Sponges have an outsized influence on organic carbon cycles on Caribbean coral reefs. However, little is known about what types of carbon are consumed by sponges from the dissolved organic matter (DOM), whether they transform the unrespired fraction of this carbon to detritus or biomass, and how these transformations vary across functional groups, namely the divisions of species based on microbiome abundance, sponge morphologies, and chemical defenses.
*new* watch the 3-part zoom recording of my dissertation defense on 11 November 2022:
introduction and part 1:
part 2:
part 3 and conclusion
Abstract: Sponges have an outsized influence on organic carbon cycles on Caribbean coral reefs. However, little is known about what types of carbon are consumed by sponges from the dissolved organic matter (DOM), whether they transform the unrespired fraction of this carbon to detritus or biomass, and how these transformations vary across functional groups, namely the divisions of species based on microbiome abundance, sponge morphologies, and chemical defenses.
In chapters 1 and 2, I used untargeted metabolomics to molecularly characterize DOM taken up by sponges on the forereef of Carrie Bow Cay (CBC), Belize. I found that only sponges with high microbial abundance (HMA) took up DOM, including many compounds that were halogenated ( Ch. 1 ) and produced by nearby benthic cyanobacterial mats (BCM; Ch. 2).
In chapter 3, I used a combination of bulk stable isotope analyses and DNA metabarcoding to evaluate the composition of detritus on CBC and found a negligible sponge signature in the detritus and dominant contribution by benthic and pelagic primary producers.
In the third part of this research (Ch. 4), I used photogrammetry to estimate the growth rates of 16 species of sponges on a shipwreck and found that species without chemical defenses grew faster than species with chemical defenses, corroborating past findings. Sponges transform dissolved carbon to biomass and not detritus, but this transformation varies across functional groups, and the net effect to the ecosystem may be harmful, particularly on reefs where sponges and other non-reef builders (e.g., BCM) are proliferating.
In chapters 1 and 2, I used untargeted metabolomics to molecularly characterize DOM taken up by sponges on the forereef of Carrie Bow Cay (CBC), Belize. I found that only sponges with high microbial abundance (HMA) took up DOM, including many compounds that were halogenated ( Ch. 1 ) and produced by nearby benthic cyanobacterial mats (BCM; Ch. 2).
In chapter 3, I used a combination of bulk stable isotope analyses and DNA metabarcoding to evaluate the composition of detritus on CBC and found a negligible sponge signature in the detritus and dominant contribution by benthic and pelagic primary producers.
In the third part of this research (Ch. 4), I used photogrammetry to estimate the growth rates of 16 species of sponges on a shipwreck and found that species without chemical defenses grew faster than species with chemical defenses, corroborating past findings. Sponges transform dissolved carbon to biomass and not detritus, but this transformation varies across functional groups, and the net effect to the ecosystem may be harmful, particularly on reefs where sponges and other non-reef builders (e.g., BCM) are proliferating.
some photos of our research at Carrie Bow Cay and UNCW:
last updated 15 November 2022