Write article critique and summary

Dr. Moring

BIO 3934

11-16-21

Selected Reading #3

Summary

This article details the experiment, research, data, and methods used to find the effects of

different dissolved oxygen levels on survivability, emergence, and drift of macroinvertebrates. Aquatic

macroinvertebrates have different structural and behavioral respiratory systems. Some insects require

diffusion through the cuticle, which is the outside layer of the insect’s exoskeleton where the muscles are

attached, and others use a plastron or an air bubble that they use as a gill. This gives the impression that

different species and genus of insects will not be affected the same way as other species or genera. The

experiment was conducted using different compositions of upland and lowland assemblages due to the

adaptations of different locations.

Artificial mesocosms were created using a combination of washed and unwashed cobble (rocks

10-12cm in diameter), a motor to drive water flow, and an oval container with two walls to create a

circular track. Each mesocosm was seeded with a random container of macroinvertebrate to ensure

similar numbers within each mesocosm. The variable that was manipulated was oxygen saturation.

According to the charts given, for experiment, as the oxygen saturation was decreased, then the density

per 20 cobbles had risen for the benthic zone. For experiment 2, as oxygen saturation decreased, the same

is true as well as the number of emergent macroinvertebrates decreased tremendously. However, for the

experiments, the were not any taxa of macroinvertebrates that were tolerate enough for an oxygen

saturation level of greater than or equal to 10%. The end of the experiment led the researchers to come to

the conclusion that benthic macroinvertebrates were decreased to a delayed pupation more than any lethal

impact that a low oxygen saturation could have. This increase in benthic organisms also led to a decrease

in emergent organisms. It is possible for the organisms to have nestled into the artificial riffle to help

compensate for the lack of oxygen saturation. The conclusion being that lowland macroinvertebrates were

more resistant to hypoxia was found to be not proven correct.

Critiques

My first critique would be that there would be no use of leaf litter within the artificial mesocosm.

The article says they use it for nutrients and for organic material. I think they would have been okay in

either not using it or finding an alternative for the material. I believe that they could get away with not

using it but just using completely unwashed but filtered sand, cobble, and gravel to fill in the tubs for the

experiment. Although, this would add another degree of variability for the experiment. The nutrients

could be added though dissolvable matter and alternative means.

My next critique would be gathering and creating the assemblage at completely different

locations and try to find them at different elevations. They state within the article that the similarities in

the assemblages were reflecting the similarities in the gathering sites in reference to shade and relatively

small difference in elevation. This would not only give a greater variation in the species and genus of

study, but it would also give a greater chance at differentiating tolerances of oxygen saturation. Having

this difference would be great for showing how different areas and different elevations have a great affect

on how the concentration of oxygen affects the taxa in that area.

My last critique would be the graphs and charts. In comparison to other selected readings this

article has the best charts and graphs and the best explanations. However, there can still be some

improvement. Table 1 doesn’t have a standard time duration. There are labels for some, meaning there are

number that have minutes or days attached, but most number are just numbers. I don’t know the duration

that the numbers indicate so any labeling would help identifying that. Also, with identifying that same

problem it has six taxa with no data, just the statement “Until ceased moving” which is not a great way to

articulate data. I still need to know how long it took for the experiment. Figure 3 is very cluttered and that

is unfortunate because that us all because of the data points. It is still readable, but it is very clustered. I

think if they just stuck to the bar graphs, I feel like everything would’ve been a lot clearer and easier to

read.

Citation

Connolly, N.M., M. R. Crossland, and R. G. Pearson. 2021. Effects of low dissolved oxygen on survival,

emergence, and drift of tropical stream macroinvertebrates. Journal of the North American Benthological

Society, Vol. 23, No. 2, pp. 251-270.