Botanica Marina 2019; 62(1): 1–2

Editorial

Hendrik Schubert and Angela Wulff Baltic algae https://doi.org/10.1515/bot-2018-0116 molecular tools often just raise confusion. Where, along a phenetic and often also genetic continuum to draw the This special issue is dedicated to Baltic algae. Which to line between ? many readers may raise the question “Baltic algae”? It’s fascinating how many answers will be given Issued in 2018? Isn’t the Baltic the region in which Lin- immediately before the unavoidable debate starts. And naeus lived? So everything has been known for centuries? there is still no commonly agreed answer yet; at the very Indeed, recent for most of the algal groups starts best, the opponents will come to a friendly agreement with Linnaeus’s classification and many taxa still bear the that they need more material and “objective” tools. So, epithets given by him. But the is also a geologi- e.g. friendly physiologists became involved too. And field cally young system with ongoing immigration processes – phycologists were getting annoyed by perpetual changes a “Sea of invaders” is the catchphrase ultimately coined of taxonomic rank – and especially by the disappearance by the perspective article of Leppäkoski et al. (2002). And of species – due to the combination of (ecologically mean- immigrating into a system characterized by steep gradi- ingful) morphotypes. ents of climatic, salinity and eutrophication conditions, And this is what this special issue is about. The Baltic species are shaped by strong habitat filters until their Sea is kind of an open laboratory for acclimation and acclimation potential is either exhausted or evolution adaptation processes and, consequently, it is studied by begins to dominate the process, leading to . the many institutions located at its shores. This became Evolution is indeed an ongoing process over billions very obvious in 2017 when the world community of phy- of years and the basic principles were discovered already cologists met in Szczecin, Poland for the 11th Interna- more than 150 years ago by Wallace and Darwin (Wallace tional Phycology Congress. After a well-attended special 1858, Darwin 1859). Examples of recent speciation are rare session on “Baltic algae”, covering two slots of brilliant and whether or not we are able to experimentally evolve presentations, the idea of presenting its highlights to a new species by the principles discovered by Wallace and broader community by a special issue of Botanica Marina Darwin still depends on the species concept applied. appeared. So, irrespective of its long history in nature as well as in The contributions ranged from cyanobacteria to mac- science, the terms “species” and “speciation” are still roalgae, and from molecular methods to in situ experiments raising debates and can turn distinguished scientists related to climate change. In this special issue, we present into emotional fighters for concepts – which is always big seven very interesting research papers on different aspects theatre, as probably first seen on stage in 1860 as the still of primary producers in the Baltic Sea. The members of the famous “Huxley-Wilberforce debate”. genus act as key species in the Baltic Sea, so it is A number of Linnaean algal species are described of no surprise that four papers deal with different species by material from the Baltic Sea – which means that of Fucus: Linnaeus, the relatively new the type represents morphologies from the edge of their species Fucus radicans L. Bergström & L. Kautsky, and the distribution ranges. And in phycology we are still bota- introduced species Fucus evanescens C. Agardh. Asexual nists, who agree to a species concept based on phenetic reproduction in F. radicans was the focus of the contribu- characters. By developing molecular tools we really tion by Schagerström and Salo, where temperature and could try to determine the vertical components, develop- light were shown to have an interactive effect on the re- ing it to a phylogenetic one and leaving ultimately Lin- attachment of fragments, further suggesting that the meta- naeus’s ground. We have not only accepted species with bolic balance of the fragment was a crucial feature for a sexual dimorphisms, but also heteromorphic life-cycles. successful re-attachment. Effects of substratum manipu- But phenotypic plasticity resulting from acclimation is lation and algal exudates on recruitment and survival of a completely different issue and, for immigrants with a F. vesiculosus were studied by Kautsky et al. In the same gene pool shaped by a series of strong habitat filters, the contribution, the authors address transplantation studies results of acclimation experiments, crossing attempts and where epiphytic load, light, grazing and type of substratum 2 H. Schubert and A. Wulff: Baltic algae were some of the factors important for a successful resto- if the cyanobacteria could have a competitive advantage ration of F. vesiculosus. At least 4–5 years were needed to over other phytoplankton groups in a future warmer Baltic reach reproductive age for F. vesiculosus in the Baltic Sea. Proper with increased carbon dioxide concentration. The Gradual adaptation of the introduced species F. evanes- results indicated a highly efficient resistance towards cens to low salinity was addressed by Romoth et al. where short-term (12 days) changes in abiotic factors by the it seemed that the vegetative stage was not limited by salin- natural Baltic Sea spring bloom community. ity, indicating that this species has the potential to spread The guest editors hope that the reader will find the further into the Baltic Sea. In the artificial Kiel Canal, contents interesting and inspiring. Steinhagen et al. explored the potential of the canal as, for example, a stepping stone for introduced species. F. eva- nescens was detected nearly exclusively inside the canal, References while F. vesiculosus dominated outside the sluice gates. Also, three Ulvales species, Ulva linza Linnaeus, Ulva Darwin, C. 1859. On the origin of species by means of natural selec- intestinalis ­Linnaeus and an unknown and possibly intro- tion, or, the preservation of favoured races in the struggle for life. John Murray, London. pp. 562. duced species of the genus Blidingia were found. Species Leppäkoski, E., S. Gollasch, P. Gruszka, H. Ojaveer, S. Olenin and V. distribution and branching patterns (U. intestinalis) were Panov. 2002. The Baltic – a sea of invaders. Can. J. Fish. Aquat. affected by salinity. Within the canal, specific eutrophi- Sci. 59: 1175–1188. cation status affected thallus size. Another introduced Wallace, A.R. 1858. On the tendency of varieties to depart indefi- species, the green alga Kornmannia leptoderma (Kjellman) nitely from the original type. Paper on natural selection sent by Bliding, raised the interest of Weinberger et al. The authors Wallace to Darwin. The Alfred Russel Wallace Page hosted by Western Kentucky University. http://people.wku.edu/charles. studied the recent expansion of the species and speculate smith/essays/Wallace_On_the_Tendency_of_Varieties.htm, that maybe the specimens found could represent a newly downloaded 13.12.2018. introduced cryptic species, expanding its temperature range. A different group of green algae, the charophytes, were in focus when Nowak and Schubert studied their Hendrik Schubert: Chair of Ecology, University of Rostock, genetic variability in the Baltic Sea area. But the Baltic Einsteinstr. 3, 18055 Rostock, Germany, e-mail: [email protected] Sea is not only inhabited by macroscopic algae. A micro- Angela Wulff: Department of Biological and Environmental Sciences, scopic spring bloom community inoculated with filamen- Göteborgs Universitet, Box 461, 405 30 Göteborg, Sweden, tous cyanobacteria was studied by Olofsson et al. to reveal e-mail: [email protected]