Where has all the grass gone?

Much of 2001 was plagued with less than 4 ft of visibility near the bottom and we didn't venture there as diving is a visual sport.  Then during our winter diving, when the visibility opened up a little to 10 - 20 feet, we came to the realization that something was amiss at Falling Rock Quarry.  We couldn't put a finger on it for a while.  There was something just not right.  Then we realized that when crossing the bottom it was a desert.  A couple years ago there were acres of grass beds throughout the quarry at the 35 - 40 foot level.  These beds, which were 2 - 3 foot tall provided a habitat for fish and helped keep the visibility in check by isolating the fine silt on the rock floor of the quarry from passing divers.  Unfortunately, the grass has died off.  We were sure that the grass was perennial.  We visit many quarries which are as cold and they have healthy growth.  We then thought we may have a species which may experience an annual winter die-off.  We could not believe what we were seeing.  Before saying anything, we decided to monitor the bottom during the summer of 2002.  Unfortunately, the visibility near the bottom was so poor in 2002 that we rarely had a chance to see it even from 6 inches above it.  Our only hope seemed to be to wait out the season till fall and the algae bloom die-outs and lower diver traffic to verify our suspicions.  Now that a full year has passed, we know the grass is indeed gone.  All that remains are the rotted tips of the stems that dot the quarry floor like black dots of ink on a sheet of paper.

The exact cause is debatable.  The results are not.  Since the die-off, visibility has become consistently poor.  It has gotten to the point where 10 foot visibility is considered good.  Two years ago, before the die-off, we had 50 foot vis in the winter and days in the summer reached 20- 30 foot even on the bottom. I can remember swimming along the surface in the winter and seeing all the bottom details 40 foot below!  There is normally a big difference between summer and winter visibility due to algae growth.  

This writer thinks that there are three principal causes:  One, the summer of 2001 was a very dry one.  Falling Rock is a small quarry with no spring feed.  Two, there has been a steady increase of diver traffic the last two years.  It  is reasonable to expect the quarry to be impacted by diver traffic in the best of times.  Three, poor buoyancy and trim techniques as displayed by the vast majority of open water divers who frequent the local quarry.  Taken individually, these factors would most likely not have caused the grass die-off.  However taken collectively, it was too much for the normally tough grass to take.  The die-off coincided with this very dry summer and the increase in traffic to the quarry.  I am sure that there are other factors such as a heavy algae bloom.  There are several types of algae that grow on the rocks and walls of the quarry that were continually swept by the inattentive divers.  This would have also contributed to the decrease in visibility.  

My supposition is that vast amounts of silt were stirred up, which covered the grass beds enough to suffocate them.  Not enough light could get thru the silt covering the plants to continue the photosynthesis process, and the grass died off.  Joe, the owner, thought it may be that the grass carp ate it all up.  However, this is not born out as there still are decent grass beds in the shallow areas in the southwest side of the quarry which see little traffic and get lots of sunlight.

Poor diving techniques have always been a problem.  We have all heard about the importance of good diving habits.  We, as divers, constantly hear about diver damage to coral reefs.  What divers are unaware of is that good diving techniques are as much about good habits as anything else.  The only way to become good is to dive and be constantly aware of where your fins are.  In the open water class, there is just not enough time and attention placed on the finer points of buoyancy and trim.  Even taking an advanced class will not address the problem.  Good buoyancy and trim are attained by those divers who have the desire and will to do it right.  It is not really difficult, but there definitely are some tricks that can be used to help the diver with the will to do it.   The easiest way to get good at it is to take a class on buoyancy and trim.  But first dive with the instructor you are considering and see if his techniques warrant your trust.  Unfortunately, many instructors are clueless to the art of good trim.  Most can exhibit good buoyancy, but it takes the two skills in combination to be a conscientious diver.  A good diver should be able to hover a foot above the bottom in a silty environment like most quarries and propel himself or herself through the water with no impact on the silty floor!!

We are seeing an increase in the visibility which is normal for this time of year.  There is no diver traffic and the summer algae has died off.  Even so, we are only getting 20 - 30 foot visibility.  This is far below what we used to experience at this time of the year just a couple of years ago.  There is a ray of hope as there are some faint  signs of a recovery on the southeast side of the quarry.  Just this past weekend we noticed some small shoots in a couple of areas.  They are small, as they are isolated and only 2 - 3 foot in diameter and 6 inches tall.  However, it is a start.  If these areas can be encouraged to expand and we can raise the awareness of the divers who frequent the quarry, there is a chance the visibility can once again increase to previous levels.  

We are open to suggestions as to how we could promote more plant growth.  To that end, I would like to start a small project to transplant some small seed beds. We could use some volunteers to help implement this program.  During the upcoming dive season, we would like to have some volunteer dive buddies to help mentor new divers in good diving habits.  If we help a new diver realize how much impact they can have in a quarry like Falling Rock, they may just take their good habits to the coral reefs.  Please contact me by email at dale@airheadsscuba.com or 502-957-1226

Dale Bletso

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