Often times the oceans feel distant and far away such that we never actively link the effects of the climate around us to our little friends under the sea. One such effect of ongoing climate change is decreasing salinity of oceanic waters. As climate change causes increased precipitation and melting of ice due to increased global temperatures there is increased water run off into streams and ultimately the oceans. This has implication for many organisms in the oceans that isoconform their internal environment to the external environment. For example on a hot summer day when we might spend too long in the swimming pool, our skin has a tendency to shrivel and become, as we all dread before entering that pool, “pruny”. This concept also applies to organisms that live in the sea, such if there is too great of a difference in the salinity of water in comparison to its internal environment they begin to experience changing levels of ion and extracellular fluid. In situations were external environment has significantly decreased levels of salinity they can essential take in water and “bloat up” such that their physiological functionality is detrimentally affected.
So in lab last week we studied how barnacles, or Balanus Glandula, reacted to decreased salinity conditions. Barnacles are sessile and feed through the use of remarkable looking appendages known as ciri that beat with an enchanting rhythm as the barnacle captures its food. We attempted to determine the effect of decreased salinity on the proportion of individuals feeding alongside several other factors. Another component to our experiment was determining if barnacles displayed a certain level of adaptability or acclimatization to low salinity conditions depending on what region they called home. We placed barnacles from Vancouver, an area that is known for variable salinity that can become quite low at times, and Bamfield, an area of stable and high salinity, in test salinities of 12, 20 and 28ppt and attempted to get the barnacles to feed. This resulted in hands swishing in the water for almost three hours in order generate artificial current to make them feel more at home and lure them to feed.
Our results pointed towards the possibility of a local adaptation of barnacles from Vancouver as they had a greater proportion of individuals feeding in all test salinities in comparison to Bamfield. A potential reason for this may be that since barnacles from Vancouver are exposed to more variable salinity conditions there would be greater selective pressure on their traits to help increase their salinity tolerance, whereas a stable environment such as Bamfield may not present such pressures. Hence, whereas at lower salinities the Bamfield barnacles would have closed up shop in order to prevent salinity stress, the Vancouver barnacles may have been better adapted to tolerate this stress and thus a greater proportion were feeding.
If barnacles have gotten you thinking about biology take a look at these links:
Melting Ice caps and Decreasing Ocean Salinity: www.newton.dep.anl.gov/askasci/gen06/gen06794.htm
A Barnacle Feeding with the soothing touch of ambient music: