Marine Atlas: Maximizing Benefits for Kiribati

HOW MUCH DO WE REALLY KNOW? COLD WATER CORAL HABITATS Although cold-water corals can be common and important deep-sea species, little is known about their distribution and abundance in much of Kiribati’s waters, except for the PIPA. Their sensitivity to human impact and future climate change should be considered when assessing management options for deep-sea eco- system conservation.

of corals in the region. However, at present, owing to the limited data, habitat suitability modelling has been used to predict the likely occurrence of corals in the area. Habitat suitability was highest along the major island slopes in each sector of Kiriba- ti. The northern Line Islands, as well as the Gilbert group, had high habitat suitability close to the islands. There were also high predicted occurrences on seamounts in the Line Islands and Phoenix Islands EEZs. However, bathymetry is poorly known in this region; following recent work in the PIPA, new seamount features were located in 2017. The distribution shown in the maps largely reflects the depth of the seafloor, with topography also a factor. These deeper slope and seamount features are shallower than much of the abyssal plains, with higher food availability for the corals. The steep topography provides hard rocky substrate, which the corals need for attachment; it also elevates them from surrounding sediment for feeding. Although not presented, similar analyses have been carried out for five species of stony coral (order Scleractinia) (Davies and Guinotte, 2011). Depth, temperature, arag- onite saturation state and salinity were the key environmental drivers for this taxonom- ic grouping. The published figures do not indicate high suitability for these corals in Kiribati’s waters. Cold-water corals are widely regarded as being susceptible to damage from human activities, such as direct effects from fish- ing and deep-sea mining (with potential for cobalt-rich ferromanganese crust in Kiri- bati) as well as more indirect impacts from pollution and climate change. Many species of cold-water coral are structurally fragile,

The Moon or the sea? There is a common misconception that we know more about the surface of the Moon than the ocean floor and that 95 per cent of the ocean is unexplored. The chapter “Voyage to the bottom of the sea” showed that we actually know a lot about the ocean floor. The entire ocean floor has been mapped to a maximum resolution of around 5 kilometres, un- veiling most features larger than 5 kilo- metres across (Sandwell, 2014). How- ever, only 0.05 per cent of the ocean floor has been mapped to a high level of detail, meaning Kiribati’s waters un- doubtedly hold a lot of secrets, including deepwater or cold-water corals. These Corals are not restricted to shallow-water trop- ical seas. Deepwater or cold-water corals are regarded as occurring deeper than 50 metres, and include five taxa and over 3,300 more species than their better known tropical coral reef counterparts: order Scleractinia (hard, stony corals), order Zoanthidea (zoanthids, gold corals), order Antipatharia (black corals), subclass Octocorallia (soft corals, gorgonians, bamboo corals), and family Stylasteridae (lace corals) (Roberts et al., 2009). They are wide- spread throughout the Pacific Ocean. At present, cold-water corals have no economic importance for Kiribati, although some coral species have a value for jew- ellery production. However, many of them have been recognized as playing important ecological roles in the deep sea, since they can form large reef-like structures or have complex growth forms which in turn provide habitat for many associated invertebrate and fish species.

corals have a depth range extending from around 50 metres to beyond 2,000 metres deep, where water temperatures may be as cold as 4°C (see also chapter “Still waters run deep”). While there are nearly as many species of cold-water corals as shallow-water corals, only a few cold-water species develop into traditional reefs. This is also why they are much harder to discover and map than their shallow-water counterparts. Never- theless, scientists have created habitat suitability models that use information on the physical environment to predict their distribution and provide an understand- ing of their ecological requirements. The map shows the predicted suitability of habitat where octocoral species could occur. Octocorals are a highly diverse group, with soft corals, gorgonians, sea fans, sea whips, sea feathers, precious corals, pink coral, red coral, golden corals, bamboo corals, leather corals, horny corals and sea pens among their estimated 2,000-plus species (Roberts et al., 2009). Globally accessible data for offshore corals are sparse in many Pacif- ic Islands, including a large proportion of Kiribati’s waters. The Phoenix Islands area has been relatively well studied. A number of recent voyages by the National Oceanic and Atmospheric Administration (NOAA) vessel Okeanus Explorer (as part of the CAPSTONE programme) and the Schmidt Ocean Institute’s RV Falkor (Raineault et al., 2018) set out to survey new seamounts and have taken extensive video footage and several hundred samples of cold-water corals. When fully processed and analysed, these data will hugely boost the knowledge

The bamboo coral Keratoisis grandiflora, which has been recorded in Kiribati’s waters.

and hence easily broken. They can also be long-lived and slow growing, meaning that any recovery from damage, or changing environmental conditions, is slow. This could have long-term effects on deep-sea eco- systems. Octocorals are one of the groups that the Food and Agriculture Organization of the United Nations (FAO) lists as poten- tially Vulnerable Marine Ecosystems (FAO, 2009), and which are required under United Nations resolutions to be protected from deep-sea fishing. The presence of cold-water corals can be an important indicator for managing human activities to avoid or minimize impacts on deep-sea ecosystems. The habitat suitability map, although based on

presence–absence rather than abundance, gives an indication of which areas may need protection from disturbance of the sea floor or climate change.

MAXIMIZING BENEFITS FOR KIRIBATI

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