Anomalously high precipitation and river discharge during the spring of 2005 caused considerable freshening and depletion of dissolved inorganic carbon (DIC) in surface waters along the coastal Gulf of Maine. Surface pCO2 and total alkalinity (TA) were monitored by repeated underway sampling of a cross-shelf transect in the western Gulf of Maine (GOM) during 2004–05 to examine how riverine fluxes, mixing, and subsequent biological activity exert control on surface DIC in this region. Most of the variability in surface DIC concentration was attributable to mixing of low DIC river water with higher DIC, saline GOM waters, but net biological uptake of DIC was significant especially during the spring and summer seasons. The extent and persistence of the coastal freshwater intrusion exerted considerable influence on net carbon dynamics. Integrated over the 10-m surface layer of our study region (∼5 × 104 km2), net biological DIC uptake was 0.48 × 108 mol C during April–July of 2004 compared to 1.33 × 108 mol C during April–July of 2005. We found the temporal signature and magnitude of DIC cycling to be different in adjacent plume-influenced and non-plume regions. Extreme events such as the freshwater anomaly observed in 2005 will affect mean estimates of coastal carbon fluxes, thus budgets based on short time series of observations may be skewed and should be viewed with caution. 相似文献
Cementation of bryozoan-echinoid-benthic foraminiferal temperate shelf carbonates of the Oligocene Te Kuiti Group, North Island, New Zealand, occurred mainly during subsurface burial. The calcite cements in the limestones are dominated by equant and syntaxial rim spar which typically becomes ferroan (given an iron supply) and, compared to the skeletal material with normal marine δ18O values from +2 to −1‰, more depleted in 18O with depth of burial, the δ18O composition of bulk cement samples ranging from −1 to −7‰. These trends reflect the establishment in pore waters during sediment burial of reducing conditions and gradually increasing temperatures (20–50°C), respectively. The δ13C values (0 to +3‰) of the cements remain the same as the host marine shells, suggesting the source of carbon in the cements was simply redistributed marine carbonate derived from shell dissolution.
Two gradational burial diagenetic environments influenced by marine-derived porewaters are arbitrarily distinguished: shallow burial phase and moderate burial phase. During the shallow burial phase, down to 500–600 m sub-bottom depth, the carbonates lost at least 25% of their original porosity by mechanical compaction and were selectively cemented by non-ferroan or usually ferroan, variably luminescent, slightly 18O-depleted sparry calcite cement (δ18O −2 to −4‰), mainly as syntaxial rims about echinoid grains. These shallow-burial cements form less than about 10% of total cement in the majority of the limestones and their source was probably mainly mild intergranular dissolution of calcitic skeletal fragments accompanying the onset of chemical compaction. During the moderate burial phase, between about 600 and 1100 m sub-bottom depth, porosity loss continued (typically to about 70% of its original value) as a result of pressure-solution of calcitic bioclasts associated with more advanced stages of chemical compaction. This involved development of a wide variety of non-sutured and microstylolitic solution seams, including both single and composite, wispy or continuous, bedding-parallel types and non-parallel reticulate forms. The released carbonate was precipitated as ferroan (or non-ferroan where iron supply was negligible), dull luminescent, strongly 18O-depleted (δ18O −4 to −7‰), mainly equant calcite spar cement, occluding available pore space in the limestones. 相似文献
The spatial locations of food retailers are considered to be an influential aspect of population consumption patterns. Such contextual relationships are often related to socio‐economic deprivation, with disparities in accessibility having important implications. This study used Geographic Information Systems and an Enhanced Two‐Step Floating Catchment Area model of spatial accessibility to further understand such relationships within urban areas of New Zealand. Findings, while mixed, indicate that there is generally increased accessibility to all food retailers in highly deprived areas. Understanding these socio–spatial relationships in local environments has important implications for policy initiatives, health outcomes and sustainable development. 相似文献
Emerging infectious diseases (EIDs) of wildlife have characteristics that make them difficult to manage, leading to reactive and often ineffective management strategies. Currently, two fungal pathogens, Pseudogymnoascus destructans (Pd) and Batrachochytrium salamandrivorans (Bsal), are causing declines in novel host species. To improve the application of management strategies addressing the risk of these pathogens to North American wildlife, we queried wildlife managers about their concerns regarding managing populations of bats and amphibians potentially impacted by Pd and Bsal. Using these responses, we identified aspects of each decision problem that were shared across pathogens, regions and agencies – and found similarities in decision-problem elements for disease management. Reframing management problems as decisions can enable managers to identify similarities across EIDs, i.e. uncertainties within management actions, and improve reactive responses if proactive management is not possible. Such an approach recognizes context-specific constraints and identifies relevant uncertainties that must be reduced in developing a response. 相似文献
The drivers (social) and pressures (physical) of marine debris have typically been examined separately. We redress this by using social and beach surveys at nine Tasmanian beaches, across three coastlines and within three categories of urbanisation, to examine whether people acknowledge that their actions contribute to the issue of marine debris, and whether these social drivers are reflected in the amount of marine debris detected on beaches. A large proportion (75%) of survey participants do not litter at beaches; with age, gender, income and residency influencing littering behaviour. Thus, participants recognise that littering at beaches is a problem. This social trend was reflected in the small amounts of debris that were detected. Furthermore, the amount of debris was not statistically influenced by the degree of beach urbanisation, the coastline sampled, or the proximity to beach access points. By linking social and physical aspects of this issue, management outcomes can be improved. 相似文献
Small catchments have served as sentinels of forest ecosystem responses to changes in air quality and climate. The Hubbard Brook Experimental Forest in New Hampshire has been tracking catchment water budgets and their controls – meteorology and vegetation – since 1956. Water budgets in four reference catchments indicated an approximately 30% increase in the evapotranspiration (ET) as estimated by the difference between precipitation (P) and runoff (RO) starting in 2010 and continuing through 2019. We analyzed the annual water budgets, cumulative deviations of the daily P, RO and water budget residual (WBR = P − RO), potential ET (PET) and indicators of subsurface storage to gain greater insight into this shift in the water budgets. The PET and the subsurface storage indicators suggest that this change in WBR was primarily due to increasing ET. While multiple long-term hydrological and micrometeorological data sets were used to detect and investigate this change in ET, additional measurements of groundwater storage and soil moisture would enable better estimation of ET within the catchment water balance. Increasing the breadth of long-term measurements across small gauged catchments allows them to serve as more effective sentinels of substantial hydrologic changes like the ET increase that we observed. 相似文献