11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 11: From Molecules to Moonbeams: How is Reproductive Timing Regulated in Coral Reef Organisms?
11-17
The Annual Timing Of Coral Spawning: A Role For Rainfall?
Judith MENDES* 1,2
1 Department of Life Sciences, University of the West Indies, Kingston, Jamaica, 2 Bellairs
Research Insititute of McGill University, St James, Barbados
Sea surface temperature (and the solar insulation responsible for temperature) is the most
frequently cited trigger for the annual timing of coral spawning. We conducted a metaanalysis
of spawning time at 42 sites worldwide in relation to sea surface temperature and
rainfall. The data on temperature, rainfall and spawning time were examined by loglinear
analysis. The log-linear model of best fit included al 2-way interactions
(temperature x rainfall, spawning x temperature, and spawning x rainfall; chi-squared =
41.06, df = 39, p = 0.38). The chi-squared test is not significant indicating that the values
predicted by the model are not significantly different from the observed values. One can
thus conclude that the model is sufficient to explain the time of spawning. Tests of partial
association show that the magnitude of the temperature effect was greater than that for
rainfall, however, on its own, temperature was insufficient to explain the time of
spawning. Only when the interaction between rainfall and spawning was incorporated in
the model could the time of spawning be adequately explained. According to our model,
temperature and rainfall have opposite effects on the time of spawning with the
likelihood of spawning increasing with increasing temperature and decreasing with
increasing rainfall. Two possible roles underlying the contribution of rainfall to spawning
time are, firstly, that spawning during period of low rainfall reduces the risk of
catastrophic reproductive failure caused by gametes coming into contact with rain diluted
surface water. Secondly, spawning prior to the peak of heavy rainfall, may also increase
the food available for newly-settled, azooxanthellate coral polyps and the chance of such
polyps acquiring zooxanthellae. A similar association of spawning to heavy rainfall
(typhoons) has recently been described for the abalone Haliotis diversicolor (Onitsuka et
al, 2007)
11-18
Global Patterns And Environmental Controls Of Sexual Reproduction in
Scleractinian Reef Corals
Peter HARRISON* 1
1 Coral Reef Research Centre, School of Environmental Science and Management,
Southern Cross University, Lismore, NSW, Australia
Research on sexual reproductive patterns of scleractinian reef corals continues to expand
rapidly, providing important insights into proximate environmental controls and
evolutionary constraints on coral reproductive success. An updated global review of
scleractinian coral reproductive patterns confirms that hermaphroditic broadcast
spawning remains the dominant pattern among scleractinian corals studied to date, with
fewer gonochoric broadcast spawning or brooding species known. In a few species,
mixed patterns of sex allocation and both brooding and broadcast spawning occur. Sea
temperature and light in various forms are key environmental factors that interact to
control reproductive cycles, lunar periodicity and spawning periods in reef corals. These
proximate cues also strongly influence breeding periods and reproductive synchrony
among coral species, with mass spawning (involving many species) or multispecific
spawning (with fewer species) prevalent on many tropical and subtropical reefs.
Protracted breeding periods and less synchronous reproduction are evident among reef
corals on some equatorial reefs. A new model is developed that integrates thermal and
light energy optima as primary determinants of coral reproductive patterns, with
suboptimal conditions resulting in impaired reproduction and reduced reproductive
success. Sea temperature also significantly influences coral larval development,
competency and settlement success, with more rapid larval attachment and increased
likelihood of localised settlement, but lower post-settlement survival, under elevated
temperature. This has very important implications for reef connectivity and gene flow
among coral populations in a rapidly warming global climate, and the future viability of
some isolated reef systems.
11-19
Solar Insolation Drives Reproductive Schedules Of Reef Corals: A Long Road in The
Search For Proximate And Ultimate Cues
Robert VAN WOESIK* 1
1 Biological Sciences, Florida Institute of Technology, Melbourne, FL
Coral populations depend on the formation of sex cells (gametes) for survival and adjustment to
climatic shifts. Since adaptation involves differential-reproductive rates of individuals in
populations, it is critical to understand global reproductive schedules of corals. This study tested
the hypothesis that annual rising Sea Surface Temperatures (SSTs) and solar insolation are
related to gamete maturation and synchronous gamete release in the Atlantic and Indo-Pacific
Oceans. Reproductive schedules of corals were positively related to solar insolation cycles, and
SSTs were poor predictors of coral spawning schedules. Near the equator coral spawning
coincided with the equinoxes, showing two annual events. While proximate cues may explain
how spawning synchronicity develops, there is a need to identify ultimate cues to ask why
questions, including: 1) Why do such patterns exist? and 2) What is the long-term advantage (or
adaptive significance) of such synchronized patterns? There is a strong positive relationship
between the derivative of solar insolation and mean-wind speed, suggesting that rates of solar
insolation change are strong predictors of mean-wind speed. This infers that corals appear to
synchronize mass spawning during seasonally calm periods; which clearly agrees with recent
genetic evidence of local dispersal and high local retention. Synchronization during calm
periods would have rapidly evolved through selection outside the seasonally calm periods,
because gametes and larvae would have been lost from the local species pool. Therefore, while
solar insolation may be the proximate cue, the strong evolutionary filter (the ultimate cue) may
have been the calm periods when insolation was not changing rapidly, which in turn facilitated
local larval retention. This research demonstrates that solar insolation strongly influences coral
reproductive schedules worldwide, and synchronization enhances time-varying differences in
reproductive output and fitness because it occurs at times of low regional wind speeds that
facilitate high local larval retention.
11-20
Predicting patterns of coral spawning at multiple scales
Andrew BAIRD* 1 , James GUEST 2
1 ARC CoE Reef Studies, James Cook University, Townsville, Australia, 2 School of Biology,
Newcastle University, Newcastle upon Tyne, United Kingdom
Early theoretical work predicted that the reproductive season of widespread organisms should
be more extended near the equator than at high latitudes because conditions favourable for
gametogenesis persist year round. Similarly, it was believed that synchrony among both
populations and species would be lower at the equator because there are fewer good cues in the
tropics where annual fluctuations in environmental variables are lower. Here, we present data
from numerous locations within the Indo-Pacific which indicates that multi-specific
synchronous spawning is a characteristic feature of all Acropora assemblages and further, at
large scales, spawning episodes are highly predictable. In the central Indo-Pacific, for example,
the majority of reproductive output is concentrated in brief periods following full moons at the
beginning and end of the monsoon. Above approximately 28-30 degrees latitude, and possibly
at some sites in the cental Pacific, this pattern breaks down and the spawning episode is
progressively one month later in the season for every 2-400 km further from the equator. At
smaller scales the patterns are far less predictable. For example, in the central GBR peak
spawning times within sub-populations of a single species can vary dramatically over very
small scales. In conclusion, while large scale patterns in coral spawning seasonality may be
relatively predictable, detailed studies at the local scale are required to determine precisely
when a given sub-population will spawn.
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