Use of Eelgrass, <em>Zostera marina</em>, Wrack by Three Species of Ladybird Beetles (Coleoptera: Coccinellidae) in Prince Edward Island

Abstract

Large numbers of the introduced ladybird beetle, Coccinella septempunctata L., were present at Wood Islands and Green Point, Prince Edward Island, in wrack consisting primarily of Zostera marina L. (Eelgrass). The wrack occurred in a 0.5 to 1.0 m band parallel to the shore, and was from five to 25 cm thick. The other ladybirds, Propylea quatuordecimpunctata (L.), an introduced coccinellid also found in high numbers, and an individual of the native Hippodamia tredecimpunctata (Say) were found only at Wood Islands. At both sites the ladybird beetles occurred in the mid-intertidal zone along at least 100 m of shoreline, and were absent to rare on the terrestrial vegetation above the high tide mark. At four of the other eight sites surveyed, occasional individuals were present in the wrack, but they were no more abundant than could be observed on landward vegetation. Mean densities of C. septempunctata at the two primary sites were 52 m-2 (Green Point) and 410 m-2 (Wood Islands).

Ecology of freshwater shore zones

“…By virtue of its complex physical structure and high food availability, marine wrack supports large populations of invertebrates, typically dominated by dipterans, enchytraeid oligochaetes, collembolans, mites, and amphipods (e.g., Backlund 1945;Behbehani and Croker 1982;McLachlan 1983McLachlan , 1985Marsden 1991;Jedrezejczak 2002a, b;Romanuk and Levings 2003;Garbary et al 2004). Most of these species are detritivores or bacteriovores, and many are good colonizers, and so are able to take advantage of ephemeral wrack accumulations.…”

Halocladius variabilis(Diptera: Chironomidae): a marine insect symbiotic with seaweeds from the White Sea, Russia

“…The few strictly marine species are rarely conspicuous members of this environment, and terrestrial species are rarely abundant in the intertidal zone except in salt marshes and estuaries (e.g. Garbary et al , 2004). Consequently, insects are typically ignored in general textbooks of marine biology (e.g.…”