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Artificial reefs are used to protect coastal habitats and rebuild fisheries. This engineering approach to fisheries management has gained popularity in many coastal areas, including China. In Shandong province alone, over USD 50 million were invested in artificial reefs during 2005–2013. Have artificial reefs achieved their biological and economic objectives? We compared reef and control sites in terms of catch and value per unit effort and average body length across species, based on surveys carried out during 2012–2013. We found that in aggregate, with all fish and invertebrates combined, artificial reefs did not improve the overall catches or revenues. Instead, seasonal fluctuations were prominent. However, when we allow for species-specific differences and focus on the common fish species, we find that an artificial reef can increase the catch and value per unit effort on average by approximately 40% compared to the control sites. The difference between these contrasting results occurs because some of the dominant species that comprise the bulk of the catches did not benefit from the reef, while many of the less dominant ones did so. This underlines the importance of being specific about what is meant by “benefiting fisheries” when evaluating artificial reefs, as well as when the objectives of reef projects are formulated in the first place. The positive effects of artificial reefs can be caused by the reefs themselves and by their influence on fishing patterns. Our study was not designed to separate these effects but we suggest that in Shandong, restrictions on fishing access may have been as important as the presence of the reef itself.

13 pages, 7 figures, 2 tables, Water homeostasis and the structural integrity of the vertebrate lens is partially mediated by AQP0 channels. Emerging evidence indicates that external pH may be involved in channel gating. Here we show that a tetraploid teleost, the Atlantic salmon, retains 4 aqp0 genes (aqp0a1, -0a2, -0b1, and -0b2), which are highly, but not exclusively, expressed in the lens. Functional characterization reveals that, although each paralog permeates water efficiently, the permeability is respectively shifted to the neutral, alkaline, or acidic pH in Aqp0a1, -0a2, and -0b1, whereas that of Aqp0b2 is not regulated by external pH. Mutagenesis studies demonstrate that Ser, His, and His residues in the extracellular transmembrane domain of a-helix 2 facing the water pore are critical for the pH modulation of water transport. To validate these findings, we show that both zebrafish Aqp0a and -0b are functional water channels with respective pH sensitivities toward alkaline or acid pH ranges and that an N-terminal allelic variant (Ser) of Aqp0b exists that abolishes water transport in Xenopus laevis oocytes. The data suggest that the alkaline pH sensitivity is a conserved trait in teleost Aqp0 a-type channels, whereas mammalian AQP0 and some teleost Aqp0 b-type channels display an acidic pH permeation preference. © The Author(s), This work was supported by Research Council of Norway (RCN) Projects 224816/E40 and 178837/40 (to R.N.F.), and Spanish Ministry of Science and Innovation (MICINN) Grant AGL2010-15597 (to J.C.). F.C. and J.A.S. were supported by postdoctoral fellowships from the RCN (224816/E40 and 178837/40, respectively); C.Z. was supported by a predoctoral fellowship (FPI) from MICINN

Deep-sea hydrothermal vents and cold seeps are biological hot spots with chemolithotrophic bacterial production sustaining both benthic and pelagic organisms. Although efforts have been made to understand the diversity and function of the bacterial composition of these systems, first-level consumers, pelagic single cell heterotrophic organisms, which represent an important link between bacterial production and higher trophic levels, remain un-described in hydrothermal vents and seeps of the Nordic Seas. Here, we used a molecular biodiversity assay to investigate the impact of water masses and hydrothermal vents on the eukaryotic micro-organisms surrounding two vents systems, Jan Mayen Vent Field and Loki`s Castle, and one cold seep, Hakon Mosby Mud Volcano. The assay generated a total of 482 operational taxonomic units (OTUs) based on a 99 % cut-off value, and the OTUs were grouped according to taxonomic rank. Data analysis using hierarchical clustering and non-metric multidimensional scaling with class as taxonomic entries suggested that water masses followed by depth was the dominant effect on eukaryotic micro-organism diversity. However, in one of the vent systems, Loki`s Castle, the community was different compared to the reference station. Our data suggest that while the total production of vent systems is higher than the surrounding waters, the biodiversity of eukaryotic micro-organisms is more influenced by both water masses and depth.

Mitra, Aditee ... et. al.-- 11 pages, 6 figures, The traditional view of the planktonic food web describes consumption of inorganic nutrients by photoautotrophic phytoplankton, which in turn supports zooplankton and ultimately higher trophic levels. Pathways centred on bacteria provide mechanisms for nutrient recycling. This structure lies at the foundation of most models used to explore biogeochemical cycling, functioning of the biological pump, and the impact of climate change on these processes. We suggest an alternative new paradigm, which sees the bulk of the base of this food web supported by protist plankton communities that are mixotrophic-combining phototrophy and phagotrophy within a single cell. The photoautotrophic eukaryotic plankton and their heterotrophic microzooplankton grazers dominate only during the developmental phases of ecosystems (e.g. spring bloom in temperate systems). With their flexible nutrition, mixotrophic protists dominate in more-mature systems (e.g. temperate summer, established eutrophic systems and oligotrophic systems); the more-stable water columns suggested under climate change may also be expected to favour these mixotrophs. We explore how such a predominantly mixotrophic structure affects microbial trophic dynamics and the biological pump. The mixotroph-dominated structure differs fundamentally in its flow of energy and nutrients, with a shortened and potentially more efficient chain from nutrient regeneration to primary production. Furthermore, mixotrophy enables a direct conduit for the support of primary production from bacterial production. We show how the exclusion of an explicit mixotrophic component in studies of the pelagic microbial communities leads to a failure to capture the true dynamics of the carbon flow. In order to prevent a misinterpretation of the full implications of climate change upon biogeochemical cycling and the functioning of the biological pump, we recommend inclusion of multi-nutrient mixotroph models within ecosystem studies. © 2014 Author(s), A. Calbet was partially supported by the Ministry of Science and Innovation of Spain through project PROTOS (CTM2009-08783). A. Mitra was supported in part by project EURO-BASIN (Ref. 264933, 7FP, European Union). D. K. Stoecker was partially supported by NSF award 1031344. J. Hawkey assisted with graphic preparation. A. Mitra thanks Rohan Mitra-Flynn for his continuing support. This is contribution number 4789 from UMCES. The University of Dundee is a registered charity, no. SC010596

We explore the trophic ecology of heterotrophic fauna associated with a high temperature (HT) vent, 2 low temperature vents, a ‘near-HT vent’ habitat and a non-vent site situated at upper bathyal depths on the southern Mohn’s Ridge in the Arctic Ocean. Only a single taxon (the gastropod Pseudosetia griegi) was found at the high temperature vent habitat. Their mean δ13C values were significantly lighter than conspecifics from a low temperature vent habitat within the same vent field, reflecting the incorporation of sulfide oxidizing bacteria into the biomass of the animals. The majority of fauna from the low temperature, near-HT, and non-vent habitats had isotopic signatures indicative of assimilation of photosynthetic material. However, we found remarkably diverse isotopic compositions among the fauna sampled here, with a small sub-set of fauna at each site possessing C and N isotopic signatures indicative of incorporation of chemo - synthetic production. Moreover, when isotopic signatures of similar taxa were compared from the same sample, δ13C signatures suggested a high degree of trophic complexity can exist over relatively small spatial scales at vent habitats on the southern Mohn’s Ridge. The high contribution of photosynthetic food material to faunal diets and variability in food types may result from the upper bathyal venting depth and sedimentary nature of the vents. We hypothesize that the upper bathyal depth of active venting may lead to iron enhancement of surface photosynthetic production, especially in high nutrient areas, which ultimately sinks to the seabed where it is incorporated by fauna around the vents. publishedVersion

Recent studies have shown that crude oil exposure affects cardiac development in fish by disrupting excitation-contraction (EC) coupling. We previously found that eggs of Atlantic haddock (Melanogrammus aeglefinus) bind dispersed oil droplets, potentially leading to more profound toxic effects from uptake of polycyclic aromatic hydrocarbons (PAHs). Using lower concentrations of dispersed crude oil (0.7–7 μg/L ∑PAH), here we exposed a broader range of developmental stages over both short and prolonged durations. We quantified effects on cardiac function and morphogenesis, characterized novel craniofacial defects, and examined the expression of genes encoding potential targets underlying cardiac and craniofacial defects. Because of oil droplet binding, a 24-hr exposure was sufficient to create severe cardiac and craniofacial abnormalities. The specific nature of the craniofacial abnormalities suggests that crude oil may target common craniofacial and cardiac precursor cells either directly or indirectly by affecting ion channels and intracellular calcium in particular. Furthermore, down-regulation of genes encoding specific components of the EC coupling machinery suggests that crude oil disrupts excitation-transcription coupling or normal feedback regulation of ion channels blocked by PAHs. These data support a unifying hypothesis whereby depletion of intracellular calcium pools by crude oil-derived PAHs disrupts several pathways critical for organogenesis in fish.

Normal 0 21 false false false NO-BOK X-NONE X-NONE The bone-eating siboglinid polychaete Osedax mucofloris Glover, Kallstrom, Smith & Dahlgren, 2005 is reported from Norwegian waters for the first time. Dense growth was found on bovine bones deposited at 118 meters depth off western Norway. Dwarf males were observed for the first time. The two specimens sequenced were identical to haplotypes previously found at a Swedish whale fall. The possibility of finding additional species of Osedax is discussed.

Calbet, Albert ... et al.-- 14 pages, 12 figures, 3 tables, Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioural aggregation. Simulating a mixing event by adding nutrient-rich deep water abruptly triggered dense phytoplankton blooms in the nutrient-poor environment of the upper layer. These findings suggest that vertical structures within the mixed layer provide critical seeding stocks that can rapidly exploit nutrient influx during mixing, leading to winter bloom formation, This study was funded by King Abdullah University of Science and Technology, and project PROTOS (CTM2009-08783) from the Ministry of Science and Innovation of Spain to AC

International audience; Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from two annual cycles, with the taxonomic resolution and sampling depth obtained with high-throughput sequencing. From outer Oslofjorden, S Norway, nano- and picoplanktonic samples were collected monthly for 2years, and the haptophytes targeted by amplification of RNA/cDNA with Haptophyta-specific 18S rDNA V4 primers. We obtained 156 operational taxonomic units (OTUs), from c. 400.000 454 pyrosequencing reads, after rigorous bioinformatic filtering and clustering at 99.5%. Most OTUs represented uncultured and/or not yet 18S rDNA-sequenced species. Haptophyte OTU richness and community composition exhibited high temporal variation and significant yearly periodicity. Richness was highest in September-October (autumn) and lowest in April-May (spring). Some taxa were detected all year, such as Chrysochromulina simplex, Emiliania huxleyi and Phaeocystis cordata, whereas most calcifying coccolithophores only appeared from summer to early winter. We also revealed the seasonal dynamics of OTUs representing putative novel classes (clades HAP-3-5) or orders (clades D, E, F). Season, light and temperature accounted for 29% of the variation in OTU composition. Residual variation may be related to biotic factors, such as competition and viral infection. This study provides new, in-depth knowledge on seasonal diversity and dynamics of haptophytes in North Atlantic coastal waters. See also the Perspective by Massana

The order Mysida (2 families, 178 genera, 1132 species) contains species across a broad range of habitats, such as subterranean, fresh, brackish, coastal, and surface to deep-sea habitats. The Stygiomysida (2 families, 2 genera, 16 species), however, are found primarily in subterranean waters, but always in waters with a marine influence. The Mysida and Stygiomysida body is divided into three main regions: cephalon, thorax, and abdomen. They are shrimp-like in appearance, containing morphological features earlier referred to as defining a "caridoid facies". The shrimp-like morphology was to some extent diagnostic for the historic Decapod taxon Schizopoda, containing the Nebalia, Mysida, Lophogastrida, and Euphausiacea. In 1904 the concept of Schizopoda was abandoned, and the Mysidacea (Mysida and Lophogastrida) along with Cumacea, Amphipoda, Isopoda, and Tanaidacea were placed in a new taxon, the Peracarida. Later discoveries of groundwater mysids led to the establishment of Stygiomysida, but placement to either Lophogastrida or Mysida remained unclear. The presence of oostegites and absence of podobranchiae, coupled with non-statocyst bearing uropods have been used to classify the Stygiomysida as a primitive Mysida family, comparable to Petalophthalmidae. On the other hand, equally suggestive characters, but for a Lophogastrida affiliation, was suggested for the archaic foregut characters and again, non-statocyst bearing uropods. With the inclusion of DNA sequence data of ribosomal genes, sister group relationships between Stygiomysida, Lophogastrida, and Mictacea within the Peracarida are observed, which supports a classification of the Stygiomysida as a separate order removed from the Mysida. publishedVersion

This study evaluates long-term mean fluxes of carbon and nutrients to the upper 100 m of the Iceland Sea. The study utilises hydro-chemical data from the Iceland Sea time series station (68.00° N, 12.67° W), for the years between 1993 and 2006. By comparing data of dissolved inorganic carbon (DIC) and nutrients in the surface layer (upper 100 m), and a sub-surface layer (100–200 m), we calculate monthly deficits in the surface, and use these to deduce the long-term mean surface layer fluxes that affect the deficits: vertical mixing, horizontal advection, air–sea exchange, and biological activity. The deficits show a clear seasonality with a minimum in winter, when the mixed layer is at the deepest, and a maximum in early autumn, when biological uptake has removed much of the nutrients. The annual vertical fluxes of DIC and nitrate amounts to 2.9 ± 0.5 and 0.45 ± 0.09 mol m−2 yr−1, respectively, and the annual air–sea uptake of atmospheric CO2 is 4.4 ± 1.1 mol C m−2 yr−1. The biologically driven changes in DIC during the year relates to net community production (NCP), and the net annual NCP corresponds to export production, and is here calculated as 7.3 ± 1.0 mol C m−2 yr−1. The typical, median C : N ratio during the period of net community uptake is 9.0, and clearly higher than the Redfield ratio, but is varying during the season. &nbsp

It is generally accepted that the high buoyancy of pelagic marine eggs is due to substantial influx of water across the cell membrane just before ovulation. Here we further develop the theoretical basis by applying laboratory observations of the various components of the fertilized egg in first-principle equations for egg specific gravity (ρegg) followed by statistical validation. We selected Atlantic cod as a model animal due to the affluent amount of literature on this species, but also undertook additional dedicated experimental works. We found that specific gravity of yolk plus embryo is central in influencing ρegg and thereby the buoyancy. However, our established framework documents the effect on ρegg of the initial deposition of the heavy chorion material in the gonad prior to spawning. Thereafter, we describe the temporal changes in ρegg during incubation: Generally, the eggs showed a slight rise in ρegg from fertilization to mid-gastrulation followed by a gradual decrease until full development of main embryonic organs just before hatching. Ontogenetic changes in ρegg were significantly associated with volume and mass changes of yolk plus embryo. The initial ρegg at fertilization appeared significantly influenced by the chorion volume fraction which is determined by the combination of the final chorion volume of the oocyte and of the degree of swelling (hydrolyzation) prior to spawning. The outlined principles and algorithms are universal in nature and should therefore be applicable to fish eggs in general. publishedVersion

Several phenomenological descriptions, such as the von Bertalanffy growth model, have been widely used to describe size-at-age and individual growth across a diverse range of organisms. However, for modelling life histories, as opposed to just growth, biologically and mechanistically meaningful growth models, based on allocation decisions, have become increasingly important. This is because fitness is determined by survival and reproduction, which are not addressed directly in phenomenological growth models. To elucidate these considerations, we take as a starting point the biphasic growth model by Quince et al. (2008a, J. Theor. Biol. 254:197) which has the advantage that the underlying allometric scaling of net energy intake can be freely chosen. First, we reformulate this model such that individual size is given in meaningful units of length and weight, facilitating the model's interpretation and application. Second, we show that even though different allometric scaling relationships can produce practically identical growth trajectories, the accompanying reproductive investments are highly dependent on the chosen allometric exponent. Third, we demonstrate how this dependence has dramatic consequences for evolutionary predictions, in particular with regard to the age and size at maturation. These findings have considerable practical relevance, because empirically observed allometric exponents are often uncertain and systematically differ from those assumed in current standard growth models. & 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

The mechanisms by which phytoplankton cope with stressors in the marine environment are neither fully characterized nor understood. As viruses are the most abundant entities in the global ocean and represent a strong top-down regulator of phytoplankton abundance and diversity, we sought to characterize the cellular response of two marine haptophytes to virus infection in order to gain more knowledge about the nature and diversity of microalgal responses to this chronic biotic stressor. We infected laboratory cultures of the haptophytes Haptolina ericina and Phaeocystis pouchetii with CeV-01B or PpV-01B dsDNA viruses, respectively, and assessed the extent to which host cellular responses resemble programmed cell death (PCD) through the activation of diagnostic molecular and biochemical markers. Pronounced DNA fragmentation and activation of cysteine aspartate-specific proteases (caspases) were only detected in virus-infected cultures of these phytoplankton. Inhibition of host caspase activity by addition of the pan-caspase inhibitor z-VAD-fmk did not impair virus production in either host–virus system, differentiating it from the Emiliania huxleyi-Coccolithovirus model of haptophyte–virus interactions. Nonetheless, our findings point to a general conservation of PCD-like activation during virus infection in ecologically diverse haptophytes, with the subtle heterogeneity of cell death biochemical responses possibly exerting differential regulation on phytoplankton abundance and diversity. publishedVersion

The temporal and spatial dynamics of primary and secondary biomass/production in the Barents Sea since the late 1990s are examined using remote sensing data, observations and a coupled physical-biological model. Field observations of mesozooplankton biomass, and chlorophyll a data from transects (different seasons) and large-scale surveys (autumn) were used for validation of the remote sensing products and modeling results. The validation showed that satellite data are well suited to study temporal and spatial dynamics of chlorophyll a in the Barents Sea and that the model is an essential tool for secondary production estimates. Temperature, open water area, chlorophyll a, and zooplankton biomass show large interannual variations in the Barents Sea. The climatic variability is strongest in the northern and eastern parts. The moderate increase in net primary production evident in this study is likely an ecosystem response to changes in climate during the same period. Increased open water area and duration of open water season, which are related to elevated temperatures, appear to be the key drivers of the changes in annual net primary production that has occurred in the northern and eastern areas of this ecosystem. The temporal and spatial variability in zooplankton biomass appears to be controlled largely by predation pressure. In the southeastern Barents Sea, statistically significant linkages were observed between chlorophyll a and zooplankton biomass, as well as between net primary production and fish biomass, indicating bottom-up trophic interactions in this region. publishedVersion

Calbet, Albert ... et. al.-- 16 pages, figures, 2 tables, We studied the effects of future climate change scenarios on plankton communities of a Norwegian fjord using a mesocosm approach. After the spring bloom, natural plankton were enclosed and treated in duplicates with inorganic nutrients elevated to pre-bloom conditions (N, P, Si; eutrophication), lowering of 0.4 pH units (acidification), and rising 3uC temperature (warming). All nutrient-amended treatments resulted in phytoplankton blooms dominated by chain-forming diatoms, and reached 13–16 mg chlorophyll (chl) a l21. In the control mesocosms, chl a remained below 1 mg l21. Acidification and warming had contrasting effects on the phenology and bloom-dynamics of autotrophic and heterotrophic microplankton. Bacillariophyceae, prymnesiophyceae, cryptophyta, and Protoperidinium spp. peaked earlier at higher temperature and lower pH. Chlorophyta showed lower peak abundances with acidification, but higher peak abundances with increased temperature. The peak magnitude of autotrophic dinophyceae and ciliates was, on the other hand, lowered with combined warming and acidification. Over time, the plankton communities shifted from autotrophic phytoplankton blooms to a more heterotrophic system in all mesocosms, especially in the control unaltered mesocosms. The development of mass balance and proportion of heterotrophic/autotrophic biomass predict a shift towards a more autotrophic community and less-efficient food web transfer when temperature, nutrients and acidification are combined in a future climate-change scenario. We suggest that this result may be related to a lower food quality for microzooplankton under acidification and warming scenarios and to an increase of catabolic processes compared to anabolic ones at higher temperatures., This research was funded through the projects BIOPUMP (EMT) and CYCLE from MESOAQUA -EU FP7-INFRA-2008-1, 228224 to (M. Winder & group members), the Norwegian Research Council grant NFR-HK 2024040/E40 (EMT), the project PROTOS (CTM2009-08783), and TopCop (CTM2011-23480) from the Ministry of Science and Innovation (AC). HHJ received financial support from the VELUX foundation (grant VKR022608). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Til arbeidet med etablering av Jomfruland nasjonalpark har NIVA fått i oppdrag å sammenstille kunnskap om marine naturverdier, med særlig vekt på naturtyper med st or økologisk verdi. De viktigste naturtypene er pr esentert i kart og tabeller med over sikt over størrelse og betydning . I tillegg er naturtypenes viktig e økologisk e funksjon er beskrevet. Nasjonalparkområdet omfatter spesielt store og rike tareskogsområder som har betydning for hele området s kystøkosysteme r og ressurser , og som også bidrar med viktige økosystemtjenester for område r utenfor nasjonalparken . Rapporten har i tillegg hovedfokus på naturtypene å legras enger , bløtbunn sområder i strandsonen , skjellsandforekomster , israndsavsetninger og gyteområder for fisk, men også andre marine naturverdier er beskrevet . Rapporten diskuterer mulige trusler for de marine naturverdiene i nasjonalparken og foreslår nord/nordøstsiden av Jomfruland som et aktuelt område for å overvåke naturverdienes helsetilstand Fylkesmannen i Telemark

Naturindeksens indikatorverdi for stortare har til nå blitt rapportert som prosentandelen av artens (naturtypens) utbredelse innen et gitt område som er antatt å ha naturtilstand. Vårt mål i dette utviklingsprosjektet har vært å utvikle en indikator for stortare som fanger opp både det biologiske mangfoldet og den økologiske funksjonen til stortare basert på tarens størrelse og forekomst av funksjonelle grupper som påvekstalger og tilhørende fauna. For å undersøke dette har vi utført en gjennomgang av tilgjengelig litteratur og kunnskap om stortaren og dens assosierte biologiske mangfold. I tillegg har vi har sammenstilt eksisterende data og avdekket hvilke områder som mangler data. Viktige datamangler ble dekket gjennom nye feltinnsamlinger på flere lokaliteter fra Sørlandet til Finnmark sommeren 2012. Vi har presentert en rekke parametere og miljøvariable som kan være viktig for tareskogens økologiske funksjon og kommet fram til hvilke mål som er mest hensiktsmessig å gjøre for på en praktisk gjennomførbar måte å komme fram til en indeks. En indikator for stortare bør fange opp framtidige endringer og forskyvninger i vekst og utbredelse gitt endringer i viktige påvirkningsfaktorer som klima, høsting, eutrofiering eller kråkebollebeiting. Gjennomgangen av eksisterende kunnskap sammen med nye data viste at dersom vi kan estimere naturlig habitatstørrelse for stortaren (i et upåvirket miljø) og mengden av de viktige påvekstalgene i ulike økoregioner, på ulike dyp og gitt ulik grad av bølgepåvirkning, så har vi et solid grunnlag for å kunne utvikle en samlet indeks for stortarens betydning for biologisk mangfold og økologiske funksjon.......... (utvidet sammendrag er å finne i rapporten) Direktoratet for naturforvaltning

Net community production (NCP) and carbon to nutrient uptake ratios were studied during a large-scale mesocosm experiment on ocean acidification in Kongsfjorden, western Svalbard, during June–July 2010. Nutrient depleted fjord water with natural plankton assemblages, enclosed in nine mesocosms of ~ 50 m3 in volume, was exposed to pCO2 levels ranging initially from 185 to 1420 μatm. NCP estimations are the cumulative change in dissolved inorganic carbon concentrations after accounting for gas exchange and total alkalinity variations. Stoichiometric coupling between inorganic carbon and nutrient net uptake is shown as a ratio of NCP to a cumulative change in inorganic nutrients. Phytoplankton growth was stimulated by nutrient addition half way through the experiment and three distinct peaks in chlorophyll a concentration were observed during the experiment. Accordingly, the experiment was divided in three phases. Cumulative NCP was similar in all mesocosms over the duration of the experiment. However, in phases I and II, NCP was higher and in phase III lower at elevated pCO2. Due to relatively low inorganic nutrient concentration in phase I, C : N and C : P uptake ratios were calculated only for the period after nutrient addition (phase II and phase III). For the total post-nutrient period (phase II + phase III) ratios were close to Redfield, however they were lower in phase II and higher in phase III. Variability of NCP, C : N and C : P uptake ratios in different phases reflects the effect of increasing CO2 on phytoplankton community composition and succession. The phytoplankton community was composed predominantly of haptophytes in phase I, prasinophytes, dinoflagellates, and cryptophytes in phase II, and haptophytes, prasinophytes, dinoflagellates and chlorophytes in phase III (Schulz et al., 2013). Increasing ambient inorganic carbon concentrations have also been shown to promote primary production and carbon assimilation. For this study, it is clear that the pelagic ecosystem response to increasing CO2 is more complex than that represented in previous work, e.g. Bellerby et al. (2008). Carbon and nutrient uptake representation in models should, where possible, be more focused on individual plankton functional types as applying a single stoichiometry to a biogeochemical model with regard to the effect of increasing pCO2 may not always be optimal. The phase variability in NCP and stoichiometry may be better understood if CO2 sensitivities of the plankton's functional type biogeochemical uptake kinetics and trophic interactions are better constrained.

Hardangerfjord is the second largest fjord in Norway and is situated on the southwest coast. During the last century the fjord has been influenced by a variety of anthropogenous activities such as industry, hydro-electrical power plants and since 1980 an increase in fish farming. This study was carried out in order to investigate whether changes in the macroalgal communities of Hardangerfjord have taken place since the 1950s. The macroalgal composition at a number of stations investigated in 2008–2009 was compared to recordings from the same stations during the 1950s. While the distribution and abundance of dominant groups (fucoids, kelps) showed a high resilience when compared to recordings from the 1950s, some changes in the macroalgal communities in the fjord were evident. The present study showed higher species richness and a higher frequency of species with a warm-water affinity. Since the first part of the 1990s an increase in summer sea surface temperatures has taken place in the area, and the observed algal changes suggest a pronounced temperature effect on macroalgal communities. A number of red algal species was observed to protrude further into the fjord in the present study than in the 1950s, probably caused by altered salinity regime due to the electrical power industry. publishedVersion

The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to describe the fine scale vertical distribution of Mnemiopsis leidyi in the Kattegat and Baltic Proper. Potential diel vertical migration was also investigated by frequent filming during a 24-hour cycle at two contrasting locations with respect to salinity stratification. The video profiles revealed a pronounced diel vertical migration at one of the locations. However, only the small and medium size classes migrated, on average 0.85 m h-1, corresponding to a total migration distance of 10 m during 12 h. Larger individuals (with well developed lobes, approx. >27 mm) stay on average in the same depth interval at all times. Biophysical data suggest that migrating individuals likely responded to light, and avoided irradiance levels higher than approx. 10 µmol quanta m-2 s-1. We suggest that strong stratification caused by low surface salinity seemed to prohibit vertical migration. publishedVersion