11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 25: Predicting Reef Futures in the Context of Climate Change
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Analysis of Fish Abundance in the Gulf of California, and Projection of Changes by
Global Warming
Arturo AYALA BOCOS* 1 , Hector REYES BONILLA 1
1 Biologia Marina, Universidad Autonoma de Baja California Sur, La Paz, Mexico
The Gulf of California is considered as a key area for conservation worldwide, and has
high endemism and diversity of its reef fish fauna. This group might be affected by global
warming, because they are ectotherms and temperature may increase several degrees by
2100. This study analyze the latitudinal patterns of abundance of the 20 most abundant
reef fishes in the Gulf of California, and evaluate possible changes caused by the
temperature increment. Stationary censuses of fishes (N= 147) were done in six regions,
from Los Angeles Bay (28°N) to Los Cabos (22°N). For each region we obtained the
following information: mean, minimum and maximum surface temperature,
photosynthetic pigments, and nitrate, phosphate and silicate concentrations. These factors
were included in stepwise regressions to evaluate its influence on each species, and the
equations were used to project change in numbers as a result of warming, by changing the
coefficients linked to mean temperature in 1°, 2° and 3° C. The results of the models
indicated that as temperature increases, four species reduce their abundance, fourteen
became very similar in numbers along the gulf, and two were unaffected. Ten species will
extend its range to areas where they are currently absent. Finally, richness and diversity
(H´) of the “future” communities will increase significantly; the highest value occurred in
the 1°C increase model, but afterwards the values reduce gradually. Our conclusions are:
a) the Gulf of California reef fish fauna will not react homogeneously to temperature
increase; b) some species may change their distribution; c) ecological indices reflect the
predicted qualitative shift in assemblage composition; and d) the differential responses of
the species may cause an ecological imbalance in teleost assemblages of the gulf in
following decades.
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Climate Change And The Future For Coral Reef Fishes
Philip MUNDAY* 1,2 , Geoffrey JONES 2,3 , Morgan PRATCHETT 3 , Ashley WILLIAMS 4
1 ARC Centre of Excellence for Coral Reef Studies, James Cook University,
Towwnsville, Australia, 2 School of Marine and Tropical Biology, James Cook
University, Townsville, Australia, 3 ARC Centre of Excellence for Coral Reef Studies,
James Cook University, Townsville, Australia, 4 Fishing and Fisheries Research Centre,
James Cook University, Townsville, Australia
We review and predict the likely impacts of climate change on coral reef fishes. Changes
to ocean temperature, pH, currents, and extreme weather events will affect reef fishes
through impacts on individual performance, trophic linkages, recruitment dynamics,
population connectivity and other ecosystem processes. The most immediate and
identifiable impacts will be changes in the composition of reef fish communities and loss
of biodiversity as a result of coral bleaching. Coral-dependant fishes suffer the most rapid
declines in abundance following coral bleaching. However, we predict that many other
species will exhibit longer-term declines due to loss of settlement habitat and erosion of
the structural complexity of reef habitats. Continued degradation of coral reefs from
climate change will lead to impoverished reef fish communities. Increased ocean
temperature will affect the physiological performance and behaviour of reef fishes,
especially during the larval phase. Small increases in temperature might tend to favour
larval survival, but this could be counteracted by negative effects on reproduction. We
predict that already variable recruitment will become more unpredictable, with more
good recruitment events and more recruitment failures, especially in locations where food
supply is patchy or unreliable. A substantial number of species could exhibit range shifts,
with potential implications for extinction risk of small-range species near reef margins.
Finally, the potential for adaptation to climate change needs more consideration. Many
coral-reef fishes have geographical ranges spanning a wide temperature gradient and
many have short generation times. These characteristics are conducive to acclimation and
local adaptation to climate change, and provide some hope that resilient species might
adapt to climate change if immediate action is taken to stabilise Earth’s climate.
25-48
Increased Predation Rates On Coral-Dwelling Fishes Associated With Bleached Coral
Hosts
Darren COKER* 1 , Morgan PRATCHETT 1 , Philip MUNDAY 1
1 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville,
Australia
Climate-induced coral bleaching frequently leads to declines in the abundance and diversity of
coral associated fishes, though the proximate causes of these declines remain largely unknown.
More specifically, it is unclear why coral-dwelling fishes rapidly disappear from bleached coral
hosts, even though these corals continue to provide effective physical habitat structure. The
purpose of this study was to test whether fishes that remain on bleached coral hosts are more
susceptible to predation. Using controlled aquaria-based experiments, we compared predation
rates on coral-dwelling fishes (Dascyllus aruanus, Pomacentrus moluccensis) associated with
i) healthy, ii) bleached, iii) dead and iv) algal covered colonies of the coral, Pocillopora
damacornis. Experiments were conducted by placing two prey fish of each species with one of
the four different habitat types in large glass aquaria. After 1 hour, a single predator
(Pseudochromis fuscus) was introduced and survivorship of prey was recorded over 75 hours.
This study revealed a 75% survivorship of coral-dwelling damselfishes in tanks with healthy
coral colonies, wheras only 67% and 63% of damselfishes survived in tanks with bleached
versus dead coral hosts, respectively and 58% with algal covered corals. It is possible therefore
that the loss of coral healthy coral tissue and pigmentation influenced the ability of prey to
elude predation.
It is apparent therefore, that as coral habitat degrades from healthy to algal cover, survivorship
of associated fish decreases by 17% due to predation. It is apparent therefore that healthy coral
plays an important role in moderating predation interactions among coral reef fishes. We
conclude that increasing susceptibility to predation may provide significant motivation for
coral-dwelling fishes to rapidly vacate recently bleached coral hosts. Moreover, increased
predation may contribute greatly to declines in abundance of coral-dwelling damselfishes
following widespread coral bleaching.
25-49
Effects of climate-induced coral bleaching on coral reef fishes.
Morgan PRATCHETT* 1 , Philip MUNDAY 1 , Shaun WILSON 1 , Nicholas GRAHAM 2 , Joshua
CINNER 1 , David BELLWOOD 1 , Geoff JONES 1 , Nicholas POLUNIN 2 , Tim MCCLANAHAN 3
1 ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville,
Australia, 2 School of Marine Science & Technology, University of Newcastle, Newcastle-upon-
Tyne, United Kingdom, 3 Wildlife Conservation Society, New York, NY
Global climate change is having devastating effects on habitat structure in coral-reef
ecosystems, owing to extreme environmental sensitivities and consequent bleaching of reefbuilding
scleractinian corals. Coral bleaching and loss of live coral may also lead to longer-term
declines in topographic complexity. This review identifies coral cover and topographic
complexity as critical and distinct components of coral-reef habitats that shape communities of
coral-reef fishes. Coral loss has the greatest and most immediate effect on fishes that depend on
live corals for food or shelter, and many such fishes may face considerable risk of extinction
with increasing frequency and severity of bleaching. Coral loss may also have longer-term
consequences for fishes that require live corals at settlement, which are compounded by
devastating effects of declining topographic complexity. Topographic complexity moderates
major biotic factors, such as predation and competition, contributing to the high diversity of
fishes on coral reefs. Many coral-reef fishes that do not depend on live coral are dependent on
the topographic complexity provided by healthy coral growth and will be adversely affected by
long-term degradation of coral reef habitats following severe coral bleaching. Urgent action on
the fundamental causes of climate change and appropriate management of critical elements of
habitat structure (coral cover and topographic complexity) are key to ensuring long-term
persistence of coral-reef fishes.
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