Marine Research Findings of the VECTORS Project

This website provides access to the research results of the VECTORS project, which can be used to support marine management decisions, policies and governance as well as future research and investment. VECTORS was a large scale project that brought together more than 200 expert researchers from 16 different countries. It examined the significant changes taking place in European seas, their causes, and the impacts they will have on society.


All of the publications created as part of the VECTORS project are listed below (latest first).
Please use the search box below to find a publication by title, author(s), year or keyword; the most relevant results will be displayed at the top of the page.

  • Manzari, C., B. Fosso, M. Marzano, A. Annese, R. Caprioli, A.M. D'Erchia, C. Gissi, M. Intranuovo, E. Picardi, M. Santamaria, S. Scorrano, G. Sgaramella, L. Stabili, S. Piraino and G. Pesole. (2015). The influence of invasive jellyfish blooms on the aquatic microbiome in a coastal lagoon (Varano, SE Italy) detected by an Illumina-based deep sequencing strategy. Biological Invasions 17(3), 923-940. doi:10.1007/s10530-014-0810-2
    View abstract The rapid expansion of multicellular native and alien species outbreaks in aquatic and terrestrial ecosystems (bioinvasions) may produce significant impacts on bacterial community dynamics and nutrient pathways with major ecological implications. In aquatic ecosystems, bioinvasions may cause adverse effects on the water quality resulting from changes in biological, chemical and physical properties linked to significant transformations of the microbial taxonomic and functional diversity. Here we used an effective and highly sensitive experimental strategy, bypassing the efficiency bottleneck of the traditional bacterial isolation and culturing method, to identify changes of the planktonic microbial community inhabiting a marine coastal lagoon (Varano, Adriatic Sea) under the influence of an outbreakforming alien jellyfish species. Water samples were collected from two areas that differed in their level of confinement inside in the lagoon and jellyfish densities (W, up to 12.4 medusae m-3; E, up to 0.03 medusae m-3) to conduct a snapshot microbiome analysis by a metagenomic approach. After extraction of the genetic material in the environmental water samples, we deepsequenced metagenomic amplicons of the V5-V6 region of the 16S rRNA bacterial gene by an Illumina MiSeq platform. Experiments were carried out in triplicates, so six libraries of dual indexed amplicons of 420 bp were successfully sequenced on the MiSeq platform using a 2 9 250 bp paired-end sequencing strategy. Approximately 7.5 million paired-end reads (i.e. 15 million total reads) were generated, with an average of 2.5 million reads (1.25 Mpairs) per sample replicate. The sequence data, analyzed through a novel bioinformatics pipeline (BioMaS), showed that the structure of the resident bacterial community was significantly affected by the occurrence of jellyfish outbreaks. Clear qualitative and quantitative differences were found between the western and eastern areas (characterized by many or few jellyfish), with 84 families, 153 genera and 324 species in the W samples, and 104 families, 199 genera and 331 species in the E samples. Significant differences between the two sampling areas were particularly detected in the occurrence of 16 families, 22 genera and 61 species of microbial taxa. This is the first time that a NGS platform has been used to screen the impact of jellyfish bioinvasions on the aquatic microbiome, providing a preliminary assessment of jellyfish-driven changes of the functional and structural microbial biodiversity.
  • David, M. and S. Gollasch. (2015). Global maritime transport and ballast water management. Invading Nature - Springer Series in Invasion Ecology 8, 1-11. doi:10.1007/978-94-017-9367-4_1
    View abstract Today global shipping transports over 90 % of the world’s overseas trade and trends anticipate that it will continue to play an increasing role world-wide. Shipping operations inevitably include also pressures on natural environments. The most recent waterborne threat is the transfer of harmful aquatic organisms and pathogens with ballast water and sediments releases, which may result in harmful effects on the natural environment, human health, property and resources globally. The significance of the ballast water issue was already addressed in 1973 by the International Maritime Organization (IMO) as the United Nations specialised agency for the regulation of international maritime transport at the global scale. Committed work by many experts, scientists, politicians, IGOs and NGOs at IMO resulted in the adoption if the International Convention for the Control and Management of Ships’ Ballast Water and Sediments (BWM Convention) in February 2004, which is now to be ratified and implemented. Work on ballast water management issues has also shown to be very complex, hence there are no simple solutions. Nevertheless, the BWM Convention represents a globally uniform framework for the implementation of ballast water management measures, and different supporting tools like risk assessment and decision support systems have been developed to support its efficiency. In this chapter the reader is introduced to various ballast water issues and responses to it. The intention of this book and the overview of its content is also presented.
  • Azzurro, E., M. Goren, A. Diamant, B.S. Galil and G. Bernardi. (2015). Establishing the identity and assessing the dynamics of invasion in the Mediterranean Sea by the dusky sweeper, Pempheris rhomboidea Kossmann & Räuber, 1877 (Pempheridae, Perciformes). Biological Invasions 17(3), 815-826. doi:10.1007/s10530-014-0836-5
    View abstract We investigate the genetic diversity of the sweeper Pempheris, a biological invader that entered the Mediterranean Sea via the Suez Canal. Two mitochondrial regions and one nuclear region were sequenced and topological reconstructions investigated from samples collected from the eastern Mediterranean Sea, Red Sea and three Indo-Pacific localities. Morphological and molecular analyses assigned samples from this study to three distinct species of Pempheris in the Red Sea (P. flavicyla, P. rhomboidea, and P. tominagai) and confirmed a misidentification of the Mediterranean sweepers, previously identified as P. vanicolensis and now recognized as P. rhomboidea. Pempheris rhomboidea clustered in a single clade including specimens from Madagascar and South Africa. Similarly to most other studied Lessepsian bioinvaders, no evidence of a genetic bottleneck in its invasive Mediterranean population was found. Yet, lowered gene flow levels were observed between Red Sea and Mediterranean populations in this species. These findings highlight the importance of molecular tools to the proper identification of morphologically challenging alien organisms and contribute to the understanding of the dynamics of Lessepsian invasions.
  • Tepolt, C.K. (2015). Adaptation in marine invasion: a genetic perspective. Biological Invasions 17(3), 887-903. doi:10.1007/s10530-014-0825-8
    View abstract Genetic adaptation—heritable changes that alter an organism’s performance—may facilitate invasion at several scales, but is seldom considered in predicting and managing marine invasions. However, a growing body of research—largely based on emerging genetic approaches—suggests that adaptation is possible and potentially widespread in the marine realm. Here, I review evidence for adaptation in marine invasion, considering both quantitative and genetic studies. Quantitative studies, which consider trait-based differences between populations or individuals without directly examining genetic makeup, have suggested local adaptation in several high-profile species. This implies that invasion risk may not be constant from population to population within a species, a key assumption of most invasion models. However, in many quantitative studies, the effects of heritable adaptive changes may be confounded with the effects of plasticity. Molecular approaches can help disentangle these effects, and studies at the genomic level are beginning to elucidate the specific genetic patterns and pathways underlying adaptation in invasion. While studies at this scale are currently rare in the marine invasion literature, they are likely to become increasingly prevalent—and useful—now that next-generation sequencing approaches have become tractable in non-model systems. Both traditional and emerging genetic approaches can improve our understanding of adaptation in marine invasions, and can aid managers in making accurate predictions of invasion spread and risk.
  • Rius, M., X. Turon, G. Bernardi, F.A.M. Volckaert and F. Viard. (2015). Marine invasion genetics: from spatio-temporal patterns to evolutionary outcomes. Biological Invasions 17(3), 869-885. doi:10.1007/s10530-014-0792-0
    View abstract Marine invasion genetics: from spatio-temporal patterns to evolutionary outcomes. Biological Invasions. doi:10.1007/s10530-014-0792-0 $Over the last 15 years studies on invasion genetics have provided important insights to unravel cryptic diversity, track the origin of colonizers and reveal pathways of introductions. Despite all these advances, to date little is known about how evolutionary processes influence the observed genetic patterns in marine biological invasions. Here, firstly we review the literature on invasion genetics that include samples from European seas. These seas constitute a wide array of unique water masses with diverse degrees of connectivity, and have a long history of species introductions. We found that only a small fraction of the recorded introduced species has been genetically analysed. Furthermore, most studies restrict their approach to describe patterns of cryptic diversity and genetic structure, with the underlying mechanisms involved in the invasion process being largely understudied. Secondly, we analyse how genetic, reproductive and anthropogenic traits shape genetic patterns of marine introduced species. We found that most studies reveal similar genetic diversity values in both native and introduced ranges, report evidence of multiple introductions, and show that genetic patterns in the introduced range are not explained by taxonomic group or reproductive strategy. Finally, we discuss the evolutionary implications derived from genetic patterns observed in non-indigenous species. We identify different scenarios that are determined by propagule pressure, phenotypic plasticity and pre-adaptation, and the effects of selection and genetic admixture. We conclude that there is a need for further investigations of evolutionary mechanisms that affect individual fitness and adaptation to rapid environmental change.
  • Molla, E., G. Cimino and M.T. Ghiselin.$  (2015). Alien biomolecules: a new challenge for natural product chemists. Biological Invasions 17(3), 941-950. doi:10.1007/s10530-014-0835-6
    View abstract Among natural products there are molecules well known to influence the abundance and distribution of marine organisms and to play important roles in their interactions with one another. Recently, chemical ecologists have also started to consider how research on natural products might be useful in understanding marine biological invasions, assessing their impact in the invaded areas, and considering how to deal with them. Their efforts especially focused on the Mediterranean Sea, which is one of the major hotspots of marine biological invasions on earth, showing in what way marine natural products (MNPs) may influence (1) the ability of exotic marine organisms to invade and to get established, (2) how they affect the invaded biota, and (3) public health and the economy. In all cases, the study of such chemical warfare between alien and native species started with the isolation of the pure chemicals required for chemical structure elucidation and subsequent biological testing, implying a central role of natural product chemistry in approaching critical issues in invasion biology. In this position paper we also introduce a theme of possible interest for managing marine invasive species, based on the exploitation of available chemical and biological information on MNPs. We show how a kind of chemical data originally gathered for other objectives—such as obtaining drugs from the sea—might also offer valid alternatives to unrealistic eradication campaigns, becoming the basis for a desirable commercial use of the bioactive compounds obtainable from marine pests, thus paving the way for making the control of invasions profitable. The pests might then be harvested, reducing their impact on marine ecosystems.
  • Dawson, M.N., K. Cieciel, M.B. Decker, G.C. Hays, C.H. Lucas and K.A. Pitt. (2015). Population-level perspectives on global change: genetic and demographic analyses indicate various scales, timing, and causes of scyphozoan jellyfish blooms. Biological Invasions 17(3), 851-867. doi:10.1007/s10530-014-0732-z
    View abstract Whether a perceived increase in the abundance of jellyfishes is related to changing marine environments has been considered primarily using large-scale analyses of multi-species assemblages. Yet jellyfish blooms—rapid increases in the biomass of pelagic coelenterate species—are single-species demographic events. Using published and new genetic analyses and population surveys, we investigate whether there may be a critical knowledge gap between the scales of recent analyses and the scales of natural phenomena. We find that scyphomedusae may show population genetic structure over scales of tens to hundreds of kilometers, that environments vary regionally and locally, and that populations of medusae can display uncorrelated dynamics on these scales. These findings suggest genetic differences between populations and/or environmental differences between sites are important determinants of population dynamics in these jellyfishes. Moreover, the local abundance of medusae may be most strongly correlated with preceding rather than current local environmental conditions, indicating there is a cumulative timecourse to the formation of ‘blooms’. Broad-scale macro-ecological analyses will need to build from coordinated, long-term, fine-grained studies to synthesize, rather than mask, population-level phenomena in larger-scale analyses.
  • Darling, J.A. (2015). Genetic studies of aquatic biological invasions: closing the gap between research and management. Biological Invasions 17(3), 951-971. doi:10.1007/s10530-014-0726-x
    View abstract Recent years have seen a dramatic rise in the application of genetic methods to understand aquatic biological invasions. In part these methods have been adopted to address fundamental questions in biogeography, evolutionary biology, population ecology, and other fields. But it is also commonly suggested that genetic information has the potential to directly inform the management of aquatic invasions. Here I explore the potential promise of genetic approaches for informing management of aquatic invasive species, the degree to which that promise has been realized in terms of utilization of genetic information by managers and other decision-makers, and the likely limitations to the value of genetic methods (both in principle and in practice) and ways in which these limitations might be overcome. I consider a range of possible applications of genetic tools for management, including molecular detection and identification of cryptic invaders, source tracking and reconstruction of invasion history, and inference of population demographics. Retrospective assessment of the utility of such applications is based on both literature review and solicitation of expert opinion, and suggests that a number of hurdles likely often prevent genetic information from effectively informing decision-making. These include (1) limitations or misunderstandings of the resolution and certainty afforded by genetic analysis; (2) failure to engage decision-makers in problem formulation, research design and research implementation; and (3) complex relationships between basic research and management actions. While some of the obstacles considered are rooted in theoretical and practical limitations of genetic analysis, others are clearly associated with poor communication and insufficient engagement of potential end-users of genetic information. I consider possible avenues for overcoming these obstacles and for improving the applicability of genetic information for supporting management decisions.
  • Comtet, T., A. Sandionigi, F. Viard and M. Casiraghi. (2015). DNA (meta)barcoding of biological invasions: a powerful tool to elucidate invasion processes and help managing aliens. Biological Invasions 17(3), 905-922. doi:10.1007/s10530-015-0854-y
    View abstract Biological invasions are a major threat to the world’s biodiversity with consequences on ecosystem structure and functioning, species evolution, and human well-being (through ecosystem services). Conservation of biological diversity and management of biological resources require multi-level management strategies on non-native species, in order to (1) prevent biological introductions, (2) detect non-native species at an early stage of the introduction, and (3) eradicate or maintain at a low level of population density non-native species that were successfully introduced. A pre-requisite to any control measures on non-native species is the ability to rapidly and accurately identify the putative threatening alien species. DNA barcoding, and its recent extension, DNA metabarcoding are complementary tools that have proved their value in the identification of living beings. Here we review their use in the identification of non-native species at several steps of the introduction processes, and how they can be applied in the control and management of biological introductions. Through examples covering various taxa and ecosystems (terrestrial, freshwater, marine), we highlight the strengths and weaknesses of approaches that we foresee as crucial in the implementation of early warning strategies.
  • Nurkse, K., J. Kotta, H. Orav-Kotta, M. Pärnoja and I. Kuprijanov. (2015). Laboratory experiment on the habitat occupance of the crab Rhithropanopeus harrisii (Gould) in an invaded ecosystem: The north-eastern Baltic Sea. Estuarine, Coastal and Shelf Science 154(5), 152-157. doi:10.1016/j.ecss.2014.12.046
    View abstract The Harris mud crab (Rhithropanopeus harrisii) arrived to the Baltic Sea in 1936. It was not until the late 2000s when the species considerably expanded its distribution area towards the northern Baltic Sea and formed a viable and expanding population. This introduction represents an appearance of a completely new function, as such larger epibenthic predators were previously missing from north-eastern Baltic Sea. In order to assess potential impacts of the crab to the invaded ecosystem, knowledge of the crab habitat preferences is required. This study experimentally evaluated the habitat occupancy of the Harris mud crab. The crab stayed more in vegetated boulders compared to unvegetated boulders or sandy habitats. There was an interactive effect between the presence of prey and crab population density with prey availability increasing the crab's affinity towards less favored habitats when population densities were low. Increased aggression between crab individuals increased their affinity towards otherwise less occupied habitats. Less favored habitats were typically inhabited by smaller individuals and presence of prey increased occupancy of some habitats for larger crabs. The experiment demonstrated that the crab may inhabit a large variety of habitats with stronger affinity towards boulder fields covered with the brown macroalga Fucus vesiculosus. This implies stronger impact of crab in such habitats in the invaded ecosystem.
  • Girardin, R., Y. Vermard, O. Thébaud, A. Tidd and P. Marchal. (2015). Predicting fisher response to competition for space and resources in a mixed demersal fishery. Ocean & Coastal Management 106, 124-135. doi:10.1016/j.ocecoaman.2015.01.017
    View abstract Understanding and modelling fleet dynamics and their response to spatial constraints is a prerequisite to anticipating the performance of marine ecosystem management plans. A major challenge for fisheries managers is to be able to anticipate how fishing effort is re-allocated following any permanent or seasonal closure of fishing grounds, given the competition for space with other active maritime sectors. In this study, a Random Utility Model (RUM) was applied to determine how fishing effort is allocated spatially and temporally by the French demersal mixed fleet fishing in the Eastern English Channel. The explanatory variables chosen were past effort i.e. experience or habit, previous catch to represent previous success, % of area occupied by spatial regulation, and by other competing maritime sectors. Results showed that fishers tended to adhere to past annual fishing practices, except the fleet targeting molluscs which exhibited within year behaviour influenced by seasonality. Furthermore, results indicated French and English scallop fishers share the same fishing grounds, and maritime traffic may impact on fishing decision. Finally, the model was validated by comparing predicted re-allocation of effort against observed effort, for which there was a close correlation.
  • Boyes, S.J. and M. Elliott. (2015). The excessive complexity of national marine governance systems – Has this decreased in England since the introduction of the Marine and Coastal Access Act 2009? Marine Policy 51, 57-65. doi:10.1016/j.marpol.2014.07.019
    View abstract With successive Government restructuring and the introduction of the Marine and Coastal Access Act in 2009, this paper revisits a previous set of organograms created in 2006 indicating the government departments with responsibilities relating to the marine and coastal environment in England in 2014. The 2009 Act presented an opportunity to harmonise marine management by simplifying the complexity in England through a radical restructuring of marine governance; however this is apparently not the case with many overlapping responsibilities still existing. This paper provides an overview of the 2009 Act, discussing some of the significant changes like the creation of the Marine Management Organisation (MMO), examines the current structure of marine management in England following its enactment and highlights the continued overlaps in jurisdiction, responsibilities and complexity of the government agencies with a marine remit.
  • Keyl, F., A.J. Kempf and A.F. Sell. (2015). Sexual size dimorphism in three North Sea gadoids. Journal of Fish Biology 86(1), 261-275. doi:10.1111/jfb.12579
    View abstract Existing biological data on whiting Merlangius merlangus, cod Gadus morhua and haddock Melanogrammus aeglefinus from a long-term international survey were analysed to address sexual size dimorphism (SSD) and its effect on their ecology and management. Results show that SSD, with larger females of the same age as males, is a result of higher growth rates in females. A direct consequence of SSD is the pronounced length-dependent female ratio that was found in all three gadoids in the North Sea. Female ratios of the three species changed from equality to female dominance at specific dominance transition lengths of c. 30, 35 and 60 cm for M. merlangus, G. morhua and M. aeglefinus, respectively. An analysis by area for M. merlangus also revealed length dependence of female ratios. SSD and length-dependent female ratios under most circumstances are inseparable. Higher overall energy demand as well as a higher energy uptake rate must result from the observed SSD and dimorphism in growth rates. Potential processes related to feeding, locomotion and physiology are proposed that could balance the increased energy investment of females. Potential consequences of SSD and length dependency of female ratios are the reduction of the reproductive potential of a stock due to size-selective fishing and biased assessment of the true size of the female spawning stock that could distort decisions in fisheries management.
  • Gueroun, S.K.M., O.K.-D. Yahia, A. Deidun, V. Fuentes, S. Piraino and M.N.D. Yahia. (2014). First record and potential trophic impact of Phyllorhiza punctata (Cnidaria: Scyphozoa) along the north Tunisian coast (South Western Mediterranean Sea). Italian Journal of Zoology. doi:10.1080/11250003.2014.981306
    View abstract The Australian spotted scyphomedusa Phyllorhiza punctata was recorded for the first time in Tunisian waters in August 2012, in the lagoon of Bizerte (Tunisia). Metaephyrae and juveniles occurred simultaneously in August 2012. The occurrence of adult medusae was detected from September to November 2012, and from August to October 2013. This is the second record of a reproducing population of P. punctata in the Mediterranean Sea. The low abundance of mesozooplankton in summer and autumn 2012 coincides temporally with the highest density of P. punctata recorded in the lagoon, suggesting that predation by this alien jellyfish may have been a limiting factor for the mesozooplankton abundance on site.
  • Isinibilir, M., L. Martell, E.N. Topçu, I.N. Yilmaz and S. Piraino. (2014). First inventory of the shallow-water benthic hydrozoan assemblages of Gökçeada Island (northern Aegean Sea). Italian Journal of Zoology. doi:10.1080/11250003.2014.977970
    View abstract The hydroid fauna of the Mediterranean Sea is considered one of the best known in the world, but the hydrozoans of the Aegean Sea remain poorly studied, hindering efforts to identify alien and invasive species in the region. The spatial and seasonal composition of the shallow-water (0–20 m depth) benthic hydrozoan assemblage from Gökçeada Island was investigated in summer 2012 and winter 2013. Overall, 48 hydrozoan taxa were identified, and their presence and ecological features are discussed herein. Twelve species are recorded for the first time in the Aegean Sea, and the same number for the Turkish coasts. Differences in species composition were detected between the northern and southern coasts of Gökçeada by cluster, multidimensional scaling (MDS) and permutational multivariate analysis of variance (PERMANOVA) analysis, whereas seasonal and vertical distribution patterns were not statistically significant. Differences in species richness and composition between the northern and southern coasts may be explained by the distinct geomorphological aspects of the shores, providing a spatial heterogeneity in the availability of substrates for the hydroid colonies. Observed differences are attributable to the occurrence and/or abundance of common species such as Sertularella ellisii, Aglaophenia tubiformis, Clytia hemisphaerica, Clytia linearis, Eudendrium racemosum, Plumularia obliqua, Eudendrium capillare, Turritopsis dorhnii and Dynamena disticha, rather than to the presence of rare, exclusive species
  • Wlodarska-Kowalczuk, M., E. Jankowska, L. Kotwichi and P. Balazy. (2014). Evidence of season-dependency in vegetation effects on macrofauna in temperate seagrass meadows (Baltic Sea). Plos One 9(7), e100788. doi:10.1371/journal.pone.0100788
    View abstract Seagrasses and associated macrophytes are important components of coastal systems as ecosystem engineers, habitat formers, and providers of food and shelter for other organisms. The positive impacts of seagrass vegetation on zoobenthic abundance and diversity (as compared to bare sands) are well documented, but only in surveys performed in summer, which is the season of maximum canopy development. Here we present the results of the first study of the relationship between the seasonal variability of seagrass vegetation and persistence and magnitude of contrasts in faunal communities between vegetated and bare sediments. The composition, abundance, biomass, and diversity of macrozoobenthos in both habitats were compared five times throughout the year in temperate eelgrass meadows in the southern Baltic Sea. Significant positive effects of macrophyte cover on invertebrate density and biomass were recorded only in June, July, and October when the seagrass canopy was relatively well developed. The effects of vegetation cover on faunal species richness, diversity, and composition persisted throughout the year, but the magnitude of these effects varied seasonally and followed changes in macrophyte biomass. The strongest effects were observed in July and coincided with maximums in seagrass biomass and the diversity and biomass of other macrophytes. These observations indicate that in temperate, clearly seasonal systems the assessment of macrophyte impact cannot be based solely on observations performed in just one season, especially when that season is the one in which macrophyte growth is at its maximum. The widely held belief that macrophyte cover strongly influences benthic fauna in marine coastal habitats, which is based on summer surveys, should be revisited and complemented with information obtained in other seasons.
  • Lyons, D.A., C. Arvanitidis, A.J. Blight, E. Chatzinikolaou, T. Guy-Haim, I. Kotta, H. Orav-Kotta, A.M. Queiros, G. Rilov, P.J. Somerfield and T.P. Crowe. (2014). Macroalgal blooms alter community structure and primary productivity in marine ecosystems. Global Change Biology 20(9), 2712-2724. doi:10.1111/gcb.12644
    View abstract Eutrophication, coupled with loss of herbivory due to habitat degradation and overharvesting, has increased the frequency and severity of macroalgal blooms worldwide. Macroalgal blooms interfere with human activities in coastal areas, and sometimes necessitate costly algal removal programs. They also have many detrimental effects on marine and estuarine ecosystems, including induction of hypoxia, release of toxic hydrogen sulfide into the sediments and atmosphere, and the loss of ecologically and economically important species. However, macroalgal blooms can also increase habitat complexity, provide organisms with food and shelter, and reduce other problems associated with eutrophication. These contrasting effects make their overall ecological impacts unclear. We conducted a systematic review and metaanalysis to estimate the overall effects of macroalgal blooms on several key measures of ecosystem structure and functioning in marine ecosystems. We also evaluated some of the ecological and methodological factors that might explain the highly variable effects observed in different studies. Averaged across all studies, macroalgal blooms had negative effects on the abundance and species richness of marine organisms, but blooms by different algal taxa had different consequences, ranging from strong negative to strong positive effects. Blooms' effects on species richness also depended on the habitat where they occurred, with the strongest negative effects seen in sandy or muddy subtidal habitats and in the rocky intertidal. Invertebrate communities also appeared to be particularly sensitive to blooms, suffering reductions in their abundance, species richness, and diversity. The total net primary productivity, gross primary productivity, and respiration of benthic ecosystems were higher during macroalgal blooms, but blooms had negative effects on the productivity and respiration of other organisms. These results suggest that, in addition to their direct social and economic costs, macroalgal blooms have ecological effects that may alter their capacity to deliver important ecosystem services.
  • Kristensen, K., U.H. Thygesen, K.H. Andersen, J.E. Beyer and J.M. Jech. (2014). Estimating spatio-temporal dynamics of size-structured populations. Canadian Journal of Fisheries and Aquatic Sciences 71(2), 326-336. doi:10.1139/cjfas-2013-0151
    View abstract Spatial distributions of structured populations are usually estimated by fitting abundance surfaces for each stage and at each point of time separately, ignoring correlations that emerge from growth of individuals. Here, we present a statistical model that combines spatio-temporal correlations with simple stock dynamics to estimate simultaneously how size distributions and spatial distributions develop in time. We demonstrate the method for a cod (Gadus morhua) population sampled by trawl surveys. Particular attention is paid to correlation between size classes within each trawl haul due to clustering of individuals with similar size. The model estimates growth, mortality, and reproduction, after which any aspect of size structure, spatio-temporal population dynamics, as well as the sampling process can be probed. This is illustrated by two applications: (i) tracking the spatial movements of a single cohort through time and (ii) predicting the risk of bycatch of undersized individuals. The method demonstrates that it is possible to combine stock assessment and spatio-temporal dynamics; however, this comes at a high computational cost. The model can be extended by increasing its ecological fidelity, although computational feasibility eventually becomes limiting.
  • Laur, K., H. Ojaveer, M. Simm and R. Klais. (2014). Multidecadal dynamics of larval gobies Pomatoschistus spp. in response to environmental variability in a shallow temperate bay. Estuarine, Coastal and Shelf Science 136, 112-118. doi:10.1016/j.ecss.2013.11.011
    View abstract Compared to commercial fish, there is relatively limited information available about the dynamics of non-commercial fish that very often play important structural and functional roles in marine ecosystems. Long-term investigations that provide quantitative estimates of the population dynamics as a function of environmental variability are needed to understand the ecology and role of the non-commercial fish in the ecosystem, and assist the ecosystem management where relevant. Here we analyze the inter-annual variability and long-term trends of the abundance of the larval non-commercial gobies Pomatoschistus spp. in a shallow coastal bay (Pärnu Bay, northeastern Baltic Sea) in 1959-2010, in relation to climate and prey field related variables. The abundance of larval Pomatoschistus spp. decreased over the last 50 years along with the concomitant decrease in the water transparency. The first appearance of larvae has shifted for about two weeks earlier and is mostly related to the timing of ice cover breakdown. However, some of the effects of the environmental forcing on larval fish may be obscured by the uncertainty of species identification of individuals of the genus Pomatoschistus at larval stage, and the investigated population of Pomatoschistus spp. consists of at least two species with slightly different ecologies and also environmental preferences.
  • Kalaus, M. and H. Ojaveer. (2014). Over one decade of invasion: the non-indigenous cladoceran Evadne anonyx G.O. Sars, 1897 in a low-salinity environment. Aquatic Invasions 9(4), 499-506. doi:10.3391/ai.2014.9.4.08
    View abstract 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.
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