Assessing Water Quality with Ecological Characterization

Biological Community Characterization

• Fish - chemistry, flow regime, habitats
• Invertebrates - chemistry, sediment, flow regime
• Algae - nutrients and sunlight
• All - trophic effects, invasive species

Fish Collection

• Electroshock over a standardized reach length, once on each bank
• Add seining to collect difficult species such as catfish
• Get species richness, abundances, biomass
• Health anomalies and size/weight can help to evaluate populations

Invertebrate Collection

• "QMH" - qualitative multi-habitat - used to determine species richness
• "RTH" - richest targeted habitat - used to evaluate abundances in a specific habitat - usually the dominant habitat or habitat known for high species diversity

Algae Collection

• In addition to Quantitative Multi-Habitat and Richest-Targeted Habitat:
• Phytoplankton - directly assess midchannel chemistry and conditions
• Depositional habitat - assess exposure to adsorptive chemicals

Habitat Characterization

• Morphology and riparian landuse - measurements of stream shape, riparian landuse description, shade/sun, large-scale conditions
• Instream habitats and bed substrates - flow, sediments, aquatic vegetation, woody debris, small-scale conditions

Large-scale physical conditions

• Use morphology and riparian landuse to make an independent assessment of overall human impact
• Add to water chemistry data
• These variables dependent on local climate, geology/geomorphology, natural history, and human activities

Small-scale physical conditions

• Instream habitat relates most directly to species abundances and presence/absence
• These variables dependent on morphology, water chemistry, and riparian landuse
• Species presence and abundance is dependent on a combination of large- and small-scale physical conditions

Disturbance indicators

• Different species and taxonomic groups will act as indicators for different types of disturbance:
• Chemically-sensitive species - inhibited, intoxicated, or promoted
• Habitat-dependent species - specific habitats for reproduction, daily survival
• Trophic structure - presence of predator, prey, or competitor species

Chemistry indicators

• Certain algae indicative of nutrient enrichment, high plant biomass
• Low species diversity also indicative, due to competition
• Dominance of particularly tolerant species
• Sensitive invertebrates lacking from some areas
• Sensitive fish show health problems, out-competed by other species

Habitat indicators

• Fish need certain substrates for spawning, pools to shelter young
• Woody debris and aquatic vegetation critical habitat for many bugs and fish
• Species have different tolerances for flow conditions - changes in flow frequency, as with urban sites, changes species composition
• Channelization, riprap, clearing and snagging trees - changes available habitats

Trophic indicators

• Extirpation of a species due to competition, frequently with an introduced species
• Introduced species often more tolerant of human stream modifications
• Changes in food or habitat for one species may cascade through food chain

Applications

• Baseline characterization prior to water-management projects
• General water-quality assessment
• Assessment for specific water-chemistry issues such as TMDLs
• Game fish population management
• Study and control of introduced species

Examples

Bayou Lacassine physical characteristics

• Low gradient, low velocity
• Narrow, forested floodplains
• Muddy, high organic sediment
• Abundant woody debris and aquatic vegetation
• Landuse is largely rice, with low-diversity riparian forest, lots of Salvinia

Animals in Bayou Lacassine

• Reach length 1000m
• 22 fish taxa, 189 individuals
• Dominant fish taxa: shad, anchovy, catfish
• 49 invertebrate taxa, 2 EPT taxa
• 18% chironomids
• Notable invertebrates: Odonates, Oligochaetes, molluscs, beetles

Mermentau River physical characteristics

• Low gradient, low velocity
• Wide, forested floodplains with lots of fish and bug habitat
• Landuse is largely rice, but riparian forest is very diverse
• Muddy, high organic sediment
• Abundant woody debris and aquatic vegetation

Animals in Mermentau River

• Reach length 3000m
• 33 fish taxa, 1540 individuals
• Dominant fish taxa: bluegill and other sunfish
• 93 invertebrate taxa, 4 EPT taxa
• 16% chironomids
• Notable invertebrates: Oligochaetes, molluscs, beetles, amphipods, isopods, decapods, true bugs

Bayou des Cannes physical characteristics

• Deeply incised, channelized
• Some development of riparian forest, plenty of shade and woody debris
• Muddy sediment; deep, slow water
• Rice landuse
• Nutrient and pesticide loading noticeable

Animals in Bayou des Cannes

• Reach length 440m
• 13 fish taxa, 199 individuals
• Dominant fish taxa: mosquitofish, bluegill sunfish
• 58 invertebrate taxa, 6 EPT taxa
• 57% chironomids
• Notable invertebrates: Oligochaetes, beetles, amphipods

Bayou Grosse Tete physical characteristics

• Somewhat incised, channelized
• Floodplain disconnected, landuse agricultural and rural residential
• Very muddy, lots of woody debris
• Low gradient, low velocity
• Nutrient and pesticide loading noticable

Animals in Bayou Grosse Tete

• Reach length 500m
• 20 fish taxa, 842 individuals
• Dominant fish taxa: mosquitofish, sunfishes
• 50 invertebrate taxa, 5 EPT taxa
• 43% chironomids
• Notable invertebrates: Oligochaetes, beetles and true bugs, molluscs

Whiskey Chitto Creek physical characteristics

• Moderate gradient, moderate to high velocity
• Wide, forested riparian zone
• Sandy sediment, well-developed bars and pools
• Abundant woody debris
• Low-impact landuse, mostly forestry
• Low solutes, low contaminants

Animals in Whiskey Chitto Creek

• Reach length 800m
• 27 fish taxa, 685 individuals
• Dominant fish taxa: shiners, topminnow, blackbanded darter
• 58 invertebrate taxa, 21 EPT taxa
• 70% chironomids
• Notable invertebrates: Simulidae, beetles, Megalopterans

Tchefuncte River physical characteristics

• Moderate gradient, moderate to high velocity
• Forested riparian zone, some suburban landuse encroaching
• Sandy sediment, well-developed bars and pools
• Abundant woody debris
• Principal difference is nutrient loading

Animals in Tchefuncte River

• Reach length 420m
• 25 fish taxa, 243 individuals
• Dominant fish taxa: blackbanded darter, longear sunfish
• 67 invertebrate taxa, 18 EPT taxa
• 73% chironomids
• Notable invertebrates: Odonates, Megalopterans, Oligochaetes, Nematodes, sponges

Dawson Creek physical characteristics

• Deeply incised, channelized
• Mown regularly, no woody riparian vegetation
• Muddy sediment, lots of algae and aquatic vegetation
• No shade, sluggish flow except during rain
• Urban runoff high in contaminants

Animals in Dawson Creek

• Reach length 450m
• 14 fish taxa, 4118 individuals
• Dominant fish taxa: mosquitofish, sailfin molly
• 60 invertebrate taxa, 5 EPT taxa
• 7% chironomids
• Notable invertebrates: Oligochaetes, Odonates, Molluscs, Decapods

Bayou Boeuf physical characteristics

• Heavily industrialized local landuse
• Channelized, with heavy boat traffic and large wakes
• Some woody debris along banks, but habitat resembles lentic and estuarine areas in cover and salinity
• Low gradient, bi-directional flow

Animals in Bayou Boeuf

• Reach length 1000m
• 21 fish taxa, 1293 individuals
• Dominant fish taxa: anchovy, menhaden, shad, mullet
• 27 invertebrate taxa, 2 EPT taxa
• 91% chironomids
• Notable invertebrates: Oligochaetes, Molluscs

Summary

• Characterization of fish, invertebrate, and algae comunities, with habitat surveys, can be used to determine "problem areas" of water quality
• Ecological surveys can illuminate complex biotic interactions dependent on changes in water quality