Oxygen production and consumption were measured in five species of benthic foraminifers using a "Clark-type" oxygen electrode. Net photosynthesis and respiration were calculated and normalized to both μg Chl a and mm² upper surface area for the chlorophyte-bearing soritid foraminifers, Archaias angulatus and Cyclorbiculina compressa, and the diatom-bearing amphisteginids, Amphistegina gibbosa, A. lessonii and A. radiata. Photosynthesis/Irradiance curves were generated by fitting data to the hyperbolic tangent equation P = Pmax tanh (α I/ Pmax). Derived photosynthetic parameters, Pmax, α, Ik were found to correspond to the general responses of the endosymbiont taxa. Chlorophyll concentration was found to be significantly lower in Cyclorbiculina compressa than in the other four species. Maximum O2 production (Pmax) when normalized to Chl a was 3-4 times higher in soritid species than in amphisteginids. Photosynthetic efficiency (α) was significantly higher in Amphistegina gibbosa and A. lessonii than in the soritids. Mean Ik, which indicates approaching light saturation, was 13 and 26 μmol photon m-2sec-1 respectively for A. gibbosa and A. lessonii compared with 95 and 119 μmol photon m-2sec-1 respectively for Archaias and Cyclorbiculina. Calculated P/I data were to variable for Amphistegina radiata to estimate reliable α and Ik values. Factorial metabolic scope, which indicates potential for activity was only 2-6 for amphisteginids versus 9-16 for soritids. Annual primary production was estimated to be 285 mmoles O2 m-2 of habitat for A. angulatus, 9.3 mmoles O2 m-2 of habitat for C. compressa and 15.3 mmoles O2 m-2 of habitat for Amphistegina lessonii. Pmax values for Amphistegina gibbosa fluctuated at the compensation point and did not indicate significant oxygen production. Pmax values for Amphistegina radiata failed to reach the compensation point and net oxygen production was not recorded.

Marine microbiome research is a rapidly expanding field of study, as scientists investigate the functions of microbial associations in eukaryotic organisms. Foraminifera are among the most abundant shelled organisms in the oceans, yet little is known of their associated microbiomes. This study investigated microbes associated with four species of Foraminifera that host three kinds of algal endosymbionts. The Order Miliolida, Family Soritidae, was represented by three species: Archaias angulatus and Cyclorbiculina compressa, which both host chlorophyte symbionts, and Sorites orbiculus, which hosts dinoflagellate symbionts. The fourth species, Amphistegina gibbosa, belongs to the Order Rotaliida and hosts diatom endosymbionts. Bacterial DNA extraction was attempted from 5−8 specimens per species followed by amplification and amplicon sequencing of the V4 variable region of the 16S rRNA gene. Three Ar. angulatus specimens shared 177 Operational Taxonomic Units (OTUs), and six C. compressa specimens shared 58 OTUs, of which 31 OTUs were found in all specimens of both species. Four S. orbiculus specimens shared 717 OTUs dominated by Proteobacteria, notably Amoebophilaceae. The three soritid species shared 26 OTUs, predominantly representing the bacterial families Rhodobacteraceae and Flavobacteriaceae. Since S. orbiculus shared 84% of the OTUs shared by Ar. angulatus and C. compressa, which host similar endosymbionts, phylogenetic relatedness of host taxa clearly had more influence on core microbiomes than the algal-symbiont taxon. The microbiomes of three normal-appearing and five partly-bleached specimens of Am. gibbosa varied widely, sharing only six OTUs, four of which represented Proteobacteria. All four species shared only four OTUs, three of which may have been contaminants. As the first known microbiome study to include western Atlantic/Caribbean benthic foraminifers that host algal endosymbionts, the results for Am. gibbosa revealed quite similar results to a recent study of the microbiome of Am. lobifera, a closely related Indo-Pacific taxon.