Siliceous nanoplankton I. Newly discovered cysts from the Gulf of Alaska

Siliceous nanoplankton in the size range 2.5 to 5.5 m and of a type hitherto undescribed are reported from Eastern Subarctic water samples. Nine distinct cell types were recognizable, each possessing an unusual tetrahedral symmetry, resulting from the arrangement of 8 siliceous plates. Since the cells were abundant (maximum concentration of about 7×10⁵ cells 1^-1) and were distributed over a wide oceanic area (136° to 149°W), they could well play an important role in the food web in Subarctic seas. Similar cells were found simultaneously in Antarctic waters (see following paper: Silver et al., 1980), where they were as abundant and widespread as in the Subarctic. Evidence that the siliceous forms are likely a cyst stage and that they may be part of the life cycle of species of siliceous oceanic choanoflagellates is presented.Contribution No. 1149 from the Department of Oceanography, University of Washington     

URBAN IMPACTS ON PHYSICAL STREAM CONDITION: EFFECTS OF SPATIAL SCALE,CONNECTIVITY, AND LONGITUDINAL TRENDS1

ABSTRACT: An assessment of physical conditions in urban streams of the Puget Sound region, coupled with spatially explicit watershed characterizations, demonstrates the importance of spatial scale, drainage network connectivity, and longitudinal downstream trends when considering the effects of urbanization on streams. A rapid stream assessment technique and a multimetric index were used to describe the physical conditions of multiple reaches in four watersheds. Watersheds were characterized using geographic information system (GIS) derived landscape metrics that represent the magnitude of urbanization at three spatial scales and the connectivity of urban land. Physical conditions, as measured by the physical stream conditions index (PSCI), were best explained for the watersheds by two landscape metrics: quantity of intense and grassy urban land in the subwatershed and quantity of intense and grassy urban land within 500 m of the site (R²= 0.52, p > 0.0005). A multiple regression of PSCI with these metrics and an additional connectivity metric (proximity of a road crossing) provided the best model for the three urban watersheds (R²= 0.41, p > 0.0005). Analyses of longitudinal trends in PSCI within the three urban watersheds showed that conditions improved when a stream flowed through an intact riparian buffer with forest or wetland vegetation and without road crossings. Results demonstrate that information on spatial scale and patterns of urbanization is essential to understanding and successfully managing urban streams.     

URBANIZATION OF AQUATIC SYSTEMS: DEGRADATION THRESHOLDS,STORMWATER DETECTION,AND THE LIMITS OF MITIGATION1

ABSTRACT: Urbanization of a watershed degrades both the form and the function of the downstream aquatic system, causing changes that can occur rapidly and are very difficult to avoid or correct. A variety of physical data from lowland streams in western Washington displays the onset of readily observable aquatic-system degradation at a remarkably consistent level of development, typically about ten percent effective impervious area in a watershed. Even lower levels of urban development cause significant degradation in sensitive water bodies and a reduced, but less well quantified, level of function throughout the system as a whole. Unfortunately, established methods of mitigating the downstream impacts of urban development may have only limited effectiveness. Using continuous hydrologic modeling we have evaluated detention ponds designed by conventional event methodologies, and our findings demonstrate serious deficiencies in actual pond performance when compared to their design goals. Even with best efforts at mitigation, the sheer magnitude of development activities falling below a level of regulatory concern suggests that increased resource loss will invariably accompany development of a watershed. Without a better understanding of the critical processes that lead to degradation, some downstream aquatic-system damage is probably inevitable without limiting the extent of watershed development itself.     

Putting transdisciplinarity into practice: a mixed mode procedure for stakeholder participation in natural resource management

The definition of management actions in natural resource management requires the integration of all types of knowledge involved. An appropriate approach for such a challenge is the ideal of transdisciplinarity. A transdisciplinary process can be considered “consultative” when knowledge is simply gathered and collated, or “participatory” when knowledge integration is undertaken collectively. In this paper, we present a mixed mode procedure (i.e., using interviews, questionnaires, and group discussions) that empirically demonstrates the difference between consultative and participatory transdisciplinary processes. The mixed mode procedure is used for identifying the most relevant problems occurring in the coastal system of Praia da Vitória bay, Azores, Portugal. This mixed mode procedure is likely to be useful for other studies, because the results highlight the need to promote face-to-face interaction at the earliest opportunity, and because it allows an understanding to be gained of social learning processes, the influence of power, and participant behaviour during interaction with others.     

Estuarine Macrobenthic Community Structure in the Hawkesbury River, Australia: Relationships with Sediment Physicochemical and Anthropogenic Parameters

Macrobenthic community assemblage diversity and abundance were monitored on both Cowan and Berowra Creeks in the estuarine reaches of the Hawkesbury River, Sydney Australiaduring 1997–1998. Natural sediment physicochemical differenceswere assessed, along with low-level anthropogenic contaminantsincluding copper, lead, zinc, phosphorus and nitrogen. Contaminant levels at all sites were below sediment guidelinevalues for biological effects. Natural physicochemical sedimentdifferences were the main determinants in species assemblage patterns among sites. Three groupings of sites with similar assemblages were observed during February 1998. Berowra Creek sites, which were higher in organic content and silt/clay (andthus metals and nutrients), higher in pH and lower in salinity,were similar in terms of contributions by the polychaetes Ceratoneresis aequisetis, Scoloplos normalis, the isopod Cyathura hakea and the bivalve mollusc Soletellina alba.Sites on upper Cowan Creek, higher in organic content, silt/clay(nutrients and metals) and lower in salinity, were similar andseparated from other sites in terms of the polychaete Carazziella victoriensis and the gastropod mollusc Nassarius jonasii. Sites lower in Cowan Creek, tended to be higher in sand content, more saline and lower in organic contentand thus nutrient and metal concentrations. These sites were similar in terms of contributions of the polychaete Sigalion bandaensis and the bivalve molluscs, Mysella vitrea and Tellina deltoidalis. The biotic assemblage patterns were not maintained temporally, suggesting the importance of monitoring over time to assess possible futureimpacts. Aggregating species data to the family level resultedin similar site discrimination. Site differences were less distinct at higher taxonomic levels and suggests future monitoring at the family level is sufficient to detect assemblage differences among sites. The results obtained represent the difficulty in detecting responses to low-levelcontamination at the community level, and provide a sound anticipatory baseline for the assessment of future possible anthropogenic disturbance in the Hawkesbury River.     

Polychlorinated biphenyls (PCBs) in Africa: a review of environmental levels

Several studies have shown an increase in PCB sources in Africa due to leakage and wrongly disposed transformers, continuing import of e-waste from countries of the North, shipwreck, and biomass burning. Techniques used in the recycling of waste such as melting and open burning to recover precious metals make PCBs contained in waste and other semivolatile organic substances prone to volatilization, which has resulted in an increase of PCB levels in air, blood, breast milk, and fish in several regions of Africa. Consequences for workers performing these activities without adequate measures of protection could result in adverse human health effects. Recent biodegradation studies in Africa have revealed the existence of exotic bacterial strains exhibiting unique and unusual PCB metabolic capability in terms of array of congeners that can serve as carbon source and diversity of congeners attacked, marking considerable progress in the development of effective bioremediation strategies for PCB-contaminated matrices such as sediments and soils in tropical regions. Action must be taken to find and deal with the major African sources of these pollutants. The precise sources of the PCB plume should be pinned down and used to complete the pollutant inventories of African countries. These nations must then be helped to safely dispose of the potentially dangerous chemicals.     

Remediation of heavy metals and dyes from wastewater using cellulose-based adsorbents

Environmental Chemistry Letters - Heavy metals and dyes are major pollutants that pose potential threat to the health of humans and ecosystems. Various technologies are available to remediate such...     

The guessing of mine safety signs meaning: effects of user factors and cognitive sign features

This study investigated the effects of user factors and cognitive sign features on the guessability of mine safety signs. Sixty na?ve participants guessed the meanings and rated the cognitive sign features of 42 Mainland Chinese mine safety signs. The results showed that some user factors were significant predictors of guessing performance, while some were not. As expected, guessability scores varied significantly with the cognitive sign features of familiarity, concreteness, simplicity, meaningfulness and semantic closeness. The findings emphasize the need to create awareness of the importance of mine safety and promote understanding of mine safety sign meanings amongst people in their work environments. To design more user-friendly mine safety signs, industrial designers should develop and evaluate signs with consideration of the significant user factors and the 5 sign features tested here.