Effects of marine snow (transparent exopolymer particles, TEP) on coral recruits, Great Barrier Reef


Temporal Range: From 14-Dec-1999 To 06-Jan-2000

Resource Summary

The effects on the survivorship of recruits of the hard coral Acropora willisae of muddy coastal sediments, with and without enrichment by 'marine snow', were examined.

The experiment exposed four-week-old recruits to 4 treatments : muddy coastal sediments; transparent exopolymer particles (TEP); TEP-enriched muddy coastal sediments; and unfiltered sea water (control), for 43 h in aerated flow chambers. The recruits survival experiment was run five times, each time using eight new tiles (2 for each treatment). The position, number of polyps, and state (alive, i.e. healthy tissue visible; and dead, i.e. bare skeleton without tissue) of each recruit was mapped on the upper side of each tile before and after exposure using a dissecting microscope. Thirty-three percent of coral recruits died after 43-h exposure to TEP-enriched muddy coastal sediments (~14 mg cm-2 sediments enriched with 3.8 microg cm-2 gum xanthan equivalents [GX] TEP). In contrast, no or minimal mortality was observed in the other three treatments. Mortality increased to >80% when the amount of deposited TEP was almost tripled (10.9 microg cm-2 GX) and sediment increased by 50%. Thus, coral recruits survived short-term exposure to low levels of TEP and low levels of muddy sediments, but sediments enriched with TEP at concentrations recorded at some of the inshore stations proved to be detrimental.

Concentrations were measured in the central Great Barrier Reef in summer (the season of coral spawning and recruitment) for values of TEP (GX L-1), suspended solids, chlorophyll a, phaeopigments, and particulate phosphorus. Samples were taken 200m away from coral reefs ('Ship') during 2 voyages; and 1m above coral reefs ('Reef') on inshore (<10 km from the coast), midshelf (10-25 km) and offshore reefs (40 km or more) only during the first voyage. The station number, date, reef name, distance to coast (km), and number of samples taken were recorded.
Within <10 km off the coast, TEP concentrations were high (mean = 291 microg GX L-1, range = 152 - 791 microg GX L-1). Concentrations declined with increasing distance from the coast, and averaged 83 (+- 26 SE) microg GX L-1 around oceanic reefs >40 km off the coast.

To test the short-term effects of deposition of TEP-enriched muddy marine snow and sediments on the survival of recruits of hard corals (Cnidaria: Scleractinia), by exposing them to sediments with and without TEP-enrichment.

To determine what levels of TEP are likely to be encountered by coral recruits in inshore waters of the central Great Barrier Reef.

Stations were at the following locations: Alexandra Reef, Cape Tribulation, Daintree River, Double Island, Dunk Island, Fitzroy Island, Garioch Reef , Green Island, Hastings Reef, Low Island, Mission Bay, Mourilyan Inlet, Norman Reef, Port Douglas, Russel River, Snapper Island, Trinity Inlet, Upolu Reef, Yorkey's Knob.

One of the first studies to quantify TEP in tropical marine systems.

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Australian Institute of Marine Science (AIMS). (2009). Effects of marine snow (transparent exopolymer particles, TEP) on coral recruits, Great Barrier Reef, https://apps.aims.gov.au/metadata/view/bba10401-9102-499c-b3d2-a6bd641dd645, accessed 28-Jan-2021.