Recovery of an endangered Caribbean coral from parrotfish predation
Coral tissue loss was driven by a few exceptionally large predation
scars, but 87% of scars were small and likely to fully heal

Date:
December 14, 2020
Source:
California Polytechnic State University
Summary:
Orbicella annularis is an important Caribbean coral and an
endangered species, yet it is also frequently predated by
parrotfishes. Researchers have tracked the recovery of this coral
species from parrotfish predation. They found that O. annularis
coral tissue loss appears to be driven primarily by a few
exceptionally large parrotfish predation scars.

Fortunately, 87% of scars were small and likely to fully heal.



FULL STORY ========================================================================== Parrotfishes are abundant herbivores that primarily graze upon
algae, which may indirectly benefit corals by mitigating coral-algae competition. At a local scale, management efforts to increase populations
of parrotfishes are believed to be critically important to maintaining resilient, coral-dominated reefs.

Yet, some parrotfish species also occasionally graze coral --
a behavior known as corallivory. Corallivory can cause the partial
to total mortality of coral colonies and may have long-term impacts
such as reduced coral growth and reproductive capacity and increased susceptibility to disease. While evidence suggests that parrotfishes
likely have an overall net positive impact on coral communities, they
may have detrimental impacts on heavily predated coral species, such as
O. annularis.


==========================================================================
To better understand the consequences of corallivory for O. annularis, researchers from California Polytechnic State University evaluated
coral healing rates from parrotfish predation scars. With these data,
they developed a statistical model to predict long-term coral tissue loss
from snapshot surveys of parrotfish predation scars. This study, recently published in Coral Reefs, is the first to monitor coral healing rates
and recovery thresholds from parrotfish predation scars in the Caribbean.

Coral healing capacity The researchers monitored the healing of over
400 parrotfish predation scars on O. annularis coral colonies on the
Caribbean islands of St. Croix and Bonaire over two months. Their
research suggests that the majority of O. annularis healing occurs
within the first few weeks and that scars have minimal healing after approximately 45 days. Importantly, they found that scar size strongly influences coral healing rates and recovery thresholds. They observed
that smaller scars (?1.25 cm2) often fully heal, while larger scars
(?8.2 cm2) - - presumably resulting from repetitive, localized predation
by parrotfishes - - had minimal healing.

Predicted coral tissue loss They surveyed the size and abundance of
recent parrotfish predation scars present on O. annularis colonies at
a point in time and used their model to predict coral tissue loss from
these scars. They observed that 87% of scars were small (?1.25 cm2) and
their model predicted that these small scars would fully heal or result
in minimal tissue loss. In contrast, while only 6% of observed scars
were large (?8.2 cm2), their model predicted that these large scars had
minimal healing and would account for 96% of the total tissue loss for parrotfish predation.

Conclusions & future directions This study suggests that the immediate
negative consequences of parrotfish corallivory for O. annularis
appear to be driven primarily by a few exceptionally large predation
scars. Interestingly, there was no observable difference in healing
rates or total coral healing between islands despite stark contrasts in parrotfish and coral community composition on St. Croix and Bonaire. This suggests that these findings and this predictive model may be broadly applicable to other regions of the Caribbean. This study presents an
important advance in understanding the recovery of a heavily predated, ecologically important, and endangered Caribbean coral from parrotfish corallivory. The group's ongoing work seeks to address how the intensity
of parrotfish corallivory is influenced by the community composition of
corals and parrotfishes across multiple spatial scales and regions of
the Greater Caribbean.


========================================================================== Story Source: Materials provided by
California_Polytechnic_State_University. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Hannah S. Rempel, Kelly N. Bodwin, Benjamin I. Ruttenberg. Impacts
of
parrotfish predation on a major reef-building coral: quantifying
healing rates and thresholds of coral recovery. Coral Reefs, 2020;
39 (5): 1441 DOI: 10.1007/s00338-020-01977-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201214192336.htm

--- up 16 weeks, 7 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)