11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10-5
The Influence Of Water Quality, Larval Supply And Surrounding Benthos On
Coral Recruitment To Nearshore Reefs Of The Great Barrier Reef
Stephen J NEALE* 1 , Damien THOMSON 1 , Angus THOMPSON 1 , Britta
SCHAFFELKE 1
1 Australian Institute of Marine Science, Townsville, Australia
Ecological processes on nearshore coral communities of the Great Barrier Reef (GBR)
are affected by agricultural and urban runoff. Elevated nutrient and sediment levels in
runoff have detrimental impacts on many aspects of coral reproduction and may reduce
the ability of nearshore coral communities to recover from other disturbances and hence,
their resilience. Few studies have documented recruitment rates in nearshore waters of
the GBR and it is unclear how recruitment varies across gradients of water quality and
how the surrounding coral community influences spatial and temporal patterns in coral
recruitment. As a part of a long-term marine monitoring program under the GBR Water
Quality Protection Plan, hard coral recruitment has been monitored for three years (2005,
2006 and 2007). Terracotta settlement tiles were deployed on fringing reefs located along
an assumed water quality gradient within each of four inshore regions, to examine the
influence of water quality, larval supply and surrounding benthos on the recruitment
success of corals. Numbers of hard coral recruits in this study were up to 10 times higher
than previously recorded at the same locations, highlighting the large temporal variability
of recruitment on GBR nearshore reefs. The influence of water quality on recruitment
was variable, but recruitment did not generally increase with increasing distance away
from the coast, where turbidity levels and nutrient availability are usually elevated.
Characteristics of the surrounding adult hard coral communities, such as the taxonomic
composition and the reproductive health (e.g., influenced by disturbance such as
bleaching or mechanical damage in the previous year), also played an important role in
determining both the quantity of recruits and their taxonomic composition. Sustained
local larval supply is vital for the recovery of inshore coral communities from
disturbances, and, conversely, large-scale disturbance such as coral bleaching have longlasting
negative effects on these communities.
10-6
Complex Life Histories, Dynamic Populations And Multiple Disturbances: Can A
Demographic Approach To Monitoring Help Conserve Coral Reefs?
James GILMOUR* 1
1 Australian Institute of Marine Science, Perth, WA, Australia
Global decreases in coral cover resulting from an increasing combination of disturbances
are directly related to changes in the rates of transition of life history stages of corals
through their life cycle. Quantifying these transition rates for populations (vital rates)
therefore provides a way to investigate the past and future consequences of disturbance
regimes. However, disturbance regimes affect species and their life history stages
differently. The quantification of vital rates in three studies provided evidence of the
extent to which the contribution of stage transitions to population growth, and their
variability following population decrease, depended on the coral and the disturbance
regime. For example, in populations of a fungiid coral exposed to chronic disturbances,
survival varied dramatically between sexual and asexual recruits of similar size, whereas
survival varied little across all size classes in populations of Acropora free of chronic
disturbances. Further, the relative importance of sexual recruits or other stages to
population maintenance varied along a gradient of water quality in populations of
Acropora, and for populations of fungiid coral according to whether disturbances were in
the form of periodic cyclones or cyclones and chronic sedimentation. In these
populations, demographic and temporal variability had implications for the application of
their vital rates to projection models. In particular, changes in stage transitions were not
independent, so that substituting transition values with those observed in other
populations, time-steps, or experimental manipulations, further reduced the accuracy of
projections aimed at simulating disturbance regimes. Nevertheless, the quantification of
population vital rates and their application to simple matrix models was an effective
means of understanding and summarising the impacts of complex regimes of disturbance,
and the projection of population structure under a variety of hypothetical scenarios a
useful means of illustrating the future consequences of not mitigating certain stressors.
10-7
How Settlement Dynamics Determine The Abundance And Distribution Of Corals
Mark VERMEIJ* 1 , Stuart SANDIN 2
1 Botany Department, University of Hawaii, Lahaina, HI, 2 Center for Marine Biodiversity and
Conservation, Scripps Institution of Oceanography, La Jolla, CA
Studying the earliest life-stages of corals (i.e. settled planulae and recently metamorphosed
polyps) is problematic due to their small size and cryptic behavior and therefore limited
information exists on the earliest demographics of corals. Here we present a combination of
field and laboratory studies from the Caribbean and Hawaii aimed at revealing the factors that
determine settler abundance and subsequent settlement success. Local densities of
heterospecifics (algae and microbes) and conspecifics have profound effects on rates of
settlement and early post-settlement survivorship. The early benthic phase of corals represents a
severe demographic bottleneck whereby >80% of the initial number of settlers will not survive
for more than one year. During this period, density-dependent and density-independent effects
of microbes and benthic algae have profound effects on settler survivorship laying a foundation
for their future distribution. The effects of algae and microbes can be positive or negative and
depended on a settler’s developmental stage. Increasing adult cover causes higher local
settlement rates but only when total cover is low (