Micronekton assemblages and bioregional setting of the Great Australian Bight: a temperate northern boundary current system (Australian Marine Science Association AMSA Conference 2018)

Summary

Micronekton communities and pelagic bioregionalisation of the Great Australian Bight (GAB), a regionally significant northern boundary current system, were studied as part of a multi-disciplinary pelagic ecosystem study.  Micronekton community structure, biomass and phenylalanine d¹⁵N isotopes differed between the eastern and central GAB.  The results are supportive of a hypothesis that the east GAB is an upwelling-dominated system.  Using lanternfishes (family Myctophidae) as a model group, a supervised cluster analysis indicated bioregional affinities between GAB pelagic fauna and the subtropical Indian Ocean region.  However, over the continental slope, the east GAB appears to have biogeographic affinities with the Subtropical Convergence and South Tasman Sea, concordant with oceanographic regimes on the GAB continental slope.  Lanternfish assemblage distribution was compared with existing bioregional schema based on physicochemical variables and the Delphic Method.  Lanternfish assemblage distributions support a regionalisation placing the GAB within a Subtropical Indian Ocean province, as opposed to a Subtropical Convergence province.  No single existing biogeographic schema adequately reflected lanternfish distributions, but boundaries from multiple physicochemical schema were able to be selected to erect data-driven hypothesised pelagic biogeography.  The data presented here will be useful for the management and monitoring of oil-and-gas developments and Marine Parks.