I agree with Fabian

I was also working in Ethiopian rivers. The macro-invertebratediversity and assemblage significantly vary between dry and wet season. It is not only their developmental cycle that will be affected but also the flood and spate will remove riparian vegetation and substrates as a result most sensitive taxa will disappear. Moreover, the water level fluctuation in the wet season has also a great impact.

Interesting.... Regarding the young larvae is true. I found that several family would suddenly disappear on certain month, but the water quality is good as ever, might due to the life cycle, im not sure.

3/4 of my focus river located in urban area. On dry or wet months water quality can be either in class 3-5. I suspect water quality is more influenced by point source pollution (residential & industrial) than seasonal effect.

My other colleague working on this monitoring with focus on pristine river said on wet season fast water current do influence the organisms distribution and as that you just said, they move to slow current area.

But for a modified U-concrete canal is a different stuff, i need to see on this and considering taking water flow data.

Oh that malaysian wqi index system

I was hoping more data on small modified urban river... Where riparian and substrate are hard to find. And benthic macroinvertebrate survive on whatever sediment and patchy aquatic plant

I'm not working with macro-invertebrates. However, it is possible that seasonal variations would influence macro-invertebrate assemblage. During dry seasons, concentration levels of contaminants tend to be higher than during rainy seasons when dilution effects are taking place. As result, sensitive taxa may not survive. For example, a factory discharging effluent at a rate of 50 m3/s into a river with 100 m3/s during rainy season has more impact when the river flow reduces to 70 m3/s during dry season because the river's ability to assimilate the effluent is reduced.

its hard to see seasonal effect on urban river. residential area and industrial area have different rate/time when all those waste released into the river. this influence physico-chemical directly. but for benthic macroinvertebrate is a different story. some of the water quality data give a better water quality status during rainy season. but the benthic macroinvertebrate is otherwise.

is it due to fast current and increasing river height or due to past pollution event? as physical chemical analysis only valid during time of sampling.

regarding the oxygen concentration. some literature state that ripple effect from cobblers and other physical interruption would increase the dissolve oxygen and i found its true in my study as the river not all way smooth... but biological oxygen demand and chemical oxygen demand data show higher demand.

frankly speaking, I a bit confuse with this kind of river as clean/pristine river outside city which i usually work with have more persistent trend data.

here I attach some data. every month of Jun is the mid of dry season, sampling was done once every 2 month

Akmal,

The most important thing that you need to know is that some macroinvertebrates can escape pollution using the riparian vegetation and other habitat attributes. Therefore, either you should sample from the same habitat type or multihabitat sampling. So that data can be comparable among sites. Secondly, macroinvertebrates are strongly influenced by habitat quality and it is better to include habitat quality assessment.

orait... thanks for the habitat quality assessment suggestion. that would be suitable to justify some relation between seasonal effect on water quality and benthic macroorganism. I might have overlooked that possibility and too focused on chemical-physical data

Have a look at this paper: A comparison of spatially explicit landscape representation methods and their relationship to stream condition.ERIN E. PETERSON, FRAN SHELDON, ROSS DARNELL, STUART E. BUNN, BRONWYN D. HARCH. 2011. Freshwater Biology, Vol 56(3): 590-610. It considers all the co-factors that can affect urban stream condition.

Wow tq tq very much.... I shall read it now

Hi Akmal. We published something on urban/peri-urban areas in Brazil. And we also looked at some of the effects of wet/dry season (huge pressure due to precipitation and water current). I also agree with the colleagues that habitat loss is one of the main drivers of change for MIB assemblages. regards, Daniel

Article Substrate specificity, environmental degradation and disturb...

Hi Akmal. How are you?

Firstly, I need to know if you want to analyze benthic community (that lives in sediments) or all macroinvertebrates community (organisms that lives in surficial water, sediments and water column)? This point is very important.

Urban rivers usually have different hydrodynamics when compared with rivers located in outside of the urban area. Especially if these rivers are channeled, flow and water velocity (are different variables) can vary greatly with a simple rain and thus the benthic community will change according with this aquatic dinamic. See about laminar flow and turbulent flow.

The answer depends on the situation of the urban river. Urban rivers can also receive a lot of effluents from cities. In this situation other variables can affect the distribution of benthic macroinvertebrate communities.

Best regards,

Professor Corbi

Fine tq, i hope you in a great condition too,

I want to analyze benthic community that live in sediment and water column, the malaysia bmwp index exclude any community like water strider.

True, urban river vary from those situated outside the city. Much harder to understand.

Currently I try to get rainfall data, and land use data.

Thank you again Professor Corbi

Hi, Akmal,

it is also important to remember that many of the macroinvertebrates are insects that only spend part of their life cycle in the water. In the tropical parts of the Northern Territory of Australia we sample at the end of the wet season. Many insects are then present at their latest, ie largest, growth stage and easiest to identify. Two months after this many of them won't be sampled at all. Some macroinvertebrates, ie some crustaceans are migratory and again will not be caught throughout the whole year. However, when present they can be quite dominant in a sample.

This should apply to urban streams as well as semi-natural and natural ones.

Another aspect is to use a standardised protocol for each sampling event, which you might already be doing. This should state the habitat/s to sample, sampling method, sample size, ie size of area sampled, etc.

Good luck !

Gisi Lamche

Dear gisela lamche,

Such an interesting finding. I would say that i also encounter the same case. Do you have any interesting reference to share regarding the duration of the life cycle? As there are less info regarding the life cycle of each family.

Thanks again for sharing such story. That is really interesting to highlight the behaviour.

Wow that a very nice paper! Thank you. Just like i needed, the anthropogenic and seasonal on benthic macroinvertebrate