Environmental variability shapes trophic and resource partitioning between epipelagic and mesopelagic biomes in oceanic provinces: Implications in a globally changing ocean
{"title":"Environmental variability shapes trophic and resource partitioning between epipelagic and mesopelagic biomes in oceanic provinces: Implications in a globally changing ocean","authors":"","doi":"10.1016/j.pocean.2024.103339","DOIUrl":null,"url":null,"abstract":"<div><p>Trophic links between the epipelagic (< 200 m) and mesopelagic layers of the Indian Ocean were investigated by carbon and nitrogen stable isotope ratios of 2405 samples collected from 2002 to 2016, and that encompass the base of trophic webs, and primary, secondary and tertiary consumers. The samples include particulate organic matter, gastropods, gelatinous organisms such as salps and pyrosomes, crustaceans, mesopelagic fishes, micronektonic and nektonic squids, tuna and swordfish. Stable δ<sup>13</sup>C and δ<sup>15</sup>N values were used to investigate trophic and resource partitioning between epipelagic <em>vs</em> mesopelagic (migrators and non-migrators), feeding patterns (zooplanktivorous <em>vs</em> micronektivorous), and at seamounts and off-seamount locations. We also investigated how contrasting environmental conditions within two biogeochemical provinces, the ISSG (Indian South Subtropical Gyre) and EAFR (East African Coastal Province), influenced stable isotope patterns. Our data suggest that broad-scale biogeochemical differences and local environmental conditions significantly shape trophic and resource partitioning. In oligotrophic systems, epipelagic migrating and non epipelagic-migrating organisms rely on food webs where suspended particles are <sup>15</sup>N-enriched and organic matter recycled/re-processed. We show that seamounts form strong isotopic topographic barriers (which we define as “isobiome”) that impact the trophic linkages/connections between epipelagic migrants and non-epipelagic migrants, and those with zooplanktivorous feeding patterns. This study reveals that the trophic and resource partitioning in the ocean is more complex than initially thought, when environmental variability, bathymetric gradients, and a wider range of samples are taken into account compared to earlier studies. We also showed that a warmer ocean led to a reduction in productivity, lower values of δ<sup>13</sup>C and δ<sup>15</sup>N, and potential shifts in food web trophic structure that remain to be investigated further. Finally, we discuss how important it is to unravel this complexity on a global scale given the vulnerability of epipelagic and mesopelagic communities due to anthropogenic pressures in the Anthropocene.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":null,"pages":null},"PeriodicalIF":3.8000,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Progress in Oceanography","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0079661124001459","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"OCEANOGRAPHY","Score":null,"Total":0}
引用次数: 0
Abstract
Trophic links between the epipelagic (< 200 m) and mesopelagic layers of the Indian Ocean were investigated by carbon and nitrogen stable isotope ratios of 2405 samples collected from 2002 to 2016, and that encompass the base of trophic webs, and primary, secondary and tertiary consumers. The samples include particulate organic matter, gastropods, gelatinous organisms such as salps and pyrosomes, crustaceans, mesopelagic fishes, micronektonic and nektonic squids, tuna and swordfish. Stable δ13C and δ15N values were used to investigate trophic and resource partitioning between epipelagic vs mesopelagic (migrators and non-migrators), feeding patterns (zooplanktivorous vs micronektivorous), and at seamounts and off-seamount locations. We also investigated how contrasting environmental conditions within two biogeochemical provinces, the ISSG (Indian South Subtropical Gyre) and EAFR (East African Coastal Province), influenced stable isotope patterns. Our data suggest that broad-scale biogeochemical differences and local environmental conditions significantly shape trophic and resource partitioning. In oligotrophic systems, epipelagic migrating and non epipelagic-migrating organisms rely on food webs where suspended particles are 15N-enriched and organic matter recycled/re-processed. We show that seamounts form strong isotopic topographic barriers (which we define as “isobiome”) that impact the trophic linkages/connections between epipelagic migrants and non-epipelagic migrants, and those with zooplanktivorous feeding patterns. This study reveals that the trophic and resource partitioning in the ocean is more complex than initially thought, when environmental variability, bathymetric gradients, and a wider range of samples are taken into account compared to earlier studies. We also showed that a warmer ocean led to a reduction in productivity, lower values of δ13C and δ15N, and potential shifts in food web trophic structure that remain to be investigated further. Finally, we discuss how important it is to unravel this complexity on a global scale given the vulnerability of epipelagic and mesopelagic communities due to anthropogenic pressures in the Anthropocene.
期刊介绍:
Progress in Oceanography publishes the longer, more comprehensive papers that most oceanographers feel are necessary, on occasion, to do justice to their work. Contributions are generally either a review of an aspect of oceanography or a treatise on an expanding oceanographic subject. The articles cover the entire spectrum of disciplines within the science of oceanography. Occasionally volumes are devoted to collections of papers and conference proceedings of exceptional interest. Essential reading for all oceanographers.