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Macrozooplankton and micronekton community structure and diel vertical migration in the Heard Island Region, Central Kerguelen Plateau

Citation

Hunt, BPV and Swadling, KM, Macrozooplankton and micronekton community structure and diel vertical migration in the Heard Island Region, Central Kerguelen Plateau, Journal of Marine Systems, 221 Article 103575. ISSN 0924-7963 (2021) [Refereed Article]


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DOI: doi:10.1016/j.jmarsys.2021.103575

Abstract

The Kerguelen Plateau is the largest topographic barrier to the eastward flowing Antarctic Circumpolar Current (ACC) in the Indian Sector of the Southern Ocean. The plateau is separated into a northern and southern plateau by the Fawn Trough. The northern plateau has a shallow bathymetry (<700 m) with two prominent island systems, the Kerguelen Islands on the northern end and Heard and McDonald Islands on the southern end. The interaction of the northern and southern branches of the Polar Front with the northern plateau results in a complex oceanographic environment, with potential for dynamic mixing of sub-Antarctic and Antarctic fauna. Furthermore, the High Nutrient Low Chlorophyll (HNLC) water that flows over the northern plateau is subject to natural iron fertilization from the shallow bathymetry (< 700 m), leading to extensive phytoplankton blooms each summer, particularly to the southeast of the Kerguelen Islands. The Heard Island region on the central plateau has been relatively underexplored. In January 2004, the Heard Island Predator-Prey Investigation and Ecosystem Study (HIPPIES) conducted macrozooplankton (RMT-8 trawl) and micronekton (IYGPT trawl) sampling in foraging areas used by top predators in the vicinity of the island. Macrozooplankton and micronekton were sampled day and night from three depth strata (0100 m, 100300 m and 300600 m). In the area south and east of Heard Island, over bathymetry ≥1000 m depth, the water column had characteristics of the southern branch of the Polar Front (S-PF) and the macrozooplankton and micronekton were dominated by Antarctic Zone fauna (e.g., the euphausiids Euphausia triacantha and Euphausia frigida, and the myctophids Krefftichthys anderssoni, Electrona antarctica, Gymnoscopelus braueri and Gymnoscopelus nicholsi). Shallow slope and shelf stations were located north of the S-PF and the macrozooplankton assemblages were influenced by Polar Frontal Zone species (e.g., Euphausia vallentini), while the shelf micronekton were dominated by the bentho-pelagic channichthyids Champsocephalus gunnari and Channichthys rhinoceratus, together with G. nicholsi. Most macrozooplankton migrated from the deep epipelagic (100300 m) into the surface epipelagic (<100 m) at night, although some macrozooplankton occurred at high densities in the surface epipelagic during the day (e.g., Rhincalanus gigas, Themisto gaudichaudii). Most micronekton species occurred in the mesopelagic layers (300600 m) during the day, and migrated into the deep and surface epipelagic at night. Only the small but very abundant K. anderssoni utilized the top 300 m during the day. The vertical distributions of macrozooplankton and micronekton are discussed with respect to the foraging behavior and diets of top predators.

Item Details

Item Type:Refereed Article
Keywords:Kerguelen Plateau, food webs, top predators, zooplankton, nekton, macrozooplankton, micronekton, mesopelagic, vertical migration, community structure, Antarctic, Heard island, Southern Ocean
Research Division:Biological Sciences
Research Group:Ecology
Research Field:Marine and estuarine ecology (incl. marine ichthyology)
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the environmental sciences
UTAS Author:Swadling, KM (Associate Professor Kerrie Swadling)
ID Code:144814
Year Published:2021
Deposited By:Ecology and Biodiversity
Deposited On:2021-06-14
Last Modified:2021-06-21
Downloads:0

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