Formation of agglutinated cysts by the foraminiferan Sphaeroidina bulloides on the Porcupine Abyssal Plain (NE Atlantic)

Benthic foraminiferal species sometimes produce a covering made of sediment and detrital material around their tests (shells). These sedimentary envelopes, termed ‘cysts’, have been observed in a number of species, from organic-walled and agglutinated to calcareous (e.g., Linke and Lutze 1993; Cedhagen 1996; Gross 2000, 2002; Gooday and Hughes 2002; Heinz et al. 2005). However, almost all published records of this phenomenon originate from coastal or bathyal settings, and there are very few examples from abyssal depths, i.e. deeper than 3500 m. During the analysis of Megacorer samples (25.5 cm2 surface area, formalin-buffered, 0–1 cm sediment horizon, >150 ?m fraction) collected in the area of the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the northeast Atlantic (49°N 16.5°W, 4850 m water depth), we observed benthic foraminifera that had created partial or complete muddy coatings. Most belonged to Sphaeroidina bulloides d’Orbigny, 1826 (Fig. 1), and a few to Melonis barleeanus (Williamson, 1858). The S. bulloides cysts occasionally incorporated juvenile planktonic foraminiferal tests (<50 ?m), and always included one or more flexible agglutinated tubes (20–35 ?m wide, 140–400 ?m long) that extended out of the main structure (Fig. 1a–e). There was no evidence of the presence within the cysts of microscopic organisms, comparable to the ciliates and nematodes observed by Linke and Lutze (1993) inside the cysts of Elphidium incertum

Benthic foraminiferal responses to mesoscale environmental heterogeneity at the Porcupine Abyssal Plain, NE Atlantic

Although our knowledge on the vast deep-sea biome has increased in recent decades, we still have a poor understanding of the processes regulating deep-sea diversity and assemblage composition, as well as their underlying natural variability in space and time. In the face of unprecedented anthropogenic impact on this environment, addressing this knowledge gap remains of paramount importance. In this thesis I focus on the effect of mesoscale (10s of kilometres) spatial heterogeneity, in the form of abyssal hills and surrounding abyssal plains, on benthic communities and specifically on foraminiferal faunas living at abyssal depths in the northeast Atlantic. ‘Live’ (Rose-Bengal-stained) and dead benthic foraminiferal assemblages, including rarely-studied soft-walled monothalamous species, were analysed based on a total of 16 Megacorer samples (0.25 cm2 surface area, 0-1 sediment horizon, &gt;150 ?m sieve fraction) from five sites within the area of the Porcupine Abyssal Plain Sustained Observatory (PAP-SO, NE Atlantic, ~4850 m water depth). Three sites were located on the tops of small abyssal hills (~200-500 m elevation) and two on the adjacent abyssal plain. The main results of this analysis include the following. (1) Description of new morphotypes of poorly known primitive benthic foraminifera associated with (i.e. sessile on) planktonic foraminiferal shells and mineral grains. Some of these forms were more common on the hills, while others were more common on the plain. (2) Agglutinated foraminifera selected particles of different sizes on the hills compared to the plain, which affected their test morphometry and visual appearance. Distinct hydrodynamic conditions, and consequently distinct sediment granulometric characteristics between the two settings (hills, plain) resulted in foraminifera on the hills having more coarsely agglutinating tests. This information could be useful in palaeoecological interpretations of the fossil record. (3) Live benthic foraminiferal assemblages were significantly influenced by seafloor topography. Abyssal hills had a higher species density compared to the plain, supported a distinct fauna, and therefore tended to increase regional diversity. Enhanced bottom-water flow on hills, which affects organic matter supply and local sedimentology, were proposed to be responsible for these differences. (4) During the transition from live to dead benthic foraminiferal faunas there was a significant loss of delicate agglutinated and organic-walled forms. Unlike ‘live’ assemblages, the composition of the dead assemblages was very similar in hill and plain settings, suggesting that it would not be possible for paleoceanographers to differentiate between fossil foraminiferal faunas originating from these topographically contrasting settings. In conclusion, this study highlighted the significant effect of hills on agglutination patterns, assemblage composition and regional diversity of living benthic foraminifera. Since abyssal hills are one of the most common landforms on Earth, their presence may substantially enhance abyssal biodiversity, with important implications of deep-sea ecosystem functioning

Abyssal hills: influence of topography on benthic foraminiferal assemblages

Abyssal plains, often thought of as vast flat areas, encompass a variety of terrains including abyssal hills, features that constitute the single largest landscape type on Earth. The potential influence on deep-sea benthic faunas of mesoscale habitat complexity arising from the presence of abyssal hills is still poorly understood. To address this issue we focus on benthic foraminifera (testate protists) in the >150-?m fraction of Megacorer samples (0–1 cm layer) collected at five different sites in the area of the Porcupine Abyssal Plain Sustained Observatory (NE Atlantic, 4850 m water depth). Three sites are located on the tops of small abyssal hills (200–500 m elevation) and two on the adjacent abyssal plain. We examined benthic foraminiferal assemblage characteristics (standing stock, diversity, composition) in relation to seafloor topography (hills vs. plain). Density and rarefied diversity were not significantly different between the hills and the plain. Nevertheless, hills do support a higher species density (i.e. species per unit area), a distinct fauna, and act to increase the regional species pool. Topographically enhanced bottom-water flows that influence food availability and sediment type are suggested as the most likely mechanisms responsible for these differences. Our findings highlight the potential importance of mesoscale heterogeneity introduced by relatively modest topography in regulating abyssal foraminiferal diversity. Given the predominance of abyssal hill terrain in the global ocean, we suggest the need to include faunal data from abyssal hills in assessments of abyssal ecology

Stakeholder-derived recommendations and actions to support deep-reef conservation in the Western Indian Ocean

Deep reefs below 30mprovide essential ecosystem services for ocean health and human well-being such as food security and climate change resilience. Yet, deep reefs remain poorly researched and largely unprotected, including in the Western Indian Ocean (WIO). Here, we assessed current conservation approaches in the WIO focusing on deep reefs, using a combination of online surveys and semi-structured interviews. Results indicated that deep-reef data are sparse and commonly stemming from non-peer-reviewed or non-publicly available sources, and are often not used to inform conservation of WIO marine protected areas

Relationship between ‘live’ and dead benthic foraminiferal assemblages in the abyssal NE Atlantic

Dead foraminiferal assemblages within the sediment mixed layer provide an integrated, time-averaged view of the foraminiferal fauna, while the relationship between dead and live assemblages reflects the population dynamics of different species together with taphonomic processes operating over the last few hundred years. Here, we analysed four samples for ‘live’ (Rose-Bengal-stained) and dead benthic foraminifera (0–1 cm sediment layer, >150 ?m) from four sites in the area of the Porcupine Abyssal Plain Sustained Observatory (PAP-SO; NE Atlantic, 4850 m water depth). Two sites were located on abyssal hills and two on the adjacent abyssal plain. Our results indicate that the transition from live to dead benthic foraminiferal assemblages involved a dramatic loss of delicate agglutinated and organic-walled tests (e.g. Lagenammina, Nodellum, Reophax) with poor preservation potential, and to a lesser extent that of some relatively fragile calcareous tests (mostly miliolids), possibly a result of dissolution. Other processes, such as the transport of tests by bottom currents and predation, are unlikely to have substantially altered the composition of dead faunas. Positive live to dead ratios suggest that some species (notably Epistominella exigua and Bolivina spathulata) may have responded to recent phytodetritus input. Although the composition of live assemblages seemed to be influenced by seafloor topography (abyssal hills vs. plain), no such relation was found for dead assemblages. We suggest that PAP-SO fossil assemblages are likely to be comparable across topographically contrasting sites, and dominated by calcareous and some robust agglutinated forms with calcitic cement (e.g. Eggerella)

Low connectivity between shallow, mesophotic and rariphotic zone benthos

© 2019 Massachussetts Medical Society. All rights reserved. Worldwide coral reefs face catastrophic damage due to a series of anthropogenic stressors. Investigating how coral reefs ecosystems are connected, in particular across depth, will help us understand if deeper reefs harbour distinct communities. Here, we explore changes in benthic community structure across 15-300 m depths using technical divers and submersibles around Bermuda. We report high levels of floral and faunal differentiation across depth, with distinct assemblages occupying each depth surveyed, except 200-300 m, corresponding to the lower rariphotic zone. Community turnover was highest at the boundary depths of mesophotic coral ecosystems (30-150 m) driven largely by taxonomic turnover and to a lesser degree by ordered species loss (nestedness). Our work highlights the biologically unique nature of benthic communities in the mesophotic and rariphotic zones, and their limited connectivity to shallow reefs, thus emphasizing the need to manage and protect deeper reefs as distinct entities

Deep Reef Benthos of Bermuda: Field Identification Guide

Deep Reef Benthos of Bermuda builds on the video and imagery data collected during Nekton’s Mission – the XL Catlin Deep Ocean Survey - and provides a photographic guide for the visual identification of many of the corals, marine plants and other common invertebrates that inhabit Bermuda’s outer deep reefs.This guide is designed to aid marine biologists, divers and naturalists with the identification of organisms as seen in underwater footage or live in the field.</div

Hybrid conferences: opportunities, challenges and ways forward

Hybrid conferences are in-person events that have an online component. This type of meeting format was rare before the COVID-19 pandemic, but started to become more common recently given the asynchronous global progression of the pandemic, the uneven access to vaccines and different travel regulations among countries that led to a large proportion of participants being unable to attend conferences in person. Here we report the organization of a middle-sized (581 participants: 159 onsite, 422 online) international hybrid conference that took place in France in September 2021. We highlight particular organizational challenges inherent to this relatively new type of meeting format. Furthermore, we surveyed both in-person and online participants to better understand their conference experience and to propose improvements based on the feedback received. Finally, we compare the advantages and disadvantages of three types of conferences (onsite-only, online-only and hybrid) and suggest that hybrid events should be favored in the future because they offer the most flexibility to participants. We conclude by proposing suggestions and ways forward to maximize accessibility and inclusivity of hybrid conferences. Our study brings novel insights on the challenges and opportunities created by hybrid conferences, by reporting not only the organizing committee experience but also by considering the participants’ perspective

Moving conferences online: lessons learned from an international virtual meeting

We consider the opportunities and challenges associated with organizing a conference online, using a case study of a medium-sized (approx. 400 participants) international conference held virtually in August 2020. In addition, we present quantifiable evidence of the participants’ experience using the results from an online post-conference questionnaire. Although the virtual meeting was not able to replicate the in-person experience in some aspects (e.g. less engagement between participants) the overwhelming majority of respondents found the meeting an enjoyable experience and would join similar events again. Notably, there was a strong desire for future inperson meetings to have at least some online component. Online attendance by lower-income researchers was higher compared with a past, similarthemed in-person meeting held in a high-income nation, but comparable to one held in an upper-middle-income nation. This indicates that online conferences are not a panacea for diversity and inclusivity, and that holding in-person meetings in developing economies can be at least as effective. Given that it is now relatively easy to stream contents of meetings online using low-cost methods, there are clear benefits in making all presented content accessible online, as well as organizing online networking events for those unable to attend in person

A multidisciplinary approach for generating globally consistent data on mesophotic, deep-pelagic, and bathyal biological communities

Approaches to measuring marine biological parameters remain almost as diverse as the researchers who measure them. However, understanding the patterns of diversity in ocean life over different temporal and geographic scales requires consistent data and information on the potential environmental drivers. As a group of marine scientists from different disciplines, we suggest a formalized, consistent framework of 20 biological, chemical, physical, and socioeconomic parameters that we consider the most important for describing environmental and biological variability. We call our proposed framework the General Ocean Survey and Sampling Iterative Protocol (GOSSIP). We hope that this framework will establish a consistent approach to data collection, enabling further collaboration between marine scientists from different disciplines to advance knowledge of the ocean (deep-sea and mesophotic coral ecosystems)