Page 39 - Coral Reef Teachers Guide
P. 39
Coral Reef Teacher’s Guide Benefits, Threats, and Solutions
The lucky few planulae which successfully ing, especially bottom trawling and dredging.
attach to substrate next confront competi- In typical groundfish trawling, a large net is
tion for food and space.Over 4,000 species dragged across the ocean floor, its mouth held
of fish inhabit coral reefs. The vast majority open by two 2-tonne doors called otterboards.
occupy the Mid Reef zone. Healthy reefs can The siliceous skeleton of the sponges is frag-
produce up to 35 tons of fish per square ki- ile, and these organisms are easily broken by
lometer each year, but damaged reefs pro- physical impact. While less harmful, hook and
duce much less. Much attention in marine line fishing as well as crustacean trapping
biology is focused on coral reefs and the El may also damage the reefs. When the fishing
Niño weather phenomenon. In 1998, cor- gear is hauled to the surface, the lines and
al reefs experienced the most severe mass traps drag along the ocean floor and have the
bleaching events on record, when vast ex- potential to break corals and sponges. Broken
panses of reefs across the world died be- sponge “stumps,” as well as those with abrad-
cause sea surface temperatures rose well ed sides, were found in regions where line and
above normal. Some reefs are recovering, trap fishing took place.
but scientists say that between 50% and Coral reef animals use many different forms of
70% of the world’s coral reefs are now en- protection. Some hide in the sand, others hide
dangered and predict that global warming among the coral. Some swim into the lagoon
could exacerbate this trend. The Shallow and hide among the mangrove roots while oth-
Shore and the Mid Reef are the most sus- ers swim in schools along the reef face. Some
ceptible to such beaching events because eject poison while others inflate themselves to
of the shallower depths they exist at. The a much larger size.
reefs are susceptible to damage by fish-
Figure 3‐17. Sponges are an important part of the coral reef ecosystem. This photo was taken at Cozumel. Mexico on the
famous Palancar reef system.
2 - 19
