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Ecological Drivers of Mercury Bioaccumulation in Fish of a Subarctic Watercourse
Get PDFMercury (Hg) is a serious concern for aquatic ecosystems because it may biomagnify to harmful concentrations within food webs and consequently end up in humans that eat fish. However, the trophic transfer of mercury through the aquatic food web may be impacted by several factors related to network complexity and the ecology of the species present. The present study addresses the interplay between trophic ecology and mercury contamination in the fish communities of two lakes in a pollution-impacted subarctic watercourse, exploring the role of both horizontal (feeding habitat) and vertical (trophic position) food web characteristics as drivers for the Hg contamination in fish. The lakes are located in the upper and lower parts of the watercourse, with the lower site located closer to, and downstream from, the main pollution source. The lakes have complex fish communities dominated by coregonids (polymorphic whitefish and invasive vendace) and several piscivorous species. Analyses of habitat use, stomach contents, and stable isotope signatures (δ15N, δ13C) revealed similar food web structures in the two lakes except for a few differences chiefly related to ecological effects of the invasive vendace. The piscivores had higher Hg concentrations than invertebrate-feeding fish. Concentrations increased with size and age for the piscivores and vendace, whereas habitat differences were of minor importance. Most fish species showed significant differences in Hg concentrations between the lakes, the highest values typically found in the downstream site where the biomagnification rate also was higher. Mercury levels in piscivorous fish included concentrations that exceed health authorization limits, with possible negative implications for fishing and human consumption. Our findings accentuate the importance of acquiring detailed knowledge of the drivers that can magnify Hg concentrations in fish and how these may vary within and among aquatic systems, to provide a scientific basis for adequate management strategies.publishedVersio
Seaweed forests are carbon sinks that may help mitigate CO2 emissions: a comment on Gallagher et al. (2022)
Get PDFRecently, Gallagher et al. (2022) suggested that seaweed ecosystems are net heterotrophic carbon sources due to CO2 released from the consumption of external subsidies. Here we outline several flaws in their argument, which we believe confuse research on the blue carbon potential of seaweed ecosystems, and unjustifiably generate doubt around initiatives to protect and restore seaweed forests. Gallagher et al.’s evidence relies on 18 studies with highly variable measures of net ecosystem production, which do not statistically support their conclusion that most seaweed ecosystems are heterotrophic. This dataset is also inappropriate as it is incomplete and misrepresents seaweed ecosystems globally, particularly seaweed forests, which contribute disproportionately to global seaweed productivity. We maintain that the climate change mitigation value of an ecosystem depends on the net difference in CO2 uptake between the original ecosystem and its replacement ecosystem. We provide evidence that most seaweed ecosystems, which drawdown the largest carbon flux of any vegetated coastal habitat, are indeed net autotrophic ecosystems. We recognize that substantial uncertainties remain concerning the magnitude of CO2 drawdown by seaweed ecosystems and recommend that carbon fluxes around seaweed ecosystems should be considered more broadly and taken into account in estimates of their CO2 mitigation potential.publishedVersio
Forbedring av oksygenforhold ved kunstig omrøring i Oslofjorden
Get PDFProsjektleder: André StaalstrømIndre Oslofjorden har ca. 11,4 km² med havbunn hvor vannmassen over er periodevis eller permanent anoksisk. I denne rapporten blir effekt av nedpumping av overflatevann på oksygenforholdene modellert. Det blir dokumentert at Paddehavet har anoksiske forhold, og at nedpumping av 250 liter/s med overflatevann i en periode på 9 dager vil gi kunne gi 100 % oksygenmetning i hele vannsøylen, og det er sannsynlig at opp mot 120000 m² av sjøbunnen vil gå fra å være anoksisk til å få tilbake bioturberende organismer. Siden oppholdstiden i dypvannet er gitt av topografiske forhold, vil det være nødvendig å gjenta nedpumping av overflatevann med jevne mellomrom, for å oppnå en varig forbedring av oksygenforholdene.HafslundpublishedVersio
Tiltaksorientert overvåking av Husebybukta på Lista i 2022. Overvåking for Alcoa Lista.
Get PDFProsjektleder: Sigurd ØxnevadNIVA har utført tiltaksorientert overvåking av Husebybukta på Lista i 2022 på oppdrag for Alcoa Lista. Overvåkingsprogrammet er utarbeidet i henhold til vannforskriften og godkjent av Miljødirektoratet. Programmet er utformet på bakgrunn av bedriftens utslippskomponenter til sjøen. I overvåkingen er det gjort bestemmelser av PAH-forbindelser, arsen, bly, kadmium, kobber, krom, kvikksølv, nikkel, sink og fluorid i prøver av albusnegl fra fem stasjoner. Det ble også gjort overvåking av bly og kadmium i vannprøver fra Haugestranda. Overvåkingen i 2022 viser at albusnegl fra Haugestranda og Tjuvholmen hadde konsentrasjoner av benzo(a)pyren og fluoranten som ga overskridelse av grenseverdi for disse prioriterte stoffene. Kjemisk tilstand for de to stasjonene klassifiseres derfor som «ikke god». Det var ingen konsentrasjoner av prioriterte stoffer på de tre andre stasjonene som hadde overskridelse av grenseverdier, og kjemisk tilstand for stasjonene Einarsneset, Havik og Østhassel settes til «god». Det var høyere konsentrasjoner av PAH-forbindelser i albusnegl i 2022 enn i 2021. Det var ikke påviselige konsentrasjoner av kadmium i vannprøvene som ble tatt ved Haugestranda. For bly var gjennomsnittet av målingene lavere enn grenseverdi for årlig gjennomsnitt (AA-EQS). Konsentrasjoner av bly og kadmium lavere enn grenseverdiene gjør at kjemisk tilstand for vannprøvestasjonen klassifiseres som «god».Alcoa Norway avd. ListapublishedVersio
Tiltaksorientert overvåking av larvikittbruddene i Larvik kommune i 2022
Get PDFProsjektleder: Jonas PerssonDenne rapporten omhandler bunndyrundersøkelser i 2022 i utvalgte bekker som påvirkes av avrenning fra steinbruddene i områdene Tvedalen og Tjølling i Larvik kommune. Data fra senere års undersøkelser tilsier at PSI-indeksen responderer tilfredsstillende på partikkelavrenning, og gir verdifull informasjon om effekten av sedimentering på bunndyrene. Resultatene ved bruk av PSI-indeksen tyder på at bruddet Klåstad ikke lenger i betydelig grad påvirker bunndyrsamfunnene ved stasjonene undersøkt i 2022 (KLÅ3 og KLÅ4). Bedringen her er betydelig etter etableringen av sedimentasjonsdammer, og i 2022 viste begge stasjonene den laveste påvirkning av finsedimenter som er målt i undersøkelsene til nå. Tilstanden tilsvarer referansestasjonen i området (KRU3 ref). Ved stasjonen som overvåker bruddet Håkestad (HÅK1), var påvirkningen av partikulært finstoff betydelig lavere i 2022 enn i 2020-2021. Resultatene tilsier at belastningen i 2022 er på samme nivå (moderat sedimentert) som målingene gjort i 2018-2019. Bruddene Tvedalen mot Askedalsbekken og Saga Pearl viser i 2022 derimot økt belastning sammenlignet med tidligere år. Påvirkningen fra Tvedalen mot Askedalsbekken har blitt mindre de siste årene etter at etablering av en sedimentasjonsdam som har redusert spredningen av partikulært stoff. Bedringen har lenge vært stabil ved stasjonen ASK_opp, men i 2022 var tilstanden kraftig sedimentert og klart forverret sammenlignet med de siste årene. Det er fortsatt stor variasjon i tilstand ved ASK som ligger lengre nedstrøms i et mer roligflytende parti av bekken.WSP Norge ASpublishedVersio
Water Column Monitoring Research and development programme: Determining the residency of wild fish around offshore installations
Get PDFProsjektleder: Steven BrooksIn order to link effects with exposure, recent WCM programmes have discovered the need to determine the residency of fish, caught from within the safety zone of offshore installations. The method of using baited tags to encourage the voluntary ingestion of acoustic tags was thought promising and work was commissioned to develop the baited tag concept for field application. Acoustic telemetry products such as receivers and tag transmitters were obtained from the Norwegian electronics manufacturer Thelma Biotel AS. Developmental work, consisting of a series of cod feeding experiments in large aquaria at the NIVA marine research station in Solbergstrand, discovered some important findings including food preferences, residency time of the tag in the stomach of the fish and excretion pathways. A field trial was conducted in the Trondheimsfjord and although only one tag was eaten the quality of the data was promising for offshore application. The good quality images from the underwater camera with light fixed to the fishing line was also considered suitable for species determination and able to visually document the interactions of the baited tags with the fish. The offshore trial of the baited tag system at Ekofisk proved to be unsuccessful due to the unsuitability of the two fish species present at Ekofisk. It was thought the baited tag system would be more suitable in deeper waters with more voracious fish such as ling, tusk and larger haddock or cod. The baited tag system will be carefully considered for future water column monitoring campaigns.Offshore Norway, represented by EquinorpublishedVersio
"Hanging gardens" - comparing fauna communities in kelp farms and wild kelp forests
Get PDFA growing need for food is causing increased interest for seaweed farming globally. This requires knowledge of the industry’s effects on the marine environment. We therefore aimed to explore the communities hosted by a kelp farm compared to that of wild kelp forests. The study was performed in mid-western Norway. Kelp associated fauna were collected from farmed kelp (Saccharina latissima and Alaria esculenta), in wild kelp forests (S. latissima, A. esculenta and Laminaria hyperborea), and from fauna traps in the water column. The study showed that the kelp farm had lower taxa abundance and richness and a lower biodiversity than the wild kelp forests. Nonetheless, the farmed kelp hosted many associated species, with communities different from what was found on ropes without kelp (i.e., in the water column). The fauna communities among the farmed kelp were more similar to what was found in the wild L. hyperborea kelp forest than to its wild counterparts. The difference between the fauna communities of ‘old’ and ‘young’ farmed kelp (grown for 3 and 7 months, respectively) was not significant, but the fauna was dominated by the isopod species Idotea pelagica in the young forest and by amphipods, mainly belonging to the genus Caprella, in the older. The study contributes to our knowledge of kelp farms’ ecological role in the marine environment, which is of importance for today’s management as well as for ensuring a sustainable future development of the kelp farming industry.publishedVersio
Stressors affecting the ecological status of temporary rivers in the Mediterranean region
Get PDFTemporary rivers are widespread in the Mediterranean region and impose a challenge for the implementation of the Water Framework Directive (WFD) and other environmental regulations. Surprisingly, an overarching analysis of their ecological status and the stressors affecting them is yet missing. We compiled data on the ecological status of 1504 temporary rivers in seven European Mediterranean region countries and related their ecological status (1) to publicly available data on pressures from the European WISE-WFD dataset, and (2) to seven more specific stressors modelled on a sub-catchment scale. More than 50 % of the temporary water bodies in the Mediterranean countries reached good or even high ecological status. In general, status classes derived from phytobenthos and macrophyte assessment were higher than those derived from the assessment of benthic invertebrates or fish. Of the more generally defined pressures reported to the WISE-WFD database, the most relevant for temporary rivers were ‘diffuse agricultural’ and ‘point urban waste water’. Of the modelled more specific stressors, agricultural land use best explained overall ecological status, followed by total nitrogen load, and urban land use, while toxic substances, total phosphorus load and hydrological stressors were less relevant. However, stressors differed in relevance, with total nitrogen being most important for macrophytes, and agricultural land use for phytobenthos, benthic invertebrates and fish. For macrophytes, ecological quality increased with stressor intensity. The results underline the overarching effect of land use intensity for the ecological status of temporary water bodies. However, assessment results do not sufficiently reflect hydrological stress, most likely as the biological indicators used to evaluate these systems were designed for perennial water bodies and thus mainly target land use and nutrient impacts. We conclude that biomonitoring systems need to be updated or newly developed to better account for the specific situation of temporary water bodies.acceptedVersio
Head in the clouds, feet on the ground: how transdisciplinary learning can foster transformative change—insights from a summer school
Get PDFThere is a pressing need for transformative change, with a vision of long-term human well-being within planetary boundaries. The lack of progress—despite increasing awareness and action—illustrates how challenging it is to foster change in our complex global society. Education and learning are needed to enable change. Transdisciplinary learning, which meaningfully integrates diverse knowledge and perspectives, contributes to developing an integrative understanding—a necessity for tackling complex challenges. We explore how transdisciplinary learning for early-career researchers can foster transformative change and lead to increased biodiversity conservation. This paper focuses on a case study of the authors’ shared experiences during the 2021 Alternet Summer School, which focused on transformative change for biodiversity conservation and human well-being. In this introspective research, we gained insights through an online survey for participants and organizers of the summer school (n = 27). Using qualitative content analysis, we identify seven crucial elements of transdisciplinary learning which can lead to transformative change on (a) a personal level, as the learning process shifts values and helps researchers identify their roles; (b) a research level, by rethinking science and providing tools for transdisciplinary approaches, and (c) a societal level, by moving from the individual to the collective and constructing a shared vision for a sustainable future. Participants highlighted how changes on all these levels could benefit biodiversity conservation. These insights point to the benefit of transdisciplinary learning opportunities that empower young researchers to take up their part in fostering transformative change.publishedVersio
Annual changes in aquatic plant photosynthesis in the regulated river Otra and the effect of plant removal
Get PDFProsjektleder: Benoît O.L. DemarsMass development of submerged aquatic plants is often seen as nuisance for human activities. The present study used novel methods to estimate the changes in ecosystem photosynthesis (mostly Juncus bulbosus), through an annual cycle, under varying dissolved gas supersaturation events in the Rysstad basin, Otra River. The methods and results from this study may help us to understand the dynamics between supersaturation, J. bulbosus and fish health, and guide management decisions on aquatic plant removal.Krypsivprosjektet på Sørlandet (KPS). Sekretariat: Fylkesmannen i Agder, MiljøvernavdelingenpublishedVersio