The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
abundance estimates in number per square meter, they do give perspective on the
relative dominance of different taxa in the sampled habitats.
Percent composition values for the two dates are included as Appendices C and D.
Shoreline vegetation supported the most taxa of any habitat: 27 taxa in the 2001
collection and 33 taxa in the 2003 collection. Cattail habitat had 27 taxa in the 2003
collection, 13 of which were not recorded in the shoreline vegetation category. Since
cattails are shoreline plants, a total of 46 taxa were recorded in combined shoreline
vegetation in the 2003 collection. Cattails were also sampled in 2001 but not listed as a
separate category. Thus, the shoreline vegetation category exhibited a large increase in
species richness with the return to normal flows. In 2001 the percent composition of the
shoreline vegetation was dominated by Tarebia granifera (41.5%), snails of the family
Hydrobiidae (34.8%) and oligochaetes (13.6%), primarily of the family Naididae. In 2003
the shoreline vegetation community had much less Tarebia (6.4%) and oligochaetes
(0.4%), but a higher percent compositions of isopods (38%), Zygoptera (5.4%) and
Tricoptera (16.7%) compared to 2001.
Bare sand and filamentous algae had 8 and 10 taxa, respectively, in the 2001 collection.
The number of taxa in these habitats increased markedly in the 2003 collection, with 25
taxa reported for bare sand and 27 taxa for filamentous algae. Qualitative sweeps from
concrete structures were made in 2001 with 10 taxa reported. This habitat was not
sampled in 2003. Snags (submersed wood) and organic debris packs in the channel
were sampled in 2003, although the snag habitat was very limited. Tarebia continued to
be a dominant species in these habitats with 30% and 41.7% compostion in snags and
organic debris. Both of these habitats had significant percentages of amphipods and
isopods, the latter being particulary dominat in snags (43.3%). Aquatic insects were
common in organic debris packs, which contributed to a fairly high count of total taxa
(30) in this habitat. No aquatic insects were reported from snags in 2003, but this may
have been due to the very limited amount of snag habitat available for sampling.
3.7.3.5 Quantitative samples from May 2000, November 2001, and December 2003
The FWC collected quantitative samples of macroinvertebrates from benthic habitats in
the channel of the spring run on three of the collection dates: May 25, 2000, November
8, 2001, and December 9, 2003. Samples were collected using a petite ponar dredge
with an sampling area of 232 cm 2 . Samples were sieved in the field using 300 micron
sieve buckets and preserved in 95% ethanol. A full description of the field and
laboratory methods for site selection, sample processing, taxonomic identification and
enumeration can be found in Allen et al. (2001).
The findings of the May 2000 sampling, including discussions or species abundance,
evenness and diversity, are presented in the report Allen et al. (2001). The results of the
latter two collections will be discussed by the FWC in a final report to be published in
2005. The results from these samples, however, were made available to the District and
are presented below.
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