De Hoop weekend

Eric and Bryan (snake dude) taking in the vast intertidal wave-cut platforms. The kelps occupy the vertical fringes of the platforms in the lower intertidal.
Eric and Bryan (snake dude) taking in the vast intertidal wave-cut platforms. The kelps occupy the vertical fringes of the platforms in the lower intertidal.

Last weekend a group of us went to the De Hoop Nature Reserve, about 70 km east of the Southern-most tip of the African continent, Cape Agulhas. The intention was to install more temperature recorders there to form part of the South African Coastal Temperature Network, and to explore some of the kelp beds there. Sadly, neither of the objectives could be achieved due to permitting issues and undiveable sea conditions (although Eric did snorkel in some sheltered areas). A temperature recorder already exists around Koppie Alleen, but we also wanted to place one at Noetsie further to the east.

 

The decrease seawater temperature trend at Cape Agulhas.
The decreasing seawater temperature trend at Cape Agulhas.

The region around Koppie Alleen  is the subject of our scrutiny, as a recent paper (Bolton et al., 2012) has shown that kelp (Ecklonia maxima) has only recently established itself there, after historically being limited to a region about 73 km to the west. Certainly the kelps look quite different from their counterparts elsewhere in the Western Cape: for one, they are much smaller in stature. Also, there are questions about whether or not they are hybrids of E. maxima and the smaller E. radiata, which is abundant along the south coast.

Our existing data (AJ Smit, unpublished) show that the region is cooling, as we have hypothesised in the Bolton et al. (2012) paper. See the second figure here.

Reference

Bolton, J. J., Anderson, R. J., Smit, A. J., & Rothman, M. D. (2012). South African kelp moving eastwards: the discovery of Ecklonia maxima (Osbeck) Papenfuss at De Hoop Nature Reserve on the south coast of South Africa. African Journal of Marine Science, 34(1), 147–151.

 

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