Is the coral-algae symbiosis really ‘mutually beneficial’ for the partners?

 Is the coral-algae symbiosis really ‘mutually beneficial’ for the partners? 

Scott Wooldridge
DOI: 10.1002/bies.200900182 · Source: PubMed

In terms of the demand for CO2(aq), an enlarged endosymbiont population increases the likelihood of CO2(aq) becoming a limiting internal substrate during periods of peak photosynthesis [18, 19]. Several environmental factors favour increased zooxanthellae densities (particularly on a per host cell basis), including: (i) elevated nutrient levels (e.g. dissolved inorganic nitrogen, DIN) in the surrounding sea water [20], elevation of the CO2 partial pressure (pCO2) in the surrounding sea water [21], and diffusive (i.e. branching) coral colony morphologies [22]. Experimental manipulations confirm the higher expulsion rate of zooxanthellae during periods of high irradiance in branching corals [23] and in corals exposed to DIN and pCO2 enrichment [24, 25].

Fast Growth May Impair Regeneration Capacity in the Branching Coral Acropora muricata

Fast Growth May Impair Regeneration Capacity in the Branching Coral Acropora muricata

Vianney Denis, Mireille M. M. Guillaume, Madeleine Goutx, Stéphane de Palmas, Julien Debreuil, Andrew C. Baker, Roxane K. Boonstra, J. Henrich Bruggemann
Research Article | published 30 Aug 2013 PLOS ONE
http://dx.doi.org/10.1371/journal.pone.0072618

At the sheltered site characterized by high temperatures, temperature variations, and irradiance levels, regeneration took 192 days on average. At the exposed site, characterized by steadier temperatures and lower irradiation, nubbins demonstrated fast lesion repair (81 days), slower growth, lower zooxanthellae density, chlorophyll a concentration and lipid content than at the former site. A trade-off between growth and regeneration rates was evident here.

Continue reading “Fast Growth May Impair Regeneration Capacity in the Branching Coral Acropora muricata”

Trophic dynamics of scleractinian corals: stable isotope evidence

Trophic dynamics of scleractinian corals: stable isotope evidence

Pascale TremblayJean François MaguerRenaud GroverChristine Ferrier-Pagès

Bacterivory in algae: A survival strategy during nutrient limitation

Bacterivory in algae: A survival strategy during nutrient limitation

Association for the Sciences of Limnology and Oceanography
http://aslo.org/lo/toc/vol_38/issue_2/

Table of Contents, Vol. 38 (2), 1993
NYGAARD, KARI, AND AUGUST TOBIESEN
“Bacterivory in algae: A survival strategy during nutrient limitation” p.273-279

Bacteria have a high P content even when phosphate is limited (Andersen et al. 1986), although their P content can be reduced when they are drastically starved (Tezuka 1990). Bacteria are therefore a potential source of P when obligate phototrophic algal flagellates are subjected to P limitation, because bacteria are more efficient at sequestering P under these conditions (Bratbak and Thingstad 198 5).

Phosphate deficiency alone may be insufficient for the success of bacterivorous algae because their growth requires that other environmental factors are also favorable.

Bacteria have been shown to out-compete algal flagellates in phosphate-limited chemostats at low dilution rates (Currie and Kalff 1984; Bratbak and Thingstad 1985).

Our results suggest that algae able to graze and use P compounds in the bacteria will have a compensatory mechanism to overcome their competitive disadvantage.

If you want to avoid toxic algae in your tank, avoid this condition!

Function of Funnel-Shaped Coral Growth in a High-Sedimentation Environment

Function of Funnel-Shaped Coral Growth in a High-Sedimentation Environment

Bernhard Riegl, Carlton Heine, and George M. Branch. 1996. Function of Funnel-Shaped Coral Growth in a High-Sedimentation Environment .Marine Ecology Progress Series : 87 -93.
http://nsuworks.nova.edu/occ_facarticles/336.

“Current speeds between 30 and 90 cm s-1 were enough to clean the funnels of 3 experimental grain sizes (coarse, fine, medium sand).”

High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

Claire GodinotRenaud GroverDenis AllemandChristine Ferrier-Pagès

Ratio of Energy and Nutrient Fluxes Regulates Symbiosis between Zooxanthellae and Corals

Ratio of Energy and Nutrient Fluxes Regulates Symbiosis between Zooxanthellae and Corals

Dubinsky Z, Jokiel PL. 1994. Ratio of energy and nutrient fluxes regulates symbiosis between zooxanthellae and corals. Pac Sci 48(3): 313-324.

http://hdl.handle.net/10125/2241

Full article available.

(See also: https://pacificscience.wordpress.com/open-access-v1-v54/pacific-science-48-1994/)

[Summarizing] the main interactions and feedback mechanisms connecting light intensity, nutrient level, and feeding in zooxanthellate corals:

  1. Under constant nutrient concentration, light intensity determines the onset of nutrient limitation; as light increases, C : N ratios exceed Redfield ratios.
  2. The availability of other nutrients, mainly nitrogen, determines the fate of photo-assimilated carbon. Under high C: N ratios, most carbon goes into respiration, calcification, and excreted mucus, whereas low C : N ratios favor increases in zooxanthellae density, reduce translocation, and slow down calcification.
  3. Feeding on zooplankton by the coral under low light provides carbon for metabolism. Under high light it supplies both algae and animal with nitrogen.

Nutrient balance is one of the most important, but seemingly lease understood aspects of aquarium keeping.  This statement from the article summarizes it as well as I’ve seen it summarized.  I’ve edited only for clarity.

Also from this article:

Nutrients acquired by predation of the coral on zooplankton are available first to the animal, whereas those absorbed by the zooxanthellae from seawater as inorganic compounds lead first to growth of the algae.