Composition and dynamics of fish stocks in the Gulf of Riga ecosystem

http://www.ester.ee/record=b1053387~S1*es

Over one decade of invasion: the non-indigenous cladoceran Evadne anonyx G.O. Sars, 1897 in a low-salinity environment

Invasive species are often in focus in the non-indigenous species (NIS) research while low-abundance species receive relatively little attention. However, tracking NIS dynamics since the early stages of an invasion provides valuable information on the ecology of invasions. In the current paper, we investigated the invasion history and population dynamics of the small-bodied cladoceran Evadne anonyx G. O. Sars, 1897 in the Gulf of Riga (Baltic Sea) almost since its first detection in 2000. The species already was widespread the Gulf of Riga in 2001 and has been found in nearly every subsequent sample collected during summer months. However, the abundance of the species remained low, seldom 100 individuals m-3. Both, salinity and water temperature affected the spatial distribution and population abundance of E. anonyx. The species was found to occur only sporadically at salinities below ca. 6. To obtain reliable presence/absence and density estimates on this small-bodied cladoceran, the entire zooplankton sample needed to be analysed

Methodological challenges in assessing the environmental status of a marine ecosystem: Case study of the Baltic Sea

Assessments of the environmental status of marine ecosystems are increasingly needed to inform management decisions and regulate human pressures to meet the objectives of environmental policies. This paper addresses some generic methodological challenges and related uncertainties involved in marine ecosystem assessment, using the central Baltic Sea as a case study. The objectives of good environmental status of the Baltic Sea are largely focusing on biodiversity, eutrophication and hazardous substances. In this paper, we conduct comparative evaluations of the status of these three segments, by applying different methodological approaches. Our analyses indicate that the assessment results are sensitive to a selection of indicators for ecological quality objectives that are affected by a broad spectrum of human activities and natural processes (biodiversity), less so for objectives that are influenced by a relatively narrow array of drivers (eutrophications, hazardous substances). The choice of indicator aggregation rule appeared to be of essential importance for assessment results for all three segments, whereas the hierarchical structure of indicators had only a minor influence. Trend-based assessment was shown to be a useful supplement to reference-based evaluation, being independent of the problems related to defining reference values and indicator aggregation methodologies. Results of this study will help in setting priorities for future efforts to improve environmental assessments in the Baltic Sea and elsewhere, and to ensure the transparency of the assessment procedure

Multidisciplinary perspectives on the history of human interactions with life in the ocean

Abstract There is an essentially circular interaction between the human social system and the marine ecosystem. The Oceans Past V Conference “Multidisciplinary perspectives on the history of human interactions with life in the ocean” held in Tallinn, Estonia, in May 2015 was an opportunity for the presentation and discussion of papers on a diverse array of topics that examined this socio-ecological system from a historical perspective. Here we provide background to the disciplines participating in the conference and to the conference itself. We summarize the conference papers that appear in this special volume of the ICES JMS and highlight issues which arose during general discussion. We make two conclusions. First, to have greater impact and ensure more efficient use of knowledge gained from marine historical ecology (MHE) and marine environmental history (MEH) in ecosystem-based management and related policy development, practitioners need to work more routinely with population and ecological modellers and statisticians. This will allow greater processing of the available historical data to derive ecologically meaningful properties that can then be used to assess the ecological impact of long-term changes of affected species and define appropriate and realistic management targets. Second, increased multi- and trans-disciplinary effort is required to better understand the relative importance of different human demographic, technological, economic, and cultural drivers on the patterns, intensities and trajectories of human activities affecting marine ecosystems.</jats:p

Meedia raamid keeruliste ühiskondlike nähtuste kajastamisel päevalehtedes: ühiskondliku kokkuleppe käsitlemine ajalehtedes Eesti Päevaleht ja Postimees

There are several essential tasks to implement social functions in addition to the informative function of mass media; for example creating publicity, framing social activity or intellectual environment of society or offering ground to criticise independently and profoundly society or the government. On the other hand, society itself limits media through its values and beliefs by reflecting the attitudes transmitted to the auditorium as a result of media framing. A process of recurrent representation forms frames with same themes, aspects and sources being highlighted more than the others, resulting in construction a one-sided, even simplified vision. Therefore, the treatment of such complicated social phenomena like social/public agreement, which concerns different subjects on different stages, consists of main and subdocuments as well as includes different social groups, in mass media may result in suppressing public debate between concerned parties due to simplified frames of media. The purpose of current research is to examine how the nation-wide Estonian daily newspapers – Eesti Päevaleht and Postimees framed social/public agreement during the period of 2001 to 2004. The author aims to find an answer to the question of how the daily newspapers presented the phenomenon of social/public agreement as a talking-point; how the daily newspapers contextualised the agreement and what subject matters were made news- worthy in the process of representation. The author chose integrated textual analysis to conduct the research. The sample consists of 147 articles concerning social/public agreement published in Eesti Päevaleht and Postimees during the period of 23.02.2001 – 22.11.2004. Empiric analysis showed that major nation-wide Estonian daily newspapers presented the subject matter of social/public agreement as a talking-point mainly in year 2003, emphasizing the importance of the subject matter especially during that year by preoccupying the public attention through measures such as reference on the front page, recurrent presentation of key-words in essential parts of the article, placement within the issue etc. The subject matter was mainly expressed in feature articles, less in special topic news stories. The authors of feature articles were mainly journalists and politicians, whereby several politicians were introduced rather as opinion leaders than politicians. Different politicians were most frequently quoted and paraphrased as spokespersons. The analysis of photographs presented along with the piece of writing, showed that while in Eesti Päevaleht entrepreneurs were most frequently imaged in connection with the subject matter of social/public agreement, in Postimees the photos of coalition politicians were most frequently used. One of the conclusion of current research is that the major Estonian daily newspapers presented the subject matter of social/public agreement as a talking-point mainly in year 2003 by contextualizing politicians (several of which were presented as opinion leaders) and experts as important parties of the agreement. The analysis identified two differences while forming the topic: while Eesti Päevaleht positioned the subject matter of social/public agreement as primary or secondary, Postimees positioned the subject matter mainly as secondary or insignificant. The second difference applied to the selection of photo materials used to illustrate the subject matter: while in Eesti Päevaleht photographs of entrepreneurs were dominant, in Postimees the photos of politicians were most frequently used. Several additional subject matters and various concerned parties emerged in connection with the representation of social/public agreement. While in 2001 the economic growth was raised as the main goal of social/public agreement, in 2002 economic aspects were receded into background and a need for public and social discussion emerged in turn. Politicians and citizens were represented as concerned parties. In 2003, four issues emerged in the process of representation, the central issue being the content and text related matters of social/public agreement. Politicians were presented as concerned parties and journalists, politicians and persons connected with the development of the agreement were presented as spokespersons. The second important issue appeared to be the treatment of social/public agreement as a mechanism guaranteeing the continuance of the Estonian state and government. Politicians and citizens were presented as concerned parties, experts were presented as spokespersons. The third issue dealt with contradictions between the authors of social/public agreement and the critics. Politicians, among them Estonian President Rüütel, were presented as concerned parties; journalists, politicians and initiators of the agreement were presented as spokespersons. The fourth issue was the deadline of social/public agreement. Journalists, politicians and authors of the agreement were presented as spokespersons. In all the articles concerning the deadline of the agreement president Rüütel was presented as the concerned party. The main statement in 2004 was that of Estonia should change course towards becoming a knowledge based society for it is possible to reduce social inequality only through high quality education. Citizens and the government were represented as concerned parties.The largest number of articles with negatively toned headings was published in 2003. It also became obvious that the authors’ attitude towards the agreement changed in 2003, becoming more critical than it had been in the years of 2001 and 2002. The second conclusion of current research is that the noticeable accentuation of the phenomenon of social/public agreement in 2003 lead to changes in subject matters connected to the agreement. Instead of continuing the analytical discussion that began in 2002, it appeared that the spokespersons concentrated mainly on defining single aspects of the agreement. The analytical discussion was suddenly left out of the debate of public sphere. The analysis also showed that with every covered issue, politicians were always presented as concerned parties, being at the same time one of the most prominent group of spokespersons. Proceeding form the above mentioned the general conclusion of current Bachelor’s thesis is that Estonian nation-wide daily newspapers attached value and newsworthiness in representing the social/public agreement to single aspects of the agreement, and receded the analytical discussion to the background, by framing the subject matters of the agreement through the point of view and purposes (approaching elections, Euro referendum etc) of political elite. Since only one group’s – politicians – reality was constructed, it is possible to conclude that we are dealing with “public sphere constructed by media (Schultz 1997). The author concludes by stating that Estonian daily newspapers did not implement the functions of public forum (Bourdieu 2003), because instead of including as many groups as possible into the discussion, single concerned groups competed in defining their messages.http://tartu.ester.ee/record=b2118609~S1*es

Female ovarian abnormalities and reproductive failure of autumn-spawning herring (Clupea harengus membras) in the Baltic Sea

Fecundity and reproductive potential are important factors to be considered in evaluating trajectories and demographic predictions of fish populations. Therefore, characterizing the nature and quantifying the extent of any reproductive failure should be considered in fisheries studies. Here, we describe morphological changes in developed ovaries of autumn-spawning herring (Clupea harengus membras) caught in the northern Baltic Sea and evaluate the magnitude of this phenomenon during 3 consecutive years. Visibly, abnormal ovaries were histologically characterized by irregular-shaped oocytes in a vitellogenic or final maturation stage with coagulative necrosis and liquefaction of the yolk sphere, degraded follicle membranes, and fibrinous adhesion among oocytes. Such degeneration is presumed to cause complete infertility in the fish. The frequency of fish with abnormal ovaries varied annually between 10 and 15% among all females sampled. However, specific sampling events showed up to 90% females with abnormal gonads. The specific cause of this abnormality remains unknown; however, prevalence was associated with unfavourable environmental conditions encountered before spawning. Thus, ovarian abnormality was positively related to water temperatures, with the highest level found at ≥15°C and negatively related to the frequency of strong winds. The frequency of occurrence of abnormal gonads decreased with the progression of spawning from August to October. The observed abnormality and associated spawning failure will negatively affect the realized fecundity of autumn herring in the Baltic Sea and may act as a limiting factor for recovery of the stock, which has experienced profound depression during the last three decades

Long-term changes in a zooplankton community revealed by the sediment archive

To reconstruct changes in zooplankton communities in response to past anthropogenic perturbations, one possibility is to use the sedimentary records. We analyzed the sediments at a coastal site in the Northern Baltic Sea to relate changes in the zooplankton community to anthropogenic eutrophication and the invasion of a predatory cladoceran, Cercopagis pengoi. We sampled 30-cm laminated sediment cores and dated the sediment layers back to the 1950s. From each 1-cm layer, we measured eutrophication indicators (delta C-13, delta N-15, TC, TN, TP) and identified and counted zooplankton resting eggs (cladoceran, calanoid copepod, rotifer). In addition, we estimated the abundance of the cladoceran Bosmina (Eubosmina) maritima by counting subfossils (carapaces, headshields, and ephippia) and estimated the experienced stress as the relationship between sexual and asexual reproduction. Using redundancy and variance partitioning analyses, we found similar to 16% of the variation in the zooplankton community to be explained by eutrophication, and 24% of the variation in B. (E.) maritima abundance and reproduction mode to be explained by eutrophication and the introduction of the alien predator. Our results show a long-term shift from calanoid copepods and predatory cladocerans toward small-sized zooplankton species, like rotifers. Furthermore, the results indicate that the invasion of C. pengoi induced a short-term increase in sexual reproduction in B. (E.) maritima. The results indicate that anthropogenic eutrophication since the 1950s has altered the zooplankton community toward smaller species, while the invasion of the predatory cladoceran had only a transitory influence on the community during its expansion phase.Peer reviewe