MARINE BENTHIC SUCCESSION
Memory Stick or Floppy Disk
is a progressive, often predictable
change in species composition (and abundance) in
a community over time.
With time, certain
species may become rare or even disappear, while
others increase in abundance.
begins when a previously uninhabited
area becomes available for colonization. For
example, primary succession occurs when
retreating glaciers expose soil that has been sterile
for thousands of years. On the island of Hawai’i,
primary succession occurs on fresh lava from
disturbance of a previously inhabited area. A
forest fire or hurricane that damages a forest leads
to secondary succession as a new set of plants
initially begin to replace the fallen trees.
Although these examples involve plants, the
concept of succession also applies to animal
For example, temperate rocky
intertidal zones are first colonized by fast growing
algae, then barnacles, then slower growing algae,
and then mussels.
After the onset of succession, a community may
go through a number of
different flora and fauna dominate. A
sequence of communities encountered in a
particular location over time. Eventually, a stage
may be reached where community structure will
remain relatively constant in the absence of a
community state is called the
The species composition of a climax community
is dependent on the local environmental
conditions (e.g., temperature, rainfall, and soil
type). Other factors affecting the pattern of
succession and composition of the climax
community include the rate and sequence of
colonization of different species.
Simplified example of a successional sere
involving three plant communities.
The concept of a
, in which
there is a single climax community for a given
environment, has given way to the more dynamic
concept of the
. The pattern-
climax concept recognizes that most forests are
comprised of a patchwork of climax communities
and different seral stages (due to patches of
Some communities never reach a “climax” state
and are maintained in a state of subclimax.
occurs in communities that are regularly
This disturbance can come in a variety
of forms, such as herbivory, wind, fire, flood,
drought, ice scour, or wave action.
Mechanisms of Succession
Three primary mechanisms have been proposed to
act during succession: facilitation, inhibition, and
tolerance (Connell & Slayter, 1977).
, early successional species modify the
environment, making the environment more
suitable for germination and growth of later
successional species. For example, a nitrogen-
fixing plant may add nitrogen to nutrient-poor
soil, allowing nitrogen-loving plants to colonize.
Facilitation is extremely important during the