Over the last few weeks, I have received several questions and comments on, and about, the eastern indigo snake. I was curious as to why so many in such a short time – maybe a public television program on them or something? Not sure, but it is an amazing snake and I like to talk about them. So, let’s talk about them.
The eastern indigo (Drymarchon couperi) is the longest native snake found in North America. It reaches a length of 9 feet and can weigh up to 11 pounds. It is beautiful. A shiny, iridescent black, with smooth scales that give a glossy look and emits beautiful patterns of color when the sun reflects off it that resembles the sheen you see when gasoline is spilled on water. This beautiful coloration, being nonvenomous, and docile attitude made it very popular as a pet – except that it can reach up to 9 feet long.
The eastern indigo snake.
Photo: Molly O’Connor
Their habitat of choice are high sandy ridges along the extreme southeastern United States. These ridges are covered with longleaf pine or turkey oak trees and provide enough space, hibernacula, and food to support them. Though a point of origin has not been published, the historic range suggest a possible origin in Florida. It has been suggested that there were once two distinct genetic forms of indigo snakes, one existing along the Gulf coast and another along the Atlantic coast. It appears there was a climatic barrier separating the two which no longer exist and today it is believed that there is only one species in existence now. The historic range of the snake included extreme southwest Mississippi, extreme coastal Alabama, extreme coastal Georgia, and all of Florida. The most recent range shows the snake exists across the entire Florida peninsula and some portions of southern Georgia but does not include all of Georgia’s historic range. It may be extirpated in the Florida panhandle, with a few rare reports, and believed to be completely extirpated in southern Alabama and Mississippi.
Indigos live mainly solitary lives with large home ranges that can extend hundreds to thousands of acres. Males have larger home ranges than females. Indigo snakes are diurnal and forage for their food rather than sit and ambush as many snakes do. Their diet consists of a variety of species, but diet studies show that rodents, frogs, small turtles, and snakes make up the bulk of their prey. It also includes species of venomous snakes like the eastern diamondback and copperhead.
Indigo snakes move between upland and lowland habitats during the warmer months. During the winter months they are closely associated with gopher tortoise burrows where the temperature can range between 45F and 88F and average 54F. They often emerge on sunny winter days to bask but do not move too far from the burrow. It is not known how long indigos live in the wild, but they have lived as long as 25 years in captivity.
During the 20th century the population of these snakes began to decrease. As is often the case, the loss of suitable habitat was a big problem. Longleaf pine forests where no prescribed burning was occurring as frequently as they had historically, the understory altered the habitat to a point where indigos could not support themselves. This also led to the decrease in gopher tortoise populations along with their burrows in which the indigos needed. The harvest of gopher tortoises as food and pets also decreased the number of burrows and thus the number of snakes. Often people would pour gasoline into the burrows to get the tortoises out and this led to the death of many indigos. And then there was the collection of the snakes for the pet trade. Another problem was that they are snakes. An eight-foot snake crawling around had little chance of escaping the wrath of scared humans.
The eastern indigo snake is the largest nonvenomous snake in the southeast.
Photo: Molly O’Connor
Today they are completely missing in Mississippi, Alabama, and the Florida panhandle. They are listed as an endangered species under the Endangered Species Act, and there are attempts to restore their populations in Alabama and the eastern Florida panhandle. Though there are occasional reports from the panhandle, there have been no verified records of the eastern indigo in the western panhandle since 1999. We would like to see this animal return but to do so, the habitat will need to be restored, and head starting (releasing captive bred snakes) may be needed as well. Though they are large, they are harmless to humans and actually provide a needed service by controlling the populations of venomous snakes in our region. I for one would love to see them return.
I recent took my granddaughter on a dolphin tour out of Pensacola Beach. It was amazing. It was a cool October morning, not a cloud in the sky, the winds were calm, the water crystal clear due to the lack of rain over the past few weeks, and the dolphins were out.
They are amazing animals and always seem to grab your attention no matter how many times you see them. I was a student at Dauphin Island Sea Lab from 1980-81 and taught there from 1985-1990. No matter how many times we heard “dolphins” when out on one of the research vessels, everyone had to run over to look. People do enjoy seeing dolphins. There is just something about them.
A group of small dolphin leap from the ocean.
Photo: NOAA
During the tour at one location, we saw a group of them (a pod) feeding on fish in the shallow water. They would roll and chase, you could see the sand being kicked up from the bottom as they did. At another location we saw them in breeding mode. Slower moving, caressing, fluke slapping as they turned all around in the water near us. The tour guide told us all sorts of dolphin facts, and some great jokes to go along with them. It was a good program, and my granddaughter was loving it.
She looked over at me at one point and said, “dolphins use to walk on land”. I responded that actually their ancestors did. Dolphins, as we know them, were very much aquatic animals. This led to thoughts on other dolphin questions I have heard over the years.
What is the difference between a dolphin and a whale?
Size… and in some cases teeth.
All whales and dolphins are in the mammalian order Cetacea. Mammalian orders are divided based on the type of teeth they have. Cetaceans are homodonts, meaning they have only one type of tooth. For the toothed whales, these are canines, they lack the molars and incisors that many other mammals have. But some have no teeth rather a specialized fibrous material called baleen, similar to the bristles of a broom, with which they can filter plankton from the water.
There are over 90 species of cetaceans in the world’s oceans, 21 of those are known from the Gulf of Mexico. In a recent published survey by the National Marine Fisheries Service, most of the cetaceans in the Gulf of Mexico are of the toothed whale variety and most occur beyond the continental shelf (which is between 60 and 140 miles south of Pensacola). The only baleen whale in their report was the Byrde’s Whale (Balanopatera edeni). They estimate about 33 of these whales based on their transect surveys and all of these were found beyond the continental shelf between Pensacola and Apalachicola Florida. The largest of the toothed whales reported was the sperm whale, which can reach over 60 feet. They estimate 763 sperm whale in the Gulf, and they were found across the basin beyond the continental shelf.
But it is the bottlenose dolphin (Tursiops truncatus) that we see on the dolphin tours. This is a relatively small toothed whale, reaching lengths of 13 feet, though most in the Gulf region are less than 10 feet. They are the most abundant and most frequently encountered cetacean near shore and within the estuaries and seem to prefer these shallower waters to the open Gulf beyond the shelf. The National Marine Fisheries Service divides them into stocks based on their geographic distribution. They report 37 different stocks of bottlenose dolphins in the northern Gulf. These are divided into western, eastern, and northern stocks, and then subdivided into estuarine stocks. There are separate stocks for the Perdido Bay and Pensacola Bay groups. This report indicated the stock size for the Pensacola and Perdido Bay dolphins was unknown, though our tour guide indicated there were about 250 in the Pensacola Bay stock. The National Marine Fisheries Service did report about 179 dolphins in the Choctawhatchee Bay stock. The reports estimated over 51,000 individuals for the northern Gulf.
Though not listed as endangered or threatened by the Endangered Species Act, there is some concern on the smaller estuarine stocks and so they have been labeled as “strategic”. There has been fishery related mortality with these dolphins in our waters, primarily with longlining and otter trawl operations, but losses are less than four animals/year and do not seem to be impacting their populations.
What is the difference between a dolphin and a porpoise?
Though many associate the long beak as a dolphin, there are dolphins with short snouts. Killer whales are actually large dolphins. The answer goes back to the teeth, as it always does when classifying mammals. Dolphins have conical shaped teeth where porpoise have more spade shaped ones.
How smart are dolphins?
As everyone knows these are highly intelligent animals. They use an audible form of communication that includes squeaks, clicks, and whistles, to keep the pod together. Researchers have discovered that these audible sounds have a sort of “accent” to them that tells dolphins which pod the dolphin communicating is from. This appears to be very important being that dolphins from one social pod may not accept others from different one. I remember in 1993 when a group of five pantropical spotted dolphins stranded on Pensacola Beach. There were four adults and one 3-month year old in the group. After failed attempts to return the dolphins back to the Gulf, it was decided to transport them to a quarantine area near the EPA lab on Pensacola Beach. There was a virus spreading through some European populations and they did not want to risk taking them to the Gulfarium. In route three of the four adults passed away. The remaining adult was named Mango and the juvenile was named Kiwi. After a period of time in quarantine Mango passed away leaving on the young Kiwi. There was a move to return Kiwi to the wild but some of the dolphin experts on scene told me the likely hood of a different pod accepting Kiwi was a risk, and finding her original pod was very unlikely. After determining the dolphin did not have the virus of concern, they decided to move her to the Gulfarium in Ft. Walton Beach, where she lived the rest of her life.
How does dolphin echolocation work?
Echolocation is different than communication, in that it is inaudible. As with communication, the sounds are produced by expelling air through the blowhole. In the case of communication, there is a muscle that partially closes the opening of the blowhole producing the sounds we hear. In echolocation this is completely closed, and the sound waves are moved through a fat filled melon near the head. The shape and density of the melon can be changed by the animal to produce different frequencies of sound but all inaudible to our ears. These sounds are emitted through the melon into the environment, where they contact something and “echo” back to the dolphin. These echoes are received in a fat filled cavity of the lower jaw and transferred to the brain – where the animal is then made aware of the object out in front of them. Some studies suggest that it may be more than knowing there is an object, they may be able to distinguish different kinds of fish. Though it is most effective within 600 feet, studies show their range may be up to 2000 feet. Studies have also shown that some species of toothed whales can alter the frequency of these echolocated sounds to stun their prey making them easier to catch.
Dolphins are amazing animals.
They live between 30 and 50 years in the wild. During this time, they form tight social groups, feed on a variety of prey, and produce new members every 2-3 years. There is so much more to the biology, ecology, and social life of these animals and we recommend you read more. Once you understand them better, we also recommend you take a dolphin tour to view these amazing creatures.
In the invasive species world, we talk of “Early Detection Rapid Response” (EDRR). These are invasive species that are currently not in our area, or are in very low numbers, but pose a potential threat. One of these is the Cuban treefrog.
As the name implies, Cuban treefrogs are from Cuba, and arrived in Florida around 1920 mostly likely in cargo ships. With the tropical climate of south Florida, the frogs did well and began to multiple and disperse north. At the beginning of 2022 there were 1,953 records of Cuban treefrogs in the U.S. Currently there are 2,462. There were few records in the Florida panhandle, now there 45 records from 11 of the 16 panhandle counties. They are spreading.
Photo by: Dr. Steve Johnson
In the past many of the invasive species that invade south Florida could not tolerate our winters. That is changing, and we are seeing more here than we have in the past. We have had one off records of Cuban treefrogs from our area over the years but recently there were reports of possible breeding pairs in Panama City, reports from the Crestview area, the Pensacola area, and several from the Milton-Pace area. Just recently they were found at one of the county buildings in Escambia County, in downtown Pensacola, and now near Gulf Breeze. Again… they are coming.
How would you know one when you see it?
First, they are treefrogs. Treefrogs differ in have toe pads at the end of each toe. Second, the adult Cuban treefrogs are much larger than the natives. Most of our native treefrogs are no more than two inches in length. Cuban treefrogs can reach six inches. The juveniles can be distinguished by looking at their belly. The skeleton appears blue through the skin. The skin between the eyes is fused to the skull (will not slide if rubbed with your thumb), and their eyes are reddish in color.
What do I do if I see one?
First, report it to the national database EDDMapS (www.EDDMapS.org). Second, if you are willing, humanely euthanize it. The most humane way to do this is to numb the nervous system first. This can be done by rubbing oral gel in the stomach or cooling them in a cooler with ice. Then they can be frozen.
Why are they a problem?
By definition invasive species DO cause problems. In this case Cuban treefrogs they are known to consume native frogs, wiping them out of many areas in the state. Like most invasive species, they reproduce at high rates and have few predators. One story came from a USGS biologist in Louisiana. He received a call from the Audubon Zoo in New Orleans stating they had ordered palm trees from a south Florida nursery for one of their exhibits. After a couple of days, the caretakers noticed numerous frogs they had not seen before. The biologist had an idea of what they might be and drove over. When he arrived, he decided to check the electric panel by the male restroom – Cuban treefrogs are known to reside here and sometimes short circuit systems. He opened the panel to find 30 Cuban treefrogs inside. Game on. New Orleans now has Cuban treefrogs.
By the way, this is a common method of dispersal – hitchhiking on plants from south Florida to nurseries and stores in our neck of the woods. Our winters are milder than they once were, and they seem to be overwintering and breeding. So, game on for us here in the panhandle as well.
If you think you may have a Cuban treefrog contact your county extension office to verify identification before you try to remove them. We certainly do not want harmless native species to get caught up in this management effort. If you have any questions, contact your county extension office.
As many of you know, I do programs with snakes and receive a lot of calls about them. But in recent weeks I have seen an increase in the number of calls and the number of encounters inside of homes. Though most of the home invasions have been in the garage, one found a gray rat snake in the cushions of her couch. In addition to the home invasion calls I have also seen an increase with venomous snake encounters and thought I would write about the possible reasons for this increase.
For many, snakes on the property is an unnerving situation.
Photo: Molly O’Connor
Of the 48 species of snakes found in Florida, 40 are found in the western panhandle – where I live. I decided to try a snake watch where they public would report what snakes they were seeing and what time of year. As of September 15, there have been 54 reports. 32 of those (59%) were reported in April and May. There are two explanations for this. One, it is the beginning of spring and the warm temperatures have them moving from their wintering habitats. Two, it is spring, and this is breeding season. When breeding hormones are flowing snakes are bolder during their movements and may expose themselves more often in the search for mates. It is also true that they have been in brumation during the winter when they feed very little and are need of food. This could make them move more than normal as well.
I divided the species into subgroups mimicking publications by Dr. Whit Gibbons. Based on this, in the western panhandle there are 7 species of small snakes, 8 mid-sized, 7 large snakes, 13 water snakes, 4 venomous snakes, and 1 non-native species. The encounters by these subgroups so far include 1 of the 7 small snakes (14%), 3 of the 8 mid-sized snakes (38%), 5 of the 7 large snakes (71%), 5 of the 13 water snakes (38%), 3 of the 4 venomous snakes (75%), and the non-native Brahminy Blind Snake has not been reported yet.
The eastern king snake is one of the larger snakes in the western panhandle.
Photo: Rick O’Connor
The high percentage of large snake encounters makes sense because they are – well… large and easier to see. The explanation for the high percentage of venomous snake encounters is numbers. There are only four species to be found in the western panhandle. It does not take many encounters to get a high percentage.
Water snakes will be encountered only if folks are visiting local waterways and are relatively still while there. My guess is that most encounters were from basking snakes or ones swimming across a body of water in which the observer happened to be there. Most snakes will freeze and hide when they since we are near, and most are well camouflaged. There are plenty of people who visit local waterways where these snakes exist. The lower percentage of encounters with this subgroup does not mean they are not there; they were just not seen. Many reports come from fishermen who are relatively still in their boats while fishing. If you move, they stop. If you stop, they move – and more will be seen.
The banded water snake is one of the more commonly encountered water snakes.
Photo: Rick O’Connor
If you look at the encounters by species, we have found 17 of the 40 western panhandle species have been encountered so far (43%). There has been a total of 54 encounters. Most, 13 (24%) have been with the southern black racer. This is a common large snake that does very well in human habitats like our neighborhoods and parks. It is active during the day and is fast enough to avoid trouble so may be more willing to expose themselves than other species. They also have a preference for more open spaces where they can be seen.
The southern black racer differs from other black snakes in its brilliant white chin and thin sleek body.
Photo: Jacqui Berger.
The second most frequently encountered snake so far this year has been both the eastern ribbon snake and the cottonmouth – 9 reports of both. The two account for 33% of all reports. Eastern ribbon snakes are fans of water and are often found along the edge of water bodies. With the increase in rainfall, many areas are wetter and encounters with this mid-sized snake have increased. They are most active during the day, especially on warm days, and this may also play a role in why they have been seen more often than other species.
The cottonmouth is an interesting story. Of the four species of venomous snakes, three of these have been encountered, and their encounters make up 15 of the 54 so far this year (28%). Of the 15 encounters, 9 were cottonmouths (60% of the venomous snake encounters, and 17% of all snake encounters reported). It is a commonly encountered snake. Seeing the cottonmouth as one of the top three encountered snakes in our area makes some people nervous. Like some of the other commonly encountered snakes, they like water – and there is plenty of it in the western panhandle. They prefer quiet water locations such as ponds, swamps, and lakes. They frequent water holes on golf courses and retention ponds in neighborhoods. It is also obvious that new developments are going up closer to wetlands than they did in the past – which would increase your chances of encounters. I recently completed a three-year survey of a gated community on Perdido Key where encounter rates were high. The interesting thing here is that barrier islands have little freshwater and are not classic cottonmouth habitat. But for decades there have seen an increase in encounters, which prompted many studies on how they are surviving. There are certainly natural freshwater systems on both Perdido Key and Santa Rosa Islands, but we have also created such habitats as well. It is possible that the cottonmouth is better suited to exploit these island habitats than other species of water snakes and thus are encountered more often. I plan to do more surveys for this, and other water snakes, on our islands beginning in 2023 and will let everyone know what we discover.
The cottonmouth is one of the more commonly encountered snakes in the western panhandle.
Photo: Bob Jackson
So, what has triggered the recent increase in home invasion and other snake encounters?
A week or two ago we experienced massive amounts of rainfall when a frontal system passed over. You might remember the flooding that occurred in Dallas TX and Jackson MS. That same system passed over us and generated a lot of rainfall. Like many animals, when water levels are up, they seek higher ground. During such events snakes are often reported in garages, porches, even in walls of homes. People were telling me they were finding them in the bathrooms, hallways, and even in the cushions of their couches. All of those reported were non-venomous, but cottonmouths are often encountered during these flooding events as well.
Other encounters can be explained as they were in the spring – the weather is changing. You may have noticed the recent decrease in humidity as a front passed over. It is not cold yet, but the lower humidity is signaling the oncoming fall season – and the snakes’ sense this as well. 15 of the 40 species (38%) in the western panhandle have a fall breeding season in addition to the spring one. All of the pit vipers breed in the fall and the rattlesnakes prefer fall breeding to spring. With the oncoming of the fall, males will be out seeking females. And as we mentioned earlier, hormones will force you to move more in the open than they may typically do.
This eastern diamondback rattlesnake was seen crossing a dirt road near DeFuniak Springs shortly after the humidity dropped.
Photo: Lauren McNally
We will continue our snake watch for the rest of the year and will give an update early in 2023. If you do see a snake, please let us know which species and which month you encountered it. If you have questions about snake encounters and snake safety, do not hesitate to contact your county extension office.
We all know how important oxygen is to all life. It is an element with the atomic number of 8, meaning it has eight protons and eight electrons. It has an atomic mass of 16 indicating that it also has eight neutrons. Oxygen is a gas at room temperature indicating that 70°F is VERY hot for this element. It is a diatomic molecule, meaning that it likes to combine with other elements and will combine with itself if need be. Oxygen is not actually O, it is O2 in nature. There is a triatomic form of this element, O3, which is called ozone – but that is another story.
Again, we know oxygen is much needed by living organisms. Well… by most living organisms – there are some microbes that can survive with little or no oxygen, but for the majority of the creatures we are familiar with, it is a must.
I have asked students why oxygen was so important to life. I usually get the answer “that we will die without it”. I respond by asking again – “but WHY do we need it? What does it DO?” And the response usually does not change – “we must have it or we will die”. There is no doubt that it is important. Being in an atmosphere with little or no oxygen sends our bodies into a “stress mode” gasping – but what DOES the element actually do for us?
Life is abundant on this planet due to the presence of oxygen.
Photo: Rick O’Connor
Oxygen is needed to complete the reaction we call respiration. For most, the term respiration means “breathing” and this would be correct – but it is more than that. It is an oxygen demanding reaction we all need to remain alive. In this reaction the sugar molecule glucose (C6H12O6) is oxidized to produce Adenosine triphosphate (ATP – C10H13N5O13P3). ATP is the “energy” molecule needed for cells to function – our gasoline. It fuels all metabolic reactions needed to sustain life. ATP cannot be consumed in food, it must be made in the cell and, as the reaction below shows, it requires sugar (which we get from food) and oxygen (which we inhale from the atmosphere) to work.
C6H12O6 + O2 –> CO2 + H2O + ATP
This reaction will produce 36 of the much-needed molecules of ATP with each cycle. It is known that in anaerobic respiration (the break down of glucose without oxygen) it will also produce ATP but not as much – only 2 molecules of it instead of 36. So, for most creatures’ aerobic respiration (with oxygen) is preferred and needed.
The primary source of oxygen on our planet is plants. This suggest that before plants existed there may have been little, or no, oxygen on in our atmosphere and scientists believe this was the case. When you look at the fossil records it suggests that prior to plants existence there was life (anaerobic life) but after plants the diversity and abundance of life exploded. Aerobic respiration seems to be the way to go.
As most know, plants produce oxygen in the process known as photosynthesis. This chemical reaction is used by the plants to produce the other needed respiration molecule glucose. Plants produce their own glucose and so are called producers, while other creatures, including animals, are consumers – consuming glucose in their food. The reaction for photosynthesis is –
CO2 + H2O –> C6H12O6 + O2
The excess oxygen produced in this reaction is released into the atmosphere by the plants. It makes up 20% of our atmosphere and this allows life as we know it to exist. Note… almost 50% of the oxygen in our atmosphere comes from single celled algae called phytoplankton that grow and exist at the surface of our oceans.
Single celled algae are the “grasses of the sea” and provide the base of most marine food chains.
Photo: University of New Hampshire
But what about aquatic creatures who do not breath the atmosphere you and I do? How do they obtain this much needed oxygen drifting in our atmosphere?
The answer is in dissolved oxygen. Oxygen, being a gas, is released into the atmosphere. Even the oxygen produced by submerged aquatic plants, like seagrasses and algae, release their oxygen as a bubble of gas which floats to the surface, pops, and is released to the atmosphere. To get that back to the creatures in the water who need it as much as we do, you have to “dissolve” it into the water.
To do this you must break the hydrogen bonds that connect water molecules to each other. Water is a polar molecule, and each molecule connects to each other like magnets using hydrogen bonds. These hydrogen bonds are weak and easy to break, but you must MOVE the water in order to do this.
The water molecule.
Image: Florida Atlantic University
Water movement, such as waves, currents, and tides, will do it. The more movement you have the more oxygen will dissolve into it. Waterways such as the rapids of mountain rivers and waterfalls will have high concentrations of dissolved oxygen – usually over 10 µg/L. For some creatures this could be too high – like an oxygen rush to the head – but for others, like brook trout, it is perfect. They do not do well in water with dissolved oxygen (DO) concentrations less than 10.
For most waterways the DO concentrations run between 4 and 10 µg/L. Most systems run between 5-7. Waterways with a DO concentration less that 4 µg/L are termed hypoxic – oxygen deprived – and many creatures cannot live at these levels. They are literally gasping for air. I have seen fish at the surface of our local waterways when the DOs are low gasping for much needed oxygen through the atmosphere. It is also the primary reason the great crab jubilees of Mobile Bay occurs. Low levels of DO in the bay will trigger many creatures to leave seeking higher DO in the open Gulf. But for some benthic creatures – like stingray, flounder, and blue crabs – they will literally run onto the beach gasping for oxygen. The fish known as menhaden are particularly sensitive to low DOs and are one of the first to die when concentrations begin to dip below 4. When you see the surface of a waterway littered with dead menhaden it typically means there is a DO problem.
Slick calm water diffuses/dissolves less oxygen.
Photo: Molly O’Connor
That said, some creatures, like catfish, can tolerate this and do not become stressed until the concentrations get below 2 µg/L. If they ever reach 0 µg/L (and I have seen this twice – once in Mobile Bay and once in Bayou Texar) the waterway is termed anoxic – NO oxygen. This is obviously not good. Some are familiar with the “Louisiana Dead Zone”. An area of the open Gulf of Mexico south of the Mississippi River where DO levels decline in the summer to levels where most benthic species, particularly shrimp, are hard to find. It seems “dead” – void of marine life. This is also a DO issue.
How – or why – do dissolved oxygen levels get that low?
There are three basic reasons to this answer.
The surface is still, and little atmosphere oxygen is being “dissolved”. We have all seen calm days when the water is as slick as glass. On days like these, less oxygen is being dissolved into the system and the DO concentrations begin to drop. But how low will they go?
The water is warm. Higher water temperatures hold less oxygen. As the water warms the oxygen “evaporates” and the DO concentrations begin to decline. If it is a warm calm day (like those during a high-pressure system in summer) you have both working against you and the DO may drop too low. Most fish kills due to DO concentrations occur during the hot calm summer days.
What is called biological oxygen demand. All creatures within the system demand oxygen and remove it from the water column. However, in most cases, atmospheric dissolved oxygen will replace for a net loss of zero (or close to it). But when creatures die and sink to the bottom the microbes that decompose their bodies also demand oxygen. If there is a lot of dead organic material on the bottom of the waterway that needs to be broken down, the oxygen demanding microbes can significantly decrease the DO concentrations. This dead organic material is not restricted to fish and crabs that die but would include plant material like leaves and grass clippings from our yards, organic waste like feces, food waste, the carcasses of cleaned fish, any organic material that can be broken down can trigger this process.
Now picture the perfect storm. A hot summer day with no wind and high humidity over a body of water that has heavy organic loads of leaves, dead fish carcasses, and waste. BAM – hypoxia… – low DO… fish kill… which would trigger more oxygen demanding decomposition and – more dead fish – a vicious cycle.
You have probably gathered that low dissolved oxygen concentrations can occur naturally – and this is true – but they can also be enhanced by our activity. Allowing organic material from our yards (grass clippings, leaves, and pet waste) to enter a body of water will certainly enhance the chance of a hypoxic condition and a possible fish kill – which would in turn fuel lower DO and poor water quality state for that body of water. The release of human waste (food and garbage, sewage, etc.) will also trigger this. And throwing fish carcasses after cleaning at the boat dock will too.
But there is another process that more people are becoming familiar with that has been a problem for some time. The process of eutrophication. Eutrophic indicates the waterway is nutrient rich. These nutrients are needed by the plants in order to grow – and they do. Particularly the single celled algae known as phytoplankton. These phytoplankton begin to grow in huge numbers. So, abundant that they can color the water – make it darker. As mentioned above, they produce a lot of oxygen, but at night they consume it, and with SO much phytoplankton in the water they can consume a large amount of DO. The DOs begin to drop as the evening wears on and before sunrise may reach concentrations low enough to trigger a fish kill. These phytoplankton will eventually die and with the large mass of organic matter sinking to the bottom, the oxygen demand to decompose them can trigger larger fish kills. These fish kills in turn demand more oxygen to decompose and the process of eutrophication can create a waterway with very poor water quality and a habitat unsuitable for many aquatic creatures. It is not good. This is the process that causes the Louisiana Dead Zone each summer. The nutrients are coming from the Mississippi River.
One of 39 stormwater drains into Bayou Texar that can introduce a variety of organic compounds that can fuel eutrophication.
Photo: Rick O’Connor
So, is there anything we can do to help reduce this from happening?
Well, remember some hypoxic conditions are natural and they will happen. But there are things we can do to not enhance them or trigger them in waterways that would otherwise not have them.
When raking your yard, place all leaves in paper bags for pick up. This keeps the leaves from washing into the street during rain events (and we are getting plenty of those) and eventually into a local waterway. The problem with using plastic bags is that the local utility who collects them can no longer compose this into mulch. You might consider using your leaves and grass clippings for landscaping yourself.
Watch fertilization of your yard. Many over fertilize their yards and the unused fertilizer is washed into the street and eventually into the local waterway. These fertilizers will do to phytoplankton what they were designed to do with your lawn – make them grow. Of course, not fertilizing your yard would be best, but if you must place only the amount, and type, your lawn needs. Your extension office can help you determine what that would be.
Pick up pet waste when you take your pets out to go to the bathroom.
If you have a septic tank – maintain it. You can also look into converting to a sewer system.
If you are on sewer – watch what you pour down the drain. Many products – such as fats, oils, and grease – can create clogs that cause sanitary sewage overflows when we have heavy rains (and we will have heavy rains). Our local utility in the Pensacola area offers the FOG program (Fats, Oils, and Grease). In this program you can pick up a clean 1-gallon plastic container to pour your fats, oils, and grease into. Once full, you bring it back and switch for a clean empty. To find where these containers bins are located near you visit the ECUA website – https://ecua.fl.gov/live-green/fats-oils-grease.
1-gallon container provided free to dispose of your oil and grease.
Photo: Rick O’Connor
Dissolved oxygen concentrations naturally go up and down, and sometimes low enough to trigger a natural fish kill but following some of the suggestions above can help reduce how frequently these happen and can help to make our estuary healthier.
