|
The first impressions |
of the research area
are the existence of a great fauna & flora and a good basic for our project,
the research about the circadian rhythms, the difference of the behaviour from
the animals at night and daytime. There is a big difference between day and
night (light, temperatures, etc). Some organisms are nocturnal meaning that
they come out only at night time. They adopted this through evolution. A
reason for this is to avoid predators that are around during day time. It is
like a defence mechanism. Also some of their prey or food is more abundant
during night time. This is because there are lot of organisms that have a
vertical migration between day and night in the water column and at night time
they are found near the bottom. Some of the animals that feed on them come out
at night time since that's when they can find them. It is easier to find prey
or food. This will be investigated in the next 4 weeks. |
|
Intermediate Report |
During the recent
dives, I gained plenty of new experiences: I was able to observe animals and
biocoenosis I only knew from books. Though, I would like to confine myself to
only describing that kind of animals and their behaviour, which is of
particular significance in the context of circadian rhythm.
The question of whether an animal is to be denominated as nocturnal or diurnal
is generally answered by regarding the maximum activity of ingestion. The
specific time of ingestion is subject to a strong rivalry amongst the diverse
species: in case of insufficient satisfaction of their needs, there will be an
intensive competition for food, space or other ecological requirements between
two different species, which demand a similar environment.
The ecosystem is substantially influenced by these kinds of adaptation
processes. Considering the example of the vertical movement of the plankton,
this becomes most apparent: After sunset, the plankton moves to the surface.
Through this change in stratification, certain surface areas offer remarkably
more nourishment during the night than during daytime.
We are diving at “Jubilee Shoal”, which is a 20-30m deep steep face, located
approximately 25 m under surface level. At night, the plankton is rustled up at
this wall.
Thus, during the day the area is basically populated by some medium scale fish
that devour plants or small micro organisms, e.g. “Meerjunker” or “Meerpfau”.
These fish use the walls and sandy grounds as a source of nutrition and sleep
close to the ground or in crevices during the night.
Then, it is the time of the animals who avoid food-related competition with the
diurnal species through setting their maximum activity over night; this
primarily origins in the vertical movement of the plankton (the preferred
source of food). Other animals again eat the plankton-consuming ones, which
leads to a completely new image of the ecosystem during the night compared to
daytime. Especially the places exposed to current are attracting lots of
organisms.
Particularly eye-catching were some decapods, e.g. the big prawn or the
“Scherengarnele”, which are only nocturnal.
Visible during the day are in the first instance the species able to protect
themselves against predators, e.g. “Feuerborstenwürmer” that shield themselves
with fine bristles able to intrude into the attacker and to hurt painful. Other
diurnal animals are - for example - scavengers or the yellow stone coral that
provides protection with its cnidoblasts. Also noticeable were animals like
the “Weissspitzschnecke” or the “Violette Fadenschnecke”, which also protect
themselves through cnidoblasts which they extract from polyps they ate before.
This animal also deposits its eggs only during daytime. |
