Holocene foraminifera from the reefs surrounding Viti Levu, Fiji Islands

a test of the FORAM Index

Luke C. Strotz, Glenn A. Brock

    Research output: Contribution to journalMeeting abstract

    Abstract

    The FORAM Index is a technique developed by Hallock et al.(2003, Environmental Monitoring and Assessment 81(1-3):221-238) that uses foraminifera, particularly the “larger” foraminifera, those that possess endosymbiotic algae, to assess water quality in coral reef environments. However, development of the technique took place largely in the Caribbean, and Hallock et al.(2003)admit that more testing in Indo-Pacific reef environments is needed. With an aim to determine whether the FORAM Index can be utilised to assess the health of reefs outside of the Caribbean, particularly in the south-west Pacific region, coral reefs surrounding the main island of Fiji, Viti Levu, were systematically sampled for foraminifera. Viti Levu was chosen as reefs surrounding the island are in clear decline due to anthropogenic pollutants and activities (Zann, 1994. Marine Pollution Bulletin, 29:52-61)and the coral and foraminiferal fauna that inhabits the region is typical of reefs throughout the south-west Pacific. Samples were collected from six transects surrounding Viti Levu,and from a series of spot localities to the north-west and south-east of the island. A total of forty-nine species of foraminifera were recovered from collected samples. The faunal assemblage is typical of reef faunas throughout the south Pacific, composed of predominantly miliolid and rotaliid taxa, with agglutinated taxa inferior in both diversity and abundance. FORAM Index values calculated for the collected samples range from a high of 9.75 to a low of 3, but only in exceptional circumstances do calculated values fall below the required value of 4 that indicates water quality conducive to coral reef growth (Hallock et al., 2003). The calculated values obtained suggest that water quality in much of the region surrounding Viti Levu is suitable for coral reef growth and that, therefore, the corals surrounding the island should be unaffected by anthropogenic influences. However, field observations show an inverse relationship to that expected, with a decrease in hermatypic coral cover and diversity coinciding with an increase in calculated FORAM Index values and vice versa. All decreases in coral cover observed directly correlate with an increase in macro-algal abundance. It is possible that, rather than reflecting coral diversity and abundance, as should be the case if the index functions as intended, results obtained from Fiji appear to be more influenced by macro-algae cover. This could possibly be attributed to the fact that many “larger” foraminifera live epiphytically on the surface of macro-algae and thus, increased macro-algae abundance, often the direct result of anthropogenically driven eutrophication, will result in increased absolute abundance of these taxa, thereby skewing the FORAM Index value obtained.
    Original languageEnglish
    Pages (from-to)305-306
    Number of pages2
    JournalAnuário do Instituto de Geociências
    Volume29
    Issue number1
    Publication statusPublished - 2006
    EventInternational Symposium on Foraminifera (FORAMS 2006) - Natal, Brazil
    Duration: 10 Sep 200615 Sep 2006

    Keywords

    • water quality assessment
    • coral reef environments

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