Dataset: coral growth dye 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.

One of four dyes was used to mark the coral skeleton: alizarin red S (sodium salt – Alfa Aesar 42040 lot E22R017 – referred to as alizarin), alizarin complexone (Alfa Aesar A16699 lot E8180A), calcein (Alfa Aesar L10255 lot USLF006789), and oxytetracycline HCl (USB 23659 lot 113648).

The dye experiments took place from March to October 2009. Growth rates were estimated via alkalinity depletion measurements the day before (pre-treatment), the day of (treatment), and the day after (post-treatment) dye exposure. The alkalinity incubations were about 24 hours in duration (one full light-dark cycle). Temperatures ranged from 25 to 26 degrees C. Four to seven corals were used in each treatment, each in a separate incubation container. Irradiance in each container, measured using a diving-PAM underwater quantum sensor (WALZ), ranged from 10 to 40 micromoles photons/m^2/sec.

Samples for alkalinity were taken from each container about 1 hour after the corals were added, and once again at the end of the incubation. Salinity and pH were also measured at the end of each incubation for each container (and at the start for a sub-set of the containers). Aragonite deposition was assumed to be the only process affecting alkalinity, with 2 mol alkalinity consumed per mol of CaCO3 deposited. Alkalinity depletion rates were corrected for evaporation and background rates measured in the control containers (the control containers contained no slides).

Alkalinity was measured via titration with 0.01 N HCl containing 40.7 g NaCl/l using a Metrohm Titrando 808 Dosimat and a 730 Sample Changer controlled by Tiamo software to perform automated normalized Gran titrations of 1 ml samples.