Quantifying scales of spatial variability in algal turf assemblages on coral reefs

Active remote sensing technology represented by multi-beam and lidar provides an important approach for the effective acquisition of underwater coral reef geomorphological information. A spatially continuous surface model of coral reef geomorphology reconstructed from active remote sensing datasets can provide important geomorphological parameters for the research of coral reef geomorphological and ecological changes. However, the surface modeling methods commonly used in previous studies, such as ordinary kriging (OK) and natural neighborhood (NN), often represent a “smoothing effect”, which causes the strong spatial variability of coral reefs to be imprecisely reflected by the reconstructed surfaces, thus affecting the accurate calculation of subsequent geomorphological parameters. In this study, a spatial variability modified OK (OK-SVM) method is proposed to reduce the impact of the “smoothing effect” on the high-precision reconstruction of the complex geomorphology of coral reefs. The OK-SVM adopts a collaborative strategy of global parameter transformation, local residual correction, and extremum correction to modify the spatial variability of the reconstructed model, while maintaining high local accuracy. The experimental results show that the OK-SVM has strong robustness to spatial variability modification. This method was applied to the geomorphological reconstruction of the northern area of a coral atoll in the Nansha Islands, South China Sea, and the performance was compared with that of OK and NN. The results show that OK-SVM has higher numerical accuracy and attribute accuracy in detailed morphological fidelity, and is more adaptable in the geomorphological reconstruction of coral reefs with strong spatial variability. This method is relatively reliable for achieving high-precision reconstruction of complex geomorphology of coral reefs from active remote sensing datasets, and has potential to be extended to other geomorphological reconstruction applications.

Download Full-text

Coral species composition drives key ecosystem function on coral reefs

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2019.2214 ◽

2020 ◽

Vol 287 (1921) ◽

pp. 20192214 ◽

Cited By ~ 3

Author(s):

Laura E. Richardson ◽

Nicholas A. J. Graham ◽

Andrew S. Hoey

Keyword(s):

Coral Reefs ◽

Species Composition ◽

Coral Species ◽

Fish Assemblages ◽

Reef Fishes ◽

Ecosystem Functions ◽

Algal Turf ◽

Benthic Assemblages ◽

Ecosystem Recovery ◽

Visual Occlusion

Rapid and unprecedented ecological change threatens the functioning and stability of ecosystems. On coral reefs, global climate change and local stressors are reducing and reorganizing habitat-forming corals and associated species, with largely unknown implications for critical ecosystem functions such as herbivory. Herbivory mediates coral–algal competition, thereby facilitating ecosystem recovery following disturbance such as coral bleaching events or large storms. However, relationships between coral species composition, the distribution of herbivorous fishes and the delivery of their functional impact are not well understood. Here, we investigate how herbivorous fish assemblages and delivery of two distinct herbivory processes, grazing and browsing, differ among three taxonomically distinct, replicated coral habitats. While grazing on algal turf assemblages was insensitive to different coral configurations, browsing on the macroalga Laurencia cf. obtusa varied considerably among habitats, suggesting that different mechanisms may shape these processes. Variation in browsing among habitats was best predicted by the composition and structural complexity of benthic assemblages (in particular the cover and composition of corals, but not macroalgal cover), and was poorly reflected by visual estimates of browser biomass. Surprisingly, the lowest browsing rates were recorded in the most structurally complex habitat, with the greatest cover of coral (branching Porites habitat). While the mechanism for the variation in browsing is not clear, it may be related to scale-dependent effects of habitat structure on visual occlusion inhibiting foraging activity by browsing fishes, or the relative availability of alternate dietary resources. Our results suggest that maintained functionality may vary among distinct and emerging coral reef configurations due to ecological interactions between reef fishes and their environment determining habitat selection.

Download Full-text

Transformation of algal turf by echinoids and scarid fishes on French Polynesian coral reefs

Coral Reefs ◽

10.1007/bf00291934 ◽

1992 ◽

Vol 11 (1) ◽

pp. 45-50 ◽

Cited By ~ 10

Author(s):

Mireille L. Harmelin-Vivien ◽

Mireille Peyrot-Clausade ◽

Jean-Claude Romano

Keyword(s):

Coral Reefs ◽

Algal Turf

Download Full-text

Algal turf productivity on coral reefs: A meta-analysis

Marine Environmental Research ◽

10.1016/j.marenvres.2021.105311 ◽

2021 ◽

Vol 168 ◽

pp. 105311

Author(s):

Sterling B. Tebbett ◽

David R. Bellwood

Keyword(s):

Coral Reefs ◽

Meta Analysis ◽

Algal Turf

Download Full-text

Temporal and spatial variability in coral recruitment on two Indonesian coral reefs: consistently lower recruitment to a degraded reef

Marine Biology ◽

10.1007/s00227-012-2066-7 ◽

2012 ◽

Vol 160 (1) ◽

pp. 97-105 ◽

Cited By ~ 19

Author(s):

P. Salinas-de-León ◽

C. Dryden ◽

D. J. Smith ◽

J. J. Bell

Keyword(s):

Coral Reefs ◽

Spatial Variability ◽

Coral Recruitment ◽

Temporal And Spatial Variability ◽

Temporal And Spatial

Download Full-text

Acropora abundance and size in the Maldives six years after the 1998 mass mortality: patterns across reef typologies and depths

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315410000020 ◽

2010 ◽

Vol 90 (5) ◽

pp. 919-922 ◽

Cited By ~ 17

Author(s):

Roberta Lasagna ◽

Giancarlo Albertelli ◽

Carla Morri ◽

Carlo Nike Bianchi

Keyword(s):

Coral Reefs ◽

Spatial Variability ◽

Shallow Water ◽

Growth Rates ◽

Mass Mortality ◽

Sea Surface ◽

Extension Rate ◽

Reef Corals ◽

Mass Mortality Event ◽

Mean Size

In 1998, in coincidence with high sea surface temperatures, Maldivian reef corals were severely affected by mass mortality following bleaching. Tabular Acropora corals, formerly abundant in shallow water, were nearly exterminated. Recovery started soon, and in 2004 Maldivian reefs appeared rich in tabular Acropora colonies again, especially at some sites. This study aimed at determining the degree of spatial variability of tabular Acropora abundance and size among reef typologies (ocean versus lagoon reefs) and depth zones (4–6, 10–12 and 16–18 m) 6 years after the mass mortality event. A total of 192 tabular Acropora colonies (Ø > 16 cm) were counted and measured in six sites. Their abundance differed between reef typologies and according to depth zones, with the highest values in deep lagoon reefs. Colony mean size differed only among depth zones, the largest colonies (up to 105 cm) being found in shallow reefs. Assuming a radial extension rate of 10 cm · yr−1, colonies larger than 65 cm can be interpreted as the survivors of the mass mortality of 1998; conversely, they may represent the result of enhanced growth rates in uncrowded situations as those characterizing the coral reefs of the Maldives in 2004.

Download Full-text