Water flow influences the mechanisms and outcomes of interactions between massive Porites and coral reef algae

Brown, A. L.; Carpenter, Robert C.

doi:10.1007/s00227-014-2593-5

Cited by 16 publications

(14 citation statements)

References 51 publications

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“…Increased flow commonly results in thinner DBLs [56,59]. Previous studies showed that high flow reduces algal competitiveness over corals and bacterial concentrations at the coral -algal interaction zone [60,61]. Furthermore, our study shows that thick turf oriented upstream retains the hyper-and hypoxic conditions at the coral-algal interface more strongly compared to thin turf, supporting the importance of algal canopy height, flow speed, and orientation in watermediated interactions between corals and algae.…”

Section: Discussionsupporting

confidence: 79%

Evidence for water-mediated mechanisms in coral–algal interactions

et al. 2016

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Although many coral reefs have shifted from coral-to-algal dominance, the consequence of such a transition for coral -algal interactions and their underlying mechanisms remain poorly understood. At the microscale, it is unclear how diffusive boundary layers (DBLs) and surface oxygen concentrations at the coral -algal interface vary with algal competitors and competitiveness. Using field observations and microsensor measurements in a flow chamber, we show that coral (massive Porites) interfaces with thick turf algae, macroalgae, and cyanobacteria, which are successful competitors against coral in the field, are characterized by a thick DBL and hypoxia at night. In contrast, coral interfaces with crustose coralline algae, conspecifics, and thin turf algae, which are poorer competitors, have a thin DBL and low hypoxia at night. Furthermore, DBL thickness and hypoxia at the interface with turf decreased with increasing flow speed, but not when thick turf was upstream. Our results support the importance of water-mediated transport mechanisms in coral-algal interactions. Shifts towards algal dominance, particularly dense assemblages, may lead to thicker DBLs, higher hypoxia, and higher concentrations of harmful metabolites and pathogens along coral borders, which in turn may facilitate algal overgrowth of live corals. These effects may be mediated by flow speed and orientation.

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Section: Discussionsupporting

confidence: 79%

Evidence for water-mediated mechanisms in coral–algal interactions

et al. 2016

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“…Additional plaster corals were placed in a bucket filled with the same seawater as contained in the flume, and left undisturbed as controls during the dissolution trial. The proportion of plaster corals dissolving in still water was multiplied by the initial mass of the plaster corals placed in the flume to correct for dissolution in still water, providing a corrected measure of the dissolution resulting from seawater motion in the flume (after Brown and Carpenter, 2015). The final dry mass of each coral cast after the flume incubations was subtracted from the corrected initial mass and expressed as a dissolution rate (g h −1 ).…”

Section: Flow Characteristicsmentioning

confidence: 99%

Conspecific aggregations mitigate the effects of ocean acidification on calcification of the coral Pocillopora verrucosa

Evensen

Edmunds

2017

Journal of Experimental Biology

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In densely populated communities, such as coral reefs, organisms can modify the physical and chemical environment for neighbouring individuals. We tested the hypothesis that colony density (12 colonies each placed ∼0.5 cm apart versus ∼8 cm apart) can modulate the physiological response (measured through rates of calcification, photosynthesis and respiration in the light and dark) of the coral Pocillopora verrucosa to partial pressure of CO 2 (P CO2 ) treatments (∼400 μatm and ∼1200 μatm) by altering the seawater flow regimes experienced by colonies placed in aggregations within a flume at a single flow speed. While light calcification decreased 20% under elevated versus ambient P CO2 for colonies in low-density aggregations, light calcification of high-density aggregations increased 23% at elevated versus ambient P CO2 . As a result, densely aggregated corals maintained calcification rates over 24 h that were comparable to those maintained under ambient P CO2 , despite a 45% decrease in dark calcification at elevated versus ambient P CO2 . Additionally, densely aggregated corals experienced reduced flow speeds and higher seawater retention times between colonies owing to the formation of eddies. These results support recent indications that neighbouring organisms, such as the conspecific coral colonies in the present example, can create smallscale refugia from the negative effects of ocean acidification.

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“…While studies have quantified measurement errors that arise from using this technique compared to 'true' volume and surface area [12][13][14] or rugosity [10,14], no study has determined error margins for measurements obtained over time and across different observers. Moreover, no research has attempted to measure the volume and surface area of an ecologically-relevant reef feature often used in reef monitoring, the coral bommie [15][16][17]. Such 3D measurements of bommies are essential for our understanding of the reef's capacity to support assemblages of fishes [18], assess their reef-building capacity [14,19], nutrient requirements [20], and to understand the extent of impacts, such as coral bleaching [21].…”

Section: Introductionmentioning

confidence: 99%

How Reliable Is Structure from Motion (SfM) over Time and between Observers? A Case Study Using Coral Reef Bommies

et al. 2017

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Recent efforts to monitor the health of coral reefs have highlighted the benefits of using structure from motion-based assessments, and despite increasing use of this technique in ecology and geomorphology, no study has attempted to quantify the precision of this technique over time and across different observers. This study determined whether 3D models of an ecologically relevant reef structure, the coral bommie, could be constructed using structure from motion and be reliably used to measure bommie volume and surface area between different observers and over time. We also determined whether the number of images used to construct a model had an impact on the final measurements. Three dimensional models were constructed of over twenty coral bommies from Heron Island, a coral cay at the southern end of the Great Barrier Reef. This study did not detect any significant observer effect, and there were no significant differences in measurements over four sampling days. The mean measurement error across all bommies and between observers was 15 ± 2% for volume measurements and 12 ± 1% for surface area measurements. There was no relationship between the number of pictures taken for a reconstruction and the measurements from that model, however, more photographs were necessary to be able to reconstruct complete coral bommies larger than 1 m 3 . These results suggest that structure from motion is a viable tool for ongoing monitoring of ecologically-significant coral reefs, especially to establish effects of disturbances, provided the measurement error is considered.

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Water flow influences the mechanisms and outcomes of interactions between massive Porites and coral reef algae

Cited by 16 publications

References 51 publications

Evidence for water-mediated mechanisms in coral–algal interactions

Evidence for water-mediated mechanisms in coral–algal interactions

Conspecific aggregations mitigate the effects of ocean acidification on calcification of the coral Pocillopora verrucosa

How Reliable Is Structure from Motion (SfM) over Time and between Observers? A Case Study Using Coral Reef Bommies

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