CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 49 No. 4 December 2000
Chironomid larvae (Diptera, Chironomidae) as indicators of water quality in Estonian streams; 307–316
Ado SEIRE and Peeter PALL
Abstract. Of the 184 taxa of chironomid larvae, recorded from Estonian running waters in 1987–97, a total of 26 proved to be related to water quality as measured by biological oxygen demand (BOD5). Out of these 26, the following 18 taxa of larval chironomids were identified at the species level: Paramerina cingulata (Tanypodinae); Diamesa carpatica, Pseudodiamesa nivosa (Diamesinae); Odontomesa fulva (Prodiamesinae); Acricotopus lucens, Corynoneura scutellata, Cricotopus sylvestris, Eukiefferiella brevicalcar, Nanocladius bicolor, Paracladius conversus, Synorthocladius semivirens, Tvetenia calvescens, T. discoloripes (Orthocladiinae); Chironomus cingulatus, Ch. plumosus, Glyptotendipes glaucus, G. gripekoveni, and Microtendipes rydalensis (Chironomini). Methodological problems related to division of indicator species between saprobic classes and to the arrangement of these species within saprobic classes are discussed considering presence/absence data.
Key words: chironomid larvae, BOD5, water quality, indicators, streams, Estonia.
Dynamics of copepods and fish larvae in Pärnu Bay (NE part of the Gulf of Riga) in the spring–summer period; 317–326
Mart SIMM and Evald OJAVEER
Abstract. Analysis of seasonal and long-term abundance of copepods and fish larvae during 1957–97 with reference to environmental conditions and predation is presented. The start of the seasonal mass development of copepods and fish larvae depended mainly on the temperature regime. In the warm years with low salinity the peak abundance of Eurytemora occurred significantly (about a month) earlier than in the cold years with higher salinity. In the cold years herring dominated among fish larvae and the abundance of fish larvae was higher than in warm years when gobies were the most numerous group of larvae. A rapid decrease in the abundance of Eurytemora in shallow Pärnu Bay in July may be due to predation from larval fish, mysids, and in recent years by the exotic cladoceran Cercopagis pengoi.
Key words: copepods, fish larvae, long-term changes, seasonal dynamics.
Changes in copper and cadmium content of male herring in relation to spawning; 327–334
Mart SIMM and Jonne KOTTA
Abstract. Copper and cadmium concentrations were determined in the muscles, liver, and gonads of male herring caught in the middle part of the Gulf of Finland, eastern Baltic Sea. Fish age did not affect the trace metal concentrations in muscles and gonads, whereas the concentrations were significantly higher in the liver of 5–7 year old fish as compared to 2–4 year old fish. The concentration of trace metals in herring gonads depended on their maturity stage and most pronounced changes occurred during spawning. The excretion of trace metals during spawning comprised 15–30% of the total content of copper and cadmium in the muscles, liver, and gonads of male herring. Relative amounts of copper and cadmium excreted during spawning were higher for 2–4 year old than 5–7 year old fish.
Key words: age, cadmium, copper, herring, maturity stage of gonads, Baltic Sea.
Heavy metal and organochlorine levels in coastal fishes from the Väike Väin Strait, western Estonia, in high summers of 1993–94; 335–343
Abstract. Heavy metals (Hg, Fe, Mn, Zn, Cu, Cd, Pb, Ni) and organochlorine compounds (HCHs, HCB, DDTs, PCBs) were analysed from muscle tissue and livers of Baltic herring (Clupea harengus membras L.), sprat (Sprattus sprattus balticus L.), smelt (Osmerus eperlanus L.), pike (Esox lucius L.), bleak (Alburnus alburnus L.), roach (Rutilus rutilus L.), ruffe (Gymnocephalus cernua L.), perch (Perca fluviatilis L.), and garpike (Belone belone L.) from the Väike Väin Strait during high summers of 1993–94. Mercury concentrations were higher in the muscle tissue than liver for both smelt and perch. For perch both these concentrations were higher than they were for smelt. In the muscle tissue of all predatory fishes (pike, perch, ruffe, garpike) the concentrations of mercury were higher than for the nonpredatory species (herring, sprat, smelt, bleak, roach). The concentrations of mercury were higher in the coastal inshore species (pike, perch, roach, smelt) than in open-sea fishes (garpike, herring, sprat). For metals other than mercury the values of manganese tended to be higher in smelt than in the two clupeids but for copper the opposite was observed. For cadmium and nickel the values measured for sprat, smelt, and bleak tended to be higher than they were from the same species from comparable Finnish coastal waters. The same is true for lead from herring, smelt, and bleak. For iron and zinc no such differences were observed. For both the organochlorine pesticides and PCBs, the concentrations were higher in the homogenates of migrating pelagic partly open-sea species (herring, sprat, garpike) than in the homogenates of less migrating coastal species (smelt, pike, perch). The food safety levels in Estonia or Finland for either metals or organochlorine compounds were exceeded in no cases.
Key words: heavy metals, organochlorine pesticides, PCBs, Baltic coastal fish, Väike Väin.
Content of benzo(a)pyrene in Estonian small lakes; 344–351
Ingeborg VELDRE and Svetlana KARLOVA
Abstract. The content of benzo(a)pyrene (BaP) in 62 small lakes was studied. It was found that the pollution with BaP was not high, although there was a wide variation in its concentrations. The mean value of BaP fluctuated from 0.11 to 9.30 ng L–1. The situation and economic use of the lakes played a certain part in the BaP content in their water. The study of seasonal variations of BaP in the small lakes did not establish distinct differences between the seasons. Only the urban and suburban lakes showed about an order of magnitude higher concentration of BaP in water in winter than in other seasons. The hydrobiological type (trophicity) of a lake did not influence the content of BaP in the lake water. The concentration of BaP in fish tissues depended on its amount in the lake water and on the fat content of the fish tissue.
Key words: lakes, water pollution, polycyclic aromatic hydrocarbons, benzo(a)pyrene, fish tissue.