With the South Kingston Bridge beginning, much is changing at the Carpenter Creek estuary. Traffic will be slowed at times. The scour holes on either side of the estuary will be modified so the deep holes created by tidewater funneling through the narrow culvert will likely disappear. The way the water moves the soil, sand, and debris from trees and shrubs will change greatly. New flow patterns will emerge and sediment habitats will change.
Several intrepid souls have spent days photographing, measuring, and collecting samples of sediment and bugs, to capture a snapshot of what the areas look like and how they function as aquatic habitat. Each survey takes several steps. First, the reconnaissance — walking the estuary side at low tide to see where its possible to walk without sinking knee-deep into mud. This determines where sampling equipment can be placed. Finally a consistent method of deploying and retrieving samplers is established.
One survey measured insects contributing to the diet of the fish that inhabit or pass through our the estuary. This was done by placing plastic containers with small amounts of soapy water along the shore for 24 hours to trap insects. The container deployment came with the sacrifice of a boot to the mud but otherwise worked well and no boots were lost upon retrieval. The bridge project won’t have a large impact on insect life, but the survey sheds light on why the fish use the estuary so heavily — good chow! We found mosquitoes, other flies, spiders, mites, ants, and some other larval critters.
In an attempt to document the change in sediment deposition several sampling transects were established. A transect is a line that is established on the landscape along which samples can be taken consistently over time.
To look at how the sediment type might change over time we established sample sites where the sediment type change currently (some sand, some rock, some shell). We used a consistent approach to taking sediment grab samples. Between two and 11 samples were taken per transect. We will sieve these samples to learn what size particles make up each location, and will identify the critters we collected in the grabs as well. We saw many crabs, different types of clams, and some parts of tubes that worms live in. There will be much more to see and many more hours of sample analysis.
A snorkeler with an underwater camera has attempted to document fish and other aquatic organism behavior at high time in the vicinity of the culvert. This same survey will be done in the future after the bridge is in place. We always hope our presence in the water does not influence the life we see, but it does. Salmon and other fish species sense your presence in the water and often flee. That same instinct protects them from predators. It is another reminder that we do change the picture when we are in it.
Nonetheless, we will still try to understand the picture as it unfolds with this new change to the environment across the next decade.
Betsy Cooper is a marine biologist and volunteer monitor with Stillwaters Environmental Center.
