Regier H.A., Lin P., Ing K.K. & Wichert G.A. 1996. Likely responses to climate change of fish associations in the Laurentian Great Lakes Basin: concepts, methods and findings. Boreal Env. Res. 1: 1–15.
Abstract
Turtola E. 1996. Peroxodisulphate digestion and filtration as sources of inaccuracy in determinations of total phosphorus and dissolved orthophosphate phosphorus in water samples containing suspended soil particles. Boreal Env. Res. 1: 17–26.
Abstract
Juntura E., Koponen J. & Alasaarela E. 1996. Modelling resuspension in the Bothnian Bay, Northern Baltic. Boreal Env. Res. 1: 27–35.
Abstract
Mäkelä T.P., Rahunen L., Petänen T., Oikari A.O.J. & Hyvärinen H. 1996. Seasonal fluctuation and impact of cage incubation on trace metals in the freshwater mussels Anodonta anatina and Pseudanodonta complanata. Boreal Env. Res. 1: 37–47.
Abstract
Nyman S., Eklund J. & Kyröläinen H. 1996. Eutrophication, acidification and abundance of Baltic herring larvae in the Vaasa archipelago, Gulf of Bothnia in 1983–1991. Boreal Env. Res. 1: 49–58.
Abstract
Turunen T. & Suuronen P. 1996. Hooking mortality of small brown trout and grayling in Finnish rivers catch and release fisheries. Boreal Env. Res. 1: 59–64.
Abstract
Tambets M., Muje P. & Saat T. 1996. In vitro maturation of whitefish, Coregonus lavaretus (L.), oocytes. Boreal Env. Res. 1: 65–69.
Abstract
Lehtinen K.-J., Mattsson K., Tana J. & Grotell C. 1996. Light energy as a cause of structural and functional variations in brackish water littoral mesocosms used in ecotoxicological research. Boreal Env. Res. 1: 71–83.
Abstract
Regier H.A., Lin P., Ing K.K. & Wichert G.A. 1996. Likely responses to climate change of fish associations in the Laurentian Great Lakes Basin: concepts, methods and findings. Boreal Env. Res. 1: 1–15.
How a water body’s temperature characteristics constrain organisms ecologically has been a continuing focus of interest in limnology and aquatic ecology for over a century now. A number of complementary scientific approaches are reviewed briefly. Progress in assessment of climate change is hampered by the still fragmentary and scattered scientific literature. A number of tentative generalizations are sketched. We expect that climate change of a type consistent with currently available scenarios will have severe consequences for Great Lakes fish and fisheries: in rivers that flow south, east or west and which contain isolated endemic species at the northerly edge of their ranges and which have no opportunity to migrate northwards; and where effects on the aquatic ecosystem of climate change interact synergistically and harmfully, as seems likely, with bad effects of other cultural stresses such as damming and nutrient loading.
Turtola E. 1996. Peroxodisulphate digestion and filtration as sources of inaccuracy in determinations of total phosphorus and dissolved orthophosphate phosphorus in water samples containing suspended soil particles. Boreal Env. Res. 1: 17–26.
Determinations of phosphorus fractions in water samples may be unreliable if an appreciable amount of phosphorus is attached to suspended soil particles. The inaccuracies in peroxodisulphate digestion for determination of total phosphorus were studied on the basis of surface runoff and drainflow samples from a clay soil. The results obtained with peroxodisulphate digestion tended to be lower than those obtained with a HF digestion method. The results of peroxodisulphate digestion indicated incomplete extraction of phosphorus, especially in samples with large amounts of suspended soil particles. More sulphuric acid, or dilution of the samples before the digestion, improved the results. Error in dissolved orthophosphate determination due to colloidal material was investigated by removing variable amounts of the material from samples before the analysis. The amounts of dissolved orthophosphate that were determined increased with the amount of suspended material in the filtrate, indicating release of orthophosphate from colloids. The described inaccuracies in total and orthophosphate phosphorus determinations may result in underestimation of the particulate phosphorus fraction.
Juntura E., Koponen J. & Alasaarela E. 1996. Modelling resuspension in the Bothnian Bay, Northern Baltic. Boreal Env. Res. 1: 27–35.
A resuspension model was added to a 3D flow and water quality model. The resuspension model consisted of a wind-wave model, an orbital current model and an erosion model. Erosion was modelled using the critical current velocity. The wave-induced orbital current was added to the advection current calculated by the 3D model. Sediment trap measurements were made in the Bothnian Bay near the Island of Hailuoto. The model results were compared with the field observations. The comparison revealed both discrepancies and agreements. Heavy storm conditions and differences in local depths between the study site and the coarse grid model are possible causes for the discrepancies. The model predicted correctly some erosion and accumulation areas.
Mäkelä T.P., Rahunen L., Petänen T., Oikari A.O.J. & Hyvärinen H. 1996. Seasonal fluctuation and impact of cage incubation on trace metals in the freshwater mussels Anodonta anatina and Pseudanodonta complanata. Boreal Env. Res. 1: 37–47.
Seasonal changes in dry weight based Cd, Cr, Cu, Fe, Hg, Ni and Zn concentrations were measured in the soft tissue of freshwater mussels Anodonta anatina and Pseudanodonta complanata. The animals were collected from uncontaminated Lake Höytiäinen, and from three areas of central Lake Saimaa, with varying anthropogenic impact. In addition, two transplantation experiments with A. anatina were carried out in Lake Saimaa. Heavy metal levels in the mussel soft tissue were low. Statistically significant seasonal fluctuation was found in the concentrations of Cd, Cr, Cu, Hg, and Ni in A. anatina. The apparent increase in Cd, Cr, Hg and Ni concentration in July was probably related to spawning. The two species differed in metal levels at different stages of their seasonal cycle. The effect of sex, size and sediment contact on trace metal concentrations was negligible for mussels of 60–80 mm shell length. Higher levels of Fe and Zn were, in general, found in P. complanata. Transplanted mussels did not have the same metal concentrations as natural populations but the order of metal levels in different areas in central Lake Saimaa was similar to native mussels. Therefore transplanted A. anatina can be used to indicate areas of differing metal bioavailability. Use of male mussels and sampling in autumn can be recommended.
Nyman S., Eklund J. & Kyröläinen H. 1996. Eutrophication, acidification and abundance of Baltic herring larvae in the Vaasa archipelago, Gulf of Bothnia in 1983–1991. Boreal Env. Res. 1: 49–58.
Surface water nitrogen and phosphorus concentration, pH and chlorophyll-a content were monitored at 28 stations in the Vaasa archipelago (63°05´N, 21°30´E) in June–August 1983–1991, and pH additionally during the spring runoff maximum. Herring larvae were sampled weekly or biweekly in May–August during the period. High levels of nutrients and chlorophyll-a were found in the innermost archipelago receiving non-point runoff load and municipal sewage load. Elevated nutrient and chlorophyll-a levels extend to the outer border of the archipelago. River water entering the area is acidified by acid sulphate soils, and pH values of 5 or lower were measured in spring each year in runoff and in the innermost bays. The areas affected by acid runoff have low levels of phosphorous and chlorophyll-a. Herring larvae densities were highest in the outer part of the study area, and there was a negative correlation between larval density and the chlorophyll-a content. It was concluded that the entire study area is to some extent eutrophicated by runoff and sewage nutrient load. Recurring acidity limits phytoplankton production in the innermost bays. Acidity or excessive eutrophication may preclude the utilization of the innermost bays for feeding by herring larvae.
Turunen T. & Suuronen P. 1996. Hooking mortality of small brown trout and grayling in Finnish rivers catch and release fisheries. Boreal Env. Res. 1: 59–64.
Experiments to evaluate post-capture hooking mortality caused by widely used flies and other angling-gear types for brown trout (Salmo trutta L.) and grayling (Thymallus thymallus (L.)) in catch and release fishing were conducted in four typical Finnish rivers. Most of the fish caught were smaller than the legal minimum size. The average total body length (± 95% confidence limit) of brown trout (n = 380) was 19.3 ± 0.4 cm and 30.4 ± 1.3 cm, respectively, in the two main research areas. The average length of grayling was 26.6 ± 1.1 cm (n = 60). Mortality was estimated by returning released fish into wire-cages that were held in the river. The duration of caging was usually 3 days. Only three (i.e. 1%) brown trout died. No mortality occurred among grayling. The most visible injury in dying brown trout was bleeding in the gills caused by hooking. Because hooking-mortality for these species was almost non-existent, no relation could be established between mortality and fish size, gear type, and water temperature. Potential factors for the low mortality rate in our study are the relative short playing times and careful handling of released fish. The low hooking mortality of brown trout and grayling supports the concept of catch and release fishing.
Tambets M., Muje P. & Saat T. 1996. In vitro maturation of whitefish, Coregonus lavaretus (L.), oocytes. Boreal Env. Res. 1: 65–69.
Ovarian fragments of whitefish, Coregonus lavaretus (L.), were incubated in medium 199 with Earle’s salts at 10°C in the presence of 17alpha-hydroxy-20beta-hydroxyprogesterone (1 µg ml–1) or salmon pituitary extract (10 µg ml–1) for 5 or 10 days. These hormones induced both cytoplasmic and nuclear maturation of 91–100% of oocytes within 3–4 days. However, ovulation in vitro was observed only from follicles stimulated to mature in vivo. Fusion of oil droplets in vitro was usually incomplete as compared with in vivo maturation.
Lehtinen K.-J., Mattsson K., Tana J. & Grotell C. 1996. Light energy as a cause of structural and functional variations in brackish water littoral mesocosms used in ecotoxicological research. Boreal Env. Res. 1: 71–83.
The significance of two vital ecosystem regulating factors, i.e. light and temperature, was studied in littoral brackish water mesocosms during a four month experiment. Conspicuous light energy-related structural and functional responses were observed in the mesocosms. Functionally, the horizontal transport of organic carbon increased with lower temperature and light conditions. Systems with lower temperature and less light adapted by increasing phytoplanktic production instead of periphytic growth. All systems seemed to be nitrogen limited. Sedimentation was lower in colder than in warmer systems. Colder systems contained less organic carbon in the sediment but only insignificantly less carbon was bound in the macroscopic organisms in these systems as compared with warmer systems. This indicates adaptatory mechanisms on the structural level, as observed by invertebrate and fish studies. Small sized Jaera spp. was favoured by less efficient system carbon binding capacity. Typical littoral species such as Gammarus spp. and Theodoxus fluviatilis were favoured by efficient carbon binding environments and higher temperature. Lower temperature favoured mollusc species such as Macoma baltica and Mytilus edulis. Fish fry were favoured by higher temperature at the individual level but population mortality was negatively affected. The results obtained show that mesocosms are sensitive systems that rapidly respond to external perturbations, including pollution. However, in order to separate responses caused by natural variability from those caused by pollution, it is important that both structure and function are measured.