Dataset: coral growth isotope spike experiment
Deployment: lab_Cohen_WHOI

Methodology as described in Holcomb et al. (2013):

Colonies of the temperate scleractinian coral Astrangia poculata were collected and processed as previously described. Newly settled polyps and their associated substratum were attached to slides. The slides with corals were suspended vertically in a flow-through aquarium receiving 20 micrometers filtered Vineyard Sound seawater. Corals experienced a temperature range of 14 to 30 degrees C. Aquaria were aerated, and corals were maintained under these conditions for at least one month prior to use in experiments. A mixture of brown and white colonies (zooxanthellate and azooxanthellate colonies) was used for all treatments.

For the marking experiments, corals were placed in pre-washed containers with lids containing ~800 ml of water from the source aquarium. Airstones were added to each container and each container bubbled continuously. Containers were held within a water bath with a temperature similar to that of the source aquarium.

Ba 135 or Sr 86 isotope spikes (purchased as carbonate salts from Oak Ridge National Lab) were used as markers in some incubations. See the "coral growth dye experiment" dataset for results from marking experiments using one of four dyes (alizarin, alizarin complexone, calcein, and oxytetracycline).

The isotope spike marking was carried out as part of long term growth experiments (see Holcomb et al. 2010 and 2012). Six to sixteen corals were used in each of the isotope spike treatments. For marking with 86Sr, 60 microliters of an 86Sr solution were added to ~800 ml seawater and the corals were incubated for two days. Growth was estimated from changes in buoyant weight (per Holcomb et al., 2010) for the 5 months prior to and the month following the isotope spike. Corals were held at one of two temperatures: ~19 or ~26 degrees C throughout that six month period.

Spikes with 135Ba were carried out in a flow-through aquarium system (see Holcomb et al., 2012). Each reservoir supplying water to individual aquaria was spiked with 81 microliters of 135Ba solution per liter of seawater. The aquaria received spiked seawater for two days, after which unspiked seawater was added to the reservoir, diluting the spike. Buoyant weights were measured for the two months prior and one month following isotope exposure using a Sartorius G803S balance, and the aquaria were held at either 16 or 24 degrees C throughout this time.