11th ICRS Abstract book - Nova Southeastern University

12-27
Interaction Between Fishing And Bleaching On Kenyan Coral Reefs Moderated By
Disturbance History
Emily DARLING* 1 , Tim MCCLANAHAN 2 , Isabelle CÔTÉ 1
1 Simon Fraser University, Burnaby, BC, Canada, 2 Wildlife Conservation Society, Bronx,
NY
Coral reef ecosystems are affected by many stressors. The possibility these stressors
interact synergistically causes conservation concern, but such non-linear effects remain
untested in nature. We examined the independent and interactive effects of two stressors,
fishing and bleaching, on coral community structure using a 16-year time series of
monitoring data from Kenyan reefs. While both fishing and a mass coral bleaching event
in 1998 decreased hard coral cover, these stressors did not interact synergistically to
accelerate coral decline. Instead, fishing and bleaching interacted antagonistically.
Following 1998, hard coral cover on unfished reefs declined 74% (relative to prebleaching
cover) compared to 48% on fished reefs. Multivariate community analyses
suggest that the non-synergistic interaction between fishing and bleaching may be
explained by changes in coral community structure associated with fishing history. Prior
to 1998, unfished reefs had diverse coral assemblages (dominated by branching Acropora
and plating Montipora) that were not resistant to the 1998 bleaching event. In contrast,
fished reefs, composed primarily of massive and branching Porites, were both more
resistant to and recovered more quickly from bleaching. Decades of fishing pressure thus
appears to have favoured low-diversity disturbance-tolerant coral communities. By
contrast, unfished reefs may be refugia for high-diversity disturbance-sensitive
communities. We suggest that disturbance history, community susceptibility, and tradeoffs
between diversity and resilience can moderate interactions between multiple
stressors and may be important factors determining resilience to future large-scale
climate events.
12-28
Great Barrier Reef Coral Communities: Resilient in the 1980s but Struggling in the
2000s
Terry DONE* 1 , Lyndon DEVANTIER 2 , Emre TURAK 2 , Mary WAKEFORD 2 , Abbi
MCDONALD 2 , Craig JOHNSON 3
1 Australian Institute of Marine Science, Townsville, Qld, Australia, 2 Australian Institute
of Marine Science, Townsville, 4810, Qld, Australia, 3 University of Tasmania, Hobart,
Australia
Coral communities were monitored using photography and video at 30 Great Barrier Reef
study sites in the period 1980 – 2005. At Pandora Reef in the 1980s, regional elevation of
land-based nutrients did not prevent spectacular recovery of coral cover and diversity
following a sequence of environmental disturbances in the 1970s. There was high coral
mortality in some habitats in the 1998 bleaching, and the standing dead corals were then
flattened by a 2000 cyclone. Degree of impact and extent of recovery was related to
marked differences around the reef in benthic species composition and relative
abundance, notably fleshy algae, soft corals, poritids and acroporids. Relative paucity of
larval derived recruits and viable fragments in 2005 suggests the strong coral population
resilience of the 1980s will not be repeated in the short term, especially reflecting
regional paucity in Acropora broodstock. At a small (32 m2) site at Lizard Island there
were three acute disturbance events followed by good coral recovery and no tendency for
phase-shift: 1982- a combination of coral bleaching and Crown-of-Thorns starfish; 1990 -
cyclone waves and 1996 - Crown-of-Thorns starfish. However beyond 1996,
observations and modeling using Johnson’s Compete © Cellular Automaton model
suggest the area may be subject to annual chronic background mortality. The apparent
retardation of coral recovery may be exacerbated by projected reduced intervals between
disturbances associated with global climate change. However hopefully recovery
prospects will be improved as region-wide benefits of improved GBR-wide management
introduced in 2004 take effect: i.e. an eightfold increase in the area of no take protected
areas, and the initiation of actions to improved coastal water quality.
Oral Mini-Symposium 12: Reef Resilience
106