Population trajectories for the Antarctic bivalve Laternula elliptica: identifying demographic bottlenecks in differing environmental futures

The world’s oceans are changing, and dramatic shifts have been documented in the Southern Ocean. The consequences of these shifts to coastal benthic organisms are difficult to predict at present, as ocean warming may increase primary production and food resources for benthic consumers, whilst OA may have negative impacts that differentially affect various species and life stages. A model was developed to investigate how different scenarios of change may influence population size of the Antarctic bivalve Laternula elliptica. The model describes potential implications of both pH and temperature change on survivorship and reproductive output of a population of this bivalve species in McMurdo Sound, Ross Sea. Implications of increases and decreases in mortality rate across different life stages of the population (early, mid and late) were assessed. Additionally, effects on energetic resource partitioning and dictating reproductive potential (RP) were also investigated. Significant declines in RP, due to increased basal metabolic demand, were associated with even relatively small changes in temperature and pH, resulting in populations declining to 25 % of the starting equilibrium density within 60 years. As L. elliptica is a pivotal species to the functionality of the Antarctic coastal benthic ecosystem, wide spread repercussions are expected if populations are impacted as the model predicts. Although further model development is required to explore the ecosystem implications of the population decline described in this paper, this work allows a better understanding of the consequences of change as soon as data on the direction and magnitude of the changes affecting Antarctic seas become available.     

KCNMA1 Encoded Cardiac BK Channels Afford Protection against Ischemia-Reperfusion Injury

Mitochondrial potassium channels have been implicated in myocardial protection mediated through pre-/postconditioning. Compounds that open the Ca²⁺- and voltage-activated potassium channel of big-conductance (BK) have a pre-conditioning-like effect on survival of cardiomyocytes after ischemia/reperfusion injury. Recently, mitochondrial BK channels (mitoBKs) in cardiomyocytes were implicated as infarct-limiting factors that derive directly from the KCNMA1 gene encoding for canonical BKs usually present at the plasma membrane of cells. However, some studies challenged these cardio-protective roles of mitoBKs. Herein, we present electrophysiological evidence for paxilline- and NS11021-sensitive BK-mediated currents of 190 pS conductance in mitoplasts from wild-type but not BK^−/− cardiomyocytes. Transmission electron microscopy of BK^−/− ventricular muscles fibres showed normal ultra-structures and matrix dimension, but oxidative phosphorylation capacities at normoxia and upon re-oxygenation after anoxia were significantly attenuated in BK^−/− permeabilized cardiomyocytes. In the absence of BK, post-anoxic reactive oxygen species (ROS) production from cardiomyocyte mitochondria was elevated indicating that mitoBK fine-tune the oxidative state at hypoxia and re-oxygenation. Because ROS and the capacity of the myocardium for oxidative metabolism are important determinants of cellular survival, we tested BK^−/− hearts for their response in an ex-vivo model of ischemia/reperfusion (I/R) injury. Infarct areas, coronary flow and heart rates were not different between wild-type and BK^−/− hearts upon I/R injury in the absence of ischemic pre-conditioning (IP), but differed upon IP. While the area of infarction comprised 28±3% of the area at risk in wild-type, it was increased to 58±5% in BK^−/− hearts suggesting that BK mediates the beneficial effects of IP. These findings suggest that cardiac BK channels are important for proper oxidative energy supply of cardiomyocytes at normoxia and upon re-oxygenation after prolonged anoxia and that IP might indeed favor survival of the myocardium upon I/R injury in a BK-dependent mode stemming from both mitochondrial post-anoxic ROS modulation and non-mitochondrial localizations.     

Increased proton leak and SOD2 expression in myotubes from obese non-diabetic subjects with a family history of type 2 diabetes

Muscle insulin resistance is linked to oxidative stress and decreased mitochondrial function. However, the exact cause of muscle insulin resistance is still unknown. Since offspring of patients with type 2 diabetes mellitus (T2DM) are susceptible to developing insulin resistance, they are ideal for studying the early development of insulin resistance. By using primary muscle cells derived from obese non-diabetic subjects with (FH +) or without (FH ?) a family history of T2DM, we aimed to better understand the link between mitochondrial function, oxidative stress, and muscle insulin resistance. Insulin-stimulated glucose uptake and glycogen synthesis were normal in FH + myotubes. Resting oxygen consumption rate was not different between groups. However, proton leak was higher in FH + myotubes. This was associated with lower ATP content and decreased mitochondrial membrane potential in FH + myotubes. Surprisingly, mtDNA content was higher in FH + myotubes. Oxidative stress level was not different between FH + and FH ? groups. Reactive oxygen species content was lower in FH + myotubes when differentiated in high glucose/insulin (25 mM/150 pM), which could be due to higher oxidative stress defenses (SOD2 expression and uncoupled respiration). The increased antioxidant defenses and mtDNA content in FH + myotubes suggest the existence of compensatory mechanisms, which may provisionally prevent the development of insulin resistance.     

Rapid reworking of subtidal sediments by burrowing spatangoid urchins

The mixing and displacement of sediment by benthic macrofauna (bioturbation) has major biogeochemical implications, and can control rates of organic matter degradation and carbon burial. Large, abundant, mobile macrofauna often dominate sediment bioturbation, and heart urchins of the genus Echinocardium are regarded as key sediment bioturbators in marine systems throughout the world. To better understand the bioturbation potential and functional role of Echinocardium, we developed a mathematical model and parameterized it with field data from six locations in northern New Zealand in order to estimate bioturbation rates in these places. Although urchin sizes and densities were measured in consecutive years at all six locations, we obtained a third model parameter, urchin movement rate, from one time and place only (Site OB5). Because confidence in model output was greatest at OB5, and since OB5 had the highest sediment reworking rate of all sites, our model yielded a good upper bound estimate for the bioturbation potential of Echinocardium in the areas examined. The volume of sediment displaced by Echinocardium populations reached 20,000 cm³ m⁻² d⁻¹ at OB5, suggesting that surface sediment is reworked about every 3 days at sites where Echinocardium is abundant. Experimental work with a fluorescent tracer at OB5 suggested limited downward particle movement as a result of Echinocardium bioturbation, though vertical profiles of chlorophyll a and organic matter content indicated well mixed sediment. The loss of Echinocardium because of broad-scale anthropogenic disturbance to the seabed could have major consequences on marine ecosystem functioning.     

CD8 suppressor cell activity and its effect on CD4 helper cell-dependent growth of SJL/J B-cell lymphomas

CD8 cells, flow cytometrically sorted from the lymph nodes of tumor-bearing and normal SJL/J mice, suppressed in vitro proliferation of syngeneic CD4 cells in response to concanavalin A, two independent SJL/J lymphomas, and LPS-activated syngeneic B-cell blasts. The data confirm earlier reports that nonspecific suppressor cells are generated as a consequence of SJL/J lymphoma-stimulated T-cell proliferation. Earlier reports are extended, in that the suppressor cell is identified as expressing CD8, and the suppressor activity is shown to decrease the tumor-stimulated CD4 cell proliferation which is essential to growth of these CD4-dependent murine B-cell lymphomas. In three separate experiments, anti-CD8 treatment of mice, in which CD4 cells were made limiting by injection with anti-CD4, increased growth of transplantable SJL/J lymphomas with corresponding increases in numbers of CD4 cells. The data imply that, under certain conditions, CD8 suppressor cells measurably influence growth of SJL/J lymphomas by regulating the tumor-stimulated CD4 cell proliferation essential to maximum growth of SJL/J lymphomas.     

Initial Results from the Survey of Organizational Research Climates (SOuRCe) in the U.S. Department of Veterans Affairs Healthcare System

Background

In service to its core mission of improving the health and well-being of veterans, Veterans Affairs (VA) leadership is committed to supporting research best practices in the VA. Recognizing that the behavior of researchers is influenced by the organizational climates in which they work, efforts to assess the integrity of research climates and share such information with research leadership in VA may be one way to support research best practices. The Survey of Organizational Research Climate (SOuRCe) is the first validated survey instrument specifically designed to assess the organizational climate of research integrity in academic research organizations. The current study reports on an initiative to use the SOuRCe in VA facilities to characterize the organizational research climates and pilot test the effectiveness of using SOuRCe data as a reporting and feedback intervention tool.

Methods

We administered the SOuRCe using a cross-sectional, online survey, with mailed follow-up to non-responders, of research-engaged employees in the research services of a random selection of 42 VA facilities (e.g., Hospitals/Stations) believed to employ 20 or more research staff. We attained a 51% participation rate, yielding more than 5,200 usable surveys.

Results

We found a general consistency in organizational research climates across a variety of sub-groups in this random sample of research services in the VA. We also observed similar SOuRCe scale score means, relative rankings of these scales and their internal reliability, in this VA-based sample as we have previously documented in more traditional academic research settings. Results also showed more substantial variability in research climate scores within than between facilities in the VA research service as reflected in meaningful subgroup differences. These findings suggest that the SOuRCe is suitable as an instrument for assessing the research integrity climates in VA and that the tool has similar patterns of results that have been observed in more traditional academic research settings.

Conclusions

The local and specific nature of organizational climates in VA research services, as reflected in variability across sub-groups within individual facilities, has important policy implications. Global, “one-size-fits-all” type initiatives are not likely to yield as much benefit as efforts targeted to specific organizational units or sub-groups and tailored to the specific strengths and weaknesses documented in those locations.     

Spatial patterns in soft-bottom communities

The spatial patterns exhibited by soft-bottom macrobenthic organismshave become recognized for their potential to play an importantrole in determining both the ecology of these species and our ability to study it. Recent studies have shown that spatial scales of field sampling or experimentation are important influences on data interpretation. The presence of patches, density gradients and spatially autocorrelated variables may confound designs and affect the validity of inferential statistics. Future studies must integrate the intensity and form of patterns from various spatial and temporal scales if we are to understand the process responsible for generating pattern.     

Beyond the single index: Investigating ecological mechanisms underpinning ecosystem multifunctionality with network analysis

Ecosystems simultaneously deliver multiple functions that relate to both the activities of resident species and environmental conditions. One of the biggest challenges in multifunctionality assessment is balancing analytical simplicity with ecosystem complexity. As an alternative to index‐based approaches, we introduce a multivariate network analysis that uses network theory to assess multifunctionality in terms of the relationships between species'' functional traits, environmental characteristics, and functions. We tested our approach in a complex and heterogeneous ecosystem, marine intertidal sandflats. We considered eight ecosystem function, five macrofaunal functional trait groups derived from 36 species, and four environmental characteristics. The indicators of ecosystem functions included the standing stock of primary producers, oxygen production, benthic oxygen consumption, DIN (ammonium and NOx efflux) and phosphate release from the sediments, denitrification, and organic matter degradation at the sediment surface. Trait clusters included functional groups of species that shared combinations of biological traits that affect ecosystem function: small mobile top 2 cm dwellers, suspension feeders, deep‐dwelling worms, hard‐bodied surface dwellers, and tube‐forming worms. Environmental characteristics included sediment organic matter, %mud, %shell hash, and %sediment water content. Our results visualize and quantify how multiple ecosystem elements are connected and contribute to the provision of functions. Small mobile top 2 cm dwellers (among trait clusters) and %mud (among environmental characteristics) were the best predictor for multiple functions. Detailed knowledge of multifunctionality relationships can significantly increase our understanding of the real‐world complexity of natural ecosystems. Multivariate network analysis, as a standalone method or applied alongside already existing single index multifunctionality methods, provides means to advance our understanding of how environmental change and biodiversity loss can influence ecosystem performance across multiple dimensions of functionality. Embedding such a detailed yet holistic multifunctionality assessment in environmental decision‐making will support the assessment of multiple ecosystem services and social‐ecological values.     

Biological traits approaches in benthic marine ecology: Dead ends and new paths

Biological traits analysis (BTA) links community structure to both ecological functions and response to environmental drivers through species’ attributes. In consequence, it has become a popular approach in marine benthic studies. However, BTA will reach a dead end if the scientific community does not acknowledge its current shortcomings and limitations: (a) uncertainties related to data origins and a lack of standardized reporting of trait information; (b) knowledge gaps on the role of multiple interacting traits on driving the organisms’ responses to environmental variability; (c) knowledge gaps regarding the mechanistic links between traits and functions; (d) a weak focus on the spatial and temporal variability that is inherent to the trait expression of species; and, last but not least, (e) the large reliance on expert knowledge due to an enormous knowledge gap on the basic ecology of many benthic species. BTA will only reach its full potential if the scientific community is able to standardize and unify the reporting and storage of traits data and reconsider the importance of baseline observational and experimental studies to fill knowledge gaps on the mechanistic links between biological traits, functions, and environmental variability. This challenge could be assisted by embracing new technological advances in marine monitoring, such as underwater camera technology and artificial intelligence, and making use of advanced statistical approaches that consider the interactive nature and spatio‐temporal variability of biological systems. The scientific community has to abandon some dead ends and explore new paths that will improve our understanding of individual species, traits, and the functioning of benthic ecosystems.