Cryptofaunal communities are influenced by benthic cover and fish abundance in a large Caribbean coral reef system

Small-sized invertebrates inhabiting hard substrates in coral reefs (a.k.a. cryptofauna) contribute substantially to reef biodiversity, but their patterns of distribution and ecological controls are poorly understood. Here, we characterized the cryptofauna community and explored “bottom-up” and “top-down” controls by benthic cover and fish abundance, respectively. We sampled the cryptofauna inhabiting the reef terrace from 13 sites along 200 km in Jardines de la Reina (Cuba), a well-preserved and protected area in the Caribbean. We counted 23,959 invertebrates of 14 higher taxa, being the most abundant Copepoda (54%), Nematoda (21%), Mollusca (7%), Ostracoda (5%), Polychaeta (5%), and Amphipoda (3%). Richness, abundance, and community structure varied across the reefs without any geographical gradient of distribution. One-third of the variance occurred at site scale (~ 10 km), and half occurred at quadrat scale (~ 1 m). Algal cover promoted cryptofauna richness and abundance likely providing substrate and food, while live coral cover negatively influenced nematode abundances, potentially due to coral defenses. Relationships between cryptofauna and reef fishes were also present, with invertivores and herbivores negatively affecting cryptofauna abundance likely due to direct or indirect predation pressures. This research highlights the important roles of bottom-up and top-down controls, by algal/coral cover and fishes, respectively, on cryptofauna and in extension to coral reef biodiversity. Current threats by climate change are expected to alter these controls on cryptofauna resulting in changes to diversity, trophodynamics and energy flows of coral reefs.

Settlement patterns and temporal successions of coral reef cryptic communities affect diversity assessments using autonomous reef monitoring structures (ARMS)

Autonomous Reef Monitoring Structures (ARMS) are used worldwide to assess cryptic diversity, especially on coral reefs. They were developed as standardised tools, yet conditions of deployment, such as immersion duration and/or deployment and retrieval seasons, vary among studies. Here we studied temporal and seasonal variability in coral reef cryptic communities sampled with 15 ARMS on a single coral reef slope site at Reunion Island, Southwest Indian Ocean. Settlement patterns and temporal succession of Eukaryote communities were investigated across three immersion times (6 months, 1 year, 2 years), two immersion seasons (hot vs. cool) and three fractions (500-2000 μm, 106-500 μm, sessile) using two genetic markers (18S, COI). Both markers detected different taxa with different resolutions, but broadly similar patterns of community composition and structure. While OTU diversity of communities did not change with immersion time and season, these parameters significantly affected community structure and composition. Our results showed a decrease of the similarity of ARMS communities with duration of immersion, and a strong temporal turnover of species with only a small proportion of the diversity persisting over time. The small proportion of OTUs assigned at phylum level highlights the uniqueness of the Mascarene cryptobiome.

Marine Debris Harbor Unique, yet Functionally Similar Cryptofauna Communities

Human-made debris is entering the ocean at alarming rates. These artificial structures are becoming habitats for small marine taxa known as cryptofauna. Cryptofauna are among the most essential reef taxa; however, little is known about these organisms, let alone their fate considering degrading coral reefs and increasing anthropogenic disturbance. The current study explores differences in naturally occurring cryptofauna biodiversity compared to those inhabiting benthic marine debris. To explore this difference, we measured invertebrate diversity from autonomous reef monitoring structures (ARMS) located on patch reefs along the middle Florida Keys reef tract. ARMS were used as a proxy for natural structure to compare to marine debris removed from five reef locations. Plastic debris was the most abundant of all the debris material collected. Wood and concrete were identified as covariates since they are sourced from wooden lobster traps. Taxa diversity varied significantly between ARMS and debris, indicating that each structural unit contained significantly different and diverse communities. The most influential taxa identified included commensal shrimps, hermit crabs, brittle stars, segmented worms, and several families of crabs. Additionally, while functional richness increased with taxa richness for ARMS communities, debris communities showed decreasing functional richness and high functional similarity, suggesting a specialization of debris-specific taxa. Overall, these data assist in better understanding of the marine community ecology surrounding anthropogenic marine debris for future debris removal and management practices for comprehensive reef health.

Seq' and ARMS shall find: DNA (meta)barcoding of Autonomous Reef Monitoring Structures across the tree of life uncovers hidden cryptobiome of tropical urban coral reefs

Coral reefs are among the richest marine ecosystems on Earth, but there remains much diversity hidden within cavities of complex reef structures awaiting discovery. While the abundance of corals and other macroinvertebrates are known to influence the diversity of other reef-associated organisms, much remains unknown on the drivers of cryptobenthic diversity. A combination of standardized sampling with 12 units of the Autonomous Reef Monitoring Structure (ARMS) and high-throughput sequencing was utilized to uncover reef cryptobiome diversity across the equatorial reefs in Singapore. DNA barcoding and metabarcoding of mitochondrial cytochrome c oxidase subunit I, nuclear 18S and bacterial 16S rRNA genes revealed the taxonomic composition of the reef cryptobiome, comprising 15,356 microbial ASVs from over 50 bacterial phyla, and 971 MOTUs across 15 metazoan and 19 non-metazoan eukaryote phyla. Environmental factors across different sites were tested for relationships with ARMS diversity. Differences among reefs in diversity patterns of metazoans and other eukaryotes, but not microbial communities, were associated with biotic (coral cover) and abiotic (distance, temperature and sediment) environmental variables. In particular, ARMS deployed at reefs with higher coral cover had greater metazoan diversity and encrusting plate cover, with larger-sized non-coral invertebrates influencing spatial patterns among sites. Our study showed that DNA barcoding and metabarcoding of ARMS constitute a valuable tool for quantifying cryptobenthic diversity patterns and can provide critical information for the effective management of coral reef ecosystems.

Rediscovering Monogenoids (Platyhelminthes) Parasitizing Pomacentrid and Chaetodontid Fishes from Cayo Arcas Reef, Gulf of Mexico

During a research of gill ectoparasites on damselfishes (Pomacentridae) and butterflyfishes (Chaetodontidae) from the Cayo Arcas reef in the Campeche Bank (Gulf of Mexico), the following monogenoids (Platyhelminthes) were found: Paraeuryhaliotrema pomacentris n. gen., n. sp. (Dactylogyridae) on beaugregory Stegastes xanthurus (Poey, 1860) (Pomacentridae) that is characterized, in part, by possessing a haptor armed with a dorsal, ventral anchor-bar complexes, seven pairs of similar hooks; two pairs of eyespots; overlapping gonads; a copulatory complex composed of a male copulatory organ (MCO) and an accessory piece; MCO tubular with a bulbous base from which arises a coiled shaft in the clockwise direction; and a dextral vaginal pore; Neohaliotrema variabilis n. sp. on bicolor damselfish Stegastes partitus (Poey, 1868) (type host), beaugregory Stegastes xanthurus (Poey, 1860) and beaugregory Stegastes leucostictus (Müller & Troschel, 1848); Neohaliotrema manubrium n. sp., Neohaliotrema aliamanubrium n. sp. and Neohaliotrema bifidum n. sp., Neohaliotrema bychowskii Zhukov, 1976 and Neohaliotrema macracanthum Zhukov, 1976 on Sergeant-major Abudefduf saxatilis (Linnaeus, 1758) (Pomacentridae); Neohaliotrema similium n. sp. on S. xanthurus; Haliotrema brevicirrus Zhukov 1976 on spotfin butterflyfish Chaetodon ocellatus Bloch 1787 (Chaetodontidae); Microcotyle multilineatus n. sp. (Microcotylidae) on brown chromis Chromis multilineata (Guichenot 1853) (Pomacentridae). The new species are described and illustrated; new illustrations and measurements of the haptoral structures, and new redescription and illustrations are provided for N. bychowskii, N. macracanthum and H. brevicirrus, respectively. The present study represents the first knowledge about ectoparasitic monogenoids of fishes in the Cayo Arcas reef from the Gulf of Mexico.