11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10-29
Coral Reef Assemblages and Diversity in the Volcanic Northern Mariana Islands
Peter HOUK* 1 , John STARMER 1
1 CNMI Marine Monitoring Program, Saipan, Northern Mariana Islands
The volcanic Northern Mariana Islands (NMI) provide a unique opportunity to examine
patterns in coral-reef assemblages, diversity, and reef growth due to varying island size,
volcanic activity, and environmental regime. Initially, this study explores why patchy,
inconsistent reef growth is evident throughout the archipelago by examining if there are
linkages between ‘reef types’ and the modern assemblages growing upon them. The ‘reef
types’ examined were: 1) volcanic boulders, 2) colonized boulders, 3) low-slope
Holocene and sand, 4) complex, colonized Holocene, 5) complex, uncolonized Holocene,
and 6) high-slope, sheltered Holocene. Replicated, quadrat-based surveys were
conducted at 41 sites to gather coral colony size and taxon occurrence data. The initial
results showed that ‘reef type’ acts as a good predictor of modern coral assemblages,
however, taxon occurrence data showed less affiliation with ‘reef type’, rather an ‘island
effect’ emerged. Most islands supported distinct populations of algae and invertebrate
species. Building from this base, regressions between island size, volcanic disturbance,
salinity, and species richness are interpreted to approach existing theories that explain
diversity patterns. Notably, island size had a positive, log-log relationship with species
richness across many phyla, including corals. The differing z-values, or rates of increase,
suggest different levels of connectivity may exist between the local and regional
populations for different phyla. Deviations from the expected species-area relationship
for corals (e.g. residuals) were positively related to the number of years since volcanic
activity has occurred. At a minimum, the presence of a favorable foundation is required
for sustained coral growth, while coral populations and reef diversity rise on large islands
that are less influenced by freshwater and volcanic disturbances. For the NMI
specifically, the results provide a desirable context for developing management strategies
to maintain and enhance the biological integrity of these remote islands.
10-30
The Rise And Fall Of A Coral Reef Ascidian
Noa SHENKAR* 1 , Omri BRONSTEIN 2 , Yossi LOYA 1
1 Zoology Department, Tel Aviv University, Tel Aviv, Israel, 2 Tel Aviv University, Tel
Aviv, Israel
Although ascidians constitute a minor benthic component on exposed surfaces on natural
coral reefs they play an important role in the carbon and nutrients cycles in coral reef
ecosystems. Eutrophication of these ecosystems may result in vast changes in the
densities and distribution of colonial ascidians and their interaction with benthic biota. In
the coral reefs of Eilat, a new colonial ascidian, Botryllus eilatensis, has been observed
rapidly colonizing artificial substrates and overgrowing dead coral skeletons. Monthly
monitoring of 50 - 70 tagged coral colonies interacting with B. eilatensis was conducted
in order to study overgrowth dynamics and the relationship between coral morphology,
size, and orientation and ascidian overgrowth. Results show that the rate of B. eilatensis
overgrowth was influenced by the coral's morphology and orientation combined with a
seasonal appearance of the ascidian. During spring (April - June) the average ascidian
cover percentage was 27 ± 4.6 %; decreasing rapidly during summer months. This
seasonality is linked to the vertical mixing phenomenon that occurs in Eilat every winter.
This was corroborated when B. eilatensis fragments translocated to a nutrient rich site
were observed to increase three fold in size and exhibited higher survivorship rates in
comparison to the intact fragments remained in a reference site. Increased anthropogenic
activity, particularly the eutrophication occurring along the Israeli coasts, creates
favorable conditions for filter-feeding organisms such as ascidians, providing them with
an advantage in competition for space with reef-building corals and other organisms.
10-31
Population Dynamics Of The Corkscrew Anemone Bartholomea Annulata On Caribbean
Coral Reefs: Implications For Anemoneshrimp Symbionts And Fish Cleaning Stations
Michael NELSEN* 1 , Stephen RATCHFORD 2 , Nanette E. CHADWICK 1
1 Auburn University, Auburn, AL, 2 University of the Virgin Islands, St. Thomas, Virgin Islands
(U.S.)
Large sea anemones are conspicuous components of coral reef communities, yet little is known
concerning their population dynamics. On Caribbean coral reefs, the corkscrew anemone
Bartholomea annulata hosts an assemblage of obligate shrimp symbionts, some of which are
important cleaners of parasites from large reef fish. Thus, the stability and recovery from
disturbance of anemone host populations may impact the coral reef community at several
trophic levels. During 2006-2008, we monitored the dynamics of populations of B. annulata at 2
coral reef sites near St. Thomas, US Virgin Islands. The abundance and body size of individuals
both were significantly higher at an inshore than an offshore reef site. At both sites, recruitment
was rapid and populations were extremely dynamic. Rates of growth and mortality decreased
with body size; small individuals tended to either grow rapidly or die, while large individuals
either shrank or did not change in size, and rarely died. Some individuals in all size classes
reproduced asexually to produce small buds (clonal replicates), resulting in a rapid potential
expansion of populations. We applied matrix modeling and sensitivity analyses to determine
which life stage most impacted change in these populations. Based on these demographic
characteristics, we also provide recommendations for the support of a sustainable fishery on
these anemones, which are heavily collected for the ornamental aquarium trade. We conclude
that rapid population turnover in this sea anemone leads to radiating effects on the stability of
obligate anemoneshrimps and the location of fish cleaning stations on Caribbean reefs.
10-32
What Is The Future Of The Threatened acropora Palmata? Population Projections And
Management Recommendations
Tali VARDI* 1 , Dana E. WILLIAMS 2,3 , K. Lindsey KRAMER 4
1 Scripps Institution of Oceanography, La Jolla, CA, 2 Cooperative Institute for Marine and
Atmospheric Studies, University of Miami RSMAS, Miami, FL, 3 Southeast Fisheries Science
Center, NOAA Fisheries, Miami, 4 Pacific Island Network Inventory and Monitoring Program,
National Park Service, Kailua-Kona, HI
Acropora palmata was once the dominant hermatypic coral in shallow reef environments
throughout the Caribbean, Florida, and Bahamas. Since the 1980s it has suffered a 97% decline
in abundance throughout its range and was included on the US Endangered Species List in
2006. Despite the dramatic nature of this decline, and the loss of habitat that would be caused
by an extinction, neither abundance nor rates of decline have been documented systematically
throughout the Caribbean. In Autumn 2007, abundance of Acropora palmata was estimated in
Florida, Puerto Rico, Jamaica, Virgin Gorda, and Curaçao. Abundance in Florida was
dramatically lower than in other sites. The scarcity of Acropora palmata in Florida is explained
by increased hurricanes and disease, problems that are difficult to manage. To explore
population changes in more detail and to help identify life history stages most affected, a sizebased
population model was developed. Based on Acropora palmata’s population trajectory
since 2004, as measured by a standardized, size-based demographic monitoring protocol in the
Florida Keys, the local population will reach a stable distribution in 20 years. At that time, the
current population structure, in which 35% are pre-reproductive and 45% are reproductive, will
have become dominated by pre-reproductive individuals and only 20% of colonies will
reproduce sexually. This loss of large individuals would also reduce the number of asexually
derived fragments, leading to an overall decrease in abundance of colonies in Florida. Parallel
data from the island of Curaçao from 2006-7, show both a greater overall abundance of
Acropora palmata and no significant change in the relative abundance of larger individuals.
Significant changes in size distribution can warn of impending phase shifts. These results
suggest that determining and eliminating the causes of mortality in large adults are key
conservation priorities for Florida reefs.
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