FACT SHEET 17
SPONGES
• Sponges are colourful animals that are quite common on the reef. They are primitive (dating back more than 650 million years ago), sessile (cannot move) and filter-feeding animals that pump water through their bodies to filter out particles of food matter.
• The bright colours of sponges are a warning that they are toxic and can only be eaten by certain predators that have adapted to be able to eat them.
• Sponges are eaten by the endangered Hawksbill sea turtle as well as by nudibranchs (slugs with no shells), which feed on them in order to sequester (acquire) toxic chemicals which they use to protect themselves from predators.
• They are found growing almost everywhere (rocks, dead coral and rubble) and take on various shapes and sizes, often looking more like plants than animals.
• Their role on a coral reef is to clean the water of suspended matter.
• This role is very important as coral reefs need clear water in order for the sunlight to penetrate and allow the zooxanthellae to photosynthesize. • Humans collect sponges for use in homes (showers) and also to extract chemical compounds used to create medicines (especially against cancer).
• Reef Check Australia identify and monitor sponges. We record sponges (SP) and encrusting sponges (SPE). We record and monitor the amount of these sponges as large numbers of sponges may indicate high sewage levels, because there is lots of food for the sponges. If this is the case, sponges may out-compete hard corals and decrease the reef building capacity of that reef. Encrusting sponges tend to indicate sewage pollution.
Interesting Fact: A sponge the size of a tea cup can filter 5000 litres of water a day.
Further links:
• ReefED: http://www.reefed.edu.au/home/explorer/animals/marine_invertebrates/sponges
• Wikipedia: ttp://en.wikipedia.org/wiki/Sponge
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