Linkages between coral assemblages and coral proxies of terrestrial exposure along a cross-shelf gradient on the southern Great Barrier Reef

S. Jupiter*, G. Roff, G. Marion, M. Henderson, V. Schrameyer, M. McCulloch, O. Hoegh-Guldberg

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    74 Citations (Scopus)

    Abstract

    Coral core records, combined with measurements of coral community structure, were used to assess the long-term impact of multiple environmental stressors on reef assemblages along an environmental gradient. Multiple proxies (luminescent lines, Ba/Ca, δ15N) that reflect different environmental conditions (freshwater discharge, sediment delivery to the nearshore, nutrient availability and transformations) were measured in Porites coral cores collected from nearshore reefs at increasing distance from the intensively agricultural region of Mackay (Queensland, Australia). The corals provide a record (1968-2002) of the frequency and intensity of exposure to terrestrial runoff and fertilizer-derived nitrogen and were used to assess how the present-day coral community composition may have been influenced by flood-related disturbance. Reefs closest to the mainland (5-32 km offshore) were characterized by low hard coral cover (≤10%), with no significant differences among locations. Distinct annual luminescent lines and elevated Ba/Ca values (4.98 ± 0.63 μmol mol-1; mean ± SD) in the most inshore corals (Round Top Island; 5 km offshore) indicated chronic, sub-annual exposure to freshwater and resuspended terrestrial sediment that may have historically prevented reef formation. By contrast, corals from Keswick Island (32 km offshore) indicated episodic, high-magnitude exposure to Pioneer River discharge during extreme flood events (e.g., 1974, 1991), with strongly luminescent lines and substantially enriched coral skeletal δ 15N (12-14‰). The reef assemblages at Keswick and St. Bees islands were categorically different from all other locations, with high fleshy macroalgal cover (80.1 ± 7.2% and 62.7 ± 7.1%, respective mean ± SE) overgrowing dead reef matrix. Coral records from Scawfell Island (51 km offshore) indicated little exposure to Pioneer catchment influence: all locations from Scawfell and further offshore had total hard and soft coral cover comparable to largely undisturbed nearshore to middle shelf reefs of the southern Great Barrier Reef.

    Original languageEnglish
    Pages (from-to)887-903
    Number of pages17
    JournalCoral Reefs
    Volume27
    Issue number4
    DOIs
    Publication statusPublished - Dec 2008

    Fingerprint

    Dive into the research topics of 'Linkages between coral assemblages and coral proxies of terrestrial exposure along a cross-shelf gradient on the southern Great Barrier Reef'. Together they form a unique fingerprint.

    Cite this