Illustrated by the graphic below, the aquatic trophic structure has primary producers, primary consumers, mid-level consumers, and high-level consumers. Plankton, at the bottom of the aquatic trophic structure, are defined as small and microscopic organisms drifting or floating in the sea or fresh water, consisting chiefly of diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals (National Oceanic and Atmospheric Administration, n.d.). Like plants on land, phytoplankton perform photosynthesis to convert the sun’s rays into energy to support them, and they take in carbon dioxide and produce oxygen (National Oceanic and Atmospheric Administration, n.d.). Because they need the sun’s energy, phytoplankton are found near the water’s surface (National Oceanic and Atmospheric Administration, n.d.). Plankton cannot swim against a current which I figure, along with their small size, makes them easier to prey on.
The next graphic illustrates an aquatic trophic structure is actually a web rather than merely a chain. It also shows biodiversity gives consumers more gateways to receive nutrients. When there is algae, phytoplankton, and terrestrial plants/insects, there is more opportunity for nutrient acquisition as the type of species at each trophic level increases. At the highest level, the small mouth bass ends up with nine direct food sources. Notice, too, the smallmouth bass also consumes organisms such as the suckers and crayfish who two levels below the highest instead of directly under it. Further, the graphic illustrates cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores (Naddafi and Rudstam 2013). Since the smallmouth bass eats the herbivore stoneroller fish, the smallmouth bass impacts the primary producer algae. Therefore, predator biodiversity impacts producers just as much as producer biodiversity impacts predators.
Biodiversity increases stability of the aquatic trophic structure. Insofar as there is diversity of life forms in all levels of the system, the less a given aquatic food web relies on a certain species to maintain its structure. A study found interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels (Naddafi and Rudstam 2013). Additionally, the ocean food web shows the importance of having a diversity of forage fish for the high-level mammals and seabird species to feed on.
Leopold’s “The Green Lagoons” demonstrates the interplay between terrestrial and aquatic trophic structures. Terrestrial mammals feed on aquatic organisms. For example, Leopold said “families of raccoons waded the shallows, munching water beetles […] At every shallow ford were tracks of burro deer” (Leopold 2013, 126). He also illustrates it is difficult for the developer proposing to modify a natural wetland for inclusion in a golf course to not disturb the area’s trophic structure, explaining “as one flock filled up and left, another arrived, eager for their delectable stones. Of all the millions of pebbles in the green lagoons, those on this particular bar suited them best. The difference, to a show goose, was worth forty miles of flying” (Leopold 2013, 128). So, a developer would still be detracting from the trophic structure’s health by impacting some sections of the lagoon and leaving others untouched even if the two areas had similar components. Additionally, even areas that seem to be unimportant to the ecosystem’s function actually serve a purpose. For example, Leopold said “the dried-up mud flats bore an annual grass, the gain-like seeds of which could be scooped up by the cupful […] The deer and coons had opened the frozen fruits, exposing the seeds. Doves and quail fluttered over this banquet like fruit-flies over a ripe banana” (Leopold 2013, 128). Leopold also mentioned a water shortage at the lagoon and having to dig for sweet water (Leopold 2013, 129). If modifying the natural wetland for the golf course involved further depleting water supply, it would have a severe negative impact on the species in the area. Lastly, Leopold highlights a human being experiencing freedom in the midst of a thriving trophic structure raising flavorful cantaloupes is slightly lost when its developed instead of being a blank spot on the map (Leopold 2013, 130). Therefore, I would tell the developer a human being walking on the prospective golf course area now is going to feel different if the space is developed. Keeping the aquatic food web in tact as much as possible will bring a more fulfilling experience to all the species who inhabit the area.
Leopold, Aldo. 2013. Sand County Almanac & Other Writings on Conservation and Ecology. London: Penguin.
Naddafi, Rahmat and Lars G. Rudstam. 2013. “Predator Diversity Effects in an Exotic Freshwater Food Web.” PLOS ONE 8: e72599. doi:101371/jornal.pone.0072599.
National Oceanic and Atmospheric Administration. n.d. “What are Plankton?”. Accessed October 28. https://oceanservice.noaa.gov/facts/plankton.html
Comment by Professor Fenton Kay:
Great post and neat graphics, Mary. Leopold talks about cantaloupe farmers as the developers that killed his green lagoons. How might he approach the issue of a golf course instead of cantaloupes?
Michael Keiser created Sand Valley Golf Course with Aldo Leopold in mind, and it ended up being named the country’s best new course of 2017 by Golf Digest.
A key moment was when Kaiser asked the Field Museum of Chicago to survey the space. The scientific report described what would happen if the ecosystem was restored to a time before the planting of pine trees for their paper potential and suggested the developers read “A Sand County Almanac”. Keiser says he read Leopold’s book, which elicited visions of reemergent, cascading sand dunes as the central feature of a starkly beautiful natural terrain (Moe 2020). From there, he decided an ocean of prairie, sand and jack pines could compete with a course developed near any other body of water (Moe 2020). Keiser’s approach is aligned with Leopold’s as closely observing the space led to Keiser gathering knowledge about its evolution overtime.
In order to implement Leopold’s land ethic, it is important for a developer to thoroughly observe a place which leads to understanding its trophic structure and devising a plan accordingly. Much of a Sand County Almanac’s chapters entail Leopold grouping a set of wildlife observations into a thematic understanding of the place’s trophic structure. Leopold would advise a study to be conducted which would provide the developers with an inventory of existing wildlife communities and their habitat on the site, including areas of threatened or endangered species. From there, he would suggest the developers be sensitive about removing certain vegetation and critters that wildlife rely on. A comprehensive site survey would also include investigating soil characteristics and water availability. Leopold discussed how water being removed for melon farming was detrimental to preserving the aquatic trophic structure of the green lagoons. Considering golf courses require heaps of water for irrigation, I see him advising the course developers to approach its project by brainstorming alternative, economically logical water sources and constructing the course so its most active areas are away from the wetland.
The following article discusses case studies of how golf course planners have taken the land ethic into account during development:
Moe, Doug. 2020. “Michael Keiser helped create a golf course with Aldo Leopold in mind”. Madison Magazine. Accessed October 31.
Response by Professor Fenton Kay:
Mary, thank you for that information about the Leopold-influenced golf course. Things like that are really good to hear. I understand that more and more golf course developers are looking carefully at where they are and the biological community structure and history. That is good since golf courses seem to spring up rather like mushrooms wherever people are. I worked one summer as a field assistant on a lizard study. We traveled all over New Mexico and west Texas observing and collecting lizards for a chromosome study. We did a lot of work in the Permian Basin of Texas. At one place there, the oil workers had built a grassless golf course (it was all sand, not much water, and grass wouldn’t grow well). They used waste oil to make the greens. There was no runoff from that course.
Thanks for sharing your experience being on the lizard study. Sounds intriguing! I am a fan of seeing iguanas in Florida. What was the reasoning for selecting New Mexico and west Texas? Was it related to the chromosome study’s purpose? Also, lizards move fast! What was your method for collecting the lizards?
Response by Professor Fenton Kay:
Mary, the study was a post-doctoral research investigation of regional variation in the chromosomes of the lizard Uta stansburiana (DNA analysis didn’t exist at that time – 1970-71 – Chromosome studies were the hot ticket). The species is common throughout the western arid U.S., but there had been a previous study of the populations in the area we looked at, so there was a bunch of background data available. We noosed them when we could, but mostly we used a blowgun and darts. We also did some behavioral stuff on Urosaurus ornatus, a species related to Uta. And as sort of whipped cream, we discovered and describes a new species of Cnemidophorus in Laredo, TX. We named it C. laredoensis.
Comment by Jenny Murphy:
These really are some great graphics! And you really explained the various food webs well. I love that your example included sea birds. NOAA states that various disturbances such as contaminants and habitat destructions can affect sea birds to the point that can experience a complete breeding failure resulting in the overall long term survival and health of marine species (NOAA 2018).
NOAA. 2018. “What Threats Do Seabirds Face?”. Accessed October 30, 2020. https://oceanservice.noaa.gov/facts/seabird-threats.html#:~:text=Seabirds%20are%20impacted%20by%20a,%2C%20disturbances%2C%20and%20habitat%20destruction.&text=In%20some%20cases%2C%20disturbances%20can,ultimately%20may%20cause%20colony%20abandonment.
It was interesting to see sea birds included in a lot of the graphics I saw online. Along with Leopold’s description of the food web at the lagoons, it shows the aquatic trophic structure is not only composed of creatures living underwater. Through this class, I am noticing how bird migration patterns are becoming relevant in a variety of discussions. Bird migrations, as well as the factors contributing to it, definitely plays a role in understanding trophic structure. Even the fact birds can efficiently fly across an ecosystem impacts predator-prey relationships. I imagine flying is an advantageous trait in competition.
Comment by Amy Zobler:
Your point that someone would feel differently walking in the natural area compared to the developed course stood out to me. Assuming the developer could not be convinced to leave the natural area alone entirely and abandon their plans for the golf course, this could be a good way to convince him to protect the natural habitats and food webs as intact as possible. According to Audubon International, surveys have shown that “playing quality is maintained or even improved as a result of steps taken to manage a course in harmony with the natural environment” (Audubon International n.d.). I’ve seen many other studies that also support the link between mental health and being in nature. Although not as beneficial as leaving the area undeveloped, this could be a good compromise with the developer and environmental advocates.
Audubon International, n.d. “Fact Sheet: Golf and the Environment.” Accessed November 1, 2020. https://auduboninternational.org/wp-content/uploads/2019/03/GE-Golf-and-the-Environment.pdf.