Trophic State in Estero Bay- Georgia Lombardy

Estero Bay was once oligotrophic, meaning it had a low nutrient supply, generally low algae mass, and a high amount of dissolved oxygen. There are currently abundant signs that the Bay is now eutrophic. This means there is now an overfed bay with a high nutrient supply, high algae biomass, and a low amount of dissolved oxygen. This week we have encountered a diminished amount of seagrass with an increased number of epiphytes, macroalgae, and phytoplankton. All of these are signs of a eutrophic state. Along with these increases, there was also a great amount of cyanobacteria, which is present with high amounts of nutrients in the water. This environment is a concern for wildlife in the area because this decrease in the different types of macrophytes causes a decrease in habitat availability. The abundant amounts of cyanobacteria in the water can also cause an unhealthy and unlivable habitat for animals because of the toxins released. This trophic state change is also a concern for humans, this water quality associated with a eutrophic state is. Not ideal for those within living proximity. The cyanobacteria releases toxins that can have effects on humans such as breathing problems, or other skin infections if the water is introduced to an open wound. When the population around a body of water increases, it is associated with a eutrophic state. These large populations are bringing large amount of nutrients into the water mostly through fertilizer runoff and sewage waste. It is possible to diminish the amount of nutrients a population contributes to the water; this can be done through adding laws against using fertilizers on lawns. On the sewage side of things, it is possible to add more advanced steps to water purifying.

In the picture above, the sites visited most infected with cyanobacteria were Spring Creek Mouth and Estero River. The main cause is thought to be that both of these rivers are directly draining from multiple golf courses, those in which heavily use fertilizers on the green.

FGCU - Madison Wallwork

The trophic state of Estero Bay

When we visited the area around new pass we saw beautiful clear water that supported sea grasses, fish and invertebrates. This area is an oligotrophic environment, the same cannot be said for the rest of the bay. As development has increase and more people have moved to Fort Meyers, the nutrient loading in the bay has increased heavily. This is changing many oligotrophic sea grass beds into eutrophic areas. Sea grasses provide habitats and food for countless organisms, not to mention they provide cleaner water. Seeing a loss of seagrass meadows in Estero Bay is very bad news. It’s bad news for the wildlife, but it is also bad news for tourism. People want to boat and swim in places like new pass, not in places like the Estero river opening. If the excess nutrients just keep coming, there will be less and less places like new pass.

I think it is hard to suggest any management strategies when we all know how political everything is. What’s best for the bay would upset a lot of people and cost a lot of money. The excess nutrients has to stop and that would mean less people and better waste treatment. That would mean no green lawns. That would mean no fertilizers in the farms near Okeechobee Lake. With the mindset that our politicians have, I don’t see any of these things happening. To even propose these changes scientists would need clear research that shows the eutrophication of the bay over many years, and I’m not sure that information exists.

Eutrophication of Estero Bay - Elizabeth

A filamentous algal bloom similar to what was observed in Estero Bay

In our survey of Estero Bay, we saw enough filamentous cyanobacteria both in our field samples and floating in the water to conclude that the bay is currently undergoing eutrophication. Filamentous cyanobacteria grow rapidly in nutrient rich environments. It is capable of overgrowing macroalgae and seagrasses and is capable of emitting chemicals to defend itself against grazers and competitors. This means that it can’t be eaten by other animals and it inhibits the growth of primary producers who form the base of the food chain, so not only does is not contribute to the productivity of a habitat, but it can also potentially harm the food web by reducing the amount of food present for larger consumer species. This means that many species who normally inhabit the area will have to abandon the habitat in search of a more productive area. We saw evidence of this on our survey. Almost all the animals seen in all four sites were benthic, burrowing species. Almost no fish were present in at any of the sites and biodiversity was low. This problem can intensify when the filamentous algae eventually die. Eutrophication has been known to cause ocean dead zones. The excess nutrient levels in the water allow for an excessive overgrowth of algae. When the algae die, the decomposition process uses up the oxygen in the water, leaving dissolved oxygen levels in the water too low to support life and leaving behind what is known as a dead zone. This could potentially happen to Estero Bay if the problem is left unchecked over an extended period of time. 

Additionally, humans are also at risk in the presence of this cyanobacteria. Filamentous cyanobacteria is known to be toxic to people. It can cause skin, eye, and respiratory irritation and be toxic if ingested. This can be harmful to swimmers who unknowingly or accidentally ingest it, especially young children. An overgrowth of this cyanobacteria can potentially make the bay unsafe for recreational use. Several rivers empty out into Estero Bay. There rivers are lined with highly developed, urbanized land (neighborhoods, golf courses, etc). Fertilizer is an incredibly common way of keeping the lawns of homes, golf courses, and farms healthy. The problem starts when all the excess fertilizer drains into the rivers and gets dumped into the bay. All those excess nutrients feed toxic cyanobacteria and cause potentially dangerous algal blooms that harm animals, people, and the local ecosystem. Managing cyanobacterial growth along with the eutrophication problem will be difficult but it is possible to take action and make changes.

More land should be dedicated as nature reserves to reduce the amount of development and urbanization. Property owners and land developers should be encouraged to invest in alternatives to high maintenance grasses like native grasses that require less attention and stone landscaping that doesn’t require any water or fertilizer. Regulations should also be put in place to limit the amount of runoff that comes from large corporate farms in Florida that use exorbitant amounts of fertilizer in order to grow mass produced crops. Regulating where these farms are in relation to major bodies of water could reduce the spread of nutrients in Florida’s water systems. Following this, the public should be encouraged to buy locally grown produce when they can to reduce the demand for mass produced food. Furthermore, more research should be done into the lifecycles of these cyanobacteria in an effort to learn more about them and eventually find a way to stop their growth in the wild.

Eutrophication of Estero Bay- Denny

What evidence have you encountered so far this week that

suggests that the trophic state of Estero Bay is changing? Why is this a concern for wildlife and

humans in the area? What additional research and/or management strategies would you

recommend to better address the eutrophication of Estero Bay?Wha evidence have you encountered so far this week that

suggests that the trophic state of Estero Bay is changing? Why is this a concern for wildlife and

humans in the area? What additional research and/or management strategies would you

recommend to better address the eutrophication of Estero Bay?

What evidence have you encountered so far this week that suggests that the trophic state of Estero Bay is changing? Why is this a concern for wildlife and humans in the area? What additional research and/or management strategies would you recommend to better address the eutrophication of Estero Bay?

Estero Bay is an aquatic preserve located in Lee County, Florida. Though the Bay may be protected, anthropogenic influences on the Bay are evident. Examining an aerial map of the Bay shows urbanization along its entire length. Many rivers flow into Estero Bay transporting runoff of nutrients from private yards, commercial agriculture, and recreational areas have led to increased eutrophication of parts of the Bay. As a result, an increasing presence of macroalgae and cyanobacteria was observed. Additionally, seagrasses have declined across the Bay. This can be attributed to high light attenuation, which decreases the seagrasses primary source of energy. Tannins from mangrove leaf matter have also attributed to the decline. Areas that were sampled with increased levels of CDOM were observed to have low levels of species diversity.

Estero Bay

Eutrophication of Estero Bay will lead to numerous detrimental consequences for both wildlife and humans in surrounding areas. An increase in nutrient output may result in harmful algal blooms (HABs) forming in the surrounding ocean water. A particularly deadly HAB was observed off the coast of Southwest Florida in 2018. The bloom, or red tide, consisted mainly of the dinoflagellate Karenia brevis. Countless wildlife in coastal waters was killed due to this HAB. It is suspected that coastal wildlife, such as spotted eagle ray (Aetobatus narinari) and black skimmer (Rynchops niger), is still recovering from the deadly event. This event also affected humans directly by inflicting respiratory complications through toxins released in the air. HABs can also take an economic toll on affect areas by decreasing tourism and impacting fishing industries. 

Cyanobacteria observed under a compound microscope. Increasing nutrient levels allow these unappealing microalgae to flourish in eutrophic water.

More careful monitoring of Estero Bay is needed to get a complete scope of its changing trophic state. Baseline on nutrient levels, including nitrates and phosphates, chlorophyll, and CDOM is needed to establish concrete evidence of eutrophication of the Bay. Additionally, more research is needed on benthic species abundance and diversity throughout the Bay. This would allow researchers to observe the effects nutrient loading has on organisms in the environment. Educating the public on the adverse effects fertilizers have on marine ecosystems is also needed. Bridging the knowledge gap between scientists and the general public would be a first step in establishing a dialogue regarding a reduction in fertilizers and other sources of nutrients.