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Effects of Global Warming. Early signals?. It is estimated that in 1998 one sixth of the world’s coral was lost due to bleaching. Were these events an early sign of the effects of global warming?
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Early signals? It is estimated that in 1998 one sixth of the world’s coral was lost due to bleaching. Were these events an early sign of the effects of global warming? A coral polyp is a tubular animal with a central mouth surrounded by tentacles. The polyps secrete an external skeleton of calcium carbonate for protection; this builds the coral reef. Mass coral bleaching is primarily caused by sea temperatures becoming too warm for the algae that live within the coral and help it feed. The algae give the coral its colour, so when the algae are lost, the coral loses its bright colours and the white calcium carbonate skeleton of the coral becomes visible.
The algae provide the coral with energy and nutrients from photosynthesis; in return, the coral provides the algae with ammonia and phosphates. Without the algae the coral will eventually die from starvation, disrupting the food chain and reducing the biodiversity of the reef. Coral bleaching is widely recognised as an indicator of climate change. The bleaching and death of coral has been attributed by many people to elevated sea temperatures which occur as a consequence of global warming.
During 1998, satellite images of the Indian Ocean showed higher than normal sea surface temperatures (Figure 1) and some scientists think that this explains why the coral bleaching occurred in these regions.
Phenology Phenology is the study of the timing of recurring natural phenomena especially in relation to climate. It involves recording events such as when you heard the first cuckoo of the year or first saw the hawthorn come into blossom. Long-term datasets can be examined for any trends that could indicate changes in the timing of life cycles that may be related to climate change.
The Environmental Change Network (ECN) website is available through the weblinks for this activity. This site shows the mean flight date of the common footman moth and orange tip butterfly, indicating the timing in the year when these insects are active. The site uses online data from continuously updated ECN data setsto produce graphs
The effect of temperature on thehatching success of brine shrimps Brine shrimps Brine shrimps are small, salt water crustaceans; the adults are about 8 mm in length. They are relatively easy to keep in the laboratory and will produce dormant egg cysts that hatch to produce young shrimp larvae.
Procedure • Decide on a range of temperatures from 5 °C to 35 °C to be tested. • Place 2 g of sea salt into a 100 cm 3 beaker. • Add 100 cm 3 of dechlorinated water and stir until the salt completely dissolves. • Label the beaker with the temperature at which it will be incubated. • Place a tiny pinch of egg cysts onto a large sheet of white paper. • Wet the piece of graph paper using a few drops of salt water. Dab the paper onto the white sheet to pick up approximately 40 eggs. This will look like a tiny shake of pepper. Use a magnifying glass to count the eggs. Cut the graph paper so that there are exactly 40 eggs. • Put the paper with the 40 eggs into the beaker (eggs side down). After 3 minutes, use a pair of forceps to gently remove the paper, making sure that all the egg cysts have washed off into the water.
Repeat steps 2 to 7 for all the temperatures that are to be investigated. • If possible replicate the treatments. • Incubate the beakers at the appropriate temperatures. • The next day count the number of hatched larvae in each of the beakers. To do this, place a bright light next to the beaker. Any larvae will swim towards the light. Using a fine glass pipette, reversed with the tip inserted into the teat, catch the brine shrimps and place them in a small beaker of salt water. • Repeat the counting daily for several days. Brine shrimps are very delicate and care must be taken when handling them. Finally, release the young brine shrimps into a salt water aquarium. • Record the number of larvae that have successfully hatched at each temperature.
What would be the: • safety precautions taken • the ethical issues arising from the use of living organisms To find out more about brine shrimps, visit the British Ecological Society website.
