ALBERT

Description: This study aimed to reveal the dynamics of inducible anti-herbivory traits in the brown seaweed Fucus vesiculosus, in response to grazing by the isopod Idotea baltica. As the molecular basis of defence induction in seaweeds is poorly understood, a transcriptomic approach was used to gain insight into cellular processes underlying defence induction and thus promote the mechanistic understanding of anti-herbivory responses in seaweeds. In a 27 day feeding-assayed induction experiment, temporal patterns of the induced anti-herbivory resistance of F. vesiculosus were assessed under laboratory conditions. Feeding assays were performed at three day intervals, using fresh and reconstituted food. Microarray hybridizations investigating the expression of genes 3 days before, as well as at the same time as, feeding assays revealed a decreased palatability of previously grazed F. vesiculosus pieces compared with non-grazed control pieces. Despite permanent exposure to grazers, F. vesiculosus palatability varied over time. Non-grazed F. vesiculosus pieces were significantly preferred to grazed pieces after 18 and again after 27 days of previous grazing, while their relative palatability for isopods was comparable at all other times during the experiment. Relative to controls, 562/402 genes were ≥ 1.5-fold up-/down-regulated in seaweed pieces that were grazed for 18 days, i.e. when induction of defences was detected in feeding assays. Massive reprogramming of the regulatory expression orchestra (translation, transcription) as well as up-regulation of genes involved in lipid and carbohydrate metabolism, intracellular trafficking, defence and stress response was found. At the same time, down-regulation of photosynthesis was observed in grazed seaweed pieces. This study suggests a high level of temporal variability in induced anti-herbivory traits of F. vesiculosus and reveals increased expression of genes with putative defensive functions in conjunction with the reallocation of resources from primary to secondary metabolism.

Description: This study aimed to reveal the dynamics of inducible anti-herbivory traits in the brown seaweed Fucus vesiculosus, in response to grazing by the isopod Idotea baltica. As the molecular basis of defence induction in seaweeds is poorly understood, a transcriptomic approach was used to gain insight into cellular processes underlying defence induction and thus promote the mechanistic understanding of anti-herbivory responses in seaweeds. In a 27 day feeding-assayed induction experiment, temporal patterns of the induced anti-herbivory resistance of F. vesiculosus were assessed under laboratory conditions. Feeding assays were performed at three day intervals, using fresh and reconstituted food. Microarray hybridizations investigating the expression of genes 3 days before, as well as at the same time as, feeding assays revealed a decreased palatability of previously grazed F. vesiculosus pieces compared with non-grazed control pieces. Despite permanent exposure to grazers, F. vesiculosus palatability varied over time. Non-grazed F. vesiculosus pieces were significantly preferred to grazed pieces after 18 and again after 27 days of previous grazing, while their relative palatability for isopods was comparable at all other times during the experiment. Relative to controls, 562/402 genes were ≥ 1.5-fold up-/down-regulated in seaweed pieces that were grazed for 18 days, i.e. when induction of defences was detected in feeding assays. Massive reprogramming of the regulatory expression orchestra (translation, transcription) as well as up-regulation of genes involved in lipid and carbohydrate metabolism, intracellular trafficking, defence and stress response was found. At the same time, down-regulation of photosynthesis was observed in grazed seaweed pieces. This study suggests a high level of temporal variability in induced anti-herbivory traits of F. vesiculosus and reveals increased expression of genes with putative defensive functions in conjunction with the reallocation of resources from primary to secondary metabolism.

Description: Combined genetic, morphological and ontogenetic observations show that the circumarctic boreal green algal macrophyte Kornmannia leptoderma has expanded its distribution range into the Baltic Sea, on a German coastal section of 220 km length. The species is also again (or still) established at its former extreme southern distribution limit in the North Sea, the German island of Helgoland, where it has not been detected during the last four decades. Macroscopic visible sporophytes of K. leptoderma are nowadays present in the Baltic Sea and at Helgoland from February to September, while they were in the past only detected from February to May at Helgoland. This capacity for formation of sporophytes in summer correlates with the circumstance that K. leptoderma from the Baltic Sea can complete its life cycle at 15°C while several studies conducted decades ago with material from Helgoland and from Pacific coasts consistently reported an inhibition of the algal gametogenesis at temperatures that exceed 12°C. Possibly K. leptoderma has undergone adaptations that facilitate its spread into warmer environments, unless the Kornmannia present in the Baltic Sea and on Helgoland today represents a newly introduced cryptic species.

Description: The Kiel Canal is one of the world’s most frequently used inland waterways and connects the SW Baltic Sea with the Wadden Sea. At the same time, the canal is a highly eutrophicated environment that is characterized by salinities that range from 3 to 16. This brackish character could make the Kiel Canal an important stepping stone for the introductions of species into the inner Baltic Sea. It could also hinder the identification of native and introduced species, given the fact that salinity sometimes severely affects algal morphology. Here we report on a survey of introduced and native seaweed species in the canal, focusing on the dominant groups, which are Fucales and Ulvales. Of the Fucales, the introduced species Fucus evanescens was detected nearly exclusively inside the canal, while Fucus vesiculosus dominated rockweed communities directly outside the sluice gates. Morphological analysis and genetic barcoding distinguished three species of Ulvales, Ulva linza, Ulva intestinalis and an unknown and possibly introduced species of the genus Blidingia. Species distributions and – in the case of U. intestinalis – branching patterns were clearly affected by salinity, while thallus sizes appeared to be affected by the specific eutrophication status of sites within the canal.

Description: Due to low salinity and lack of hard substrata, the Baltic Sea and Kattegat area and German and Danish North Sea coasts are characterized by a relatively low diversity of seaweeds. At the same time the areas are severely eutrophicated, which has caused extensive shifts in macroalgal communities toward opportunistic species. Unattached seaweed communities dominated by Furcellaria lumbricalis, which have been a resource for hydrocolloid production since the 1940s, have been severely reduced due to eutrophication and unsustainable harvesting and are nowadays only exploited commercially in Estonia. On the other hand, the biomass of opportunistic seaweeds of various red, green and brown algal genera has increased. They cause ecological problems, are a nuisance on many tourist beaches and constitute at the same time a potential bioresource that is so far only exploited to a limited extent for production of energy and fertilizer. Commercial seaweed cultivation is largely focused on Saccharina latissima and still very limited, but is currently being expanded as a compensation measure for sea-based fish aquaculture. Also land-based seaweed cultivation is primarily employed for recycling of nutrients in tank animal aquaculture, but in most cases so far only on an experimental scale.

Description: Supralittoral and shallow water seaweed communities are particularly exposed to impacts such as climate change and disturbance by humans. Therefore, their classification, the study of composition, and the monitoring of their structural changes are particularly important. A phytosociological survey of the supralittoral and upper sublittoral vegetation of the South West Baltic Sea revealed eight phytobenthos communities with two variants comprising 35 taxa of macrophytes (18 taxa of Chlorophyta, 13 taxa of Rhodophyta and four taxa of Phaeophyceae, Ochrophyta). Five of the eight communities were dominated by Ulvales (Ulva intestinalis, Kornmannia leptoderma, and three Blidingia species), the other three by Fucus vesiculosus. Most Fucus vesiculosus-dominated communities contained U. intestinalis and U. linza as subdominants. Only one of the communities had until now been described as an association ( Ulvetum intestinalis Feldman 1937). The syntaxonomic composition of the investigated vegetation includes both phytocenoses with the domination of green algae ( Ulvetum intestinalis Feldman 1937 and communities of Blidingia marginata, unidentified Blidingia spp. and Kornmannia leptoderma), as well as a number of communities dominated by Fucus vesiculosus. Mainly boreal Atlantic species and cosmopolitans make up the bulk of the species in these associations.