Modeling the Invasion of Holly (Ilex aquifolium): Spatial Relationships and Spread Trajectories

In this study, we investigated the environmental factors associated with the establishment of invasive English holly (Ilex aquifolium) and the spatiotemporal trajectories of its potential spread. We collected georeferenced presence and absence and demographic data of holly between 2011 and 2014 in Saint Edward State Park, Washington. We analyzed them through a spatially explicit framework that combines multiple logistic regression, cellular automata, and bivariate quadratic modeling. Results showed that the presence of holly is influenced by the proximity to evergreen coniferous vegetation and forest edge, distance to streams, forest structure, and slope direction. Our study confirmed that local environmental conditions, species characteristics, and vegetative and dispersal mechanisms play a significant role in determining the rate and success of holly establishment across the different phases of invasion. Invasive species management plans should consider both species characteristics and their habitat and the interactions among them when planning long-term strategies for control and eradication.     

Determination of reaeration‐rate coefficient by modified tracer gas technique

The modified tracer gas technique is used to determine the reaeration coefficient in six different water bodies of the Itajaí River basin, three with rural land use and three in urban areas. Propane was used as the tracer gas and Rhodamine WT as the conservative tracer, providing information on dilution, mixing and dispersion. Liquefied petroleum gas was used instead of high purity propane, aimed at reducing the costs associated with the field trials. Reaeration‐rate coefficients observed in the field ranged from 25.8 to 367.7 d^?1. Two data sets could be observed where smaller streams had substantially larger coefficients of between 133.1 and 367.7 d^?1, while the larger streams had values ??ranging from 25.8 to 54.5 d^?1. Five empirical equations were evaluated by comparing the values ??obtained in the field. The equations proposed by Tsivolgou and Wallace and Tsivoglou and Neal showed greater adherence to the values ??determined in the tests. Reaeration‐rate coefficients obtained in the field were correlated with the hydrodynamic characteristics of the watercourses, thus establishing a mathematical function through which to obtain estimates for future evaluations. The R² value obtained using this equation was 0.959, indicating a high correlation between the calculated values ??and those estimated in the field. Copyright © 2012 John Wiley & Sons, Ltd.     

Evidence for rapid ice flow and proglacial lake evolution around the central Strait of Magellan region,southernmost Patagonia

This paper presents a detailed palaeoglaciological reconstruction of ice sheet dynamics in the Seno Skyring, Seno Otway and Strait of Magellan region of the former Patagonian Ice Sheet, with a particular focus on previously hypothesised zones of rapid ice flow and the evolution of proglacial lakes. Geomorphological mapping from a combination of satellite imagery and oblique and vertical aerial photographs reveals a variety of glacial landforms that are grouped into several discrete flow‐sets and associated ice margin positions. The most distinct features are represented by flow‐sets of highly elongate streamlined glacial lineations on both sides of the Strait of Magellan. Based on the shape and dimensions of the flow‐sets and their abrupt lateral margins, a transverse and longitudinal variation in glacial lineation length and elongation ratio, and the reported presence of a potentially deformable bed and thrust moraines, the flow‐sets are interpreted as zones of rapid ice flow within the Otway and Magellan lobes. We hypothesise that this provides evidence for contemporaneous surge‐like advances within the lobes, which may explain the asymmetry in the lobate margin positions on either side of the strait. The mechanisms that initiated rapid flow are unclear, but are likely to have been influenced by internal factors such as a change in thermal/hydrological conditions at the bed. The topography of the region suggests ice‐dammed lakes would have formed as the ice lobes retreated. The westernmost of the former lakes, Lake Skyring, is delimited by a series of palaeo‐shorelines surrounding the present‐day lake Laguna Blanca and we reconstruct lake evolution based on manipulation of a digital elevation model. The size and orientation of meltwater channels and a large outwash plain indicate that Lake Skyring drained eastwards towards the Strait of Magellan, probably quite rapidly. We conclude that the potential for quasi‐independent surge‐like behaviour within adjacent lobes raises the possibility that, during climate‐driven ice expansion, some advances in this region may have been partly controlled by secondary internal feedback mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

Estimating the expansion of urban areas and urban heat islands (UHI) in Ghana: a case study

Natural Hazards - This research is focused on identifying urban sprawl pattern and extent in two rapidly growing major Ghanaian cities (Accra and Kumasi) and how urban expansion affected heat...     

Apparent decoupling of the He and Ne isotope systematics of the Icelandic mantle: The role of He depletion, melt mixing, degassing fractionation and air interaction

We present new He-Ne data for geothermal fluids and He-Ne-Ar data for basalts from throughout the Icelandic neovolcanic zones and older parts of the Icelandic crust. Geothermal fluids, subglacial glasses, and mafic phenocrysts are characterized by a wide range in helium isotope ratios (³He/⁴He) encompassing typical MORB-like ratios through values as high as 36.8 R_A (where R_A = air ³He/⁴He). Although neon in geothermal fluids is dominated by an atmospheric component, samples from the northwest peninsula show a small excess of nucleogenic ²¹Ne, likely produced in-situ and released to circulating fluids. In contrast, geothermal fluids from the neovolcanic zones show evidence of a contribution of mantle-derived neon, as indicated by ²⁰Ne enrichments up to 3% compared to air. The neon isotope composition of subglacial glasses reveals that mantle neon is derived from both depleted MORB-mantle and a primordial, ‘solar’ mantle component. However, binary mixing between these two endmembers can account for the He-Ne isotope characteristics of the basalts only if the ³He/²²Ne ratio of the primordial mantle endmember is lower than in the MORB component. Indeed, the helium to neon elemental ratios (⁴He/²¹Ne∗ and ³He/²²Ne_s where ²¹Ne∗ = nucleogenic ²¹Ne and ²²Ne_s = ‘solar’-derived ²²Ne) of the majority of Icelandic subglacial glasses are lower than theoretical values for Earth’s mantle, as observed previously for other OIB samples. Helium may be depleted relative to neon in high-³He/⁴He ratio parental melts due to either more compatible behavior during low-degree partial melting or more extensive diffusive loss relative to the heavier noble gases. However, Icelandic glasses show higher ⁴He/⁴⁰Ar∗ (⁴⁰Ar∗ = radiogenic Ar) values for a given ⁴He/²¹Ne∗ value compared to the majority of other OIB samples: this observation is consistent with extensive open-system equilibrium degassing, likely promoted by lower confining pressures during subglacial eruptions of Icelandic lavas. Taken together, the He-Ne-Ar systematics of Icelandic subglacial glasses are imprinted with the overlapping effects of helium depletion in the high-³He/⁴He ratio parental melt, binary mixing of two distinct mantle components, degassing fractionation and interaction with atmospheric noble gases. However, it is still possible to discern differences in the noble gas characteristics of the Icelandic mantle source beneath the neovolcanic zones, with MORB-like He-Ne isotope features prevalent in the Northern Rift Zone and a sharp transition to more primitive ‘solar-like’ characteristics in central and southern Iceland.     

Spectral Irradiance and Phytoplankton Community Composition in a Blackwater-Dominated Estuary,Winyah Bay,South Carolina,USA

We investigated spatial and temporal relationships between spectral irradiance and phytoplankton community composition in the blackwater-influenced estuary Winyah Bay, South Carolina. Upstream, high concentrations of chromophoric dissolved organic matter (CDOM) absorbed blue wavelengths, resulting in a predominantly red light field. Green light prevailed downstream near the lower-CDOM coastal ocean, and phytoplankton community composition was distinct from upstream and mid-estuarine communities. Diatoms were abundant throughout the estuary in January, August, and October, cryptophytes dominated in July, and chlorophytes were abundant in December 2006. Only diatoms and chlorophytes showed significant covariation with the spectral attenuation coefficient (k(λ)): Chlorophytes showed positive relationships with k(442) (blue light) while diatoms were negatively correlated with k(442) and k(490) (violet to blue). Phytoplankton community composition in Winyah Bay appears to be driven by strong horizontal flow rather than gradients in spectral irradiance, but results indicate that water color is likely to play a greater role in blackwater-influenced estuaries with longer residence times.     

Distribution of Diatoms and Development of Diatom-Based Models for Inferring Salinity and Nutrient Concentrations in Florida Bay and Adjacent Coastal Wetlands of South Florida (USA)

The composition and distribution of diatom algae inhabiting estuaries and coasts of the subtropical Americas are poorly documented, especially relative to the central role diatoms play in coastal food webs and to their potential utility as sentinels of environmental change in these threatened ecosystems. Here, we document the distribution of diatoms among the diverse habitat types and long environmental gradients represented by the shallow topographic relief of the South Florida, USA, coastline. A total of 592 species were encountered from 38 freshwater, mangrove, and marine locations in the Everglades wetland and Florida Bay during two seasonal collections, with the highest diversity occurring at sites of high salinity and low water column organic carbon concentration (WTOC). Freshwater, mangrove, and estuarine assemblages were compositionally distinct, but seasonal differences were only detected in mangrove and estuarine sites where solute concentration differed greatly between wet and dry seasons. Epiphytic, planktonic, and sediment assemblages were compositionally similar, implying a high degree of mixing along the shallow, tidal, and storm-prone coast. The relationships between diatom taxa and salinity, water total phosphorus (WTP), water total nitrogen (WTN), and WTOC concentrations were determined and incorporated into weighted averaging partial least squares regression models. Salinity was the most influential variable, resulting in a highly predictive model (r _apparent² = 0.97, r _jackknife² = 0.95) that can be used in the future to infer changes in coastal freshwater delivery or sea-level rise in South Florida and compositionally similar environments. Models predicting WTN (r _apparent² = 0.75, r _jackknife² = 0.46), WTP (r _apparent² = 0.75, r _jackknife² = 0.49), and WTOC (r _apparent² = 0.79, r _jackknife² = 0.57) were also strong, suggesting that diatoms can provide reliable inferences of changes in solute delivery to the coastal ecosystem.     

Coastal management challenges from a community perspective: The problem of ‘stealth privatization’ in a Canadian fishery

Intertidal clam fisheries seem ideal candidates for the devolution of management authority from government to local stakeholders. In St. Mary's Bay, Nova Scotia, a private firm recently applied for a 10-year renewal of a large (1,627 ha) lease for quahog clam aquaculture. This case study examines the challenges of implementing community-based natural resource management (CBNRM) in rural fisheries within a broad integrated coastal management (ICM) institutional environment that favours corporate stakeholders. The challenges facing clam harvesters in rural Digby Neck, Nova Scotia arise from poor communication and coordination within government and between government and communities, as well as higher-level policy conflicts. The most important challenge arises from ‘stealth privatization’ of clam beaches. A single firm was granted rights of first refusal to depurate all clams harvested from closed (polluted) beaches in the region, resulting in the de facto privatization of all (polluted and unpolluted) clam beaches. Experiences in other parts of Canada suggest there may be community-based governance approaches that avoid the pitfalls associated with corporate management of clam beaches. New thinking is required about how to moderate the ‘privatization paradigm’ so prevalent within senior levels of government in order to ensure environmental and social sustainability in rural fishing communities.