Click
here to close Hello! We notice that
you are using Internet Explorer, which is not supported by Echinobase
and may cause the site to display incorrectly. We suggest using a
current version of Chrome,
FireFox,
or Safari.
The ecological importance of habitat complexity to the Caribbean coral reef herbivore Diadema antillarum: three lines of evidence.
Bodmer MDV
,
Wheeler PM
,
Anand P
,
Cameron SE
,
Hintikka S
,
Cai W
,
Borcsok AO
,
Exton DA
.
???displayArticle.abstract???
When Caribbean long-spined sea urchins, Diadema antillarum, are stable at high population densities, their grazing facilitates scleractinian coral dominance. Today, populations remain suppressed after a mass mortality in 1983-1984 caused a loss of their ecosystem functions, and led to widespread declines in ecosystem health. This study provides three lines of evidence to support the assertion that a lack of habitat complexity on Caribbean coral reefs contributes to their recovery failure. Firstly, we extracted fractal dimension (D) measurements, used as a proxy for habitat complexity, from 3D models to demonstrate that urchins preferentially inhabit areas of above average complexity at ecologically relevant spatial scales. Secondly, controlled behaviour experiments showed that an energetically expensive predator avoidance behaviour is reduced by 52% in complex habitats, potentially enabling increased resource allocation to reproduction. Thirdly, we deployed a network of simple and cost-effective artificial structures on a heavily degraded reef system in Honduras. Over a 24-month period the adult D. antillarum population around the artificial reefs increased by 320% from 0.05 ± 0.01 to 0.21 ± 0.04 m-2 and the juvenile D. antillarum population increased by 750% from 0.08 ± 0.02 to 0.68 ± 0.07 m-2. This study emphasises the important role of habitat structure in the ecology of D. antillarum and as a barrier to its widespread recovery.
Figure 1. Panel photograph showing tank setup for different complexity treatments. Top left natural-material-low-complexity, top right = artificial-material-low-complexity, bottom left = natural-material-high-complexity, bottom right = artificial-material-high-complexity.
Figure 2. Three-dimensional images showing complexity differences between: (A) a 2 m × 2 m area of reef without urchins on Utila, (B) a 2 m × 2 m area of reef with urchins on Utila, (C) a 2 m × 2 m area of control reef in La Ensenada, (D) an artificial reef deployed at La Ensenada. D(5–15 cm) = fractal dimension of the model at the 5–15 cm spatial resolution. Mean ± 1SE is reported for (A)–(C), but all artificial reefs are identical therefore variation in fractal dimension for (D) is not reported.
Figure 3. Distribution of adult D. antillarum test diameters on the reefs of Utila (yellow; n = 139) and Tela (blue; n = 100). Dotted vertical line is the mean of all individuals from both locations.
Figure 4. Complexity signatures of reef areas devoid of D. antillarum (orange, n = 35), and areas inhabited by D. antillarum (blue, n = 5). Data shown in the main panel are mean ± 1SE fractal dimension (D), a measure of structural complexity within defined spatial resolutions, shown at: 1–5 cm, 5–15 cm, 15–30 cm, 30–60 cm and 60–120 cm, with 5–15 cm representing the size range of ecological significance to D. antillarum as predation refugia. D ranges from 2 to 3 and higher values are associated with greater structural complexity. Error bars represent ± 1SE from the mean.
Figure 5. Impacts of habitat complexity on the predator avoidance behaviour (PAB) of D. antillarum. Flat treatments were carried out in trial tanks without any structure, low complexity treatments with natural material occurred in tanks enriched with fragments of reef rubble, and low complexity treatments with artificial materials were conducted in tanks with fragmented breezeblocks. High complexity treatments with natural material used reef rubble to simulate a reef crevice, and during high complexity treatments with artificial material individuals were provided with a whole breezeblock. The study was fully factorial and n = 10 for each treatment. The bold horizontal line on each boxplot represents the mean, the box itself shows the interquartile range and the whiskers delimit the full range of the data. Letters above the plots show the result of a post hoc Tukey–Kramer analysis and show where significant differences between treatments occur.
Figure 6. Temporal changes in the density of adult and juvenile D. antillarum on small artificial reef structures and nearby control reefs. Data were collected at the same time each year, but points are jittered to aid visualisation. Data shown are mean ± SE.
Alvarez-Filip,
Flattening of Caribbean coral reefs: region-wide declines in architectural complexity.
2009, Pubmed,
Echinobase
Alvarez-Filip,
Flattening of Caribbean coral reefs: region-wide declines in architectural complexity.
2009,
Pubmed
,
Echinobase
Andradi-Brown,
Reef Fish Community Biomass and Trophic Structure Changes across Shallow to Upper-Mesophotic Reefs in the Mesoamerican Barrier Reef, Caribbean.
2016,
Pubmed
Bellwood,
Confronting the coral reef crisis.
2004,
Pubmed
Bruno,
Assessing evidence of phase shifts from coral to macroalgal dominance on coral reefs.
2009,
Pubmed
Carpenter,
One-third of reef-building corals face elevated extinction risk from climate change and local impacts.
2008,
Pubmed
Edmunds,
Recovery of Diadema antillarum reduces macroalgal cover and increases abundance of juvenile corals on a Caribbean reef.
2001,
Pubmed
,
Echinobase
Exton,
Artisanal fish fences pose broad and unexpected threats to the tropical coastal seascape.
2019,
Pubmed
Gardner,
Long-term region-wide declines in Caribbean corals.
2003,
Pubmed
Graham,
Predicting climate-driven regime shifts versus rebound potential in coral reefs.
2015,
Pubmed
Hughes,
Coral reefs in the Anthropocene.
2017,
Pubmed
Hughes,
Rising to the challenge of sustaining coral reef resilience.
2010,
Pubmed
Hunt,
Aggregating behaviour in invasive Caribbean lionfish is driven by habitat complexity.
2019,
Pubmed
Lessios,
The Great Diadema antillarum Die-Off: 30 Years Later.
2016,
Pubmed
,
Echinobase
Lessios,
Spread of diadema mass mortality through the Caribbean.
1984,
Pubmed
,
Echinobase
Levitan,
Influence of Body Size and Population Density on Fertilization Success and Reproductive Output in a Free-Spawning Invertebrate.
1991,
Pubmed
,
Echinobase
Levitan,
What makes a species common? No evidence of density-dependent recruitment or mortality of the sea urchin Diadema antillarum after the 1983-1984 mass mortality.
2014,
Pubmed
,
Echinobase
McCann,
The diversity-stability debate.
2000,
Pubmed
Mumby,
Thresholds and the resilience of Caribbean coral reefs.
2007,
Pubmed
,
Echinobase
Noriega,
[Abundance of Diadema antillarum (Echinodermata: Echinoidea) in the coasts of Venezuela].
2006,
Pubmed
,
Echinobase
Pandolfi,
Global trajectories of the long-term decline of coral reef ecosystems.
2003,
Pubmed
Pennington,
THE ECOLOGY OF FERTILIZATION OF ECHINOID EGGS: THE CONSEQUENCES OF SPERM DILUTION, ADULT AGGREGATION, AND SYNCHRONOUS SPAWNING.
1985,
Pubmed
,
Echinobase
Raible,
Opsins and clusters of sensory G-protein-coupled receptors in the sea urchin genome.
2006,
Pubmed
,
Echinobase
Roff,
Global disparity in the resilience of coral reefs.
2012,
Pubmed
Ullrich-Lüter,
C-opsin expressing photoreceptors in echinoderms.
2013,
Pubmed
,
Echinobase
Young,
Cost and time-effective method for multi-scale measures of rugosity, fractal dimension, and vector dispersion from coral reef 3D models.
2017,
Pubmed