Larval settlement preference of a native bivalve: the influence of an invasive alga versus native substrata
Gribben, P and Wright, JT and O'Connor, WA and Steinberg, P, Larval settlement preference of a native bivalve: the influence of an invasive alga versus native substrata, Aquatic Biology, 7, (3) pp. 217-227. ISSN 1864-7790 (2009) [Refereed Article]
ABSTRACT: Recruitment patterns of marine invertebrates are strongly influenced by the habitat
preference of larvae as larvae can choose to settle (or not) in response to positive or negative cues.
High abundances of recruits of the native infaunal bivalve Anadara trapezia occur in the invasive
alga Caulerpa taxifolia compared to native habitats. Using controlled laboratory experiments, A.
trapezia larval habitat preference was investigated through exposure to available native (adult A.
trapezia, Zostera capricorni and sediment from unvegetated areas) and invasive (C. taxifolia and
sediments from C. taxifolia) substrata that co-occur in estuaries invaded by C. taxifolia in New South
Wales, Australia. When exposed to all substrata, larval settlement was significantly higher on adults
compared to all other substrata except Z. capricorni. Although settlement to C. taxifolia was low, larvae
did not reject it as settlement surface. In pairwise comparisons, larval settlement was always
higher on adults compared to all other substrata, although differences were only significant compared
to C. taxifolia and unvegetated sediments. There was no difference in settlement when larvae
were exposed to Z. capricorni and C. taxifolia. When offered a single substratum, larval settlement
was significantly higher on adults and Z. capricorni compared to all remaining substrata. Manipulations
of shells of adults indicated that larvae may be responding positively to biofilms on the surface
of shells. The data indicate that A. trapezia larvae prefer to settle on adults and, while they do not prefer
C. taxifolia, they do not reject it as a settlement surface. Therefore, C. taxifolia may serve as a sink
habitat for A. trapezia.
KEY WORDS: Anadara trapezia · Bivalve · Caulerpa taxifolia · Habitat choice · Habitat-forming invasive
species · Invasion biology · Larval settlement
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