Application of empirical and semi-analytical algorithms to MERIS data for estimating chlorophyll a in Case 2 waters of Lake Erie

Lake Erie is biologically the most active lake among the Great Lakes of North America, experiencing seasonal harmful algal blooms (HABs). The early detection of HABs in the Western Basin of Lake Erie (WBLE) requires a more efficient and accurate monitoring tool. Remote sensing is an efficient tool with high spatial and temporal coverage that can allow accurate and timely detection of the HABs. The WBLE is heavily influenced by the surrounding terrestrial ecosystem via rivers such as the Sandusky River and the Maumee River. As a result, the optical properties of the WBLE are influenced by multiple color producing agents (CPAs) such as phytoplankton, colored dissolved organic matter (CDOM), organic detritus, and terrigenous inorganic particles. The diversity of the CPAs and their non-linear interactions makes these waters optically complex, and the task of optical remote sensing for retrieving estimates of CPAs more challenging. Chlorophyll a, which is the primary light harvesting pigment in all phytoplankton, is used as a proxy for algal biomass. In this study, several published remote sensing algorithms and band ratio models were applied to the reflectance data from the full resolution MERIS sensor to remotely estimate chlorophyll a concentrations in the WBLE. Efficiency of the sensor and the algorithms performance were tested through a least squares regression and residual analysis. The results indicate that, among the suite of existing bio-optical models, the Simis semi-analytical algorithm provided the best model results for measures of algal biomass in the optically complex WBLE with R ² of 0.65, RMSE 0.85 μg/l, (n = 71, P < 0.05). The superior results of this model in detecting chlorophyll a are attributed to several factors including optimizing spectral regions that are less sensitive to CDOM and the incorporation of correction factors such as absorption effects due to pure water (a _w), backscatter (b _b) from suspended matter and interference due to phycocyanin (δ), a major accessory pigment in the WBLE.     

Recent paleolimnology of three lakes in Northwestern Minnesota

A paleolimnological study was undertaken to investigate changes in three Minnesota lakes over the last 100 years and to demonstrate the stratigraphic effects of cultural eutrophication in two of them. The study combined the analysis of the lake sediment from short cores with stratigraphic analyses of pollen, plant macrofossils, mollusks, diatoms and certain other algae, chydorid Cladocera, and Daphnia ephippia.The rise of Ambrosia type pollen (ragweed) marks the onset of interference with the landscape by European man, which can be closely dated. Calculations of sedimentation rates from this base gave reasonable correlations of other stratigraphic events with historical events.Elk Lake is considered “unpolluted” today and was chosen as a control. Man's effects are limited to logging some of the surrounding forest and to the construction of a dam. Small changes in the lake's fauna and flora are demonstrated, showing the sensitivity of the lake to changes in its catchment area.Lake Sallie and St. Clair Lake, in the same watershed as the city of Detroit Lakes, have been affected not only by logging but also by addition of nutrients from agricultural runoff and sewage effluent. Considerable responses by the lake organisms are apparent. In Lake Sallie the changes were gradual, but in St. Clair Lake they were very abrupt because the lake was partially drained at the same time and the water volume was thereby reduced.The merits of such an integrated study, the types of information gained from the analyses of the various fossils, and the wider application of the results are discussed.     

Response of Tidal Creek Fish Communities to Dredging and Coastal Development Pressures in a Shallow-Water Estuary

To investigate the effects of dredging and associated development pressures (i.e., shoreline armoring, developed land use) on fish, three sets of paired dredged and undredged tidal creeks were surveyed within Lynnhaven River, Virginia. Fish species diversity, community abundance, biomass, and size structure were compared among creeks and related to watershed, shoreline, and physicochemical characteristics. Mean fish community characteristics (e.g., abundance) were similar among creeks; however, species-specific analysis revealed subtle differences. Species biomass differed between dredged and undredged creeks, though species abundance was similar. Turbidity highly influenced differences in species abundance among creeks, while organic matter, dissolved oxygen, turbidity, and shoreline hardening may be influencing biomass patterns. The most recently dredged creek appeared to provide less suitable nursery habitat for some species than historically dredged creeks, suggesting initial adverse effects with eventual recovery. Protective measures, such as preservation of marshes, dredge depth, and time-of-year restrictions, may be moderating development and dredging pressures.     

Species diversity and emergence patterns of nematocerous flies (Insecta: Diptera) from three coastal salt marshes in prince Edward Island, Canada

Emerging insects were monitored every 10 days between early May and late August 1993, from tidal pools in three coastal salt marshes on Prince Edward Island, Canada. The salt marsh pools ranged from about 1 m² to > 1,000 m² in surface area, and had salinities ranging from 11–27‰ Water temperatures through the study period ranged from 4–46°C. Most of the emerging insects were flies (Diptera; 85%), and two-thirds of these were in the sub-Order Nematocera, mainly Chironomidae, Ceratopogonidae, and Culicidae. Forty-three species of Nematocera were identified, although most of these were rare occurrences, and twelve of the species are undescribed. No consistent relationships were found between abundance or diversity and pool size or marsh for Nematocera species overall, although some species showed a statistical preference for a particular marsh or pool size. Emergence patterns were consistent between marshes for species found in different marshes, but overall patterns were highly variable, depending upon species.     

Cenozoic evolution of the eastern Black Sea: A test of depth-dependent stretching models

Subsidence analysis of the eastern Black Sea basin suggests that the stratigraphy of this deep, extensional basin can be explained by a predominantly pure-shear stretching history. A strain-rate inversion method that assumes pure-shear extension obtains good fits between observed and predicted stratigraphy. A relatively pure-shear strain distribution is also obtained when a strain-rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form. The timing of opening of the eastern Black Sea, which occupied a back-arc position during the closure of the Tethys Ocean, has also been a subject of intense debate; competing theories called for basin opening during the Jurassic, Cretaceous or Paleocene/Eocene. Our work suggests that extension likely continued into the early Cenozoic, in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism. Further basin deepening also appears to have occurred in the last ～ 20 myr. This anomalous subsidence event is focused in the northern part of the basin and reaches its peak at ～ 15–10 Ma. We suggest that this comparatively localized shortening is associated with the northward movement of the Arabian plate. We also explore the effects of paleowater depth and elastic thickness on the results. These parameters are controversial, particularly for deep-water basins and margins, but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy.     

Life histories in cyberspace: life writing as a development tool for rural women

Increasingly, information and communication technology (ICT) is being used as a development tool. For example, a recent innovative experiment by the FIDAMERICA development cybernetwork (sponsored by IFAD, the International Fund for Agricultural Development) in Latin America used an electronic network to collect, post and discuss rural women's life histories, intending to support gender mainstreaming in IFAD projects. However, cybernetworking processes can also reflect contradictory agendas and power relations that ultimately make them a site of contestation. In the FIDAMERICA case, the authors did not participate in the electronic conference, nor were there any subsequent efforts to connect them or to develop this process further.In this paper, I argue that the analysis of increasingly complex cybernetworked development efforts must incorporate a correspondingly sophisticated technique that can uncover the nuanced relations of transnational cyber communication; and I propose that an actor-network approach should be investigated as an analytical framework in these cases. I then apply this approach to the case study, using field research conducted with the participants of the FIDAMERICA electronic life history project in Central America. I conclude that an actor-network approach is a fruitful means by which these processes can be both understood and improved.     

Identifying the spatial pattern and importance of hydro‐geomorphic drainage impairments on unpaved roads in the northeastern USA

Roads have been widely studied as sources of runoff and sediment and identified as pollutant production sources to receiving waters. Despite the wealth of research on logging roads in forested, upland settings, little work has been conducted to examine the role of extensive networks of rural, low‐volume, unpaved roads on water quality degradation at the catchment scale. We studied a network of municipal unpaved roads in the northeastern US to identify the type and spatial extent of ‘hydro‐geomorphic impairments’ to water quality. We mapped erosional and depositional features on roads to develop an estimate of pollutant production. We also mapped the type and location of design interventions or best management practices (BMPs) used to improve road drainage and mitigate water quality impairment. We used statistical analyses to identify key controls on the frequency and magnitude of erosional features on the road network, and GIS to scale up from the survey results to the catchment scale to identify the likely importance of unpaved roads as a pollutant source in this setting. An average of 21 hydro‐geomorphic impairments were mapped per kilometer of road, averaging 0.3 m³ in volume. Road gradient and slope position were key controls on the occurrence of these features. The presence of BMPs effectively reduced erosion frequency. Scaled up to the watershed and using a conservative estimate of road–stream connectivity, our results for the Winooski River watershed in the northeastern US suggest that roughly 16% and 6% of the average annual sediment and phosphorus flux, respectively, of the Winooski River may be derived from unpaved roads. Our study identifies an under‐appreciated source of water quality degradation in rural watersheds, provides insights into identifying ‘hot spots’ of pollutant production associated with these networks, and points to effectiveness of design interventions in mitigating these adverse impacts on water quality. Copyright © 2017 John Wiley & Sons, Ltd.