shifting their ranges in response to climate-driven environmental changes, particularly in high-latitude regions. However, the patterns of dispersal and colonization during range shifting events are not always clear. Understanding how populations are connected through space and time can reveal how species navigate a changing environment. Here, we present a fine-scale population genomics study of gentoo penguins (Pygoscelis papua), a presumed site-faithful colonial nesting species that has increased in population size and expanded its range south along the Western Antarctic Peninsula. Using whole genome sequencing, we analysed 129 gentoo penguin individuals across 12 colonies located at or near the southern range edge. Through a detailed examination of fine-scale population structure, admixture, and population divergence, we inferred that gentoo penguins historically dispersed rapidly in a stepping-stone pattern from the South Shetland Islands leading to the colonization of Anvers Island, and then the adjacent mainland Western Antarctica Peninsula. Recent southward expansion along the Western Antarctic Peninsula also followed a stepping-stone dispersal pattern coupled with limited post-divergence gene flow from colonies on Anvers Island. Genetic diversity appeared to be maintained across colonies during the historical dispersal process, and range-edge populations are still growing. This suggests large numbers of migrants may provide a buffer against founder effects at the beginning of colonization events to maintain genetic diversity similar to that of the source populations before migration ceases post-divergence. These results coupled with a continued increase in effective population size since approximately 500-800 years ago distinguish gentoo penguins as a robust species that is highly adaptable and resilient to changing climate.

Changing nutritional seascapes of kelp forests

Ocean warming and short-term extreme events (e.g. marine heatwaves) are becoming more intense and frequent and have had major impacts on ecosystems. Seaweeds are foundational components of temperate reefs, providing nutrition for a diversity of species and underpinning temperate food webs. While the impacts of climate-driven environmental change on seaweed distribution, abundance and interactions are well studied, potential impacts on the provision of nutrients from seaweeds and their availability to consumers remain poorly understood. Here, we use metabolomic and lipidomic approaches to understand how the provision of nutrients from key seaweeds may be altered under climate change. We optimize a small-scale microextraction technique to test the effects of warming and marine heatwaves on the nutritional quality of two Australian habitat-forming seaweeds; Ecklonia and Sargassum. We then model changes in lipid availability in response to climate-driven ocean warming throughout Ecklonia’s eastern Australian distribution. Contrary to expectations, ocean warming and marine heatwaves had limited effects on seaweed nutritional quality, indicating resilience in the nutritional value of these species to climate-driven warming. However, nutritional quality varied significantly between species, which presents new implications for predicted species redistributions from the base of the food chain. Modelling revealed a projected net loss of 3.5% of lipids across the east coast of Australia by 2100 under RCP 8.5 in response to shifts in the redistribution of Ecklonia biomass. The climate-driven redistribution of seaweeds is likely to alter the availability of seaweed-derived nutrients to consumers, which may have broad implications for the transfer of energy within temperate marine food webs.

On the timing of megafaunal extinction and associated floristic consequences in Australia through the lens of functional palaeoecology

The timing and cause of megafaunal extinctions are an enduring focus of research interest and debate. Despite the developments in the analysis of coprophilous fungal spores (CFS), the proxy for reconstructing past megaherbivore changes, the environmental consequences of this fauna loss remain understudied. This is partly due to the general obscurity of such a signal in pollen records, as well as limitations in disentangling human and extinction ecological impact, and the lack of spatial information of megafauna changes in site-level sedimentary records. In Australia, the debate centres on the possibility that habitat loss through climate change, vegetation-fire change, human intervention, or a combination of these factors led to the extinction of some large animals during the Late Pleistocene. Pollen and plant isotope studies have also demonstrated that vegetation-fire responses following the Late Pleistocene megafaunal extinctions were characterized by increased vegetation density and fire activity due to reduced grazing/browsing pressure. Here, we use a well-dated marine sedimentary core record from the Murray Darling Basin in southern Australia and apply palynological and functional palaeoecological approaches to reconstruct the Late Pleistocene megafaunal abundance changes, the timing and potential cause of extinction across the basin and investigate if extinction was associated with any signal of trait-based vegetation changes. We infer megafaunal abundance changes from the abundance of CFS and compare this with climatic proxies from the same core. We then link modern observations of fruit, seed and fire response traits of plant genera within the basin to the fossil pollen record to reconstruct palaeo vegetation community traits and determine if extinction was associated with any changes in plant community trait composition. Closely-spaced 14C dates obtained from planktonic foraminifera and δ18O tie points place a major decline in CFS, and thus the timing of extinction, within the basin at ∼43.3 ka. While climate-driven environmental changes largely controlled megafaunal presence, human arrival and frequent landscape burning are considered the most likely primary cause of extinction or, at the very least, megafauna decline in the Murray Darling Basin. We also found that the proposed period of megafaunal decline was also accompanied and followed by a decline in the prevalence of plants with larger seeds and fruits that were likely to have been once dispersed by megaherbivores. Our study supports the idea of a human-driven megafaunal extinction in mainland Australia and that the extinction caused changes in vegetation due to reduced plant dispersal and herbivory. However, high fire activity primarily linked to these vegetation changes was not observed, as humans were already practicing landscape burning before the period of megafaunal extinction and likely continued to do so afterward.

Widespread regeneration failure in ponderosa pine forests of the southwestern United States

As climate changes in coming decades, ponderosa pine forest persistence may be increasingly dictated by their regeneration. Sustained regeneration failure has been predicted for forests of the southwestern US (SWUS) even in absence of stand-replacing wildfire, but regeneration in undisturbed and lightly disturbed forests has been studied infrequently and at a limited number of locations. We characterized 77 ponderosa pine sites in 7 SWUS locations, documented regeneration occurring over the past ∼20 years, and utilized gridded meteorological estimates and water balance modeling to determine the climate and environmental conditions associated with regeneration failure (R0). Of these sites, 29% were R0, illuminating that regeneration failure in these forests is widespread. R0 sites were distinguished by high above- and belowground heat loading, loss of cool-season climate, and high soil moisture variation. Explanatory variables had high accuracy in identifying R0 sites, and illustrate the climate-driven pathway by which regeneration failure has occurred in the SWUS. Regeneration failure has high potential to increase in a warmer, more hydrologically variable climate, and expand regionally from lower to higher latitudes. Yet, we also found that human management interventions were associated with environmental conditions that avoided regeneration failure. To counteract regeneration-associated forest declines, interventions will need to influence climate-driven environmental change by adjusting forest characteristics at local scales. Regeneration failures are a major threat to ponderosa pine forest persistence, and they have potential to intensify and expand in a changing climate.

Towards more inclusive and solution orientated community-based environmental monitoring

Rapid climate-driven environmental change continues to threaten front-line communities that rely on Arctic landscapes to sustain their way of life. Community-Based Monitoring (CBM) can increase our knowledge of environmental change and understanding of human-environment interactions occurring across the Arctic. However, the depth of CBM research outcomes have been limited by an imbalance in contributions from external researchers and community members. A detailed literature analysis revealed that the number of studies documenting CBM approaches in Inuit Nunangat (Inuit homeland in Canada) have increased over the last decade. We identify that bottom-up guiding protocols including the National Inuit Strategy on Research, has increased community engagement in Arctic research processes and equitable outcomes. However, these increases have been concentrated on wildlife-based research where consistent funding streams and pre-existing alignment with community priorities exist. To explore the potential for guiding principles to be more successfully incorporated into impactful CBM, we present a co-developed environmental CBM case study aiming to document and aid understanding of climate-driven landscape change near Tuktoyaktuk, Inuvialuit Settlement Region, Canada since 2018. A foundation of early dialogue and collaborative partnerships between community members and external researchers formed the basis of a community-based climate monitoring program driven by community research priorities. A succession of funded CBM projects at Tuktoyaktuk demonstrated that longer term and resilient climate monitoring can bring together Scientific and Indigenous knowledge systems. Progressing beyond an emphasis on data collection is vital to sustain monitoring efforts, capacity sharing and co-dissemination processes to ensure research is communicated back in a way that is understandable, relevant, and usable to address community priorities. The need for successful CBM is often at odds with current research funding structures, which risks a fragmented mosaic of early-stage initiatives focused on understanding environmental problems rather than sustained and progressive research development towards cooperative solutions.

Late-Middle Pleistocene Sedimentary Environment and Climate Variation in North Hebei Plain, China: Evidence from the SHBZK-1 Core

Thick Quaternary alluvial and floodplain sediments in north Hebei Plain provide important information for understanding local paleoenvironmental and paleoclimatic variations. A 120.8 m drilled core (SHBZK-1) was recovered to determine the late Pleistocene climatic fluctuations, sedimentary environment and their coevolutionary relationship. Laboratory analysis, including grain size distribution, magnetic susceptibility, and optical stimulated luminescence dating, was carried out. Lithofacies and grain size showed that the sediments are of fluvial origin and contain two subfaces: river sand bar and flood plain. The good correlation between magnetic susceptibility and grain size show that climate change is the main factor controlling the variation of sedimentary environment in Hebei Plain, rather than tectonic factors. Furthermore, variations of the magnetic susceptibility and lithofacies reflect the intensity and fluctuations of Asian monsoons and couple well with glacial-interglacial cycles, suggesting that the variation of ice volume in the Northern Hemisphere drives climate change in the Hebei Plain, which, in turn, regulates the variation of the sedimentary environment and facies through controlling precipitation changes, as well as the input amount of magnetic minerals. This research provides a useful continental archive for understanding the late Pleistocene environmental and climatic variation and suggests the prevalence of climate-driven environmental change.

Spirituality and Sustainable Development: A Systematic Word Frequency Analysis and an Agenda for Research in Pacific Island Countries

While different in emphasis, spirituality and sustainable development are intertwined concepts that cannot be meaningfully discussed in isolation from each other. This is especially pertinent in Pacific Island countries that are characterised by both high degrees of vulnerability to climate change and high degrees of religious engagement. There is a paucity of research that examines the relationship between spirituality and sustainable development in contemporary human development discourse. To address this gap in the literature, this research employs an inductive and exploratory methodological approach to the study of major development organisations in Australia. It investigates what significance contemporary NGOs ascribe to matters of spirituality in the design and implementation of their community aid and development programming in the Pacific and beyond. To achieve its goal, the study conducts a systematic term frequency analysis in the annual reports of government-funded and independently funded NGOs, both faith-based and secular. It extends previous research by focusing expressly on the intersectionality of sustainable development and spirituality as a fertile space for interdisciplinary inquiry. The findings link development policy and practice more closely to the needs and worldviews of Pacific peoples. A better understanding of the spirituality–sustainability nexus will enable more effective, sustainable, equitable, ethical, and culturally acceptable development programming. Crucially, integrated approaches promise to make ongoing community development programmes and adaptation responses to climate-driven environmental change more effective and sustainable. Finally, it is an important aim of this study to conceptualise various opportunities for future research, thus laying the foundation for an important emergent research agenda.

Size-differential photosynthetic traits of phytoplankton in the Chukchi Sea

Understanding size-differential productivity characteristics of phytoplankton is important to evaluating climate-driven environmental changes in marine ecosystems. In this study, we derived the relative contribution of small phytoplankton (Psmall; <5 μm) to the total primary production (TPP) and characterized their photosynthetic traits in comparison to large phytoplankton (Plarge) based on field-measured observations in the Chukchi Sea, 2012. The overall chlorophyll-a (51.8 ± 23.1%) and TPP contributions (52.3 ± 29.8%) of Psmall observed in this study were closely related to freshwater contents. In regards to nitrogen uptake, Psmall contributed 39.0% (S.D. = ± 28.4%) and 73.4% (S.D. = ± 50.1%) to the total nitrate uptake rate (TNP) and the total ammonium uptake rate (TAP), respectively, which is consistent with previous findings. Particulate and assimilated carbon/nitrogen (C/N) ratios were significantly (p < 0.01 and 0.05, respectively) lower in Psmall compared to Plarge, indicating their different natural capacities during growths. A significantly negative relationship was observed between the Psmall contribution and the TPP in the Chukchi Sea. These results imply that the more Psmall contribution in marine ecosystems could lead the less C sequestration from euphotic depths to deep ocean. In comparison to other regions, a more rapid decreasing TPP in the Chukchi Sea with increasing Psmall contribution is distinctively noticeable, which suggest that the Chukchi Sea ecosystem could be more vulnerable to an expected increase in Psmall contribution.

Stronger adaptive response among small-scale fishers experiencing greater climate change hazard exposure

Progressive climate-driven environmental changes are threatening the global livelihoods of small-scale fishers, yet how their adaptation responses vary in relation to hazard exposure is poorly understood. We use a systematic review approach to identify a global data set of 301 reported adaptation responses (remaining, adaptive, and transformative) of small-scale fishers to climate change and analyse their spatial agreement with estimated geographical location of global coastal hotspot areas for specific climate change hazards associated to those responses (long-term trends in sea surface temperature, cumulative intensity of marine heatwaves, frequency of tropical storms, and intensity of associated storm surges). Only 37% of responses were found in climate change hotspots. Despite this, our results evidence that fishers are responding more passively in areas with lower exposure levels to abrupt climatic events. The relative proportion of adaptive and transformative responses increase with climate change hazard exposure.

Seagrass Factor in Climate Change Mitigation in the Philippines

Despite their importance, seagrasses are facing a global decline due primarily to increased nutrient loading and sedimentation resulting from deforestation and agriculture, and, more recently, from seawater warming in shallow coastal waters. With the advent of new technology and a concerted understanding of seagrass ecosystems as vulnerable social-ecological systems, there has been a dramatic increase in the number of studies focusing on the effects of climate change on seagrasses. Here, I provide an account of the status, role, and future of Philippine seagrasses in an era of climate-driven environmental change. I have gathered information from published studies and actual accounts to identify potential commonalities in the effects of climate change and the responses of seagrasses across the molecular, community, and ecosystem levels. Occupying 13.3% or 4,826 km of the total length of the Philippine coastline, seagrass species composition and diversity remain relatively stable. The seagrass beds of the Philippines and Southeast Asia are declining at an estimated rate of 2.62% or 391 km2 yr–1. Coupled with the apparent neglect in accounts of global carbon, this decline indicates a potential to lose an effective source of blue carbon useful in mitigating the impacts of climate change. In this study, I evaluate the combined effects of climate change with other environmental stressors on the ecosystem services of seagrasses and emphasize the need to apply the lessons learned from three decades of local studies to provide a more inclusive science-based knowledge of seagrass- climate interaction and a deeper understanding of the ecosystem’s resilience. I conclude by presenting the most significant knowledge and management gaps and future directions for seagrass research in the Philippines.

The Extremes of Disturbance Reduce Functional Redundancy: Functional Trait Assessment of the Shallow Antarctic Benthos

Climate-driven changes in disturbance are a major threat to ecosystem Functional diversity. The selective mechanisms underlying ecosystem response to disturbance are far from universal and remain the subject of scientific debate. Ice scouring of the shallow Antarctic benthos is one of the largest disturbance gradients in the natural environment and thus provides an opportunity to investigate how disturbance gradients influence functional structure of a biological assemblage. The Western Antarctic Peninsula, in particular, is a hotspot of climate-driven environmental change. Addressing how this system might respond to species loss is critical. Previous surveys across the shallowest 100 m of the seabed, detected unimodal changes in diversity and a shift in assemblage composition in response to disturbance gradients. This study investigated how functional traits and associated functional diversity change across the depth gradient. Our results revealed that selective mechanisms, such as disturbance filtering and inter-species competition, reduce functional redundancy at the extremes of the disturbance gradient. Our study highlights areas of potential vulnerability to future environmental change due to low functional redundancy. Threatening the important negative (mitigating) feedbacks on climate change, through blue carbon, currently provided by Antarctic continental shelf benthic assemblages.

Radiocarbon dating from Yuzhniy Oleniy Ostrov cemetery reveals complex human responses to socio-ecological stress during the 8.2 ka cooling event.

Yuzhniy Oleniy Ostrov in Karelia, northwest Russia, is one of the largest Early Holocene cemeteries in northern Eurasia, with 177 burials recovered in excavations in the 1930s; originally, more than 400 graves may have been present. A new radiocarbon dating programme, taking into account a correction for freshwater reservoir effects, suggests that the main use of the cemetery spanned only some 100-300 years, centring on ca. 8250 to 8000 cal BP. This coincides remarkably closely with the 8.2 ka cooling event, the most dramatic climatic downturn in the Holocene in the northern hemisphere, inviting an interpretation in terms of human response to a climate-driven environmental change. Rather than suggesting a simple deterministic relationship, we draw on a body of anthropological and archaeological theory to argue that the burial of the dead at this location served to demarcate and negotiate rights of access to a favoured locality with particularly rich and resilient fish and game stocks during a period of regional resource depression. This resulted in increased social stress in human communities that exceeded and subverted the 'normal' commitment of many hunter-gatherers to egalitarianism and widespread resource sharing, and gave rise to greater mortuary complexity. However, this seems to have lasted only for the duration of the climate downturn. Our results have implications for understanding the context of the emergence-and dissolution-of socio-economic inequality and territoriality under conditions of socio-ecological stress.

Understanding risks and consequences of pathogen infections on the physiological performance of outmigrating Chinook salmon.

The greatest concentration of at-risk anadromous salmonids is found in California (USA)—the populations that have been negatively impacted by the degradation of freshwater ecosystems. While climate-driven environmental changes threaten salmonids directly, they also change the life cycle dynamics and geographic distribution of pathogens, their resulting host-pathogen interactions and potential for disease progression. Recent studies have established the correlation between pathogen detection and salmonid smolt mortality during their migration to the ocean. The objective of the present study was to screen for up to 47 pathogens in juvenile Chinook salmon (Oncorhynchus tshawytscha) that were held in cages at two key sites of the Sacramento River (CA, USA) and measure potential consequences on fish health. To do so, we used a combination of transcriptomic analysis, enzymatic assays for energy metabolism and hypoxia and thermal tolerance measures. Results revealed that fish were infected by two myxozoan parasites: Ceratonova shasta and Parvicapsula minibicornis within a 2-week deployment. Compared to the control fish maintained in our rearing facility, infected fish displayed reduced body mass, depleted hepatic glycogen stores and differential regulation of genes involved in the immune and general stress responses. This suggests that infected fish would have lower chances of migration success. In contrast, hypoxia and upper thermal tolerances were not affected by infection, suggesting that infection did not impair their capacity to cope with acute abiotic stressors tested in this study. An evaluation of long-term consequences of the observed reduced body mass and hepatic glycogen depletion is needed to establish a causal relationship between salmon parasitic infection and their migration success. This study highlights that to assess the potential sublethal effects of a stressor, or to determine a suitable management action for fish, studies need to consider a combination of endpoints from the molecular to the organismal level.

Climate Change as an International Security Issue

The security paradigm of the world is constantly shifting, and compared to the military and traditional issues, non-military problems are now given significantly greater emphasis. Threats to a person's life and wellness that fall beyond the usual definition of security include climate change. Climate Change has taken a central position on the international forum. The purpose of this study is to analyze climate-driven environmental changes that are anticipated to influence some of the factors that threaten security; undermine livelihoods, increase migration, create political instability or other forms of insecurity, and weaken the capabilities of states to respond to challenges appropriately. Some major international issues such as population growth, pollution, melting of ice glaciers, floods, and droughts are interlinked with the above-said problems and are also becoming the core issues within states and borders. Climate Change may result eventually in a plethora of security risks and threats that can also exacerbate conflicts. The purpose of the study is to examine either climate change is a critical issue or whether the states just politicize it. This study aims to investigate how climate change affects security and public perception to recommend policy solutions to these ever-evolving problems. Security is a multidimensional approach that focuses on an individual’s welfare and well-being. Improvement of policymaking in handling the issue of climate change is also a very important factor for peace and human security at the international level.

2400 years of climate and human-induced environmental change recorded in sediments of Lake Młynek in northern Poland

Abstract. In the densely forested Warmia and Masuria region (northern Poland) there are many small endorheic lakes characterized by their low sedimentation rate, which makes them excellent archives of Holocene environmental and palaeoclimatic change. Lake Młynek, located near the village of Janiki Wielkie, was selected for multi-faceted palaeoenvironmental research supported with radiocarbon dates. Sediments from this lake also contain unique information about human impact on the environment, because a stronghold has been operating on its northern shore since the early Iron Age to the early Medieval period, giving the opportunity to correlate palaeoenvironmental data with the phases of human activity over the last 2400 years. During the second and third centuries BCE the lake was surrounded by a dense deciduous forest. From the first century BCE to second century CE the forest around the lake was much reduced, which can be associated with the first pre-Roman (La Tène) and Roman occupation phase evidenced by the construction of the stronghold located close to the lake. From the second up to ninth century CE gradual restoration of the forest and a decline in human activity took place, along with lake deepening and the onset of a colder and humid climatic phase which corresponded to the global cooling episode known as the Bond 1 event (1.5 ka BP). The next intensive phase of forest clearing around the lake occurred between the 9th–13th century CE as result of human activity (Middle Age settlement phase of the stronghold). Whilst this period is marked by a warming, the human impact which has transformed the landscape likely overprints any signals of climate-driven environmental changes.

A revised, Last Interglacial chronology for the Middle Palaeolithic sequence of Gruta da Oliveira (Almonda karst system, Torres Novas, Portugal)

Based on previous radiocarbon and U-series (Diffusion/Adsorption) dating of bone samples, the Middle Palaeolithic has been thought to persist at Gruta da Oliveira until ∼37 thousand years (ka) ago. New U-series ages for stratigraphically constraining speleothems, coupled with new luminescence ages for sediment infill, show that the site’s ∼6 m-thick archaeological stratigraphy dates entirely within a <30 ka interval spanning substages 5a-5b of Marine Isotope Stage (MIS) 5. Significant technological change is observed across the sequence, akin to that seen in the Upper Palaeolithic over similar timescales. Flake-cleavers and bifaces, normatively definitional of the Vasconian facies, are restricted to a short interval correlated with Greenland Stadial (GS) 22, 85.1–87.6 ka ago. In cave and rock-shelter sites of southern and western Iberia, intact archaeological deposits securely dated to the ∼37–42 ka interval remain elusive. Geological dynamics (e.g., erosion, sedimentation hiatuses, palimpsest formation) and human adaptive responses to climate-driven environmental change (e.g., abandonment of now forest-covered low- and mid-altitude karst areas, concentration of settlement in alluvial plains and coastal settings) are possible explanations for this pattern.

Different Biochemical Compositions of Particulate Organic Matter Driven by Major Phytoplankton Communities in the Northwestern Ross Sea.

Marine particulate organic matter (POM) largely derived from phytoplankton is a primary food source for upper trophic consumers. Their biochemical compositions are important for heterotrophs. Especially, essential amino acids (EAAs) in phytoplankton are well known to have impacts on the survival and egg productions of herbivorous zooplankton. To estimate the nutritional quality of POM, the biochemical compositions [biomolecular and amino acid (AA) compositions] of POM were investigated in the northwestern Ross Sea during the late austral summer in 2018. Carbohydrates (CHO) accounted for the highest portion among different biomolecules [CHO, proteins (PRT), and lipids (LIP)] of POM. However, the higher contribution of PRT and lower contribution of CHO were observed in the southern section of our study area compared to those in the northern section. The spatial distribution of total hydrolyzable AAs in POM was considerably influenced by phytoplankton biomass, which indicates that the main source of particulate AA was generated by phytoplankton. Our results showed that the relative contribution of EAA to the total AAs was strongly associated with EAA index (EAAI) for determining protein quality. This result indicates that higher EAA contribution in POM suggests a better protein quality in consistency with high EAAI values. In this study, variations in the biochemical compositions in POM were principally determined by two different bloom-forming taxa (diatoms and Phaeocystis antarctica). The southern region dominated majorly by diatoms was positively correlated with PRT, EAA, and EAAI indicating a good protein quality, while P. antarctica-abundant northern region with higher CHO contribution was negatively correlated with good protein quality factors. Climate-driven environmental changes could alter not only the phytoplankton community but also the physiological conditions of phytoplankton. Our findings could provide a better understanding for future climate-induced changes in the biochemical compositions of phytoplankton and consequently their potential impacts on higher trophic levels.

Latitudinal Cline in Chromosome Numbers of Ice Cod A. glacialis (Gadidae) from Northeast Greenland

The ice cod Arctogadus glacialis (Peters, 1872) is one of the few fish species endemic to the Arctic. With a circumpolar distribution, the species is confined to the fjords and shelves of the Arctic seas. Biological information on A. glacialis is scarce, with genomic information restricted to microsatellites. Within the frame of the TUNU-Programme: Arctic Ocean Fishes—Diversity, Adaptation and Conservation, we studied A. glacialis at the chromosomal level to explore fish diversity and evolutionary aspects. The analysis of over 50 individuals from the Northeast Greenland fjords between latitudes 71°09′ N and 76°42′ N revealed a remarkable intraspecific diversity epitomized by chromosome numbers spanning from 28 to 33, the occurrence of putative B chromosomes, and diversified patterns of distribution of heterochromatin and rDNAs. The number of B chromosomes followed a latitudinal gradient from 0–2 in the north to 2–5 in the south. Considering the benthic and rather stationary life history of this species, the observed chromosomal differences might have arisen independently, possibly driven and/or fostered by the dynamics of repetitive sequences, and are being fixed in relatively isolated fjord populations. The resulting latitudinal cline we observe today might have repercussions on the fate of local populations facing the ongoing climate-driven environmental changes.