Biology subjects

Pasella, M. M.

Publications and source records attributed to Pasella, M. M..

3 recordsLinked to original sources

bioRxiv2026

Light-harvesting strategies and competition drive niche partitioning among Ostreobium lineages in the spectral architecture of the coral reef

Ostreobium, a siphonous green alga capable of living inside of calcium carbonate substrates, including the skeletons of reef-building corals. This study investigates spectral niche preferences and physiological strategies of Ostreobium using community-wide experiments. We exposed natural Ostreobium communities from Porites lutea collected across shallow, mid, and deeper-water sites to three light conditions: far-red, blue, and white light, simulating healthy shallow-water corals, deeper water conditions, and bleached coral skeletons respectively. Using 16S rRNA metabarcoding and chlorophyll analysis, we assessed community changes and physiological responses over 16 weeks. We show significant variation in spectral preferences among Ostreobium OTUs, with clear evidence for both generalist and specialist strategies. Chlorophyll analysis showed photoacclimation responses through changes in pigment compositions. Our work shows that the spectral architecture of the reef plays a role in structuring Ostreobium communities, but the many mismatches between spectral preferences of OTUs and their observed presence in nature, suggests that inter-species competition is likely to be an even stronger contributor to community structure across the reefs microhabitats. We show that physiological heterogeneity within Ostreobium is strongly phylogenetically structured, and our results clearly highlight the importance of considering OTU-level differences when predicting community responses to environmental disturbances such as coral bleaching. While generalist OTUs dominate natural communities, these do poorly in incubations, and we hypothesise that white light specialists may become key players during coral bleaching events. Our work is a substantial advance in our understanding of Ostreobium ecology and provides a framework for interpreting future environmental sequencing data, offering insights into the functional roles of the different OTUs.

ecology↗

bioRxiv2021

Ten Ostreobium (Ulvophyceae) strains from Great Barrier Reef corals as a resource for algal endolith biology and genomics

Ostreobium is a genus of siphonous green algae that lives as an endolith in carbonate substrates under extremely limited light conditions and has recently been gaining attention due to its roles in reef carbonate budgets and its association with reef corals. Knowledge about this genus remains fairly limited due to the scarcity of strains available for physiological studies. Here, we report on 10 strains of Ostreobium isolated from coral skeletons from the Great Barrier Reef. Phenotypic diversity showed differences in the gross morphology and in few structures. Phylogenetic analyses of the tufA and rbcL put the strains in the context of the lineages identified previously through environmental sequencing. The chloroplast genomes of our strains are all around 80k bp in length and show that genome structure is highly conserved, with only a few insertions (some containing putative protein-coding genes) differing between the strains. The addition of these strains from the Great Barrier Reef to our toolkit will help develop Ostreobium as a model species for endolithic growth, low-light photosynthesis and coral-algal associations.

genetics↗

bioRxiv2020

Genomic adaptations to an endolithic lifestyle in the coral-associated alga Ostreobium

The green alga Ostreobium is an important coral holobiont member, playing key roles in skeletal decalcification and providing photosynthate to bleached corals that have lost their dinoflagellate endosymbionts. Ostreobium lives in the corals skeleton, a low-light environment with variable pH and O{square} availability. We present the Ostreobium nuclear genome and a metatranscriptomic analysis of healthy and bleached corals to improve our understanding of Ostreobiums adaptations to its extreme environment and its roles as a coral holobiont member. The Ostreobium genome has 10,663 predicted protein-coding genes and shows adaptations for life in low and variable light conditions and other stressors in the endolithic environment. This alga presents a rich repertoire of light-harvesting complex proteins but lacks many genes for photoprotection and photoreceptors. It also has a large arsenal of genes for oxidative stress response. An expansion of extracellular peptidases suggests that Ostreobium may supplement its energy needs by feeding on the organic skeletal matrix, and a diverse set of fermentation pathways allow it to live in the anoxic skeleton at night. Ostreobium depends on other holobiont members for vitamin B12, and our metatranscriptomes identify potential bacterial sources. Metatranscriptomes showed Ostreobium becoming a dominant agent of photosynthesis in bleached corals and provided evidence for variable responses among coral samples and different Ostreobium genotypes. Our work provides a comprehensive understanding of the adaptations of Ostreobium to its extreme environment and an important genomic resource to improve our comprehension of coral holobiont resilience, bleaching and recovery.

genomics↗