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.

Publications

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.

  • Bulleri, F. (2013). Grazing by sea urchins at the margins of barren patches on Mediterranean rocky reefs. Marine Biology 160(9), 2493-2501. doi:10.1007/s00227-013-2244-2 http://dx.doi.org/10.1007/s00227-013-2244-2
    View abstract The role played by the urchins, Paracentrotus lividus and Arbacia lixula, in the formation and persistence of barren areas dominated by encrusting coralline macroalgae is yet to be fully elucidated. This study, carried out in the NW Mediterranean (43A degrees 30'N, 10A degrees 20'E) between February 2005 and April 2006, investigated how the loss or density decrease in one or both urchin species influences the recovery of erect macroalgal stands (dominated by filamentous forms) at the margins of barren areas. At a depth of 4-6 m, three barren patches were assigned to each of the following treatments: (1) control (natural densities of A. lixula and P. lividus); (2) 50 % of the natural density of A. lixula and natural density of P. lividus; (3) total removal of A. lixula and natural density of P. lividus; (4) 50 % of the natural density of P. lividus and natural density of A. lixula; (5) total removal of P. lividus and natural density of A. lixula; (6) 50 % of the natural densities of both A. lixula and P. lividus; (7) total removal of both A. lixula and P. lividus. The effects of the herbivore treatments were evaluated either in the presence or the absence of encrusting corallines. The partial or total removal of A. lixula, P. lividus or both favored the proliferation of filamentous macroalgae at the margins of barren patches. The presence of encrusting corallines reduced the development of these macroalgae. The results of this study suggest that a moderate decrease in the density of just one of the two species can decrease the ability of the herbivore assemblage to control the proliferation of filamentous macroalgae at the margins of barren patches. The extent of barren areas appears, therefore, to be regulated by the outcome of density-dependent interactions between the two species of sea urchins.
  • Boero, F., G. Belmonte, R. Bracale, S. Fraschetti, S. Piraino and S. Zampardi. (2013). A salp bloom (Tunicata, Thaliacea) along the Apulian coast and in the Otranto Channel between March-May 2013. F1000Research 2(181). doi:10.12688/f1000research.2-181.v1 http://dx.doi.org/10.12688/f1000research.2-181.v1
    View abstract Between March-May 2013 a massive Salpa maxima bloom was recorded by a citizen science study along the Ionian and Adriatic coast of the Salento peninsula (Italy). Citizen records were substantiated with field inspections along the coast and during an oceanographic campaign in the Otranto Channel. Salps clogged nets, impairing fishing activities along the coast. Swimmers were scared by the gelatinous appearance of the salps, and thought they were jellyfish. At the end of the bloom the dead bodies of the colonies, that were up to 6-7 m long, were accumulated along the coast and stirred by the waves, forming foams along dozens of kilometers of coast. The bloom also occurred at the Tremiti Islands, north of the Gargano Peninsula. The possible impacts of such events on the functioning of pelagic systems are discussed.
  • Bogi, C. and B.S. Galil. (2013). Cylichna villersii, an Erythraean cephalaspideid snail (Mollusca: Gastropoda: Opisthobranchia) in the eastern Mediterranean. Marine Biodiversity Records 6, e92. doi:10.1017/s1755267213000687 http://dx.doi.org/10.1017/s1755267213000687
    View abstract Cylichna villersii, a minute 'bubble snail' is newly recorded in the Mediterranean Sea from specimens recently collected along the Israeli coastline. The species, described and illustrated, matches the syntype collected in the Red Sea by Savigny. It is the eighth Erythraean alien cephalaspideid species recorded in the Levantine Basin. The recent collection of many living specimens in several continuously sampled locations attests to the speed of its establishment in the south-eastern Levant.
  • Bogi, C. and B.S. Galil. (2013). Monotygma watsoni, an Erythraean alien pyramidellid (Mollusca: Gastropoda: Heterobranchia) newly recorded in the Mediterranean Sea. Marine Biodiversity Records 6, e80. doi:10.1017/s175526721300047x http://dx.doi.org/10.1017/S175526721300047X
    View abstract Monotygma watsoni, a minute parasitic pyramidellid gastropod is newly recorded in the Mediterranean Sea from specimens recently collected off the Israeli coastline. The species, described and illustrated, matches the three syntypes of Ceratia watsoni collected in the southern Red Sea. The characteristic protoconch and teleoconch sculpture led us to assign it to Monotygma. It is the fourteenth Erythraean alien pyramidellid species recorded in the Levantine Basin. The large populations of a great number of Erythraean aliens in the Levantine Basin may serve as reservoir hosts for pyramidellids, many of which seem to be parasitic generalists, and may be introduced to native Mediterranean hosts.
  • Bolte, S., V. Fuentes, H. Haslob, B. Huwer, D. Thibault-Botha, D.L. Angel, B.S. Galil, J. Javidpour, A.G. Moss and T.B.H. Reusch. (2013). Population genetics of the invasive ctenophore Mnemiopsis leidyi in Europe reveal source-sink dynamics and secondary dispersal to the Mediterranean Sea. Marine Ecology Progress Series 485, 25-36. doi:10.3354/meps10321 http://www.int-res.com/abstracts/meps/v485/p25-36/
    View abstract Repeated invasions of European waters by the ctenophore Mnemiopsis leidyi offer a unique opportunity to study population dynamics and dispersal in gelatinous zooplankton. Here we followed population establishment in 2 recently invaded areas, the North and Baltic Seas, and analysed changes in population structure during a 3 yr interval using 7 highly polymorphic microsatellites comprising 191 alleles. A second goal was to reconstruct routes of recent invasive range expansion into the Mediterranean Sea. During the study period (2008 to 2010), populations in the North Sea and Western Baltic Sea maintained their allelic composition with virtually unchanged levels of genetic diversity and between-population differentiation, demonstrating limited gene flow between the 2 regions and successful reproduction in both areas. In contrast, at the eastern distribution limit in the central Baltic (Bornholm Basin), the same measures fluctuated between years and genetic diversity decreased from 2008 to 2010. In concordance with prior ecological observations, this supports the view that M. leidyi in the central Baltic is a sink population. In the area of recent range expansion (Mediterranean Sea), we observed high population differentiation: pairwise differentiation (FST ) values between sites in Spain, France and Israel were significant and between 0.04 and 0.16. Despite this differentiation, Bayesian clustering and phylogeographic analysis support the hypothesis that all Mediterranean M. leidyi result from a secondary introduction originating from the Black Sea. Our study contributes to growing evidence that multiple invasions of the same species can vary in their degree of genetic diversity and demonstrates how genetic markers can help to resolve whether gelatinous plankton species form self-sustaining populations.
  • Bastardie, F., J.R. Nielsen and T. Miethe. (2013). DISPLACE: a dynamic, individual-based model for spatial fishing planning and effort displacement - integrating underlying fish population models. Canadian Journal of Fisheries and Aquatic Sciences 71(3), 366-386. doi:10.1139/cjfas-2013-0126 http://dx.doi.org/10.1139/cjfas-2013-0126
    View abstract We previously developed an individual-based model evaluating the bio-economic efficiency of fishing vessel movements from recent high resolution spatial fishery data. The assumption was constant underlying resource availability. Now, an advanced version considers the underlying size-based dynamics of the targeted stocks for Danish and German vessels harvesting the North Sea and Baltic Sea fish stocks. The stochastic fishing process is specific to the vessel catching power and to the encountered population abundances, based on disaggregated research survey data. The impact of the effort displacement on the fish stocks and the vessels' economic consequences were evaluated by simulating individual choices of vessel speed, fishing grounds, and ports. Some scenarios led to increased energy efficiency and profit while others such as fishing closures or fishermen optimization sometimes lowered the revenue by altering the spatiotemporal effort allocation. On an individual scale, the simulations led to gains and losses due to either the interactions between vessels or to the alteration of individual patterns. We demonstrate that integrating the spatial activity of vessels and fish abundance dynamics allow for more realistic predictions of fishermen behaviour, profits, and stock abundance.
  • Batsleer, J., J.J. Poos, P. Marchal, Y. Vermard and A.D. Rijnsdorp. (2013). Mixed fisheries management: protecting the weakest link. Marine Ecology Progress Series 479, 177-190. http://www.int-res.com/abstracts/meps/v479/p177-190/
    View abstract North Sea cod Gadus morhua stock is outside safe biological limits, and total allowable catch (TAC) management has proved ineffective to rebuild the stock. The European Commission is considering the imposition of a discard ban to preserve vulnerable and economically important fish stocks. We explored the potential effects of a discard ban in mixed fisheries management using the French mixed fisheries in the Eastern English Channel as a model system. We examined in particular the performance of 2 different management scenarios: (1) individual quota management with a tolerance for discarding and (2) individual quota management in combination with a discard ban, using a dynamic state variable model. The model evaluates a time series of decisions taken by fishers to maximize profits within management constraints. Compliance to management was tested by applying an in-height varying fine for exceeding the quota. We then evaluated the consequences of individual cod quota in both scenarios with respect to over-quota discarding, spatial and temporal effort allocation and switching between métiers. Individual quota management without a discard ban hardly influenced fishers' behaviour as they could fully utilise cod quota and continue fishing other species while discarding cod. In contrast, a discard ban forced fishers to reallocate effort to areas and weeks in which cod catch is low, at the expense of lower revenue. In general, a restrictive policy for individual quota for cod needs to be combined with a discard ban and a high fine (>20 times the sale price) to reduce over-quota discarding.
  • Beare, D., A. McQuatters-Gollop, T. van der Hammen, M. Machiels, S.J. Teoh and J.M. Hall-Spencer. (2013). Long-term trends in calcifying plankton and pH in the North Sea. PLOS ONE 8(5), e61175. doi:doi:10.1371/journal.pone.0061175 http://dx.doi.org/10.1371/journal.pone.0061175
    View abstract Relationships between six calcifying plankton groups and pH are explored in a highly biologically productive and data-rich area of the central North Sea using time-series datasets. The long-term trends show that abundances of foraminiferans, coccolithophores, and echinoderm larvae have risen over the last few decades while the abundances of bivalves and pteropods have declined. Despite good coverage of pH data for the study area there is uncertainty over the quality of this historical dataset; pH appears to have been declining since the mid 1990s but there was no statistical connection between the abundance of the calcifying plankton and the pH trends. If there are any effects of pH on calcifying plankton in the North Sea they appear to be masked by the combined effects of other climatic (e.g. temperature), chemical (nutrient concentrations) and biotic (predation) drivers. Certain calcified plankton have proliferated in the central North Sea, and are tolerant of changes in pH that have occurred since the 1950s but bivalve larvae and pteropods have declined. An improved monitoring programme is required as ocean acidification may be occurring at a rate that will exceed the environmental niches of numerous planktonic taxa, testing their capacities for acclimation and genetic adaptation.
  • Karhan, S.U., M.B. Yokes, P.F. Clark and B.S. Galil. (2013). First Mediterranean record of Actaea savignii (H. Milne Edwards, 1834) (Crustacea: Decapoda: Brachyura: Xanthidae), an additional alien Erythraean crab. BioInvasions Records 2(2), 145-148. doi:10.3391/bir.2013.2.2.09 http://www.reabic.net/journals/bir/2013/2/BIR_2013_2_Karhan_etal.pdf
    View abstract To date, the only alien xanthid crab recorded from the Mediterranean is Atergatis roseus (Rüppell, 1830). This species was first collected off Israel in 1961 and is now common along the Levantine coast. Recently a second alien xanthid species, Actaea savignii (H. Milne Edwards, 1834), was found off Israel and Turkey. A single adult specimen was collected in Haifa Bay in 2010, and two specimens were captured off Mersin, Turkey in 2011. Repeatedly reported from the Suez Canal since 1924, the record of the Levantine populations of A. savignii is a testament to the ongoing Erythraean invasion of the Mediterranean Sea.
  • Kempf, A.J., V. Stelzenmüller, A. Akimova and J. Floeter. (2013). Spatial assessment of predator-prey relationships in the North Sea: the influence of abiotic habitat properties on the spatial overlap between 0-group cod and grey gurnard. Fisheries Oceanography 22(3), 174-192. doi:10.1111/fog.12013 http://dx.doi.org/10.1111/fog.12013
    View abstract The understanding of spatio-temporal dynamics of marine ecosystems is crucial for ecosystem-based fisheries management and climate change impact assessments. We quantified temporal changes in the distribution of 0-group cod (Gadus morhua) and grey gurnard (Eutriglia gurnardus), a primary predator of 0-group cod, with the help of regression kriging and assessed the temporal dynamics of the related spatial predator-prey overlap of these two species at different spatial scales. We analysed the robustness of relationships among abiotic habitat properties (temperature, salinity and depth) and abundance. Small cod was mainly found in low salinity areas of the Skagerrak but larger year classes were able to expand their distribution area towards the central and northern North Sea. In contrast, grey gurnard was mainly found in waters with salinities above 33 and temperatures above 14°C. This species has expanded its high density areas in the central North Sea northward over the last two decades. Recruitment success of cod was negatively correlated to a Moran's I cross-correlation index, a proxy for the degree of spatial overlap between both species. Strong cod year classes overlapped less with grey gurnard at the large and medium spatial scale. In general, the relationships between abiotic habitat properties and abundance showed an increased inter-annual variability, which was likely caused by underlying factors not taken into account in the distribution models. Thus assemblage modeling approaches combining the strength of different model types should be considered in the future to predict potential distribution patterns under climate change scenarios.
  • Kotta, J., M. Pärnoja, T. Katajisto, M. Lehtiniemi, S.A. Malavin, G. Reisalu and V.E. Panov. (2013). Is a rapid expansion of the invasive amphipod Gammarus tigrinus Sexton, 1939 associated with its niche selection: a case study in the Gulf of Finland, the Baltic Sea. Aquatic Invasions 8(3), 319-332. http://www.aquaticinvasions.net/2013/AI_2013_3_Kotta_etal.pdf
    View abstract Among the recent non-indigenous species the gammarid amphipod Gammarus tigrinus is one of the more aggressive invaders in the Baltic Sea. Quantitative sampling of the shallow water habitats of the Gulf of Finland showed that G. tigrinus has become established in the whole coastal zone of the Gulf. Boosted Regression Trees modelling indicated that the abundance and biomass of G. tigrinus varied as a function of wave exposure, water salinity and transparency, with the invasive amphipod having higher abundance and biomass at less exposed, more dilute, and more turbid sites. Gammarus tigrinus appears to be competitively superior to the native gammarids, possibly leading to further decline of the native gammarid populations in the Gulf of Finland.
  • Jones, M.C., S.R. Dye, J.A. Fernandes, T.L. Frölicher, J.K. Pinnegar, R. Warren and W.W.L. Cheung. (2013). Predicting the impact of climate change on threatened species in UK waters. PLOS ONE 8(1), e54216. doi:10.1371/journal.pone.0054216 http://dx.doi.org/10.1371%2Fjournal.pone.0054216
    View abstract Global climate change is affecting the distribution of marine species and is thought to represent a threat to biodiversity. Previous studies project expansion of species range for some species and local extinction elsewhere under climate change. Such range shifts raise concern for species whose long-term persistence is already threatened by other human disturbances such as fishing. However, few studies have attempted to assess the effects of future climate change on threatened vertebrate marine species using a multi-model approach. There has also been a recent surge of interest in climate change impacts on protected areas. This study applies three species distribution models and two sets of climate model projections to explore the potential impacts of climate change on marine species by 2050. A set of species in the North Sea, including seven threatened and ten major commercial species were used as a case study. Changes in habitat suitability in selected candidate protected areas around the UK under future climatic scenarios were assessed for these species. Moreover, change in the degree of overlap between commercial and threatened species ranges was calculated as a proxy of the potential threat posed by overfishing through bycatch. The ensemble projections suggest northward shifts in species at an average rate of 27 km per decade, resulting in small average changes in range overlap between threatened and commercially exploited species. Furthermore, the adverse consequences of climate change on the habitat suitability of protected areas were projected to be small. Although the models show large variation in the predicted consequences of climate change, the multi-model approach helps identify the potential risk of increased exposure to human stressors of critically endangered species such as common skate (Dipturus batis) and angelshark (Squatina squatina).
  • Janßen, H., C.B. Augustin, H.-H. Hinrichsen and K. S. (2013). Impact of secondary hard substrate on the distribution and abundance of Aurelia aurita in the western Baltic Sea. Marine pollution bulletin 75(1-2), 224-234. doi:10.1016/j.marpolbul.2013.07.027 http://dx.doi.org/10.1016/j.marpolbul.2013.07.027
    View abstract This study assessed the impact of secondary hard substrate, as being introduced into marine ecosystems by the establishment of wind farm pillars, on the occurrence and distribution of the moon jelly Aurelia aurita in the southwestern Baltic Sea. A two-year data sampling was conducted with removable settlement plates to assess the distribution and population development of the scyphozoan polyps. The data collected from these samples were used to set up a model with Lagrangian particle technique. The results confirm that anthropogenic created hard substrate (e.g. offshore wind farms) has the potential to increase the abundance of the A. aurita population. The distribution of wind farm borne jellyfish along Danish, German and Polish coasts indicates conflicts with further sectors, mainly energy and tourism.
  • Janßen, H., S. Kidd and T. Kvinge. (2013). A spatial typology for the sea: A contribution from the Baltic. Marine Policy 42, 190-197. doi:doi: 10.1016/j.marpol.2013.03.001 http://www.sciencedirect.com/science/article/pii/S0308597X13000699
    View abstract Marine spatial planning (MSP) has a need for spatial delimitation and for the identification of spatial classes. This paper reports on the findings of a pilot study that was undertaken to test the development of a data informed spatial typology for the Baltic Sea. The Baltic Sea is a comparatively shallow sea with nine adjoining countries and intense anthropogenic activities. The aim of the study was to assess the applicability and value of such a spatial typology for MSP. A spatial typology with seven different spatial classes was identified. The approach used here to identify a spatial typology could be used for seas worldwide.
  • Lehtiniemi, M., E. Gorokhova, S. Bolte, H. Haslob, B. Huwer, T. Katajisto, L. Lennuk, S. Majaneva, A. Põllumäe, M. Schaber, O. Setälä, T.B.H. Reusch, S. Viitasalo-Frösén, I. Vuorinen and P. Välipakka. (2013). Distribution and reproduction of the Arctic ctenophore Mertensia ovum in the Baltic Sea. Marine Ecology Progress Series 491, 111-124. doi:10.3354/meps10464 http://www.int-res.com/abstracts/meps/v491/p111-124/
    View abstract Species identification based on morphological characteristics has caused misidentifications and led to twisted views of abundances and roles of ctenophores. Based on extensive field studies from 2007 to 2010, the occurrence of the arctic ctenophore Mertensia ovum was genetically verified in the southern, central and northern Baltic Sea, and its egg production, distribution and abundance were studied in relation to physical factors. Genetic analyses indicate that M. ovum is by far the most abundant small ctenophore in the Baltic Sea. Specimens from a 20 yr old ctenophore collection were also genetically identified as M. ovum, contrary to their previous morphological identification as another ctenophore species, Pleurobrachia pileus. Thus, earlier reports on P. pileus in the Baltic Sea may actually refer to M. ovum. The abundance of M. ovum was regulated by both salinity and temperature, with highest abundances found in sea areas and water layers at temperatures less than 7°C, salinities greater than 5.5 and oxygen levels greater than 4 ml l-1. During summer, the highest abundances of ctenophores and their eggs were found near the halocline, while the distribution was more uniform throughout the water column during winter. Only ctenophores greater than 3.5 mm (oral-aboral length) produced eggs in the experiments, with an average rate of 2.2 eggs ind.-1 d-1. Finally, comparison with published data from the 1980s (assuming that those data refer to M. ovum) indicates that the present-day ctenophore abundance is ~80% lower in the north and ~55% higher in the southern parts of the Baltic Sea, due to reasons yet to be established.
  • Jones, M.C., S.R. Dye, J.K. Pinnegar, R. Warren and W.W.L. Cheung. (2013). Applying distribution model projections for an uncertain future: the case of the Pacific oyster in UK waters. Aquatic Conservation: Marine and Freshwater Ecosystems 23(5), 710-722. doi:10.1002/aqc.2364 http://dx.doi.org/10.1002/aqc.2364
    View abstract The inherent complexity of the environment is such that attempts to model it must operate under simplifications and assumptions. Considering predictions from alternative models, with a range of assumptions and data requirements, therefore provides a more robust approach. The intractability and uncertainty resulting from a suite of predictions may hinder the application of science in policy, where a single prediction with little ambiguity or uncertainty would be most desirable. Few studies modelling species' distributions attempt to present multi-model outputs in a format most useful to the non-modelling community, and none of these have done so for the marine environment. The problem of uncertainty is particularly prevalent in predicting the distribution of invasive alien species under climate change. As invasive alien species are one of the main drivers of biodiversity loss and may incur significant economic costs, the benefit of applying predictions to highlight areas of possible establishment and inform policy and management may be large. An ensemble prediction is used to assess the distribution of suitable habitat for the Pacific oyster, Crassostrea gigas, in UK waters both currently and in the future. The ensemble incorporates predictions from three species distribution models, using data from two global climate models. A method is developed highlighting the agreement of the ensemble, further applying threshold values to retain information from constituent predictions in the final map of agreement. Ensemble predictions made here suggest that Pacific oyster will experience an opening of suitable habitat in northern UK waters, reaching the Faroe Islands and the eastern Norwegian Sea by 2050. Habitat suitability will increase with warming temperatures in the English Channel and Central North Sea for this species. The approaches applied here can be incorporated into risk assessment frameworks for invasive species, as stipulated in the Convention on Biological Diversity.
  • Loureiro, M.L. and J.B. Loomis. (2013). International public preferences and provision of public goods: assessment of passive use values in large oil spills. Environmental and Resource Economics 56(4), 521-534. doi:10.1007/s10640-012-9556-4 http://dx.doi.org/10.1007/s10640-012-9556-4
    View abstract With global media reporting major environmental disasters, environmental damages linked to large oil spills may go well beyond the territorial limits of affected countries, particularly in the case of passive use values. In this analysis, we compare environmental damages linked a large oil spill off the coast of Spain using an online contingent valuation survey in three different European countries: Spain, UK, and Austria. Our results show that mean willingness to pay in Spain is about 124.37 Euros/household, 80.87 Euros/household in the UK, and 89.08 Euros/household for Austria (expressed in 2009 prices). Conclusions and implications of our results suggest policy makers should consider the potential importance of passive use values in the compensation process of environmental damages caused by large international oil spills, especially within the European Union.
  • Leone, A., R.M. Lecci, M. Durante and S. Piraino. (2013). Extract from zooxanthellate jellyfish Cotylorhiza tuberculata modulates gap junction intercellular communication in human cell cultures. Marine Drugs 11, 1728-1762. http://www.mdpi.com/1660-3397/11/5/1728
    View abstract On a global scale, jellyfish populations in coastal marine ecosystems exhibit increasing trends of abundance. High-density outbreaks may directly or indirectly affect human economical and recreational activities, as well as public health. As the interest in biology of marine jellyfish grows, a number of jellyfish metabolites with healthy potential, such as anticancer or antioxidant activities, is increasingly reported. In this study, the Mediterranean 'fried egg jellyfish' Cotylorhiza tuberculata (Macri, 1778) has been targeted in the search forputative valuable bioactive compounds. A medusa extract was obtained, fractionated, characterized by HPLC, GC-MS and SDS-PAGE and assayed for its biological activity on breast cancer cells (MCF-7) and human epidermal keratinocytes (HEKa). The composition of the jellyfish extract included photosynthetic pigments, valuable ω-3 and ω-6 fatty acids, and polypeptides derived either from jellyfish tissues and their algal symbionts. Extract fractions showed antioxidant activity and the ability to affect cell viability and intercellular communication mediated by gap junctions (GJIC) differentially in MCF-7and HEKa cells. A significantly higher cytotoxicity and GJIC enhancement in MCF-7 compared to HEKa cells was recorded. A putative action mechanism for the anticancer bioactivity through the modulation of GJIC has been hypothesized and its nutraceutical and pharmaceutical potential was discussed.
  • Maar, M., E.F. Møller, Z. Gürkan, S.H. Jónasdóttir and T.G. Nielsen. (2013). Sensitivity of Calanus spp. copepods to environmental changes in the North Sea using life-stage structured models. Progress in Oceanography 111, 24-37. http://www.sciencedirect.com/science/article/pii/S0079661112001280
    View abstract The copepods Calanus finmarchicus and Calanus helgolandicus co-exist in the North Sea, but their spatial distribution and phenology are very different. Long-term changes in their distributions seem to occur due to climate change resulting in a northward extension of C. helgolandicus and a decline of C. finmarchicus in this region. The aim of this study is to use life-stage structured models of the two Calanus species embedded in a 3D coupled hydrodynamic-biogeochemical model to investigate how the biogeography of C. finmarchicus and C. helgolandicus is modified by changes in ±2°C sea water temperatures, overwintering and oceanic inflow in the North Sea. Life-stage structured models are validated against CPR data and vertical distributions north of the Dogger Bank in the North Sea for the reference year 2005. The model shows that (1) ±2°C changes from the current level mainly influence the seasonal patterns and not the relative occurrence of the two species, (2) changes due to oceanic inflow mainly appeared in the northern and southern part of the North Sea connected to the NE Atlantic and not in the central part and (3) the abundance of Calanus species were very sensitive to the degree of overwintering within the North Sea because it allows them to utilise the spring bloom more efficiently and independently of the timing and amount of oceanic inflow. The combination of lower temperatures, higher overwintering and oceanic inflow simulating the situation in the 1960s largely favoured C. finmarchicus and their relative contribution to Calanus spp. increased from 40% in the reference year to 72%. The +2°C scenario suggest that in a warmer future, C. finmarchicus is likely to decline and C. helgolandicus abundance will probably continue to increase in some areas.
  • Magni, P., S. Rajagopal, S. Como, J.M. Jansen, G. van der Velde and H. Hummel. (2013). δ13C and δ15N variations in organic matter pools, Mytilus spp. and Macoma balthica along the European Atlantic coast. Marine Biology 160(3), 541-552. http://link.springer.com/article/10.1007/s00227-012-2110-7
    View abstract Stable carbon (δ13C) and nitrogen (δ15N) isotope (SI) values of sedimentary organic matter (SOM), seston and two dominant bivalves, Mytilus spp. and Macoma balthica, were studied at 18 stations along the European coast in spring and autumn 2004. Three main regions, the Baltic Sea (BS), the North Sea and English Channel (NS), and the Bay of Biscay (BB), were tested for possible geographic (latitudinal) differences in the SI values. In spring, only BS showed lower d 13C values of seston and Mytilus spp., and higher δ15N values of SOM, than NS and BB. No significant differences between the 3 regions were found in autumn. Irrespective of season and regions, Mytilus spp. was more 13C-depleted than M. balthica. δ13C values of M. balthica, but not those of Mytilus spp., were significantly correlated with SOM. These results are consistent with differences in feeding behavior of Mytilus spp. and M. balthica, as the two species are known as obligatory-suspension and facultative-deposit feeders, respectively. In contrast, no differences in the δ15N values of Mytilus spp. and M. balthica were found at individual stations, indicating the same trophic level of the two bivalves within the food webs. At some stations, irrespective of geographic location, both bivalves showed δ15N values up to 18-20‰. These were two trophic levels higher than those found at the other stations, indicating local and/or episodic eutrophic conditions, probably due to waste water discharge, and the effectiveness of both Mytilus spp. and M. balthica as bio-indicators of anthropogenic eutrophication. Overall, our results suggest that pathways of energy flow from OM pools to dominant bivalves is more related to local environmental conditions than to geographic regions across the European coastline. This has implications for food web studies along the Atlantic coast because most of the values are consistent over a large area and show no significant differences. Therefore, the present study can be used twofold for the determination of trophic baselines and for the correction of the trophic position of consumers higher up in the food web in the case of differences in waste water discharge.
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