"Brrr!" That is what many people have been saying in several cities across the United States over the past week, including all of us here at the YSI Headquarters in Ohio. The recent blast of Arctic cold form the polar vortex is to blame for the coldest temperatures in almost two decades in many U.S. cities, with some areas reaching record breaking lows on January 6th and 7th.
We know what happens to us when it gets this cold: the layers get added, the boots come out, hopes rise that our cars will start, that our doors aren't frozen, that our pipes don't break and of course the roads stay safe. But what happens to fish and the quality of our water bodies when water temperatures change this much? Temperature plays a huge role in our water bodies and the animals and plant life that call them home. Temperature determines which organisms will thrive and which will suffer in both population and size, basically temperature is a limiting factor to what kind of organisms can live in rivers and lakes.
Let's take a look at the fish:
All aquatic organisms have a thermal death point, and a thermal point that produces optimal abundance. If temperatures go outside the preferred temperature range of aquatic life (either too high or too low), the survival rate decreases significantly. When temperatures go outside of the optimal range, physiological stress occurs. When aquatic organisms become stressed, they become infrequent because activities are limited when water temperatures are at levels that produce discomfort or stress.
Sudden, drastic, changes of 5º C or more, in temperature are believed to be very harmful to fish life. Some fish species, cannot survive temperature shocks like these.
Median Tolerance Limits have been created to identify different species' temperature tolerance. Some fish are more tolerant of temperature differences, such as goldfish, bass and carp, while others, such as trout or salmon are much more sensitive. This logic only applies to adult fish. When it comes to fish spawning and eggs hatching, lower temperatures are required - but not too low. Many species spawn only above or below specific temperatures.
Ability for reproduction is one of the main distinctions between cold-water fish and warm-water fish. Cold-water fish can breed at temperatures only a few degrees above freezing, but warm-water fish can only start breeding at much higher temperatures. The record-breaking low temperatures the past few days could make it impossible for any fish to breed.
Let's take a look at the water body:
These brutally cold temperatures didn't last long, only a couple days, and temperatures are rising back to what is normally expected for cities across the country during this time of year. However, as temperatures start to warm up, and the snow and ice melt, runoff from parking lots, roads and farms will begin to join our surrounding water bodies. A lot of this run off can contain pollutants such as trash or leaking motor oil. Salts that have been laid on the roads for driving safety will also increase salinity levels in the water.
The positive side of the colder months is our lakes, rivers and streams water quality is most likely significantly better now than in warmer months. The negative effects on water quality due to low temperatures and runoff will correct themselves, naturally, much quicker. Temperature has a huge influence on water chemistry. Chemical reactions usually increase with warmer temperatures with higher conductivity levels, and toxicity of compounds along with decreased dissolved oxygen levels. These factors can make it very difficult for the survival of different species of aquatic life. It is important to spot check these parameters several times throughout the year to ensure the health of a water body and the aquatic life it is home to. YSI, proudly, manufactures water quality instrumentation that can test a number of various water quality parameters such as conductivity, temperature and dissolved oxygen throughout the year to ensure our water bodies are at optimal survival levels for aquatic life.