Sedimentation stress in a scleractinian coral exposed to terrestrial and marine sediments relevant on the Great Barrier Reef

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Corals were exposed to 10 different sediment types at varying concentrations (33, 66, 100 and 133 mg DW cm-²) and exposure times (12, 20, 36, 44, 60 h) in laboratory and field experiments.Sediments were collected from the shores of 2 river estuaries (Herbert River, HR; Normanby River, NR), from 3 coral reefs (High Island, NS2; Wilkie Island, NS1; Otter Reef, OS) and one type comprised of aragonite sawdust (AR) from massive Porites sp. Three grain size classes of sediments were used: silts (S, Each of the 10 sediments (HR-S, HR-F, HR-M, OS-S, OS-F, OS-M, NR-S, NS1-S, NS2-S and AR-S) were characterised by 19 measured parameters. Physical parameters (PP) were: Grain size distribution (GSD, µm), Settling volume (SV, 25%, 50%, 75%), Settling rate (SR, % - 15 min, 1 h), Compaction (Comp, %), Relative light transmission (RLT, %). Organic and nutrient-related parameters (ONP) were: Ash-free dry weight (AFDW, %), Total organic carbon (TOC, %), Total nitrogen (TN, %), Total phosphorous (TP, %), Chlorophyll a (Chl a) and phaeophytin (Phaeo). Geochemical parameters (GCP, µmol g DW-¹) were: Aluminium, Barium, Copper, Iron, Manganese, Nickel, Lead, Zinc and Vanadium.Changes in the photosynthetic yield of the coral Montipora peltiformis was measured by pulse-amplitude modulated chlorophyll fluorometry (PAM) as proxy for photophysiological stress from exposure, and to determine rates of recovery.Tank experiments where conducted at the Australian Institute of Marine Science (AIMS) in December 2002, and in the field based during an expedition by the RV Lady Basten in January/February 2003. Responses by M. peltiformis to sediment on their surfaces were recorded: tentacle action, tissue swelling, mucus release, black spots, sediment accumulation, and percentage of colony surface freed from sediment.The field experiment was conducted at the front reef of Hannah Island in January 2003 at 4-6 m depth. The effects of HR-S, OS-S and AR-S sediment types (at a concentration of 66 mg DW cm-²) on each of 10 large colonies left for 24 h were recorded. The photosynthetic activity of each colony surfaces was then measured.
To investigate the effects on coral of 10 different types of sediments (of terrestrial, nearshore and offshore marine origin).The field experiment aimed to determine the extent of photophysiological stress from different sediment types at natural flow, wave and light conditions in colonies of Montipora peltiformis.

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Credit
Fabricius, Katharina E, Dr (Principal Investigator)