Marine Atlas: Maximizing Benefits for Solomon Islands

HOW MUCH DO WE REALLY KNOW? COLD WATER CORAL HABITATS While quite a lot is known about Solomon Islands’ inshore environment, some habitats are hard to explore and map. For example, although cold-water corals can be com- mon and important deep-sea species, little is known about their distribution and abundance in Solomon Islands’ waters. Their sensitivity to human impact and future climate change should be considered when assessing management options for deep-sea ecosystem conservation.

that FAO lists as potentially Vulnerable Ma- rine Ecosystems (FAO, 2009), and which are required under United Nations resolutions to be protected from deep-sea fishing. They are fully protected in some countries (e.g. New Zealand). Habitat suitability was highest along the major bathymetric features in the EEZ, with high predicted occurrence on seamounts to the south-east of the main islands and the island slopes of Santa Isabel, New Georgia and Choiseul, as well as the Santa Cruz Islands in the south. The distribution largely follows depth, with topography also a factor. These deeper slope and seamount features are shallower than many of the abyssal plains in the EEZ, with higher food availability. The steep topography provides hard rocky sub- strate which the corals need for attachment. 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 taxonomic grouping. The published figures do not indi- cate high suitability for these corals around Solomon Islands. The presence of cold-water corals can be an important indicator for managing human ac- tivities 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.

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, unveil- ing most features larger than 5 kilometres across (Sandwell, 2014). However, only 0.05 per cent of the ocean floor has been mapped to a high level of detail, meaning Solomon Islands’ waters undoubtedly hold a lot of secrets, including deepwater or cold-water corals. These corals have Corals are not restricted to shallow-water tropical seas. Cold-water corals are regard- ed 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, gorgoni- ans, bamboo corals), and family Stylasteridae (lace corals) (Roberts et al., 2009). They are widespread throughout the Pacific Ocean. At present, cold-water corals have no economic importance for Solomon Islands, though some species are used in jewel- lery 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.

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 shal- low-water corals, only a few cold-water species develop into traditional reefs. This is also why they are much harder to dis- cover and map than their shallow-water counterparts. Nevertheless, scientists have created habitat suitability models that use information on the physical environment to predict their distribution and provide an understanding of their ecological requirements. Cold-water corals are widely regarded as being susceptible to damage from human activities, such as direct effects from fishing, deep-sea mining and submarine commu- nication cables (see also chapters “Fishing in the dark” and “Underwater Wild West”), as well as more indirect impacts of pollu- tion and climate change (see also chapters “The dose makes the poison” and “Turning sour”). Many species of cold-water coral are structurally fragile, and hence easily broken. They can also be long-lived and slow-growing, meaning that any recovery from damage is slow. Therefore, the pres- ence of cold-water corals can be an impor- tant indicator of the need to manage human activities to avoid or minimize impacts on these deep-sea ecosystems. The presence of cold-water corals can therefore be used as an important indicator for managing human activities in order to avoid or mini- mize impacts on deep-sea ecosystems. For instance, octocorals are one of the groups

The bamboo coral Keratoisis grandiflora, which has been recorded in Solomon Islands’ waters.

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

OCEAN VALUES

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