Tag Archives: food web

How Influential is the Platypus in Freshwater Dynamics?

Image Credit: Maria Grist, CC BY-SA 4.0, Image Cropped

Platypus predation has differential effects on aquatic invertebrates in contrasting stream and lake ecosystems (2020) McLachlan-Troup, Scientific Reports, https://doi.org/10.1038/s41598-020-69957-1

The Crux

A trophic cascade occurs when a predator’s effects of its prey goes on to affect ‘lower’ levels of that ecosystem. A great example is the effect that sea otters have on kelp: the sea otters prey extensively on sea urchins, which in turn increases the populations of kelp, which the sea urchins prey on. While this is a result of direct predation by otters, often this can occur through a prey species changing its behaviour to avoid the predators.

Yet most ecosystems are more complex than a simple three-level trophic system. Cascades are therefore more likely to occur when the ecosystem is less complex, or when there are well-defined relationships between species, as a result of a predator having preferred prey species or only a few groups of species making up an ecosystem.

This week’s authors investigated how the platypus (our recently-found-to-be-fluorescent friend) influences the abundance and species richness of invertebrates across both rivers and lakes, and whether it’s capable of affecting an ecosystems algae and sediments as well.

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Consider the Copepod: Researching the Base of the Food Web (with Dr. Nancy Mercado-Salas)

Image Credit: Andrei Savitsky (left and right), CC BY-SA 4.0 ; Uwe Kils (centre), CC BY-SA 3.0

The deep sea is a wondrous world of biodiversity, darkness, and mysteries we still know very little about. Despite the fact that we rely on the deep sea as a sink for carbon dioxide – and increasingly as a source of natural gases and minerals – we have very little understanding of how our actions will affect its intricate food web.

Near the base of the food web sits an incredibly diverse group of animals called copepods. They are so abundant and have such sweeping variety that we are still struggling to come up with a way to classify them. Dr. Nancy Mercado-Salas has worked with these tiny creatures since her bachelor’s thesis, both in freshwater and in marine ecosystems, and her message is clear: We need to increase our knowledge on this group of animals before it is too late.

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It’s EVERYWHERE: The true extent of microplastics

Image Credit: Oregon State University, CC BY-SA 2.0

Quantitative analysis of selected plastics in high-commercial-value Australian seafood by pyrolysis gas chromatography mass spectrometry (2020) Ribeiro et al., Environmental Science & Technology, https://doi.org/10.1021/acs.est.0c02337

The Crux

Plastic is one of those things that we hear about all the time these days. More specifically, we hear about how there is an absolute ton of it in the environment thanks to human negligence and the lack of concern that a large amount of people have for where their plastic goes when they are finished with it. Plastic isn’t like paper or metal, it takes a long, LONG time for it to break down. Plastic bags take anywhere from 10-20 years, but the normal time it takes for most plastic waste to decompose is about 1000 years. To put that into perspective, Leif Erikson led an expedition from Greenland to the coast of what is now North America in the year 1002. If his crew had some plastic with them and left it in the places they visited (typical tourists) there’s a good chance that it would STILL be there today.

I hope I’ve convinced you why plastic is bad, but another danger that plastics pose are microplastics, small bits of plastic that have come from a larger piece, all of which are less than 5mm in size. Our environment is full of them, and the ocean in particular has been saturated with microplastics. In 2014 a research expedition sailed from Bermuda to Iceland (a trip of 2500 miles/4023 km) and found microplastics in every single sample they took. And that was just plastic in the environmental samples they took, the real threat to marine life comes from what happens to all of that microplastic.

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How Form Defines Function

Image Credit: Francesco Veronesi, CC BY-SA 2.0, Image Cropped

Macroevolutionary convergence connects morphological form to ecological function in birds (2020) Pigot et al, Nature Ecology & Evolution, https://doi.org/10.1038/s41559-019-1070-4

The Crux

There are an astounding amount of different forms that the animals on our planet take. Likewise, there are a multitude of diverse functions that animals serve in the environment, such as that of a herbivore, a predator, or scavenger. In some cases it’s a clear link between the form of a given animal and its function in the environment, like that of the beak of a hummingbird that allows it to feed on nectar and their role as a pollinator. But whether or not there is a reliable way to predict the function of an animal based off of its form is has been the subject of considerable controversy.

Deciding on how many morphological traits to use to predict ecological function is a difficult prospect. One could argue that it’s impossible to pick a finite number of traits, as there are infinite possible niches that organisms can fill so there’s no way that a set of traits could fill those infinite possible niches. Mapping animal form to function has major implications for quantifying and and conserving biodiversity, and the authors of today’s paper wanted to to determine just how many traits are needed to do that.

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