News

Current knowledge on the reproduction of deep-sea corals

Deep-sea corals provide critical structure, habitat, shelter, spawning, and nursery sites for thousands of marine species and are thus major contributors to global marine biodiversity. At the same time, deep-sea corals are slow growing and extremely fragile, taking decades if not centuries to recover from disturbances such as fishing, ocean warming, and mining. With increasing pressure on deep sea resources, research on their reproduction and capacity to recover is even more imperative to adequately inform policies to protect these vulnerable organisms.

This review synthesises the current state of research on the reproduction of deep-sea corals. Although knowledge has expanded rapidly over recent decades, it found that less than 7% of all known species have any aspect of their reproduction reported in the scientific literature, highlighting significant gaps in this area of research. This is likely due to the unique logistical challenges of studying the deep sea. Further, lack of comparability of studies is a frequent issue highlighting the need for standard protocols and procedures in data collection and management. This is where global efforts such as the Ocean Biodiversity Information System (OBIS) play an important role.

Fig2

Figure 1. Total number of coral species with ranges extending below 100 m depth by taxonomic group and the number of species with published reproductive data (grey) and with no available reproductive data (hatched).

How OBIS was used in this study

OBIS, along with the World Register of Marine Species (WoRMS) and primary literature, were used in this study to find available depth range information for each species. Occurrence data were extracted from OBIS using the package robis in R. This data was then used to determine the total number of described azooxanthellate coral species living in depths below 100 m. The depth-related trends show that, across all coral taxa, most species have an upper depth range of 500 m or shallower, with very few species exhibiting depth ranges beginning below 1500 m.

Fig2

Figure 2. Known depth ranges of all coral species examined in this review (grey). Colored areas represent the depth ranges where reproductive information has been published across each taxa.

This research highlights that deep sea corals are vastly understudied and further studies on reproduction are needed to inform and support plans to manage and conserve populations of deep-sea corals worldwide.

Full publication available at:

Waller, R.G., Goode, S., Tracey, D. et al. 2023. A review of current knowledge on reproductive and larval processes of deep-sea corals. Marine Biology 170, 58.