The short-term stimulation of production, due to marine-derived nutrients (MDN) from spawning salmon, is well documented for certain trophic levels in stream communities (e.g., algae and insect biomass). The effect of these nutrients on the stream ecosystem as a whole, however, remains unclear especially later in the year. Trichopterans have been shown to feed on salmon and other fish carcasses and there is evidence for greater growth rates in the presence of salmon tissue. To address the question of long-term MDN subsidy on trichopterans, we investigated the growth of three limnephilid caddisflies in the spring in the Harris River on Prince of Wales Island, Southeast Alaska. The Harris River has a natural waterfall barrier to salmon and receives large runs of pink (O. gorbuscha) and chum (O. keta) salmon each fall. We selected two shredding caddisflies (Onocosmoecus unicolor) and (Psychoglypha spp.) and one facultative scraper, (Dicosmoecus atripes) for our study. We had two objectives : 1) compare the spring growth of larval caddisflies in a stream section that receives a large autumn run of salmon with their growth in a stream section that is blocked from receiving salmon (due to an impassable waterfall), and 2) compare the growth of shredders with that of a facultative scraper when provided either leaves or biofilm on rocks as food.

Insects were placed in growth boxes in May 2001 with either conditioned alder leaves or stream rocks as food sources. The boxes were placed along with temperature loggers in both the salmon (below the waterfall) and non-salmon (above the waterfall) reaches. The boxes were removed 40 days later. In-stream samples were taken of each caddisfly initially and at the end of the experiment to establish in-stream growth versus growth in the boxes. All larvae were coaxed from their cases, measured for total wet length, dried and weighed. Only D. atripes and Psychoglypha spp. were growing during our experiment and both showed very high relative growth rates in the Harris River. Psychoglypha spp. and O. unicolor were both significantly larger in the leaf boxes and D. atripes was significantly larger in the rock boxes. Both D. atripes and Psychoglypha spp. had significantly greater relative growth rates between food types (on biofilm on rocks and leaves respectively). These results support the notion that D. atripes are most likely facultative scrapers at least in their first year of growth. None of these caddisflies showed differences in their final mean weights or relative growth rates between stream sections, suggesting no effect of MDN on their spring growth in the Harris River. Further research on caddisfly communities in the fall and winter will help clarify if MDN has an influence on the abundance and life history of these species closer to the salmon run. This study questions the long-term influence of MDN on stream communities, particularly those populations that do most of their production in the spring, months after salmon carcasses are no longer visible.

Corbicula fluminea populations were sampled annually from 1997 to 2000 at the beginning of the autumn, i.e. at the end of the reproduction period, at 14 sites along the Saône and Rhône rivers. Recruitment in the upper reach of these rivers was generally high. Conversely, the observation of other sectors revealed generally low or no production of juveniles, missing cohorts and major year to year variations in population structure. Nevertheless, no dramatic fall in population density was observed during the surveyed four years. This suggests that the longevity of the Corbicula populations of the Saône and Rhône rivers is ensured to a great extent by the drifting of individuals from the upper course of these rivers and their tributaries. Two possible causes are put forward to explain the low recruitment observed : low production of phytoplankton that prevents adults from constituting sufficient energy reserves to ensure the full development of larvae, and/or toxic contamination, which inhibits the development of phytoplankton and it is lethal for pediveligers.

Decomposition of dry and fresh willow leaves and the dynamics of invertebrates during this decomposition were followed in upstream and downstream Oued Zegzel, Eastern Morocco. A seasonal comparison of the two studied sites stressed the importance of the structure of the benthic fauna in the process of decomposition. The rate of decomposition was faster in summer, following an increase in the biomass of invertebrates. It was slower in winter, when abundances of Chironomidae reached their maxima. The decomposition of willow leaves was faster upstream, where invertebrates biomass was greater. The artificial drying of leaves before their immersion had a positive effect on the activity of invertebrates. Whereas Melanopsis praemorsa preferred the dry leaves during the four seasons in upstream Zegzel, the preference of Hydropsyche maroccana for the fresh leaves in the downstream station changed according to the season. The seasonal variation of leaves quality seems to especially influence invertebrate colonisation, and thereafter the decomposition process in downstream Zegzel.

This study investigated major pigment patterns of 8 cyanoprokaryota, 2 rhodophytes and 2 cryptomonads isolated from freshwater ecosystems. Analysis was done by means of HPLC. The method, historically adapted to marine phytoplankton, was modified to accommodate limnic algae. Quantitative results obtained in this study can be used for phytoplankton quantification techniques based on pigment patterns. Compared to marine strains, the studied freshwater cyanoprokaryote strains reveal a more complex pigment pattern, including myxoxanthophyll, canthaxanthin and echinenone. Cryptophyta possess the two acetylenic class-specific marker compounds allo- and monadoxanthin, crocoxanthin was not detectable. Rhodophytes show a simple pigment pattern similar to marine species. Previous reports as to the existence of chlorophyll-d could not be confirmed (historical reports probably refer to an artefact of preparation). Besides methodological considerations, the phenomenon of complementary chromatic adaptation is discussed briefly.

Major pigment patterns of 18 chlorophyceae, 7 charales, 4 euglenophyta, and 2 dinophyta isolated from freshwater ecosystems, were investigated by means of HPLC. In this study, quantitative results are presented, too, which are capable for phytoplankton quantification techniques based on pigment patterns. Chlorophyceae revealed a pattern similar to that of higher plants, but in some strains, loroxanthin as well as α-carotene were present. In charophytes, except for vegetative specimens of Chara tomentosa, γ-carotene was detected in antheridia only. Among investigated freshwater euglenophytes diadinoxanthin was the major carotenoid, with neoxanthin and ß-carotene present in minor amounts. Besides chlorophylls-a and -c, dinophytes contained high quantities of peridinin, whereas fucoxanthin was absent. An unknown component eluting just before violaxanthin showed a spectrum reminding of peridinin.

Tetrazolium reduction and enzyme kinetics were examined to estimate the ETS activity of decomposing reed (Phragmites australis /Cav./ Trin. ex Steud.) rhizome to collect information on the activity of microbial decomposers. Optimal incubation time was determined at 22 °C. For complete enzyme extraction, 4-6 min. of homogenization was necessary. The main substrates of the enzymatic reaction were NADH and NADPH. The reaction was fastest when 2-(-p-iodophenyl)-3-(-p-nitrophenyl)-5-phenyl tetrazolium chloride (INT ; 0.8 mM), NADPH (0.25 mM) and NADH (1.7 mM) were applied simultaneously. The optimal incubation time should be less than 20 minutes. The pH optimum of the enzyme reaction is 8.0-8.4. ETS activity of decomposing reed rhizome can be used to estimate potentially the oxygen consumption of microorganisms involved in decomposition and, indirectly, the rate of decomposition.

This paper focuses on relationships between the North Atlantic Oscillation Index (NAO) and the ice conditions in coastal lakes (Jamno, Bukowo, Gardno and Lebsko) of the southern Baltic Sea. The data on ice conditions included : date of first ice appearance (F), date of last ice disappearance (D), number of days with ice (N), length of the ice season (in days ; S) and maximum ice thickness (H) during the given winter. The period examined covers the winters from 1960/61 to 1999/2000. The monthly values of the NAO index for the same period were applied in accordance with Jones et al. (1997). Correlation and regression analysis methods were applied to determine and study the relationships between NAO (independent variable) and the parameters of ice conditions (dependent variables). The strongest relationships, with a linear correlation coefficient exceeding - 0.80, were obtained for the date of the last ice disappearance (D) in Lebsko Lake (- 0.853) and Gardno Lake (- 0.828) for the January March period. In contrast, the relationships between the NAO index and the date of first ice appearance (F) are much weaker. They are statistically significant only in November and early winter (Nov.-Dec., Nov.-Jan.). The correlation coefficients in the coastal lakes of the Southern Baltic Sea coasts generally increase eastwards, a phenomenon related to the severity of winters and to the increasing continuity of ice phenomena during a given winter in this direction.