Assessing the recovery of lakes in southeastern Canada from the effects of acidic deposition

Reductions in North American sulfur dioxide (SO2) emissions promoted expectations that aquatic ecosystems in southeastern Canada would soon recover from acidification. Only lakes located near smelters that have dramatically reduced emissions approach this expectation. Lakes in the Atlantic provinces, Quebec and Ontario affected only by long-range sources show a general decline in sulfate (SO4(2-)) concentrations, but with a relatively smaller compensating increase in pH or alkalinity. Several factors may contribute to the constrained (or most likely delayed) acidity response: declining base cation concentrations, drought-induced mobilization of SO4(2-), damaged internal alkalinity generation mechanisms, and perhaps increasing nitrate or organic anion levels. Monitoring to detect biological recovery in southeastern Canada is extremely limited, but where it occurs, there is little evidence of recovery outside of the Sudbury/Killarney area. Both the occurrence of Atlantic salmon in Nova Scotia rivers and the breeding success of Common Loons in Ontario lakes are in fact declining although factors beyond acidification also play a role. Chemical and biological models predict that much greater SO2 emission reductions than those presently required by legislation will be needed to promote widespread chemical and latterly, biological recovery. It may be unrealistic to expect that pre-industrial chemical and biological conditions can ever be reestablished in many lakes of southeastern Canada.     

Trade-offs and performances of a range of alternative global climate architectures for post-2012

Quantitative assessments help to highlight the main features of climate policies by better identifying their strengths and weaknesses. In this study, we develop a grading system for assessing thirteen proposals for post-2012 climate policy. We believe that these proposals contain appropriate policy instruments which will be considered for discussions about how to design the post-2012 climate agreement. Our grades are based on four criteria: environmental effectiveness, cost effectiveness, distributional considerations and institutional feasibility. We analyze the grades with two complementary methods: principal component and cluster analysis. Our results entail three policy implications. Firstly, the higher the number of policy instruments a proposal comprises, the more difficult might be its implementation. Secondly, proposals which include a meaningful effort by the U.S. tend to fail in environmental effectiveness and institutional feasibility. Thirdly, we identify that the “first best” and the “second best” approaches belong to a stable policy group, and both may be considered as suitable candidates for post-2012 climate policy.     

Production of glycine betaine and dimethylsulfoniopropionate in marine phytoplankton. II. N-limited chemostat cultures

The influence of salinity on the time elapsed between two successive molts and the size reached after each molt were studied at 30, 21, 12 and 3‰S in juveniles of two co-occurring grapsid species, Cyrtograpsus angulatus and C. altimanus, cultured under identical conditions of temperature, photoperiod and food. Juvenile growth patterns were compared between these species (which differ in size-at-maturity and maximum size). C. angulatus grew faster than C. altimanus, reflecting a higher increment per molt and a shorter intermolt period. A significant difference existed between the number of instars preceding the size of maturity in both species: >11 in C. angulatus, 6 in C. altimanus. There was evidence of a differential effect of low salinity on growth. By the end of the experiment, individuals of both species were smaller at the lowest salinity (3‰) tested; the largest crabs developed at 21‰ (C. angulatus) and 30‰ (C. altimanus). The size difference between the “optimal” and the less suitable salinities in the sixth crab instar was 12.4% in C. angulatus and 35% in C. altimanus. During early juvenile development (Crab Instars 1 to 4), there were slight differences in intermolt period among salinities in C. angulatus, but large differences in C. altimanus. The longest intermolt period of C. altimanus was at 3‰S and the shortest at 30‰S. In the following instars (5 to 10 in C. angulatus and 5 to 6 in C. altimanus), the longest intermolt period occurred at 21‰S, the shortest at 3‰S, in both species. Interspecific differences in response to low salinities may explain why C. angulatus occurs throughout a whole temperate coastal lagoon, whereas C. altimanus is restricted to its mouth. Received: 12 July 1998 / Accepted: 24 February 1999     

Production of glycine betaine and dimethylsulfoniopropionate in marine phytoplankton. I. Batch cultures

The quantitative significance of the nitrogenous compound glycine betaine (GBT) and its sulfur analog dimethylsulfoniopropionate (DMSP) to intracellular pools in marine phytoplankton is not well known. In a series of experiments conducted in August 1993, we measured these compounds, as well as total organic sulfur, carbon, and nitrogen, over the growth cycle in six isolates of marine phytoplankton, Amphidinium carterae Hulburt, Chrysochromulina sp. Lackey, Emiliania huxleyi Hay et Mohler, Prorocentrum minimum (Pavillard) Schiller, Skeletonema costatum (Greville) Cleve, and Tetraselmis sp. At the same time, we measured cellular concentrations of protein, amino acids, chlorophyll, and inorganic nutrients. All six species produced DMSP, while three produced GBT at lesser levels. In the Chrysochromulina sp. isolate, levels of GBT were greater than DMSP during the exponential phase of growth, but declined sharply as the culture approached stationary phase. This change appeared to coincide with the onset of nitrogen limitation. Other nitrogenous osmolytes were produced in five of the six species but in much smaller quantities. DMSP contributed significantly to cellular sulfur throughout the growth cycle although, in some algae, the proportion of dissolved DMSP increased substantially during stationary growth. When present, GBT formed a sizeable fraction of the cellular nitrogen only during exponential growth. A significant percentage (ca. 50%) of the organic nitrogen could not be accounted for even when cellular pools of protein, amino acids, inorganic nitrogen, and nitrogenous osmolytes were combined. Based on these experiments, there does not appear to be a reciprocal relationship between DMSP and GBT production, although GBT production does appear to be correlated with nitrogen availability. Received: 5 January 1998 / Accepted: 29 June 1999     

Carbon emission associated with respiration and calcification of nine gastropod species from the intertidal rocky shore of Western Europe

Intertidal rocky shores are characterized by vertical zonation that results from the interplay between environmental conditions, organism physiology, and species interactions. Metabolism of intertidal organisms is highly variable between species and it changes with vertical position along the intertidal gradient. The present study aimed to quantify the carbon metabolism of nine intertidal rocky shore gastropods, in order to clarify their respective roles in carbon production during emersion and immersion. The influences of monthly temperature variation and tidal level were tested for each species. Analyses were performed in the laboratory using the infrared gas analyzer method for measuring aerial respiration rates, and the dissolved inorganic carbon and total alkalinity technique for measuring aquatic respiration rate and calcification. Hourly carbon fluxes were calculated for the mean annual temperature of 13 °C measured in both air and underwater in the study area. Respiration rates were similar for emersion (8–25 μmol CO₂ g AFDW^?1 h^?1) and immersion (10–23 μmol DIC g AFDW^?1 h^?1). For all species, underwater respiration fluxes were more influenced by monthly temperature variation than by air fluxes, probably as an adaptation to the rapid changes occurring during emersion. Calcification was an important factor influencing annual carbon fluxes for all studied species; every species showed different calcification rates according to its size and position on the intertidal zone. Annual carbon emissions were calculated using the mean immersion/emersion time of each species. Intertidal gastropod carbon emission was primarily influenced by body biomass and their vertical position within the intertidal zone.     

Size-dependent behavior of tuna in an array of fish aggregating devices (FADs)

Several lines of evidence indicate that aggregations of yellowfin tuna associated with floating objects are more frequently composed of small animals than larger ones. Also, the diet of small yellowfin tuna caught at anchored fish aggregating devices (FADs) around Oahu, Hawaii, was found to shift quite rapidly when these fish reached approximately 50 cm FL. In order to test for ontogenetic changes in aggregation behavior, we tagged and released two distinct size classes of yellowfin tuna in an array of anchored FADs around Oahu, Hawaii. Twenty-four yellowfin tuna 30–39 cm FL and 16 yellowfin tuna 63–83 cm FL were tagged with acoustic transmitters and released near anchored FADs equipped with automated acoustic receivers. Fish in the smaller size class stayed about 2.5 times longer at individual FADs than the larger fish (mean 4.05 days vs. 1.65 days) and displayed larger horizontal movements within the array. However, the durations of unassociated phases, residence times in the entire FAD array, percentage of time spent associated with FADs and numbers of movements between FADs did not show any difference between the two size groups. The observed size-dependent behavior is discussed in terms of physiological abilities, diet segregation and anti-predator behavior.     

Mitochondrial genomic divergence in coelacanths (Latimeria): slow rate of evolution or recent speciation?

Dating the divergence between the two known living species of coelacanths has remained a difficult issue because of the very ancient origin of this lineage of fish, which is more closely related to tetrapods than to other fishes. We sequenced the complete mitochondrial genome of a recently captured individual of the Indonesian coelacanth in order to solve this issue. Using an approach based on loglinear models, we studied the molecular divergence between the two species of coelacanths and three other pairs of species, one that has diverged recently (Pan) and two that have diverged more distantly in the past. The loglinear models showed that the divergence between the two species of coelacanths is not significantly different from the two species of Pan. A detailed gene by gene analysis of the patterns of nucleotide and amino acid substitutions between these two pairs of species further supports the similarity of these divergences. On the other hand, a molecular dating analysis suggested a much older origin of the two coelacanth species (between 20 and 30 million years ago). We discuss the potential reasons for this discrepancy. The analysis of new individuals of the Indonesian coelacanth will certainly help to solve this issue.     

Management von schadstoffbelasteten Feinsedimenten in Bundeswasserstraßen

The Federal Institute of Hydrology has developed operating strategies in order to deal with dredged material within the scope of the Waterways and Shipping Administration. Sediments will be assessed based on certain quality parameters. The potential environmental impact at the source and relocation areas has to be evaluated in respect to ecological and economical issues. A coordinated sediment management plan for the Rhine River was commissioned. The most important contaminated sedimentation areas were identified, and special sedimentation areas were classified based on ecological impact or even risk. Proposals for economical and ecological strategies are discussed. Further developments for operational instructions dealing with sediments and dredged material in federal waterways are still being processed. The objectives of the river basin commissions as well as those of the stakeholders have to be met in an appropriate manner. In the framework of the analysis and impact of climate change on both sediment quantity and quality for optimizing sediment management, one or more dimensional hydraulic models will be applied. This will help gain a better insight into the understanding of contaminant transport in freshwater bodies.