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Charophytes in the estuarine Curonian Lagoon: Have the changes in diversity, abundance and distribution occurred since the late 1940s?

Sinkevičienė Z., Bučas M., Ilginė R., Vaičiūtė D., Kataržytė M., Petkuvienė J.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 2

186--198

EN

The results of the recent (2014-2015) inventory and three historical datasets (1949-1959, 1960-1980 and 1997-2007) were analyzed in order to track the long-term changes of charophytes in the largest estuarine lagoon of the Baltic Sea. The present species composition of charophytes in the estuarine part of the Curonian Lagoon consisted of 7 species, including tolerant to salinity (Chara aspera, C. contraria, C. globularis and Nitellopsis obtusa) and typical brackish-water species (Chara baltica, C. canescens and Tolypella nidifica). The highest congruence of species was between the 1997-2007 and 2014-2015 datasets, which covered respectively eutrophication and post-eutrophication periods. The 1949-1959 dataset (closest to the reference conditions) differed by the absence of typical brackish-water species. The 1960-1980 dataset (the major period of eutrophication) was relatively poor in study sites and species. During the last 6 decades, only tolerant to salinity freshwater species were constant and abundant; only Nitella mucronata can be considered as extinct. Recently, C. contraria became dominant and widespread. The changes in the charophyte species composition, abundance and distribution can be explained by different intensity of surveys and/or density of study sites, but also by the increased exposure to brackish waters since 1980s and/or recently reduced effect of eutrophication.

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Microorganisms associated with charophytes under different salinity conditions

Kataržytė M., Vaičiūtė D., Bučas M., Gyraitė G., Petkuvienė J.

Oceanologia

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2017

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No. 59 (2)

177--186

EN

Microorganisms associated with aquatic macrophytes can in various ways interact with a plant and influence its activity and vice versa. A low-salinity intrusion into freshwater environment can affect plant-microorganism interactions. In this study, effects of different salinity conditions on the abundance and community composition of associated microorganisms with charophytes in the Curonian Lagoon were assessed. From the results, we found that short term salinity changes affected the abundance of bacteria and fungi associated with charophytes, whereas no response was reflected in the taxa composition of fungi, showing that other factors could be of more importance. The increased fungi abundances and different fungi composition in August in comparison to June was probably related to senescence process of aquatic vegetation. 8 fungi taxa were isolated and identified in association with charophytes, while higher diversity was revealed by DGGE technique.

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Baltic herring (Clupea harengus membras) spawning grounds on the Lithuanian coast: current status and shaping factors

Šaškov A., Šiaulys A., Bučas M., Daunys D.

Oceanologia

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2014

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No. 56 (4)

789--804

EN

During the 2009 and 2010 seasons Baltic herring (Clupea harengus membras L.) spawning grounds were investigated by SCUBA divers off the Lithuanian Baltic Sea coast. The most important spawning substrate was a hard bottom overgrown with red algae Furcellaria lumbricalis, but only 32.8% of potentially suitable spawning locations had herring eggs. Bottom geomorphological analysis using multibeam bathymetry revealed that the distribution of spawning beds is not random, but is determined rather by small-scale geomorphological features. The majority of the detected spawning locations were on local elevations characterised by 2.4±1.1 m depth differences and 4.8±1.8 slopes.

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Mapping an ecosystem service: A quantitative approach to derive fish feeding ground maps

Šiaulys A., Daunys D., Bučas M., Bacevičius E.

Oceanologia

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2012

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No. 54 (3)

491-505

EN

This study presents a quantitative approach to mapping benthophagous fish feeding grounds. This approach combines the spatial biomass distribution of benthic prey items and their importance for the diets of predators. A point based biomass data of macrozoobenthos together with a set of environmental factors was used to develop Random Forests models that produce continuous biomass distribution layers for individual prey species. Depending on the diet composition and the importance of prey for fish feeding, these layers are overlaid and an integrated GIS map of the seabed showing the quality of feeding grounds is generated. These maps provide a useful basis for conservation and marine spatial planning. In addition, this method could be applied to the mapping of resources used by other benthophagous organisms. The method is presented using the example of three common Baltic fish species: cod, flounder and viviparous eelpout.

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Recent distribution and stock assessment of the red alga Furcellaria lumbricalis on an exposed Baltic Sea coast: combined use of field survey and modelling methods

Bučas M., Daunys D., Olenin S.

Oceanologia

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2009

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No. 51 (3)

341-359

EN

Recent results of field studies on the exposed coast of Lithuania were used to model the area occupied by the red alga Furcellaria lumbricalis using the Natural Neighbor interpolation technique, while linear regression was applied to estimate the species' standing stock. The area covered by F. lumbricalis extended for 26 km along the coast between depths of 1 and 15 m. The maximum species cover in the study area ranged between 4 and 10 m depth, which is one of the widest in the Baltic Sea. The modelled area of F. lumbricalis covered 35 š 11 km2 with a total biomass of 7554 š 3813 t.