Organic carbon accumulation in Hardangerfjorden A micropaleontological and geochemical study of benthic environmental impact from fish farming Lars Birkeland Sjetne Master Thesis Environmental geology – environmental stratigraphy 60 credits Institute of Geosciences The Faculty of Mathematical and Natural Sciences UNIVERSITY OF OSLO 06/2017 II Organic carbon accumulation in Hardangerfjorden A micropaleontological and geochemical study of benthic environmental impact from fish farming Lars Birkeland Sjetne Master Thesis Environmental geology – environmental stratigraphy 60 credits Institute of Geosciences The Faculty of Mathematical and Natural Sciences UNIVERSITY OF OSLO 06/2017 III © Lars Birkeland Sjetne 2017 Organic carbon accumulation in Hardangerfjorden Lars Birkeland Sjetne http://www.duo.uio.no/ Trykk: Reprosentralen, Universitetet i Oslo IV Abstract The present study investigated the impact of organic loading from fish farm waste on the benthic environment surrounding a fish farm, and the organic carbon accumulation in fjord sediments in a Western Norwegian fjord. One sediment core collected 100 m from the fish farm was compared with a control core collected 500 m from the farm. Both cores were radiometrically dated to 1927. Interpretation of depositional environment was done based on grain size distribution analysis. Benthic foraminifera (protists) were utilized to assess the ecological quality status (EcoQS) of the benthic environment in each sample, based on foraminiferal species diversity, foraminiferal assemblage composition and benthic foraminiferal accumulation rates (BFAR). Total organic carbon- and total nitrogen content in the sediments, together with stable C- and N-isotope ratios and C- and O-isotope ratios in the tests of selected foraminiferal species, were used to interpret the source of organic matter in the sediments. Heavy metal concentrations were measured and the sediments classified according to official guidelines for sediment pollution. Stable isotope signals and carbon- and nitrogen content was stable throughout the period since 1927 until present-day in both cores, and showed no evidence for increased organic loading related to fish production. Both cores had C/N-ratios characteristic of marine organic matter in sediments deposited after 1927. Foraminiferal species assemblage compositions reflected naturally different benthic environments in the two cores, and showed no clear response to fish production. EcoQS was ‘good’ in both cores. BFAR in the control core increased since the onset of fish production. V Acknowledgements I would like to thank my supervisor Elisabeth Alve who facilitated this project and for always being available for insightful comments and guidance. An equal thanks to my co-supervisor Silvia Hess for invaluable lab assistance and for pushing me in the right direction, and Paul Renaud for helpful comments. Excellent service was provided by lab engineers Mufak Said Naoroz and Siri Simonsen at the Department of Geosciences, UiO. M/S Solvik skipper Leon Pedersen deserves praise for his ingenuity and for making the Hardangerfjord cruise very enjoyable, as does the rest of the crew members. Thanks to Kristian Råsberg at Alsaker Fjordbruk AS for providing fish farm data, Lars Asplin at IMR for hydrographic data and Anouk Tosca Klootwijk, Astrid Harendza and the other participants of the Jellyfarm project for their help. Thanks to fellow students, friends and family for keeping up the morale. VI Table of Contents 1 Introduction .......................................................................................................................11 2 Study area .........................................................................................................................15 2.1 Hardangerfjorden ......................................................................................................15 2.2 Hydrography .............................................................................................................15 2.3 Influence of fish farming in Hardangerfjorden .........................................................17 2.4 Onarheimsfjorden .....................................................................................................19 3 Methods ............................................................................................................................23 3.1 Sample collection and preparations ..........................................................................23 3.2 Sediment dating ........................................................................................................24 3.3 Organic carbon (TOC) content, total nitrogen (TN) content and d15N and d13C of the sediments .........................................................................................................................25 3.4 Heavy metal concentrations ......................................................................................25 3.5 Particle size distribution analysis ..............................................................................26 3.6 Micropaleontological analysis ..................................................................................26 3.7 Stable isotope analyses of foraminiferal tests ...........................................................27 4 Results ...............................................................................................................................28 4.1 Fish farm station, FF-core .........................................................................................28 4.2 Non-fish farm station, NF-core .................................................................................35 5 Discussion .........................................................................................................................44 5.1 Comparison of the two cores ....................................................................................44 5.1.1 Sediment chronology and accumulation rates ......................................................44 5.1.2 Heavy metal concentrations ..................................................................................45 5.1.3 Carbon accumulation rates, source of organic matter and stable isotopes ...........46 5.1.4 Stable isotope ratios of foraminiferal tests ............................................................48 5.1.5 Foraminiferal assemblages ....................................................................................50 5.2 Impact of fish farming on the benthic environment and the natural condition .........53 5.3 Comparison with other fjords ...................................................................................56 Conclusions ...............................................................................................................................60 References: ................................................................................................................................62 Appendices: ...............................................................................................................................70 Appendix A: Lab report from sediment dating .........................................................................70 Appendix B: Laboratory report for carbon and nitrogen analysis of sediment samples ..........80 VII Appendix C: Results from geochemical analyses .....................................................................83 Appendix D: Results from stable isotope analyses of foraminiferal tests. ...............................84 Appendix E: Foraminifera data, total counts and diversity indices (colour codes listed in Table 4-1) ............................................................................................................................................87 Appendix F: Foraminifera data, concentration of tests (individuals/g dry sediment). .............88 Appendix G: Foraminifera data, relative species abundance (%) .............................................89 Appendix H: Foraminifera reference list, based on The World Register of Marine Species (WoRMS, 2017) ........................................................................................................................90 List of figures and tables: Figure 2.1: Dashed line indicate the extent of Hardangerfjorden, from the sill at Huglo into the innermost Sørfjorden. Red circle marks the extent of Onarheimsfjorden and the red line marks the sill at Huglo (map modified from www.kartverket.no ). .........................................15 Figure 2.2: Monthly average precipitation for the period 2007-2016 measured at a weather station in Rosendal, East of Onarheimsfjorden. Average annual precipitation in this period was 2088mm (data from Meteorologisk Institutt, www.eklima.met.no). .................................16 Figure 2.3: Bathymetric map of Onarheimsfjorden (encircled) in Hardangerfjorden. FF = fish farm, 100 m from the fish farm. NF = non-fish farm, 500 m away from the fish farm. Red line in bottom left corner marks the outer sill by Huglo (Figure 2.1), red arrow marks position of Onarheimselva (modified from www.kartverket.no). ...............................................................20 Figure 2.4 A-C: CTD-data from MOM-C survey conducted in March 2014. ‘Fish farm’ is located directly below the fish farm, ‘Transition’ and ‘Distal at 300 m and 1000 m away from the fish farm, respectively. A: Oxygen concentrations. B: Water salinity. C: Water temperature (Ingebrigtsen et al., 2014). ....................................................................................21 Figure 2.5: Conceptual illustration of Hardangerfjorden (basin) and Onarheimsfjorden with the fish farm anchored at the sea floor. Arrows indicate the fish farm’s movement. Colors indicate the theoretical stratification of the water column. Note that proportions are not correct. ......................................................................................................................................22 Figure 4.1A-C: A: FF-core under inspection. B: Water- and sand content. Red line marks the dating horizon. C: Differential volume of the complete grain size range. ................................29 Figure 4.2A-B: A: Age models for FF- and NF-core. Note how error margins are increasing down core. B: Unsupported (i. e. radionuclides from atmospheric fallout) 210Pb-activity in both cores. .................................................................................................................................30 Figure 4.3A-B: A: TOC content and stable carbon isotope ratio, FF-core. B: Total nitrogen content and stable nitrogen isotope ratio, NF-core. Dashed red line indicates dating horizon. Red arrow marks the onset of fish farming. ..............................................................................31 Figure 4.4: Heavy metal concentrations and their corresponding environmental classification (Table 4-1). Dashed red line marks the dating horizon, red arrow marks the onset of fish production. ................................................................................................................................32 VIII Figure 4.5 A-B: A: Foraminiferal concentration and BFAR, FF-core. Diversity indices (ES(100) and H’(log2)), FF-core. Dashed red line marks dating horizon, red arrow marks start of fish production. .....................................................................................................................33 Figure 4.6 A-B: A: Stable carbon isotope composition in tests of Uvigerina peregrina, Hyalinea balthica and Cassidulina laevigata. B: Stable oxygen composition of the aforementioned species. Dashed red line mark the dating horizon, red arrow marks the start of fish production. .........................................................................................................................34 Figure 4.7 A-B: A: NF-core during inspection. B: Replicate core (AKS203) from control station split vertically. ...............................................................................................................35 Figure 4.8: Water- and sand content NF-core. Dashed red line marks the dating horizon, red arrow marks the start of fish production. ..................................................................................36 Figure 4.9: Sediment accumulation rates in FF- and NF-core. Dashed red line marks the start of fish production. .....................................................................................................................36 Figure 4.10: Differential volume of the complete particle size range of sediments in the NF- core. Particles > 2mm were not included in the analysis and are therefore not shown in the diagram. Red arrow marks the sample representing the dating horizon. ..................................37 Figure 4.11A-B: A: TOC content and stable carbon isotope ratio, NF-core. B: TN content and stable nitrogen isotope ratio, NF-core. Dashed red line marks the dating horizon, red arrow marks the start of fish production. ..................................................................................38 Figure 4.12: Heavy metal concentrations and their corresponding environmental classifications, NF-core. Dashed red line marks the dating horizon, red arrow marks the start of fish production. .....................................................................................................................39 Figure 4.13: A-B: A: Foraminiferal concentration and BFAR, NF-core. Diversity indices (ES(100) and H’(log2)), NF-core. Dashed red line marks dating horizon, red arrow marks start of fish production. .............................................................................................................40 Figure 4.14: Two-dimensional MDS-ordination plot based on faunal assemblage (relative abundance) similarity between analysed samples. ....................................................................41 Figure 4.15A-B: A: Stable carbon isotope composition in tests of Uvigerina peregrina, Hyalinea balthica and Cassidulina laevigata. B: Stable oxygen composition of the aforementioned species. Dashed red line mark the dating horizon, red line marks the start of fish production. .........................................................................................................................41 Figure 4.16 A-F: MDS- diagram showing relative occurrence of A: P. osloensis; B: B. skagerrakensis; C: T. earlandi; D: H. balthica; E: E. medius; F: N. iridea in both cores. Sphere size indicate concentration (individuals/g) of the species in each sample. Dashed line indicates 65 fauna similarity. Red spheres = FF-core, green spheres = NF-core. ....................42 Figure 4.17 A-E: MDS- diagram showing relative occurrence of A: P. osloensis; B: C. laevigata; C: C. reniform, D: B. marginata, E: S. fusiformis. Sphere size indicate concentration (individuals/g) of the species in each sample. Dashed line indicates 65 fauna similarity. Red spheres = FF-core, green spheres = NF-core. ..................................................43 Figure 5.1: TOC- and TN accumulation rates of both cores since 1927. ................................46 Figure 5.2: Diagram showing characteristic ranges of C/N- and d13C-values of organic matter from different sources. C3 and C4 relates to modes of carbon fixation through different IX photosynthetic pathways. 90% of all terrestrial plants utilize the C3 pathway (Lamb et al. 2006 and references therein). Figure modified from Lamb et al. (2006). ................................48 Figure 5.3: Temperature curve from measuring station at Ytre Utsira, measuring coastal water temperatures at 200m depth (data from IMR, Lars Asplin, pers comm Apr. 2017) .......50 Figure 5.4: Foraminiferal concentration and BFAR in sediments younger than 1927, both cores. Dashed red line marks the start of fish production. ........................................................51 Table 3-1: Station details. ........................................................................................................23 Table 4-1: Classification intervals for soft marine sediment. Diversity indices based on H’ and ES(100) (Veileder 02:2013), heavy metal concentrations (Veileder M-608:2016). ..........28 Table 5-1: Macrofauna diversity indices at various distances from the fish farm in Onarheimsfjorden. Data from MOM-C surveys in 2008 and 2014 (Ingebrigtsen et al., 2014; P. O. Johansen and Botnen, 2008). ...............................................................................................55 Table 5-2: Overview of various parameters in three Western Norwegian fjords (Onarheimsfjorden (this study), Lurefjorden (Torper, 2017), Lysefjorden (C. J. Duffield et al., 2017)): Average sedimentation rate, average TOC content, range of C/N ratio, carbon accumulation rates, average sand content, and diversity indices ES(100) and H'(log2). Colour refers to ecological quality status (EcoQS) according to table 4-1. ..........................................57 Table 5-3: Species of foraminifera with occurrence > 10% in at least one sample in Onarheimsfjorden, Lurefjorden (Torper, 2017), and Lysefjorden (C. J. Duffield et al., 2017). ...................................................................................................................................................59 X