Coral alga with a growth
of small calcareous spiral-formed tubes that contain the tubeworm
Spirorbis corallinae. In the picture, a ormstjärna is
Sea-mats of the Flustrellidra family can both collect its food
from the surrounding water and
|from the alga it is atached to.
A great many algae emit large quantities of organic compounds into
the water, and it is said that Flustrellidra gets about 17%
of its energy needs from the toothed
wrack upon which it is atached. The toothed wrack is probably
not harmed by the Flustrellidra as it only utilizes those organic
compounds that are emitted into the water. The biggest damage that
Flustrellidra is that it prevents the flow of light to the
effected areas and therefore, photosynthesis is not as effective.
Grazers help and upset
Some of the roaming animals that congregate around
the algae, also eat them. These
grazers do not necessarily cause great damage to the algae, if they only
eat those parts that are old and need to be replaced, whereas if they assault
those areas that are important for growth and reproduction they can cause
serious damage. This is especially true if they are not restrained by some
form of regulating factor. For example, in certain areas of the world, sea-urchins
and certain shellfish have grazed heavily
on the kelp forests so that the kelp population has nearly been eradicated.
Great damage can be caused, even if grazing is not too heavy, for example
the Laminaria-skålsnäckor can instead of eating the leaf-like
parts of the kelp, graze on the more vital parts of the stem or torso. It
is enough that they graze just a little bit for the kelp to lose some of
its anchor power, and with the with
the next storm they are torn lose and washed up onto the beach.
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