Kelp-plucking: coastal erosion facilitated by bull-kelp Durvillaea antarctica at subantarctic Macquarie Island

Abstract

Erosion of bedrock from lower intertidal reefs by waves acting on attached plants of bull-kelp (Durvillaea antarctica) was investigated over one year at Macquarie Island, Southern Ocean. At a site on the more sheltered east coast, such erosion occurred during four separate storms, each casting up 834–1078 large kelp plants km−1 of coast, of which 30–45% were still attached to jagged, freshly quarried bedrock fragments over 2.5 cm long. The largest fragment weighed was 74.6 kg; rounded cobbles and boulders attached to kelp plants and weighing up to 102.2 kg (and probably more than 160 kg) were also cast up on beaches. 19–21% of the standing crop of large kelp plants was removed by storms during the year of observation. Break points for 10 kelp stipes were found to be at least 90–161 kg. Total annual erosion by kelp-plucking is at least 1.56 tonnes of rock km−1 of coast. However, in terms of erosion this computes to only 0.1 mm yr−1, far below the rate of uplift of the island.

Seasonal variation in floating persistence of detached Durvillaea antarctica (Chamisso) Hariot thalli

“…Furthermore, D. antarctica possesses a unique gas-filled honeycomb structure within the blades, which gives strength and extreme buoyancy, and offers protection against potential damage by the strong waves in its natural habitat (Skottsberg 1941, Santelices et al 1980, Hay 1994, Koehl 1999. However, during periods of strong waves, D. antarctica suffers substantial hydrodynamic drag at the base of the stipe, resulting in detachment of thalli from the rocks with or without holdfasts (Smith and Bayliss -Smith 1998.…”

Quantifying the attachment strength of climbing plants: A new approach

“…For the hairy pads, it was established that the animal body mass is correlated to the grade of contact splitting in the attachment system [22,23]. Furthermore, sessile marine organisms such as algae or sessile invertebrates exhibit strong permanent adhesion to substrates under severe environmental conditions [24][25][26][27][28][29][30][31]. In particular, the attachment systems of mussels have been studied extensively and were used as concept generators for biomimetic applications [32][33][34].…”

Macroalgal Distribution Patterns and Ecological Performances in a Tidal Coastal Lagoon, with Emphasis on the Non-indigenous Codium Fragile ssp. Tomentosoides

“…This weight is an order of magnitudes lower than most measured break forces, and entrainment should therefore be of main importance for algae attached to unconsolidated shells (Ben Avraham 1971, Dromgoole 1982, Smith & Bayliss-Smith 1998, even though sediment-shell resistance was ignored. Thus, size-limitations are less likely on single shells, partly explaining why these algae can be found as larger thalli in Hog Island Bay compared to algae attached to consolidated substrates (pers.…”