Climate and juvenile recruitment as drivers of Arctic cod (Boreogadus saida) dynamics in two Canadian Arctic seas

Arctic cod (Boreogadus saida) is the most abundant forage fish species in Arctic seas and plays a pivotal role in the transfer of energy between zooplankton and top predators. The dominance of Arctic cod and the Arctic’s relatively low biodiversity interact such that changing population dynamics of Arctic cod have cascading effects on whole Arctic marine ecosystems. Over the last decades, warming in the Arctic has led to a decline in Arctic cod populations in the Barents Sea, but in the Canadian Arctic these conditions have been correlated with up to a 10-fold higher biomass of age-0 Arctic cod at the end of summer. However, whether this enhanced larval survival with warmer waters endures through age-1þ populations is unknown. A better understanding of spatial variation in the response of Arctic cod populations to environmental conditions is critical to forecast future changes in Arctic ecosystems. Here, we rely on a 17-year time series of acoustic-trawl surveys (2003–2019) to test whether ice-breakup date, sea surface temperature, zooplankton density, and Arctic climate indices during early life stages affect the subsequent recruitment of age-1þ Arctic cod in the Beaufort Sea and Baffin Bay. In the Beaufort Sea, the biomass of age-1þ Arctic cod correlated with both Arctic Oscillation indices and age-0 biomass of the previous year. In Baffin Bay, the biomass of age-1þ Arctic cod correlated with previous-year North Atlantic Oscillation indices and the timing of ice breakup. This study demonstrates that climate and environmental conditions experienced during the early life stages drive the recruitment of the age-1þ Arctic cod population and helps to quantify spatial variation in the main environmental drivers

Spitzer, Near-Infrared, and Submillimeter Imaging of the Relatively Sparse Young Cluster, Lynds 988e

We present {\it Spitzer} images of the relatively sparse, low luminosity young cluster L988e, as well as complementary near-infrared (NIR) and submillimeter images of the region. The cluster is asymmetric, with the western region of the cluster embedded within the molecular cloud, and the slightly less dense eastern region to the east of, and on the edge of, the molecular cloud. With these data, as well as with extant H$\alpha$ data of stars primarily found in the eastern region of the cluster, and a molecular $^{13}$CO gas emission map of the entire region, we investigate the distribution of forming young stars with respect to the cloud material, concentrating particularly on the differences and similarities between the exposed and embedded regions of the cluster. We also compare star formation in this region to that in denser, more luminous and more massive clusters already investigated in our comprehensive multi-wavelength study of young clusters within 1 kpc of the Sun.Comment: 21 pages, 6 tables, 13 figures. Full resolution figures at: http://astro.pas.rochester.edu/~tom/Preprints/L988e.pd

A food web model for the Baffin Bay coastal and shelf ecosystem. Part 1 : Ecopath Technical Report

This work was undertaken as part of a multidisciplinary research project funded by the Marine Observation Prediction and Assessment Network - MEOPAR (at ULaval), Canadian Institute of Health Research – CIHR (at University of Ottawa), and Sentinel North (at ULaval), and hosted at Université Laval, in Canada. The objective of the overall project is to support the food security (i.e., the availability and access to sufficient, safe, nutritious food that meets dietary preference) of Inuit communities of the Eastern Canadian Arctic, as well as to explore ways to adapt to effects of climate change. Inuit fish and hunt local marine species, from invertebrates to fish and marine mammals, which make a large part of their diet and are central to their food security. With temperatures increasing twice as fast as the global average and sea ice becoming thinner and forming later, climate change effects on the distribution and abundance of Arctic marine species are already taking place. To better understand the effects of climate change in important subsistence species, a multi-species model (Ecopath with Ecosim) will be used to inform the development of an integrated ecosystem assessment. The model will be used as a tool to co-create scenarios of ecosystem change with the community of Qikiqtarjuaq, Nunavut, to inform adaptation strategies regarding food security (e.g., potential of new fisheries in the region). This report describes the development of an Ecopath model of the Baffin Bay coastal and shelf ecosystem. The methodology, data used to construct the model, data gaps and limitations are described

The circumpolar impacts of climate change and anthropogenic stressors on Arctic cod (Boreogadus saida) and its ecosystem

Arctic cod biomass are predicted. In most Arctic seas, the relative abundance of Arctic cod within the fish community will likely fluctuate in accordance with cold and warm periods. A reduced abundance of Arctic cod will negatively affect the abundance, distribution, and physiological condition of certain predators, whereas some predators will successfully adapt to a more boreal diet. Regional management measures that recognize thecritical roleof Arcticcod arerequiredtoensure that increased anthropogenic activities do not exacerbate the impacts of climate change on Arctic marine ecosystems. Ultimately, the mitigation of habitat loss for Arctic cod will only be achieved through a global reduction in carbon emissions

Effects of Annual Droughts on Fish Communities in Mississippi Sound Estuaries

© 2018, Coastal and Estuarine Research Federation. The Mississippi coastal region has two major rivers and four smaller rivers influencing the estuaries that make up the Mississippi Sound. The islands off Mississippi create a barrier which allows the area to be a widespread, productive estuarine region. With such a dependence on discharge from the drainages, it is important to understand the effect of salinity regimes on fish communities. Drought conditions in other regions have been shown to dramatically change the fish community structure. We used the long running Interjurisdictional Fisheries Program database (2006–2014) within Mississippi state waters and compared yearly fish communities between drought and non-drought years. Non-metric Multidimensional Scaling (nMDS), Analysis of Similarity (ANOSIM), and Indicator Species Analysis (ISA) were used to compare drought and non-drought conditions in the Mississippi Sound. During 2006 and 2007, which were identified as drought years by the Palmer Drought Severity Index (PDSI), differences in fish community structure were identified and compared to non-drought years (2008–2009 and 2011–2014). The ISA identified a total of eight species that were significantly influenced by drought years. Of the eight species, the abundance of seven species significantly decreased while the abundance of one species significantly increased. With an increasing human population in central and south Mississippi, pressure on freshwater resources is likely to increase, resulting in possible changes in the fish community dynamics of the Mississippi Sound. Understanding the influence of decreased river discharges will assist managers in determining the impacts of freshwater withdrawals during base flow periods

Structure and function of the western Baffin Bay coastal and shelf ecosystem

Arctic marine species, from benthos to fish and mammals, are essential for food security and sovereignty of Inuit people. Inuit food security is dependent on the availability, accessibility, quality, and sustainability of country food resources. However, climate change effects are threatening Inuit food systems through changes in abundance and nutritional quality of locally harvested species, while foundational knowledge of Arctic food webs remains elusive. Here, we summarized scientific knowledge available for the western Baffin Bay coastal and shelf ecosystem by building a food web model using the Ecopath with Ecosim modeling framework. Based on this model, we calculated ecological network analysis indices to describe structure and function of the system. We used Linear Inverse Modeling and Monte Carlo analysis to assess parameter uncertainty, generating plausible parameterizations of this ecosystem from which a probability density distribution for each index was generated. Our findings suggest that the system is controlled by intermediate trophic levels, highlighting the key role of Arctic cod (Boreogadus saida) as prey fish, as well as the importance of other less studied groups like cephalopods in controlling energy flows. Most of the ecosystem biomass is retained in the system, with very little lost to subsistence harvest and commercial fisheries, indicating that these activities were within a sustainable range during the modeling period. Our model also highlights the scientific knowledge gaps that still exist (e.g., species abundances), including valued harvest species like Arctic char (Salvelinus alpinus), walrus (Odobenus rosmarus), and seals, and importantly our poor understanding of the system in winter. Moving forward, we will collaborate with Inuit partners in Qikiqtarjuaq, NU, Canada, to improve this modeling tool by including Inuit knowledge. This tool thus serves as a starting point for collaborative discussions with Inuit partners and how its use can better inform local and regional decision-making regarding food security

Mechanism of the Internal Ribosome Entry Site-mediated Translation of Serine Hydroxymethyltransferase 1*

The 5′-untranslated region (UTR) of serine hydroxymethyltransferase 1 (SHMT1) contains an internal ribosome entry site (IRES) that regulates SHMT1 expression, a rate-limiting enzyme in de novo thymidylate biosynthesis. In this study, we show that the SHMT1 IRES is the first example of a cellular IRES that is poly(A) tail-independent. Interactions between the 5′-UTR and 3′-UTR functionally replaced interactions between the poly(A) tail and the poly(A)-binding protein (PABP) to achieve maximal IRES-mediated translational efficiency. Depletion of the SHMT1 IRES-specific trans-acting factor (ITAF) CUG-binding protein 1 (CUGBP1) from in vitro translation extracts or deletion of the CUGBP1 binding site on the 3′-UTR of the SHMT1 transcript decreased the IRES activity of non-polyadenylylated biscistronic mRNAs relative to polyadenylylated biscistronic mRNAs and resulted in a requirement for PABP. We also identified a novel ITAF, heterogeneous nuclear ribonucleoprotein H2 (hnRNP H2), that stimulates SHMT1 IRES activity by binding to the 5′-UTR of the transcript and interacting with CUGBP1. Collectively, these data support a model for the IRES-mediated translation of SHMT1 whereby the circularization of the mRNA typically provided by the eukaryotic initiation factor (eIF) 4G/PABP/poly(A) tail interaction is achieved instead through the hnRNP H2/CUGBP1-mediated interaction of the 5′- and 3′-UTRs of the SHMT1 transcript. This circularization enhances the IRES activity of SHMT1 by facilitating the recruitment and/or recycling of ribosomal subunits, which bind to the transcript in the middle of the 5′-UTR and migrate to the initiation codon via eIF4A-mediated scanning