|The effect of grain size on the burrowing of two Donax species|In: Journal of Experimental Marine Biology and Ecology. Elsevier: Tokyo; Oxford; New York; Lausanne; Shannon; Amsterdam. ISSN 0022-0981, more
Sand particle diameter; Swash exclusion hypothesis; Burrowing; Bivalve
|Authors|| || Top |
- Nel, R.
- McLachlan, A.
- Winter, D.P.E.
Donax serra and Donax sordidus are bivalves inhabiting the intertidal area of sandy beaches in the Eastern Cape, South Africa. This study investigated the effect of grainsize on the burrowing performance of these twospecies in the laboratory to elucidate the influence of grainsize on the longshore distribution of Donax populations and, consequently, the importance of particle diameter in swash exclusion. Burial time, burrowing cycles and a burrowing rate index were obtained for both species in nine well-sorted sediments with grainsizes ranging 90–2000 µm. The burial times of both D. serra and D. sordidus were positively correlated with shell length. Burrowing performance of both species was influenced by grainsize. Fastest burrowing times were measured in the fine and medium sediments (125–500 µm) but increased towards the very fine (90–125 µm) and coarse extremes (500–2000 µm). Burial time experiments were extended to test how D. serra would behave in sediments with more natural properties and were, therefore, repeated in mixed sands of different sortings. Sediment sorting had a positive influence on the burrowing times of D. serra. Burrowing time was fastest in well-sorted sediments and slowest in moderately sorted sediments, especially those containing fractions of sands >500 µm. Burial times approximating the swash periods on dissipative beaches (~32 s) were measured for grainsizes <500 µm. It is, therefore, predicted that most D. serra individuals are able to burrow between swashes on dissipative beaches. However, only the smallest individuals (~15 mm) would be able to burrow between swashes on reflective beaches with swash periods approximating 15 s. The smaller (maximum) size of D. sordidus reduces burial time and should, therefore, enable this slower burrowingspecies to bury successfully under most dissipative/intermediate conditions.