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MEPS 725:29-44 (2023)  -  DOI: https://doi.org/10.3354/meps14449

Oceanographic structuring of the mucous-mesh grazer community in the Humboldt Current off Peru

Dominik Auch1,*, Vanessa Steinen1, Luisa Steckhan1, Rolf Koppelmann1, Sadegh Yari2, Volker Mohrholz2, Anna Schukat3, Mar Fernández-Méndez4, Leila Richards Kittu5, Myron A. Peck6

1Institute of Marine Ecosystem and Fisheries Science (IMF), University of Hamburg, 22767 Hamburg, Germany
2Leibniz Institute for Baltic Sea Research Warnemünde, 18119 Rostock, Germany
3Bremen Marine Ecology, University of Bremen, 28359 Bremen, Germany
4Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany
5GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany
6Department of Coastal Systems (COS), Royal Netherlands Institute for Sea Research (NIOZ), 1797 SZ 't Horntje, Texel, The Netherlands
*Corresponding author:

ABSTRACT: The Humboldt Upwelling System (HUS) supports high levels of primary production and has the largest single-stock fishery worldwide. The high fish production is suggested to be related to high trophic transfer efficiency in the HUS. Mucous-mesh grazers (pelagic tunicates and gastropods) are mostly of low nutritious value and might reduce trophic transfer efficiency when they are locally abundant. Unfortunately, little is known about the spatial dynamics of mucous-mesh grazers from Peruvian waters, limiting our understanding of their potential ecological role(s). We provide a spatial assessment of mucous-mesh grazer abundance from the Peruvian shelf in austral summer 2018/2019 along 6 cross-shelf transects spanning from 8.5 to 16°S latitude. The community was dominated by appendicularians and doliolids. Salps occurred in high abundance but infrequently, and pelagic gastropods were mostly restricted to the north. At low latitudes, the abundance of mucous-mesh grazers was higher than some key species of crustacean mesozooplankton. Transects in this region had stronger Ekman transport, higher temperature, lower surface turbidity and a broader oxygenated upper water layer compared to higher-latitude transects. Small-scale lateral intrusions of upwelled water were potentially associated with high abundances of doliolids at specific stations. The high abundance and estimated ingestion rates of mucous-mesh grazers in the northern HUS suggest that a large flux of carbon from lower trophic levels is shunted to tunicates in recently upwelled water masses. The data provide important information on the ecology of mucous-mesh grazers and stress the relevance to increase research effort on investigating their functioning in upwelling systems.


KEY WORDS: Gelatinous zooplankton · Abundance · Humboldt Upwelling System


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Cite this article as: Auch D, Steinen V, Steckhan L, Koppelmann R and others (2023) Oceanographic structuring of the mucous-mesh grazer community in the Humboldt Current off Peru. Mar Ecol Prog Ser 725:29-44. https://doi.org/10.3354/meps14449

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