Microsensor studies of photosynthesis and respiration in larger symbiotic foraminifera. I The physico-chemical microenvironment of Marginopora vertebralis, Amphistegina lobifera and Amphisorus hemprichii

Calcification acidifies the microenvironment of a benthic foraminifer (Ammonia sp.)

“…2) is in accordance with previous microsensor measurements, showing high spatial variability of Ca 2+ microgradients in Amphistegina lobifera and Marginopora vertebralis (Koehler- Rink and Kuehl, 2000) and among specimens in Orbulina universa (Koehler- Rink and Kuehl, 2005). This indicates that Ca 2+ uptake varies temporally and spatially over the shell surface of Ammonia sp.…”

“…This indicates that Ca 2+ uptake varies temporally and spatially over the shell surface of Ammonia sp. (Koehler-Rink and Kuehl, 2000). The absence of an overall significant calcium gradient during chamber formation in the microenvironment can be explained in two ways: 1) Ca 2+ was not transported from the external seawater into the DBS via channel-pumping, but supplied via an intracellular calcium pool as shown by Anderson and Faber (1984), ter Kuile and Erez (1988) and ter Kuile et al (1989).…”

A novel mechanism for host-mediated photoprotection in endosymbiotic foraminifera

“…Although Symbiodinium showed photosynthetic plasticity, it is evident that the physical relocation of surface symbionts into the foraminiferal test contributed to preventing long-term photosynthetic damage. This is supported by a previous study which found that only 30% of the incoming irradiance was able to penetrate to the bottom of the test of M. vertebralis (Kohler-Rink and Kühl, 2000). In addition to the inherent shading effect of the test itself (Kohler-Rink and Kühl, 2000), the increased reflectivity of the test decreased the incoming irradiance by an additional 20% upon symbiont retraction.…”

“…This is supported by a previous study which found that only 30% of the incoming irradiance was able to penetrate to the bottom of the test of M. vertebralis (Kohler-Rink and Kühl, 2000). In addition to the inherent shading effect of the test itself (Kohler-Rink and Kühl, 2000), the increased reflectivity of the test decreased the incoming irradiance by an additional 20% upon symbiont retraction. The efficacy of this photoprotective strategy is supported by the high photosynthetic activity measured in symbionts on the underside of the test during exposure to high irradiance and the rapid reversibility in photosynthetic quenching, Q M and xanthophyll pigment epoxidation of surface symbionts when incoming irradiance was lowered.…”

The Microenvironment and Photosynthetic Performance of Prochloron SP. in Symbiosis with Didemnid Ascidians

“…Yet, the microenvironment of Prochloron remains virtually unstudied. Use of minimally invasive microsensor techniques (reviewed in Kühl and Revsbech 2001) has given new insights to microenvironmental controls in the symbioses of microalgae with corals (Kühl et al 1995;De Beer et al 2000, Salih et al 2000, benthic foraminifera (Köhler-Rink and Kühl 2000), and sponges (Sand-Jensen and Pedersen 1994). Recently, we have used a similar approach to study Prochloron-ascidian associations (Kühl and Larkum, 2001).…”