The hidden beauties living in the depths of the world’s streams


There are many streams in Canada, where I live. So of course, growing up, I spent a lot of time playing in them. I would try to catch fish, frogs, butterflies living on the surrounding plants, and sometimes even end the day running home with a leech stuck on my skin – it goes without saying, an accidental catch. (Although it’s always fun to try to detach a leech stuck on your skin. My personal favourite technique is to use a lighter –- the proximity of heat scares them away.)

A stream flowing through the Hautes-Gorges de la rivière Malbaie National Park, in Quebec, Canada. I’ve put my red hiking bag down to take a break in this peaceful spot. Photo by Dalal Hanna

Streams were one of my favourite playgrounds, which I felt I knew inside out. So a few years ago, when I started my PhD researching the various ways freshwater ecosystems contribute to human wellbeing, I was surprised to discover that there was a whole other world of life hiding at the bottom of streams I didn’t know about.  They are the living things that are small, but visible to the naked eye. They are miniature, but they produce essential food for many other species, like fish. They are tiny, but exquisite. They are benthic aquatic invertebrates!

A black fly larva, which eventually turns into a pupa, and in turn emerges from the water as a black fly. Usually anywhere from 5-15mm long. Photo by Dalal Hanna
A black fly pupa. Photo by Dalal Hanna.

These itsy bitsy little bugs live on rocks and in the soil found at the bottom of streams. There are hundreds of different species, found all around the world, each with its unique quirks.  One of my personal favourite families is Helicophsychidae, because they build circular sheaths out of tiny rocks that they hide in and use for protection.

Helicopsychidae sheath. Photo by Dalal Hanna
Can you spot the insect poking out of the sheath? Photo by Dalal Hanna

Another family I really like is the Hydropsychidae. They build themselves little homes out of plants and mineral fragments on the side of rocks. At the edge of their homes, just like caterpillars, they spin a net out of silk they produce to catch algae and other invertebrates that they then feed on. Apparently, they sometimes get separated from their homes because of the current in streams, at which point they’ll try to steal another home from one of their kin by engaging in fights. I like to imagine these insect battles.

Hydropsychidae larva. Usually anywhere from 3-40mm long. Photo by Dalal Hanna

Over the past few months, I’ve spent more than 200 hours at the macro-microscope looking at samples I collected from the bottom of streams around the province of Quebec, in Canada, identifying all the aquatic invertebrates that are found there.

Sorting through sediments collected in the bottom of streams to find the benthic macroinvertebrates amidst the muck. Photo by Dalal Hanna
Can you spot the insect on the bottom, in the centre? Photo by Dalal Hanna
Hydroptilidae. One individual in the sheath it built, and another floating freely. Usually smaller than 5mm long. Photo by Dalal Hanna

I’m comparing streams that are in National Parks to streams that aren’t protected, because, in an age where National Parks are increasingly threatened by development, we need to know about every beautiful living thing found there, and what happens to them when we stop protecting our ecosystems.

Stay tuned to find out more!

Changing Planet


Meet the Author
Since as far as I can remember I've spent my time outside attempting to understand and connect with the natural world that surrounds us. When it came time to make a career choice, this lead me toward research in ecology and conservation, topics that are of fundamental importance to me. I completed a Bachelors degree in Environmental Sciences at the University of Ottawa in 2011, during which I studied the effects anthropogenic traffic noise on birdsong; discovering the impacts human activity has on even the most unexpected aspects of animal life! I then completed a cross-Canada canoe journey in partnership with the Canadian Parks and Wilderness Society & the Ottawa Riverkeeper Alliance raising funds and awareness for watershed conservation. Between 2012 & 2014 I studied mercury contamination in African freshwater fish as part of a Masters degree in Biology at McGill University. (The stories in this blog series are from my field work in Uganda!) Following this, I spent time developing Science Faction, a podcast all about unbelievable discoveries and creating an urban beekeeping collective in Montreal, Canada, with which we teach locals about beekeeping and pollinator gardens. Today, I'm working on a PhD in the department of Natural Resource Sciences at McGill University, during which I will explore questions related to riverine ecosystem service conservation.