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PalmTreeDude

Why Do Some Beaches Have Clear Water While Others Don't?

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PalmTreeDude

Why do beaches (normally closer to and in the tropics) have clear water yet places like the South Carolina coastline don't? I know Sardinia, Italy has crystal clear water and it is pretty far up there.

Edited by PalmTreeDude

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tropicbreeze

There's a lot of factors that can affect it. One is depth of the sea off the coast. Where water is very deep sediments settle at a level where they can't be stirred up by waves or currents. Large rivers flowing in carry sediments or colloids depending on the type of land they drain. Coastal waters nearby will consequently be affected. Warmer waters will tend to keep colloids in suspension a lot longer. You need to look at the local geography.

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Cikas

Plankton. Some waters are rich in plankton, while some are poor. Mediterranean Sea is poor in plankton. That is why our waters are crystal clear.

1-s2.0-_S1687428515000382-gr1.jpg

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bubba

Interesting question. For our area in South Florida, the ocean is generally very clear compared to ocean water to our north (Vero Beach). I believe this is a direct result of the close nature of the Gulfstream and the great depth of this moving river in the ocean approximately 2 miles off our coast. I believe tropicbreeze has quantified the reason for the clarity of the ocean water in this area (sediments settle in great depth and cannot be stirred up). Once you reach South Carolina, the Gulfstream is likely 50 to 60 miles off the beach and no longer can cause the clarity that result from the lack of sediments. However, after a hurricane (See Irma) our ocean water is a mess.

The pristine waters of the Mediterranean have always been a mystery. I did not realize that it was due to lack of plankton.

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Austinpalm
On ‎9‎/‎16‎/‎2017‎ ‎11‎:‎51‎:‎50‎, tropicbreeze said:

There's a lot of factors that can affect it. One is depth of the sea off the coast. Where water is very deep sediments settle at a level where they can't be stirred up by waves or currents. Large rivers flowing in carry sediments or colloids depending on the type of land they drain. Coastal waters nearby will consequently be affected. Warmer waters will tend to keep colloids in suspension a lot longer. You need to look at the local geography.

I get and agree with what you are saying but can you or anyone else explain why the Florida panhandle has such nice water (have not been there but have seen pictures and heard people talk about) when it seems to have fairly shallow water for some distance out and the Mississippi River is not too far away and pumping out all the sediment it can from the interior of the continent? When I look at a map, I get the impression the water will be the same chocolate milk color that we have for most of the Texas coast from Sabine Lake down to Corpus Christi. Both areas are on the same water body and within 400 mile or so of one another.

Edited by Austinpalm
misspelling

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Kim

Southern California ocean water clarity is greatly affected by seasonal swell size and weather. Large pounding winter waves and currents stir up the sand, tear at the seaweed, and make a mess of the water clarity, pulling sand out to sea and steepening the beach. Winter rains dump sediments and runoff carrying all manner of pollutants into the waters at outflow points along the coast, causing bacterial levels to rise and beaches to be closed for a time. In contrast, summer brings quiet seas that replenish the beach sand, warm water temperatures and dry weather resulting in astonishingly clear waters. The occasional chubasco moving north from Baja California, Mexico may bring waves, but not enough to ruin the water clarity beyond the impact zone where the waves are breaking.

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Silas_Sancona

Thinking water temperature and the upwelling effects of on shore vs off shore wind flow can play into water clarity.

In California, as Kim mentioned, a prolonged West or Northwest wind event often churns up all sorts of stuff. Thinking drawing up the cooler offshore waters stirrs more nutrient dense waters to the surface and brings Plankton blooms closer to the shoreline. Reverse the wind for acouple weeks and sst's start rising, water becomes clearer, esp. further south along the coast.

I recall seeing a similar situation play out at times when Id walk local beaches in Florida during the winter as well, though there is a much greater amount of shallower shelf water along the Gulf side of the state compared to California's abrupt transition from shoreline to 100+ft deep water. Seemed the composition of the sand there may also lessen the effects of heavy turnover compared to back west as well. 

 

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Xerarch
6 hours ago, Austinpalm said:

I get and agree with what you are saying but can you or anyone else explain why the Florida panhandle has such nice water (have not been there but have seen pictures and heard people talk about) when it seems to have fairly shallow water for some distance out and the Mississippi River is not too far away and pumping out all the sediment it can from the interior of the continent? When I look at a map, I get the impression the water will be the same chocolate milk color that we have for most of the Texas coast from Sabine Lake down to Corpus Christi. Both areas are on the same water body and within 400 mile or so of one another.

The sediment load from the Mississippi is primarily carried to the west and south by currents, this is fortunate for Florida and unfortunate for Texas. The higher the river flows, like in times of flood, the more widespread the sediment, sometimes all the way to South Padre. Consider this satellite photo from Bing images 

IMG_3588.thumb.JPG.ae8e9f53249de8f95c9fd

also consider that the slope in Texas is very gentle, this is related to what others have said regarding deep water vs shallow water. The gentle slope encourages the presence of fine sediments that muck up the water. 

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Laaz

Here in South Carolina the beaches are sand, but once you're off the beach everything is pluff mud. The tide brings the mud in and out & keeps the water cloudy. Once you get out a mile or so in the ocean you can see a line where the water is crystal clear.

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Alan_Tampa

Nutrient load is big part of water clarity, not just mud. Nutrient load promotes phytoplankton etc to grow, clouds the water. Carribean water is low in nutrients,  so Crystal clear. Gulf of Mexico is green way off shore, high nutrient load. 

 

At about 20miles out on west coast (Tampa area) start to see blue water. On east coast of Florida blue water at like 300 yards.

All the other factors at play also, (wind, depth, sediment, rivers, pool noodles also plays a big role!  

 

Just remember coral needs clear water, so if there is coral, there is low nutrient load in the water. 

Just my 1 cent.

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Walt

 The clearest water I've seen on the east coast was in the Portsmouth, New Hampshire - Kittery, Maine area. When I was in the navy, they sent me to a school there (Portsmouth Naval Ship Yard) for two weeks, located on the Piscataqua River, about 1-1/2 miles from the Atlantic Ocean.  I recall being on a pier or wharf, and looking down into the water, maybe 15 to 20 feet deep, and I could see clear to the bottom, seeing fish and other sea creatures. This was in May of 1969. I'm originally from Maryland, and I never saw water that clear at the ocean or back water in the Maryland - Virginia area.

But one notable thing about that area was that the river bottom was mostly rock.and the shores were very rocky. I think that rock, and lack of mud and dirty sand probably contributed to the better water clarity.

 

 

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AnTonY

Yes, the key to that "clear, tropical-looking water" is lack of nutrients (assisted by warm SSTs), lack of sediment-laden river sources nearby, as well as light-colored, rocky geology. The lack of nutrients helps to limit biotic processes that can interfere with water's natural blueness, as does lack of river sediment. Rocky geology then helps to limit suspension of whatever sediment is present, and, if light-colored, complements the water's blue in a way to make for that "turquoise" hue. This is the case for places like Cozumel, and also Sardinia in Italy (actually a lucky spot in the Med, as most beaches in the basin aren't nearly as clear and blue hued to that degree).

In the absence of rock content, beaches can still have great, tropical-looking blue water, but only on calm days without strong waves to stir-up the sand/sediment. As before, light colored sediment is best for complementing the water's blue to allow for the effect. This is the case for much of Florida's beaches. Even Folly Beach at SC witnessed this phenomenon for a time due to dredging for beach nourishment, which threw up light-colored limestone sediment that complimented any blue water present to make for that hue:
http://wbtw.com/2014/05/20/water-at-sc-beach-mysteriously-turns-beautifully-crystal-blue/

Blue is still be present in colder, more nutrient filled waters, but just in a darker shade, not quite that tropical hue and clarity. This is the case for upwelled low-latitude areas like California, or the Galapagos (seasonally), as well as the beaches of high latitudes (year-round). And of course, large rivers loaded with sediment can make water look brown, as in the northern Texas coast, areas of Georgia and South Carolina, the Rio De La Plata in Uruguay and Argentina, etc.

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AnTonY
On 9/19/2017, 5:58:18, Xerarch said:

Also consider that the slope in Texas is very gentle, this is related to what others have said regarding deep water vs shallow water. The gentle slope encourages the presence of fine sediments that muck up the water. 

The continental shelf maintains shallowness distances out pretty much all over the US Gulf, not just Texas. In fact, the shallowness extends further off the Florida Gulf, as well as north and west of the Yucatan. So its role in reduction of Texas water clarity is indirect at best (i.e. a factor only through another issue, in this case the sediment of the Mississippi).

The "cragginess" after the Texas shelf drop-off is actually complex underwater canyon geography resulting from the many salt domes that push up from the area; they hold sediment well, and don't dampen the water clarity in that distance (hence the blueness of the water around those off-shore oil rigs, supportive of the Flower Banks Coral Reefs)

Fixed_gulf_map.png

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Gonzer

  Just imagine "Look Mommy! I don't have to pee anymore!" and factor that by 10,000.

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Dave-Vero

I suspect there's all sorts of factors, and I assume an expert on beaches like Stephen Leatherman at Florida International University could provide a short explanation.  I think these factors may matter:

1.  local sources of fine matter (mud, organic stuff).  The rivers draining much of the eastern Piedmont more or less naturally have lots of very fine sediment and the salt marshes from the Carolinas through northern Florida generate lots of tiny organic particles.  Also, the St. Johns and St. Marys Rivers are loaded with tannic acids, which are brown.  

2.  Fine stuff in the beach sand.  This seems characteristic of Atlantic beaches, whether nourished or not.  So, as noted by Bubba, whenever there's the least bit of surf, the water turns murky.  The North Carolina Outer Banks tend to look like lentil soup.  

3.  Mineral composition of the beach sand.  The southeast Atlantic beaches have heavy minerals that are dark in color.  The Florida Panhandle and the Gulf beaches from Clearwater southward tend to be very heavy on white quartz, with Siesta Key famous for the whitest sand.  And rather clear water.  

4.  Offshore seaweed (kelp) can make for organic matter.  Offshore filter feeders (barnacles, mussels, corals, oysters) can make for clear water.

5.  Tropical environments where calcification happens (corals, mollusks, etc.) can be clear water.  Of course those corals are filter feeders.

6.  Nutrients, of course.   A nutrient-rich cold-water area like Humboldt Bay, California will be murky.   

What with east Florida's murkiness, I marvel at underwater surf videos from Hawaii and even Sydney, Australia with crystal water.  

 

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AnTonY
On 9/28/2017, 10:45:49, Dave-Vero said:

What with east Florida's murkiness, I marvel at underwater surf videos from Hawaii and even Sydney, Australia with crystal water.  

 

Well, Hawaii and Sydney do have lots of rock content on their coastlines; that implies less fine sediment that can be stirred up.

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GMann

This is what I have noticed:

1) Islands tend to have clearer water than the mainland, I think it is because they have much less large rivers that flow down to the coast, murky the waters, and bring a lot of dark sediment. This is why the islands in the Mediterranean have so many more beautiful beaches than the mainland (all of the most spectacular beaches in Italy and Spain are on the islands).

2) Fast moving cold currents (upwelling) such as those that move along the Pacific Coast of the Americas from colder latitudes seem to make the sea rougher and darker. This is why the West Coast of the Americas has nothing like the Caribbean in terms of clear waters.

3) Temperature must also be a big factor. Since there are very few clear water beaches above 40 degrees latitude, except maybe the Scilly Islands off Britain, but those are islands (see point 1).

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LF-TX

As for the south Texas coast, I’ve personally noticed that surf is a huge factor as to weather or not you’ll see clear water or not. Also the type of sand affects clarity here as well. When there is a lot of surf, obviously the sand gets kicked up and it makes the water a little nasty. Even on days with a lot of surf, if you look down between wave swells, the water is clean enough for you to see your feet. And when there is little to no surf, the water clarity (clarity, not color) is almost comparable to that in Florida. While not an everyday occurrence, every other trip to South Padre Island will give you water like this. I remember one time when me and my family went over to the island, it was a very cloudy day with little to no air and minimal rain. The water was absolutely beautiful! The water was a dark green blue from the sky’s reflection and the waves were almost like those you see on a LAKE- little to almost none at all. We were in about 4-5 ft of water and you could still see your body through the water. It’s strange how rainy weather systems can either calm the waves or absolutely enrage them. 

Now the sand on the island, while bright to the human eye, isn’t the whitest there is. If you are to reach into the water and take some sand and compare to the sand in the dunes, the wet sand is significantly more darker. I’ve came to my conclusion because on my first trip to Miami Beach, I noticed that the sand was a lot rockier and pebble like near the water - and it was a white/grey color. Even when it was wet, it was still a bright grey/ white color. The result: beautiful, crystalline water. Now with the sand at SPI, it’s not as bright and much much much more soft to the touch than the sand I felt in Miami. So since the sand under the water at SPI is much more darker when it’s wet, the water is only gonna reflect its dim color. But the water in reality is very very clear and clean. Again, like mentioned, when surf allows. 

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