Landscape consequences of aggregation rules for functional equivalence in compensatory mitigation programs

Mitigation and offset programs designed to compensate for ecosystem function losses due to development must balance losses from affected ecosystems with gains in restored ecosystems. Aggregation rules applied to ecosystem functions to assess site equivalence are based on implicit assumptions about the substitutability of functions among sites and can profoundly influence the distribution of restored ecosystem functions on the landscape. We investigated the consequences of rules applied to the aggregation of ecosystem functions for wetland offsets in the Beaverhill watershed in Alberta, Canada. We considered the fate of 3 ecosystem functions: hydrology, water purification, and biodiversity. We set up an affect‐and‐offset algorithm to simulate the effect of aggregation rules on ecosystem function for wetland offsets. Cobenefits and trade‐offs among functions and the constraints posed by the quantity and quality of restorable sites resulted in a redistribution of functions between affected and offset wetlands. Hydrology and water purification functions were positively correlated with one another and negatively correlated with biodiversity function. Weighted‐average rules did not replace functions in proportion to their weights. Rules prioritizing biodiversity function led to more monofunctional wetlands and landscapes. The minimum rule, for which the wetland score was equal to the worst performing function, promoted multifunctional wetlands and landscapes. The maximum rule, for which the wetland score was equal to the best performing function, promoted monofunctional wetlands and multifunctional landscapes. Because of implicit trade‐offs among ecosystem functions, no‐net‐loss objectives for multiple functions should be constructed within a landscape context. Based on our results, we suggest criteria for the design of aggregation rules for no net loss of ecosystem functions within a landscape context include the concepts of substitutability, cobenefits and trade‐offs, landscape constraints, heterogeneity, and the precautionary principle.     

Does Wetland Location Matter When Managing Wetlands for Watershed‐Scale Flood and Drought Resilience?

Wetland protection and restoration strategies that are designed to promote hydrologic resilience do not incorporate the location of wetlands relative to the main stream network. This is primarily attributed to the lack of knowledge on the effects of wetland location on wetland hydrologic function (e.g., flood and drought mitigation). Here, we combined a watershed‐scale, surface–subsurface, fully distributed, physically based hydrologic model with historical, existing, and lost (drained) wetland maps in the Nose Creek watershed in the Prairie Pothole Region of North America to (1) estimate the hydrologic functions of lost wetlands and (2) estimate the hydrologic functions of wetlands located at different distances from the main stream network. Modeling results showed wetland loss altered streamflow, decreasing baseflow and increasing stream peakflow during the period of the precipitation events that led to major flooding in the watershed and downstream cities. In addition, we found that wetlands closer to the main stream network played a disproportionately important role in attenuating peakflow, while wetland location was not important for regulating baseflow. The findings of this study provide information for watershed managers that can help to prioritize wetland restoration efforts for flood or drought risk mitigation.     

Proximity to competitors changes secondary metabolites of non-indigenous cup corals, Tubastraea spp., in the southwest Atlantic

Competition for space changes species’ distributions and community organization on tropical rocky shores, and the presence of secondary metabolites in the tissues of non-indigenous species may aid them in establishing and expanding their range through negative competitive interactions. The aim of this study was to describe the range of chemical substances produced by the non-indigenous cup corals Tubastraea coccinea and T. tagusensis and to test whether they varied in the field when the corals were placed in proximity to two local competitors. Cholest-5-en-3β-ol and 9-octadecanoic acid were two common secondary metabolites found in the tissues of Tubastraea. In the competition interaction experiment, necrosis was detected on the tissues of the coral Mussismilia hispida, and this species induced variation in sterol, alkaloid, and fatty acid production in Tubastraea tissues. In contrast, a sponge overgrew Tubastraea colonies. These results indicate that chemical defense may contribute to the ability of these non-indigenous corals to invade native communities.     

Investigation of sequential and enzymatic extraction of arsenic from drinking water distribution solids using ICP-MS

A sequential extraction approach was utilized to estimate the distribution of arsenite [As(iii)] and arsenate [As(v)] on iron oxide/hydroxide solids obtained from drinking water distribution systems. The arsenic (As) associated with these solids can be segregated into three operationally defined categories (exchangeable, amorphous and crystalline) according to the sequential extraction literature. The exchangeable As, for the six drinking water solids evaluated, was estimated using 10 mM MgCl(2) and 10 mM NaH(2)PO(4) and represented between 5-34% of the total As available from the solid. The amorphously bound As was estimated using 10 mM (NH(4))(2)C(2)O(4) and represented between 57-124% of the As available from the respective solid. Finally, the crystalline bound As was estimated using titanium citrate and this represented less than 1.5% of the As associated with the solids. A synthetic stomach/intestine extraction approach was also applied to the distribution solids. The stomach fluid was found to extract between 0.5-33.3 microg g(-1) As and 120-2,360 microg g(-1) iron (Fe). The As concentrations in the intestine fluid were between 0.02-0.04 microg g(-1) while the Fe concentration ranged from 0.06-0.7 microg g(-1) for the first six drinking water distribution solids. The elevated Fe levels associated with the stomach fluid were found to produce Fe based precipitates when the intestinal treatment was applied. Preliminary observations indicate that most of the aqueous Fe in the stomach fluid is ferric ion and the observed precipitate produced in the intestine fluid is consistent with the decreased solubility of ferric ion at the pH associated with the intestine.     

印染行业清洁生产技术

论述了目前印染行业水污染的现状及原因，指出调整产业结构、应用新工艺、大力提倡节约用水、清沽生产将是印染行业实现可持续发展的必由之路。     

Epibiosis on cerith shells in a seagrass bed: correlation of shell occupant with epizoite distribution and abundance

The cerith Cerithium atratum (Born 1778) is an abundant gastropod in the seagrass beds at Cabo Frio, Brazil. In order to estimate the ecological importance of cerith shells as a rare hard substratum in the seagrass bed, the abundances of C. atratum and of cerith shells occupied by hermit crabs were quantified. The mean densities of C. atratum and hermit crabs were 1887 and 100 individuals m⁻², respectively, and these provided 0.5 m² shell area m⁻² available for epizoite colonization. The tube-forming polychaete Hydroides plateni (Kinberg 1867) and oyster Ostrea puelchana Orbigny, 1841 were the dominant visible epizoites on inhabited cerith shells. These epizoite populations were compared in order to investigate whether the temporal and spatial patterns in the epibiotic community were related to ecological and behavioral aspects of the occupant species (cerith or hermit crab). Larger cerith shells had a greater abundance of epizoites. Each epizoite showed a preference for a different occupant of the shells (the oyster for C. atratum and the polychaete for cerith shells occupied by hermit crabs). The oyster showed a seasonal pattern in abundance on C. atratum, being more common in fall (March–April). The distribution of the epizoites on the shells depended on the shell occupant species and was probably related to their different foraging activity –C. atratum ploughs half buried through the sediment, while the hermit crab crawls on the sediment surface. In both cases, the activity of the shell occupant was considered to be beneficial to the epizoites, as empty shells and shell fragments did not support a macroepifauna. Received: 1 May 2000 / Accepted: 8 August 2000     

Safeguarding Wetlands and Their Connections within Wetlandscapes to Improve Conservation Outcomes for Threatened Amphibian Species

Wetlands should not be considered as independent objects but as dynamically connected objects, collectively known as wetlandscapes. We developed a framework that analyzes the influences of wetland suitability and connectivity on amphibian distributions. We defined two indices: a Wetland Suitability Index describing wetland quality and a Movement Permeability Index characterizing wetland connectivity for amphibian population dynamics. These indices were calculated from raster datasets and time‐varying inundation estimates. The indices were used to define a wetlandscape and an amphibian model was used to simulate population dynamics within the wetlandscape. The framework was applied to the Nose Creek watershed, a highly modified wetlandscape in Alberta, Canada. Two amphibian species were selected with different habitat preferences: the Northern Leopard Frog that prefers wet habitats and has high mobility over land, and the Great Plains Toad that prefers terrestrial habitats and has low mobility over land. We found each amphibian species had a “preferred” wetlandscape, reflecting their life cycle traits and migration strategies which in turn were dependent on the hydrological and ecological connections within the wetlandscape. This study highlights the importance of investigating both individual wetlands and the wetlandscape and considering both wetland habitat quality and connectivity as non‐substitutable properties that act jointly, but differently, on population dynamics.     

Distribution of Diatoms in a Forested Stream Containing a Series of Interconnected Lakes

We explored the spatial variation in diatom communities withinthe Turkey Lakes Watershed (TLW). The TLW is a single watershed in an old growth sugar maple forest that contains an alternatingseries of stream and lake embayments. Near the outlet of each lake, we sampled pools and riffles to determine abundance and diversity of diatom communities along this hydrologic system. Diatom diversity, measured by Shannon-Weaver Index, richness andevenness, increased steadily downstream before eventually decreasing near the watershed outlet. Canonical CorrespondenceAnalysis indicated that diatom genera were correlated with streamchemistry. Upper reaches were the least productive, characterizedby lower pH (<7), higher N:P (113:1 to 124:1, dominated by complex forms of N), and high mean relative abundances of Eunotia spp., Tabellaria spp., and Pinnularia spp. Middle and lower reaches were more productive, characterized byhigher pH (>7), lower N:P (71:1 to 90:1, dominated by simple forms of N, e.g., nitrate-N), and high mean relative abundances of Cymbella spp. and Brachysira spp. Achnanthesminutissima (Kutz.) Hustedt, the most abundant species, and Navicula spp., Nitzschia spp., Gomphonema spp., and Frustrulia spp. were represented at all stream sites. Thisstudy revealed that within the TLW, a hydrologic system of the same stream order, the diatom community was influenced by a nutrient gradient, where the stream and its intervening lakes contributed to a shift from acidic, inorganic N-poor upper reaches to a circum-neutral, inorganic N-richer outlet. By imparting genera-specific stresses, stream flow (i.e. pools vs. riffles) further shaped the diatom community.     

Biophysical suitability,economic pressure and land-cover change: a global probabilistic approach and insights for REDD+

There has been a concerted effort by the international scientific community to understand the multiple causes and patterns of land-cover change to support sustainable land management. Here, we examined biophysical suitability, and a novel integrated index of “Economic Pressure on Land” (EPL) to explain land cover in the year 2000, and estimated the likelihood of future land-cover change through 2050, including protected area effectiveness. Biophysical suitability and EPL explained almost half of the global pattern of land cover (R ² = 0.45), increasing to almost two-thirds in areas where a long-term equilibrium is likely to have been reached (e.g. R ² = 0.64 in Europe). We identify a high likelihood of future land-cover change in vast areas with relatively lower current and past deforestation (e.g. the Congo Basin). Further, we simulated emissions arising from a “business as usual” and two reducing emissions from deforestation and forest degradation (REDD) scenarios by incorporating data on biomass carbon. As our model incorporates all biome types, it highlights a crucial aspect of the ongoing REDD + debate: if restricted to forests, “cross-biome leakage” would severely reduce REDD + effectiveness for climate change mitigation. If forests were protected from deforestation yet without measures to tackle the drivers of land-cover change, REDD + would only reduce 30 % of total emissions from land-cover change. Fifty-five percent of emissions reductions from forests would be compensated by increased emissions in other biomes. These results suggest that, although REDD + remains a very promising mitigation tool, implementation of complementary measures to reduce land demand is necessary to prevent this leakage.     

Groundwaters at Risk: Wetland Loss Changes Sources,Lengthens Pathways,and Decelerates Rejuvenation of Groundwater Resources

Wetland loss alters the hydrology of wetlandscapes in poorly understood ways. To quantify the effects of wetland loss on subsurface hydrology, a physically based hydrologic model that simulates the timing and pathways of subsurface hydrologic connections was coupled with wetland inventories over a 50‐year period during which substantial wetland loss occurred. The model revealed, based on vertical variations in saturated hydraulic conductivities, wetland loss of different degrees led to a contraction of catchment contributing areas to local surface waters but an expansion of contributing areas to the regional surface water body. This shift in groundwater contributing areas reflected (1) a decrease in baseflow contribution to the local surface water bodies, and (2) an increase in the transit time and length of subsurface hydrologic connections with an associated increase in the magnitude and age of baseflow discharging to the regional surface water body. The model also showed regions with thick permeable aquifers were particularly sensitive to the loss of wetlands. Our ability to predict these changes in hydrology of the watershed provides important support for designing science‐based policies to promote sustainable water resource management.