Project Breathless

Project Breathless brings together an interdisciplinary team of ecologists, economists and communication scholars to increase understanding of the impact of low oxygen dead zones in lakes and oceans. The project team focuses on how low oxygen conditions influence fish, their habitats and the food webs that support them, as well as ecosystem services, including fisheries production.

The study focuses on several species of fish and their food webs in the Baltic Sea, Gulf of Mexico and Lake Erie.

Project Breathless is supported by a grant from the U.S. National Science Foundation (award #: 1923965).

Project Breathless examines the impacts of dead zones on aquatic food webs.

Image adapted from photo by Peter Ljungberg, SLU

Dead zones - or hypoxic zones - are areas of significantly reduced oxygen in oceans, estuaries and lakes. Pollution from runoff and warming waters due to climate change are leading to an increase in the occurrence of hypoxic zones worldwide.

Project Breathless seeks to quantify the loss of ecosystem services that are caused by dead zones. A major concern is the loss of fisheries production. Aquatic species with limited mobility like shellfish and other invertebrates often die from exposure to low-oxygen conditions. Fishes can swim away from dead zones, but the exposure to low oxygen levels can impact growth rates and body condition of some species, including those that humans depend on for food. Hypoxic exposure produces smaller fish, which can reduce overall commercial catches and lead to a lower availability of affordable seafood. Smaller fish have lower rates of reproduction, which could reduce long-term fisheries productivity. Other ecosystem services impacted by dead zones include recreational and cultural assets, and the benefits of eco-tourism on local economies.

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Project Breathless in the Baltic. Produced by Elizabeth LoGiudice with footage provided by Deep Sea Reporter.

Exploring dead zones through a fish's eyes and ears

Chemical analysis of fish eye lenses and earstones reveals impacts of low oxygen exposure.

Karin Limburg and Yvette Heimbrand analyze chemical components present in fish otoliths. Photo credit: Martina Blass

Earstones, or otoliths, are tiny, calcified structures in fishes' ears that grow in concentric rings. The age and condition of a fish can be tracked by examining earstone growth rings. As they grow, earstones absorb trace elements from the water. The presence of the element manganese in an earstone can indicate a fish's exposure to low oxygen conditions.

The presence of methlymercury in eye lenses can also be an indicator of hypoxia. Methlymercury is a neurotoxin that is made more bioavailable under low oxygen conditions, mobilizing it into aquatic food webs.

For more details about Project Breathless research, visit our Project Details page.

A Baltic cod otolith. Photo credit: Jess Lueders-Dumont

breathing new life into dead zones

We know the causes of dead zones. Urbanization, loss of natural land cover, fossil fuel use and certain agricultural practices lead to runoff of fertilizers, sewage and other pollutants into our waterways. These pollutants accumulate in lakes and coastal areas and lead to algal blooms, which cause low oxygen conditions when the algae die and decompose. Climate change is increasing water temperatures, leading to larger and more severe hypoxic events.


Produced by Caitlin Warren for The Economist.


Fortunately, many of the solutions to mitigate and adapt to climate change will also address causes of hypoxia. These include:

  • Reducing emissions from the energy, transportation and food sectors

  • Revitalizing cities to be green and sustainable

  • Conserving natural landscapes

  • Using nature-based solutions for storm water management

  • Using flood-proof wastewater infrastructure

  • Reducing agricultural runoff

Baltic cod. Photo credit: Yvette Heimbrand