Nutrient availability induces community shifts in seagrass meadows grazed by turtles
In the Caribbean, green turtles graze seagrass meadows dominated by Thalassia testudinum through rotational grazing, resulting in the creation of grazed and recovering (abandoned) patches surrounded by ungrazed seagrasses. We evaluated the seagrass community and its environment along a turtle grazin...
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| Format: | Article |
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PeerJ Inc.
2019-09-01
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| Online Access: | https://peerj.com/articles/7570.pdf |
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| author | Isis Gabriela Martínez López Marloes van Den Akker Liene Walk Marieke M. van Katwijk Tjisse van Der Heide Brigitta I. van Tussenbroek |
| author_facet | Isis Gabriela Martínez López Marloes van Den Akker Liene Walk Marieke M. van Katwijk Tjisse van Der Heide Brigitta I. van Tussenbroek |
| author_sort | Isis Gabriela Martínez López |
| collection | DOAJ |
| description | In the Caribbean, green turtles graze seagrass meadows dominated by Thalassia testudinum through rotational grazing, resulting in the creation of grazed and recovering (abandoned) patches surrounded by ungrazed seagrasses. We evaluated the seagrass community and its environment along a turtle grazing gradient; with the duration of (simulated) grazing as a proxy for the level of grazing pressure. The grazing levels consisted of Short-term (4 months clipping), Medium-term (8 months clipping), Long-term grazing (8 months of clipping in previously grazed areas), 8-months recovery of previously grazed patches, and ungrazed or unclipped patches as controls. We measured biomass and density of the seagrasses and rhizophytic algae, and changes in sediment parameters. Medium- and Long-term grazing promoted a shift in community species composition. At increasing grazing pressure, the total biomass of T. testudinum declined, whereas that of early-successional increased. Ammonium concentrations were highest in the patches of Medium-term (9.2 + 0.8 μM) and Long-term grazing levels (11.0 + 2.2 μM) and were lowest in the control areas (4.6 + 1.5 μM). T. testudinum is a late-successional species that maintains sediment nutrient concentrations at levels below the requirements of early-successional species when dominant. When the abundance of this species declines due to grazing, these resources become available, likely driving a shift in community composition toward a higher abundance of early-successional species. |
| first_indexed | 2024-03-09T07:28:02Z |
| format | Article |
| id | doaj.art-397b6bef5b2845c89c0ba9c258df6bf7 |
| institution | Directory Open Access Journal |
| issn | 2167-8359 |
| language | English |
| last_indexed | 2024-03-09T07:28:02Z |
| publishDate | 2019-09-01 |
| publisher | PeerJ Inc. |
| record_format | Article |
| series | PeerJ |
| spelling | doaj.art-397b6bef5b2845c89c0ba9c258df6bf72023-12-03T06:47:17ZengPeerJ Inc.PeerJ2167-83592019-09-017e757010.7717/peerj.7570Nutrient availability induces community shifts in seagrass meadows grazed by turtlesIsis Gabriela Martínez López0Marloes van Den Akker1Liene Walk2Marieke M. van Katwijk3Tjisse van Der Heide4Brigitta I. van Tussenbroek5Instituto de Ciencias del Mar y Limnología/Unidad Académica de Sistemas Arrecifales-Puerto Morelos, Universidad Nacional Autónoma de México, Puerto Morelos, Quintana Roo, MexicoInstitute for Water and Wetland Research, Radboud University, Nijmegen, The NetherlandsInstitute for Water and Wetland Research, Radboud University, Nijmegen, The NetherlandsInstitute for Water and Wetland Research, Radboud University, Nijmegen, The NetherlandsInstitute for Water and Wetland Research, Radboud University, Nijmegen, The NetherlandsInstituto de Ciencias del Mar y Limnología/Unidad Académica de Sistemas Arrecifales-Puerto Morelos, Universidad Nacional Autónoma de México, Puerto Morelos, Quintana Roo, MexicoIn the Caribbean, green turtles graze seagrass meadows dominated by Thalassia testudinum through rotational grazing, resulting in the creation of grazed and recovering (abandoned) patches surrounded by ungrazed seagrasses. We evaluated the seagrass community and its environment along a turtle grazing gradient; with the duration of (simulated) grazing as a proxy for the level of grazing pressure. The grazing levels consisted of Short-term (4 months clipping), Medium-term (8 months clipping), Long-term grazing (8 months of clipping in previously grazed areas), 8-months recovery of previously grazed patches, and ungrazed or unclipped patches as controls. We measured biomass and density of the seagrasses and rhizophytic algae, and changes in sediment parameters. Medium- and Long-term grazing promoted a shift in community species composition. At increasing grazing pressure, the total biomass of T. testudinum declined, whereas that of early-successional increased. Ammonium concentrations were highest in the patches of Medium-term (9.2 + 0.8 μM) and Long-term grazing levels (11.0 + 2.2 μM) and were lowest in the control areas (4.6 + 1.5 μM). T. testudinum is a late-successional species that maintains sediment nutrient concentrations at levels below the requirements of early-successional species when dominant. When the abundance of this species declines due to grazing, these resources become available, likely driving a shift in community composition toward a higher abundance of early-successional species.https://peerj.com/articles/7570.pdfChelonia mydasNitrogenCompetitionRotational grazingAmmonium |
| spellingShingle | Isis Gabriela Martínez López Marloes van Den Akker Liene Walk Marieke M. van Katwijk Tjisse van Der Heide Brigitta I. van Tussenbroek Nutrient availability induces community shifts in seagrass meadows grazed by turtles PeerJ Chelonia mydas Nitrogen Competition Rotational grazing Ammonium |
| title | Nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| title_full | Nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| title_fullStr | Nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| title_full_unstemmed | Nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| title_short | Nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| title_sort | nutrient availability induces community shifts in seagrass meadows grazed by turtles |
| topic | Chelonia mydas Nitrogen Competition Rotational grazing Ammonium |
| url | https://peerj.com/articles/7570.pdf |
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