Macroinvertebrates assemblages on reed beds, with special attention to Chironomidae (Diptera), in Mediterranean shallow lakes

Macroinvertebrates associated to reed-beds (Phragmites australis) in six shallow natural water bodies along the 220 km of coast of the Comunidad Valenciana (Spain) were studied. These sites were selected to reflect different trophic states, but also, and due to the natural variability of mediterranean wetlands, they greatly differ in salinity and hydroperiod. To unify the sampling, reed bed was chosen to provide data from a habitat common to all wetlands, including the most eutrophic ones where submerged macrophytes have disappeared due to water turbidity. Individual submerged stems of Phragmites australis were sampled along with the surrounding water. The animal density found refers to the available stem surface area for colonization. Forty-one taxa were recorded in total, finding Chironomidae to be the most important group, quantitatively and qualitatively. In freshwater sites it was observed an increase in macroinvertebrate's density at higher trophic states. Nevertheless each studied region had a different fauna. The PCA analysis with macroinvertebrate groups distinguished three types of environment: freshwaters (characterized by swimming insect larvae, collectors and predators, oligochaetes and Orthocladiinae), saline waters (characterized by crustaceans and Chironominae) and the spring pool, which shares both taxa. Chironomids were paid special attention for being the most abundant. A DCA analysis based on the relative abundance of Chironomids reveals salinity as the main characteristic responsible for its distribution, but trophic state and hydrological regime were also shown to be important factors.Se han estudiado los macroinvertebrados asociados a la vegetación de carrizo (Phragmites australis) en seis lagunas someras a lo largo de los 220 km de costa de la Comunidad Valenciana (España). Las lagunas se eligieron de manera que se contemplasen diferentes estados tróficos, pero además y reflejando la natural variabilidad de los humedales mediterráneos, presentan importantes diferencias en cuanto al hidroperiodo y la salinidad. Para unificar el muestreo, se eligió el carrizo por ser un elemento común en todos los humedales, incluso los más eutróficos en los que los macrófitos sumergidos han desaparecido debido a la turbidez del agua. Para cada muestra se toma individualmente la parte sumergida de una planta de Phragmites australis junto con el agua circundante. La densidad de animales encontrados se refiere a superficie colonizable del tallo de la planta. En total se han encontrado 41 taxones, siendo Chironomiidae el grupo más importante tanto cuantitativa como cualitativamente. En las lagunas de agua dulce, se observó un aumento de la densidad de macroinvertebrados en los niveles tróficos mayores. Sin embargo cada zona de estudio tiene una fauna diferente. El análisis PCA de los grupos de macroinvertebrados diferencia tres tipos de ambientes: aguas dulces (caracterizados por larvas nadadoras de insectos recolectores y depredadores, oligoquetos y orthocladinos), aguas salobres (caracterizadas por la presencia de crustáceos y Chironomiinae) y el "ullal" o surgencia de agua que comparte taxones de los dos grupos anteriores. Se ha prestado especial atención al grupo de quironómidos por ser los más abundantes. Un análisis DCA basado en la abundancia relativa de las especies de quironómidos, muestra la salinidad como la principal característica responsable de su distribución, siendo luego el estado trófico y el régimen hidrológico factores también importantes

Epiphytic metazoans on emergent macrophytes in oxbow lakes of the Krapina River, Croatia: differences related to plant species and limnological conditions

This study investigated the structure of the epiphytic metazoans on emerged macrophytes in the littoral zone of two oxbow lakes with different trophic levels. Differences in the diversity and density of the epiphytic metazoans were analyzed in relation to plant architecture (simple or complex stems), food resources (algae and detritus) and water characteristics (transparency and derived trophic state index). Asignificant negative correlation was found between detritus on plants as food resource, and diversity and density of epiphytic metazoans, indicating grazing of microphagous species. Rotifers dominated in diversity and density in the epiphyton on all habitats. Total density of metazoans, rotifers and copepods in epiphyton were significantly higher on Mentha in mesotrophic lake than on Iris in a eutrophic lake.We presume that macrophyte belt width and trophic state governed biotic interactions and consequently epiphytic assemblages more strongly than macrophyte architecture. However, a Mentha habitat showed a slightly higher density and diversity of epiphytic metazoans in relation to Iris at the same site, but these differences were not significant

Ecosystem of the Polish part of the Vistula Lagoon from the perspective of alternative stable states concept, with implications for management issues

Summary: The alternative stable states concept finds broad application in reference to both terrestrial and aquatic ecosystems. For some reason, attempts to implement the concept to explain processes observed in estuaries and Baltic lagoons are very rare. Based on information included in publications issued over the last 60 years, three co-existing states were designated within the strongly elongated basin the Vistula Lagoon, namely: phytoplankton-dominated (Middle Basin), macrophyte-dominated (Elbląg Bay), and transition state balancing between the two former ones (West Basin). Regions of the lagoon representing such states are similar in terms of nutrient concentrations, but they considerably differ in terms of: exposure to wind and wave action, salinity, anthropogenic impact, and multi-level top-down regulations. The paper discusses the role of such drivers, responsible for both the maintenance of a given state, and the past transition into the present alternative state. Moreover, it presents chances for the improvement of the situation, as well as threats which can undermine them. Keywords: Baltic Sea, Coastal management, Regime shift, Food-web interactions, Driver

Three-dimensional microdistribution of

Despite the worldwide distribution and ecological importance of Chironomus larvae in both freshwater and brackish water ecosystems, patterns of their spatial distribution have been rarely studied. This study was conducted in summer, spring and autumn (2010–2011) in the deep-water zone of the polymictic, strongly eutrophic Vistula Lagoon. Its objective was to test whether temporal changes in density of the larvae affect their horizontal microdistribution and burrowing depth. Horizontal distribution, as inferred from indices of dispersion and patchiness, was density-dependent. The larvae spread more regularly with increasing density. The decreased density was associated with an increase in clustered distribution. The larvae burrowed into sediments up to a depth of 25 cm. The maximum burrowing depth positively correlated with total density, but also depended on the size of the larvae. The smallest individuals (<10 mm) did not occur deeper than 5 cm. Larger larvae were encountered throughout the sediment profile. The largest larvae did not always burrow the deepest. In spring before pupation, the larvae gathered below the sediment surface.The paper focuses on a crucial and overlooked aspect of the ecology of chironomid larvae. Their more regularly distribution was associated with seasonally increased density, and a clustered one with decreased density. The maximum burrowing depth (up to 25 cm) positively correlated with total density, but also depended on the size of the larvae