Worksheet 3 – Shoreline Florida Bay
Note: Before beginning this activity view the recorded lecture and read the paper by Lorenz located in the Week 4 folder.
Introduction
The activities this week involve looking at data concerning several ecological parameters in the southern Everglades. Changes in the flow of freshwater through the southern Everglades have had significant impacts on both wildlife and plant communities. Information taken from the Web must give the source of the information.
This worksheet is due Tuesday July 17 at 11:59 pm uploaded through the link provided in Canvas
Part I – Nesting success of wading birds
Lorenzo has reported in a study on the number of roseatte spoonbill nests found each year in the southern Everglades. A chart showing this data is shown below (From Lorenzo. Wetlands, 2014, 34 (Suppl 1), S201-S211).
The years of the survey are shown along the X-axis and the number of nests are shown along the Y-axis.
1. What is the trend shown in the number of nests?
The graph follows a specific trend; once it starts in the year 1974, although there have been a few increases, the overall number of roseate spoonbill nests have had an immense decrease.
2. Using the Web, summarize the feeding and nesting habits of the roseate spoonbill.
The roseate spoonbill spends a lot of its time in shallow water feeding. It sweeps its open bill from side to side in the water to sift up food like small fish, shrimp, mollusks, snails and insects. It has touch receptors in its bill that help it feel its prey. The roseate spoonbill’s pink color comes from the food it eats. Some of the crustaceans it eats feed on algae that give the spoonbill’s feathers their rosy pink color.
As for its nesting habits, the roseate spoonbill nest in colonies with egrets, ibises, and herons, typically on islands or over standing water. They nest in mangroves, Brazilian pepperbush, willows, sea myrtle, and other shrubs near the water. They tend to put their nests in the shadiest part of the tree or shrub, up to 16 feet high.
3. Given what you found out in #2, what environmental changes in the Everglades may be factors in the data trend that you see in the chart?
There are a few possible contributing factors that make the number of roseate spoonbill nests decrease. Some of these may be the varying salinity rates. This has a negative effect on this species’ food. This also has an effect on the trees where they make their nests in. The increase of salinity forces the trees to move inland, separating the roseate spoonbill from their source of food. As a consequence, this can force these animals to move to a more convenient location where their nests and food would be closer.
Ogden et al did a study on great white herons (Ecological Indicators 44 (2014); 148-163). The great white heron is a subspecies of the great blue heron. Its distribution is restricted to southern Florida and the Caribbean. Unlike the blue heron, the white heron is restricted to coastal and estuarine areas. Populations appeared stable from the 1960s until the 1980s at 1600-1800 breeding individuals, although they were much lower than populations in the 1920s. Ogden et al report that in the 1990s, numbers of birds began to decline, and since 2000, the annual count has not exceeded 500 birds.
1. How does the trend compare with that seen for the roseate spoonbill?
Similar to the roseate spoonbill, the number of great white herons has decreased greatly.
2. Using the Web, summarize the feeding and nesting habits of the great white heron
The great white heron feeds mostly by standing or walking in shallow water, waiting for fish to come near, then catching them with rapid thrust of bill. May feed in flocks or in association with other herons, cormorants, ibises, sometimes stealing food from smaller birds.
As for their nesting habits, the great white heron occasionally nests in isolated pairs, usually in colonies, often mixed with other wading birds, cormorants, Anhingas. In mixed colonies, Great Egrets tend to nest high. Male selects nest area and displays there, at first driving away all other birds, later courting females. Courtship displays include calling, circular display flight, stretching neck up with bill pointed skyward. Nest: Site is in tree or shrub, usually 10-40′ above ground or water, sometimes very low in thicket or marsh, sometimes up to 90′ high in tall cypress. Nest a platform of sticks, sometimes substantial.
3. Based on the study by Ogden et al, the following environmental factors can impact great white heron populations:
• Contaminant releases (mercury for example)
• Changes in freshwater inflow
• Alteration or loss of shorelines
• Altered air and water temperature
Based on what we have learned so far in this course, describe how these factors applied to the Everglades and how they might have impacted the great white heron populations.
Starting with the contaminant releases, in previous lab worksheets, we have studied and analyzed the roles that mercury plays in the Everglades and how it affects its biodiversity, animals, and even people. It is safe to say that contaminant releases that affect the water, consequently affecting the fish and animals that live in it, which is what the great white heron’s food, therefore it affects them directly. As for the changes in the water inflow, this affects their feeding grounds since it negatively affects their preys. Next, the alteration or loss of shorelines forces them to lose their nesting habitats. Lastly, the alteration in air and freshwater temperature, this also effects their distribution.
Part II – Introduction of exotic fishes
Alterations in drainage for the Everglades have connected the preserve to suburban and agricultural areas. Kline et al (in Wetlands (2014) 34 (Suppl 1); S175-S187) looked at the presence of exotic fish species in Taylor Slough and C-111 drainage areas in the southern Everglades. They also look a little further north in the Rocky Glades. The Rocky Glades are adjacent to the Redland Agricultural Area.
With the construction of the canals and their connectivity, deep water refuges were created that can provide habitat for fish through the dry season, even as the marsh dries out. Prior to the 1980s, very little water was returned to the Everglades from southern Miami-Dade canals. Beginning in 1999, restoration efforts targeted to rehydrate the southern Everglades is returning 28% of the water flows into Everglades National Park from canals in the southern part of the park.
African jewelfish, Mayan cichlids and pike killifish were the most widespread and abundant non-natives throughout the Everglades. Percent of non-native fishes were highest at the eastern boundary of Everglades National Park and declined westward.
In Figure b above, the stars show where African jewelfish were first seen in ENP in 2000. The solid circles indicate where the African jewelfish was sampled between 2000 and 2012.
1. What is the distribution of the African jewelfish in the Everglades based on this map?
This map indicates that the distribution of the African jewelfish in the Everglades have a good distribution around the entire grounds of the Everglades, but they mostly come together in the center of it.
2. What was the likely source of introduction of this fish into the Everglades?
The most likely source of introduction of this fish into the Everglades is probably the canals along with the trade of exotic animals in the state of Florida.
3. Based on the feeding habits of this fish, what might be its impact on native fish species in the Everglades?
The African Jewelfish has very similar feeding habits with the native fishes of the Everglades. This is considered a problem since there is a competition between these types of fishes and it can cause food shortages for these species.
In Figure h above, the stars show where the Asian swamp eel was first seen in the Everglades. The closed circles show where surveys have detected this species. The eel was not present in areas with open circles.
1. How do the distributions of the two species compare?
Although their distribution is not the same, both the African Jewelfish and the Asian Swamp Eel both made their way to the Everglades through the canals.
2. What was the likely source of introduction of this eel into the Everglades?
Like mentioned above, the introduction of the Asian Swamp Eel, as well as the African Jewelfish were probably through the canals that lead to the Everglades.
3.Based on the feeding habits of the swamp eel, what might be its impact on native fish species in the Everglades?
Similar to the relationship that the African Jewelfish had with native animals, the Asian Swamp Eel has the same feeding habits as the native animals that live in the same area that these eels do. This forces them to engage in a competition of who eats first and who finds food first leaving other species foodless and more likely to die.
Part III. Loss of Florida Bay Seagrass Beds
With the extensive human modifications of the Everglades, such as the construction of the Tamiami Trail, freshwater flow to Florida Bay has been significantly reduced. With the summer heat and high rates of evaporation, water temperatures rise and salinity increase to levels above that of ocean water. Extensive seagrass beds in Florida Bay are dying.
The diagram below shows the interconnections among the services provided by different ecosystems in the coastal zone. The services are shown in the bottom of the diagram by the color-coded arrows. If seagrasses were no longer part of the ecological structure of Florida Bay, what would be the impact on coral reefs, mangroves and communities on the nearby land? How would people living in southern Florida notice the loss of the seagrass communities?
Sawgrass has numerous jobs starting with binding sediments, absorbing inorganic nutrients, exporting organic material and nutrients for nearshore and offshore food webs, exporting invertebrate and fish larvae, and the task of being fish and invertebrate habitats. If sawgrasses were to disappear from the ecological structure of South Florida, it would have a domino effect on all of these things that it is responsible for. All of these factors mentioned above will have a direct negative impact on the mangroves and coral reefs. By all of these factors being stripped away from the ecosystem, besides the effects it has on the mangroves and coral reefs, it will also have a negative impact on the community living in the southern part of Florida. There will be a clear lack of sediments, nutrients, and freshwater discharge.
Part IV: Reflection
What did you learn about the Everglades from this exercise?
Any invasive species can propose big threats to the place that its invading. These types of species are not constrained by natural factors that existed in their native habitats, other native species, diseases, or predators. They can have alterations on natural areas, resulting in economic, environmental harm, or negative effects in human health. Sadly, the Everglades has many invasive species that are threatening the native species, and their surroundings. Both the African Jewelfish and the Asian Swamp Eel are just two of so many more that propose a threat to the life in the Everglades.
Besides invasive animals, I learned a lot about different factors such as contaminant releases, changes in freshwater inflow, alteration or loss of shorelines, or alteration of air and water temperature can have severe negative effects on native animals in the Everglades as well as their habitats and surroundings.
Lastly, I learned about the relationships between offshore water, coral reefs, sawgrass, mangroves, and land. Very detailed information was provided on the roles that each one partakes in the life of one another and how they would be affected if one of them were to be stripped away from the South Florida ecosystem.