The role of pioneers as indicators of biogeographic range expansion caused by global change in southern African coastal waters

Abstract

The South African coastline is just over 3000 km in length yet it covers three major biogeographic regions, namely subtropical, warm temperate and cool temperate. In this review we examine published information to assess the possible role of climate change in driving distributional changes of a wide variety of organisms around the subcontinent. In particular we focus on harmful algal blooms, seaweeds, eelgrass, mangroves, salt marsh plants, foraminiferans, stromatolites, corals, squid, zooplankton, zoobenthos, fish, birds, crocodiles and hippopotamus, but also refer to biota such as pathogens, coralline algae, jellyfish and otters. The role of pioneers or propagules as indicators of an incipient range expansion are discussed, with mangroves, zoobenthos, fishes and birds providing the best examples of actual and imminent distributional changes. The contraction of the warm temperate biogeographic region, arising from the intrusion of cool upwelled waters along the Western Cape shores, and increasingly warm Agulhas Current waters penetrating along the eastern parts of the subcontinent, are highlighted. The above features provide an ideal setting for the monitoring of biotic drivers and responses to global climate change over different spatial and temporal scales, and have

Range extension of a euryhaline crab, Varuna litterata (Fabricius, 1798) (Brachyura: Varunidae), in a climate change hot-spot

“…The southeastern coast of Australia, including NSW, has been identified as a global warming hot-spot, a region experiencing greater increases in temperature than the global average (Hobday & Lough, 2011). To our knowledge, this study is the first recorded range extension of any euryhaline invertebrate in this climate change hot-spot, and one of the few examples globally of a range extension by any euryhaline invertebrate in a climate change hot-spot (also see Whitfield et al, 2016). We do not regard our results as artefacts of limited past sampling as considerable field sampling has been conducted along the NSW coast since the 1950s by the Australian Museum and others (e.g.…”

Population irruption of the clam Meretrix morphina in Lake St Lucia, South Africa

“…5,20 The southernmost distribution of M. morphina was previously recorded as Maputo Bay and Inhaca Island (25°57'S).The new records from St Lucia (28°13'S) and Mlalazi (28°57'S) have now substantially extended this distribution southwards.…”

“…5 The population then declined and was not detected in the lake, most likely because of a severe drought that caused widespread desiccation and hypersalinity in the region from 2005 until 2011. 5 The system then experienced increased freshwater input, resulting in lower salinities from 2011 until 2014, during which time live M. morphina reappeared and their population gradually increased. In 2015, M. morphina became overwhelmingly abundant in St Lucia.…”

“…This occurrence represents another case of poleward range expansion, probably in response to global warming, as many such cases have already been documented along the South African coastline. 5 The mode of introduction into Lake St Lucia remains unresolved, but possible means involve either transport of veligers from Maputo Bay via the southward flowing Agulhas Current or humanmediated introduction of adults as bait for recreational fishing. 6 The St Lucia system is Africa's largest estuarine lake, a Ramsar Wetland of International Importance and a crucial part of the iSimangaliso UNESCO World Heritage Site.…”

Hydrology and water quality factors driving spatiotemporal analyses of zoobenthos in a pilot city in China

“…Specifically, CCA analysis of zoobenthos in Jinan City in the spring and chemical factors through Monte Carlo screening of differences with p < .05 as the threshold of significance yielded potassium ion levels as a chemical water quality factor with a very significant difference ( p = .0042). Pekcan‐Hekim et al (), Untiedt and MacKay (), and Whitfield et al () found that Na + , potassium ions, and reducing substances in water have important effects on the distribution of zoobenthos. The primary sensitive species of zoobenthos was Limnodrilus hoffmeisteri.…”