Effect of salmon-derived nutrients and matters on riparian ecosystems in the Shiretoko World Natural Heritage area

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1 Effect of salmon-derived nutrients and matters on riparian ecosystems in the Shiretoko World Natural Heritage area Koshino Y, Minagawa M, Kudo H & Kaeriyama M. Graduate School of Fisheries Sciences, Hokkaido University y_koshino516@fish.hokudai.ac.jp

2 Material cycles in the terrestrial ecosystems Physical Biological Rainfall P N N Vaporization Feces N P Nutrients Organic matters Flowing Spawning migration

3 Pacific salmon contributed on the productivity and biodiversity as Ecosystem-Transboundary Materials (ETMs) Pacific salmon supply a large amount of nutrients to natal spawning ground (e.g. Juday et all. 1932; Donaldson 1967; Johnson & Johnson et al.2003) Marine-derived nutrients (MDN) facilitate growth rate and body condition of aquatic organisms (Bilby et al. 1998; Wipfli et al.2003) Riparian vegetation increase growth rate and biodiversity in salmon spawning area Various trophic levels (Helfield & Naiman 2001; Bilby et al. 2003)

4 Disruption of salmon spawning environment Anthropogenic impacts River channel modification Artificial river constructions Hatchery programs Disturbance Freshwater ecosystems Reproduction of wild salmon Anthropogenic impacts negatively affect the wild salmon reproduction (Kaeriyama & Edapalina 2004)

5 Objects Pacific salmon play a significant role in the terrestrial ecosystems as biodiversity and productivity in order to transport marine-derived nutrients (MDN) at the spawning period As an example of ETMs, we evaluate the MDN contributions for freshwater and riparian ecosystems in the Shiretoko World Natural Heritage area, Japan, using carbon and nitrogen stable isotope analysis

6 Field sampling Shiretoko Peninsula (World Natural Heritage Area) Pre-spawning: July Spawning (Rusha River) Three artificial dams for controlling erosion in lower reach Non-spawning (Akai River) Investigation in non-spawning area between the impassible dams Akai River Spawning : September to October Hokkaido Rusha River Shiretoko Peninsula Rusha R. Akai R. Tributary of Iwaubetu R.

7 Stable isotope analysis Biofilm Salmonids Dolly Varden Masu salmon Pink salmon Samples Aquatic invertebrates Mayfly Caddisfly Stonefly Amphipod Chironomid Plants Willow Butterbur Bamboo Male fern Alder Mammals Brown bear Yezo sitka deer MAT252 (Finningan MAT) δ 13 C orδ 15 N ( ) =( R sample /R standard -1) 1000 Growth Section Analysis (GSA) MDN enrichment δx se δx c TL δx s δx e 5 mm R = 13 C/ 12 C or 15 N/ 14 N Feeding history of brown bear Root Bear hair Tip (Mizukami et al. 2005) =(δx se -δx c )/(δx s +(TL δx e )-δx c ) = the isotope ratios of the organism in areas enriched with salmon = the isotope ratio of the organism in areas without salmon enrichment = the trophic level = the isotopic ratio of salmon = the isotopic enrichment factor (Johnston 1997)

8 Stomach contents analysis Dolly Varden (Salvelinus malma) IRI = (N + W) F N : % by number of prey W : % by weight of prey F : frequency (Pinkas et al. 1971) Four categories: 1) Terrestrial invertebrates 2) Aquatic invertebrates 3) Salmon eggs 4) Sea lice (Lepeophtheirus salmonis) Salmon egg Discrimination of pink salmon carcasses Bear-killed carcass Senescent carcass Sea lice

9 The C-N map of freshwater organisms Pink salmon Salmonids Spawning(Rusha R.) Pre-spawning(Rusha R.) Non-spawning(Akai R.) δ 15 N ( ) 3 0 Biofilm -3 Aquatic invertebrates δ 13 C ( ) MDN changed trophic position of organisms in the food-web of freshwater ecosystems

10 Feeding habits of Dolly Varden in the Shiretoko 2 Non-spawning (Akai R.) IRI 0 2 Pre-spawning period Spawning period Spawning (Rusha R.) Jul Aug Sep Oct Aquatic invertebrates Terrestrial invertebrates Pink salmon eggs Sea lice Dolly Varden switched preys from invertebrates to salmon eggs in salmon spawning period

11 Frequency (%) Distance of carcass transported by brown bear from the river Almost bears carried carcasses to the Near 0 Near (<10m) Middle (10m< >30m) Far (>30m) Brown bears serve as a vector of salmon carcass in riparian area

12 individuals Precipitation (mm/day) Temporal change in number of pink salmon carcasses on the riparian area in Bear-killed (N=412) Senescent (N=1,062) Senescent>Bear-killed Water level Precipitation Transport 20-Sep 25-Sep 30-Sep 5-Oct 10-Oct The flooding is one of the main process for carcass transport as well as brown bear Water level (m)

13 6 4 2 The C-N map of riparian vegetation Spruce Willow Alder Butterbur Bamboo (collected within 10m from the river) Spawning (Rusha R.) δ 15 N ( ) Non-spawning (Akai R.) δ 13 C ( ) Riparian vegetation around the Rusha River had higher stable isotope than those of the Akai River

14 δ 15 N of willow foliage ( ) Relationship between δ 15 N of willow and the distance from the river ** Spawning (Rusha R.) δ 15 N = L+1.80 (r = -0.54, P = 0.005) * Non-spawning (Akai R.) δ 15 N = L 1.03 (r = -0.03, P = 0.87) ** P < 0.01 * P < Distance from the river (L, m) MDN was incorporated within 50 m from the river

15 Conclusion MDN contribution to Rusha River terrestrial ecosystems Averaged MDN enrichment 24 % Rusha R. North America Biofilm 30 % 73 % Aquatic invertebrates 21 % 40 % Salmonids 23 % 40 % Riparian tree 22 % 24 % Low High (Chaloner et al. 2002) (Chaloner et al. 2002) (Bilby et al. 1996) (Helfield and Naiman 2001) Antropogenic impact Artificial dams disturb the spawning behavior (Boggs et al. 2004, Caudill et al. 2007) The spawning-redd density of pink salmon; Rusha River : /m 2 (Yokoyama et al. 2010) North America : /m 2 (Heard 1991) MDN incorporation in the Rusha River region was negatively affected by anthropogenic impacts despite the World Natural Heritage area

16 MDN pathways in terrestrial ecosystems Herb Arbor 15 % Fly maggots? Dolly Varden 29 % Brown bear Salmon carcass Invertebrates 24 % 45 % Flooding Biofilm 30 % Pink salmon 21 % Seabirds? MDN flow Freshwater ecosystem: Direct feeding, Food chain Riparian ecosystem : Flooding, Vector