paxfish
04-20-2010, 10:24 AM
Premise: Sedmentation is something that a Natural oyster bar is equipped to deal with. The natural 3-D shape slows turbid water during a high sediment event, the sediment falls to the low parts of the bar, and the oysters on the sides and top continue to thrive in the current flow. Benthic organisms in the troughs help break down some of that sediment over time.
Continued dredging flattens that natural profile making the bar more susceptible to sedimentation events. It covers up the troughs, kills benthic organisms and ruins that habitat. Further, it stresses the organisms that manage to survive making them more susceptible to disease.
From another thread we have:
uno
Average TF Poster - Not a Tidal Fish Subscriber
Join Date
Oct 2008
Posts
89
Originally Posted by paxfish
uno,
It's important to know that the vast majority of bay siltation occurred prior to 1900 before we (Chesapeake humans) knew much about soil conservation. This is easily confirmed via core sampling of bay sediment.
Knowing that, oysters in established, natural, 3-D bars were very capable of forging through the onslaught of sediment.
Response by Uno:
Nice theory and sounds wonderful. Unfortunately, it's not true. I can personally show you several oyster bars that are in restricted areas and haven't been touched by humans for decades that have disappeared due to silting! You think all of that chocolate brown water coming down the bay from PA after any type of runoff event is an illusion? The creek where I live has silted in over 2' in just the last 20 years. There are substantially more problems with the oyster population and recovery then many people want to admit.
So there's all kinds of stuff there in Uno's response. First of all, my statements about the vast majority of silting happening before 1900 is proven data. Further, the data shows that the rate of siltation is better now than it has been in the last 200 years. I'm not disputing that there is more siltation now than would occur if humans has not altered the landscape. I am saying that if the bars had not been wrecked by destructive harvest methods, that the oysters would continue to thrive just as they did during our highest sediment periods of the 1700s and 1800s.
Sediment study can be found here:
http://www.springerlink.com/content/5021718456p6766w/fulltext.pdf
This study shows that the current measured rate of sedimentation at four middle bay sampling sites is roughly .25 cm/yr. Over 20 years, that equates to 5cm or roughly 2 inches. The data show that the natural sedimentation rate is about 1/4 of that.
So - If you've got 2 feet in 20 years, I suggest you have a localized problem that needs to be addressed ASAP. What creek is that you're referencing? Maybe we can find some data.
Finally, you reference a bar in a restricted area that has been untouched by humans in decades. I'd suggest that no such bar exists because as DNR has made very clear, virtually every santuary bar that they surveyed last year had evidence of being heavily poached. Here's a very interesting thread on the topic: http://www.tidalfish.com/forums/showthread.php/283267-Oyster-Sanctuary-Poaching?highlight=sanctuary+poaching
Where is the bar you reference? Let's see if it is included in that survey.
Continued dredging flattens that natural profile making the bar more susceptible to sedimentation events. It covers up the troughs, kills benthic organisms and ruins that habitat. Further, it stresses the organisms that manage to survive making them more susceptible to disease.
From another thread we have:
uno
Average TF Poster - Not a Tidal Fish Subscriber
Join Date
Oct 2008
Posts
89
Originally Posted by paxfish
uno,
It's important to know that the vast majority of bay siltation occurred prior to 1900 before we (Chesapeake humans) knew much about soil conservation. This is easily confirmed via core sampling of bay sediment.
Knowing that, oysters in established, natural, 3-D bars were very capable of forging through the onslaught of sediment.
Response by Uno:
Nice theory and sounds wonderful. Unfortunately, it's not true. I can personally show you several oyster bars that are in restricted areas and haven't been touched by humans for decades that have disappeared due to silting! You think all of that chocolate brown water coming down the bay from PA after any type of runoff event is an illusion? The creek where I live has silted in over 2' in just the last 20 years. There are substantially more problems with the oyster population and recovery then many people want to admit.
So there's all kinds of stuff there in Uno's response. First of all, my statements about the vast majority of silting happening before 1900 is proven data. Further, the data shows that the rate of siltation is better now than it has been in the last 200 years. I'm not disputing that there is more siltation now than would occur if humans has not altered the landscape. I am saying that if the bars had not been wrecked by destructive harvest methods, that the oysters would continue to thrive just as they did during our highest sediment periods of the 1700s and 1800s.
Sediment study can be found here:
http://www.springerlink.com/content/5021718456p6766w/fulltext.pdf
This study shows that the current measured rate of sedimentation at four middle bay sampling sites is roughly .25 cm/yr. Over 20 years, that equates to 5cm or roughly 2 inches. The data show that the natural sedimentation rate is about 1/4 of that.
So - If you've got 2 feet in 20 years, I suggest you have a localized problem that needs to be addressed ASAP. What creek is that you're referencing? Maybe we can find some data.
Finally, you reference a bar in a restricted area that has been untouched by humans in decades. I'd suggest that no such bar exists because as DNR has made very clear, virtually every santuary bar that they surveyed last year had evidence of being heavily poached. Here's a very interesting thread on the topic: http://www.tidalfish.com/forums/showthread.php/283267-Oyster-Sanctuary-Poaching?highlight=sanctuary+poaching
Where is the bar you reference? Let's see if it is included in that survey.