Presented by: Cooper, Mashishi, Mokataka, Moseki
KELPS – BROWN SEAWEEDS OF THE GROUP LAMINARIALES
habitat: hard substratum, exposed marine, cold water less than 20, but even less than 16 degrees, nutrient rich water
biology: morphology variable, often rapid growth, 30 cm per day in California
LIFE CYCLE: involves sexual and asexual spread, supply of gametes a problem for spread, also supply of spores by currents
KELP FORESTS – IMPORTANT FACTORS
(1) Physical – Nutrients, currents, temperature, storms
(2) Recruitment of kelp, larvae of invertebrates
(3) Plant – plant interactions such as shading
(4) Grazing by urchins, predation on urchins
Kelp Succession in Alaska
(1) Initiated by disturbance, predation
(2) Get mixture of kelps, including giant Nereocystis leutkeana
(3) Nereocystis is an annual so it dies off
(4) Laminaria establishes dense growths and shades all others, comes to dominance
Kelps – Trophic Level Interactions
seaweeds –> urchins –> sea otters
Effects on one level has strong effects on other levels.
Alternative stable states:
Barrens – urchins dominate and rove for food, results in hard bottom covered with coralline algae
Kelp forest – urchins present but drift algae supplies their needs, urchins hide in crevices
OUTBREAKS STILL OCCURRING
See What is Natural (Jan Sapp, 1999, Oxford University Press)
Kelp plants thrive on water products produced by fish. Together with the biofilter,the kelp purifies the water. As a result the kelp forest Exhibit has the best quality water in the Aquarium. South Africa’s kelp forests are home to many fish species found no where else in the world. Some fish such as strepies, southern mullet and hottentots live permanently in kelp forests where they find food and shelter while other types of fish move in and out of the kelp forest in search of food.
The temperature in this exhibit must be kept between 12 and 15°C to ensure optimum temperature levels for growth. In the wild kelp plants receive their nutrients from upwelling. During summer, the strong South Eastern wind which buffets the Cape Peninsula, blows the surface water away from the coastline. The kelp need sunlight to photosynthesis.
Cape waters is the only place in the world where you can consistently dive with Seven Gill Cow Sharks.You may also encounter prehistoric looking seven gill cow sharks in the kelp forests of False Bay, just off Miller’s Point.
With guided diving as an available recreational activity, you are offered an 85% chance of successfully spotting these predators all year round, in a 12m deep channel with a sandy bottom. Cat sharks and spotted gully sharks are also seen at this dive site, along with other marine life.
Divers come across a wide variety of sea animals along the Cape coastline, from whales and dolphins to seals, manta rays and different types of fish. Various kinds of sharks can also be spotted (mostly harmless ones), with the norm being that sharks leave scuba divers to be.
Requirements for diving in the Cape Waters :
Cold waters: dry-suits or good quality 7mm, 2-piece wetsuits are recommended for diving in Cape Town.
Summer Diving – Atlantic Seaboard (October to February)average water temperature of about 13°C, average visibility of about 10m beautiful reefs, kelp forests and shipwreck dives, both shore and boat based
When the south-easterly wind has been blowing the visibility can reach up to 20m, but then the temperatures tend to drop to about 10°C.
Winter Diving – False Bay (March to September)average water temperatures – between 12°C and 18°Caverage visibility of about 6mexcellent shore dive sites, deeper reefs and wreck dives accessed by boat
As with surfing in False Bay, scuba diving is best in the winter when the northwester blows, which improves the visibility (up to 15m).
Soil formation along coastal and continental shelf regions of the Cape marine biome contain mostly terrigenous soil created from sedimentary, metamorphic or igneous rocks that have been eroded and weathered above the surface. Rivers, ice and wind transport the sediment to marine waters.
Turbidity currents, underwater avalanches, sweep much of the terrigenous sediments around coastal waters and continental shelves but not to the deepest abyssal region of the ocean. Only the finest terrigenous sediments make it to this region to become clays.
In a nutshell, usually includes muds, gravels, sands, silts, clays or oozes.
The elements organisms require for development, maintenance, and reproduction are called nutrients. Ecologists refer to the use, transformation, movement, and reuse of nutrients in ecosystems as nutrient cycling. Nutrient cycling is one of the most ecologically significant processes studied by ecosystem ecologists. The carbon, nitrogen, and phosphorus cycles have played especially prominent roles in studies of nutrient cycling.
Within the Cape Aquatic Biome we describe the movement of carbon, nitrogen and phosphorus. Over time, these elements cycle through the biosphere, lithosphere, hydrosphere and atmosphere (the latter three are also called geospheres).They can be taken up by living things and used for growth and reproduction before either passing on to another organism or returning to one of the geospheres. They can be present in the atmosphere (except for phosphorus) as gases such as CO2, N2; in the hydrosphere as dissolved nutrients and gases such as PO43-, NO3- and CO2; or in the form of minerals such as carbonates, sulphates or phosphates in sedimentary and volcanic rocks.
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