|
PROPOSED
MEASURES: BIOLOGICAL COMMUNITY CONDITION
|
To understand the
condition of an ecosystem, we must know the condition of key groups
of species within that system. Some groups are important because they
play key ecological roles, whereas others are important because they
are powerful indicators of a disturbance to the ecosystem. For example,
in estuaries, seagrass provides a physical structure in which many other
species live, and animals that live in bottom sand and mud are good
indicators of degradation resulting from human influence. In addition,
coastal and marine areas consist of several distinct zones defined by
water depth, proximity to shore, salinity, or the existence of special
features such as coral reefs. We are developing a measure or set of
measures of the condition of key species groups in each of these different
habitat types. For the final report we will obtain additional data and
select and further refine these measures.
|
Key
Species Groups
|
Habitat
Zones or Types
|
|
Species
that provide habitat ("structural species")
Fish communities
(measuring overall declines in number of species or weight
of fish)
Key consumers/predators
(e.g., tuna, swordfish)
|
(Figs.
1, 2, 3)
|
Shoreline/Intertidal
— the area between high and low tide
|
|
|
Shallow
subtidal — shallow waters below high tide
|
(Fig.
3)
|
|
Estuaries
— where rivers meet the sea, and salt and fresh water
mix
Offshore/deep
water
|
(Fig.
1)
|
|
Bottom-dwelling
species
|
(Fig.
1)
|
Coral
reefs
|
(Fig.
2)
|
No national findings
can be presented based on the data available for this report. More extensive
long-term research and monitoring data are needed to fully evaluate
national and regional trends. All of the measures presented here are
in development.
Estuaries Example: Structural Species and Bottom-Dwelling
Animals in the
Chesapeake Bay (1) Technical
Note |
Coral Reef Example: Carysfort Reef,
Florida (2) Technical
Note |
 |
 |
| Source:
Orth, Virginia Institute of Marine Sciences, and Chesapeake Bay
Program |
Source:
Dustan and Hayles 1987 & Dustan et al, 1997, 1998 |
| This
graph shows two measures of the condition of the Chesapeake Bay:
percentage of seagrass relative to a predicted optimal level (where
100 percent is the optimum), and an index of bottom-dwelling animals,
for which 100 percent would be the optimum. |
This
graph shows the area covered by coral in Carysfort Reef in Florida,
as a percentage of the maximum area during the study period, which
began in 1975. This graph presents a short-term historical perspective. |
Shallow Water Example: Structural Species
(Kelp; Point Loma, CA) (3) Technical
Note |
Shoreline/Intertidal
and Deepwater (4) |
 |
 |
| Source:
Dayton, et al 1998 |
| This
graph shows the coverage of two kinds of kelp at an area off Point
Loma, California. Each year is presented as a percentage of the
maximum density of kelp fronds (analogous to branches) within the
20-year study period. |
|
STATUS
OF DATA & OTHER NOTES
|
No consistent
and comprehensive national information is available on the status
of, and trends in, key biological communities and habitats. Data
presented here are from individual research projects.
Please see
the Technical
Notes for additional information.
|
|
