Crustose coralline algae increased framework and diversity on ancient coral reefs

Quantifying the three-dimensional (3D) habitat structure of coral reefs is an important aspect of coral reef monitoring, as habitat architecture affects the abundance and diversity of reef organisms. Here, we used photogrammetric techniques to generate 3D reconstructions of coral reefs and examined relationships between benthic cover and various habitat metrics obtained at six different resolutions of raster cells, ranging from 1 to 32 cm. For metrics of 3D structural complexity, fractal dimension, which utilizes information on 3D surface areas obtained at different resolutions, and vector ruggedness measure (VRM) obtained at 1-, 2- or 4-cm resolution correlated well with benthic cover, with a relatively large amount of variability in these metrics being explained by the proportions of corals and crustose coralline algae. Curvature measures were, on the other hand, correlated with branching and mounding coral cover when obtained at 1-cm resolution, but the amount of variability explained by benthic cover was generally very low when obtained at all other resolutions. These results show that either fractal dimension or VRM obtained at 1-, 2- or 4-cm resolution, along with curvature obtained at 1-cm resolution, can effectively capture the 3D habitat structure provided by specific benthic organisms.

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The hidden army: corallivorous crown-of-thorns seastars can spend years as herbivorous juveniles

Biology Letters ◽

10.1098/rsbl.2019.0849 ◽

2020 ◽

Vol 16 (4) ◽

pp. 20190849 ◽

Cited By ~ 7

Author(s):

Dione J. Deaker ◽

Antonio Agüera ◽

Huang-An Lin ◽

Corinne Lawson ◽

Claire Budden ◽

...

Keyword(s):

Coral Reefs ◽

Exponential Growth ◽

Black Box ◽

Coralline Algae ◽

Crustose Coralline Algae ◽

Major Threat ◽

Asymptotic Size ◽

The Impact

Crown-of-thorns seastar (COTS) outbreaks are a major threat to coral reefs. Although the herbivorous juveniles and their switch to corallivory are key to seeding outbreaks, they remain a black box in our understanding of COTS. We investigated the impact of a delay in diet transition due to coral scarcity in cohorts reared on crustose coralline algae for 10 months and 6.5 years before being offered coral. Both cohorts achieved an asymptotic size (16–18 mm diameter) on algae and had similar exponential growth on coral. After 6.5 years of herbivory, COTS were competent coral predators. This trophic and growth plasticity results in a marked age–size disconnect adding unappreciated complexity to COTS boom–bust dynamics. The potential that herbivorous juveniles accumulate in the reef infrastructure to seed outbreaks when favourable conditions arise has implications for management of COTS populations.

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CRUSTOSE CORALLINE ALGAE INCREASE FRAMEWORK AND DIVERSITY ON ANCIENT CORAL REEFS

10.1130/abs/2016am-281530 ◽

2016 ◽

Author(s):

Anna M. Weiss ◽

◽

Rowan Martindale

Keyword(s):

Coral Reefs ◽

Coralline Algae ◽

Crustose Coralline Algae

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Low recruitment due to altered settlement substrata as primary constraint for coral communities under ocean acidification

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.1536 ◽

2017 ◽

Vol 284 (1862) ◽

pp. 20171536 ◽

Cited By ~ 21

Author(s):

Katharina E. Fabricius ◽

Sam H. C. Noonan ◽

David Abrego ◽

Lindsay Harrington ◽

Glenn De'ath

Keyword(s):

Coral Reefs ◽

Ocean Acidification ◽

Field Experiments ◽

Later Life ◽

Coralline Algae ◽

Life Stages ◽

Crustose Coralline Algae ◽

Coral Recruitment ◽

Recovery Potential ◽

Coral Communities

The future of coral reefs under increasing CO 2 depends on their capacity to recover from disturbances. To predict the recovery potential of coral communities that are fully acclimatized to elevated CO 2 , we compared the relative success of coral recruitment and later life stages at two volcanic CO 2 seeps and adjacent control sites in Papua New Guinea. Our field experiments showed that the effects of ocean acidification (OA) on coral recruitment rates were up to an order of magnitude greater than the effects on the survival and growth of established corals. Settlement rates, recruit and juvenile densities were best predicted by the presence of crustose coralline algae, as opposed to the direct effects of seawater CO 2 . Offspring from high CO 2 acclimatized parents had similarly impaired settlement rates as offspring from control parents. For most coral taxa, field data showed no evidence of cumulative and compounding detrimental effects of high CO 2 on successive life stages, and three taxa showed improved adult performance at high CO 2 that compensated for their low recruitment rates. Our data suggest that severely declining capacity for reefs to recover, due to altered settlement substrata and reduced coral recruitment, is likely to become a dominant mechanism of how OA will alter coral reefs.

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A possible link between coral reef success, crustose coralline algae and the evolution of herbivory

Scientific Reports ◽

10.1038/s41598-020-73900-9 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Sebastian Teichert ◽

Manuel Steinbauer ◽

Wolfgang Kiessling

Keyword(s):

Coral Reefs ◽

Coralline Algae ◽

Time Interval ◽

Crustose Coralline Algae ◽

Coralline Red Algae ◽

Potential Capacity ◽

Morphological Adaptations ◽

Geological Past ◽

Tropical Coral ◽

Negative Effect

Abstract Crustose coralline red algae (CCA) play a key role in the consolidation of many modern tropical coral reefs. It is unclear, however, if their function as reef consolidators was equally pronounced in the geological past. Using a comprehensive database on ancient reefs, we show a strong correlation between the presence of CCA and the formation of true coral reefs throughout the last 150 Ma. We investigated if repeated breakdowns in the potential capacity of CCA to spur reef development were associated with sea level, ocean temperature, CO2 concentration, CCA species diversity, and/or the evolution of major herbivore groups. Model results show that the correlation between the occurrence of CCA and the development of true coral reefs increased with CCA diversity and cooler ocean temperatures while the diversification of herbivores had a transient negative effect. The evolution of novel herbivore groups compromised the interaction between CCA and true reef growth at least three times in the investigated time interval. These crises have been overcome by morphological adaptations of CCA.

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Ocean warming and acidification have complex interactive effects on the dynamics of a marine fungal disease

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2013.3069 ◽

2014 ◽

Vol 281 (1778) ◽

pp. 20133069 ◽

Cited By ~ 32

Author(s):

Gareth J. Williams ◽

Nichole N. Price ◽

Blake Ushijima ◽

Greta S. Aeby ◽

Sean Callahan ◽

...

Keyword(s):

Climate Change ◽

Coral Reef ◽

Coral Reefs ◽

Fungal Disease ◽

Ocean Warming ◽

Interactive Effects ◽

Coralline Algae ◽

Future Climate Change ◽

Disease Dynamics ◽

Crustose Coralline Algae

Diseases threaten the structure and function of marine ecosystems and are contributing to the global decline of coral reefs. We currently lack an understanding of how climate change stressors, such as ocean acidification (OA) and warming, may simultaneously affect coral reef disease dynamics, particularly diseases threatening key reef-building organisms, for example crustose coralline algae (CCA). Here, we use coralline fungal disease (CFD), a previously described CCA disease from the Pacific, to examine these simultaneous effects using both field observations and experimental manipulations. We identify the associated fungus as belonging to the subphylum Ustilaginomycetes and show linear lesion expansion rates on individual hosts can reach 6.5 mm per day. Further, we demonstrate for the first time, to our knowledge, that ocean-warming events could increase the frequency of CFD outbreaks on coral reefs, but that OA-induced lowering of pH may ameliorate outbreaks by slowing lesion expansion rates on individual hosts. Lowered pH may still reduce overall host survivorship, however, by reducing calcification and facilitating fungal bio-erosion. Such complex, interactive effects between simultaneous extrinsic environmental stressors on disease dynamics are important to consider if we are to accurately predict the response of coral reef communities to future climate change.

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