Alafia River Minimum Flows and Levels - Southwest Florida Water ...

USGS Lithia gage that would be necessary to inundate specific floodplain
elevations (e.g., mean vegetation class and soils elevations).
4.2.5 Aquatic Invertebrate Community Assessment
Descriptors of aquatic invertebrate community structure, including absolute
abundance, relative abundance, Shannon diversity, and evenness of distribution
were determined to evaluate the importance of various habitats in the Alafia
River corridor.
Invertebrates were sampled at a site in the river near Site 64 at Alderman Ford
Park, in the Lithia Springs Major run and Buckhorn Creek. Prior to the initial
sampling event, the areal extent of discrete habitats (both instream and on the
stream bank) along each transect was computed and mapped. A minimum of
four habitats was sampled at each site during sampling events. Three
pseudoreplicate samples were collected from each of the sampled habitats.
Habitats sampled were bedrock, sand, mud (backwaters), snags, leaf
packs/mats, filamentous algal mats, floating vegetation and rooted aquatic
vegetation.
Collection methods and gear types were habitat specific with the ability to
quantify abundance and biomass estimates on an areal basis (number of
organisms per square meter). Qualitative collections were taken in each habitat
as a method to ensure that quantitative methods provide an accurate indicator of
species richness. Bottom sediments were sampled using a petite ponar dredge,
an Eckman dredge, or a Hess Stream sampler (Merritt et al. 1996). Bedrock and
aquatic macrophytes were sampled using a modified Hess stream sampler
(Warren et al. 2000) while floating vegetation was sampled using a quantitative
dip net method (Warren et al. 2000). Snags were examined by enclosing
portions of submerged limbs or trunks in heavy-duty plastic bags and sawing off
the enclosed sample portion (Warren et al. 2000). Leaf packs and filamentous
algal mats were sampled using a traditional or modified Hess stream sampler.
Upon collection, all samples were rinsed in 600 micron mesh sieve buckets to
remove excess water. Samples were preserved in the field with 95 percent
ethanol and placed, separately, into suitable containers for transport to the
laboratory.
All samples were processed in the Florida Fish and Wildlife Conservation
Commission (FFWCC) aquatic invertebrate laboratory at the University of
Florida, Gainesville. Prior to processing, samples were sieved (600 micron
mesh) to remove excess ethanol. Small sample portions were then placed in
petri dishes, covered with water, and processed by technicians using
stereoscopic dissecting microscopes with magnifications to 40X. Organisms
from samples were removed, identified to major taxonomic groups, and
enumerated to each identified taxon. Organisms were identified to the species
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