Mercury in a northeastern Brazilian mangrove area, a case study: potential of the mangrove oyster Crassostrea rhizophorae as bioindicator for mercury

The Channel of Santa Cruz is a mangrove area in northeastern Brasil 40 km north of Recife. Until 1991 a chlor-alkali factory discharged large amounts of mercury into the main tributary of the channel, the Rio Botafogo. The objective of this study was to assess the potential of the mangrove oyster Crassostrea rhizophorae as a bioindicator for mercury in this area and to examine the influence of condition on mercury concentrations in the oysters. The investigation was carried out in the late rainy season (July to September) 1993, in the rainy season (April to June) 1994 and in the dry season (November/December) 1994. At 11 stations in the channel, mangrove oysters, surface sediments and suspended matter were sampled, representing different compartments of the system. The distribution of mercury in the Channel of Santa Cruz exhibited for all compartments the same distinct spatial pattern with maxima in the Rio Botafogo. Seasonal variations were small and revealed no clear tendencies. In addition, mangrove oysters were transplanted from more contaminated stations to less contaminated stations and vice versa. These experiments were designed to study the oysters' capability to adjust their mercury concentrations to a changing bioavailability of mercury. The transplantation experiments suggest that the oysters are capable to adjust to changing ambient mercury availability within a few months. The transplantation experiments also revealed the importance of condition changes on the mercury concentration of the oysters. This factor should not be ignored during pollution studies. However, condition had apparently no strong influence on the spatial or seasonal mercury variations of the oysters. The mangrove oyster is a suitable bioindicator for long-term changes in mercury availability. Received: 20 August 1997 / Accepted: 15 January 1998     

Zooplankton biomass in the ice-covered Weddell Sea,Antarctica

Zooplankton was sampled by a Rectangular Midwater Trawl (RMT 1 + 8) in Weddell Sea surface waters (0 to 300 m) between 66 and 78°S during austral summer (February – March 1983). Sixty-nine taxa including different developmental stages were considered and divided into 16 size classes between <1 and >39.5 mm length. Biomass was determined by taxon and size class for three different meso- and macroplankton communities in the oceanic region, on the northeastern shelf and on the southern shelf of the Weddell Sea. The highest biomass of 11.2 mg DW m^–3 (3.4 g DW m^–2) was found in the northeastern shelf community (70 to 74°S), where juvenile and adultEuphausia crystallorophias accounted for 3.7 mg DW m^–3 (1.1 g DW m^–2). Although not quantitatively sampled, early copepodite stages (CI to CIII) ofCalanoides acutus andCalanus propinquus ranked second with 2.7 mg DW m^–3 (0.8 g DW m^–2). Biomass in the northeastern shelf community was concentrated in the size ranges 1 to 4 mm and 19.5 to 39.5 mm. The oceanic community of the central Weddell Sea was dominated by copepods smaller than 5 mm, which made up half of the total oceanic biomass. The tunicateSalpa thompsoni (7.0 to 8.5 mm) was the dominant single species with 1.6 mg DW m^–3 (0.5 g DW m^–2). Euphausiids, mainly juvenile and adult krillEuphausia superba, comprised 1.2 mg DW m^–3 (0.4 g DW m^–2). Total standing stock in the oceanic community was 9.4 mg DWm^–3 (2.8 g DW m^–2). Lowest biomass values were found in the southern shelf community (south of 75°S) with 4.0 mg DW m^–3 (1.2 g DW m^–2), concentrated in the 1 to 4 mm and 14.5 to 34.5 mm size classes. Abundant species were the pteropodLimacina helicina (1 to 2 mm; 0.7 mg DW m^–3; 0.2 g DW m^–2) andE. crystallorophias (24.5 to 39.5 mm; 0.9 mg DW m^–3; 0.3 g DW m^–2). The data reveal that it is essential to distinguish among subsystems in the Southern Ocean. This leads to a better understanding of the structure and function of those pelagic food webs which represent alternatives to the paradigmatic krill-centered system.     

Feeding ecology and energetics of the Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica

Ecological and physiological studies focused on dietary preferences, lipid biochemistry and energetics within the three Antarctic chaetognaths Eukrohnia hamata, E. bathypelagica and E. bathyantarctica from meso- and bathypelagic depths. Eukrohnia hamata and E. bathypelagica respired 0.15 μL O₂ mg dry mass (DM)⁻¹ h⁻¹, which translates to an average metabolic loss of only <1.1% of body carbon per day. Lipid storage was not substantial in E. bathypelagica (mean 11.5 ± 6.5% DM) and E. bathyantarctica (mean 15.4 ± 4.1% DM) during summer and winter, suggesting year-round feeding of these predators mainly on copepods. In E. bathypelagica, total fatty acids were dominated by the fatty acids 16:0, 20:5(n-3) and 22:6(n-3) and in E. bathyantarctica also by 18:1(n-9), a fatty acid usually found in storage lipids. Only the latter species was characterized by significant amounts of wax esters, consisting largely of the common fatty alcohols 16:0, 20:1(n-9) and the unusual fatty alcohol isomer 22:1(n-9).     

INTEGRATING DEMOGRAPHIC AND LANDSAT (TM) DATA AT A WATERSHED SCALE1

ABSTRACT: Recurrent calls for integrated resource management urge that an understanding of human activities and populations be incorporated into natural resource research, management, and protection efforts. In this paper, we hypothesize that watersheds can be a valuable geography for organizing an inquiry into the relationship between humans and the environment, and we present a framework for conducting such efforts. The framework is grounded in the emerging field of landscape ecology and incorporates demographic theory and data. Demography has been advanced by technological capabilities associated with the 1990 Census. Employing Geographic Information System (GIS) tools, we couple Landsat Thematic Mapper (TM) land cover data with census‐derived housing density data to demonstrate the operation of our framework and its utility for better understanding human‐landscape interactions. In our investigation of the Kickapoo Watershed and two sub‐ watersheds, located in southwestern Wisconsin, we identify relationships between landscape composition and the distribution and social structure of human populations. Our findings offer insight into the interplay between people and biophysical systems.     

Modeling thermoelectric power generation in view of climate change: a comment

Numerous power plants in Europe had to be throttled in summer months of the years 2003 and 2006 due to water shortages and high water temperatures caused by a hot and dry summer. Therefore, the effects of higher temperatures on power plants have received much attention in the last years. One article published in Regional Environmental Change presents a study about ‘Modeling thermoelectric power generation in view of climate change’. In this article, the statement is given that other studies do not include aspects as environmental legislation or cots of water shortages. This comment will show that in at least one article cited these aspects are considered.