Development of a Risk Characterization Tool for Harmful Cyanobacteria Blooms on the Ohio River

Round 1

Reviewer 1 Report

Nietch et al attempted the ecological model to predict the occurrence of cyanobacterial blooms on the River Ohio, USA. The reviewer has the following major questions.

1. What is the definition of the occurrence or presence of cyanobacterial blooms in the river? Or how did authors determine if there occurred the cyanobacterial blooms in the river with flowing water?
2. The authors’ model was mainly based on the data in the River Ohio in the past 25 years. However, as far as the reviewer knows, the occurrence of algal blooms has been rarely reported in the River Ohio, most of the researchers focused on the western Lake Erie in which massive algal bloom occurred annually. The occurrence frequency and bloom intensity in River Ohio should be not as remarkable as that in Lake Erie. If the cyanobacterial bloom occurred quite infrequently, how reliable for using such limited occurrence data in the past 25-years to predict the future occurrence? This should be clearly addressed in the manuscript.
3. Additionally, is the model applicable to all the locations in the River Ohio? Every location has its relatively unique geographical, hydrological, and ecological backgrounds and the different water qualities. It should be more difficult to predict the occurrence of algal blooms in the river than in the static lake. The performance or merit (or drawback) should be clearly mentioned in the manuscript.
4. Third, it is about predictor variables used in the model. There was the lack of clear definition of each used variable. Therefore, it is suggested that the authors list all the used predictor variables in a table and that the authors also include the corresponding equation or definition.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

omments on “Development of a Risk Characterization Tool for Harmful Cyanobacteria Blooms on the Ohio River” by Christopher T. Nietch et al.

I read the manuscript with great interest, and I found it a good fit to publish in Water. The conceptualization of ideas and the formulation of models (occurrence and persistence) are good ways/tools to predict cyanobacterial blooms in lotic systems. This is true for predicting the occurrence and persistence of this phenomenon. All in all, I find nothing significant to suggest revision except for some minor points mentioned below.

1. The replication of events: this manuscript is based on one major occurrence of cyanobacterial bloom in 2015 and the data collected from 25 sites all long Ohio River over a prolonged period of time. It would have been nice to get more data or observations on similar occurrences of similar sorts from this river or any other rives in the area. This does not mean that I recommend to have more instances of cyanobacterial blooms which is not good for the ecosystem and the life around, but to have more reliability on the proposed prediction models. It may be good to look for similar observations from elsewhere where this model can be applied and tested.
2. It would be nice to have some idea about the data on nutrient load in the water systems just before, during and after the cyanobacterial blooms. The data on the toxins produced by the bloom is given, but nothing on the nutrients. The manuscript just says the concentration of nutrients were high (?) leading to the bloom.
3. Also some information on the possible point and non-point sources of nutrients into this ecosystem will be good.
4. The length of the manuscript is a bit worrisome.. this needs to be shortened where possible.

A  good manuscript. Needs to reduce the lengt

Author Response

Please see the attachment

Author Response File: Author Response.docx