DOI: 10.5061/dryad.pk0p2ngx0
title: The scaling of metabolic traits differs among larvae and juvenile colonies of scleractinian corals

description: Body size profoundly affects organism fitness and ecosystem dynamics
 through the scaling of physiological traits. This study tests for
 variation in metabolic scaling and its potential drivers among corals
 differing in life history strategies and taxonomic identity. Data were
 compiled from published sources and augmented with empirical measurements
 of corals in Moorea, French Polynesia. The data compilation revealed
 metabolic isometry in broadcasted larvae, but size-independent metabolism
 in brooded larvae; empirical measures of Pocillopora acuta larvae also
 supported size-independent metabolism in brooded coral larvae. In
 contrast, for juvenile colonies (i.e., 1–4 cm diameter), metabolic scaling
 was isometric for Pocillopora spp. and negatively allometric for Porites
 spp. The scaling of biomass with surface area was isometric for
 Pocillopora spp., but positively allometric for Porites spp., suggesting
 the surface area:biomass ratio mediates metabolic scaling in these corals.
 The scaling of tissue biomass and metabolism was not affected by light
 treatment (i.e., either natural photoperiods or constant darkness) in both
 juvenile taxa. However, biomass was reduced by 9–15% in the juvenile
 corals from the light treatments and this coincided with higher metabolic
 scaling exponents, thus supporting the causal role of biomass in driving
 variation in scaling. This study shows that metabolic scaling is plastic
 in the early life stages of corals, with intrinsic differences between
 life history strategy (i.e., brooded and broadcasted larvae) and taxa
 (i.e., Pocillopora spp. and Porites spp.), and acquired
 differences attributed to changes in area-normalized biomass.
description: Data were compiled from published sources and augmented with
 empirical measurements of corals in Moorea, French Polynesia. Data were
 processed through Excel and R software (R Development Core Team 2021,
 v1.4.1103) using the stats package (R Core Team, v4.0.3), and the car
 package (Fox and Weisberg, 2020, v3.0-10) used to test for the statistical
 assumptions of the procedures employed.
 <em>Metabolic scaling of larvae - data
 compilation</em> To investigate metabolic scaling
 of brooded and broadcasted larvae, data were compiled from peer-reviewed
 and grey literature identified using Web of Science, Google Scholar, and
 the published proceedings of the International Coral Reef Symposia which
 were available from 1972 to 2012 (accessed 11 May 2020). The keywords,
 “(scleractinia*) and (larva* or planula*) and (respirat* or metabolism or
 "metabolic rate" or metabolic)” were utilized, with the
 asterisks indicating different suffixes. The citation lists in the papers
 included in the data compilation were also searched for additional
 relevant sources. We searched for studies that reported oxygen consumption
 and dry biomass that were either standardized to or could be converted to,
 a per larva scale. Studies that reported proximal tissue composition
 (i.e., lipid or protein content) from which dry biomass could be
 calculated based on conversion factors (Table S1, see details in the
 supplementary materials of Bean and Edmunds 2024) were also included. Only
 data from studies in which larvae were kept under ambient seawater
 conditions (relative to the time and location of the study) with respect
 to temperature and pCO<sub>2</sub> were retained. Data were
 extracted from sources using values reported in the manuscript or
 supplementary material, or by digitizing plots presented therein using the
 online tool, WebPlot Digitizer (Rohatgi, 2021). Some data points from one
 study were not retrievable due to the resolution of the graphics and were
 omitted from the analysis. <em>Metabolic scaling
 of larvae – empirical data </em> To empirically
 quantify the scaling of metabolism in brooded larvae, respiration was
 measured for larvae freshly released from <em>Pocillopora
 acuta</em> (Lamark 1816) in Moorea, French Polynesia. To obtain
 larvae from <em>P. acuta</em>, 6 adult colonies were collected
 from a site on the north shore (17°28'59.67"S,
 149°48'49.91"W) at ~1 m depth. Colonies were collected on May
 15<sup>th</sup>, 2021 (lunar day 4) to sample peak release of
 larvae that occurs around lunar days 8–12. The colonies
 were taken to the Richard B. Gump South Pacific Research Station, where
 each was placed in a separate aquarium under shaded natural sunlight (~9
 µmol photons m<sup>-2 </sup>s<sup>-1</sup>) where
 they were supplied with sand-filtered seawater pumped directly from Cook’s
 Bay at 8 m depth. Larvae were collected by overflowing seawater from these
 aquaria into a container fitted with a 110 µm mesh window. Following the
 overnight release of larvae, they were collected the next morning from a
 single parent colony that had released the greatest number of
 larvae.  Larval respiration was measured for groups of
 similarly-sized larvae placed in 2 mL glass Autosampler vials (Biomed
 Scientific, part number: MGV2-9-CS-100Z), with the results expressed per
 larva. Respiration trials were conducted with 6 larvae
 vial<sup>-1</sup> with each trial considered a statistical
 replicate. To obtain larvae of similar sizes, freshly released larvae were
 coarsely sorted into 3 size classes (i.e., small, medium, large) by visual
 inspection using a dissecting microscope (40x magnification).
 Approximately 40 each of the largest, smallest, and medium-sized larvae
 (relative to the larval sizes on each day of release) were grouped and
 dark acclimated for 100 minutes. Following dark acclimation, batches of 6
 similarly-sized larvae were randomly selected from the three size groups
 and allocated to autosampler vials filled with filtered seawater (0.45 µm)
 with known oxygen saturation and covered with parafilm. At the conclusion
 of the respiration trial, larval size was measured by quantifying their
 protein content as described below. Throughout dark acclimation and
 respiration trials, larvae were maintained in filtered seawater (0.45 µm)
 at ambient seawater temperature (27.9°C) and salinity (34.7 ppt) relative
 to the time of collection of the maternal colonies. The temperature was
 regulated (± 0.1°C) using a water bath (Lauda Ecoline, model RE 104,
 Lauda-Königshofen, Germany), and measured with a certified thermometer
 (Fisher Scientific, model 15-077-8, Waltham, MA, USA, accuracy ± 0.1°C),
 and salinity were measured with a benchtop conductivity meter
 (ThermoFisher Scientific Orion Star A212, Waltham, MA, USA).
 Oxygen saturation was measured using a NEOFOX-GT optical oxygen
 sensing system fitted with a 1.6-mm diameter FOSPOR-R probe (Ocean
 Insight, Orlando, FL, USA). The probe was two-point calibrated at 0%
 (sodium sulfite and 0.01 M sodium tetraborate) and 100% oxygen saturation
 (air-saturated 0.45 µm filtered seawater (FSW)). The respiration of the
 larvae in the vials was measured in darkness for ~0.5–1.5 hrs, over which
 oxygen saturation remained &gt; 80% to prevent oxygen-dependent
 respiration. After the incubation period, the vials were carefully
 inverted to mix the seawater, and the oxygen probe was inserted through
 the parafilm to record the oxygen saturation. Oxygen saturation was
 converted to concentration using Unisense conversion tables and corrected
 with controls consisting of filtered seawater (0.45 µm). Following the
 respiration trials, larvae were frozen in seawater (-18°C) for
 determination of protein biomass. The protein content
 of the larvae was measured using the Bio-Rad Protein Assay (Bio-Rad
 Laboratories, CA, USA). Larvae were thawed, sonicated (Sonic Dismembrator
 500, Fisher Scientific, Waltham, MA, USA), heated in alkaline conditions
 using 1 M NaOH, and neutralized with 1.65 M HCl. Protein content (mg) was
 calculated using bovine serum albumin standards and converted to dry
 biomass (mg) assuming the larvae contain 17% protein
 <em>Metabolic scaling of juvenile
 corals</em> 11 juvenile colonies
 of <em>Pocillopora </em>spp. (excluding <em>P.
 acuta</em>) and 10 of massive <em>Porites </em>spp.
 (i.e., not including branching <em>Porites </em>spp.) were
 collected from the back reef of Moorea (17°28’25.65”S, 149°48’46.53”W) at
 ~2 m depth on November 8<sup>th</sup>, 2020. Juvenile colonies
 were collected to vary in size from 1 to 4 cm in diameter so that the
 scaling exponent for respiration could be measured. Corals were not
 morphologically distinguishable by species at this early life stage and
 were identified by genus. Colonies were chipped from the reef using a
 small chisel and attached to a plastic base using underwater epoxy (Z-Spar
 Splash Zone A-788). The portions of the colony bases that were not covered
 in live coral tissue were cleaned of organisms and covered with the same
 underwater epoxy. The colonies were left for 21 hours in flowing seawater
 under a shaded roof to let the epoxy harden before respiration was
 measured. The respiration rates of the juvenile corals
 were measured within 4 days of collection to minimize photo-acclimation to
 laboratory conditions and following 14–54 hours of darkness in flowing,
 sand-filtered water pumped from Cook’s Bay and maintained at an ambient
 temperature of ~27°C. Respiration trials were run over two days and were
 conducted by coral colony, alternating between taxa, with two seawater
 controls run daily. For each trial, a juvenile coral was placed inside a
 sealed 240 mL cylindrical chamber filled with 0.45 µm FSW and surrounded
 by a water jacket to regulate the temperature. All trials began at ~100%
 oxygen saturation and were conducted at ~27.3°C and ~34.3 ppt, which were
 the ambient conditions at the collection site when the analyses were
 completed (November 2020). A stir bar below the juveniles mixed the
 seawater during the trials, and juvenile corals were acclimated to chamber
 conditions for 10 minutes before sealing the chamber and measuring
 respiration through oxygen consumption recorded using a FOSPOR-R optical
 oxygen probe (Ocean Insight, Orlando, FL, USA). The probe was calibrated
 in the same manner as described above for larval respiration, and
 incubations lasted 20–60 minutes until a steady decline of oxygen
 saturation was recorded while ensuring that saturation remained &gt;
 80%. Following respiration trials, the surface area and
 the dry biomass of the corals were measured. The surface area of the
 juveniles was estimated geometrically by measuring two perpendicular
 diameters (i.e., length and width) and height, and assuming the colonies
 were vertical cylinders (see details in the supplementary materials of
 Bean and Edmunds 2024). Biomass was quantified by fixing the juvenile
 corals in 10% formalin in seawater for 48 hours, then decalcified in 5%
 HCl in distilled water over 1–7 days. The tissue was rinsed of formalin
 residue with deionized (DI) water before being placed in HCl to avoid the
 formation of bis-chloromethyl ether, a carcinogen. The tissue tunic was
 rinsed in DI water before being dried to a constant weight at
 60°C. <strong> </strong><em>Metabolic
 scaling between taxa in light and dark</em> To
 evaluate the role of biomass in mediating scaling relationships, the
 biomass of corals was indirectly manipulated by exposing corals to
 darkness (i.e., starvation) or natural photoperiods (i.e., 12:12 hr
 light:dark) of ambient light relative to the collection site as a control.
 Two tanks were maintained in darkness and two at a maximum of 967 ± 9 (±
 s.e.m.) μmol photons m<sup>−2</sup> s<sup>−1</sup>
 (measured with a Li-Cor 4π sensor fitted to a Li-Cor meter (LI-1400,
 Lincoln, NE, USA)) on a 12:12 hr light:dark photoperiod supplied through
 LED lights (75 W, Sol LED Module, Aqua-illumination, Ames, Iowa, USA).
 Thirty-two juvenile colonies of both <em>Pocillopora
 </em>spp<em>. </em>and massive <em>Porites
 </em>spp<em>. </em>were collected on May
 20<sup>th</sup>, 2021, from the back reef of Moorea at ~2 m
 depth (17°28’25.65” S, 149°48’46.53” W). Colonies were acclimated to
 laboratory conditions for 4 days before experimental trials took place.
 Tanks (150 L) were held at 28.5°C and 34.7 ppt and supplied with
 sand-filtered seawater from Cook’s Bay at ~400 mL
 min<sup>-1</sup> and each contained eight colonies of
 <em>Pocillopora </em>spp<em>. </em>and eight
 colonies of <em>Porites </em>spp<em>.</em>
 Colonies were held at treatment conditions for 9–12 days, depending on
 when they were used for respiration trials, and arranged daily in each
 tank to minimize position effects. Respiration was measured starting at 9
 days because the colonies in the dark tanks showed signs of physiological
 stress (i.e., paling). Two juveniles were measured concurrently for
 respiration in separate chambers with one control completed in each
 chamber daily. Colony selection for respiration trials alternated between
 tanks within each treatment and between taxa, and with 14–18 corals
 processed each day, all corals were processed in four days. The
 respiration rate of each colony was measured using the methods described
 above for juvenile corals. Following respiration
 trials, corals were frozen (-20 °C) and crushed with 2500 µL of 0.45 µm
 FSW to produce a slurry of skeleton and tissue. To maintain consistency of
 sampling, ~13 cm<sup>2</sup> of each coral colony was crushed
 with the area chosen as the size of the smallest colony in the experiment.
 The homogenate was used for the analysis of ash-free dry weight (AFDW)
 using a muffle furnace (5 hours at 450°C) (Fisher Scientific, model:
 650–126, Waltham, MA) and symbiont density using a hemocytometer (8
 replicate counts/sample).
description: # Scaling of metabolic traits of larvae and juvenile scleractinian corals
 [https://doi.org/10.5061/dryad.pk0p2ngx0](https://doi.org/10.5061/dryad.pk0p2ngx0) ## Description of the datasets for Bean and Edmunds 2024 ([https://doi.org/10.1242/jeb.246362)](https://doi.org/10.1242/jeb.246362\)) **"Data_compilation_list.xlsx"** contains all the literature screened for relevance to include in the data compilation.  **"Data_comp_data.xlsx"** is the data set containing all the compiled data from the data compilation. It includes "Source_resp" (i.e., where respiration rates were located), "n_resp" (i.e., number of larvae in each replicate for respiration rates), "Respiration_OG", "Respiration_OG_SE", and "Respiration_OG_units" which are the original respiration rates, standard error, and unit of measure of the respiration rates reported in the literature, "Source_energy" (i.e., the location where measures of biomass, protein, or lipids were found), "n_energy" (i.e., number of larvae in each replicate for the energy measure), "Biomass_ug.larva_dry" and "Biomass_ug.larva_dry_SE" which are the directly reported or estimated dry biomass and standard error of each larva in ug using the conversion assumptions in the "Biomass_assumptions" column. NA in the “Biomass_assumptions” column indicates not applicable because conversion assumptions were not needed. NA in the other columns indicates that these data were not taken and therefore are not available.  **"larvae.xlsx"** is the data set containing respiration and protein/biomass measures of *Pocillopora acuta* larvae obtained in Moorea, French Polynesia. It includes the "Temp_C" (i.e., temperature (°C)), "Genotype" (i.e., the genotype of the parental colony), "ID" (i.e., the ID of the vial containing 6 larvae), "Category_size" (i.e., size category of the larvae), "Dark acclimation" (i.e., time at which dark acclimation began), "Start_Time" (i.e., time at which respiration trials began), "Dark acclimation_min" (i.e., minutes larvae were dark acclimated), "End_Time" (i.e., time at which respiration trials ended), "incubation_time.min" (i.e., number of minutes respiration trials went on for), "umol/vial/min" (i.e., respiration rate in units of umol/vial/min), "umol/larva/min" (i.e., respiration rate in units of umol/larva/min), "pikomol.larva.min" (i.e., respiration rate in units of pikomol.larva.min), "ug.protein.larva" (i.e., protein content per larva in ug), and "Dry_weight.mg" (i.e., dry weight in mg of each larva).  **"R_wax_dipping.xlsx"** is the data set containing the wax dipping weights of juvenile *Pocillopora* and Porites corals used to determine the surface area of corals in the study. It includes the "max1.mm" (i.e., length of colony in mm), "max2.mm" (i.e., the width of the colony in mm), "height.mm" (i.e., the height of the colony in mm), "weight.g" (i.e., weight in grams before wax dipping), "dip1.g" (i.e., weight in grams after first dip in the wax), "dip2.g" (i.e., weight in grams after second dip in the wax), "dip2_change" (i.e., difference in weight between dip1.g and dip2.g in grams) and "SA.dip2.cm2" (i.e., surface area in cm^2 calculated from the dip2_change metric and the using calibration slope using standardized wooden dowels. NA in the notes column indicates “not applicable” because there was nothing to note. NA in the other columns indicates that these data were not taken and therefore are not available.  **"R_juve_resp_size_2020.xlsx"** is the data set for juvenile corals collected in situ and measured 4 days later. It includes the "Dry_weight.g" (i.e., calculated dry weight of the whole coral in grams), "Max.mm" (i.e., length of the colony in mm), "Min.mm" (i.e., the width of the colony in mm), "Height.mm" (i.e., the height of the colony in mm), "micromol.coral.min" (i.e., respiration rate in micromol/coral/min), "std.error" (i.e., standard error of the respiration rate), and "p.value", "adj.r.squared", and "r.squared" are values for the respiration rate.  **"environmental.xlsx"** is the data set for the environmental variables measured in the tanks of the light/dark experiment. It includes the "temp_C" (i.e., temperature (°C)), "light_PAR" (μmol photons m−2 s−1), and "flow_mL_min" (mL min-1). NA indicates that these data were not taken and therefore are not available.  **"R_juve_resp_size_2021.xlsx"** is the data set for juvenile corals in the light/dark experiment. It includes the "est.dry.weight.mg" (i.e., calculated dry weight of the whole coral in mg), "Max.mm" (i.e., length of the colony in mm), "Min.mm" (i.e., the width of the colony in mm), "Height.mm" (i.e., the height of the colony in mm), "micromol.coral.min" (i.e., the respiration rate in micromol/coral/min), "std.error" (i.e., standard error of the respiration rate), "chamber" (i.e., the chamber used for respiration trials), and "p.value", "adj.r.squared", and "r.squared" are values for the respiration rate.  **"symbionts_juveniles.xlsx"** is the data set containing the symbiont counts of juveniles in the light/dark experiment. It includes the "rep" (i.e., replication) and "counts" (i.e., symbiont counts). NA in the notes column indicates “not applicable” because there was nothing to note. **"R_juve_AFDW_2021.xlsx"** is the data set containing the biomass of juvenile corals in the light/dark experiment. It includes the "AFDW.whole.coral.ug" (i.e., ash-free dry weight of the whole coral in ug).