Author Archives: Cam Carvalho

Marine Evictions

Anyone who has seen the any of our world’s oceans can easily appreciate their immensity.

 

The ocean’s cover 71% of the surface of Earth. Retrieved March 4, 2019 from https://www.goodfreephotos.com/people/woman-standing-next-to-the-ocean.jpg.php

But don’t be fooled. Contrary to what you might think, they aren’t open expanses of habitable environment where any marine species can live and thrive.

As anyone with any background in biology can tell you, just because the space is there, doesn’t mean it can be occupied by any living organism. This is especially true when it comes to the marine environment.

Marine species have to face a number of challenges that many terrestrial species simply would never have to worry about. One of these challenges, that poses a more serious threat because of climate change, is the availability of oxygen.

The Oxygen Minimum Zone

Many complex physical, biological, and chemical processes are constantly taking place within the ocean. Some of which are highly variable, and others are relatively constant.

One feature that arises from a combination of these processes, is the Oxygen Minimum Zone (or OMZ), which are pockets within the water column that contain low levels of dissolved oxygen. These areas are present throughout the world’s oceans and usually occur at a depth of 200 to 1000 metres.

Oxygen Minimum Zones occur naturally and don’t pose a serious threat to marine life. However, researchers have begun to see that some of these low oxygen areas are beginning to expand, as a result of global warming.

Sea surface oxygen levels. Purple are the lowest concentrations and red are the highest. Retrieved March 4, 2019 from https://commons.wikimedia.org/wiki/File:WOA09_sea-surf_O2_AYool.png

The Problem

One benefit of living in the ocean that many terrestrial animals don’t have, is the ability to not only migrate horizontally, but also vertically. In fact, many marine organisms undergo these vertical migrations for many different purposes, such as escaping predation.

There are many studies being conducted, and that have already been done, where researchers are trying to measure how well different marine species are able to tolerate low levels of oxygen.

They can measure this through physiological responses, like metabolism, or behavioural responses, like the frequency and duration of movement within the water column.

One key observation that some researchers have made is that many fish species cannot tolerate low levels of oxygen. So, if the oxygen minimum zones continue to expand, their habitat will become more and more limited.

What Does This All Mean?

Some species with a higher tolerance to low oxygen levels may have an advantage as they are able to escape predation and other competing species.

However, the expansion of the oxygen minimum zones will bring even more challenges to species who need to avoid the low oxygen levels.

This is especially concerning if this includes certain fish species that are an integral part of the food web; not only as a source of food for many other marine organisms, but for the fisheries industry that depends on a large expanse of fish populations.

 

Cameron Carvalho 

 

 

 

 

 

A Strangled Ocean

When looking through the Science section of any prominent magazine or newspaper, it’s rare not to see an article involving climate change and its numerous impacts on our planet. It’s a topic that is constantly being discussed and rightly so, as it represents one of the biggest challenges that society is facing. Even if you have no idea of the science behind how our world is being affected, articles such as this one just recently posted in The New York Times online website, are good to get you thinking.

A visual depiction of how much global warming heat is going into the various components of the climate system for the period 1993 to 2003. (n.d.). Retrieved January 14, 2019, from https://skepticalscience.com/graphics.php?g=12

Our world’s oceans are the most dramatically impacted by global warming, and are the subject of countless research studies being done. One of the most concerning effects of climate change on the oceans, and perhaps the one raising the most questions, is the process of deoxygenation. This, in brief, is the process of declining O2 levels because of many complicated and interconnected biological, chemical, and physical processes. Perhaps the most fundamental and easily understood process that effects the way oxygen is exchanged between the atmosphere and surface ocean is the correlation between temperature and solubility; as temperature increases the solubility of oxygen decreases. This temperature effect accounts for up to half of the deoxygenation in the upper 1000m of the water column.

Being able to accurately model the changes in oxygen concentration is the biggest hurdle associated with deoxygenation. When modelling any part of the ocean, a researcher needs to understand and accurately represent the processes that are occurring. Seeing as oxygen is highly utilized and highly dynamic within any given part of the ocean, it’s extremely difficult to produce meaningful results. So, in most studies, especially those involving biological oceanography, a field where many processes are poorly understood, researchers must make certain assumptions. Additionally, these assumptions are highly dependent on that researchers understanding of the ocean.

The urgency of being able to obtain meaningful and reproducible models is always increasing. Declining oxygen levels in the ocean can dramatically affect the countless species that live in and depend on the ocean for resources.

Most notably, us.

An Argo float, foreground. The new study included direct measurements of ocean temperatures from the global array of 3,500 Argo floats and other ocean sensors. (2015, July 9). Retrieved January 14, 2019, from https://www.jpl.nasa.gov/news/news.php?feature=4655

The process of deoxygenation does not need to be looked at as a doomsday clock.

We have countless research behind us and every day, researchers work towards finding a solution that minimizes the effects that global warming has on the world’s oceans.

 

Cameron Carvalho