South African kelp moving eastwards: the discovery ofEcklonia maxima(Osbeck) Papenfuss at De Hoop Nature Reserve on the south coast of South Africa

Abstract

Historical and recent evidence is documented to demonstrate that the eastern limit of the major kelp-bed forming seaweed Ecklonia maxima has moved c. 73 km eastward along the south coast of South Africa since 2006, after remaining unchanged for almost 70 years. A significant population has established at Koppie Alleen, De Hoop Nature Reserve, which has been monitored from 2008 to 2011. It is hypothesised that the eastward spread is limited by aspects of the inshore water temperature regime, and recent evidence suggests that gradual cooling along this coast may have caused the change in distribution. It seems likely that if a cooling trend continues along the South African south coast, kelp beds and their associated species will move farther eastward in future decades, affecting the ecology and livelihoods along this coast.

Global patterns of kelp forest change over the past half-century

“…The regional variability in change detected by our analysis is also a reflection of the diversity of multiscaled stressors whose effects vary in direction and magnitude across the geographic range of kelp forests (52)(53)(54). In some cases, the results of our analysis are consistent with predictions regarding regional trends in temperature, with decreases in abundance in locations where water temperatures are warming (e.g., Bassian ecoregion, Gulf of Maine, Scotian Shelf) (32,33) and increases where water temperatures are cooling (e.g., Western South Africa, Southern California Bight) (52,55). In many instances, literature suggests that climate-driven temperature change is acting synergistically with other stressors, such as the fishing of sea urchin predators [Bassian ecoregion (7)], pollution [South Australian Gulfs (56)], and invasive species [Scotian Shelf (32)] to cause the kelp declines detected by our analysis.…”

Kelps’ Long-Distance Dispersal: Role of Ecological/Oceanographic Processes and Implications to Marine Forest Conservation

“…The regional cooling of coastal environments observed in the southwestern Atlantic warm temperate province southern edge [55,65] corroborate the niche suitability described for the south of Brazil and Uruguay. The range extension of the South African kelp, Ecklonia maxima, was also ascribed to a regional cooling process [56]. Therefore, kelps are ecosystem engineers, responsible for most of the primary production where they occur.…”

“…in coastal areas of South America [55] and South Africa [56]. In South Africa, this resulted in the extension of the known distribution limits of Ecklonia maxima (Osbeck) Papenfuss.…”

A changing distribution of seabirds in South Africa—the possible impact of climate and its consequences

“…Kelp gulls may scavenge from fishing boats , but the food of crowned cormorants, mainly small fish that occur inter-tidally or inshore sub-tidally , and of white-breasted cormorants, mainly inshore and estuarine fish species (Crawford et al, 2013b), is unlikely to be influenced by commercial fishing activities. Although other factors, such as disturbance and predation, may have influenced decreases of white-breasted cormorants and kelp gulls off northwest South Africa (Crawford et al, 2013b;Whittington et al, in press), there was a concurrent extension in the range of the cool-water, kelp-bed forming seaweed Ecklonia maxima to the east of Cape Agulhas (Bolton et al, 2012) suggesting a cooling of the environment in the vicinity of Cape Agulhas. Prior to this extension, the breeding range of bank cormorants was broadly related to that of E. maxima (Cooper, 1981).…”