Assessing reproductive and endocrine parameters in male largescale suckers (\u3ci\u3eCatostomus macrocheilus\u3c/i\u3e) along a contaminant gradient in the lower Columbia River, USA

Persistent organochlorine pollutants such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p′-DDE), and polybrominated diphenyl ethers (PBDEs) are stable, bioaccumulative, and widely found in the environment, wildlife, and the human population. To explore the hypothesis that reproduction in male fish is associated with environmental exposures in the lower Columbia River (LCR), reproductive and endocrine parameters were studied inmale resident, non-anadromous largescale sucker (Catostomus macrocheilus) (LSS) inthe samehabitats as anadromous salmonids having conservation status. Testes, thyroid tissue and plasma collected in 2010 from Longview (LV), Columbia City (CC), and Skamania (SK; reference)were studied. Sperm morphologies and thyrocyte heights were measured by light microscopy, sperm motilities by computer-assisted sperm motion analysis, sperm adenosine triphosphate (ATP) with luciferase, and plasma vitellogenin (VTG), thyroxine (T4), and triiodothyronine (T3) by immunoassay. Sperm apoptosis, viability, mitochondrial membrane potential, nuclear DNA fragmentation, and reproductive stage were measured by flow cytometry. Sperm quality parameters (except counts) and VTG were significantly different among sites, with correlations between VTG and 7 spermparameters. Thyrocyte heights, T4, T3, gonadosomatic index and Fulton\u27s condition factor differed among sites, but not significantly. Sperm quality was significantly lower and VTG higherwhere liver contaminants and water estrogen equivalents were highest (LV site). Total PCBs (specifically PCB-138, -146, -151, -170, -174, -177, -180, -183, -187, -194, and -206) and total PBDEs (specifically BDE-47, -100, -153, and -154) were negatively correlated with sperm motility. PCB-206 and BDE-154 were positively correlated with DNA fragmentation, and pentachloroanisole and VTG were positively correlated with sperm apoptosis and negatively correlated with ATP. BDE-99 was positively correlated with sperm counts and motility; T4 was negatively correlated with counts and positively correlated with motility, thus indicating possible androgenic mechanisms and thyroid endocrine disruption. Male LSS proved to be an informativemodel for studying reproductive and endocrine biomarkers in the LCR

Towards integrated assessment of the Ganges-Brahmaputra delta

Understanding the future evolution of the Ganges-Brahmaputra delta is fundamental to planning and management of this heavily-populated low-lying delta plain. Through the Holocene it was shaped by the interacting effects of sediment supply, sea level and marine reworking. Unlike traditional models, tectonics and climate have also played important roles in the delta’s evolution. Superimposed upon the active, but relatively unknown, natural system, human alterations to natural processes have become increasingly important, both (1) indirectly by changing land use and water management within the catchment, and (2) directly within the delta itself due to groundwater withdrawal, flood mitigation efforts, infrastructure development, etc. This human influence will intensify in the future as coastal and catchment populations grow, urbanise and develop their economies. Hence, the Ganges-Brahmaputra delta, like all deltas, is evolving in response to multiple drivers of change. To analyse future changes for management and planning purposes, this paper argues that an integrated assessment framework of the entire delta plain is required. This would take account of the interacting natural and human drivers of change within the delta plain, as well as the external drivers, such as global-mean sea-level rise. Hence it would emphasise the multiple factors and stresses that are influencing the delta evolution. Such a framework also allows the full range of management responses to be considered. In addition to traditional engineering approaches in deltas, there are opportunities to work with nature. The deltaic system has the capacity to be highly resilient in the face of these multiple pressures with important ecological and social benefits. This resilience is largely due to the delivery of sediment to the delta from the catchment.A challenge for future management is to understand and use this capacity to the maximum, including consideration of possible catchment changes such as dam construction. A similar approach could be developed for the management and planning of the other big and small delta systems in Asia

Landscape variability and the response of Asian megadeltas to environmental change

Deltas, occurring at the mouths of river systems that deposit sediments as they enter the sea, are some of the most dynamic sedimentary environments. They contain a long, and often economically significant, sedimentary record of their response to past episodes of climate and sea-level change. Geological investigation of these deposits, and the processes controlling sedimentation, provide insights into the response of deltas to environmental change, which in turn may offer rational and cost-effective strategies for the sustainable management of natural resources and land use in these dynamic systems in the face of future environmental change

Assessing reproductive and endocrine parameters in male largescale suckers (Catostomus macrocheilus) along a contaminant gradient in the lower Columbia River, USA

Persistent organochlorine pollutants such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p'-DDE), and polybrominated diphenyl ethers (PBDEs) are stable, bioaccumulative, and widely found in the environment, wildlife, and the human population. To explore the hypothesis that reproduction in male fish is associated with environmental exposures in the lower Columbia River (LCR), reproductive and endocrine parameters were studied in male resident, non-anadromous largescale sucker (Catostomus macrocheilus) (LSS) in the same habitats as anadromous salmonids having conservation status. Testes, thyroid tissue and plasma collected in 2010 from Longview (LV), Columbia City (CC), and Skamania (SK; reference) were studied. Sperm morphologies and thyrocyte heights were measured by light microscopy, sperm motilities by computer-assisted sperm motion analysis, sperm adenosine triphosphate (ATP) with luciferase, and plasma vitellogenin (VTG), thyroxine (T4), and triiodothyronine (T3) by immunoassay. Sperm apoptosis, viability, mitochondrial membrane potential, nuclear DNA fragmentation, and reproductive stage were measured by flow cytometry. Sperm quality parameters (except counts) and VTG were significantly different among sites, with correlations between VTG and 7 sperm parameters. Thyrocyte heights, T4, T3, gonadosomatic index and Fulton's condition factor differed among sites, but not significantly. Sperm quality was significantly lower and VTG higher where liver contaminants and water estrogen equivalents were highest (LV site). Total PCBs (specifically PCB-138, -146, -151, -170, -174, -177, -180, -183, -187, -194, and -206) and total PBDEs (specifically BDE-47, -100, -153, and -154) were negatively correlated with sperm motility. PCB-206 and BDE-154 were positively correlated with DNA fragmentation, and pentachloroanisole and VTG were positively correlated with sperm apoptosis and negatively correlated with ATP. BDE-99 was positively correlated with sperm counts and motility; T4 was negatively correlated with counts and positively correlated with motility, thus indicating possible androgenic mechanisms and thyroid endocrine disruption. Male LSS proved to be an informative model for studying reproductive and endocrine biomarkers in the LCR

Impact of glacial-lake paleofloods on valley development since glacial termination II: A conundrum of hydrology and scale for the lowstand Brahmaputra-Jamuna paleovalley system

To better define the base of the Brahmaputra River paleovalley, we analyzed an extensive borehole data set from the subaerial Bengal delta and a 255-km-long multichannel seismic survey along the modern river. The data reveal that the paleovalley floor is defined by a gravel unit containing boulder-sized clasts up to 30 cm in diameter, deposited after ca. 30 ka but before ca. 9 ka. Paleohydrology during that time and the previous glacial maximum was characterized by a weak monsoon and reduced river discharge, both of which are inconsistent with large valley formation. However, our work indicates that glacial-lake outburst floods sourced from the Tibetan reaches of the Brahmaputra were routed through the lowstand valley, producing megaflood-scale discharge capable of transporting gravel and cannibalizing the valley margins. The timing of these glacial-lake outburst flood–driven discharge events was coincident with valley development and explains the anomalously large width of the valley and basal gravel surface. Despite the underfit scale of Brahmaputra discharge following the last glacial period, a strengthening monsoon and high sediment discharge in the early Holocene subsequently contributed to the efficient infilling of the massive paleovalley by the mid-Holocene. In a sequence stratigraphic context, this work provides an example of a major unconformity that developed late in the eustatic cycle (i.e., during early transgression rather than an earlier, protracted response to sea-level lowering) and in response to a perturbation originating in the catchment instead of changing accommodation in the basin. As such, it represents a geologically instantaneous time surface that can be used as a marker for stratigraphic correlation but one that is not in phase with eustatic sea-level fall