Reef Cloverson / Coral science
What helps young Acropora grow?
What actually nourishes a coral? Endosymbiotic algae inside its tissues supply carbon compounds made through photosynthesis, while polyps capture prey. [1] [2] The coral and its associated microbes can also take up dissolved nutrients and trace elements from seawater. [3] [4] Understanding those connections helps reefers ask better questions about what they put into an aquarium.
Four treatments. Three tanks each.
Newly settled recruits of Acropora hyacinthus, A. loripes, A. millepora, and A. tenuis were studied. Each tank symbol represents one replicate; read across for the significant growth comparisons. [1]
A. tenuis: more growth than all three other treatments.
Read each result within a species. The comparisons above were statistically significant (p < 0.05). No significant treatment differences in growth were detected for A. hyacinthus or A. loripes. [1]
No statistically significant treatment difference was detected. This does not establish equal survival. [1]
Change in surface area measured from images, rather than a measurement of skeletal mass. [1]
What remains unresolved?
Unfiltered seawater changes dissolved inputs, suspended food, and microbes together. The experiment did not isolate which component caused the growth difference. [1]
Biochemical context. The study also examined lipids and fatty acids. Total lipid concentration was relatively stable across treatments, while lipid-class and fatty-acid profiles varied. Those associations do not establish a causal nutrient requirement. [1]
How dissolved uptake works. In Stylophora pistillata, dissolved amino-acid uptake included active, carrier-mediated transport at low concentrations. [3] Metal accumulation also differed among elements and components of the coral holobiont. [4] These findings describe possible uptake pathways; they do not explain the Acropora treatment effect by themselves.
Limits: Three tanks per treatment; the formulated-feed recipe was undisclosed. [1] The result should be interpreted for these recruits and conditions, without assuming the same response in mature colonies or other systems.
Authors’ next direction: Identify beneficial features of unfiltered seawater to inform controlled feeding regimes. [1]
My interpretation. This study is a reason to test food and nutrient combinations more carefully. It does not identify a supplement to dose, an optimal concentration, or a universal feeding recipe.
Methods: How they did it
Four feeding regimes were randomly assigned to 12 flow-through tanks of 49 L, with three tanks per regime. Analyses adjusted for initial recruit counts. [1]
BaselineDay 46
Follow-upDay 93
Final
Day 0 was two days after settlement. Survival, surface area, and fusion were assessed at baseline and 46 and 93 days later. [1]
Sources
The review centers on Conlan et al. (2017). The additional studies support the biological context; they are separate experiments in Stylophora pistillata.
- Jessica A. Conlan, Craig A. Humphrey, Andrea Severati, and David S. Francis (2017). Influence of different feeding regimes on the survival, growth, and biochemical composition of Acropora coral recruits. PLOS ONE 12(11): e0188568. DOI: 10.1371/journal.pone.0188568.
- Pascale Tremblay, Renaud Grover, Jean François Maguer, Louis Legendre, and Christine Ferrier-Pagès (2012). Autotrophic carbon budget in coral tissue: a new 13C-based model of photosynthate translocation. Journal of Experimental Biology 215: 1384–1393. DOI: 10.1242/jeb.065201.
- Renaud Grover, Jean-François Maguer, Denis Allemand, and Christine Ferrier-Pagès (2008). Uptake of dissolved free amino acids by the scleractinian coral Stylophora pistillata. Journal of Experimental Biology 211: 860–865. DOI: 10.1242/jeb.012807.
- Marc Metian et al. (2015). Metal bioconcentration in the scleractinian coral Stylophora pistillata: investigating the role of different components of the holobiont using radiotracers. Environmental Monitoring and Assessment 187: 178. DOI: 10.1007/s10661-015-4383-z.
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