It sounds like one of those Sci-Fi thrillers where there is a giant asteroid heading to Earth and we need a special team led by Bruce Willis to save the planet. But in this case it is not a large rock, but a large mass of seaweed. And the threat is not a huge impact that would form tidal waves and atmospheric black out but large masses of seaweed covering the beaches up to a foot or more. Once on the beach, the mass of seaweed would begin to break down releasing odors and attracting insects that would not be popular with tourists – just as we get into the peak of tourist season around the state.
Mats of Sargassum on a south Florida Beach.
Photo: University of Florida
It is not something new, this has been a problem in south Florida for a few years now, but this year scientists can see the massive blob of seaweed heading this way and it is larger than before. They are expecting some beaches in Florida to be heavily impacted.
The seaweed in this floating mass is a brown algae known as Sargassum (Gulfweed). Like many brown algae’s, it is yellowish-brown in color and possesses small air bladders called pneumatocysts. These pneumatocysts allow large brown algae, like kelp, to stand tall like a tree in the water column – or, like Sargassum, to float on the surface where they can reach the much-needed sunlight.
Sargassum has small air bladders called pneumatocysts to help them remain afloat on the surface.
Photo: Florida Sea Grant
There are two species of Sargassum that are found in the South Atlantic: Sargassum natans and S. fluitans. They are not easily distinguished so most just say “sargassum”. These seaweeds form large floating mats that drift in the ocean currents. The clockwise rotation of the North Atlantic gyre creates a central point around which the currents spin that is calm – similar to the eye of a hurricane. Here, the sargassum collects in large masses and was noted in the logs of Christopher Columbus as the “Sargasso Sea” – a place to avoid for colonial sailors due to the fact there is little wind or current here.
The Sargasso Sea
Image: University of Florida
Mats of this algae creates an ecosystem drifting across the sea housing transient and residential species that have been the study of marine biologists for decades. The seaweed will get caught in currents that bring it close to shore where fishermen seek it out fishing for jacks or mahi-mahi. Baby sea turtles will use it as refuge until they are large enough to return to the shores of the continents and islands. It will at times get caught in currents that bring it ashore where beach combers sift through to see what they can find. As we mentioned, once on dry ground the seaweed begins to die releasing the odors of decaying sea life and attracting an assortment of insects. When this happens coastal communities will use tractors to drag and remove the smelly mats and deposit them in the local landfill.
In recent years, in south Florida, the amount of this seaweed has increased. The seaweed has formed large mounds on the beaches making beach combing an ordeal and the smell unbearable in many communities. Some of the Sargassum finds its way into the canals of the Florida Keys where it sits and decays, decreasing dissolved oxygen and causing a decline in abundance of some local marine communities. They have responded by removing the Sargassum to the local landfill but are experimenting with composting the material for fertilizing other plants.
Several researchers have experimented with the composting idea with some encouraging results. Some have found a use for it as mulch for coastal mangrove shoots that have lost much of their natural fertilizers due to coastal urbanization. There are problems with using this in some plant settings. 1) It could be too salty for some landscape plants. 2) There is the concern of the amount of arsenic present. Studies continue.
The recent large masses of Sargassum coming ashore began in 2011. What is causing this recent increase in Sargassum on the beaches? Researchers are finding the source of this material is not mats rotating off of the Sargasso Sea but forming in the belt of moving water between the North Equatorial Current in the south Atlantic and the equator itself. The exact cause of this increase growth is uncertain but could be linked to an increase of nutrients from regional rivers, like the Amazon, and from increased ocean temperatures due to climate change – both of these are exactly what seaweeds like.
This year the mass of seaweed seen from satellites is particularly large – over 5,000 miles. It is drifting in the currents heading for the Caribbean and Florida. It will most likely impact south Florida, but researchers do not believe the impact will be as large along Florida panhandle beaches. They will continue to monitor and report on the movement of this mass of seaweed over the course of the summer.
Health advisories are issued by state and local health departments when levels of fecal bacteria become too high for the public to safely enter the water. Sewage can be a source of these fecal bacteria. They can harbor pathogenic organisms that can cause of a variety of health problems. State and local health departments routinely monitor local waterways, particularly where people recreate, to assure the level of fecal bacteria is not unsafe. It is understood that the presence of fecal bacteria in waterways is normal, animals do go the bathroom, but excessive levels can be unsafe.
Closed due to bacteria.
Photo: Rick O’Connor
In the Pensacola Bay area, most of the human recreation areas near the barrier islands rarely have health advisories issued. Once every few years there is an issue at the sewage treatment facility on Pensacola Beach and an advisory is issued, or a sewage line is broken either near Santa Rosa Sound or Big Lagoon with the same results. But is very rare.
However, our local bayous are different. The neighborhoods are densely populated with old or outdated infrastructure, and how we manage these systems can cause problems as well. We are going to do a three-part series on what property owners can do to help reduce the number of health advisories issued in waterways where they are more common. In Part 1 we will look at how to maintain your septic system.
Septic systems were commonly used decades ago when city limits, and treatment facilities, were smaller. Many communities within our counties are on a septic system, and it falls on the property owner to properly maintain them.
Most understand how the system works, but for those who are not familiar – here are the basics.
When you flush your commode, take a shower, or wash your clothes, the wastewater leaves your house through a series of pipes and empties into a septic tank buried in your yard. These tanks are usually made of concrete and there are different sizes. A typical tank will be about 8 feet long x 4 feet wide x 6 feet deep and hold around 1000 gallons (again, sizes vary). The solid material settles to the bottom where it is broken down by living microbes. The oils and fats float to the surface forming a scum layer. The remaining wastewater settles in the middle of the tank and drains into a drain field through a series of perforated pipes.
The drain field should be made of less compacted soils to allow percolation into the surrounding environment. There is some physical, chemical, and biological treatment of the wastewater as it percolates, but only if the drain field is properly designed and located. For obvious reasons you should not (and most communities will not allow) have your drain field next to an open or public water system. In Florida it is required that the loose uncompacted soils must be no less than 24 inches above the wet/water table.
A conventional septic system is composed of a septic tank and a drainfield, where most of the wastewater treatment takes place. Image: US EPA
It has been found that if the septic system is placed in the correct location and maintained properly, it does a good job of removing pathogens from the wastewater. However, it was not designed to remove nutrients, which can still leach into waterways and cause algal blooms. And the presence of pharmaceuticals and household chemicals are not always removed, which can cause problems for aquatic wildlife. But to reduce health advisories they can work.
So…
How do we maintain our septic system so that it functions properly?
Watch what you pour down your drain. As mentioned above, many household chemicals and pharmaceuticals are not removed and become environmental problems when they leach from the drain fields into the local environment. Fats, oils, and grease (and even milk) can solidify and form the scum layer at the top of the septic tank. These solids can clog the lines running to the septic tank, or the drain field lines themselves. They can create back flows and could cause untreated sewage to back flow into your home. Our local utility offers the FOGProgram. In this program you can visit a local dispensing site (these can be found at ECUA’s website and there is one at the Escambia County Extension Office) to obtain as free 1-gallon plastic jug. Pour your bacon grease, oils, etc. into these containers. When full, return them to the dispensing location and swap out for a clean empty one. The service is free.
Watch how much water you use. As mentioned, septic tanks come in different sizes and are designed for a certain amount of water. “Flooding” of the system can occur if you are using more water than your system is designed for and this could include flooding of semi, or untreated, sewage.
The scum and solid layers of the tank need to be pumped out. It is recommended the septic systems are pumped once every 3-5 years, depending on the size of the tank. A pump out may cost you several hundreds of dollars, but a tank replacement is going to be in thousands – it is a good investment and will help reduce health advisories in local waterways.
Do not drive over your septic system, or drain field, with heavy vehicles. This could crack the tank and/or compact the soils within the drain field.
The FOG gallon containers are found in these metal cabinets placed around the county.
Photo: Rick O’Connor 1-gallon container provided free to dispose of your oil and grease.
Photo: Rick O’Connor
Studies have shown that a properly designed, properly placed, and properly maintained septic system will work well in reducing the presence of pathogenic fecal bacteria in our local waterways for up to 50 years. Note: like all things, even a good septic tank does have a live span. If you do not know the history of your septic system, we recommend you contact a certified professional to come do an assessment.
As always, if you have additional questions, do not hesitate to contact your county extension office.
Historically the average rainfall in the Pensacola Bay is around 60 inches per year. However, over the past 10 years that has increased to slightly more than 75 inches per year (see Table 1). The frequency of those levels over the past decade shows that most are between 60 – 80 inches but there have been two years with over 90 inches reported. In the last decade, nine of the 10 years had total rainfall above the historic mean for the area.
Along with the increase in rainfall has come an increase in development. This increase reduces the amount of the excess rainfall to percolate into the ground and recharge our aquifer. Instead, it is directed into stormwater projects to reduce flooding in the community. Some of this stormwater will eventually find its way to the estuary or the tributaries that feed the estuary. The question is whether this increase in freshwater run-off is enough to decrease the salinity of the bay system.
There are several restoration projects ongoing within the bay. Two of them Sea Grant has been involved in. One is monitoring the status of seagrass and the other is status of bay scallops. The species of seagrass in lower bay, such as turtle grass (Thalassia testudnium) and shoal grass (Halodule wrightii) require salinities to be at, or above, 20 parts per thousand. Bay scallops depend on turtle grass for their life cycle and also require the salinity at, or above, 20 ppt.
Citizen volunteers are assisting Florida Sea Grant by monitoring the salinity of the bay on a weekly basis.
Volunteers are trained to use a refractometer and asked to monitor their assigned beach once a week, reporting their results to Sea Grant and calibrating their instrument once a month.
We are asking our volunteers to continue to monitor until they have logged 100 readings.
Currently 21 locations around the bay are being monitored. Nine are in the Big Lagoon area, eight near downtown Pensacola, and four near Pensacola Beach.
12 of these sites are actively being monitored at this time, 3 have reached the 100-reading mark, and 6 have not been monitored in some time.
Note:
Our volunteers are monitoring the water at the surface near the beach due to ease of access. The seagrass and scallops we are interested in grow at the bottom and at depth. However, saline water is more dense than fresh, and it is assumed that the water on the bottom at depth is saltier than the data being found at the surface near the beach.
There are other agencies who are monitoring salinity at depth.
Data for Each Site as of the end of 2022
Table 3 – Salinity Mean, Median, and Mode from Around the Pensacola Bay Area
Water Body
No. of samples logged
Mean
Median
Mode
Bayou Chico
7
10
5
5
Bayou Grande
29
20
21
21
Bayou Texar
10
8
7
ND
Big Lagoon
15
23
20
20
Big Lagoon SP
51
16
15
14
Big Sabine
64
22
22
22
Bruce Beach
1
18
18
ND
Ft. McRee
4
21
21
19
Galvez Landing
65
22
23
22
Hawkshaw
24
16
15
15
Kees Bayou
100
20
21
14
Little Sabine
100
23
23
25
Lower Perdido Bay
100
16
15
20
Navy Point SE
21
17
17
20
Navy Point SW
22
16
17
10
Old River
36
23
23
25
Oriole Beach
51
25
25
25
Perdido Key SP
33
21
20
15
Sanders Beach
70
18
18
18
Siguenza Cove
11
22
21
21
Shoreline Park
10
25
25
25
TOTAL
824
19
19
19
Table 4 – Salinity Mean, Median, and Mode from the Big Lagoon Area
Water Body
No. of samples logged
Mean
Median
Mode
Big Lagoon
15
23
20
20
Big Lagoon SP
51
16
15
14
Ft. McRee
4
21
21
19
Galvez Landing
65
22
23
22
Kees Bayou
100
20
21
14
Lower Perdido Bay
100
16
15
20
Old River
36
23
23
25
Perdido Key SP
33
21
20
15
Siguenza Cove
11
22
21
21
TOTAL
415
20
20
19
Table 5 – Salinity Mean, Median, and Mode for the Downtown Pensacola Area
Water Body
No. of samples logged
Mean
Median
Mode
Bayou Chico
7
10
5
5
Bayou Grande
29
20
21
21
Bayou Texar
10
8
7
ND
Bruce Beach
1
18
18
ND
Hawkshaw
24
16
15
15
Navy Point SE
21
17
17
20
Navy Point SW
22
16
17
10
Sanders Beach
70
18
18
18
TOTAL
184
15
15
15
Table 6 – Salinity Mean, Median, Mode for the Pensacola Beach Area
Water Body
No. of samples logged
Mean
Median
Mode
Big Sabine
64
22
22
22
Little Sabine
100
23
23
25
Oriole Beach
51
25
25
25
Shoreline Park
10
25
25
25
TOTAL
225
24
24
24
Discussion
A glance at Table 3 will show all 21 bodies of water that have been involved in this project. Three of those, Lower Perdido Bay, Kees Bayou, and Little Sabine have reached the 100-reading mark.
For Lower Perdido Bay the mean salinity was 16 ppt ±5. The highest reading was 24 ppt and the lowest was 6 ppt. The median was 15 ppt and the mode was 20. These data suggest that this body of water would not support turtle grass or bay scallops, but it is not believed that historically lower Perdido Bay did. We would like to thank Bob Jackson for his effort on collecting these data.
For Kees Bayou the mean salinity was 20 ppt ±6. The highest reading was 31 ppt and the lowest was 5 ppt. The median was 21 ppt and the mode was 14 ppt. These data suggest that turtle grass and bay scallops could survive here. It is noted that Kees Bayou is a shallow basin located next to a highway and during intense rainfall the salinities could drop drastically to cause a decline of both target species. We would like to thank Marty Goodman for his effort on collecting these data.
For Little Sabine the mean salinity was 23 ppt ±4. The highest reading was 30 ppt and the lowest was 12 ppt. The median was 23 ppt and the mode was 25 ppt. These data also suggest that both turtle grass and scallops could survive in Little Sabine, and there are records that scallops were once there. Turtle grass exist there now. We would like to thank Betsy Walker and Liz Hewson for their efforts on collecting these data.
The Big Lagoon Area
These data suggest that most of the sampled areas could, in fact, support both turtle grass and scallops, and there are records that they have supported both in relatively recent years. One note of interest is the lower salinities near Big Lagoon State Park. Most of the sites have data at 20 ppt or higher – except Lower Perdido Bay (understandable) but we are not sure why the numbers are below 20 ppt. at the state park. We would like to thank our active volunteers in the Big Lagoon area Jessica Bickell, Glenn Conrad, John Williams, and Emogene Johnson for their effort in collecting these data.
The Downtown Pensacola Area
These data suggest that this area of the bay would not support turtle grass nor bay scallops. But historically they did not. Seagrass does exist in these bodies of water but much of it is widgeon grass (Ruppia maritima) which can tolerate lower salinities. We would like to thank our active volunteers for the downtown area Tim Richardson and Glenn Conrad for their efforts in collecting these data.
The Pensacola Beach Area
These data suggest that Santa Rosa Sound could support, and do support, populations of turtle grass and scallops. During our scallop searches conducted in July we have found one live scallop in Big Lagoon and two in Santa Rosa Sound over the last six years. Again, these data suggests that all of these locations could do so with the highest salinities in the bay area based on these data. We would like to thank our active volunteers in the Pensacola Beach area Ann Livingston, Gina and Ingo Hertz, and Holly Forrester for their efforts in collecting these data.
Though we have not reached the targeted 100-readings for most of our sites, these early results suggest the rainfall may not be lowering the salinity. We will continue to monitor until we do reach the 100-reading for each and have a better idea.
We are seeking new volunteers. The water bodies needing help are Bayou Chico, Bayou Texar, Big Lagoon, Bruce Beach, and Sanders Beach. If you are interested contact me at roc1@ufl.edu
October has been designated as Coastal Dune Lake Appreciation month by Walton County government. Walton County is home to 15 named coastal dune lakes along 26 miles of coastline. These lakes are a unique geographical feature and are only found in a few places in the world including Madagascar, Australia, New Zealand, Oregon, and here in Walton County.
A coastal dune lake is defined as a shallow, irregularly shaped or elliptic depressions occurring in coastal communities that share an intermittent connection with the Gulf of Mexico through which freshwater and saltwater is exchanged. They are generally permanent water bodies, although water levels may fluctuate substantially. Typically identified as lentic water bodies without significant surface inflows or outflows, the water in a dune lake is largely derived from lateral ground water seepage through the surrounding well-drained coastal sands. Storms occasionally provide large inputs of salt water and salinities vary dramatically over the long term.
Our coastal dune lakes are even more unique because they share an intermittent connection with the Gulf of Mexico, referred to as an “outfall”, which aides in natural flood control allowing the lake water to pour into the Gulf as needed. The lake water is fed by streams, groundwater seepage, rain, and storm surge. Each individual lake’s outfall and chemistry is different. Water conditions between lakes can vary greatly, from completely fresh to significantly saline.
A variety of different plant and animal species can be found among the lakes. Both freshwater and saltwater species can exist in this unique habitat. Some of the plant species include: rushes (Juncus spp.), sedges (Cyperus spp.), marshpennywort (Hydrocotyleumbellata), cattails (Typha spp.), sawgrass (Cladiumjamaicense), waterlilies (Nymphaea spp.), watershield (Braseniaschreberi), royal fern (Osmundaregalis var. spectabilis), rosy camphorweed (Pluchea spp.), marshelder (Ivafrutescens), groundsel tree (Baccharishalimifolia), and black willow (Salixnigra).
Some of the animal species that can be found include: western mosquitofish (Gambusiaaffinis), sailfin molly (Poecilialatipinna), American alligator (Alligatormississippiensis), eastern mud turtle (Kinosternonsubrubrum), saltmarsh snake (Nerodiaclarkii ssp.), little blue heron (Egrettacaerulea), American coot (Fulicaamericana), and North American river otter (Lutracanadensis). Many marine species co-exist with freshwater species due to the change in salinity within the column of water.
The University of Florida/IFAS Extension faculty are reintroducing their acclaimed “Panhandle Outdoors LIVE!” series. Come celebrate Coastal Dune Lake Appreciation month as our team provides a guided walking tour of the nature trail surrounding Western Lake in Grayton Beach State Park. Join local County Extension Agents to learn more about our globally rare coastal dune lakes, their history, surrounding ecosystems, and local protections. Walk the nature trail through coastal habitats including maritime hammocks, coastal scrub, salt marsh wetlands, and coastal forest. A tour is available October 19th.
The tour is $10.00 (plus tax) and you can register on Eventbrite (see link below). Admission into the park is an additional $5.00 per vehicle, so carpooling is encouraged. We will meet at the beach pavilion (restroom facilities available) at 8:45 am with a lecture and tour start time of 9:00 am sharp. The nature trail is approximately one mile long, through some sandy dunes (can be challenging to walk in), on hard-packed trails, and sometimes soggy forests. Wear appropriate footwear and bring water. Hat, sunscreen, camera, binoculars are optional. Tour is approximately 2 hours. Tour may be cancelled in the event of bad weather.
Part of our job at Extension is to help enhance science literacy. Often we write about natural history topics of interest to community that focus on interesting wildlife or an environmental issue or on topic we think the public should know more about. These articles have good science in them but are often written in a way as to not be too “sciencey” so that public will not be lost in the message. But sometimes there is a need for “sciencey” articles. Ones that may explain things using concepts and terms that go deeper than the public usually like to go. Not that the public cannot understand this, it is just too much like a science class from high school and not everyone enjoyed science when they were in school. A topic they may not enjoy. We are going to try a “sciencey” topic for this article.
What is salinity?
Most have heard the term and usually associate it with how much salt is in the water. They are not incorrect, and for the most part this definition will suffice when using it in conversation. But it actually goes a bit deeper than that. We will start with what is a salt.
Salt crystals used to de-ice roads. Photo: University of South Florida
A salt is the product of an acid and a base. For example, when you combine hydrochloric acid and sodium hydroxide you get sodium chloride (salt) and water.
HCl + NaOH – HOH (H2O) + NaCl
Most recognize sodium hydroxide as common table salt. But to better understand the point let’s combine sulfuric acid and sodium hydroxide.
H2SO4 + NaOH – H2OH (H2O) + NaSO4
Sodium sulfate (NaSO4) would also be a salt. There are numerous salts found in the environment. They are found in rock and mineral forms from land and the seafloor and will eventually make their way into the ocean – where of course they meet water.
Water has been described as the “universal solvent” and that is because water is a polar molecule and dissolves most things. What does “being polar” that mean?
We understand that “polar” means opposite ends, and in this case one end is positively charged, and the other is negative. This has to do with the alignment of the element’s hydrogen and oxygen in the molecule. To explain the alignment would require more chemistry than we want to go into here. But let’s just say the outer suborbital requires eight electrons to be considered stable – even that will take more discussion.
We know that atoms are made of protons, neutrons, and electrons. The protons and neutrons combine to form the nucleus of the atom while the electrons orbit around the nucleus like the moon orbits around the earth. Well, not exactly like that but that description will suffice to get the idea across. The orbit closest to the nucleus can only hold two electrons, any additional electrons will be forced to another orbit further away. If there are no additional electrons there are no additional orbits.
These orbits are identified by letters. The one closest to the nucleus is an s orbital. S orbitals can only hold two electrons. The next orbit out will have an s orbital and a p orbital. Again, the s can hold two, but the p can hold six. So, the second orbit can hold a total of eight electrons – 2 in the s orbital of the second orbit and another 6 in the p orbital of the second orbit (there is not a p orbital in the first orbit). If the atom has more than 10 electrons (2 in the first orbit and 8 in the second) then there will be a third orbit that has an s orbital (holding 2 electrons), a p orbital (holding 6 electrons) and a new orbital called d (which can hold 10 electrons). And so, it goes. Large atoms with lots of electrons will have lots of orbits with several orbitals holding a fix number of electrons. This may be getting more “sciencey” than we wanted, but we will continue to plow forward to help better understand salinity.
Here is the kicker. The s and p orbitals together hold a total of 8 electrons and the s and p orbitals of the orbit farthest from the nucleus MUST be filled for the atom to be stable. If they are not, then the atom is looking to gain or lose electrons to do so. Let’s look at water, we will start with oxygen.
Oxygen has the atomic number of 8. This means it has eight protons and eight electrons. Protons are positively charged, and electrons are negatively charged. Thus, oxygen has eight protons (+8) and eight electrons (-8). The charges cancel each other out and the atom is neutrally charged. But let’s look at how those eight electrons fill the orbits.
Remember the orbit closest to the nucleus only had an s orbital and can hold two electrons, which is does. But this leaves six electrons to place. The second orbit has an s and an p. S can only hold 2 electrons, so 2 of the 6 will go there. The p can hold 6, but now the oxygen atom only has 4 electrons left (after filling the first two s orbitals). So, it places those remaining four in the p orbital. But the p orbital is not full. It will hold 6 but only has 4. It has two empty orbitals and those MUST be filled. It needs 2 electrons from somewhere. (see below).
Filled s12 s2 2 p26
Oxygen s12 s2 2 p24 – it needs two electrons
Where does it find two electrons to become stable?
Let’s look hydrogen.
Hydrogen has the atomic number of 1. It has one proton (+1) and one electron (-1). Its orbit configuration would look like this:
Filled s12
Hydrogen s11 – it needs one electron to fill
Remember if you do not have enough electrons for a second orbit, there is no second orbit. BUT as you see the first orbit of hydrogen (which needs 2) only has 1 electron. It is not full.
Let’s look at another example to first understand how MOST atoms deal with this problem.
Sodium has the atomic number of 11. Eleven protons (+11) and eleven electrons (-11)
Chlorine has the atomic number of 17. Seventeen protons (+17) and seventeen electrons (-17). They would fill their orbits, and orbitals, as follows.
Na s12 s2 2 p26 s31
Cl s12 s2 2 p26 s32 p36 s41
You can see that the last sp for both are not full. However, if sodium “gives” the electron in s3 to chlorine then it’s s3 orbital is gone and the sp2 for the second orbit of sodium would be full – stable. Likewise, if chlorine “accepted” that electron its s4 orbital would be full – stable. And this is what happens. However, this throws the electronic balance off.
If sodium is (+11) (-11) and gives away an electron it is now (+11) (-10) – no longer neutral. It becomes positively charged (+1) and charged atoms are called ions (Na+1). Likewise, chlorine accepting the electron (+17) (-18) would form a negative ion (-1) (Cl-1). Opposite charges attract with Na+1 and Cl-1 combine to form NaCl – salt. This is known as an ionic bond. Two oppositely charged ions combining to form a compound.
Water is a bit different.
Hydrogen s11
Oxygen s12 s2 2 p24
You can see oxygen needs 2, but hydrogen does not have 2 to give AND if it gives the ONLY electron, it has it will no longer exist. So, it SHARES its 1 electron with oxygen. The hydrogen atom will allow its lone electron to orbit the last orbital of oxygen BUT it must circle back and orbit the hydrogen nucleus as well. To get the required 2 electrons that oxygen needs to fill its sp2 it will need another hydrogen atom to do so – hence H2O. When sharing electrons to form a compound we call this a covalent bond.
Now comes the alignment part.
To graphically illustrate how the electrons fill the last sp orbitals of an element they use what is called the electron-dot. It would be laid out as follows:
S **
p Na p if full would look like this ** Na **
p **
The first two electrons would fill the s orbital. Then any additional electrons filling the p’s BUT you would first place an electron in each p and then come back and fill (two max) in clockwise form. The number AND ALIGNMENT of the electrons would be represented by dots.
In the example just given – sodium – the atomic number is 11. The eleven electrons would be placed as follows
s1 – (2) s2 (2) p2 (6) s3 (1) The electron dot would look like *
Na
Chlorine (17) would look like this…
s1 (2) s2(2) p2 (6) s3(2) p3 (5)
**
Cl **
**
You can see the open space for one electron to fill this and complete the two for each. Sodium would GIVE it’s one electron to chlorine (having a full s2p2 with eight dots all around) forming an ionic bond known as sodium chloride (NaCl) or salt. The next inner orbit of sodium would have its sp orbitals filled and would be stable but charged due to having more protons than electrons.
Oxygen (8) would look like this…
s1 (2) s2(2) p2(4)
**
O **
*
This alignment would force the two hydrogen atoms SHARING electrons to do so NEXT to each other.
Water would appear like this…
**
H** O **
H **
The water molecule. Image: Florida Atlantic University
In the sharing of the electrons to form water the oxygen molecule holds the electrons longer than the hydrogen (it is larger). This makes hydrogen slightly positive and oxygen negative. Due to this alignment with both hydrogens at one end of the water molecule gives it a positive and negative end – it is polar – it has opposite poles – a positive and negative one. It acts like a magnet.
The first impact of this situation is that water molecules attach to each other. The positive hydrogen end of one water molecule attaches to the negative oxygen end of another. All of the water molecules bond together and form a lattice of water molecules – like they are all holding hands. These bonds are weak and can be easily broken if a creature is trying to swim through them, but attached they are.
A second impact is that they will disassociate (dissolve) ionic compounds that they come in contact with, like salts. The ionic bond we know as salt – sodium chloride (Na+Cl–) will dissolve in water. The positive ion Na+ is attracted to the negative end of the water molecule. The opposite is true for the chlorine ion.
So, what is actually “drifting” around in the water are dissolved ions – not the salts themselves. Which salts and ions are drifting in seawater? All of them. All 92 natural elements found on the planet are dissolved in seawater – not just sodium and chloride. It is true that the sodium and chloride ions make up about 85% of all the dissolved ions in seawater, but not all. So “sea salt” looks and taste like table salt but it is different.
Salinity then is the measure of dissolved solids (or ions) in the water – not exactly salt.
How salty is the water? What is its salinity?
We can measure this several ways.
Conductivity meter. Photo: Iowa State University
Being that you are measuring the amount of dissolved charged ions in the water you can use a conductivity meter. Conductivity is the measure of the ease of which an electric charge (or heat) can pass through a material. The more ions dissolved in the water the higher the conductivity. This can be measured easily with the conductivity meter. Though conductivity is NOT a measure of the amount of ions in the water, but rather the measure of how easily an electric current passes through the water, it is still very closely related to the amount (or salinity) and is often used (making corrections) to determine the salinity of the water.
Hydrometer. Photo: University of Queensland
Another method is measuring the density of the water. The more dissolved ions in the water the denser it is. A hydrometer is a glass tube filled with a fixed amount of lead shot with a calibrated stem (you can get them with different amounts of lead to measure salinity at a wider range). As you place it in the sample, the density of the water holds the hydrometer in specific position and you can read the salinity from the calibrated stem.
Refractometer
Playing off the density game. The denser the water is the more it will refract light passing through it. A refractometer is an instrument that uses a calibrated scale to measure salinity based on much light passing through refracts (or bends). The volunteers monitoring salinity in our citizen science project are using this method.
Salinity is measured in parts per thousand – parts of salt to 1000 parts of water. Using any of these instruments, or one called a salinity meter which works similar to a conductivity meter but is calibrated to salinity not conductivity, you can determine the salinity of the water.
0 parts per thousand (ppt, ‰) would be freshwater water.
35 ‰ would be seawater.
Salinities between 0 and 35 ‰ would be brackish water.
These values are not set in stone.
Many scientists argue that anything above 0 ‰ is not freshwater. I have read salinities in Perdido River as high as 4 ‰ and it did not taste like salt water. Some would say that up to 5 ‰ could still be considered freshwater – but again, not everyone agrees. One must also understand that in nature there are always SOME dissolved ions in the water. It is just their concentrations are SO low that our instruments cannot detect and give a reading of 0 ‰.
Likewise, the salinity of the Gulf of Mexico can run between 30 – 38 ‰, the average is 35 ‰.
Usually, the salinities in the lower parts of the Pensacola Bay system run between 20-30 ‰.
The bayous are typically between 10-20 ‰.
And the upper portions of the bay run between 0-10 ‰.
There are exceptions.
Bayou Chico usually runs between 0-10 ‰ but readings above 10 ‰ are found near the lower end of the bayou.
Perdido Bay is lower than Pensacola Bay. Lower Perdido Bay averages between 10-20 ‰.
Note: The tide plays a role in what the salinity is at any given moment. High tide brings in more saline water, to any system that experiences tides, and the salinity will be higher at that time.
For reasons we will not go into here, many of the plants and animals that call our waters home have specific salinities they prefer. There is a range they can tolerate, but also a smaller range they prefer. The biology of the upper and lower bays can be very different. The seagrass known as tape grass, or eel grass (Vallisneria) prefers low salinities, typically under 10 ‰, and are found in the upper reaches of the bay. Whereas shoal grass (Halodule) and turtle grass (Thalassia) prefer it above 20 ‰ and more common in the lower reaches. Some species, like turtle grass, have a small range of salinity they can tolerate and are called stenohaline species. Others, like shoal grass or widgeon grass (Ruppia), have a much broader range and can be found in many waterways within the bay system. These are called euryhaline.
Sea Grant is currently looking at the salinity across the bay area (from shore) to determine how (if at all) the excessive amount of rain we have been receiving in the Pensacola area in recent years is impacting the salinity of the system. As we described above, this could impact those stenohaline species who cannot tolerate it. We hope to conduct a more robust salinity monitoring project in the future.
Hopefully this was not too “sciencey” and that you learned something new about the salinity of our bay.
We used to find them here. I have heard stories of folks who could fill a 5-gallon bucket with them in about 30 minutes right by Morgan Park. An old shrimper told me that back in the day when shrimping in Santa Rosa Sound they often found scallops along the points. They would drop a grab and collect them for sale. This was when both commercial scallop harvest, and shrimping, were allowed in Santa Rosa Sound. Neither are today. There are numerous tales of large beds of scallops in Big Lagoon and scientific reports of their presence in both locations and in Little Sabine. I myself have found them at Naval Live Oaks, Shoreline Park, Big Sabine, and in Big Lagoon.
Bay scallops need turtle grass to survive. Photo: UF IFAS
But that was a long time ago. The reports suggest the decline began in the 1960s and today it is rare to find one. What happen is hard to say but most believe it began with a decline in water quality. A decrease in salinity and an increase in nutrients from stormwater runoff degraded the environment for both the scallops and the turtle seagrass they depend on. Overharvesting certainly played a role.
But they are not all gone. There is still turtle grass in our system and occasionally reports of scallops. They are trying to hang on. There have also been attempts to improve water quality by modifying how stormwater is discharged into our bay, though there is much more to do there. Each year Florida Sea Grant Agents at our local county extension offices provide volunteers an opportunity to survey our bay for both species. We have a program called “Eyes on Seagrass” where volunteers monitor sites with seagrass once a month from April through October. We partner with Dr. Jane Caffrey from the University of West Florida to assess this. We also hold our annual “Pensacola Bay Scallop Search” each July.
In the Scallop Search volunteers will snorkel four different 50-meter transects lines either in Santa Rosa Sound or Big Lagoon searching for scallops. These surveys are conducted at the end of July. There are 11 survey grids in Big Lagoon and 55 in Santa Rosa Sound extending from Gulf Breeze to Navarre. To volunteer you will need a team of at least three people and your own snorkel gear. Some locations do require a boat to access. If you are interested in searching along the north shore of Santa Rosa Sound contact Chris Verlinde at chrismv@ufl.edu (850-623-3868). If you are interested in searching along the south shore of Santa Rosa Sound, or Big Lagoon, contact Rick O’Connor at roc1@ufl.edu (850-475-5230).
Volunteers conducting the great scallop search. Photo: Molly O’Connor
Reminder, harvesting scallops in Escambia and Santa Rosa counties is still illegal. Please give them a chance to recover.
Our coastal dune lakes are even more unique because they share an intermittent connection with the Gulf of Mexico, referred to as an “outfall”, which aides in natural flood control allowing the lake water to pour into the Gulf as needed. The lake water is fed by streams, groundwater seepage, rain, and storm surge. Each individual lake’s outfall and chemistry is different. Water conditions between lakes can vary greatly, from completely fresh to significantly saline.
