Scale-Specific Patterns of the Production of the Charophyte Chara aspera in the Brackish Baltic Sea: Linking Individual and Community Production and Biomass Growth

An understanding of the nature of scale-dependence in macroalgal production and to quantify how primary production is incorporated into autotrophic biomass requires an assessment of primary production at multiple scales. In this study we experimentally estimated seasonal variability in individual photosynthesis, community production and growth in biomass of the charophyte Chara aspera in the Baltic Sea together with the key environmental variables known to regulate the production of macroalgae. The experiments suggested that the production and growth of C. aspera was defined largely by light and temperature at all studied scales. However, the algal production at the same light levels was systematically lower at the community than an individual level, suggesting the importance of shelf-shading and below-ground processes in natural plant assemblages. Moreover, the observation scale also defined response types between the environment, plant production and growth. This implies that the patterns of variability of the production and growth of macrophytes should always be interpreted in the context of scale and any multiscale model development should involve experimental validation at all important scales.

Combined effects of salinity and temperature on grazing activity of invasive Gammarus tigrinus on charophytes

Charophytes are a refuge for zooplankton and stabilize sediments, but they are also a food source for various animal species (water birds, fishes, invertebrates). This grazing pressure may be an important factor prohibiting macrophyte re-colonization in eutrophic coastal waters. Especially the introduction of new species, like Gammarus tigrinus, into the Baltic Sea led to yet not understood changes in the food web. Furthermore, the occurrence of native and invasive species is determined by their capacity to acclimatize to changing abiotic factors. In this study we investigated the influence of temperature and salinity on the grazing pressure of Gammarus tigrinus on two charophyte species: Chara tomentosa and Chara aspera. The grazing experiments were conducted in a full factorial design with the factors salinity (3 – 13 PSU), temperature (5 – 30 °C), and charophyte species. Grazing rates were determined as mass deviation within 48 hours considering simultaneous growth of the charophytes. Experimental results were further used to determine gross macrophyte biomass within the ecosystem, using field data. Gammarids preferred C. aspera before C. tomentosa, but both were grazed within their respective growth optima. The potential grazing peak of 24 °C is not yet reached in these coastal waters. Furthermore, calculation of gross production revealed that macrophytes could show up to 60% and 15% more biomass without grazing in deeper light-limiting, and shallow, not light limited water depths, respectively. The impact of food web on coastal water restoration should therefore be equally considered, as the nutrient control.

НОВЫЕ НАХОДКИ ХАРОВЫХ ВОДОРОСЛЕЙ (CHARALES) НА ЕВРОПЕЙСКОМ СЕВЕРЕ РОССИИ, "Ботанический журнал"

В Архангельской, Вологодской и Ленинградской областях выявлена 41 новая популяция 9 видов харовых водорослей (Chara aspera, C. contraria, C. globularis, C. strigosa, C. subspinosa, C. virgata, C. vulgaris, Nitella flexilis, N. gracilis) и неидентифицированного представителя рода Nitella. Самое большое число новых местонахождений (10) установлено для реликтового вида C. strigosa, включенного в основной список Красной книги России. Этот вид впервые обнаружен в четырех административных районах Вологодской обл., его новые местонахождения выявлены также в Пинежском р-не Архангельской обл. Популяции C. strigosa приурочены к карстовым озерам и внутриболотным водоемам краевой зоны последнего оледенения и его деградации. В одном из болотных водоемов описана необычная форма роста C. strigosa с частично и полностью голыми листьями. Новые данные по остальным видам существенно детализируют их распространение в северных регионах Европейской России. Находки Chara subspinosa и C. vulgaris подтверждены новыми сборами в Архангельской обл. спустя чуть более чем 90 лет.

Charophytes of Insular Newfoundland II: Chara evoluta and Chara canescens

The rare Newfoundland disjuncts Chara evoluta and Chara canescens are compared morphologically, ecologically, and geographically. Although very similar morphologically, they can readily be distinguished by their monoecious/dioecious nature, cortical cell features and coronula size. Ecological differences are more subtle and difficult to quantify. In Newfoundland the two species are restricted to coastal saline lagoons in the southwest region of the Island, with C. evoluta exhibiting an association with Chara aspera. The flora and fauna of these unique habitats are poorly documented even though it is known that they are associated with other rare species including the Piping Plover and the Banded Killifish. Consideration of some degree of protection as special habitats within the provincial ecological reserve strategy is suggested. An updated key to all species of charophytes known to inhabit Newfoundland and Labrador is included, and a brief overview of their ecological distributions is provided.