Author Archives: Gabriela Rosu

A Model for Predicting Population Abundance of Species

Vancouver Island as seen from North Shore Mountain. The phytoplankton used in the experiment were sampled from Vancouver Island. (Source: Morgan Strohan)

As the environment changes with time and climate, the ability for a species to survive is dependent on the resources available to support body functions. The process by which nutrients from the environment are converted into the energy needed to support an organism is called metabolism. As temperatures increase, the metabolic rate of species increases; this means that resources in the environment are used up faster to produce energy. While previous studies looked at the effects of temperature on a species’ population growth rate, Dr. Joey Bernhardt and her colleagues decided to look at how temperature affects a species’ population carrying capacity, and how the metabolic theory of ecology (MTE) can explain these effects.

Background of the experiment

Phytoplankton were sampled in areas around Vancouver Island, from the Pacific Ocean.

Several populations of phytoplankton were kept under a fixed supply of resources between 5-38°C for forty-three days. As the phytoplankton’s ideal temperature is 25°C, the researchers measured their oxygen production between 8-24°C so as to see the rates of photosynthesis and respiration (their metabolic functions). It was found that carrying capacity declined with increasing temperature.

Phytoplankton is a simple organism relative to multicellular organisms so it provides a good model within the lab. (Source: Dr. Joey Bernhardt)

The stability of the environment

Carrying capacity describes the maximum size of a species population in a certain environment as a function of time, which is related to the amount of resources available. As resources are limited, the environment can only support a certain number of organisms. Carrying capacity is reached over time as resources are used up and the population growth rate naturally reaches zero.

[The phytoplankton] grow from almost no cells, through an exponential phase, and then eventually they plateau out; upon plateauing, they’ve reached carrying capacity. (Source: Wikimedia Commons)

Of course, an environment is not stable forever – natural disasters occur, other species evolve and dominate, etc. – thus the carrying capacity of a species population is subject to change. The metabolic theory of ecology can be used to explain the phenomenon of population decline with increasing temperatures.

Listen to the podcast below to hear why!


Why does this all matter?

Given all this information on theories and phytoplankton, what does this really mean as a big picture and why is it important? We know that along with climate change comes warming waters in our oceans. As stated above, warming temperatures have obvious effects on populations, specifically phytoplankton in this case. But just because phytoplankton may seem boring and meaningless to most people doesn’t mean these results don’t have a much bigger meaning to all other species on Earth!

Watch the video below to find out just what phytoplankton have in common with every other species on this planet, and what warming temperatures could really mean…

As we can see, the factors of temperature, metabolism and the surrounding environment all have significant effects on a population. Climate change is currently happening and we are already starting to see the effects on ecosystems around the world, both in oceans and on land. We are not able to predict all outcomes – as there are many unknowns associated with climate change – but Dr. Joey Bernhardt said it best: “One thing we can say for sure is that warming temperatures will undoubtedly accelerate metabolic rate, and this will have predictable effects on abundance.”

By Gabi Rosu, Morgan Strohan, Dan Choi, and Olivia Wong

Using the Power of Sunlight to Fight Infections

Imagine if the most resistant pathogens that plague our society today could be destroyed using the power of sunlight. Terrifying resistant bugs seem to become ever more common, and ever more dangerous. Taking a round of antibiotics can be a gamble, as there is no guarantee the bacteria will be killed off by the drugs. Antibiotics are starting to fail, but what if there is another solution after all options have been exhausted?

The overuse of antibiotics (Source: EarthPulseDaily on Flickr)

As early as 1845, it was known that sunlight could be used to treat bacterial infections. Ultraviolet (UV) light was also found to have incredible effects upon affected skin, destroying the genetic material of harmful microbes circulating in the blood underneath its surface. Nonetheless, researchers decided to take it one step further: Why not expose the blood to the UV light directly?

That’s exactly what researcher Emmett K. Knott and his co-workers did to blood extracted from infected dogs, using a machine that passed the blood under a UV light. Remarkably, the dogs made a full, long-term recovery without any side effects. Similarly, in 1928, a woman who was on the brink of death due to septic abortion complicated by a Streptococcus infection was treated with UV blood irradiation (UVBI) and recovered completely, even having two healthy pregnancies some time afterwards.

Old and new: UVBI machines (Sources: PubMed Central and Champion Ultimate UV)

You might be thinking that exposing your blood to UV rays sounds extremely dangerous! However, our body cells contain repair enzymes that can quickly fix any damage done to them by the low dose of UV light.

UVBI was an outstanding method for treating infections during the 1940s and 1950s, but was sadly overshadowed by the emergence of antibiotics. Too much of a good thing quickly turns sours, and this has certainly become the case with modern antibiotic use. Doctors are prescribing antibiotics when they are not needed – such as for viral infections – and also prescribing them too frequently when they should really be a last resort. UVBI seems to be making a small comeback, but few recent studies have been done, as some medical practitioners refuse to accept it as a viable treatment for infection despite its decades-long history. This is an effective, low cost treatment with no side effects that is still being used in some technologically-advanced countries. Hopefully, UVBI will be widely used again, starting with patients who have failed their antibiotic treatments.

Here is a TED-Ed video with more information on how bacteria can become resistant to antibiotics:

By Gabriela Rosu