Deep bioturbation by Axius serratus in the Strait of Canso, Nova Scotia

Abstract

<p>The thalassinid crustaecan Axius serratus, was investigated in order to better understand its ecology and effect on the sediment, in the Strait of Canso, Nova Scotia. The shrimp, previously virtually unknown from Canadian waters, was found to be a common element of the benthic biota south of the Canso causeway. Axius exploits vast areas of sediment, and establishes semi-permanent burrows. Densities in the study area average from 9 to 15 per square meter and uniform spatial distributions were noted.</p> <p>Areas subject to heavy industrial pollution, termed barren zones, contain no forams, ostracods or molluscs. Axius serratus is the only invertebrate observed living in the barren zones, and may well serve as an indicator of water quality.</p> <p>Polyester resin casts show that the burrows are open to a depth of at least 2.9 m. - the deepest bioturbation event recorded: Burrows are lined with grass, and exhibit a knobby exterior similar to that of Ophiomorpha nodosa.</p> <p>Variations and trends in the mass physical properties of the sediment of the Strait of Canso are related to the distribution of Axius burrows. Sediment adjacent to burrows shows relatively higher values for grain density and mass unit weight. Effect is at maximum near burrow opening.</p>