Structure, inter-annual variability, and long-term change in zooplankton communities of the Chukchi Sea

Thesis (Ph.D.) University of Alaska Fairbanks, 2016The Chukchi Sea is a complex transition zone between the Pacific and Arctic Oceans that has been experiencing dramatic change in recent decades due to shifting sea ice cover and increasing temperatures. We examine summer mesozooplankton communities of the Chukchi Sea in Alaskan and Russian waters during summers 2004, 2009, 2010 and 2012 within the scope of the RUSALCA (Russian-American Long Term Census of the Arctic) program. Community structure was highly variable between the study years, but was overall tightly correlated to water mass properties, with bottom temperature being the most significant factor influencing communities. Zooplankton biomass was dominated by the large copepod Calanus glacialis, while abundance was dominated by small shelf species of copepods, such as Pseudocalanus spp. and Oithona similis. The “cold" summers of 2009-2012 had nearly twice the biomass and abundance of zooplankton compared to the oceanographically “warm" summer of 2004. We discuss the implications of the inter-annual variability of planktonic communities within the Chukchi Sea, and the possible effects of longer-term climate change. We then look at distribution and population structure of an ecologically important species complex within the zooplankton, Pseudocalanus spp, and evaluate the implications of a warming climate for this group of copepods. While numerically dominating the communities, Pseudocalanus spp. has been historically understudied at the species level due to very subtle morphological differences between the species. Our approach used a combination of microscopic identification as well as a novel species-specific PCR identification method to discriminate between the four species found in the Chukchi Sea. Our results suggest that shifting oceanographic patterns and climate warming will have unequal impact on this group of organisms, arising from species-specific life histories and tolerance to environmental conditions. These recent observations on zooplankton are then placed into a historical context through comparison to data collected throughout the past half-century (1946-2012). Despite significant challenges associated with the highly variable spatial coverage and methodology of the available datasets, significant trends were detected. In addition to high levels of inter-annual variability, we demonstrate significant increases in zooplankton biomass and abundance in recent years compared to historical studies, as well as shifting distribution ranges for several key species. This signal was most pronounced within the copepods, particularly Calanus glacialis, which appears to be indirectly benefiting from warming of the region. While summer zooplankton communities of the Chukchi Sea have been primarily Bering-Pacific in character for as long as our records exist, continuing warming and ice loss are increasing the influence of Bering-Pacific fauna within the Chukchi region

Seasonal dynamics and life histories of three sympatric species of Pseudocalanus in two Svalbard fjords

Small copepods are the most diverse and numerous group in high-latitude zooplankton, yet our knowledge of important species remains poor because of the difficulties involved in correct species identification. In this study, we use a molecular method of identification, a species-specific polymerase chain reaction, to provide the first description of the seasonal dynamics and life histories of the important genus Pseudocalanus in two Svalbard fjords with contrasting environments. We conducted monthly investigations in the relatively warm and ice-free Adventfjorden, supplemented with seasonal samples from the colder, seasonally ice-covered Billefjorden. We found three species of Pseudocalanus (the Arctic P. acuspes and P. minutus, and the boreal P. moultoni). Pseudocalanus acuspes had a distinct annual life cycle and dominated during summer, when it actively reproduced. Surprisingly, the boreal P. moultoni was present year-round in both fjords and was the dominant species during winter; the presence of all life stages of this species throughout the year suggests a more continuous reproduction. The Arctic P. minutus was the rarest of the three species and was likely able to complete its life cycle in Billefjorden but not in Adventfjorden. Our study demonstrates that closely related species may have different life strategies and environmental preferences, which presumably make high-latitude zooplankton communities more resilient to climate change impacts on genus but not necessarily on species level

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean

In recent decades, the central Arctic Ocean has been experiencing dramatic decline in sea ice coverage, thickness and extent, which is expected to have a tremendous impact on all levels of Arctic marine life. Here, we analyze the regional and temporal changes in pan-Arctic distribution and population structure of the key zooplankton species Calanus glacialis and C. hyperboreus in relation to recent changes in ice conditions, based on historical (1993–1998) and recent (2007–2016) zooplankton collections and satellite-based sea ice observations. We found strong correlations between Calanus abundance/population structure and a number of sea ice parameters. These relationships were particularly strong for C. glacialis, with higher numbers being observed at locations with a lower ice concentration, a shorter distance to the ice edge, and more days of open water. Interestingly, early stages of C. hyperboreus followed the same trends, suggesting that these two species substantially overlap in their core distribution area in the Arctic Ocean. Calanus glacialis and C. hyperboreus have been historically classified as shelf versus basin species, yet we conclude that both species can inhabit a wide range of bottom depths and their distribution in the Arctic Ocean is largely shaped by sea ice dynamics. Our data suggest that the core distribution patterns of these key zooplankton are shifting northwards with retreating sea ice and changing climate conditions.publishedVersio

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean

publishedVersio

Daily transcriptomes of the copepod Calanus finmarchicus during the summer solstice at high Arctic latitudes

The zooplankter Calanus finmarchicus is a member of the so-called “Calanus Complex”, a group of copepods that constitutes a key element of the Arctic polar marine ecosystem, providing a crucial link between primary production and higher trophic levels. Climate change induces the shift of C. finmarchicus to higher latitudes with currently unknown impacts on its endogenous timing. Here we generated a daily transcriptome of C. finmarchicus at two high Arctic stations, during the more extreme time of Midnight Sun, the summer solstice. While the southern station (74.5 °N) was sea ice-free, the northern one (82.5 °N) was sea ice-covered. The mRNAs of the 42 samples have been sequenced with an average of 126 ± 5 million reads (mean ± SE) per sample, and aligned to the reference transcriptome. We detail the quality assessment of the datasets and the complete annotation procedure, providing the possibility to investigate daily gene expression of this ecologically important species at high Arctic latitudes, and to compare gene expression according to latitude and sea ice-coverage

Borealization of the Arctic Ocean in Response to Anomalous Advection From Sub-Arctic Seas

An important yet still not well documented aspect of recent changes in the Arctic Ocean is associated with the advection of anomalous sub-Arctic Atlantic- and Pacific-origin waters and biota into the polar basins, a process which we refer to as borealization. Using a 37-year archive of observations (1981-2017) we demonstrate dramatically contrasting regional responses to atlantification (that part of borealization related to progression of anomalies from the Atlantic sector of sub-Arctic seas into the Arctic Ocean) and pacification (the counterpart of atlantification associated with influx of anomalous Pacific waters). Particularly, we show strong salinification of the upper Eurasian Basin since 2000, with attendant reductions in stratification, and potentially altered nutrient fluxes and primary production. These changes are closely related to upstream conditions. In contrast, pacification is strongly manifested in the Amerasian Basin by the anomalous influx of Pacific waters, creating conditions favorable for increased heat and freshwater content in the Beaufort Gyre halocline and expansion of Pacific species into the Arctic interior. Here, changes in the upper (overlying) layers are driven by local Arctic atmospheric processes resulting in stronger wind/ice/ocean coupling, increased convergence within the Beaufort Gyre, a thickening of the fresh surface layer, and a deepening of the nutricline and deep chlorophyll maximum. Thus, a divergent (Eurasian Basin) gyre responds altogether differently than does a convergent (Amerasian Basin) gyre to climate forcing. Available geochemical data indicate a general decrease in nutrient concentrations Arctic-wide, except in the northern portions of the Makarov and Amundsen Basins and northern Chukchi Sea and Canada Basin. Thus, changes in the circulation pathways of specific water masses, as well as the utilization of nutrients in upstream regions, may control the availability of nutrients in the Arctic Ocean. Model-based evaluation of the trajectory of the Arctic climate system into the future suggests that Arctic borealization will continue under scenarios of global warming. Results from this synthesis further our understanding of the Arctic Ocean\u27s complex and sometimes non-intuitive Arctic response to climate forcing by identifying new feedbacks in the atmosphere-ice-ocean system in which borealization plays a key role

Ribosomal DNA as DAMPs Signal for MCF7 Cancer Cells

Introduction: The cell free ribosomal DNA (cf-rDNA) is accrued in the total pool of cell free DNA (cfDNA) in some non-cancer diseases and demonstrates DAMPs characteristics. The major research questions: (1) How does cell free rDNA content change in breast cancer; (2) What type of response in the MCF7 breast cancer cells is caused by cf-rDNA; and (3) What type of DNA sensors (TLR9 or AIM2) is stimulated in MCF7 in response to the action of cf-rDNA?Materials and Methods: CfDNA and gDNA were isolated from the blood plasma and the cells derived from 38 breast cancer patients and 20 healthy female controls. The rDNA content in DNA was determined using non-radioactive quantitative hybridization. In order to explore the rDNA influence on MCF7 breast cancer cells, the model constructs (GC-DNAs) were applied: pBR322-rDNA plasmid (rDNA inset 5836 bp long) and pBR322 vector. ROS generation, DNA damage, cell cycle, expression of TLR9, AIM2, NF-kB, STAT3, and RNA for 44 genes affecting the cancer cell viability were evaluated. The methods used: RT-qPCR, fluorescent microscopy, immunoassay, flow cytometry, and siRNA technology.Results: The ratio R = cf-rDNA/g-rDNA for the cases was higher than for the controls (median 3.4 vs. 0.8, p < 10−8). In MCF7, GC-DNAs induce a ROS burst, DNA damage response, and augmentation of NF-kB and STAT3 activity. The number of the apoptotic cells decreases, while the number of cells with an instable genome (G2/M– arrest, micronuclei) increase. Expression of anti-apoptotic genes (BCL2, BCL2A1, BCL2L1, BIRC3, MDM2) is elevated, while expression of pro-apoptotic genes (BAX, BID, BAD, PMAIP1, BBC3) is lowered. The cells response for pBR322-rDNA is much more intense and develops much faster, than response for pBR322, and is realized through activation of TLR9- MyD88 - NF-kB- signaling. This difference in response speed is owing to the heightened oxidability of pBR322-rDNA and better ability to penetrate the cell. Induction of TLR9 expression in MCF7 is followed by blocking AIM2 expression.Conclusion: (1) Ribosomal DNA accumulates in cfDNA of breast cancer patients; (2) Cell free rDNA induce DNA damage response and stimulates cells survival, including cells with an instable genome; (3) Cell free rDNA triggers TLR9- MyD88- NF-kB- signaling, with significantly repressing the expression of AIM2

Abundance of the life stages of three Calanus species and Metridia longa during Polarstern cruise ARK-XXVI/3 (PS78, TRANSARK)

Abundances of the life stages of the three Calanus species (Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus) and Metridia longa was calculated in the Arctic Ocean during Polarstern cruise ARK-XXVI/3. Samples were taken with the Multinet maxi (Hydrobios, Kiel), which is equipped with nine nets (mesh size: 150 µm)

Nasal Cerebrospinal Leaks in the Milieu of COVID-19 Pandemic

Background The unintentional ingestion of oropharyngeal or gastric contents into the respiratory tract is known as aspiration. Rhinorrhea can cause aspiration pneumonia (cerebrospinal fluid leakage)