The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

Water column optical properties of Greater Florida Bay were investigated in the context of their impacts on seagrass distribution. Scattering played an important role in light attenuation throughout the shallow water system. The northwest region was characterized by an absence of seagrasses and the highest scattering by particles, mostly from resuspended carbonate sediments. Higher seagrass densities were observed in the open waters just north of the Florida Keys, where absorption coefficients were dominated by colored dissolved organic material and scattering was lower than in the northwest region. Patchy dense seagrass meadows were observed in the clear waters south of the Keys where scattering and absorption were low and contributed equally to light attenuation. In general, seagrasses were observed in areas where >7.5% of surface irradiance reached the plants and where optical properties were not dominated by scattering. Although the prevention of eutrophication and nuisance algal blooms may be necessary for preserving seagrass meadows in this system, our observations and model calculations indicate that nutrient control alone may be insufficient to permit seagrass recolonization if optical properties are dominated by particulate scattering from resuspended sediments.     

Teaching Spatial Thinking and Geospatial Technologies Through Citizen Mapping and Problem-Based Inquiry in Grades 7-12

Our project introduced students in grades 7 through 12 to spatial thinking and geospatial technologies in the context of challenges in their community. We used a mix of levels of inquiry to advance learning from teacher- to student-guided through a citizen mapping group activity. Student-suggested problem-based topics included parks and community gardens, crime, housing, and youth employment opportunities. Qualitative methods were used to evaluate students’ knowledge of spatial thinking and geospatial technologies, including map interpretation, a case study, daily exit slips, and interviews. Overall, the students’ awareness of their community, spatial thinking, and geospatial technologies increased as a result of participation.     

The phytoplankton bloom response to wind events and upwelled nutrients during the CoOP WEST study

In the coastal waters off northern California, seasonal wind-driven upwelling supplies abundant nutrients to be processed by phytoplankton productivity. As part of the Coastal Ocean Processes: Wind Events and Shelf Transport (CoOP WEST) study, nutrients, CO₂, size-fractionated chlorophyll, and phytoplankton community structure were measured in the upwelling region off Bodega Bay, CA, during May–June 2000, 2001 and 2002. The ability of this ecosystem to assimilate nitrate (NO₃) and silicic acid/silicate (Si(OH)₄) and accumulate particulate material (i.e. phytoplankton) was realized in all 3 years, following short events of upwelling-favorable winds, followed by periods of relaxed winds. This was observed as phytoplankton blooms, dominated by chlorophyll in cells greater than 5 μm in diameter, that reduced the ambient nutrients to zero. These communities were located over the near-shore shelf (<100 m depth) and were dominated by diatoms. An optimal window of 3–7 days of relaxed winds, following an upwelling pulse, was required for chlorophyll accumulation. The large-celled phytoplankton that result are likely important players in coastal new production and carbon cycling.     

Early Benthic Organism Colonization on a Caribbean Coral Reef (Barbados, West Indies): a Plate Experimental Approach

Abstract. Macrofaunal colonization was studied using coral plates fixed at 10 m depth on a fringing reef in Barbados, West Indies. Two sites were compared: Spring Garden, a site that is affected by eutrophication, and Six Men's Bay which is relatively free of this effect. Two sets of plates were immersed in winter and spring 1990 at each site and monitored for 28 and 19 weeks, respectively. Green and brown algae colonized first, followed 2 weeks later by ostracods, cumaceans, amphipods and polychaetes: terebellids, nereidids and syllids. Most colonizers either nestled or encrusted. A total of 11 017 invertebrates belonging to 145 species were collected. Polychaetes were the most abundant and diverse zoological group. Considering polychaetes, crustaceans and molluscs, the study sites shared around 75% of the species. Overall, densities were higher on lower (shaded) surfaces while diversities were higher on upper (illuminated) sides. Similarity coefficients and correspondence analysis showed different macrobenthic assemblages and colonization patterns in light and shaded and in polluted and unpolluted sites. Coral plates were associated according to their 'immersion time' and were closely linked to their stage of development. Spring Garden (polluted) presented a higher number of soft-bottom and deposit-feeder species ( e.g. , Capitella capitata ).     

Legal and institutional tools to mitigate marine turtle bycatch: Argentina as a case study

This paper explores conservation policy pertinent to three species of marine turtles affected by fisheries, while crossing jurisdictions in their seasonal migrations through the SW Atlantic, particularly the Argentine waters. This case study reviews local legal and institutional frameworks for Argentina and concludes that tools are in place to monitor and mitigate the negative impact of bycatch on the populations. Argentina is signatory of the most relevant international treaties aimed at protecting transboundary species (e.g. Inter-American Convention for the Protection and Conservation of Sea Turtles, Convention on the Conservation of Migratory Species of Wild Animals). Legislation also exists at the federal and provincial levels. Yet, accidental captures continue to occur due to weaknesses in enforcement and the low priority that conservation has in fisheries management decisions. Some urgent practical actions supported by policy are suggested: (a) placement of on-board observers in coastal fishing fleets, (b) application of existing mitigation measures to reduce bycatch, (c) design of a national plan of action for marine turtles in Argentina, and (d) development of a regional plan between Argentina, Brazil and Uruguay. Stakeholder involvement, especially the fishing sector but also the civil society, would be important to energize practical and effective conservation decisions. The example of Argentina is typical for the region and may apply to other countries as well. The conservation community requires investing more in the application of policy, concomitant with perfecting legal tools.     

The impact of climatic and non-climatic factors on land surface temperature in southwestern Romania

Land surface temperature is one of the most important parameters related to global warming. It depends mainly on soil type, discontinuous vegetation cover, or lack of precipitation. The main purpose of this paper is to investigate the relationship between high LST, synoptic conditions and air masses trajectories, vegetation cover, and soil type in one of the driest region in Romania. In order to calculate the land surface temperature and normalized difference vegetation index, five satellite images of LANDSAT missions 5 and 7, covering a period of 26 years (1986–2011), were selected, all of them collected in the month of June. The areas with low vegetation density were derived from normalized difference vegetation index, while soil types have been extracted from Corine Land Cover database. HYSPLIT application was employed to identify the air masses origin based on their backward trajectories for each of the five study cases. Pearson, logarithmic, and quadratic correlations were used to detect the relationships between land surface temperature and observed ground temperatures, as well as between land surface temperature and normalized difference vegetation index. The most important findings are: strong correlation between land surface temperature derived from satellite images and maximum ground temperature recorded in a weather station located in the area, as well as between areas with land surface temperature equal to or higher than 40.0 °C and those with lack of vegetation; the sandy soils are the most prone to high land surface temperature and lack of vegetation, followed by the chernozems and brown soils; extremely severe drought events may occur in the region.     

Evidence for lithium-aluminosilicate supersaturation of pegmatite-forming melts

New experimental data on the solubility of lithium (Li) at spodumene (LiAlSi₂O₆) and petalite (LiAlSi₄O₁₀) saturation at 500 MPa and 550–750 °C reveal evidence for lithium supersaturation of pegmatite-forming melts before the formation of Li-aluminosilicates. The degree of Li enrichment in granitic melts can reach ~11,000 ppm above the saturation value before the crystallization of Li-aluminosilicate minerals at lower temperatures. Comparison of the experimental results with the spodumene-rich Moblan pegmatite (Quebec) is consistent with extreme Li enrichment of the pegmatite-forming melt prior to emplacement, which cannot be explained with equilibrium crystallization of Li-aluminosilicates from a common granitic melt. The results of this study support the model of disequilibrium fractional crystallization through liquidus undercooling as the most plausible mechanism for the generation of such Li-rich ore resources.     

Decentring poverty studies: Middle class alliances and the social construction of poverty

Editors' Note: The following is the tenth in the Singapore Journal of Tropical Geography Lecture Series. It is based on the plenary presentation of 13 April at the AAG held in Seattle in 2011. In this essay I explore relational poverty analysis to take seriously the spatially varied intersections of political‐economic, social ordering and cultural‐political processes in shaping understandings of poverty. My work as part of the Middle Class Poverty Politics Research Group employs a relational comparative methodology to theorize where, when and under what circumstances those framed as ‘middle class’ act in opposition to or in solidarity with those named as ‘poor’. Our approach focuses on the exploitative effects of capital accumulation, processes of unequal sociospatial categorization and political and discursive systems that limit or exclude the poor. Our research focuses on places experiencing capitalist crisis because intense periods of restructuring highlight material and discursive struggles over poverty. We conclude by identifying a research agenda focused on the ways in which poverty politics are constituted by the nonpoor through place and in the articulation of places with processes of political economy, governance and cultural politics.     

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

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.     

Insights into silicic melt generation using plagioclase, quartz and melt inclusions from the caldera-forming Rotoiti eruption, Taupo volcanic zone, New Zealand

The Rotoiti (~120 km³) and Earthquake Flat (~10 km³) eruptions occurred in close succession from the Okataina Volcanic Centre at ~50 ka. While accessory mineral geochronology points to long periods of crystallization prior to eruption (10⁴–10⁵ years) and separate thermal histories for the magmas, little was known about the rates and processes of the final melt production and eruption. Crystal zoning patterns in plagioclase and quartz reveal the thermal and compositional history of the magmatic system leading up to the eruption. The dominant modal phase, plagioclase, displays considerable within-crystal zonation: An_37–74, ~40–227 ppm MgO, 45–227 ppm TiO₂, 416–910 ppm Sr and 168–1164 ppm Ba. Resorption horizons in the crystals are marked by sharp increases (10–30%) in Sr, MgO and X_An that reflect changes in melt composition and are consistent with open system processes. Melt inclusions display further evidence for open system behaviour, some are depleted in Sr and Ba relative to accompanying matrix glass not consistent with crystallization of modal assemblage. MI also display a wide range in XH₂O that is consistent with volatile fluxing. Quartz CL images reveal zoning that is truncated by resorption, and accompanied by abrupt increases in Ti concentration (30–80 ppm) that reflect temperature increases ~50–110°C. Diffusion across these resorption horizons is restricted to zones of <20 μm, suggesting most crystallization within the magma occurred in <2000 years. These episodes are brief compared to the longevity (10⁴–10⁵ year) of the crystal mush zones. All textural and compositional features observed within the quartz and plagioclase crystals are best explained by periodic mafic intrusions repeatedly melting parts of a crystal-rich zone and recharging the system with silicic melt. These periodic influxes of silicic melt would have accumulated to form the large volume of magma that fed the caldera-forming Rotoiti eruption.