Marine Atlas: Maximizing Benefits for Solomon Islands

Around the main islands, photosynthetically available radiation tends to be higher on the south-eastern side of the islands compared to the north-western side. This is a reflec- tion of the local climatic conditions, with the predominantly easterly trade winds (see also chapter “Go with the flow”) resulting in less cloud cover over the leeward side of the larger islands (Solomon Islands Meteorologi- cal Service, 2016). There is also seasonal variation in photosyn- thetically available radiation in Solomon Is- lands. The greatest variation occurs around the main islands and in the very northern part of Solomon Islands’ waters, where pho- tosynthetically available radiation varies by

up to 20 per cent throughout the year. This is in part due to changes in atmospheric conditions, such as cloud cover. In Honiara, the average percentage of the sky covered by clouds experiences significant seasonal variation, with the cloudiest days occurring in December to March and the least cloudy days in July to September. The chlorophyll-a concentration in Solomon Islands’ waters is generally very low, with concentrations in its offshore waters less than 0.1 gram per m3 of seawater. Most of the tropical regions of the open oceans have similarly low chlorophyll-a concen- trations. In contrast, within temperate and arctic regions, these concentrations can

approach 1 gram per m3 of seawater. The shallow coastal regions of Solomon Islands have increased chlorophyll-a concentra- tions, with up to 2.5 grams per m3 of sea- water. Again, this is low compared to many coastal regions around the world, where chlorophyll-a concentrations can reach over 10 grams per m3 of seawater. The low concentrations of chlorophyll-a in Solomon Islands’ waters reflect the low availability of key nutrients. Compared to large continen- tal landmasses, with large river discharg- es that can carry nutrients into the sea, Solomon Islands is a small island nation

with comparatively small nutrient inputs into the marine environment. However, at the local or bay scale, nutrient inputs may still be significant. In the south-western tropical Pacific Ocean, strong seasonal and inter-annual variabili- ties in the chlorophyll-a concentration have been observed (Dupouy et al., 2004). Strong chlorophyll-a enrichments have been doc- umented around the Solomon Islands, and between New Caledonia and Vanuatu, with weaker enrichments found around Fiji or Tonga. The annual variation in chlorophyll-a around Solomon Islands is low, with var- iation up to 6 grams per m3 of seawater in some coastal areas.

Euphausia superba, phytoplankton from the Antarctic, is an example of the basis of the marine food chain.

PHOTOSYNTHETICALLY AVAILABLE RADIATION (Einstein m -2 d -1 )

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5°S

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Solomon Islands Provisional EEZ Boundary

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100

200 km

Copyright © MACBIO Map produced by GRID-Arendal Sources : Becker et al, 2009; Claus et al, 2016; NASA Goddard Space Flight Center, 2014; Smith and Sandwell, 1997.

10°S

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160°E

155°E

165°E

170°E

MAXIMIZING BENEFITS FOR SOLOMON ISLANDS

SUPPORTING VALUES

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