CONTENTS & ABSTRACTS

In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Biology. Ecology

Volume 52 No. 2 June 2003

Special issue on Estonian coastal ecosystems:
state, processes, and development

Foreword; 83–84

Jonne Kotta

Benthos studies in the Estonian coastal sea during 1998–2001; 85–90

Jonne Kotta, Helen Orav-Kotta, Tiina Paalme, Ilmar Kotta, and

Henn Kukk

Abstract. This paper presents the recent findings related to experimental studies on benthos in the Estonian coastal sea. Pelagic–benthic coupling, interspecific competition for food, and plant–herbivore interactions are the three main topics. In the final section we present some ideas and directions that might serve as a base for further studies.

Key words: Baltic, competition, filter-feeding, macroalgal–herbivore interaction.

Water environment of Haapsalu Bay in retrospect (1975–2000); 91–111

Andres Jaanus

Abstract. A complex study with 12 series of measurements of physical, chemical, and biological parameters (temperature, salinity, O₂, Secchi depth, concentrations of tot-N, tot-P, NO₃-N, PO₄-P, chlorophyll a, and phytoplankton species composition and biomass) was carried out in Haapsalu Bay from March to October 2000. The results are compared with the studies in 1975–90. Calculations made for the total phosphorus vs. chlorophyll a concentrations in Haapsalu Bay in 2000 indicated a moderate positive correlation (r² = 0.36; n = 57), whereas the relationships between total nitrogen and chlorophyll a were weak (r² = 0.05; n = 57). The relative biomass of cyanobacteria increased continuously until October, reaching 93–94% of the total in the eastern part of the bay, while in the central and western parts their share varied in the range 39–88% and 4–43%, respectively. Proliferation of phytoplankton in late summer was common in the eastern bay also in the 1970s. The average total phytoplankton biomass values in August 1976–85, 1989, and 2000 were 0.1–1.8, 3.3, and 7.2 mg/L, whereas in eastern Haapsalu Bay they were 0.8–8.2, 1.8–12.9, and 5.2–13.3 mg/L, respectively.

Although the general succession of phytoplankton communities in Haapsalu Bay has not altered and the biomass values obtained in 2000 were similar to those calculated from the earlier samples, a simple increase in nutrient concentrations and algal biomass will bring about greater environmental risks connected with cyanobacteria.

Key words: coastal waters, nutrients, chlorophyll a, phytoplankton.

Estonian marine phytobenthos monitoring programme: preliminary results and future perspectives; 112–124

Georg Martin, Kaire Torn, Jonne Kotta, and Helen Orav-Kotta

Abstract. A phytobenthos monitoring programme has been carried out in Estonian coastal waters since 1995. Monitoring activities include six sea areas representing different sets of environmental conditions and anthropogenic impact. Methods used in the programme are based on internationally accepted techniques developed for the HELCOM COMBINE programme. During the observation period, the most important events described were the decline of the Fucus vesiculosus population in the northern Gulf of Riga and the Väinameri area, which has triggered several changes in phytobenthic communities. A new invertebrate species for Estonian coastal waters, Orchestia cavimana, was described in Küdema Bay in 1999. Its population has remained stable since then. In the nearest future the phytobenthos monitoring programme will be reorganized in connection with the implementation of EU WFD in Estonia and the need to include new sea areas in the monitoring activities.

Key words: phytobenthos, monitoring, Baltic Sea.

Comparison of net primary production rates of Pilayella littoralis (L.) Kjellm. and other dominating macroalgal species in Kõiguste Bay, northeastern Baltic Sea; 125–133

Tiina Paalme and Henn Kukk

Abstract. In situ net primary production measurements by means of the oxygen method were carried out with the ephemeral brown alga Pilayella littoralis, which dominates in the benthic vegetation in Kõiguste Bay, NE Baltic Sea. P. littoralis was characterized by relatively high net primary production rates (up to 13 mgO₂ gDW^–1 h^–1) obtained at 0.5 m depth. In comparison with the perennial algal species Fucus vesiculosus and Furcellaria lumbricalis, P. littoralis had markedly higher (2–5 times on average) net primary production rates. No great differences were found between the maximum net production rates measured for P. littoralis and the green alga Enteromorpha intestinalis. At the same time markedly higher net primary production rates (peak values reaching 26 mgO₂ gDW^–1 h^–1) compared to P. littoralis were measured for the opportunistic green algal species Cladophora glomerata.

Key words: net primary production rate, Pilayella littoralis, Cladophora glomerata, Enteromorpha intestinalis, Fucus vesiculosus, Furcellaria lumbricalis, Kõiguste Bay.

Changes in the distribution of charophyte species in enclosed seabays of western Estonia; 134–140

Kaire Torn and Georg Martin

Abstract. An overview of the distribution of charophytes in Matsalu, Haapsalu, and Rame bays, western Estonia, is given based on sampling carried out in 2001. Sampling was performed repeating stations investigated during previous investigations. Chara aspera was the most frequent charophyte in the three investigated bays. Compared to the former data, its distribution area has decreased in Matsalu Bay. Chara connivens was found for the first time in Matsalu Bay. No large-scale changes in charophyte distribution have occurred in Haapsalu Bay during recent decades. The distribution area of Chara tomentosa in Rame Bay has moved from east towards north.

Key words: charophytes, Matsalu Bay, Haapsalu Bay, Rame Bay.

Seasonal variations in the grazing of Gammarus oceanicus, Idotea baltica, and Palaemon adspersus on benthic macroalgae; 141–148

Helen Orav-Kotta and Jonne Kotta

Abstract. Grazing of Gammarus oceanicus, Idotea baltica, and Palaemon adspersus on benthic macroalgae was studied in situ using small enclosures in Kõiguste Bay, N Gulf of Riga. Pilayella littoralis was the prime diet of the studied invertebrates. When its biomass declined in the field, invertebrate grazing on Fucus vesiculosus increased. The highest grazing rates were shown by I. baltica followed by G. oceanicus and P. adspersus. In general invertebrate grazing was high in summer, moderate in autumn, and low in spring.

Key words: Baltic, Gammarus, grazing, Idotea, macrophytobenthos, Palaemon.

Macrozoobenthos assemblages in highly productive areas of the Estonian coastal sea; 149–165

Ilmar Kotta, Helen Orav-Kotta, and Jonne Kotta

Abstract. Bank slopes, fronts between different basins, river estuaries, and sites in the vicinity of municipal wastewater discharges are the most productive areas of the Estonian coastal sea. In these areas macrozoobenthos biomass exceeded significantly the values of the adjacent sea. The concentration of total nitrogen correlated positively with the benthic biomass. An increase in the species number of macrozoobenthos followed the decrease of nutrients in Pärnu Bay whereas the relationship was insignificant in other regions. When the water currents were slow a clear negative effect of the discharged effluents on the benthic communities was observed. Very high nutrient loads result in the accumulation of hydrogen sulphide in the sediment and the disappearance of benthos in these areas.

Key words: macrozoobenthos, nutrients, river estuaries, sewage discharge, upwelling.

Instructions to authors; 166–168