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The Effect of dams on invertebrate abundance and functional feeding group composition

Gruber, Hampus (2021) BIOK01 20211
Degree Projects in Biology
Popular Abstract
How dams affect invertebrates

Getting your electricity from naturally produced energy sounds good, but this has its consequences too. To produce electricity from water, dams must be constructed, and these form a barrier between upstream and downstream areas. This stops our migrating species such as salmons, trout's, and eels and a decline in these economically valuable fish. Not only do salmons and trout have an economical value, but for freshwater pearl mussels, these are important as a host for their larvae which live on the fish's gills. Mussels might not seem valuable but for the rivers, they act as cleaners and bind nutrients which would cause eutrophication in the rivers.

Not only do dams impact mussels, but also other... (More)
How dams affect invertebrates

Getting your electricity from naturally produced energy sounds good, but this has its consequences too. To produce electricity from water, dams must be constructed, and these form a barrier between upstream and downstream areas. This stops our migrating species such as salmons, trout's, and eels and a decline in these economically valuable fish. Not only do salmons and trout have an economical value, but for freshwater pearl mussels, these are important as a host for their larvae which live on the fish's gills. Mussels might not seem valuable but for the rivers, they act as cleaners and bind nutrients which would cause eutrophication in the rivers.

Not only do dams impact mussels, but also other invertebrates. Downstream of the dams, filterers dominate the area since they can filterer out the small particles that are washed out of the dams. Shredding invertebrates are seen to be much lower in these areas since the bigger particles that they shred, stay in the dams.

But by tearing down these dams, wouldn’t the invertebrate community be in danger when the predators are being re-introduced? Studies suggest that the salmonids have an opposite effect on invertebrates and bring food from the ocean to them. The food is the very nutritious eggs that the salmonids lay in the stream, and this means a feast for the lucky inhabitants of the downstream areas. To study this, a method called kick-sampling was used to investigate the number of invertebrates. This method is, like the name says, a sampling method where the substrate in the river is kicked up and the invertebrates are taken into a net by the flow. These are later counted, measured to estimate weight, and placed into functional feeding groups. Functional feeding groups represent the species role in the ecosystem and are a simple way to get a grip of the composition.

Even though the downstream areas showed a higher amount in individuals, total biomass, and biomass for the functional feeding groups, the difference could not be proven statistically. It seems like these dams do not impact invertebrates as hard as other species and could maybe be explained by that the most invertebrates found in the river also have a terrestrial form after hatching. In the adult stages, they can later choose if to lay their eggs upstream or downstream and are not constricted to one area.

This area of study is still quite unexplored and needs further studies to get a grip on the invertebrates. To get a more precise result I would propose to extend the time for sampling to see if these small differences in composition and the total amount can be proven. Overall, the effects of removing dams seem to only have positive effects on the invertebrates, since the ones that are lucky to live downstream thrive!

Supervisor: Anders Persson
Bachelor thesis 15hp in biology 2021
Department of biology, Lund university (Less)
Please use this url to cite or link to this publication:
author
Gruber, Hampus
supervisor
organization
course
BIOK01 20211
year
type
M2 - Bachelor Degree
subject
language
English
id
9059903
date added to LUP
2021-06-30 10:17:17
date last changed
2021-06-30 10:17:17
@misc{9059903,
  author       = {{Gruber, Hampus}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{The Effect of dams on invertebrate abundance and functional feeding group composition}},
  year         = {{2021}},
}