Biomonitoring: Using Benthic Macroinvertebrates to Determine the Health of the San Lorenzo River

Overview

Objectives/Goals To determine the water quality of the San Lorenzo River by analyzing the benthic macroinvertebrates, their diversity, and by finding good, middle, or poor water quality indicator organisms. Methods/Materials In the field we collected Benthic Macroinvertebrates, (BMI's) from one riffle at three diferrent transections with kick nets. In the lab we stored our samples in an ethanol glycerine solution. We counted and sorted our 100 bug sample using microscopes and numerous taxonomic references. Working as a team, and with our mentors, we were able to conduct an in-depth analysis of our sample. We found that over ninety percent of our sample was made-up of BMI's that are indicators of good water quality. Results Insect, Number, Eating Habits ,Niche: Blue Caddisflies 2 scavengers scavengers Heptageniidae (Mayfly) 1 range from predaceous to plant(algae) feeders omnivores Perlidae (Stonefly) 5 range from predaceous to plant(algae) feeders omnivores Tabanida (Deer Fly) 2 very predacious, eats other aquatic bugs carnivores Aquatic Nematodes 3 algae, ditritus herbivores Lepidostoma larval cases (Caddisfly) 2 eat algae, decaying plant matter and microorganisms omnivores Amphipoda (Scuds) 5 anything, including larger organisms omnivores Apatania larval cases (Caddisfly) 1 algae, decaying plant matter and microorganisms omnivores Optioservus (Riffle Beetle Larvae) 9 diatoms and algae herbivores Optioservus (Riffle Beetle Adult) 1 diatoms and algae herbivores Simuliidae (Black Fly Larvae) 1 algae herbivores Coenagrionidae Arval larva (Narrow-winged Damselfly) 1 very predacious, eats other aquatic bugs carnivores Hydropsychidae (Caddisfly) 67 small aquatic organisms and various plants omnivores Conclusions/Discussion 91% of the BMI#s were indicators of good water quality: caddisflies(72%), stoneflies(5%), mayflies(1%), damselflies(1%), and deerflies(2%). Due to the vast amount of good water indicators, it is plausible to assume that the river is in good health; this is also supported by the lack of moderate and poor water indicators. A mere 5% of our sample was comprised of moderate water quality indictors, solely scuds. This left us with only 4% of our sample composed of indicators of poor water quality, including aquatic

Awards (1)

• Category Award

Competition history

• CSEF 2002 Earth Sciences/ Planetary Sciences/ Physical Environments · Entry S0601

Resources

• CSEF project summary ↗

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