Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size
Abstract When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine‐derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen‐15 (15N), are...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2021-09-01
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| Series: | Ecology and Evolution |
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| Online Access: | https://doi.org/10.1002/ece3.8017 |
| _version_ | 1818718010980958208 |
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| author | Nicola F. Rammell Allison M. Dennert Christopher M. Ernst John D. Reynolds |
| author_facet | Nicola F. Rammell Allison M. Dennert Christopher M. Ernst John D. Reynolds |
| author_sort | Nicola F. Rammell |
| collection | DOAJ |
| description | Abstract When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine‐derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen‐15 (15N), are often used to trace the destination of marine‐derived nutrients in riparian habitats. However, few studies have tested for correlations between stable isotopes and physiological responses of riparian organisms. We examined whether increases in δ15N in terrestrial insect bodies adjacent to salmon spawning habitat translate to changes in percent nitrogen content and body size. This involved comparisons between distance from a salmon‐bearing river, marine‐derived nutrients in soils and insects, soil moisture content, and body size and nitrogen content in two common beetle families (Coleoptera: Curculionidae, Carabidae). As predicted, δ15N in riparian soils attenuated with distance from the river but was unaffected by soil moisture. This gradient was mirrored by δ15N in the herbivorous curculionid beetles, whereas carabid beetles, which feed at a higher trophic level and are more mobile, did not show discernable patterns in their δ15N content. Additionally, neither distance from the river nor body δ15N content was related to beetle body size. We also found that nitrogen‐15 was not correlated with total percent nitrogen in insect bodies, meaning that the presence of spawning salmon did not increase the percent nitrogen content of these insects. We conclude that while salmon‐derived nutrients had entered terrestrial food webs, the presence of δ15N alone did not indicate meaningful physiological changes in these insects in terms of percent nitrogen nor body size. While stable isotopes may be useful tracers of marine‐derived nutrients, they cannot necessarily be used as a proxy for physiologically important response variables. |
| first_indexed | 2024-12-17T19:44:15Z |
| format | Article |
| id | doaj.art-eb5568c899f943f18b93dc5f94d81ae7 |
| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-12-17T19:44:15Z |
| publishDate | 2021-09-01 |
| publisher | Wiley |
| record_format | Article |
| series | Ecology and Evolution |
| spelling | doaj.art-eb5568c899f943f18b93dc5f94d81ae72022-12-21T21:34:55ZengWileyEcology and Evolution2045-77582021-09-011118127281273810.1002/ece3.8017Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body sizeNicola F. Rammell0Allison M. Dennert1Christopher M. Ernst2John D. Reynolds3Earth to Ocean Research Group Department of Biological Sciences Simon Fraser University Burnaby BC CanadaEarth to Ocean Research Group Department of Biological Sciences Simon Fraser University Burnaby BC CanadaEarth to Ocean Research Group Department of Biological Sciences Simon Fraser University Burnaby BC CanadaEarth to Ocean Research Group Department of Biological Sciences Simon Fraser University Burnaby BC CanadaAbstract When Pacific salmon (Oncorhynchus spp.) spawn and die, they deliver marine‐derived nutrient subsidies to freshwater and riparian ecosystems. These subsidies can alter the behavior, productivity, and abundance of recipient species and their habitats. Isotopes, such as nitrogen‐15 (15N), are often used to trace the destination of marine‐derived nutrients in riparian habitats. However, few studies have tested for correlations between stable isotopes and physiological responses of riparian organisms. We examined whether increases in δ15N in terrestrial insect bodies adjacent to salmon spawning habitat translate to changes in percent nitrogen content and body size. This involved comparisons between distance from a salmon‐bearing river, marine‐derived nutrients in soils and insects, soil moisture content, and body size and nitrogen content in two common beetle families (Coleoptera: Curculionidae, Carabidae). As predicted, δ15N in riparian soils attenuated with distance from the river but was unaffected by soil moisture. This gradient was mirrored by δ15N in the herbivorous curculionid beetles, whereas carabid beetles, which feed at a higher trophic level and are more mobile, did not show discernable patterns in their δ15N content. Additionally, neither distance from the river nor body δ15N content was related to beetle body size. We also found that nitrogen‐15 was not correlated with total percent nitrogen in insect bodies, meaning that the presence of spawning salmon did not increase the percent nitrogen content of these insects. We conclude that while salmon‐derived nutrients had entered terrestrial food webs, the presence of δ15N alone did not indicate meaningful physiological changes in these insects in terms of percent nitrogen nor body size. While stable isotopes may be useful tracers of marine‐derived nutrients, they cannot necessarily be used as a proxy for physiologically important response variables.https://doi.org/10.1002/ece3.8017body conditionbody sizeCarabidaeCurculionidaeinsectsisotope |
| spellingShingle | Nicola F. Rammell Allison M. Dennert Christopher M. Ernst John D. Reynolds Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size Ecology and Evolution body condition body size Carabidae Curculionidae insects isotope |
| title | Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size |
| title_full | Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size |
| title_fullStr | Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size |
| title_full_unstemmed | Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size |
| title_short | Effects of spawning Pacific salmon on terrestrial invertebrates: Insects near spawning habitat are isotopically enriched with nitrogen‐15 but display no differences in body size |
| title_sort | effects of spawning pacific salmon on terrestrial invertebrates insects near spawning habitat are isotopically enriched with nitrogen 15 but display no differences in body size |
| topic | body condition body size Carabidae Curculionidae insects isotope |
| url | https://doi.org/10.1002/ece3.8017 |
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