Non-indigenous species in Northern Europe and the Great Lakes-St. Lawrence River: the importance of geographic origin

Ecosystems all over the world are continuously invaded by new species, which become non-indigenous species (NIS) in the new location. Increasing ship traffic raises the chances for relocations of aquatic species to new regions since shipping is identified as the major transport vector. This dissertation focused on NIS from the North and Baltic Seas and the Great Lakes-St. Lawrence River region. Both regions are connected via frequent transatlantic ship traffic and highly invaded by well documented NIS. Comparing origins of established aquatic NIS in both regions revealed that the systems are highly invaded by species that originate from the Ponto-Caspian region which consists of the Black, Azov and Caspian Seas. Further, observed numbers of established NIS in the two regions were compared to expected numbers of NIS from major donor regions based on the available species pool from donor regions, frequency of shipping transit, and an environmental match between donor and recipient regions. It was discovered that Ponto-Caspian taxa colonized both regions in much higher numbers than expected (Chapter I). A comprehensive study of seven life history traits for each NIS in both regions revealed that certain traits such as dormancy, regeneration and r-strategy are potentially beneficial for invasion success (Chapter II). Global warming as part of a predicted climate change might become a hazard for the survival of some native species, especially in coastal zones which is the habitat of amphipods. Environmental tolerance towards changing temperatures was investigated in three amphipod species and the results revealed that the Ponto-Caspian species Pontogammarus maeoticus has a higher temperature tolerance, especially towards rising temperatures, compared to Gammarus oceanicus, which is native to the Baltic Sea (Chapter III). Hence, with predicted global warming Ponto-Caspian species might be able to compete against native species in the Baltic Sea

Life history traits of aquatic non-indigenous species: freshwater vs. marine habitats

One of the most dominant concepts in invasion ecology is the stage-based invasion model, consisting of transport, introduction, establishment and spread. Many species fail at one of the stages, with propagule pressure (i.e. number of introduced individuals) identified as a principal factor affecting establishment success. Population characteristics such as phenotypic plasticity and beneficial life history traits may facilitate successful transition of species through different stages of the process; however, studies on the latter are not so common and most of those studies focus on terrestrial taxa. In this study, we hypothesized seven life history traits that may be beneficial for invasion success of aquatic species, and determined those traits for established non-indigenous species (NIS) in the North and Baltic Seas (i.e. marine environment) and Great Lakes-St. Lawrence River regions (i.e. freshwater environment). This is the first study that examined certain life history traits of all NIS established in particular regions, as well as compared those traits between marine and freshwater habitats. Our study determined some differences in life history traits between NIS in the marine and freshwater habitats. Those differences were connected to different taxonomic groups that were dominant NIS in these two types of habitats. Furthermore, species originating from different donor regions had also different life history traits. The majority of NIS in both regions were r-strategists. There was a significantly higher number of NIS that were able to reproduce both asexually and sexually and to produce dormant stages in the freshwater than in marine habitat. Finally, as r-strategy, asexual reproduction and dormancy were dominant traits of NIS in the freshwater habitat, freshwater ecosystems may be under greater invasion risk than marine ones, as those traits reduce both demographic and environmental stochasticity during the invasion process

Importance of geographic origin for invasion success: A case study of the North and Baltic Seas versus the Great Lakes-St. Lawrence River region

Recently, several studies indicated that species from the Ponto-Caspian region may be evolutionarily predisposed to become nonindigenous species (NIS); however, origin of NIS established in different regions has rarely been compared to confirm these statements. More importantly, if species from certain area/s are proven to be better colonizers, management strategies to control transport vectors coming from those areas must be more stringent, as prevention of new introductions is a cheaper and more effective strategy than eradication or control of established NIS populations. To determine whether species evolved in certain areas have inherent advantages over other species in colonizing new habitats, we explored NIS established in the North and Baltic Seas and Great Lakes–St. Lawrence River regions—two areas intensively studied in concern to NIS, highly invaded by Ponto-Caspian species and with different salinity patterns (marine vs. freshwater). We compared observed numbers of NIS in these two regions to expected numbers of NIS from major donor regions. The expected numbers were calculated based on the available species pool from donor regions, frequency of shipping transit, and an environmental match between donor and recipient regions. A total of 281 NIS established in the North and Baltic Seas and 188 in the Great Lakes–St. Lawrence River. Ponto-Caspian taxa colonized both types of habitats, saltwater areas of the North and Baltic Seas and freshwater of the Great Lakes–St. Lawrence River, in much higher numbers than expected. Propagule pressure (i.e., number of introduced individuals or introduction effort) is of great importance for establishment success of NIS; however in our study, either shipping vector or environmental match between regions did not clarify the high numbers of Ponto-Caspian taxa in our study areas. Although we cannot exclude the influence of other transport vectors, our findings suggest that the origin of the species plays an important role for the predisposition of successful invaders

Energy and nitrogenous waste from glutamate/glutamine catabolism facilitates acute osmotic adjustment in non-neuroectodermal branchial cells

Maintenance of homeostasis is one of the most important physiological responses for animals upon osmotic perturbations. Ionocytes of branchial epithelia are the major cell types responsible for active ion transport, which is mediated by energy-consuming ion pumps (e.g., Na+-K+-ATPase, NKA) and secondary active transporters. Consequently, in addition to osmolyte adjustments, sufficient and immediate energy replenishment is essenttableial for acclimation to osmotic changes. In this study, we propose that glutamate/glutamine catabolism and trans-epithelial transport of nitrogenous waste may aid euryhaline teleosts Japanese medaka (Oryzias latipes) during acclimation to osmotic changes. Glutamate family amino acid contents in gills were increased by hyperosmotic challenge along an acclimation period of 72 hours. This change in amino acids was accompanied by a stimulation of putative glutamate/glutamine transporters (Eaats, Sat) and synthesis enzymes (Gls, Glul) that participate in regulating glutamate/glutamine cycling in branchial epithelia during acclimation to hyperosmotic conditions. In situ hybridization of glutaminase and glutamine synthetase in combination with immunocytochemistry demonstrate a partial colocalization of olgls1a and olgls2 but not olglul with Na+/K+-ATPase-rich ionocytes. Also for the glutamate and glutamine transporters colocalization with ionocytes was found for oleaat1, oleaat3, and olslc38a4, but not oleaat2. Morpholino knock-down of Sat decreased Na+ flux from the larval epithelium, demonstrating the importance of glutamate/glutamine transport in osmotic regulation. In addition to its role as an energy substrate, glutamate deamination produces NH4+, which may contribute to osmolyte production; genes encoding components of the urea production cycle, including carbamoyl phosphate synthetase (CPS) and ornithine transcarbamylase (OTC), were upregulated under hyperosmotic challenges. Based on these findings the present work demonstrates that the glutamate/glutamine cycle and subsequent transepithelial transport of nitrogenous waste in branchial epithelia represents an essential component for the maintenance of ionic homeostasis under a hyperosmotic challenge

Salinity dependence of recruitment success of the sea star Asterias rubens in the brackish western Baltic Sea

Salinity strongly influences development and distribution of the sea star Asterias rubens. In Kiel Fjord, located in the western Baltic Sea, A. rubens is the only echinoderm species and one of the main benthic predators controlling blue mussel (Mytilus edulis) abundance. However, Kiel Fjord with an average salinity of about 15 is located close to the eastern distribution boundary of A. rubens in the Baltic Sea. In this study, we combined field and laboratory investigations to test whether the salinity of Kiel Fjord is high enough to enable successful development of A. rubens. Sea star eggs were fertilized in vitro, and development was monitored in the laboratory at four salinities (9, 12, 15 and 18) for 10 weeks. At a salinity of 9, development ceased prior to the blastula stage. At a salinity of 12, no larvae reached metamorphosis. At higher salinities, larvae developed normally and metamorphosed into juvenile sea stars. Abundances of A. rubens larvae and settled juveniles were also observed in Kiel Fjord and correlated to salinity values measured from March until June during 6 years (2005–2010). Results revealed high A. rubens settlement rates only in 2009, the year when salinity was the highest and least variable during the period of spawning and larval development. It appears that only years with high and stable salinities permit recruitment of A. rubens in Kiel Fjord. Projected desalination of the Baltic Sea could shift the distribution of A. rubens in the western Baltic Sea north-westwards and may lead to local extinction of a keystone species of the benthic ecosystem

Food Supply and Seawater pCO2 Impact Calcification and Internal Shell Dissolution in the Blue Mussel Mytilus edulis

Progressive ocean acidification due to anthropogenic CO2 emissions will alter marine ecosytem processes. Calcifying organisms might be particularly vulnerable to these alterations in the speciation of the marine carbonate system. While previous research efforts have mainly focused on external dissolution of shells in seawater under saturated with respect to calcium carbonate, the internal shell interface might be more vulnerable to acidification. In the case of the blue mussel Mytilus edulis, high body fluid pCO2 causes low pH and low carbonate concentrations in the extrapallial fluid, which is in direct contact with the inner shell surface. In order to test whether elevated seawater pCO2 impacts calcification and inner shell surface integrity we exposed Baltic M. edulis to four different seawater pCO2 (39, 142, 240, 405 Pa) and two food algae (310–350 cells mL−1 vs. 1600–2000 cells mL−1) concentrations for a period of seven weeks during winter (5°C). We found that low food algae concentrations and high pCO2 values each significantly decreased shell length growth. Internal shell surface corrosion of nacreous ( = aragonite) layers was documented via stereomicroscopy and SEM at the two highest pCO2 treatments in the high food group, while it was found in all treatments in the low food group. Both factors, food and pCO2, significantly influenced the magnitude of inner shell surface dissolution. Our findings illustrate for the first time that integrity of inner shell surfaces is tightly coupled to the animals' energy budget under conditions of CO2 stress. It is likely that under food limited conditions, energy is allocated to more vital processes (e.g. somatic mass maintenance) instead of shell conservation. It is evident from our results that mussels exert significant biological control over the structural integrity of their inner shell surfaces

Effects of elevated seawater pCO2 on the blue mussel Mytilus edulis

Due to rising atmospheric carbon dioxide concentrations, the oceans take up more C02 resulting in a decrease of seawater pH. This effect is called ocean acidification. Already today, low pH values can be encountered in Kiel Fjord during summer, when COrenriched bottom water is upwelled to the surface. In the present study, recently settled Mytilus edulis were grown for 7 weeks under experimental conditions. The effect of 4 pC02 treatments (control=380, 1120, 2400, 4000 μatm) in combination with 3 different feeding levels (low, medium, high) of Rhodomonas sp. cells on mussel growth was measured. Low food supply had a larger negative impact on shell length growth than elevated pC02 (hypercapnia), while high nutritional supply could compensate a negative effect of hypercapnia. In the 4000 μatm group, mussels reached a mean length of about 1301 ± 75 μm and 3380 ± 677 μm under low and high feeding conditions, respectively. No differences in the length-dry mass ratio were detected, but high pC02 (4000 μatm) incubated shells contained significantly more organic and less calcium carbonate. The organic content increased to 13-15.6 % compared to 11.5-13 % of shell dry mass in the control treatment. Since the organic part of the shell and the body somatic tissue make up similar fractions of total organic mass, shell formation was associated with high energetic costs. 43-84 % of the energy uptake in the low and 33-46 % in the high feeding group accounted for energy that was used for growth processes (somatic and shell). Mussels of the intermediate feeding group used 23-63% of the energy input for growth, with lowest values under highest hypercapnia. The remaining energy fraction was used in respiration and excretion. These parameters were also measured and displayed high fluctuations, which might be due to methodical problems. The results of the study support the view that Mytilus edulis populations can cope with the near future predicted ocean acidification when enough food is available

Performance of gammarid spp. from different regions under stressful conditions in common garden experiments

Additional file 2. The RANSAC labelled tree trunks are displayed in green (28 of 30). An elevation filter was applied to the ground returns. Extract the .ZIP archive and open `index.html’ in a WebGL supporting web browser (e.g. FireFox 4.0+ or chrome 9.0+) to view in 3D with rotation and zoom options