Investigations into the use of benthic foraminifera as indicators for water quality on the Great Barrier Reef (MTSRF Project 3.7.1)

Full description

Sediment samples for foraminiferan community analysis were collected from 20 reefs located between 13.5°S and 20.5°S within the Great Barrier Reef. Most of these reefs are inshore fringing reefs which can be grouped into three distinct geographical regions: eight reefs of the Whitsunday area (collected in August 2004), four reefs from Princess Charlotte Bay, and four from the Wet Tropic area (both collected in October 2004). Sediments were also collected from two midshelf reefs (Charity and Bait Reefs) in August 2004, and two outer shelf reefs (Hastings and Flynn Reefs) in January 2005.On each reef one location of the sheltered back reef and one on the more exposed front reef was chosen. At each location, two samples of > 50 g sediment were carefully scraped from the top 0.5 - 1 cm at 7 to 9 m depth. Samples were fixed in 100% ethanol.To determine sediment chemistry and granulometry parameters, additional sediment samples were collected at the same sites during collection of the foraminifera. In the Whitsunday area, additional sediment samples were collected in August 2005 and February 2006. The sediment samples were taken in triplicate from each location using mini-corers (cut-off 60 ml syringes); only the top 1 cm of sediment was used.Surveys in the Whitsunday region of the GBR included a more detailed study of foraminifera along an inshore-offshore transect.
Benthic foraminifera are established indicators for coral reef water quality conditions in Florida and the Caribbean Sea. The goal of this research was to contribute knowledge of the ecology of benthic coral reef foraminifera needed to test if these protozoans can be used as indicators for water quality on the GBR and potentially other reef systems in the Pacific region.
Reefs Surveyed1. Princess Charlotte Bay: McDonald Reef, Hay Island, Wilkie Island, Hannah Island 2. Wet Tropics: Fitzroy Island, High Island, Russel Island, Dunk Island3. Mid/Outer Shelf Reefs: Hastings Reef, Flynn Reef, Charity Reef, Bait Reef 4. Whitsunday Islands: Deloraine Island, Border Island, Whitsunday Island, Hook Island, Dent Island, Island, Lindeman Island, Repulse IslandOther datasets relate to this project, see separate metadata records.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: Statement: Samples for Foraminifera analysis:Sediments were washed with freshwater over a 63 µm sieve to remove small particles. Subsequently a minimum of 30 specimens were collected from the sediment of each sample in Bogarov dishes. Only intact specimens (defined as having less that 20% damage to their tests) were considered. Thus, although not all specimens may have been alive during the time of sampling, we assume the analysis includes only living and recently dead specimens. Samples were dried (>24 h, 60°C) and species composition of foraminifera determined in microfossil slides under a dissection microscope. The dry weight of the sediment and the foraminifera was determined to calculate foraminifera densities and to estimate the percent contribution of intact foraminifera to the total sediment.Samples for sediment analysis:Sediment grain size was determined by sieving dried sediments (ca. 20-30 g) over a graded set of sieves (63, 125, 250, 500, 1000 and 2000 µm) and measuring the dry weight of each fraction, including the Concentrations of sediment chlorophyll were determined using the methods described in "Sartory, D.P., Grobbelaar, J.U., 1984. Extraction of chlorophyll a from freshwater phytoplankton for spectrophotometric analysis. Hydrobiologia 114, 177-187", with adaptation to a Synergy HT (Bio-Tek) plate reader as described in "Uthicke, S., 2006. Photosynthetic efficiency and Rapid Light Curves of sediment biofilms along a water quality gradient in the Great Barrier Reef, Australia. Marine Ecology Progress Series 322, 61-73". The remaining sediment of each sample was dried and ground for carbon and nitrogen analysis. Total carbon was analysed on a Shimadzu analyser (TOC 5000A) and organic carbon was analysed on the same instrument after dissolving inorganic carbon with 1 M HCl. Concentrations of total nitrogen were determined with an ANTEK 9000NS analyser. Blanks were run with all samples and both carbon and nitrogen values were calibrated against Acetanilide (Ajax Chemicals) and an in-house standard sediment (Gould Island 1.2.C).Sediment parameters from most reefs were only determined during one occasion. However, organic carbon and nitrogen concentrations from samples in the Whitsunday Region were determined twice from samples collected in August 2004 and February 2006. Chlorophyll, C and N data fromthe Whitsunday Region in August 2004 have been summarised in the publication "Uthicke, S., 2006. Photosynthetic efficiency and Rapid Light Curves of sediment biofilms along a water quality gradient in the Great Barrier Reef, Australia. Marine Ecology Progress Series 322, 61-73."

Notes

Credit
Uthicke, Sven, Dr (Principal Investigator)