Submersibles Greatly Enhance Research on the Diversity of Deep-Reef Fishes in the Greater Caribbean

Abstract

Understanding the diversity and ecology of deep-reef fishes is challenging. Due to intensive and widely dispersed sampling, the Greater Caribbean (GC) fauna of species found on shallow reefs is much better characterized than the fauna of deep-reef species restricted to mesophotic (40–130 m) and rariphotic (130–300 m) depths. Our knowledge about deep-reef fishes is based on ship-board sampling and the recent use of rebreather diving, remotely operated vehicles (ROVs), baited remote underwater videos, and crewed submersibles. Submersible research on GC deep-reef fishes began in the 1960s and has flourished over the last decade through research by the Smithsonian Institution’s Deep Reef Observation Project (DROP). Here we quantify the contribution of submersible research, particularly the surge by DROP, to our understanding of the diversity of the deep-reef fish fauna of the GC. We compared shallow- and deep-reef fish faunas of three GC sites subjected to DROP research to faunas of three sites without such research. DROP increased the size of the deep faunas at three islands ∼9-fold, and they have deep-reef faunas ∼2–4 times the size of those of the other three sites. Those deep-reef faunas have high proportions of small cryptobenthic fishes, which also represent a major component of shallow faunas. That research increased the rate of discovery (collection) of new species of deep-reef fishes ∼6-fold and accounts for 31% of the deep-reef species first discovered within the GC. Substantial numbers of new species at each of the three DROP islands were not found at the other two. This indicates that other parts of the GC likely harbor many undetected deep-reef fishes, and that the size of the deep-reef fauna of the GC is significantly underestimated. These results show that small research submersibles are versatile, highly productive tools for deep-reef studies. They allow long-duration dives at any depth, while offering unparalleled views of their surroundings to study the ecology of deep-reef fishes (e.g., DROP’s definition of the rariphotic assemblage from fish depth distributions). Submersibles can efficiently collect reef fishes of a broad range of taxa, ecotypes and sizes, leading to a more comprehensive understanding of the regional GC deep-reef fish fauna.

An updated, illustrated inventory of the marine fishes of the US Virgin Islands

“…At both USVI sites the deep-reef species represent only 4.2-5% of the entire local reef-fish fauna, i.e., ~ 1/3 of the percentage for the GC regional fauna (Robertson et al 2022). In contrast, when intensive submersible collecting and observations have been aimed specifically at assessing the diversity of deep-reef fish faunas, such as has occurred at other Caribbean islands (Curacao, Roatan and Sint Eustatius), the inventory of deepreef species at individual islands has increased ~ 9 fold, with such species representing 16% of the entire (shallow plus deep) reef-fish fauna at the most intensively sampled island (Robertson et al 2022), i.e., more than three times the level at each USVI. Similar sampling at both USVI undoubtedly will increase the absolute and relative sizes of their deep-reef faunas.…”

“…Abundance of ecotypes of reef-associated bony fishes in the Greater Caribbean and the USVI. Data for the region pattern are fromRobertson and Tornabene (2021), for St. Croix are fromRobertson et al (2022), and for St. John-Thomas are in File S5. Bold percentages indicate whether the value(s) for either the region or the USVI islands were > 5% higher than the value(s) for the other group in each case.…”

Description of the First Species of Polylepion (Teleostei: Labridae) from the Atlantic Ocean with Analysis of Evolutionary Relationships of the New Species

“…Baldwin et al (2018) presented a classification of reef-fish faunal zones at Curaçao that comprises the altiphotic (0 to ∼40 m), mesophotic (∼40 to ∼130 m), and rariphotic (∼130 to at least 300 m). The new species joins a growing list of new Caribbean deep-reef fish species discovered at mesophotic and rariphotic depths and collected with the aid of robotic arms and fish anesthetics using human-occupied submersibles (Robertson et al, 2022). Including the new species of Polylepion , exploration of the Caribbean deep-reef fish fauna by the Smithsonian's Deep Reef Observation Project (DROP) has resulted in the description of one new genus and more than 25 new species, with additional new species yet to be described (e.g., Tornabene and Baldwin, 2019, and references therein; McFarland et al, 2020; Tornabene et al, 2023).…”

On-demand quantum light sources for underwater communications

“…While they are exceptional over ultra-long range underwater communications [5,6], they are also highly insecure, omni-directional and suffer from very low data rates, especially over these distances [7,8]. For many underwater communication needs such as exploration, research, short range submersibles or military operations [9][10][11], the separation between the sender and receiver is often a far shorter distance than required for the use of acoustic waves. In these instances communication using standard, transversal electromagnetic waves would be far more beneficial for their increased data transmission rates and high level of security [12,13].…”