Biology Reference
In-Depth Information
or filamentous epiphytes (Chisholm et al. 2000). Lake Conjola (NSW, Australia) is
very popular with recreational boaters, water skiers, jet skiers, and fishermen, espe-
cially during the summer holiday season. On ten dates between 17 December and
25 January 2007, 13.9 ± 2.3 boats per hour (mean ± S.E.) in Lake Conjola passed
adjacent to
Caulerpa
meadows (L. Walters, P. Sacks, A. Davis, D. Burfiend, unpub-
lished data). On the same dates and at the same locations, a mean of 34.0 ± 19.8
fragments (
n
= 10) were found in a 100 × 2 m band transect along the shoreline
where
C. taxifolia
meadows were less than 2 m offshore. Boating traffic in Moreton
Bay waterways in February 2007 was lower and consisted primarily of large sail-
boats, small fishing boats, and ferries (5.9 ± 1.0 boats/h), and we found about half
as many fragments (19.7 ± 4.4) in similar transects in Moreton Bay waters (
n
= 14)
(L. Walters, P. Sacks, A. Davis, D. Burfiend, unpublished data). Using Kruskal-
Wallis nonparametric ANOVAs, there was significantly more boating activity in
Lake Conjola (
F
= 19.17;
p
= 0.001) but no significant difference in the number of
fragments (
F
= 0.19;
p
= 0.669). Ninety-eight percent and 99.9% of the fragments
from Lake Conjola and Moreton Bay, respectively, were greater than 10mm in
length, allowing us to predict that the fragments will be successful. On the contrary,
Wright (2005) found more asexual reproduction via fragmentation in Moreton Bay
populations than at the invasive locations.
Fragments can be spread by anthropogenic activities related to boating and fish-
ing (Sant et al. 1996; West 2003). In the Mediterranean, more fragments of
C. taxifolia
were found in locations where boats moored (Relini et al. 2000) and
most new outbreaks appeared in areas of high boating activity (Meinesz et al.
1993). West et al. (2007) determined that fragments of Australian
C. taxifolia
cre-
ated by all anchor types tested were of similar sizes. Eighty-two percent of anchors
lowered into
C. taxifolia
beds fragmented individuals, and the biomass removed on
a single anchor was as large as 49 g dry weight (West et al. 2007). Chains and ropes
also generated fragments when lowered onto a meadow of
C. taxifolia
(96% chains,
4% ropes). Once removed from the water, fragment survivorship increased with
clump size, protection from desiccation, and decreased exposure time (West et al.
2007). Likewise, Sant et al. (1996) found that fragments of aquarium
C. taxifolia
survived out of water in dark, humid conditions. Combined, the results suggest that
multiple anchorings within a limited area can greatly promote dispersal of
C. taxifolia
while much longer dispersal (greater than hundreds of meters) is also
possible when vessels travel long distances with fragments harbored inside anchor
lockers, attached to ropes, or entangled on boat trailers (West et al. 2007). West
et al. (2007) suggest that boaters may be more likely to discard larger, obvious
clumps of
C. taxifolia
from anchors, rope, and chains while smaller fragments may
be overlooked.
Fragment retention and attachment in
C. taxifolia
depends on season, hydrody-
namics, and water depth. In Italy, aquarium-strain fragments (15-cm stolon with
five fronds) survived best in summer months (Ceccherelli and Cinelli 1999a).
Thibaut (2001) found that fragment survival on the French coast in the summer in
10-m water on sandy bottoms was as great as 98%, whereas only 50% establish-
ment was found in shallower waters with more water motion. Many studies also
