Thread by @coraloha

Excited to share our recent work (& last chapter of my PhD) in #ISMEJ on #Symbiodiniaceae functional diversity, niche partitioning & isotopes in #corals across a rapid light-attenuation gradient (a thread..) @GatesCoralLab @himb_soest @uhmanoa @DonahueLab go.nature.com/2N1FDSm

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Corals depend on their symbionts (Symbiodiniaceae) for food, but #heterotrophy is also important--especially during periods of stress and low autotrophy (low light). But these symbionts show differences in autotrophic capacity and some (#Durusidinium spp.) may be opportunistic.

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Isotopes are a great way to understand nutrition and trophic ecology in ALL living things. We used isotopes and physiology metrics to understand how a single Hawaiian coral species (Montipora capitata) dominated by 2 different symbiont species were balancing auto- & heterotrophy.

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab In Kāne'ohe Bay these symbiont communties (dominated by #Cladocopium spp. and #Durusdinium spp.) partition across a short depth gradient with very rapid light-attenuation. How attenuated? 7m Kāne'ohe = 20-40m Red Sea, and communities shift from D to C quickly at 2-3m from surface

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab We found partitioning of symbiont communities to be consistent among reefs (previously shown by Innis et al. 2018 Coral Reefs) and seasons, but D-colonies do persist at depth, although rare. This supports the role of light in partitioning the niches of coral holobionts.

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab The finding of D-symbionts (temp stress and light stress resistant) at the surface and C-symbionts greater at depth supports findings from Caribbean and Red Sea where specialist symbionts like Cladocopium outcompete in lower light/temp ranges, whereas Durusdinium does poorly

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Traits of holobionts were also quite distinct: D-colonies had ~1.5-2.0x as many symbionts as their C-colony conspecifics, which we believe indicates Durusdinium is exploiting its host, providing < fixed-C, stimulating host N-release, with >symbiont growth (Cui et al. PlosOne)

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Now... #isotopes. Our d13C data support lower fixed carbon and translocation by Durusdinium (poor nutritional symbiont, low autotrophy) and this pattern is maintained across depth gradients--an exciting and novel finding. However, data DID NOT support a change in heterotrophy

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab In fact, we saw declining d13C values in host and symbionts (=lower rates of fixed-C, greater isotope fractionation or 12C incorporation [google that one]). BUT isotope values in host minus symbiont (more neg. = more hetero.) were opposite expectations of low-light = more hetero

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab So what does this all mean? (1) Symbiont communities are important in the nutrition of corals and symbiont functional diversity IS shaping the isotope values of corals. Ignoring this fact could lead to incorrect inferences on coral nutrition across space and time and species.

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab (2) Corals are not necessarily more heterotrophic when light becomes limited, even in species previously reported to exhibit nutritional plasticity (such as under bleaching stress in the lab). In fact, the more positive H-S isotope values = suggest > autotrophy at depth. (Hunh?)

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab On this last point I (Wall et al. 2019 Limnol. Oceanogr.) along with others (Einbinder et al. 2009 MEPS) have shown #isotope values are influenced by tissue compounds (lipids, carbs, proteins) and there is a need to resolve the ecological implications of these effects further.

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Finally, (3) Our work suggest opportunism by Durusdinium may be strategic--sending less carbon to the host, perturbing nitrogen cycling, and producing 2x more algal cells compared to 'good' symbionts, with implications for coral bleaching and performance (see Cunning et al works)

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab And one more--this work would have not been possible with my committee and field team. More so, my undergraduate intern Mario Kaluhiokalani (#NativeTwitter kanaka maoli [Native #Hawaiian]) was invaluable to this product. He's amazing, this is his first pub, & I'm Stoked For HIM!

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab One, one more-- this is open access (paper and data!)

data and script: github.com/cbwall/Coral-i…

zenodo DOI: zenodo.org/record/3583424…

and once more: the paper! go.nature.com/2N1FDSm

@GatesCoralLab @himb_soest @uhmanoa @DonahueLab Twitter bot @threadreaderapp #unroll please