What can we learn from the things in lakes?

This post is a part of a special series, written by undergraduate students in the University of Rhode Island’s Spring 2018 “Biology and Society” course. This course, taught by Dr. Lindsay Green-Gavrielidis, explores the intersection of biology and society. As part of the course, students wrote blog posts translating scientific articles related to ecology and society for a public audience.

 

About the Author

My name is Edith F. I am currently an undergraduate at the University of Rhode Island pursuing a Bachelors in Science in Biological Sciences. I’m a hard core New England sports fan and when I’m not cheering on the Patriots you can find me outside or inside with my nose stuck in a book!

 

 

 

Introduction

It is not hard to determine that we live in a time that is a heavily influenced by humans or as Alex Awiti describes it, the Anthropocene. It is a moment in time where humans have emerged as the dominant force that holds the power to build, destroy or reshape naturally occurring processes and environmental processes. Because we are the dominant force, we make the assumption that all these natural systems run on a command and control loop; meaning that no matter what type of stressor we apply on these systems, they will always go back to an equilibrium state (i.e. they will always find and maintain their balance). This assumption leads to the loss of uniqueness in these ecosystems; they become weaker because they are not given the time to rebuild fully. Is there a way that we can look at the ecological patterns and determine whether we can make them stronger and better equipped to handle human influence?

Strength and uniqueness of ecosystems: what does it all mean?

Community resilience is defined as the amount of disturbance a system can absorb and still remain within the same state of attraction. Because resilience is a measure of how strong an ecosystem is, it can help us understand the uniqueness of said ecosystem. If there is a massive disturbance and the ecosystem recovers in time, then the species will develop new adaptations that can increase the diversity of the upcoming generations. The way to maintain the resilience of ecosystems is to reduce the amount of resources that we use such as energy, land, and water, while at the same time minimizing human impacts like pollution, land destruction, and even loss of species. There are three ways to evaluate resilience: 1) measure the size of the disturbance that the system can endure and still maintain a steady state; 2) determine the level at which the system is able to recover and rebuild after disturbance and 3) estimate the ability for the system to evolve its adaptive abilities after a certain time has passed. Resilience is a key part to understanding the uniqueness of ecosystems (biodiversity), but how can lakes help us understand ecosystem resilience?

Photo of fishermen in Lake Victoria in an early morning. Image courtesy of Franklin Amuyloto.

Why is Lake Victoria special?

Lake Victoria in Kenya is home to the haplochromine cichlids which are a type of fish. Lake Victoria has undergone many ecological changes in the last five decades. These changes include the phytoplankton composition, the emergence of blue green algae and, most importantly, the introduction of a new type of fish called the Nile perch. The introduction of the Nile perch, which is a fish predator, is responsible for a 65% reduction cichlid populations. The loss of cichlid populations has likely accelerated the increase in blue green algae, which leads to a loss of water transparency and hypoxia (the decrease of oxygen in an environment when the algae blooms decompose). The lack of oxygen in the water negatively impacts the fish that are subjected to death by asphyxiation or predation by Nile perch if they move to the oxygen rich shallow waters. If all these factors were working against the cichlids then how did they make their comeback?

A cichlid fish.

The great cichlid comeback

Between 1980 and 1990, there was a decline in Nile perch because of overfishing causing a 21% increase in cichlid populations, but they had returned to an altered environment; it is this return to the altered environment that can be used to understand the response, resilience and diversity of cichlids. The new generation of cichlids looked different; they had larger retinas that allowed them to see through algae blooms, therefore making them better able to catch incoming prey, spot predators, and find mates. They developed larger gills as a response to the previous hypoxic environment. Lastly, due to the decline in water clarity, there was a change in their diet. They began feeding on larger prey like shrimp and mollusks. The cichlids also emerged in a new papyrus dominated habitat and rocky areas where they had access to more oxygen and found refuge from the Nile Perch. The resilience of the new generations of cichlids is an example of genetic and ecosystem diversity in Lake Victoria. So how exactly can we ensure the resilience of ecosystems? Is there a way to manage ecosystem resilience?

This image is meant to describe the cichlid comeback. mage courtesy of SImplecoin Business.

 

Ecosystem resilience management

Ecosystems don’t function on a straight forward loop of disturbance then rebuilding, there are unpredictable twists and turns, so it’s not reliable to assume that any old management technique will do the job. Alex Awiti states that the goal of ecosystem management is to manage the interactions of the species that make up the functioning biodiversity of the particular area. Functioning diversity can be defined as the elements of biodiversity that help the ecosystem become better functioning. One of the prevalent resilience-based ecosystem models that were used for Lake Victoria was the idea of a back loop; it’s a release and renewal cycle that focuses on transformation and feedback of an ecosystem. Because this back loop cycle is meant to nurture renewal, it calls for people to adopt new methods that will ensure the renewal and repopulation of the habitat or species in danger.

Lessons learned and future directions

We can determine that the resilience of the cichlids was dependent on genetic, functional, and response diversity (the unique way in which the species in an ecosystem respond to external stimuli) and even ecosystem diversity. There are many factors that play a role in the maintenance of species diversity and resilience of certain habitats for the upcoming generations. Managing for resilience is critical for coping with uncertainty and surprise in a biosphere shaped by human action. From Lake Victoria, we can learn that when an ecosystem has better genetic diversity, then the chances of them evolving from their previous generations’ increases and therefore ensures that populations will adapt and grow; species resilience can increase biodiversity in the ecosystem. Awiti’s work is important because it shows us that the lessons we need to learn on how to treat nature exist in our own backyards. The smallest change we make can be the first step towards hitting a pause button on issues like climate change (global warming) and pollution.

Source article:

Awiti, A. O. 2011. Biological diversity and resilience: lessons from the recovery of cichlid species in Lake Victoria. Ecology and Society 16(1): 9. [online] URL: http://www.ecologyandsociety.org/vol16/iss1/art9/

Additional references:

Folke C, Carpenter SR, Elmqvist T, et al. 2002. Resilience and sustainable development: building adaptive capacity in a world of transformations. Ambio 31: 437–40.

Guide, C. (2018). Lake Victoria Cichlids Guide – Cichlid Guide. [online] Cichlid Guide. Available at: https://cichlidguide.com/lake-victoria-cichlids-guide/

Holling CS. 1996. Engineering resilience versus ecological resilience. In: Schulze PC (Ed). Engineering within ecological constraints. Washington DC: National Academy Press.

Sue, C. (2015). Impact of an Invasive Species. [online] National Geographic Society. Available at: https://www.nationalgeographic.org/media/impact-invasive-species/

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Lindsay Green-Gavrielidis

Lindsay Green-Gavrielidis

I’m a Postdoctoral Researcher at the University of Rhode Island, where my research focuses on applied seaweed research. Have you ever gone to the beach for a day of rest and relaxation only to find the sand smothered by a thick mat of multi-colored seaweed? These floating mats of seaweed are referred to as seaweed blooms and they can have negative impacts on the ecology and economy of coastal communities. My research aims to determine how these blooms are changing over time in response to global climate change and coastal management efforts. I am also interested in promoting seaweed aquaculture in local waters. Not only are seaweeds delicious, but they can be used to clean up excess nutrients in our coastal waters (referred to as bioremediation). When I’m not in the lab, I love to garden and travel.

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