The effects of water flow and sedimentation on interactions between massive Porites and algal turf

Gowan, J.C.; Tootell, Jesse S.; Carpenter, Robert C.

doi:10.1007/s00338-014-1154-1

Cited by 32 publications

(39 citation statements)

References 81 publications

(138 reference statements)

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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: 80%

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: 80%

Evidence for water-mediated mechanisms in coral–algal interactions

et al. 2016

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“…Despite the well known direct negative effects of sediment on coral recruitment, increased sediment levels in coral reefs have been found to reduce the growth of algae [16,45,55] and therefore mitigate the negative effects of algae on recruit density. This is similar to previous findings [4,6,8,17,33] where reduced algal abundance but improved coral recruitment and settlement were reported in reefs with increased terrestrial influence.…”

Section: Discussionsupporting

confidence: 93%

“…Whereas nutrients indirectly reduce coral settlement by promoting algal growth, sediments on the other hand have been reported to inhibit algal settlement, thus countering the negative effects of nutrients on coral recruitment, therefore enhancing coral settlement and recruitment [4,8,12,15,44]. Additionally, the hydrodynamic characteristics of Malindi reef may also have played a vital role in improving coral recruitment (see [34]). The presence of swift currents and moderate wave action and the presence of a deep-water channel possibly increased flushing rates, thus reducing sediment accumulation, but enhanced larval settlement [6] in Malindi reef.…”

Section: Discussionmentioning

confidence: 99%

“…A number of studies have shown corals to be inferior competitors relative to algae [30,31]; however, other authors have found corals to be the superior competitors, only releasing algae from competitive inhibition under stressful conditions [4,32], such as land-based (terrestrial) discharge. Modification of algal-coral competition by disturbances of terrestrial origin may thus play a crucial role in mediating optimal habitat characteristics, diversity, resilience, and recovery potential of disturbed reefs [33][34][35][36][37]. Herbivorous fishes regulate algal growth on coral reefs and are important for maintaining resilient, coral-dominated ecosystems.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Coral Recruit-Algae Interactions in Coral Reef Lagoons Are Mediated by Riverine Influences

Mwachireya

Nzioka

Mutiso

2017

International Journal of Ecology

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Coral recruit and algae abundance and diversity were studied in Kenyan reefs to determine the influence of terrestrial discharge (nutrients and sediments) and the recovery potential of coral reefs after disturbances. Reefs affected by sediments and nutrients were found to have high total, turf, and macroalgae but reduced coralline algae abundance and coral recruit density. Interestingly, this response was found to be the greatest in reefs close to nutrient sources relative to "pristine" reefs and those affected simultaneously by sediments and nutrients. Further, enhanced levels of brown algae and pocilloporid recruits were observed in reefs affected by terrestrial run-off whereas acroporid recruit, coralline, and calcareous algae abundance was high in reefs under low terrestrial input. Our results show that whereas increased sediment levels negatively affect coral recruit density individually, their interaction with nutrients improves recruit density in reefs simultaneously affected by sediment and nutrients. These findings suggest that the assessment of local factors that enhance inhibitory and those that suppress promotional processes involved in coral settlement and recruitment is an important aspect to consider in the conservation and management of coral reefs in the face of local anthropogenic stress as well as future climate disturbance dynamics and their interaction.

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“…For example, sedimentation is a major stressor on coral reefs that can lead to coral decline by smothering and killing adult corals and can impede coral recovery by preventing the successful recruitment of coral larvae (Rogers 1990). By trapping sediments, algal turfs can interact with sedimentation to increase coral mortality, reduce coral growth, and impede coral settlement (Nugues & Roberts 2003, Birrell et al 2005, Gowan et al 2014. Fishing could therefore act synergistically with sedimentation to suppress corals by reducing herbivory and allowing the development of mats of sediment-trapping algal turfs.…”

Section: Knowledge Gapsmentioning

confidence: 99%