coral barnacles

A B S T R A C T
Coral-associated invertebrates contribute much to the biodiversity of Caribbean coral reefs. Although the nature
of their symbiotic relation is usually not fully understood, they can cause damage to their hosts, especially when
they occur in high densities. The abundance of seven groups of coral-associated invertebrates was investigated on
reefs along the leeward side of Curaçao, southern Caribbean. In particular, coral barnacles (Pyrgomatidae),
boring mussels (Mytilidae: Leiosolenus spp.), gall crabs (Cryptochiridae), and Christmas tree worms (Serpulidae:
Spirobranchus spp.) were recorded together with their host corals by means of a photo survey at four depths (5,
10, 15, 20 m) and across seven sites with high and five sites with low eutrophication values (based on δ15N
isotope data). Feather duster worms (Sabellidae: Anamobaea), coral blennies (Chaenopsidae: Acanthemblemaria),
and worm snails (Vermetidae: Petaloconchus) were insufficiently abundant for thorough quantitative analyses.
The results show a decrease in the number of barnacles and Christmas tree worms per host over depth, which
could be related to the availability of their host corals. Sites with high δ15N values show a higher abundance of
barnacles and Christmas tree worms per host than sites with low values. This indicates that eutrophication could
be favourable for these filter feeding organisms but when their densities become too high, they tend to overgrow
their hosts and may become a threat to them.

A B S T R A C T

An increasing number of artificial reefs (ARs) are constructed to compensate for the loss of natural reefs (NRs),
but little is known about their benthic community composition. Here, we compared the densities of coral-
associated fauna (CAF) between a centuries-old manmade structure and the nearest NR at St. Eustatius,
eastern Caribbean. Overall, no significant difference in the density of CAF (coral-dwelling barnacles, crabs,
worms) was found between the NR and the AR, nor between the exposed and sheltered sides of each. Signifi-
cantly different densities of CAF related to host cover were observed among corals on both the AR and the NR.
Per host species, the AR did not show such differences in density between exposed and sheltered sides, although
these differences were observed on the NR. Thus, turbulence and host cover regulate the density of CAF, while
differences also depend on host species composition. Furthermore, from an ecological engineering perspective,
the present AR resembles the NR in overall design, but not in relief rugosity and surface structure, which are also
considered important contributors to the difference in species assemblages of the host corals and their CAF, even
after many decades of community development