The Determination of Minimum Flows for Sulphur Springs, Tampa

DRAFT
habitat in the lower river probably affects the rate of colonization by these species.
Although colonization by organisms that are aquatic throughout their life cycle can occur
through various means (e.g. bird droppings), the availability of freshwater habitat in the
river near the mouth of the spring during seasonal high flows from the reservoir allows
the colonization of the spring run by these taxa.
The final group of taxa recorded during the qualitative collections were those that
occurred during both normal flow and drought conditions. This group included 31 taxa,
which are denoted by not being shaded in Appendix B. This group is comprised of
widely distributed euryhaline species that generally do not have narrow habitat or
salinity requirements. These species were able to survive in the spring run during times
of normal flow, when there was stable low salinity and strong downstream currents on
outgoing tides, and also during the drought when there was high salinity in the spring
run and slower current velocities.
This general category contained taxa that were identified only to higher taxonomic
levels (e.g. Nematoda, Hirundenea) and others that were identified to species . The
criterion for inclusion in this group was broad - a taxon had only to be collected in at
least one drought collection and one normal flow collection. Some of these taxa
appeared in only two or three collections and may no longer be in the spring run, as
they were not collected in 2003. Other taxa were present during all or nearly all of the
collections in the study. These common taxa included nematodes, the amphipod
Grandidierella bonnieroides, the brackish water grass shrimp Palemonetes pugio, the
isopod Munna reyonoldsi, the pelcypod Mytilopsis leucophaeata, and three snails
Pygrophorus platyachis, Melanoides sp., and Tarebia granifera. As previously
discussed, the exotic snail Tarebia grainifera is the most abundant organism in the
spring run, and likely invaded the spring run between the 1997 and 2000 collections.
Melaoides sp. are also exotic snails that are tolerant of a wide range of environmental
conditions, including fresh and brackish salinities. Pyrogophorus platyrachis is also
common in both fresh and brackish waters. The taxa in this final group are probably the
least sensitive to the flow management of the spring.
3.7.3.4 Percent composition in various habitats
For two of the qualitative collections the FWC enumerated the catch and estimated
percent composition of all taxa in four habitats in the spring run. These two collection
dates corresponded to one sample from the drought (July 16, 2001) and one after
prolonged normal flows (December 09, 2003). Habitats in the spring run for which
percent composition was estimated in the November 2001 collection were open sand,
filamentous algae, shoreline vegetation, and concrete structure. The habitats for which
percent composition was reported were somewhat different for the 2003 sample,
comprised of open sand, filamentous algae, shoreline vegetation, cattails, organic
debris packs, and snags. Although percent composition values do not provide
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