scholarly journals Among-site variability in the stochastic dynamics of East African coral reefs

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3290 ◽  
Author(s):  
Katherine A. Allen ◽  
John F. Bruno ◽  
Fiona Chong ◽  
Damian Clancy ◽  
Tim R. McClanahan ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Stochastic Dynamics ◽  
Coral Cover ◽  
Abiotic Factors ◽  
Regional Scale ◽  
East African ◽  
Vector Autoregressive ◽  
High Conservation ◽  
Site Variability

Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation efforts. Using a 22-year time series of benthic composition data from 20 reefs on the Kenyan and Tanzanian coast, we developed Bayesian vector autoregressive state-space models for reef dynamics, incorporating among-site variability, and quantified their long-term behaviour. We estimated that if there were no among-site variability, the total long-term variability would be approximately one-third of its current value. Thus, our results showed that among-site variability contributes more to long-term variability in reef composition than does temporal variability. Individual sites were more predictable than previously thought, and predictions based on current snapshots are informative about long-term properties. Our approach allowed us to identify a subset of possible climate refugia sites with high conservation value, where the long-term probability of coral cover ≤0.1 (as a proportion of benthic cover of hard substrate) was very low. Analytical results show that this probability is most strongly influenced by among-site variability and by interactions among benthic components within sites. These findings suggest that conservation initiatives might be successful at the site scale as well as the regional scale.

scholarly journals Among-site variability in the stochastic dynamics of East African coral reefs

2017 ◽  
Author(s):  
Katherine A Allen ◽  
John F Bruno ◽  
Fiona Chong ◽  
Damian Clancy ◽  
Tim R McClanahan ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Stochastic Dynamics ◽  
Coral Cover ◽  
Abiotic Factors ◽  
Regional Scale ◽  
East African ◽  
Vector Autoregressive ◽  
High Conservation ◽  
Site Variability

Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation efforts. Using a 22-year time series of benthic composition data from 20 reefs on the Kenyan and Tanzanian coast, we developed Bayesian vector autoregressive state-space models for reef dynamics, incorporating among-site variability, and quantified their long-term behaviour. We estimated that if there were no among-site variability, the total long-term variability would be approximately one third of its current value. Thus, our results showed that among-site variability contributes more to long-term variability in reef composition than does temporal variability. Individual sites were more predictable than previously thought, and predictions based on current snapshots are informative about long-term properties. Our approach allowed us to identify a subset of possible climate refugia sites with high conservation value, where the long-term probability of coral cover \(\leq\) 0.1 was very low. Analytical results show that this probability is most strongly influenced by among-site variability and by interactions among benthic components within sites. These findings suggest that conservation initiatives might be successful at the site scale as well as the regional scale.

scholarly journals Among-site variability in the stochastic dynamics of East African coral reefs

2017 ◽  
Author(s):  
Katherine A Allen ◽  
John F Bruno ◽  
Fiona Chong ◽  
Damian Clancy ◽  
Tim R McClanahan ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Stochastic Dynamics ◽  
Coral Cover ◽  
Abiotic Factors ◽  
Regional Scale ◽  
East African ◽  
Vector Autoregressive ◽  
High Conservation ◽  
Site Variability

Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation efforts. Using a 22-year time series of benthic composition data from 20 reefs on the Kenyan and Tanzanian coast, we developed Bayesian vector autoregressive state-space models for reef dynamics, incorporating among-site variability, and quantified their long-term behaviour. We estimated that if there were no among-site variability, the total long-term variability would be approximately one third of its current value. Thus, our results showed that among-site variability contributes more to long-term variability in reef composition than does temporal variability. Individual sites were more predictable than previously thought, and predictions based on current snapshots are informative about long-term properties. Our approach allowed us to identify a subset of possible climate refugia sites with high conservation value, where the long-term probability of coral cover \(\leq\) 0.1 was very low. Analytical results show that this probability is most strongly influenced by among-site variability and by interactions among benthic components within sites. These findings suggest that conservation initiatives might be successful at the site scale as well as the regional scale.

scholarly journals NON-RANDOM TIMING OF ECOLOGICAL SHIFTS ON CARIBBEAN CORAL REEFS SUGGESTS REGIONAL CAUSES OF CHANGE

2019 ◽  
Author(s):  
William F. Precht ◽  
Richard B. Aronson ◽  
Toby A. Gardner ◽  
Jennifer A. Gill ◽  
Julie P. Hawkins ◽  
...  
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Nutrient Loading ◽  
Coral Cover ◽  
Coral Disease ◽  
Regional Scale ◽  
Negative Relationship ◽  
Grazing Pressure ◽  
Coral Mortality ◽  
Macroalgal Cover

AbstractCaribbean reefs have experienced unprecedented changes in the past four decades. Of great concern is the perceived widespread shift from coral to macroalgal dominance and the question of whether it represents a new, stable equilibrium for coral-reef communities. The primary causes of the shift -- grazing pressure (top-down), nutrient loading (bottom-up) or direct coral mortality (side-in) -- still remain somewhat controversial in the coral reef literature. We have attempted to tease out the relative importance of each of these causes. Four insights emerge from our analysis of an early regional dataset of information on the benthic composition of Caribbean reefs spanning the years 1977–2001. First, although three-quarters of reef sites have experienced coral declines concomitant with macroalgal increases, fewer than 10% of the more than 200 sites studied were dominated by macroalgae in 2001, by even the most conservative definition of dominance. Using relative dominance as the threshold, a total of 49 coral-to-macroalgae shifts were detected. This total represents ∼35% of all sites that were dominated by coral at the start of their monitoring periods. Four shifts (8.2%) occurred because of coral loss with no change in macroalgal cover, 15 (30.6%) occurred because of macroalgal gain without coral loss, and 30 (61.2%) occurred owing to concomitant coral decline and macroalgal increase. Second, the timing of shifts at the regional scale is most consistent with the side-in model of reef degradation, which invokes coral mortality as a precursor to macroalgal takeover, because more shifts occurred after regional coral-mortality events than expected by chance. Third, instantaneous observations taken at the start and end of the time-series for individual sites showed these reefs existed along a continuum of coral and macroalgal cover. The continuous, broadly negative relationship between coral and macroalgal cover suggests that in some cases coral-to-macroalgae phase shifts may be reversed by removing sources of perturbation or restoring critical components such as the herbivorous sea urchin Diadema antillarum to the system. The five instances in which macroalgal dominance was reversed corroborate the conclusion that macroalgal dominance is not a stable, alternative community state as has been commonly assumed. Fourth, the fact that the loss in regional coral cover and concomitant changes to the benthic community are related to punctuated, discrete events with known causes (i.e. coral disease and bleaching), lends credence to the hypothesis that coral reefs of the Caribbean have been under assault from climate-change-related maladies since the 1970s.

scholarly journals U-Th dating reveals regional-scale decline of branching Acropora corals on the Great Barrier Reef over the past century

2017 ◽  
Vol 114 (39) ◽  
pp. 10350-10355 ◽  
Author(s):  
Tara R. Clark ◽  
George Roff ◽  
Jian-xin Zhao ◽  
Yue-xing Feng ◽  
Terence J. Done ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Coral Cover ◽  
Regional Scale ◽  
Coral Community ◽  
Past Century ◽  
Barrier Reef ◽  
The Past ◽  
Hard Coral Cover ◽  
Term Monitoring

Hard coral cover on the Great Barrier Reef (GBR) is on a trajectory of decline. However, little is known about past coral mortality before the advent of long-term monitoring (circa 1980s). Using paleoecological analysis and high-precision uranium-thorium (U-Th) dating, we reveal an extensive loss of branching Acropora corals and changes in coral community structure in the Palm Islands region of the central GBR over the past century. In 2008, dead coral assemblages were dominated by large, branching Acropora and living coral assemblages by genera typically found in turbid inshore environments. The timing of Acropora mortality was found to be occasionally synchronous among reefs and frequently linked to discrete disturbance events, occurring in the 1920s to 1960s and again in the 1980s to 1990s. Surveys conducted in 2014 revealed low Acropora cover (<5%) across all sites, with very little evidence of change for up to 60 y at some sites. Collectively, our results suggest a loss of resilience of this formerly dominant key framework builder at a regional scale, with recovery severely lagging behind predictions. Our study implies that the management of these reefs may be predicated on a shifted baseline.

scholarly journals Correlation between Coral Reef Condition and the Diversity and Abundance of Fishes and Sea Urchins on an East African Coral Reef

Oceans ◽  
2022 ◽  
Vol 3 (1) ◽  
pp. 1-14
Author(s):  
Pia Ditzel ◽  
Sebastian König ◽  
Peter Musembi ◽  
Marcell K. Peters
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Sea Urchins ◽  
Coral Cover ◽  
Fish Diversity ◽  
East African ◽  
Fish Family ◽  
The Relationship ◽  
Gazi Bay ◽  
Reef Condition

Coral reefs are one of the most diverse marine ecosystems, providing numerous ecosystem services. This present study investigated the relationship between coral reef condition and the diversity and abundance of fishes, on a heavily fished East African coral reef at Gazi Bay, Kenya. Underwater visual censuses were conducted on thirty 50 × 5 m belt transects to assess the abundance and diversity of fishes. In parallel, a 25-m length of each of the same transects was recorded with photo-quadrats to assess coral community structure and benthic characteristics. For statistical analyses, multi-model inference based on the Akaike Information Criterion was used to evaluate the support for potential predictor variables of coral reef and fish diversity. We found that coral genus richness was negatively correlated with the abundance of macroalgae, whereas coral cover was positively correlated with both the abundance of herbivorous invertebrates (sea urchins) and with fish family richness. Similarly, fish family richness appeared mainly correlated with coral cover and invertebrate abundance, although no correlates of fish abundance could be identified. Coral and fish diversity were very low, but it appears that, contrary to some locations on the same coast, sea urchin abundance was not high enough to be having a negative influence on coral and fish assemblages. Due to increasing threats to coral reefs, it is important to understand the relationship among the components of the coral reef ecosystem on overfished reefs such as that at Gazi Bay.

Sign in / Sign up

Export Citation Format

Share Document