Exploring South Africa’s southern frontier: A 20-year vision for polar research through the South African National Antarctic Programme

Antarctica, the sub-Antarctic islands and surrounding Southern Ocean are regarded as one of the planet’s last remaining wildernesses, ‘insulated from threat by [their] remoteness and protection under the Antarctic Treaty System’1 . Antarctica encompasses some of the coldest, windiest and driest habitats on earth. Within the Southern Ocean, sub-Antarctic islands are found between the Sub-Antarctic Front to the north and the Polar Front to the south. Lying in a transition zone between warmer subtropical and cooler Antarctic waters, these islands are important sentinels from which to study climate change.2 A growing body of evidence3,4 now suggests that climatically driven changes in the latitudinal boundaries of these two fronts define the islands’ short- and long-term atmospheric and oceanic circulation patterns. Consequently, sub-Antarctic islands and their associated terrestrial and marine ecosystems offer ideal natural laboratories for studying ecosystem response to change.5 For example, a recent study6 indicates that the shift in the geographical position of the oceanic fronts has disrupted inshore marine ecosystems, with a possible impact on top predators. Importantly, biotic responses are variable as indicated by different population trends of these top predators.7,8 When studied collectively, these variations in species’ demographic patterns point to complex spatial and temporal changes within the broader sub-Antarctic ecosystem, and invite further examination of the interplay between extrinsic and intrinsic drivers

Exploring South Africa's southern frontier : a 20-year vision for polar research through the South African National Antarctic Programme

Antarctica, the sub-Antarctic islands and surrounding Southern Ocean are regarded as one of the planet’s last remaining wildernesses, ‘insulated from threat by [their] remoteness and protection under the Antarctic Treaty System’. Antarctica encompasses some of the coldest, windiest and driest habitats on earth. Within the Southern Ocean, sub-Antarctic islands are found between the Sub-Antarctic Front to the north and the Polar Front to the south. Lying in a transition zone between warmer subtropical and cooler Antarctic waters, these islands are important sentinels from which to study climate change. A growing body of evidence now suggests that climatically driven changes in the latitudinal boundaries of these two fronts define the islands’ short- and long-term atmospheric and oceanic circulation patterns. Consequently, sub-Antarctic islands and their associated terrestrial and marine ecosystems offer ideal natural laboratories for studying ecosystem response to change. For example, a recent study indicates that the shift in the geographical position of the oceanic fronts has disrupted inshore marine ecosystems, with a possible impact on top predators. Importantly, biotic responses are variable as indicated by different population trends of these top predators. When studied collectively, these variations in species’ demographic patterns point to complex spatial and temporal changes within the broader sub-Antarctic ecosystem, and invite further examination of the interplay between extrinsic and intrinsic drivers.http://www.sajs.co.zaam2017GeneticsMammal Research InstituteZoology and Entomolog

Reappraisal of the Trophic Ecology of One of the World’s Most Threatened Spheniscids, the African Penguin

<div><p>Many species of seabirds, including the only penguin species breeding on the African continent, are threatened with extinction. The world population of the endangered African penguin <i>Spheniscus demersus</i> has decreased from more than 1.5 million individuals in the early 1900s to c.a. 23 000 pairs in 2013. Determining the trophic interactions of species, especially those of conservation concern, is important when declining numbers are thought to be driven by food limitation. By and large, African penguin dietary studies have relied on the identification of prey remains from stomach contents. Despite all the advantages of this method, it has well known biases. We therefore assessed the African penguin’s diet, using stable isotopes, at two colonies in Algoa Bay (south-east coast of South Africa). These represent over 50% of the world population. Various samples (blood, feathers, egg membranes) were collected for carbon and nitrogen stable isotope analyses. Results indicate that the trophic ecology of African penguins is influenced by colony, season and age class, but not adult sex. Isotopic niches identified by standard Bayesian ellipse areas and convex hulls, highlighted differences among groups and variability among individual penguins. Using Bayesian mixing models it was for the first time shown that adults target chokka squid <i>Loligo reynaudii</i> for self-provisioning during particular stages of their annual cycle, while concurrently feeding their chicks primarily with small pelagic fish. This has important ramifications and means that not only pelagic fish, but also squid stocks, need to be carefully managed in order to allow population recovery of African penguin.</p></div

Biological characteristics of the African penguins sampled on Bird and St Croix islands in 2013.

<p>Biological characteristics of the African penguins sampled on Bird and St Croix islands in 2013.</p

Spatial variation in the isotopic space depicting niche areas for African penguins blood (a, b), feathers (c, d) and egg membrane (e, f) using convex hull areas (a, c, e; [31]) and standard ellipse areas corrected for small sample size (b, d, f; [30]).

<p>Females (circles), males (triangles) and blues (crosses) sampled on Bird and St Croix islands are represented in black and grey, respectively.</p

Stable isotope mixing model (MixSIAR) results with predicted diet proportions (median values and 5^th to 95^th percentiles) of each five potential prey species compared to δ¹³C and δ¹⁵N values of African penguin blood.

<p>White: females, light grey: males, dark grey: blues.</p

Seasonal variation in the isotopic space depicting niche areas for African penguin blood (a, b) and feathers (c, d) using convex hull areas (a, c; [31]) and standard ellipse areas corrected for small sample size (b, d; [30]).

<p>Females (circles) and males (triangles) were sampled in both non-breeding and breeding periods on Bird Island and are represented in black and grey, respectively.</p

Carbon (a) and nitrogen (b) stable isotope (‰), and C:N ratio (c) values of blood, feathers and egg membranes of African penguins breeding in Algoa Bay.

<p>Carbon (a) and nitrogen (b) stable isotope (‰), and C:N ratio (c) values of blood, feathers and egg membranes of African penguins breeding in Algoa Bay.</p