Epifaunal invertebrate assemblages associated with branching Pocilloporids in Moorea, French Polynesia

Sea anemone (Anthozoa, Actiniaria) diversity in Mo'orea (French Polynesia)

Sea anemones (Order Actiniaria) are a diverse group of marine invertebrates ubiquitous across marine ecosystems. Despite their wide distribution and success, a knowledge gap persists in our understanding of their diversity within tropical systems, owed to sampling bias of larger and more charismatic species overshadowing cryptic lineages. This study aims to delineate the sea anemone diversity in Mo'orea (French Polynesia) with the use of a dataset from the Mo'orea Biocode's "BioBlitz" initiative, which prioritized the sampling of more cryptic and understudied taxa. Implementing a target enrichment approach, we integrate 71 newly sequenced samples into an expansive phylogenetic framework and contextualize Mo'orea's diversity within global distribution patterns of sea anemones. Our analysis corroborates the presence of several previously documented sea anemones in French Polynesia and identifies for the first time the occurrence of members of genera Andvakia and Aiptasiomorpha. This research unveils the diverse sea anemone ecosystem in Mo'orea, spotlighting the area's ecological significance and emphasizing the need for continued exploration. Our methodology, encompassing a broad BLAST search coupled with phylogenetic analysis, proved to be a practical and effective approach for overcoming the limitations posed by the lack of comprehensive sequence data for sea anemones. We discuss the merits and limitations of current molecular methodologies and stress the importance of further research into lesser-studied marine organisms like sea anemones. Our work sets a precedent for future phylogenetic studies stemming from BioBlitz endeavors.

Pocillopora damicornis-associated macroinvertebrate responses to spatial gradients in the southern Mexican Pacific

We explicitly tested for spatial changes in Pocillopora damicornis-associated invertebrates across several spatial scales in the southern Mexican Pacific. Sorting of invertebrates from 40 coral heads along 882 km of the coast yielded 325 taxa, 283% more than any other Pocillopora spp. coral host study to date, but estimators signals that richness might be 17-39% larger than the current number. Permutation, ordination, and regression analysis indicate that the composition and abundance of invertebrates vary in response to the spatial distance among coral heads: high similarity and variation occur among coral heads within localities (<500 m), probably related to faunal homogenization, but progressively modest reduction in similarity and variation as spatial distance increases suggesting a weak role for environmental sorting across southern Mexican Pacific coral reefs. Future studies should explicitly explore spatial, environmental, and historical biogeography processes that regulate and maintain community structure and biodiversity on eastern Pacific reefs.

Functional and phylogenetic responses of motile cryptofauna to habitat degradation

Biodiversity of terrestrial and marine ecosystems, including coral reefs, is dominated by small, often cryptic, invertebrate taxa that play important roles in ecosystem structure and functioning. While cryptofauna community structure is determined by strong small-scale microhabitat associations, the extent to which ecological and environmental factors shape these communities are largely unknown, as is the relative importance of particular microhabitats in supporting reef trophodynamics from the bottom up. The goal of this study was to address these knowledge gaps, provided coral reefs are increasingly exposed to multiple disturbances and environmental gradients that influence habitat complexity, condition and ecosystem functioning. We compared the density, biomass, size range, phylogenetic diversity and functional roles of motile cryptofauna in Palau, Western Micronesia, among four coral-derived microhabitats representing various states of degradation (live coral [Acropora and Pocillopora], dead coral and coral rubble) from reefs along a gradient of effluent exposure. In total, 122 families across ten phyla were identified, dominated by the Arthropoda (Crustacea) and Mollusca. Cryptofauna biomass was greatest in live Pocillopora, while coral rubble contained the greatest density and diversity. Size ranges were broader in live corals than both dead coral and rubble. From a bottom-up perspective, effluent exposure had mixed effects on cryptic communities including a decline in total biomass in rubble. From a top-down perspective, cryptofauna were generally unaffected by predator biomass. Our data show that, as coral reef ecosystems continue to decline in response to more frequent and severe disturbances, habitats other than live coral may become increasingly important in supporting coral reef biodiversity and food webs.

Strahler Ordering Analyses on Branching Coral Canopies: Stylophora pistillata as a Case Study

The three-dimensional structural complexities generated by living sessile organisms, such as trees and branching corals, embrace distinct communities of dwelling organisms, many of which are adapted to specific niches within the structure. Thus, characterizing the build-up rules and the canopy compartments may clarify small-scale biodiversity patterns and rules for canopy constituents. While biodiversity within tree canopies is usually typified by the vertical axis that is delineated by its main compartments (understory, trunk, crown), traditional studies of coral canopy dwelling species are evaluated only by viewing the whole coral head as a single homogeneous geometric structure. Here, we employ the Strahler number of a mathematical tree for the numerical measurements of the coral’s canopy complexity. We use the branching Indo-Pacific coral species Stylophora pistillata as a model case, revealing five compartments in the whole coral canopy volume (Understory, Base, Middle, Up, and Bifurcation nods). Then, the coral’s dwellers’ diel distribution patterns were quantified and analyzed. We observed 114 natal colonies, containing 32 dwelling species (11 sessile), totaling 1019 individuals during day observations, and 1359 at night (1–41 individuals/colony). Biodiversity and abundance associated with Strahler numbers, diel richness, abundance, and patterns for compartmental distributions differed significantly between day/night. These results demonstrate that the coral-canopy Strahler number is an applicable new tool for assessing canopy landscapes and canopy associated species biodiversity, including the canopy-compartmental utilization by mobile organisms during day/night and young/adult behaviors.