Datasets:
patrickbdevaney
/
mia9

Dataset card Data Studio Files
xet
 Community
1
text
stringlengths
0
6.44k
include: roseate spoonbill, mangrove cuckoo, various herons and egrets, bald
eagle, wood stork, brown pelican and West Indian Manatee.
The majority of the substrate in this sub-region is barren, although seagrasses are
present in some shallow areas. An oyster bioherm exists near the mouth of the
Snake Creek canal. This oyster community is notable in that, although oysters,
which prefer salinities between 5 and 20 ppt, were thought to have been fairly
common historically, are presently nearly non-existent in other areas of Biscayne
Bay.
Northern Biscayne Bay
In the Northern Biscayne Bay sub-region, which extends southward from the
Oleta River sub-region to the northern edge of the Venetian Causeway, Biscayne
Bay is considerably wider than it is to the north. Although the presence of the
barrier island of Miami Beach separates the Bay from the Atlantic Ocean,
Haulover Inlet is within this sub-region, and this tidal connection allows
significant tidal exchange.
The majority of the natural shoreline vegetation in this area has been replaced by
vertical seawalls, and a considerable portion of the bay bottoms have been
altered by dredge and fill activities. In spite of these conditions, seagrass
communities are abundant and in fairly good condition in much of this subregion. To the north of the 79th Street Causeway, seagrasses are primarily in the
western portion of the Bay. A notable feature in this area is a dense manatee
grass (Syringodium filiforme) community, possibly the largest and healthiest
manatee grass community in the Bay (Markley and Milano 1985). This grassbed
Figure 8
Designated Critical Habitat for Johnson’s Seagrass (Halophila johnsonii)
Source: Federal Register; Vol. 65, No. 66, Wed., April 5, 2000, p17804
Biscayne Bay Characteristics
Freshwater Flow and Ecological Relationships in Biscayne Bay 2-17
covers much of the Bay bottom from the 79th Street Causeway south to the
Venetian Causeway. It is possible that the freshwater inputs from the Biscayne
Canal and Little River result in the lower salinities which are favored by manatee
grass as opposed to turtle grass (Thalassia testudinum) which typically prefers
higher salinity areas. Another option is that this large area persists due to a
tolerance for higher turbidities by manatee grass.
These extensive grassbeds, which do also include Johnson's seagrass (Halophila
johnsonii), provide habitat for a variety of other organisms, including various
fishes. The entire bay bottom in this sub-region has been designated as critical
habitat for Johnson’s seagrasss (Figure 8). Spotted seatrout (Cynoscion nebulosus),
which have well-documented salinity preferences of less than 25 ppt during their
juvenile stages, are documented to occur in this sub-region, which is notable in
that this species is largely absent from other areas of the Bay (Serafy et al. 1997).
Manatees are documented to occur in this area, and it is believed that manatees
that are attracted to the warm water discharge from the coastal power plant at Ft.
Lauderdale travel to this region to forage in the dense grassbeds (DERM 1995).
Miami River/Government Cut
In comparison to the other sub-regions, the Miami River/Government Cut subregion is a relatively narrow northwest-southeast corridor that extends from the
Venetian Causeway on the north to the south side of Rickenbacker Causeway on
the south. This portion of the Bay has been highly altered. The Miami River,
which has been channelized, is intensively used for commercial purposes.
Through the years, heavy metals and other contaminants have accumulated in
the sediments of the river, which presently has a comparatively low diversity of
flora and fauna. Much of the natural bottom contour in this sub-region has been
modified as a result of dredging and filling activities. The Port of Miami, and its
associated navigation channels are within this sub-region, which also extends
eastward and includes Government Cut, the tidal inlet and navigation channel
that links the Bay to the Atlantic Ocean. Although seagrasses are present in the
southern portion of this sub-region, large areas of dredged bottom are primarily
barren.
Surprisingly, in spite of these significant alterations, from a fish diversity
perspective, this sub-region actually is one of the most highly diverse regions of
Biscayne Bay (Serafy et. al. 1997). This fish diversity is likely a direct result of the
varying salinity regimes of the different areas within this sub-region. From
upstream areas in the Miami River, where salinities are minimal, there is a
salinity increase until marine conditions are encountered at the direct
connections to the ocean at Government Cut and Norris Cut.
Biscayne Bay Characteristics
Freshwater Flow and Ecological Relationships in Biscayne Bay 2-18
This variety of salinity regimes provides habitat for varying floral and faunal
assemblages and benthic communities, including species that frequent
oligohaline areas (e.g., mullet, Mugil spp.), those that inhabit mesohaline areas
(e.g., blue crab, Callinectes sapidus, shoal grass, Halodule wrightii), those that
inhabit areas with marine salinities (e.g., paddle grass, Halophila decipiens, bluestriped grunt, sailor’s choice) and of course, those species that can tolerate highly
variable salinity conditions (e.g., manatees).
During baseline studies related to potential modifications at the Port of Miami
(Dial Cordy and Assoc., 2001), seagrasses mapped based on inspections of 35
transects within a portion of this sub-region documented the presence of
shoalgrass, paddle grass, manatee grass and turtle grass, in decreasing order of
abundance. Although not reported by Cordy and Associates as occurring within
their study area, Johnson's seagrass is known to be present within this subregion. With the exceptions of the Miami River itself and the deepwater areas of
the Port of Miami, the bay bottoms within this area are designated as critical
habitat for Johnson’s seagrass (Figure 8).
The marine water quality conditions, including salinity, that result from the
direct connections between the Bay and the Atlantic Ocean also create suitable
habitat for a variety of typically marine macroalgae, including Caulerpa prolifera,
Halimeda sp., Udotea sp., Penicillus sp. (Dial Cordy and Assoc., 2001, Zieman,
1982). Queen conch, long-spined sea urchins, nudibranchs, mollusks, and
crustaceans, including spiny lobster and blue crab, and various soft corals and
sponges were also noted within this sub-region (Dial Cordy and Assoc., 2001).
Aerial surveys and telemetry tracking have documented the presence of West
Indian Manatees within this sub-region (DERM, 1995). These monitoring efforts
have also documented the presence of manatees in upstream reaches of the
Miami River. The extent to which fresh water and/or comparatively warmer
water temperatures during winter months are the attracting features for
manatees is not known.
Dial Cordy and Associates (2001) also note the presence of loggerhead turtles
(Caretta caretta), green turtles (Chelonia mydas), and leatherback turtles
(Dermochelys coriacia) within their study area, and the nesting of these species
along suitable beaches within this sub-region, including Fisher Island. These
species are designated as threatened (loggerhead) and endangered (green and
leatherback) by both the State of Florida and federal resource agencies.
Biscayne Bay Characteristics