Page 549 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 16 Oceans, Coastal Systems, and Wind Processes 513
Despite our understand-
ing of beach and barrier island
migration and warnings of
the effects of storms, coastal
development does not always
include precautions for limit-
ing erosion. Developers and
builders still ignore the sci-
entific evidence that beaches
and barrier islands are unsta-
ble, temporary features on the
landscape. One way to encour-
age sustainable environmental
planning and zoning might be
to allocate responsibility and
cost in the event of a disaster.
A system could be set up that
would place a hazard tax on land that is based on as- sessed risk and that restricts the government’s responsi- bility to fund reconstruction or an individual’s right to reconstruct on frequently damaged sites.
▲Figure 16.19 Worldwide distribution of living coral formations. The red dots represent major reef-forming coral colonies. Colonial cor- als range in distribution from about 30° n to 30° S. [nOS/nOaa, 2008.]
living in coral reefs place the number at a million world- wide, yet, as in most ecosystems in water or on land, bio- diversity is declining in these communities.
Figure 16.19 shows the global distribution of living coral formations. Corals mostly thrive in warm tropical oceans, so the difference in ocean temperature between the western coasts and eastern coasts of continents is critical to their distribution. Western coastal waters tend to be cooler, thereby discouraging coral activity, whereas eastern coastal currents are warmer and thus enhance coral growth.
Living colonial corals range in distribution from about 30° N to 30° S. Corals occupy a very specific eco- logical zone: 10- to 55-m depth, 27‰ to 40‰ salinity, and 18°C to 29°C water temperature. Their upper threshold for water temperature is 30°C; above that limit, the corals begin to bleach and die. Corals require clear, sediment-free water and consequently do not locate near the mouths of sediment-charged freshwater streams. For example, note the lack of these structures along the U.S. Gulf Coast. Cor- als have low genetic diversity worldwide and long gen- eration times, which together mean that corals are slow to adapt and vulnerable to changing conditions.
However, an interesting exception to these environ- mental parameters for corals are various species of cool corals that exist in the deep ocean, at temperatures as low as 4°C and at depths to 2000 m, well beyond the expected range. Scientists study these remarkable oddities, which do not rely on algae but harvest nutrients from plankton and particulate matter. Canada’s Centre of Expertise in Cold-Water Corals and Sponge Reefs, established in 2008, is located at the Northwest Atlantic Fisheries Centre in St. John’s, Newfoundland and Labrador (see www.dfo-mpo .gc.ca/science/coe-cde/ceccsr-cerceef/index-eng.asp).
Coral Reefs Corals exist as both solitary and colo- nial formations. The colonial corals produce enormous structures, formed by the accumulation of skeletons
CriTiCAlthinking 16.2
Allocating Responsibility and Cost for Coastal Hazards
What do you think about the idea of allocating responsibility among individual landowners in the event of a disaster? How would you suggest implementing such a strategy? What special interests might oppose such an approach? What response would you expect from city government or busi- ness interests? From banking or the real estate industry? What about the cost of mitigating coastal hazards to reduce the damage potential: Should landowners pay, or other stakeholders, or taxpayers in general? •
Coral Formations
Not all coastlines form by purely physical processes. Some form as the result of biological processes, such as coral growth. A coral is a simple marine animal with a small, cylindrical, saclike body called a polyp; it is re- lated to other marine invertebrates such as anemones and jellyfish. Corals secrete calcium carbonate (CaCO3) from the lower half of their bodies, forming a hard, calcified external skeleton.
Corals and algae live together in a symbiotic rela- tionship, an overlapping arrangement in which each depends on the other for survival. Corals cannot photo- synthesize, but they do obtain some of their own nour- ishment. Algae perform photosynthesis, converting solar energy to chemical energy and providing the coral with about 60% of its nutrition; they also assist the coral with the calcification process. In return, corals provide algae with certain nutrients. Coral reefs are the most diverse marine ecosystems. Preliminary estimates of species