Managing Groundwater to Ensure Ecosystem Function     

Laurel Saito  Bill Christian  Jennifer Diffley  Holly Richter  Melissa M. Rohde  Scott A. Morrison 《Ground water》2021,59(3):322-333

Groundwater is a critical resource not only for human communities but also for many terrestrial, riparian, and aquatic ecosystems and species. Yet groundwater planning and management decisions frequently ignore or inadequately address the needs of these natural systems. As a consequence, ecosystems dependent on groundwater have been threatened, degraded, or eliminated, especially in arid regions. There is growing acknowledgment that governmental protections for these ecological resources are necessary, but current legal, regulatory and voluntary provisions are often inadequate. Groundwater management premised on “safe yield,” which aims to balance human withdrawals with natural recharge rates, typically provides little to no consideration for water needed by ecosystems. Alternatively, the “sustainable yield” concept aims to integrate social, economic and environmental needs for groundwater, but the complexity of groundwater systems creates substantial uncertainty about the impact that current or future groundwater withdrawals will have on ecosystems. Regardless of the legal or regulatory framework, guidance is needed to help ensure environmental water needs will be met, especially in the face of pressure to increase human uses of groundwater resources. In this paper, we describe minimum provisions for planning, managing, and monitoring groundwater that collectively can lower the risk of harm to groundwater-dependent ecosystems and species, with a special emphasis on arid systems, where ecosystems and species may be especially reliant upon and sensitive to groundwater dynamics.  相似文献   

Responses of B-esterase enzymes in oysters (Crassostrea gigas) transplanted to pesticide contaminated bays form the Ebro Delta (NE,Spain)     

Victoria Ochoa  Carmen Riva  Melissa Faria  Carlos Barata 《Marine pollution bulletin》2013,66(1-2):135-142

Marine bivalves such as oysters are widely used as bioindicators to monitor marine coastal pollution. This study aimed to use B-esterase activity responses in oysters (Crassostrea gigas) cultured in Ebro Delta bays to monitor environmental effects of pesticides. The B esterases investigated were acetylcholinesterase, propionylcholinesterase, and carboxylesterase and their activities were measured in adductor muscle and gills from oysters transplanted in Ebro Delta bays where the are traditionally grown. Enzyme activities were related with physico-chemical parameters and pesticide levels measured in water. Cholinesterase activities measured in gills were unaffected across sites and periods. Conversely, carboxylesterase activities in oyster gills varied across periods and sites and were negatively correlated with residue levels of organophoshporous and carbamate pesticides in water. Therefore, inhibition of carboxylesterase activities can be considered a good indicator of exposure to anti-cholinergic pesticides in oysters.  相似文献   

Professional women and the economic practices of success and survival before and after regime change: diverse economies and restructuring in the Russian Republic of Buryatia     

Melissa Chakars  Elizabeth L. Sweet 《GeoJournal》2014,79(5):649-663

Drawing from historical research, participant observation, and informal and formal interviews, we examine the economic experiences of professional Buryat and Russian women before and after the collapse of the Soviet Union in the Siberian Russian Republic of Buryatia. We use a diverse economies framework to theorize a broader understanding of the restructured economy and how women have sought to improve and maintain their lives by developing various practices in the workforce in both the Soviet and post-Soviet periods such as gaining more education, informal networks of exchanges and favors, urbanization, and, for Buryats, Russian language acquisition. We argue that women in the early 2000s continue to employ many of these practices regardless of their varying experiences and attitudes about the transition from socialism to a market economy.  相似文献   

Nutrient Loading and Transformations in the Columbia River Estuary Determined by High-Resolution In Situ Sensors     

Melissa Gilbert  Joseph Needoba  Corey Koch  Andrew Barnard  Antonio Baptista 《Estuaries and Coasts》2013,36(4):708-727

The Columbia River estuary is characterized by relatively large tidal currents and water residence times of a few days or less. These and other environmental conditions tend to suppress water column productivity and favor the export of riverborne nutrients to the coastal ocean. However, hotspots of biological activity may allow for significant nutrient transformation and removal within the estuary, but these processes have previously been difficult to quantify due to the challenges of obtaining measurements at appropriate frequency and duration. In this study, nutrient biogeochemical dynamics within the salt-influenced region of the estuary were quantified using high-resolution in situ observations of nutrients and physical water properties. During 2010, three autonomous nutrient sensors (Satlantic SUNA, SubChem Systems Inc. APNA, WET Labs Cycle-PO4) that together measured nitrate?+?nitrite, orthophosphate, ammonium, silicic acid, and nitrite were deployed on fixed observatory platforms. Hourly measurements captured tidal fluctuations and permitted an analysis of river and ocean end-member mixing. The results suggested that during summer, the lower estuary released high concentrations of ammonium and phosphate despite low concentrations in the river and coastal ocean. This was likely a result of organic matter accumulation and remineralization in the estuarine turbidity maximum and the lateral bays adjacent to the main channel.  相似文献   

Expansion of the northern hemisphere subtropical high pressure belt: trends and linkages to precipitation and drought     

Bohumil M. Svoma  Daniel S. Krahenbuhl  Chad E. Bush  Jonny W. Malloy  Joshua R. White  Melissa A. Wagner 《自然地理学》2013,34(3):174-187

A critical issue in research concerning long-term climate change is the relationship between circulation features and global temperature variations. We establish that the annual areal size of the northern hemisphere subtropical high pressure belt (SHPB), as defined by seven 500-hPa height isohypses, shares over 70% of the variability with global annual near-surface air temperature since 1948. The area enclosed by the 5850-m isohypse of the 500-hPa surface in the northern hemisphere has more than doubled since the 1950s, with greatest increases over northern Africa, the Middle East and India. A long-term historical run of a coupled global climate model shows rapidly increasing SHPB annual sizes, since the mid-1970s. Since the SHPB’s descending air produces increased aridity, SHPB expansion may transition humid regions to more arid lands. To examine this aspect, first, variations in recorded precipitation using a gridded database for the region experiencing expansion of the SHPB show a decrease in precipitation (though significant only at the 88% confidence level) over the last 60?years. Second, variations in a 0.5° spatial resolution monthly drought index, the Standardized Precipitation Evapotranspiration Index, are highly correlated (+0.78) with annual variations in the area enclosed by the 500-hPa height isohypses. These results support those of previous investigations that suggest further northward expansion of the northern hemisphere subtropical dry zones with continued global climate change.  相似文献   

Variability in trap catches for an American lobster,Homarus americanus,spring fishery     

Michel Comeau  Melissa D. Smith  Manon Mallet 《新西兰海洋与淡水研究杂志》2013,47(1):401-410

At‐sea sampling is a common approach used by fisheries scientists to assess changes in fished populations. Traditional sampling programmes focus on short intensive sampling periods by fisheries personnel, although there has been a move to increase temporal sampling frequency within a fishing season by using harvesters. To determine the suitability of these two options, we compared the precision of estimates obtained for the American lobster (Homarus americanus) fishery in the southern Gulf of St. Lawrence, Canada. The sampling variance estimation for the mean catch‐per‐unit‐effort (CPUE) was based on a three‐stage sampling design with days as the primary unit, and buoy and trap as secondary and third stage units, respectively. Using the estimated variance components to predict and compare the variance of the mean CPUE for different at‐sea sampling designs, we show that it would be more efficient to sample a few traps (at least 3) every day for the entire fishing season than the traditional at‐sea sampling of the entire fishing gear twice or three times in a season by scientific personnel. Designing a harvester‐based at‐sea sampling programme could be an efficient approach for reducing costs while gathering essential fishery data, improving dialogue between the industry and scientists, and increasing harvesters’ participation in managing the resource.  相似文献   

New insights into the spatial variability of the surface water carbon dioxide in varying sea ice conditions in the Arctic Ocean   总被引：1，自引：0，他引：1  

Agneta Fransson  Melissa Chierici  Yukihiro Nojiri 《Continental Shelf Research》2009

In the summer of 2005, continuous surface water measurements of fugacity of CO₂ (fCO₂^sw), salinity and temperature were performed onboard the IB Oden along the Northwest Passage from Cape Farwell (South Greenland) to the Chukchi Sea. The aim was to investigate the importance of sea ice and river runoff on the spatial variability of fCO₂ and the sea–air CO₂ fluxes in the Arctic Ocean. Additional data was obtained from measurements of total alkalinity (A_T) by discrete surface water and water column sampling in the Canadian Arctic Archipelago (CAA), on the Mackenzie shelf, and in the Bering Strait. The linear relationship between A_T and salinity was used to evaluate and calculate the relative fractions of sea ice melt water and river runoff along the cruise track. High-frequency fCO₂^sw data showed rapid changes, due to variable sea ice conditions, freshwater addition, physical upwelling and biological processes. The fCO₂^sw varied between 102 and 678 μatm. Under the sea ice in the CAA and the northern Chukchi Sea, fCO₂^sw were largely CO₂ undersaturated of approximately 100 μatm lower than the atmospheric level. This suggested CO₂ uptake by biological production and limited sea–air CO₂ gas exchange due to the ice cover. In open areas, such as the relatively fresh water of the Mackenzie shelf and the Bering Strait, the fCO₂^sw values were close to the atmospheric CO₂ level. Upwelling of saline and relatively warm water at the Cape Bathurst caused a dramatic fCO₂^sw increase of about 100 μatm relative to the values in the CAA. At the southern part of the Chukchi Peninsula we found the highest fCO₂^sw values and the water was CO₂ supersaturated, likely due to upwelling. In the study area, the calculated sea–air CO₂ flux varied between an oceanic CO₂ sink of 140 mmol m⁻² d⁻¹ and an oceanic source of 18 mmol m⁻² d⁻¹. However, in the CAA and the northern Chukchi Sea, the sea ice cover prevented gas exchange, and the CO₂ fluxes were probably negligible at this time of the year. Assuming that the water was exposed to the atmosphere by total melting and gas exchange would be the only process, the CO₂ undersaturated water in the ice-covered areas will not have the time to reach the atmospheric CO₂ value, before the formation of new sea ice. This study highlights the value of using high-frequency measurements to gain increased insight into the variable and complex conditions, encountered on the shelves in the Arctic Ocean.  相似文献   

Effects of streamflow reductions on aquatic macroinvertebrates: linking groundwater withdrawals and assemblage response in southern New Jersey streams,USA     

Jonathan G. Kennen  Melissa L. Riskin  Emmanuel G. Charles 《水文科学杂志》2014,59(3-4):545-561

Abstract

A comprehensive hydro-ecological investigation was conducted to determine the ecological response of increased groundwater withdrawals from the Kirkwood-Cohansey aquifer system, an important source of water supply in southern New Jersey, USA. Collocated observations were made of aquatic-macroinvertebrate assemblages and stream hydrologic attributes to develop flow–ecology response relations. A sub-regional transient groundwater flow model (MODFLOW) was used to simulate three plausible high-stress groundwater-withdrawal scenarios which resulted in stream baseflow reductions of approximately 0.12, 0.20, and 0.26 m³ s^-1. These reduction scenarios were used to construct flow-alteration ecological response models to evaluate aquatic-macroinvertebrate response to streamflow reduction. For example, flow-alteration ecological response models indicate that if groundwater withdrawals diminish mean annual streamflow from 1.1 to 0.6 m³ s^-1, the abundance of intolerant taxa could be reduced by as much as 20%. These flow-alteration ecological response modelling results could be used by resource professionals to evaluate alternative water management strategies to determine maximum basin withdrawal rates that meet ongoing human water demand while protecting biological integrity.