Population demographics and growth rate of Salpa thompsoni on the Kerguelen Plateau

Abstract

This study aimed to obtain the first estimates of S. thompsoni population dynamics and growth rates over the Kerguelen Plateau (Southern Indian Ocean). Micronekton, including salps, were repeatedly sampled during late summer to early autumn (26th February – 15th March 2018) at contrasting hydrological stations on the Kerguelen Plateau in the southern proximity of Kerguelen Islands. At two stations, S. thompsoni made up almost half of the micronekton biomass. Environmental conditions were important in determining the density and development of S. thompsoni populations. Growth rates (0.5–7.0% d−1) were higher than previously reported from the Antarctic Peninsula (0.3–4.6% d−1) but lower than near the Antarctic Polar Front (APF; 3.7–20.7% d−1). Despite warm surface waters (4–5 °C), low chlorophyll a concentrations restricted the salp populations from growing as fast as populations near the APF. Because the Kerguelen Plateau region deflects a branch of warm water southward towards Antarctica, more studies of S. thompsoni population dynamics across multiple seasons are needed to fully understand their importance over the Kerguelen Plateau and their invasion potential into higher latitudes.