Seeds of Rhizophora mangle L. were planted and comparatively assessed in six mangroves of Todos os Santos Bay, Bahia, Brazil. Five of the mangroves were on the north of the bay, an area under the influence of oil activities: two areas around the Landulpho Alves Refinery in Mataripe, and in Madre de Deus Island, Pati Island, and Fontes Island. The control site was a mangrove located on the south of the bay at Jiribatuba on Itaparica Island. In January and March, 1994, 1995 and 1998, sets of seeds were established and distributed in a pattern at regular intervals of 0.1, 0.5 and 1.0 m from one another. Every 3 months, the seedlings were assessed for fixation, height, number of lateral branches, surface area and wet and dry weight of leaves. During 1998, five individual seedlings were removed for biomass determination every 6 months. All variables were co-related with environmental conditions. After 12 months, a significant growth pattern difference ( p<0.05) was noted between seedlings from the mangrove around the refinery and those from Jiribatuba, mainly related to the rates of fixation higher than 50% and growth of leaves and precocious lateral branches to the two most impacted mangroves around the refinery, and Madre de Deus and Pati Islands. This branching was not observed on the seedlings grown in the mangroves of Fontes Island and Jiribatuba. The construction of an effluent emission channel into one of the mangrove area from the refinery began in 1998. One hundred and twenty-five seedlings 1 yr in age and other young plants died following direct contact with these effluents in February, 1999.

The Aratu Bay ecosystem (12°48′S; 38°28′W), located in an industrialized area, was compared with a similar but undisturbed ecosystem, Iguape Bay, in order to determine the impact of industry on water quality during the last forty years. Comparison was based on simple and low cost methodologies using bioassays on oyster embryos, validated by a survey of a benthic activity index. A bioassay method based on oyster embryo development was used to compare water quality from the study areas. A high percentage (93.2 and 97.3) of abnormal oyster embryo development was observed in water samples from one area (south and southeast) of the bay where, besides receiving heavy discharges of industrial effluents, water circulation is restricted. At the north end of the bay where the area is shallow, and some industrial discharges are present, water quality data indicated that the area was stressed. Little effect of industrial impact has been noted around the Cotegipe channel, a deep area where the water circulation pattern is heavy and the water well mixed. Validation of this survey has been achieved by the simple method of investigating benthic activity in the area. Quadrat counts of active benthic galleries were used as an index of community activity for comparative analysis between sampling stations and for discriminating between polluted and unpolluted sites. This research has shown that the quadrat counts of active benthic galleries, at least in areas of comparable homogeneous substrate, can be used as a viable index of environmental impact, when interpreted together with other source of data, such as early-life-stage tests. This new approach proved to be effective and led to the recommendation of remedial policies in the area.

The toxicity of surface waters and interstitial waters from sediments were determined at six study sites in Todos os Santos Bay, Bahia, Brazil, to evaluate the possibility of chronic environmental impact induced by 40 years of exposure to the local petroleum industry. Samples collected from four sites associated with the extraction, transportation and refinement of petroleum, and from two control sites, were tested at seven three-month intervals. Toxicological assays using acute mortality of brine shrimp ( Artemia salina) nauplii and chronic abnormalities of sea urchin ( Echinometra lucunter) and mangrove oyster ( Crassostrea rhizophorae) larvae were employed. Friedman non-parametric analyses of variance integrated seasonal variations in species response patterns and revealed significant differences among the study sites. Ranging the among-site variations for each organism in each sampling period, on a scale from 0.00 (minimum response) to 1.00 (maximum response), permitted the calculation of a single mean value for each species and the ordination of the sites on a qualitative scale of relative impact. Although the ordinations varied with species, the reduction of three species response patterns to a common relative scale also permitted their integration into a single multispecies ordination of the study sites. A cluster analysis of the six sites and two aquatic substrates, based on their toxicity to all three species, illustrated the similarities and differences between locations. Interstitial waters were more toxic, revealing an integrated ordination of Station 6≤Station 5≤(Station 3=Station2)≤(Station 4=Station 1). The ordination based on surface waters was Station 6≤Station 5≤(Station 2=Station 1=Station 3)<Station 4. In combination, the three procedures served efficiently for the description and inferential testing of the multispecies responses and, complemented with additional data on species diversity and chemical contamination of the sediment, confirmed the existence of chronic impact within the study area.

Explosives used in ammunition have been dumped in both lakes and oceans before the potential environmental effects of these chemicals were understood. Growing environmental concern in society and in the Swedish military resulted in a project dealing with the aquatic toxicology of explosives. The aim of the present study was to assess the hazard of six explosives by determining the acute sediment and water phase toxicity for two crustaceans ( Daphnia magna and Nitocra spinipes). Detoxification during storage was used as an indication of degradability (hydrolysis and biodegradation). The effect of ultraviolet light on the toxicity of these compounds was determined by post-exposure to ultraviolet light and determination of toxicity enhancement. The explosives were picric acid, trinitrotoluene, (2,4-dinitrotoluene), hexahydro-1,3,5-trinitro-1,3,5-trazine, nitroguanidine, and pentyl. The stabilising agent diphenylamine was tested in the same way. For the major explosive, trinitrotoluene, the water-phase EC/LC 50s were between 5 and 20 mg l −1 and the toxicity was not significantly affected by storage of test solutions for 30 days, indicating hydrolytic stability. The toxicity was not affected by addition of sediment, indicating that trinitrotoluene was not bound appreciably to sediment, but toxicity decreased after storage for 30 days in the presence of sediment, indicating biological degradation or slow adsorption of the chemical. The toxicity of the other explosives was similar or lower than for trinitrotoluene, but the stabilising agent diphenylamine was slightly more toxic with EC/LC 50s between 0.5 and 5 mg l −1. Photoinduced toxicity by ultraviolet light is known for many chemicals including polycyclic aromatic hydrocarbons and trinitrotoluene. The latter was confirmed in this study and especially for degraded trinitrotoluene. 2,4-Dinitrotoluene, which is one degradation product of trinitrotoluene was also activated by ultraviolet light. The toxicity of diphenylamine decreased after storage in water (hydrolysis) and with sediment (biodegradation), but both diphenylamine and its degradation products exhibited photoinduced toxicity.

Exergy and specific exergy have been found together with nine other ecological attributes for 12 coastal ecosystems. The correlation of the 11 attributes was examined, and the extent to which exergy and specific exergy can be applied as indicators to assess ecosystem health was discussed. The two concepts cover a range of important properties of ecosystems, but other indicators are also required to provide a sufficiently comprehensive assessment of ecosystem health.

The chemical and toxicological information given in this short communication is based on two sediment samples of limited amount taken from Lake Baikal. The samples received detailed chemical assessment since information about Lake Baikal sediments is scarce. The sediments were tested for sediment bound toxicity by liquid phase (Microtox) and solid phase (Hyalella) assays. The organic and inorganic chemical analyses were carried out with current technology followed in Canada, which may be useful for comparisons with other aquatic ecosystems. A wide range of organic compounds such as organochlorine pesticides, chlorinated diphenyl ethers, polychlorinated biphenyls, chlorinated dibenzo-p-dioxins and furans, coplanar polychlorinated biphenyls and polyaromatic hydrocarbons comprised the suite of compounds analysed for environmental levels. Generally, the full scan for high-resolution gas chromatography/high-resolution mass spectrometry electron impact analysis showed somewhat similar profiles for both the near-shore and off-shore stations. However, organic analysis indicated the near-shore station to be relatively more contaminated than the off-shore station. These chemical results were not supported by the Microtox and Hyalella bioassay experiments. The bioassays suggested that the near-shore and off-shore sediment samples were non-toxic. The necessity of performing both chemical as well as biological evaluations with a battery of assays is once again emphasized for ecosystem health assessment.

The results of the long-term investigations of phytoplankton of the whole of Lake Baikal summarizing almost 40years of systematic observations are given in this paper. These studies draw attention to spatial heterogeneity of planktonic biomass across the basin during the spring maximal bloom. The research of vertical distribution of phytoplankton during different years allows us to specify the role of phytoplankton in the cycle of organic substances and in biological productivity of Lake Baikal. For the first time, Baikal picophytoplankton, peculiarities of its production, seasonal and inter-annual dynamics, biocoenotic interrelations and its role in the ecosystem of Lake Baikal have been described. Changes occurring in Baikal pelagial phytocoenoses during the 1970–1990s in comparison with those of 1950–1960s have been revealed.

The objective of this study is to summarise limnological effects of cultural eutrophication in some Chinese lakes. Detailed data are shown for Lake Tai Hu as an example for a very large shallow lake affected by anthropogenic impacts. Urban and industrial waste water discharged to the lake result in high nutrient concentrations, large algal blooms dominated by cyanobacteria, mainly species of Microcystis and strong horizontal gradients. Algal growth in this lake is mainly light and/or phosphorus limited. This situation is typical for most of the lakes included in this review although some of the large deep lakes seem to be nitrogen deficient. In some cases toxicological effects may be the reason for observed discrepancies. Lakes are of vital importance for populations in China as drinking water and nutritional resources. To prevent water shortage because of conflicting usage, anticipation, control and management of water pollution is urgently needed. Moreover, efforts must be taken to rehabilitate deteriorated freshwater ecosystems.

The world's largest lakes, really inland seas, are characterised by long retention times, and are dominated by internal physical forcing, generally low nutrient loadings and predominantly internal recycling. Most are oligotrophic. Many are severely phosphorus deficient. Certainly few ever support large crops of phytoplankton. Horizontal heterogeneity sometimes permits enhanced production in shallow bays or behind thermal bars and occasional blooms develop under conditions of near-surface stratification.An assessment of published information on the composition and seasonality of phytoplankton in the open water habitats of these lakes confirms the oligotrophic nature of the world's great lakes. There is a predominance of diatoms at all latitudes; chrysophytes are seasonally prominent in some lakes at high latitude; other flagellates, including dinoflagellates, and species of cyanobacteria represent increasing proportions of the pelagic biomass towards the equator. There is an indication that species composition is influenced by underwater light availability and a positive correlation between Microcystis plankton and relatively higher concentrations of total phosphorus (TP>30μgl−1) is suggested. Picoplankton is apparently abundant during periods of relatively high insolation of the water column. Although the carrying capacity of the nutrients available is scarcely large, the production of biomass is strongly related to seasonal variability in the intensity and extent of water-column mixing and its relation to the periodicity and underwater penetration of photosynthetically active radiation. Attainment of nutrient-limited crops generally coincides with shallow mixing whereas deep circulation suppresses production.The differential effects of latitude, local climate and salinity upon this general deduction are also evaluated. The role of grazing, its contribution to nutrient recycling, and its contribution to sustaining pelagic food webs, is also considered. The paper makes some deductions about the threats placed on large-lake ecosystems by pollution, eutrophication and acidification and upon how their ecosystem health might be monitored and conserved in the future.