Insect and Diatom Richness Distribution in Big Chico Creek
Ethan Poggi and Diego Reyna-Wood
Big Chico Creek is an urban stream that runs through the city of Chico as well as California State University Chico. Urban streams are known to have high nutrient and contaminant concentrations, and altered channel morphology and biodiversity. Our project focused on sampling aquatic insects and algae(diatoms) to assess stream health and water quality in different parts of Big Chico Creek on Chico State campus, as aquatic insects and algae can be used as biomarkers for stream conditions.
In order to collect data for this study, various sampling methods were used. We first established 4 transects along Big Chico Creek and chose a sampling site in the middle of each one. At each sampling site, to collect insect data, we performed 1 kick net sample at 3 wetted widths (25%, 50%, 75%) using a D-net of 1ft2 of stream bottom. Diatom collection was also fairly simple. At each sampling site, we used a toothbrush to scrape all the algae off 3 rocks, 1 for each wetted width (25%, 50%, 75%).
In total we collected 6 orders and 12 families of aquatic insects from our 4 transects and we collected 6 morphologies of diatoms. Depending on where we sampled insects and diatoms, we saw extremely different results.
Figure 1 and Figure 2 show insect and diatom richness and how it varies for each transect sampled.
Transect 1: This transect had the lowest species richness for both diatoms and insects. This makes sense considering that this transect had the fastest moving water and was the most channelized part of the creek.
Transect 2: Insect richness was the highest in this part of the creek, while diatom richness was second highest. This indicates that conditions were the best for insect species while not being the most ideal for diatoms. This part of the stream did seem to have more of a mix of sand and large rocks making up the streambed compared to the other transects. This may imply that these are more effective sampling conditions and possibly better habitats for aquatic insects.
Transect 3: This transect had the most similar measurements of species richness. At this site, the depth of the water varied from ankle deep at one end and waist deep at the other. The streambed consisted of baseball- sized rocks and sand. The diversity data we collected may help indicate that these types of stream conditions were optimal for both species.
Transect 4: Diatom richness was highest in this part of the stream. The water was moving fairly fast, but stayed relatively shallow (ankle deep) on both sides of the creek. Our data may support the idea that this is the most optimal site for diatoms in the creek.
Overall, the individual distribution of diatom and aquatic insect richness that we collected has helped map the physical conditions of the stream by indicating the most and least optimal physical conditions for each species. In the future we would like to test the chemical conditions of the water, in order to see whether or not they correlate with diatom and aquatic insect richness.