Estimating turbidity and total suspended matter in the Adour River plume (South Bay of Biscay) using MODIS 250-m imagery

The Basque coastal waters (South Bay of Biscay) are directly influenced by the Adour River freshwater plume. The Adour outflow leads to important variations of suspended matter concentrations and turbidity, which in turn may affect biological productivity and water quality. This study aims at both developing specific algorithms and testing the efficiency of atmospherically corrected MODIS-Aqua 250-m surface reflectance product (MYD09) to map total suspended matter concentrations and turbidity within the Adour coastal region. First, regional empirical algorithms based on in-situ data were tested to retrieve the concentration of total suspended matter and turbidity from the remote sensing reflectance. Then, the respective sensitivity of MODIS surface reflectance bands 1 and 2 for water quality application was investigated as well as the quality of atmospheric corrections. Finally, selected algorithms were applied to the MYD09 product. The resulting 250-m resolution maps were then compared to 1000-m maps produced by IFREMER and comparisons between satellite measurements and in-situ sampling points were performed. Results show that MODIS-Aqua band 1 (620–670 nm) is appropriate for predicting turbidity and total suspended matter concentrations using polynomial regression models, whilst band 2 is unadapted. Comparison between total suspended matter concentration 250-m resolution maps and mineral suspended matter 1000-m maps (generated by IFREMER) produced consistent results. A high correlation was obtained between turbidity measured in-situ and turbidity retrieved from MODIS-Aqua satellite data.     

THE HARVEST OF RAIN–FOREST BIRDS BY INDIGENOUS COMMUNITIES IN PANAMA*

In this article I attempt to shed light on the relationships between indigenous communities and bird populations through research on hunting in five neighboring villages in western Panama. Over eight months, 59 households captured 1,584 birds using rifles, sling‐shots, traps, and other methods, resulting in a total yield of 252 kilograms. Although hunters captured more than 125 avian species, just four species account for more than half of the total harvest. The most important game bird is the great curassow (Crax rubra), followed by the great tinamou (Tinamus major) and crested guan (Penelope purpurascens). The type and quantity of avifauna captured varies significantly according to habitat and hunting strategy. The spatial distribution of bird kill sites is highly concentrated, with 62 percent of the harvest by weight captured within just 1 kilometer of the participating households. Even the more vulnerable species are encountered close to home, suggesting that overhunting has not occurred.     

Enhanced regeneration of phosphorus during formation of the most recent eastern Mediterranean sapropel (S1)

Phosphorus regeneration and burial fluxes during and after formation of the most recent sapropel S1 were determined for two deep-basin, low-sedimentation sites in the eastern Mediterranean Sea. Organic C/P ratios and burial fluxes indicate enhanced regeneration of P relative to C during deposition of sapropel S1. This is largely due to the enhanced release of P from organic matter during sulfate reduction. Release of P from Fe-bound P also increased, but this was only a relatively minor source of dissolved P. Pore-water HPO₄²⁻ concentrations remained too low for carbonate fluorapatite formation. An increased burial of biogenic Ca-P (i.e., fish debris) was observed for one site. Estimated benthic fluxes of P during sapropel formation were elevated relative to the present day (∼900 to 2800 vs. ∼70 to 120 μmol m⁻² yr⁻¹). The present-day sedimentary P cycle in the deep-basin sediments is characterized by two major zones of reaction: (1) the zone near the sediment-water interface where substantial release of HPO₄²⁻ from organic matter takes place, and (2) the oxidation front at the top of the S1 where upward-diffusing HPO₄²⁻ from below the sapropel is sorbed to Fe-oxides. The efficiency of aerobic organisms in retaining P is reflected in the low organic C/P ratios in the oxidized part of the sapropel. Burial efficiencies for reactive P were significantly lower during S1 times compared with the present day (∼7 to 15% vs. 64 to 77%). Budget calculations for the eastern Mediterranean Sea demonstrate that the weakening of the antiestuarine circulation and the enhanced regeneration of P both contributed to a significant increase in deep-water HPO₄²⁻ concentrations during sapropel S1 times. Provided that sufficient vertical mixing occurred, enhanced regeneration of P at the seafloor may have played a key role in maintaining increased productivity during sapropel S1 formation.     

Genotyping of Rhodopirellula baltica organisms using multispacer sequence typing

Rhodopirellula baltica is a ubiquitous Planctomycetes organism isolated from marine environments worldwide. Multilocus sequence analysis (MLSA) has been the only method used to assess the diversity of R. baltica organisms. Here, we developed multispacer sequence typing (MST) genotyping and applied it to four R. baltica isolates from the French Mediterranean Sea and R. baltica DSM10527^T type strain. While MLSA yielded interpretable sequences for two of nine genes in three R. baltica isolates, MST based on sequencing two intergenic spacers yielded an unambiguous, strain‐specific profile for each one of the four R. baltica isolates under investigation. We propose that MST could be used as an alternative R. baltica genotyping method to assess the diversity of these Planctomycetes organisms.     

Are We There Yet? NSW local governments’ progress on climate change

Local governments are responding to top-down policy initiatives from both federal and State governments to reduce emissions, and adapt to any potential impacts of climate change. Although climate change is clearly a global problem, many of the solutions will be implemented at the local level. To explore this issue, the aim of this research was to examine regional variation in climate change response across New South Wales (NSW). To this end, between September 2010 and September 2011, we reviewed publicly available council and regional documentations for all NSW councils. The indicators of response examined were based on the NSW Greenhouse Plan (2005). These were awareness-raising, emissions reduction and adaptation planning. It was found that councils were undertaking many practical projects to fulfil the goals of this plan. As a result, they are abating significant quantities of emissions. Adaptation is progressing through the development of risk-based climate change adaptation plans. Councils are addressing particular areas of management, such as water management, assisted by guidelines which incorporate consideration for climate change as part of best practice. While overall responses to this threat are progressing, a distinct urban bias in action has been observed, due to biases in policy and funding arrangements.     

The closing of a seaway: ocean water masses and global climate change

The Late Neogene witnessed various major paleoceanographic changes that culminated in intense Northern Hemisphere Glaciation (NHG). The cause and effects of these changes are still debated. We use a multiproxy approach to determine the relative timing of the closure of the Panama gateway, changes in Atlantic circulation, global cooling and ice sheet growth. Benthic foraminiferal Mg/Ca records from a Pacific and an Atlantic Site have been produced and are interpreted in terms of bottom water temperatures. These Mg-temperature records are combined with published benthic δ¹³C, δ¹⁸O and erosion records to reconstruct the flow of proto-North Atlantic Deep Water (proto-NADW) over the past 12 Ma. The results suggest that between 12.5 and 10.5 Ma, and again between about 8.5 and 6 Ma, a nutrient-depleted water mass that was colder (by 1–2°C) and fresher than the intervening deep water mass filled the Atlantic basin. This proto-NADW became warmer (by 1°C) and saltier between 6 and 5 Ma, coincident with the restriction of surface water flow through the Central American Seaway. The Mg-temperature records define a subsequent global cooling trend of 3.5°C between 5 Ma and today. Early NHG in the late Miocene was perhaps related to the formation of the relatively cold, fresh proto-NADW. The formation of the warmer and saltier proto-NADW in the early Pliocene may have initially limited Northern Hemisphere ice growth. However, the increased moisture released at high northern latitudes associated with formation of ‘warm’ proto-NADW, coupled with the global temperature decrease of deep (and hence polar surface) waters, likely helped initiate the intense NHG of the Plio–Pleistocene.     

Optical remote sensing of submerged aquatic vegetation: Opportunities for shallow clearwater streams

Remote sensing has rarely been used as a tool to map and monitor submerged aquatic vegetation (SAV) in rivers, due to a combination of insufficient spatial resolution of available image data and strong attenuation of light in water through absorption and scattering. The latter process reduces the possibility to use spectral reflectance information to accurately classify submerged species. However, increasing availability of very high resolution (VHR) image data may enable the use of shape and texture features to help discriminate between species by taking an object based image analysis (OBIA) approach, and overcome some of the present limitations.This study aimed to investigate the possibility of using optical remote sensing for the detection and mapping of SAV. It firstly looked at the possibilities to discriminate submerged macrophyte species based on spectral information only. Reflectance spectra of three macrophyte species were measured in situ across a range of submergence depths. The results showed that water depth will be a limiting factor for the classification of species from remote sensing images. Only Spiked Water Milfoil (Myriophyllum spicatum) was indicated as spectrally distinct through ANOVA analysis, but subsequent Jeffries–Matusita distance analysis did not confirm this. In particular Water Crowfoot (Ranunculus fluitans) and Pondweed (Potamogeton pectinatus) could not be discriminated at 95% significance level. Spectral separability of these two species was also not possible without the effect of an overlying water column.Secondly, the possibility to improve species discrimination, using spatial and textural information was investigated for the same SAV species. VHR image data was acquired with a Near Infrared (NIR) sensitive DSLR camera from four different heights including a telescopic pole and a Helikite UAS. The results show that shape and texture information can improve the detection of the spectrally similar Pondweed and Water Crowfoot from VHR image data. The best performing feature ‘length/width ratio of sub-objects’ was obtained through expert knowledge. All of the shape and texture based features performed better at species differentiation than the spectrally based features.In conclusion this study has shown that there is considerable potential for the combination of VHR data and OBIA to map SAV in shallow stream environments, which can benefit species monitoring and management.     

Dynamics of sediment-laden underflows passing over a subaqueous sill: glacier-fed Peyto Lake, Alberta, Canada

The dynamic behaviour of sediment-laden underflows was examined in Peyto Lake, Alberta, Canada, which contains a midlake sill 7 m high. Sediment-laden underflows are driven by the downslope component of negative buoyant gravity multiplied by the current's thickness. Our measurements of wind, lake currents and water properties indicate that underflows pass over the sill due to the active storage of turbid suspension near the bottom in the deepest proximal region. Sill overflows occurred only when a hydrological threshold of the inflowing river was exceeded, causing quasicontinuous underflow and associated sedimentation in the distal region of the lake basin.     

A late Ordovician (Hirnantian) karstic surface in a submarine channel,recording glacio‐eustatic sea‐level changes: Meifod,central Wales

The growth and decay of the end‐Ordovician Gondwanan glaciation is globally reflected by facies changes in sedimentary sequences, which record a major eustatic fall and subsequent rise in the Hirnantian Stage at the end of the Ordovician. However, there are different reported estimates of the magnitude and pattern of sea‐level change. Particularly good evidence for end‐Ordovician sea‐level change comes from a sequence at Meifod in central Wales, which has a karstified limestone unit within a channel incised into marine shelf sediments. Pre‐glacial (Rawtheyan) mudstones have a diverse fauna suggesting a mid‐to‐deep‐shelf water depth of c. 60 m. The channel, 20 m deep, was incised into these mudstones and partially filled with a mixture of fine sand and detrital carbonate. The taphonomy of bioclasts and intraclasts indicates that many had a long residence time on the sea floor or suffered diagenesis after shallow burial before being resedimented into the channel. The presence of carbonates on the Welsh shelf is atypical and they are interpreted as having accumulated as patches during a minor regression prior to the main glacio‐eustatic fall. Comparison of the carbon stable‐isotopic values of the bioclast material with the global isotopic record confirms that most of the material is of Rawtheyan age, but that some is Hirnantian. The resedimented carbonates lithified rapidly and formed a limestone, several metres thick, in the deepest parts of the channel. As sea‐level fell, this limestone was exposed and eroded into karstic domes and pillars with a relief of over 2 m. The overall, glacio‐eustatic, sea‐level fall is estimated to be in excess of 80 m. A succeeding sea‐level rise estimated to be 40–50 m is recorded in the laminated crust that mantles the karstic domes and pillars. The crust is formed of encrusting bryozoans, associated cystoids, crinoid holdfasts and clusters of the brachiopod Paromalomena, which is normally associated with mid‐shelf environments. Fine sands buried the karst topography and accumulated to fill the channel. In the sandstones at the base of the channel there is a Hirnantia fauna, while in the sandstones high in the channel‐sequence there is cross‐stratification characteristic of mid‐shoreface environments. This would indicate a fall of sea‐level of c. 30 m. The subsequent major transgression marking the end of the glaciation is not recorded at the Meifod locality, but nearby exposures of mudstones suggest a return to mid‐to‐deep‐shelf environments, similar to those that prevailed before the Hirnantian regression. The Meifod sequence provides strong evidence for the magnitude of the Hirnantian sea‐level changes and by implication confirm larger estimates for the size of the ice sheets. Smaller oscillations in relative sea‐level seen at Meifod may be local phenomena or may reflect eustatic changes that have not been widely reported elsewhere. Copyright © 2005 John Wiley & Sons, Ltd.