Birds in the trophic web of Lake Esrom,Denmark

Using an extended method for calculating food consumption by diversified bird communities taking into account variability of diet, energy content and digestibility of different food items within a diet, it was possible to calculate the energy consumption of the bird community in eutrophic Lake Esrom. As the production of food items and energy flow in Lake Esrom have been well studied, it was possible to relate the bird community to the trophic web. Birds consumed approximately 20% of the annual macrophyte production (excluding roots and rhizomes), and 4% of the annual zoobenthos production. The annual consumption of fish by birds corresponded to 22% of the annual consumption by piscivorous fish measured in kJ, and was almost the same as the commercial fishery catch. However, the consumption of fish by birds consisted mainly of non-piscivorous fish, in contrast to the commercial catch. In Lake Esrom, the birds have a significant role in the energy flow of consumers within the ecosystem. This result indicates that bird communities should be included in future studies of lake ecology. Also, competition between fish and birds is potentially significant.     

Interactions between seagrasses and burrowing ghost shrimps and their influence on infaunal assemblages

The current study examined the direct interactions between intertidal seagrasses (Zosteraceae) and burrowing ghost shrimps (Callianassidae) and their influence on associated infaunal assemblages. Reciprocal transplant experiments conducted in two temperate regions revealed different interactions between both types of organism. In the U.S.A., seagrass prospered in all treatments, irrespective of the presence of ghost shrimp, whilst ghost shrimp declined in plots containing seagrass. In New Zealand, neither transplanted ghost shrimp nor seagrass became established in experimental plots, at the same time, neither type of organism appeared to be affected by the experimental addition of transplants. The differences in interactions between seagrass and ghost shrimp appeared to be related to seasonal differences in the timing of the transplant experiments and the pairing of particular ghost shrimp and seagrass species in each region. Infaunal assemblages showed distinct differences between seagrass and ghost shrimp treatments and reflected the dominant type of organism present. In treatments where transplanted seagrass or ghost shrimp became established, assemblage composition shifted in accordance with the type of transplanted organism. Differences in assemblage composition were characterised by higher relative abundances of discriminating taxa in treatments dominated by seagrass. The overall patterns of infaunal assemblage composition were correlated with a number of variables including the number of shoots, above-, below-ground seagrass biomass, % fines/sand, % total organic carbon, and sediment chlorophyll a. Findings from this study highlight the functional importance of intertidal seagrasses and burrowing ghost shrimps and reveal some of the ecological repercussions associated with changes in the distribution of these sympatric ecosystem engineers.     

Improving data deficiencies in length-weight relationships for fish species around an artificial breakwater and adjacent soft-bottom at the central coast of Peru

Long-term environmental monitoring studies includes morphometric data (length and weight) of aggregating fish species around this artificial structure and adjacent soft-bottom habitats. We used these data, obtained biannually (summer and spring) between 2012 and 2018, to estimate population parameters such as length-weight relationships (LWRs) for 28 species. Gender and ontogeny-based differences in LWR were determined in four species, while novel LWR information was generated for all other species.     

From twigs to landscapes – methods for studying ecological effects of forest ungulates

In recent decades considerable attention has been focused on plant-ungulate interactions at various spatial and temporal scales. The cascading effects following ungulate actions are also attracting increasing interest. Our knowledge of the effects of ungulates on plants, communities, landscapes and ecosystems is, therefore, growing. At the same time, shifts in ungulate populations (increases and decreases) in various forested parts of the world together with mounting interest in biodiversity issues have heightened management concerns about plant-ungulate interactions. This paper reviews methodologies commonly applied to the study of ungulate-induced effects at various scales. Non-experimental comparisons have long been used, while simulation and exclosure methods were developed decades ago. However, these methods have been progressively refined, the objectives of studies based on them have broadened, and the results obtained have increasingly highlighted the interactive and dynamic nature of plant-ungulate interactions. Recent research has exploited various new techniques, such as remote sensing, to gather and process data over larger spatial scales, while others, such as GIS and powerful modelling and statistical methods are opening up new ways to analyse data and present information. The nature, design and use of the various commonly used methods, as well as their potentials and limitations, are discussed.