Weeki Wachee River System Recommended Minimum Flows and ...

species include Hydrilla verticillata, Najas guadalupensis, Vallisneria americana and
Sagittaria kurziana, and the algae Lyngbya sp. and Chaetomorpha sp. (Frazer et al.,
2001; Clewell et al., 2002). Earlier surveys by Mattson (1995) reported the presence of
Ruppia maritima, Chara sp., Myriophyllum spicatum, Valliserneria Americana and
Hydrilla verticillatta at Rkm 0.5 (0.3 mi), which was the most upstream station evaluated.
More recent data focused on the estuarine portion was desired and during 2005,
Estevez and Leverone conducted twenty-six transects in the Mud and Weeki Wachee
rivers on May 17, 2005. Surface salinity ranged from 0 – 7 ppt. The Mud (thirteen
transects) was sampled from the sink at Rkm 3.8 (2.4 mi) to the confluence with Weeki
Wachee, while the Weeki Wachee was sampled at thirteen transects from Rkm -0.5 to
2.4 ( -0.3 to 1.5 mi). Bottom vegetation was quantified using standard Braun-Blanquet
rapid survey technique to assess frequency, abundance and density from the results of
up to ten 1 m 2 quadrats along each transect. The following scale was used to assess
coverage, and the following metrics derived from the results. The results are
summarized in Appendix 3-1.
A total of 8 taxa were collected: Hydrilla verticellata, Myriophyllum spicatum, Najas
guadalupensis, Potamogeton pectinatus, Ruppia maritima, Sagittaria kurziana,
Vallisneria americana, and Zanichellia palustris. Species richness was relatively high
for vascular species, and the highest species number occurred in the Mud River, from
Rkm 1.4 to 3.0 (0.9 – 1.9 mi).
Two species occurred over the full range of stations in both rivers– Potamogeton and
Myriophyllum. Ruppia occurred in the lower Mud and lower Weeki Wachee rivers but
was not collected in the Weeki Wachee upstream of the Mud River’s confluence at Rkm
1.4 (0.9 mi). Zanichellia, or horned pondweed, had the most interesting distribution for it
was not found in the lower or upper reaches of either river; its distribution was
centralized near and upstream of the river juncture. Physical and chemical conditions of
each river near the limits of Zanichellia’s range may be informative in terms of defining
this important species’ environmental requirements. Figure 3-5 portrays the distribution
of SAV from this sampling effort. Superimposed is the median bottom salinity for the
period 1984-2005 8 .
8 Note – The water quality period of record is slightly longer than the adopted baseline period in order to
incorporate recent systematic sampling by the District.
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Proposed Minimum Flows and Levels for Weeki Wachee River Page 43 of 164
Estuary Characteristics